EFFECTS OF A GROUP-BASED STEP AEROBICS TRAINING ON SLEEP QUALITY AND MELATONIN LEVELS IN SLEEP-IMPAIRED POSTMENOPAUSAL WOMEN ZONG-YAN CAI,1 KENNY WEN-CHYUAN CHEN,2
AND
HUEI-JHEN WEN3
1
Division of Physical and Health Education, Center for General Education, National Sun Yat-sen University, Kaohsiung City, Taiwan; 2Office of Physical Education, Graduate Institute of Health Care, Chang Gung University of Science and Technology, Taoyuan, County, Taiwan; and 3Center of Physical Education, Tzu-Chi University, Hualien County, Taiwan ABSTRACT
Cai, Z-Y, Wen-Chyuan Chen, K, and Wen, H-J. Effects of a group-based step aerobics training on sleep quality and melatonin levels in sleep-impaired postmenopausal women. J Strength Cond Res 28(9): 2597–2603, 2014—The purpose of this study was to investigate the effect of regular moderateto high-intensity step aerobics training on the melatonin levels and sleep quality of sleep-impaired postmenopausal women (PMW). PMW with poor sleep (having a score over 5 in the Chinese version of the Pittsburgh sleep quality index [PSQI]) were divided into a training group (TG, n = 10) and an age-, height-, weight-, and PSQI score-matched control group (CG, n = 9). The participants in the TG performed 40–45 minutes of step aerobics exercise 3 times per week for 10 weeks at an intensity of 75–85% of the heart rate reserve, whereas the participants in the CG maintained their regular lifestyle. The fasting blood was analyzed, and the PSQI questionnaire and aerobic fitness test were administered before and after the 10week program. The results revealed that for the participants in the TG, the PSQI score significantly decreased (TG from 9.40 6 0.81 to 7.40 6 0.43; CG from 7.56 6 0.34 to 7.78 6 0.68; between-group difference = 2.22, p # 0.05) and the melatonin levels significantly increased (TG from 12.08 6 4.20 to 44.42 6 7.03 pg$ml21; CG from 11.81 6 2.03 to 5.5 6 1.39 pg$ml21, between-group difference = 38.65, p # 0.05). In conclusion, a 10-week moderate- to high-intensity step aerobics training program can improve sleep quality and increase the melatonin levels in sleep-impaired PMW. Therefore, regular moderate- to high-intensity step aerobics training is recommended for sleep-impaired PMW.
KEY WORDS Pittsburgh sleep quality index score, exercise, moderate- to high-intensity, heart rate reserve Address correspondence to Huei-Jhen Wen, [email protected]. 28(9)/2597–2603 Journal of Strength and Conditioning Research Ó 2014 National Strength and Conditioning Association
INTRODUCTION
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enopause, the permanent cessation of menstruation and fertility (33), is a normal part of the female aging process and is accompanied by prominent hormonal changes; unpleasant physical conditions, such as sleep disturbances, may also occur (22). Studies have indicated that sleep complaints increase with age (23), and that disturbed sleep is extremely frequent among postmenopausal women (PMW) (17,23). In Taiwan, a survey study indicated that almost half of PMW reported feeling dissatisfied with their sleep (7), and sleep problems or poor sleep qualities were more likely to be reported in PMW than in premenopausal women. Therefore, strategies that alleviate sleep-related problems are vital because sleep-related problems may have a major effect on the quality of life (18). Regular exercise has widely been considered to be a nonpharmacological therapeutic strategy against sleep disturbances (39). Research has indicated that regular exercise has positive effects on sleep quality (27,37). However, studies investigating the effects of exercise on sleep problems in PMW are limited (10,15,16,35). Of these studies, 2 correlated studies reported that training at higher intensity results in less sleep disturbances (16,35). An experimental study reported that a 4-month moderate-intensity walking program and a low-intensity yoga program failed to yield improvements in sleep quality (10). By contrast, another study by King et al. (15) reported a substantial improvement in subjective sleep quality after 16 weeks of moderate-intensity exercise training, implying that an exercise intervention at a higher intensity may be required to induce such improvements. However, not all the participants in King’s study were poor sleepers, as estimated by their Pittsburgh sleep quality index (PSQI) score (5). Recent evidence has linked sleep and melatonin levels (19,40). The production of melatonin, which is secreted by the pineal gland, is inhibited by light and enhanced by darkness, constituting the circadian rhythm (11). A nocturnal rise in the melatonin level makes individuals fall asleep, a process that occurs with the obvious physiological events of lowered VOLUME 28 | NUMBER 9 | SEPTEMBER 2014 |
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Sleep Quality and Melatonin Levels Adapt to Training body temperature, heart rate (HR), blood pressure, and sympathetic tone (9). The production of melatonin decreases as a person ages; this decrease may be the reason that older people often experience more sleep problems than do young people (19,40). In addition to its role in regulating sleep and circadian rhythms, melatonin also boosts antioxidant activity and the immune system (2,6,20). Maintaining adequate levels of melatonin is believed to benefit human health (28). Not all studies investigating the effects of acute exercise on the melatonin levels in humans have reached the same conclusion. However, most have revealed an increase in melatonin levels shortly and transiently after daytime exercise (7,29,34), and conversely, a decrease in the melatonin levels after exercise in the late evening (in the rising phase of melatonin secretion) (1,21,22). Nevertheless, few studies have investigated chronic training effects. A cross-sectional study indicated that there were no differences in the melatonin levels between recreational runners and their controls (29), but another study reported that the daytime melatonin levels of girls who played sports were substantially higher than the melatonin level of the controls (9). Moreover, an experimental study indicated an adaptive increase in the levels of plasma melatonin in professional road cyclists after a 4-day road-cycling competition (31). However, whether the melatonin level would increase after chronic training has not been established in sleep-impaired PMW. Previous studies examining the effect of exercise on the sleep quality or melatonin level have not considered groupbased exercise. Research has indicated that when social interaction is involved in the exercise atmosphere, such as in a group-based exercise program, participation of individuals can be sustained (4). From the perspective of exercise adherence, it is crucial to design an exercise intervention that is suitable for an aging population and sustainable in the long term. Step aerobics can be a form of group-based exercise and is characterized by rhythmical movements on a step, performed to cadenced musical arrangements. This exercise is easy to learn, its intensity can be adapted easily (by choosing the step height, music tempo, and similar factors), and does not require special equipment, which may meet the needs of an aging population. Previous studies have revealed that adherence was greater when individuals participated in group-based step aerobics training than when they participated in an individual cycle ergometer training (14). In addition, recent studies have indicated that group-based step aerobics training is an effective strategy for promoting improvements in the functional fitness and cardiovascular condition of apparently healthy older women (13,32). Taken together, step aerobics may be recommended as a suitable exercise modality for PMW. Therefore, the purpose of this study was to investigate the effects of regular group-based moderate- to high-intensity step aerobics training on the sleep quality and melatonin levels of sleep-impaired PMW. The hypothesis of the current study was that for PMW with a sleep disturbance, the melatonin
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levels would increase, and the sleep quality would improve after a regular group-based moderate- to high-intensity step aerobics training program.
METHODS Experimental Approach to the Problem
To investigate regular moderate- to high-intensity groupbased step aerobics training in sleep-impaired PMW, inclusion criteria for participants had to be created, and exercise intensity that met the appropriate range had to be confirmed. Initially, 44 female volunteers with a sedentary lifestyle, who self-reported the absence of menstrual cycles for more than 12 consecutive months, as well as sleep disturbances, were registered for the current study. The Institutional Review Board of the National Dung-Hwa University Institute approved all methods and procedures, and all participants provided written informed consent. Subsequently, the 44 PMW underwent a pretest, which included a fasting blood sample, anthropometric measurements, the Chineseversion PSQI, and an aerobic fitness test 2 days before the exercise training. Twenty-five participants were excluded because they were not poor sleepers (4) (PSQI #5), or they had taken sleeping pills, caffeinated beverages, or antioxidant supplements for at least 2 months before the study. Finally, 19 PMW with a sleep disturbance were selected for the study, and these PMW were divided into a training group (TG, n = 10) and an age-, height-, weight-, and PSQI score-matched control group (CG, n = 9). Given that Serrano et al. (31) indicated that a high-intensity exercise intervention may be required to improve sleep quality, the training protocol for the TG participants included 40–45 minutes of group-based step aerobics exercise training at 75–85% of the heart rate reserve (HRR) 3 times per week for 10 weeks, which met the moderate- to high-intensity exercise classification prescribed by the American College of Sports Medicine (12), whereas participants in the CG did not change their regular lifestyle. A posttest was conducted for the participants in the TG and CG 2 days after the 10-week exercise training. To minimize diurnal variance, all pretest and posttest measurements were obtained at the same time in the morning. The fasting blood samples, anthropometric measurements, PSQI score, and aerobic fitness tests were conducted pretraining and posttraining to document and compare any significant changes between the TG and CG. Subjects
Initially, 44 self-reported postmenopausal sedentary women ages 54 to 65 years old were recruited through radio and newspaper advertisements. The participants had no history of respiratory or cardiac diseases, were nonsmokers, and were not heavy alcohol or coffee drinkers. In addition, the participants had not used hormone replacement therapy in the previous year. After informing participants of the purpose, testing, training procedures, and potential risks of
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Journal of Strength and Conditioning Research the study, all of them signed an informed consent form. The study was approved by the Ethics Committee of the National Dong-Hwa University, the local equivalent of an Institutional Review Board. As previously mentioned, 25 participants were excluded. The follice-stimulating hormone (FSH) values of the remaining 19 participants, including 10 participants for the TG and 9 participants for the CG (Table 1), exceeded 40 mIU$ml21 (ranging from 47.6 to 150.2 mIU$ml21), thus meeting the inclusion criteria for menopause (26). In the present study, 1 participant from the CG withdrew from the tests for predicting V_ O2max after the training period because of an ankle sprain. Finally, only 10 participants from the TG and 8 participants from the CG were considered for predicting the V_ O2max. Procedures
The study lasted from late autumn to winter. On the assessments days, the fasting blood samples of the participants were drawn, followed by anthropometric measurements. Subsequently, the participants ate a standard meal (a sandwich, a cup of soy milk, and water) while completing a PSQI questionnaire. The aerobic fitness tests were conducted approximately 1 hour after the standard breakfast. In addition, the participants were instructed to avoid vigorous exercise or physical activity for 24 hours before the assessment days. Blood Sample Collection and Analysis
To minimize diurnal variance, all fasting blood samples were obtained in the morning between 7:30 and 9:30 AM. The blood samples were taken from an antecubital vein, using a needle and vacutainer, both before and after the step aerobics training program. Blood samples were stored at 48 C and centrifuged at 1500 rpm for 30 minutes, within 2 hours of sampling. Subsequently, the serum samples were stored at 2808 C for further serum marker assays. The serum samples were sent to the Union Clinical Laboratory, Taipei, Taiwan, for analysis. All the assays were performed according to the instructions of the manufacturers.
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The melatonin levels were analyzed using an enzyme-linked immunosorbent assay kit (IBL, Hamburg, Germany). The sensitivity and the interassay and intra-assay coefficients of variance were 1.6 pg$ml21, 3.0–11.4%, and 4–19.3%, respectively. The FSH assays were all performed using a commercial 2-site sandwich immunoassay automated chemiluminescence system (Advia Centaur; Siemens Healthcare Diagnostics, Inc., Tarrytown, NY, USA). The sensitivity and interassay and intra-assay CV were 0.3 mIU$ml21, 2.9 and 2.7%, respectively. All serum samples were analyzed in duplicate. To minimize the effects of interassay variation, all samples from 1 participant were analyzed in the same assay. Sleep Quality Measurements
Sleep quality was evaluated using the Chinese version of the PSQI, before and after the step aerobics training program. The PSQI is a self-rated questionnaire that has been validated as an instrument to assess sleep quality and disturbances over a 1-month interval. The test-retest reliability of the PSQI is 0.87 (5). The PSQI contains 7 evaluative components: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbance, sleeping medication, and daytime dysfunction. Each component is scored from 0 to 3. The sum of the 7 components is calculated as the global PSQI score (with potential scores ranging from 0 to 21). A higher global PSQI score indicates poorer sleep quality, with a score .5 having a diagnostic sensitivity of 89.6% and specificity of 86.5% to differentiate effective and poor sleepers (5). The content validity and internal consistency of the PSQI were rechecked by Yao et al. (38), who determined a Cronbach’s a of 0.85. V_ O2max Prediction
The V_ O2max was predicted using the 2-km Walk Test (Urho Kaleva Kekkonen Institute, Tampere, Finland) because of its ease, acceptability, and safety for older people (25). This test has also been shown to be a feasible and accurate method for predicting V_ O2max in healthy 20- to 65-year-old participants and was not substantially different from measured V_ O2max (24,25). All participants performed TABLE 1. Characteristic of the subjects at baseline. the 2-km Walk Test before and after the step aerobics training TG (n = 10) CG (n = 9) p period. The test was performed Age (y) 57.60 6 0.69 59.33 6 1.13 0.142 by walking 2 km on a flat Height (m) 154.45 6 3.52 154.08 6 4.82 0.128 surface indoors in a gymnasium Weight (kg) 54.15 6 1.62 57.83 6 1.95 0.761 to limit the effect of varying 22 BMI (kg$m ) 22.70 6 0.62 24.45 6 1.05 0.362 climatic conditions. The ground Age of first period (y) 12.90 6 0.48 14.00 6 0.55 0.181 was regularly marked throughMenopause age (y) 49.30 6 0.96 48.11 6 2.55 0.562 out the walking distance. Before Data are expressed as the mean 6 SE. Between-group differences were calculated by the test, the exercise leaders led Mann-Whitney U-test. the standard warm-up, which TG = training group; CG = control group; BMI = body mass index. included knee-up activity and lower-limb stretching for 5 VOLUME 28 | NUMBER 9 | SEPTEMBER 2014 |
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Sleep Quality and Melatonin Levels Adapt to Training minutes. After the warm-up, the participants were instructed to wear a HR monitor (Polar Accurex plus, Polar Electro Oy, Kempele, Finland) during the test. When the test began, participants were encouraged to walk at a brisk pace, as fast as possible, throughout the test. At the end of the 2-km walk, the HR and walking time were recorded. Each test was performed between the hours of 8:30 and 10:30 AM, after the standard meal. _ O2max was then predicted considering age, gender, body V mass index (BMI), HR, and walking time measured during the 2-km Walk Test. The walking time was measured using a man_ O2max (ml$kg21$min21) was calculated using ual stopwatch. V the following equation: 116.2 2 2.98 3 (walking time) 2 0.11 3 (finished HR) 2 0.14 3 (age) 2 0.39 3 (BMI) (24,25). Group-Based Step Aerobics Training Program
The group-based step aerobics training program was adapted from a previous study (11). This training program, which was led by the same certified step aerobics instructor, consisted of moderate- to high-intensity step aerobics exercise at a frequency of 3 times per week, meeting regularly at 8:30 and 10:00 AM on Mondays, Wednesdays, and Fridays for 10 weeks. A step aerobics class lasted a total 80–90 minutes, including (a) a warm-up with 10–15 minutes of stretching exercises for major muscles, (b) step aerobics exercise in which the target HR was reached in the first 5–10 minutes and held for another 30–35 minutes (a total of 40–45 minutes), (c) balance and cool down for 10–15 minutes, and (d) stretching and relaxation for 10–15 minutes. The group-based step aerobics exercise program was performed using a low-impact version, in which 1 foot remains in contact with the floor or bench at all times, thereby
preventing any hopping or jumping movements. The step aerobics choreographies included patterns such as the conventional basic step, the “V” step, the “L” step to both the right and left side, alternating step knee-lift sequences, alternating leg up-up-down-down patterns, and step kicks. Arm movements, such as biceps curls and lateral raises at the shoulder level and above the head, were simultaneously incorporated with the selected steps. The music cadence of all sessions was set between 120 and 126 foot strikes per minute. Participants were instructed to know whether they reached the target HRR. The target intensity for all sessions was set at 75–85% HRR, and the HR was monitored every 5 seconds for each session. The step height was initially set at 10 cm, and elevated progressively to reach 75–85% HRR until the step height reached 20–25 cm in week 10 of the intervention. The mean vertical impact force ranged from approximately 1.54 to 1.87 times the body weight (30). Statistical Analyses
Data are expressed as the mean 6 SE. The Mann-Whitney U-test was used to compare both the baseline characteristics and changes between groups in the outcomes from pretraining to posttraining. The Wilcoxon’s rank-sum test was used to compare the baseline and follow-up in each group. Statistical significance was accepted at p # 0.05 for all tests.
RESULTS V_ O2max Prediction
As shown in Table 2, the baseline value for V_ O2max did not differ between the groups, and no significant change was observed before or after the training period in the CG. The V_ O2max value in the TG significantly increased after
TABLE 2. Changes in V_ O2max, PSQI score, and melatonin level. Mean (SE)
V_ O2max (ml$kg21$min21) TG (n = 10) CG (n = 9) PSQI (score) TG (n = 10) CG (n = 9) Melatonin (ng$ml21) TG (n = 10) CG (n = 8)
Pretraining Posttraining
Mean change within-group differences (95% CI)
Mean change between-group differences (95% CI)
16.66 (1.67) 24.40 (0.82) 20.16 (3.85) 17.98 (2.65)
7.75 (4.35 to 11.14)z 21.42 (28.35 to 8.49)
9.17 (2.60 to 15.74)§
9.40 (0.81) 7.40 (0.43) 7.56 (0.34) 7.78 (0.68)
22.00 (0.65 to 3.35)z 0.22 (21.84 to 1.40)
22.22 (24.15 to 22.90)§
32.34 (12.45 to 52.23)z 26.31 (212.87 to 0.25)
38.65 (18.23 to 59.07)§
12.08 (4.20) 44.42 (7.03) 11.81 (2.03) 5.50 (1.39)
*Within-group differences and between-group differences are calculated by Wilcoxon’s rank-sum test and Mann-Whitney U-test, respectively. †CI = confidence interval; TG = training group; CG = control group; PSQI = Pittsburgh sleep quality index. zp # 0.05, significant difference between pretraining and posttraining. §p # 0.05, significant difference between group change.
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Journal of Strength and Conditioning Research the training period (p # 0.05). The change from pretest to posttest in the TG was significantly greater than that in the CG (p # 0.05). Thus, the 10-week period of training induced a significant increment of V_ O2max by 9.17 ml$kg21$min21 (p # 0.05). Pittsburgh Sleep Quality Index Score
The results revealed that there were no differences between the groups regarding the PSQI score at the baseline, as measured by the Mann-Whitney U-test (Table 2). The Wilcoxon’s rank-sum test revealed that the PSQI score achieved an average 2-point reduction in the TG after the training period (p # 0.05), whereas no significant change was observed in the CG (Table 2). The results of the MannWhitney U-test revealed that the 10-week exercise training in the TG induced a significant difference in the PSQI score compared with the CG (between-group difference = 2.22, from 9.40 6 0.81 to 7.40 6 0.43 for the TG, and from 7.56 6 0.34 to 7.78 6 0.68 for the CG; p # 0.05, Table 2). Melatonin Level
The baseline melatonin level did not differ significantly between the groups (Table 2). The Wilcoxon’s rank-sum test indicated that there was no significant change in the CG; however, the melatonin level significantly increased in the TG after the 10-week exercise training (p # 0.05). In addition, significant increases in the values for melatonin (between-group difference = 38.65, from 12.08 6 4.20 to 44.42 6 7.03 pg$ml21 for the TG and from 11.81 6 2.03 to 5.5 6 1.39 pg$ml21 for the CG, p # 0.05) were observed, as indicated by the Mann-Whitney U-test.
DISCUSSION The current study investigated the effects of 10 weeks of group-based moderate- to high-intensity step aerobics training on the sleep quality and melatonin levels of sleepimpaired PMW. The principal findings of this study were that this training program can significantly improve the sleep quality in sleep-impaired PMW, even if conducted for only 10 weeks. In addition, changes in the melatonin levels were significantly greater in the TG than in the CG. Elavsky and McAuley (10) determined that a 4-month moderate-intensity walking or a low-intensity yoga program was ineffective for improving the sleep quality of PMW, according to the PSQI. By contrast, another study by King et al. (15) reported a substantial improvement in the subjective sleep quality measured by the PSQI after the following endurance exercise program: 30–40 minutes of moderate-intensity (60–75% HRR) brisk walking on a treadmill and stationary cycling 4 times per week for 16 weeks . Elavsky and McAuley indicated that the higher intensity of exercise training might be a crucial factor for sleep quality improvement. In the present study, we used moderate- to high-intensity training programs. The participants in the TG performed 3 training sessions per week, involving 40–45 minutes of step aerobics per ses-
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sion. The relative intensity during each training session reached 75–85% HRR, being within the range of moderate to high intensity. The current study was conducted from late autumn to winter (10 weeks); however, the PSQI score did not change within the CG. Therefore, the PSQI might not be affected by seasonal variations. After the 10week step aerobics training program, the mean PSQI score in the TG exhibited a significant reduction of 2 points (9.40–7.40 points) when compared with that of the CG; this change was similar to the findings of King et al. (15), who reported an average reduction of 3 points (8–5.8 points) after a 16-week moderate endurance training program in older women (aged 50–76 years). However, no significant differences were observed in the PSQI scores within the groups at posttest (TG: 7.56 points, CG: 7.78 points). In other words, the mean PSQI of the participants in both the present study and King’s study was still higher than 5 at posttest. It was speculated that a higher intensity with a long-term exercise program might be useful to improve the sleep quality of sleep-impaired PMW. Melatonin is believed to facilitate sleep. An age-associated large decrease in melatonin levels often explains why older people experience sleep problems (18,40). To the best of our knowledge, this is the first study to investigate the effect of step aerobics exercise training on sleep quality and melatonin levels. The current study demonstrated that step aerobics training improved sleep quality and enhanced the melatonin levels in PMW. Most studies on the link between exercise and melatonin have revealed that acute exercise leads to transiently increased melatonin levels (1,7,21,29,34). However, few studies have focused on chronic training effects. The results of cross-sectional studies conflict with the melatonin levels of trained sports girls, female runners, and untrained controls (8,29). The inconsistency in the results most likely lies in the training status of the participants or the routine training programs. Previous studies have indicated that endurance exerciseenhanced melatonin levels play an inhibitory role in menstrual hormone patterns and might lead to an impaired reproductive function (3,8). Serum melatonin changes during the menstrual cycle; the nadir of serum melatonin was detected in the ovulatory phase of the menstrual cycle (36). However, suppression of reproductive physiology by melatonin in humans has not been reliably documented (11). Recent studies have regarded melatonin as an antioxidant and immune system booster rather than a source of impairment to the reproductive function (2,6,20,28). The current study was designed to investigate the response of melatonin on PMW after chronic training. The menopause status in the current study was not only self-reported by the participants as an absence of menstrual cycles for more than 12 consecutive months, but the FSH levels were also further confirmed (ranging from 47.6 to 150.2 mIU$ml21 . 40 mIU$ml21) (26). Thus, the possible influence of melatonin on the menstrual cycle was excluded. The results of the present study indicated VOLUME 28 | NUMBER 9 | SEPTEMBER 2014 |
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Sleep Quality and Melatonin Levels Adapt to Training that 10 weeks of exercise training significantly increased the melatonin level. The findings of the present study are similar to those of Serrano et al., who found that professional road cyclists displayed an increased melatonin level after just a 4day road-cycling competition (31). Serrano et al. indicated that an increase in the melatonin levels can provide a modulatory role in adaptive stress responses, offering protective effects against free radical-mediated damage (31). Taken together, enhanced melatonin production in sleep-impaired PMW may reflect, at least in part, the adaptation of the human body to an exercise-induced increase in antioxidants and immune system activity. Nevertheless, the group-based step aerobics exercise training course in the current study achieved a high attendance rate, and no one dropped out. After the 10-week step aerobics training program, the V_ O2max of the sleep-impaired PMW was significantly improved (9.17 ml$kg21$min21 improvement). This study revealed that step aerobics training might be an appropriate option to persistently motivate PMW to exercise. Not including many participants in both groups might be a limitation of the current study. The participants were rigorously screened not only for postmenopausal sedentary females who were willing to attend a 10-week intervention but also for poor sleep quality (PSQI score .5). In conclusion, our results suggested that a 10-week group-based step aerobics training program at moderateto high-intensity is an effective strategy for improving sleep quality and increasing the melatonin levels in sleepimpaired PMW.
PRACTICAL APPLICATIONS Exercise is a nonpharmacological strategy that has been recommended for improving sleep quality in older adults. This study extended the findings of previous research by demonstrating that moderate- to high-intensity step aerobics training can improve sleep quality in sleep-impaired PMW. This study considered that an exercise strategy to improve sleep quality in PMW should focus, in part, in using moderate- to high-intensity exercise. Based on the interest shown in this training program (high attendance rate), we suggest that PMW may enjoy groupbased step aerobics training for their practice routines (32), and it may be worthwhile to popularize this program for sleep-impaired PMW in fitness clubs and community centers. Hence, coaches should consider using step aerobics training when using physical exercise for improving sleep quality because this may be an appropriate option for PMW. In addition, this study also revealed that step aerobics training improved melatonin levels and aerobic fitness in PMW. Strength and conditioning specialists can educate their members to realize the added value of participating in a step aerobics training program designed to improve sleep quality by increasing melatonin levels and boosting antioxidant capacity and aerobic fitness. Furthermore,
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because the step bench is more portable and less expensive than other exercise equipment, and performing step aerobics training requires little space, strength and conditioning specialists can also teach their student members how to perform step aerobics in private homes.
ACKNOWLEDGMENTS This study was funded by Tzu-Chi University (TCMRC-P99003) and National Science Council (NSC100-2410-H-320014), Taiwan. The authors thank the contribution of all participants and the Union Clinical Laboratory of Taipei, Taiwan, for skillful laboratory assistance.
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Journal of Strength and Conditioning Research 14. Kerschan-Schindl, K, Wiesinger, G, Zauner-Dungl, A, Kollmitzer, J, Fialka-Moser, V, and Quittan, M. Step aerobic vs. cycle ergometer training: Effects on aerobic capacity, coordinative tasks, and pleasure in untrained adults-a randomized controlled trial. Wiener Klinische Wochenschrift 114: 992–998, 2002. 15. King, AC, Oman, RF, Brassington, GS, Bliwise, DL, and Haskell, WL. Moderate-intensity exercise and self-rated quality of sleep in older adults. A randomized controlled trial. JAMA 277: 32–37, 1997. 16. Kline, CE, Sui, X, Hall, MH, Youngstedt, SD, Blair, SN, Earnest, CP, and Church, TS. Dose-response effects of exercise training on the subjective sleep quality of postmenopausal women: Exploratory analyses of a randomised controlled trial. BMJ Open 2: e001044, 2012. doi: 10.1136. 17. Kripke, DF, Brunner, R, Freeman, R, Hendrix, SL, Jackson, RD, Masaki, K, and Carter, RA. Sleep complaints of postmenopausal women. Clin J Womens Health 1: 244–252, 2001. 18. Lee, M, Choh, AC, Demerath, EW, Knutson, KL, Duren, DL, Sherwood, RJ, Sun, SS, Chumlea, WM, Towne, B, Siervogel, RM, and Czerwinski, SA. Sleep disturbance in relation to health-related quality of life in adults: The Fels longitudinal study. J Nutr Health Aging 13: 576–583, 2009. 19. Lemoine, P, Nir, T, Laudon, M, and Zisapel, N. Prolonged-release melatonin improves sleep quality and morning alertness in insomnia patients aged 55 years and older and has no withdrawal effects. J Sleep Res 16: 372–380, 2007. 20. Maldonado, MD, Manfredi, M, Ribas-Serna, J, Garcia-Moreno, H, and Calvo, JR. Melatonin administrated immediately before an intense exercise reverses oxidative stress, improves immunological defenses and lipid metabolism in football players. Physiol Behav 105: 1099–1103, 2012. 21. Monteleone, P, Maj, M, Fusco, M, Orazzo, C, and Kemali, D. Physical exercise at night blunts the nocturnal increase of plasma melatonin levels in healthy humans. Life Sci 47: 1989–1995, 1990. 22. Murphy, PJ and Campbell, SS. Sex hormones, sleep, and core body temperature in older postmenopausal women. Sleep 30: 1788–1794, 2007. 23. Ohayon, MM. Epidemiology of insomnia: What we know and what we still need to learn. Sleep Med Rev 6: 97–111, 2002. 24. Oja, P, Laukkanen, R, Pasanen, M, Tyry, T, and Vuori, I. A 2-km walking test for assessing the cardiorespiratory fitness of healthy adults. Int J Sports Med 12: 356–362, 1991. 25. Rance, M, Boussuge, PY, Lazaar, N, Bedu, M, Van Praagh, E, Dabonneville, M, and Duche´, P. Validity of a VO2 max prediction equation of the 2-km walk test in female seniors. Int J Sports Med 26: 453–456, 2005. 26. Randolph, JF Jr, Crawford, S, Dennerstein, L, Cain, K, Harlow, SD, Little, R, Mitchell, ES, Nan, B, Taffe, J, and Yosef, M. The value of follicle-stimulating hormone concentration and clinical findings as
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markers of the late menopausal transition. J Clin Endocrinol Metab 91: 3034–3040, 2006. 27. Reid, KJ, Baron, KG, Lu, B, Naylor, E, Wolfe, L, and Zee, PC. Aerobic exercise improves self-reported sleep and quality of life in older adults with insomnia. Sleep Med 11: 934–940, 2010. 28. Reiter, RJ, Tan, DX, and Fuentes-Broto, L. Melatonin: A multitasking molecule. Prog Brain Res 181: 127–151, 2010. 29. Ronkainen, H, Vakkuri, O, and Kauppila, A. Effects of physical exercise on the serum concentration of melatonin in female runners. Acta Obstet Gynecol Scand 65: 827–829, 1986. 30. Scharff-Olson, M, Williford, HN, Blessing, DL, Moses, R, and Wang, T. Vertical impact forces during bench-step aerobics: Exercise rate and experience. Percept Mot Skills 84: 267–274, 1997. 31. Serrano, E, Venegas, C, Escames, G, Sa´nchez-Mun˜oz, C, Zabala, M, Puertas, A, de Haro, T, Gutierrez, A, Castillo, M, and AcunaCastroviejo, D. Antioxidant defence and inflammatory response in professional road cyclists during a 4-day competition. J Sports Sci 28: 1047–1056, 2010. 32. Shen, TW and Wen, HJ. Aerobic exercise affects T-wave alternans and heart rate variability in postmenopausal women. Int J Sports Med 34: 1099–1105, 2013. 33. Stevenson, JC. A woman’s journey through the reproductive, transitional and postmenopausal periods of life: Impact on cardiovascular and musculo-skeletal risk and the role of estrogen replacement. Maturitas 70: 197–205, 2011. 34. Theron, JJ, Oosthuizen, JM, and Rautenbach, MM. Effect of physical exercise on plasma melatonin levels in normal volunteers. S Afr Med J 66: 838–841, 1984. 35. Tworoger, SS, Yasui, Y, Vitiello, MV, Schwartz, RS, Ulrich, CM, Aiello, EJ, Irwin, ML, Bowen, D, Potter, JD, and McTiernan, A. Effects of a yearlong moderate-intensity exercise and a stretching intervention on sleep quality in postmenopausal women. Sleep 26: 830–836, 2003. 36. Wetterberg, L, Arendt, J, Paunier, L, Sizonenko, PC, Donselaar, W, and Heyden, T. Human serum melatonin changes during the menstrual cycle. J Clin Endocrinol Metab 42: 185–188, 1976. 37. Yang, PY, Ho, KH, Chen, HC, and Chien, MY. Exercise training improves sleep quality in middle-aged and older adults with sleep problems: A systematic review. J Physiother 58: 157–163, 2012. 38. Yao, KW, Yu, S, Cheng, SP, and Chen, IJ. Relationships between personal, depression and social network factors and sleep quality in community-dwelling older adults. J Nurs Res 16: 131–139, 2008. 39. Youngstedt, SD. Effects of exercise on sleep. Clin Sports Med 24: 355–365, 2005. 40. Zeitzer, JM, Duffy, JF, Lockley, SW, Dijk, DJ, and Czeisler, CA. Plasma melatonin rhythms in young and older humans during sleep, sleep deprivation, and wake. Sleep 30: 1437–1443, 2007.
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AND
HUEI-JHEN WEN3
1
Division of Physical and Health Education, Center for General Education, National Sun Yat-sen University, Kaohsiung City, Taiwan; 2Office of Physical Education, Graduate Institute of Health Care, Chang Gung University of Science and Technology, Taoyuan, County, Taiwan; and 3Center of Physical Education, Tzu-Chi University, Hualien County, Taiwan ABSTRACT
Cai, Z-Y, Wen-Chyuan Chen, K, and Wen, H-J. Effects of a group-based step aerobics training on sleep quality and melatonin levels in sleep-impaired postmenopausal women. J Strength Cond Res 28(9): 2597–2603, 2014—The purpose of this study was to investigate the effect of regular moderateto high-intensity step aerobics training on the melatonin levels and sleep quality of sleep-impaired postmenopausal women (PMW). PMW with poor sleep (having a score over 5 in the Chinese version of the Pittsburgh sleep quality index [PSQI]) were divided into a training group (TG, n = 10) and an age-, height-, weight-, and PSQI score-matched control group (CG, n = 9). The participants in the TG performed 40–45 minutes of step aerobics exercise 3 times per week for 10 weeks at an intensity of 75–85% of the heart rate reserve, whereas the participants in the CG maintained their regular lifestyle. The fasting blood was analyzed, and the PSQI questionnaire and aerobic fitness test were administered before and after the 10week program. The results revealed that for the participants in the TG, the PSQI score significantly decreased (TG from 9.40 6 0.81 to 7.40 6 0.43; CG from 7.56 6 0.34 to 7.78 6 0.68; between-group difference = 2.22, p # 0.05) and the melatonin levels significantly increased (TG from 12.08 6 4.20 to 44.42 6 7.03 pg$ml21; CG from 11.81 6 2.03 to 5.5 6 1.39 pg$ml21, between-group difference = 38.65, p # 0.05). In conclusion, a 10-week moderate- to high-intensity step aerobics training program can improve sleep quality and increase the melatonin levels in sleep-impaired PMW. Therefore, regular moderate- to high-intensity step aerobics training is recommended for sleep-impaired PMW.
KEY WORDS Pittsburgh sleep quality index score, exercise, moderate- to high-intensity, heart rate reserve Address correspondence to Huei-Jhen Wen, [email protected]. 28(9)/2597–2603 Journal of Strength and Conditioning Research Ó 2014 National Strength and Conditioning Association
INTRODUCTION
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enopause, the permanent cessation of menstruation and fertility (33), is a normal part of the female aging process and is accompanied by prominent hormonal changes; unpleasant physical conditions, such as sleep disturbances, may also occur (22). Studies have indicated that sleep complaints increase with age (23), and that disturbed sleep is extremely frequent among postmenopausal women (PMW) (17,23). In Taiwan, a survey study indicated that almost half of PMW reported feeling dissatisfied with their sleep (7), and sleep problems or poor sleep qualities were more likely to be reported in PMW than in premenopausal women. Therefore, strategies that alleviate sleep-related problems are vital because sleep-related problems may have a major effect on the quality of life (18). Regular exercise has widely been considered to be a nonpharmacological therapeutic strategy against sleep disturbances (39). Research has indicated that regular exercise has positive effects on sleep quality (27,37). However, studies investigating the effects of exercise on sleep problems in PMW are limited (10,15,16,35). Of these studies, 2 correlated studies reported that training at higher intensity results in less sleep disturbances (16,35). An experimental study reported that a 4-month moderate-intensity walking program and a low-intensity yoga program failed to yield improvements in sleep quality (10). By contrast, another study by King et al. (15) reported a substantial improvement in subjective sleep quality after 16 weeks of moderate-intensity exercise training, implying that an exercise intervention at a higher intensity may be required to induce such improvements. However, not all the participants in King’s study were poor sleepers, as estimated by their Pittsburgh sleep quality index (PSQI) score (5). Recent evidence has linked sleep and melatonin levels (19,40). The production of melatonin, which is secreted by the pineal gland, is inhibited by light and enhanced by darkness, constituting the circadian rhythm (11). A nocturnal rise in the melatonin level makes individuals fall asleep, a process that occurs with the obvious physiological events of lowered VOLUME 28 | NUMBER 9 | SEPTEMBER 2014 |
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Sleep Quality and Melatonin Levels Adapt to Training body temperature, heart rate (HR), blood pressure, and sympathetic tone (9). The production of melatonin decreases as a person ages; this decrease may be the reason that older people often experience more sleep problems than do young people (19,40). In addition to its role in regulating sleep and circadian rhythms, melatonin also boosts antioxidant activity and the immune system (2,6,20). Maintaining adequate levels of melatonin is believed to benefit human health (28). Not all studies investigating the effects of acute exercise on the melatonin levels in humans have reached the same conclusion. However, most have revealed an increase in melatonin levels shortly and transiently after daytime exercise (7,29,34), and conversely, a decrease in the melatonin levels after exercise in the late evening (in the rising phase of melatonin secretion) (1,21,22). Nevertheless, few studies have investigated chronic training effects. A cross-sectional study indicated that there were no differences in the melatonin levels between recreational runners and their controls (29), but another study reported that the daytime melatonin levels of girls who played sports were substantially higher than the melatonin level of the controls (9). Moreover, an experimental study indicated an adaptive increase in the levels of plasma melatonin in professional road cyclists after a 4-day road-cycling competition (31). However, whether the melatonin level would increase after chronic training has not been established in sleep-impaired PMW. Previous studies examining the effect of exercise on the sleep quality or melatonin level have not considered groupbased exercise. Research has indicated that when social interaction is involved in the exercise atmosphere, such as in a group-based exercise program, participation of individuals can be sustained (4). From the perspective of exercise adherence, it is crucial to design an exercise intervention that is suitable for an aging population and sustainable in the long term. Step aerobics can be a form of group-based exercise and is characterized by rhythmical movements on a step, performed to cadenced musical arrangements. This exercise is easy to learn, its intensity can be adapted easily (by choosing the step height, music tempo, and similar factors), and does not require special equipment, which may meet the needs of an aging population. Previous studies have revealed that adherence was greater when individuals participated in group-based step aerobics training than when they participated in an individual cycle ergometer training (14). In addition, recent studies have indicated that group-based step aerobics training is an effective strategy for promoting improvements in the functional fitness and cardiovascular condition of apparently healthy older women (13,32). Taken together, step aerobics may be recommended as a suitable exercise modality for PMW. Therefore, the purpose of this study was to investigate the effects of regular group-based moderate- to high-intensity step aerobics training on the sleep quality and melatonin levels of sleep-impaired PMW. The hypothesis of the current study was that for PMW with a sleep disturbance, the melatonin
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levels would increase, and the sleep quality would improve after a regular group-based moderate- to high-intensity step aerobics training program.
METHODS Experimental Approach to the Problem
To investigate regular moderate- to high-intensity groupbased step aerobics training in sleep-impaired PMW, inclusion criteria for participants had to be created, and exercise intensity that met the appropriate range had to be confirmed. Initially, 44 female volunteers with a sedentary lifestyle, who self-reported the absence of menstrual cycles for more than 12 consecutive months, as well as sleep disturbances, were registered for the current study. The Institutional Review Board of the National Dung-Hwa University Institute approved all methods and procedures, and all participants provided written informed consent. Subsequently, the 44 PMW underwent a pretest, which included a fasting blood sample, anthropometric measurements, the Chineseversion PSQI, and an aerobic fitness test 2 days before the exercise training. Twenty-five participants were excluded because they were not poor sleepers (4) (PSQI #5), or they had taken sleeping pills, caffeinated beverages, or antioxidant supplements for at least 2 months before the study. Finally, 19 PMW with a sleep disturbance were selected for the study, and these PMW were divided into a training group (TG, n = 10) and an age-, height-, weight-, and PSQI score-matched control group (CG, n = 9). Given that Serrano et al. (31) indicated that a high-intensity exercise intervention may be required to improve sleep quality, the training protocol for the TG participants included 40–45 minutes of group-based step aerobics exercise training at 75–85% of the heart rate reserve (HRR) 3 times per week for 10 weeks, which met the moderate- to high-intensity exercise classification prescribed by the American College of Sports Medicine (12), whereas participants in the CG did not change their regular lifestyle. A posttest was conducted for the participants in the TG and CG 2 days after the 10-week exercise training. To minimize diurnal variance, all pretest and posttest measurements were obtained at the same time in the morning. The fasting blood samples, anthropometric measurements, PSQI score, and aerobic fitness tests were conducted pretraining and posttraining to document and compare any significant changes between the TG and CG. Subjects
Initially, 44 self-reported postmenopausal sedentary women ages 54 to 65 years old were recruited through radio and newspaper advertisements. The participants had no history of respiratory or cardiac diseases, were nonsmokers, and were not heavy alcohol or coffee drinkers. In addition, the participants had not used hormone replacement therapy in the previous year. After informing participants of the purpose, testing, training procedures, and potential risks of
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Journal of Strength and Conditioning Research the study, all of them signed an informed consent form. The study was approved by the Ethics Committee of the National Dong-Hwa University, the local equivalent of an Institutional Review Board. As previously mentioned, 25 participants were excluded. The follice-stimulating hormone (FSH) values of the remaining 19 participants, including 10 participants for the TG and 9 participants for the CG (Table 1), exceeded 40 mIU$ml21 (ranging from 47.6 to 150.2 mIU$ml21), thus meeting the inclusion criteria for menopause (26). In the present study, 1 participant from the CG withdrew from the tests for predicting V_ O2max after the training period because of an ankle sprain. Finally, only 10 participants from the TG and 8 participants from the CG were considered for predicting the V_ O2max. Procedures
The study lasted from late autumn to winter. On the assessments days, the fasting blood samples of the participants were drawn, followed by anthropometric measurements. Subsequently, the participants ate a standard meal (a sandwich, a cup of soy milk, and water) while completing a PSQI questionnaire. The aerobic fitness tests were conducted approximately 1 hour after the standard breakfast. In addition, the participants were instructed to avoid vigorous exercise or physical activity for 24 hours before the assessment days. Blood Sample Collection and Analysis
To minimize diurnal variance, all fasting blood samples were obtained in the morning between 7:30 and 9:30 AM. The blood samples were taken from an antecubital vein, using a needle and vacutainer, both before and after the step aerobics training program. Blood samples were stored at 48 C and centrifuged at 1500 rpm for 30 minutes, within 2 hours of sampling. Subsequently, the serum samples were stored at 2808 C for further serum marker assays. The serum samples were sent to the Union Clinical Laboratory, Taipei, Taiwan, for analysis. All the assays were performed according to the instructions of the manufacturers.
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The melatonin levels were analyzed using an enzyme-linked immunosorbent assay kit (IBL, Hamburg, Germany). The sensitivity and the interassay and intra-assay coefficients of variance were 1.6 pg$ml21, 3.0–11.4%, and 4–19.3%, respectively. The FSH assays were all performed using a commercial 2-site sandwich immunoassay automated chemiluminescence system (Advia Centaur; Siemens Healthcare Diagnostics, Inc., Tarrytown, NY, USA). The sensitivity and interassay and intra-assay CV were 0.3 mIU$ml21, 2.9 and 2.7%, respectively. All serum samples were analyzed in duplicate. To minimize the effects of interassay variation, all samples from 1 participant were analyzed in the same assay. Sleep Quality Measurements
Sleep quality was evaluated using the Chinese version of the PSQI, before and after the step aerobics training program. The PSQI is a self-rated questionnaire that has been validated as an instrument to assess sleep quality and disturbances over a 1-month interval. The test-retest reliability of the PSQI is 0.87 (5). The PSQI contains 7 evaluative components: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbance, sleeping medication, and daytime dysfunction. Each component is scored from 0 to 3. The sum of the 7 components is calculated as the global PSQI score (with potential scores ranging from 0 to 21). A higher global PSQI score indicates poorer sleep quality, with a score .5 having a diagnostic sensitivity of 89.6% and specificity of 86.5% to differentiate effective and poor sleepers (5). The content validity and internal consistency of the PSQI were rechecked by Yao et al. (38), who determined a Cronbach’s a of 0.85. V_ O2max Prediction
The V_ O2max was predicted using the 2-km Walk Test (Urho Kaleva Kekkonen Institute, Tampere, Finland) because of its ease, acceptability, and safety for older people (25). This test has also been shown to be a feasible and accurate method for predicting V_ O2max in healthy 20- to 65-year-old participants and was not substantially different from measured V_ O2max (24,25). All participants performed TABLE 1. Characteristic of the subjects at baseline. the 2-km Walk Test before and after the step aerobics training TG (n = 10) CG (n = 9) p period. The test was performed Age (y) 57.60 6 0.69 59.33 6 1.13 0.142 by walking 2 km on a flat Height (m) 154.45 6 3.52 154.08 6 4.82 0.128 surface indoors in a gymnasium Weight (kg) 54.15 6 1.62 57.83 6 1.95 0.761 to limit the effect of varying 22 BMI (kg$m ) 22.70 6 0.62 24.45 6 1.05 0.362 climatic conditions. The ground Age of first period (y) 12.90 6 0.48 14.00 6 0.55 0.181 was regularly marked throughMenopause age (y) 49.30 6 0.96 48.11 6 2.55 0.562 out the walking distance. Before Data are expressed as the mean 6 SE. Between-group differences were calculated by the test, the exercise leaders led Mann-Whitney U-test. the standard warm-up, which TG = training group; CG = control group; BMI = body mass index. included knee-up activity and lower-limb stretching for 5 VOLUME 28 | NUMBER 9 | SEPTEMBER 2014 |
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Sleep Quality and Melatonin Levels Adapt to Training minutes. After the warm-up, the participants were instructed to wear a HR monitor (Polar Accurex plus, Polar Electro Oy, Kempele, Finland) during the test. When the test began, participants were encouraged to walk at a brisk pace, as fast as possible, throughout the test. At the end of the 2-km walk, the HR and walking time were recorded. Each test was performed between the hours of 8:30 and 10:30 AM, after the standard meal. _ O2max was then predicted considering age, gender, body V mass index (BMI), HR, and walking time measured during the 2-km Walk Test. The walking time was measured using a man_ O2max (ml$kg21$min21) was calculated using ual stopwatch. V the following equation: 116.2 2 2.98 3 (walking time) 2 0.11 3 (finished HR) 2 0.14 3 (age) 2 0.39 3 (BMI) (24,25). Group-Based Step Aerobics Training Program
The group-based step aerobics training program was adapted from a previous study (11). This training program, which was led by the same certified step aerobics instructor, consisted of moderate- to high-intensity step aerobics exercise at a frequency of 3 times per week, meeting regularly at 8:30 and 10:00 AM on Mondays, Wednesdays, and Fridays for 10 weeks. A step aerobics class lasted a total 80–90 minutes, including (a) a warm-up with 10–15 minutes of stretching exercises for major muscles, (b) step aerobics exercise in which the target HR was reached in the first 5–10 minutes and held for another 30–35 minutes (a total of 40–45 minutes), (c) balance and cool down for 10–15 minutes, and (d) stretching and relaxation for 10–15 minutes. The group-based step aerobics exercise program was performed using a low-impact version, in which 1 foot remains in contact with the floor or bench at all times, thereby
preventing any hopping or jumping movements. The step aerobics choreographies included patterns such as the conventional basic step, the “V” step, the “L” step to both the right and left side, alternating step knee-lift sequences, alternating leg up-up-down-down patterns, and step kicks. Arm movements, such as biceps curls and lateral raises at the shoulder level and above the head, were simultaneously incorporated with the selected steps. The music cadence of all sessions was set between 120 and 126 foot strikes per minute. Participants were instructed to know whether they reached the target HRR. The target intensity for all sessions was set at 75–85% HRR, and the HR was monitored every 5 seconds for each session. The step height was initially set at 10 cm, and elevated progressively to reach 75–85% HRR until the step height reached 20–25 cm in week 10 of the intervention. The mean vertical impact force ranged from approximately 1.54 to 1.87 times the body weight (30). Statistical Analyses
Data are expressed as the mean 6 SE. The Mann-Whitney U-test was used to compare both the baseline characteristics and changes between groups in the outcomes from pretraining to posttraining. The Wilcoxon’s rank-sum test was used to compare the baseline and follow-up in each group. Statistical significance was accepted at p # 0.05 for all tests.
RESULTS V_ O2max Prediction
As shown in Table 2, the baseline value for V_ O2max did not differ between the groups, and no significant change was observed before or after the training period in the CG. The V_ O2max value in the TG significantly increased after
TABLE 2. Changes in V_ O2max, PSQI score, and melatonin level. Mean (SE)
V_ O2max (ml$kg21$min21) TG (n = 10) CG (n = 9) PSQI (score) TG (n = 10) CG (n = 9) Melatonin (ng$ml21) TG (n = 10) CG (n = 8)
Pretraining Posttraining
Mean change within-group differences (95% CI)
Mean change between-group differences (95% CI)
16.66 (1.67) 24.40 (0.82) 20.16 (3.85) 17.98 (2.65)
7.75 (4.35 to 11.14)z 21.42 (28.35 to 8.49)
9.17 (2.60 to 15.74)§
9.40 (0.81) 7.40 (0.43) 7.56 (0.34) 7.78 (0.68)
22.00 (0.65 to 3.35)z 0.22 (21.84 to 1.40)
22.22 (24.15 to 22.90)§
32.34 (12.45 to 52.23)z 26.31 (212.87 to 0.25)
38.65 (18.23 to 59.07)§
12.08 (4.20) 44.42 (7.03) 11.81 (2.03) 5.50 (1.39)
*Within-group differences and between-group differences are calculated by Wilcoxon’s rank-sum test and Mann-Whitney U-test, respectively. †CI = confidence interval; TG = training group; CG = control group; PSQI = Pittsburgh sleep quality index. zp # 0.05, significant difference between pretraining and posttraining. §p # 0.05, significant difference between group change.
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Journal of Strength and Conditioning Research the training period (p # 0.05). The change from pretest to posttest in the TG was significantly greater than that in the CG (p # 0.05). Thus, the 10-week period of training induced a significant increment of V_ O2max by 9.17 ml$kg21$min21 (p # 0.05). Pittsburgh Sleep Quality Index Score
The results revealed that there were no differences between the groups regarding the PSQI score at the baseline, as measured by the Mann-Whitney U-test (Table 2). The Wilcoxon’s rank-sum test revealed that the PSQI score achieved an average 2-point reduction in the TG after the training period (p # 0.05), whereas no significant change was observed in the CG (Table 2). The results of the MannWhitney U-test revealed that the 10-week exercise training in the TG induced a significant difference in the PSQI score compared with the CG (between-group difference = 2.22, from 9.40 6 0.81 to 7.40 6 0.43 for the TG, and from 7.56 6 0.34 to 7.78 6 0.68 for the CG; p # 0.05, Table 2). Melatonin Level
The baseline melatonin level did not differ significantly between the groups (Table 2). The Wilcoxon’s rank-sum test indicated that there was no significant change in the CG; however, the melatonin level significantly increased in the TG after the 10-week exercise training (p # 0.05). In addition, significant increases in the values for melatonin (between-group difference = 38.65, from 12.08 6 4.20 to 44.42 6 7.03 pg$ml21 for the TG and from 11.81 6 2.03 to 5.5 6 1.39 pg$ml21 for the CG, p # 0.05) were observed, as indicated by the Mann-Whitney U-test.
DISCUSSION The current study investigated the effects of 10 weeks of group-based moderate- to high-intensity step aerobics training on the sleep quality and melatonin levels of sleepimpaired PMW. The principal findings of this study were that this training program can significantly improve the sleep quality in sleep-impaired PMW, even if conducted for only 10 weeks. In addition, changes in the melatonin levels were significantly greater in the TG than in the CG. Elavsky and McAuley (10) determined that a 4-month moderate-intensity walking or a low-intensity yoga program was ineffective for improving the sleep quality of PMW, according to the PSQI. By contrast, another study by King et al. (15) reported a substantial improvement in the subjective sleep quality measured by the PSQI after the following endurance exercise program: 30–40 minutes of moderate-intensity (60–75% HRR) brisk walking on a treadmill and stationary cycling 4 times per week for 16 weeks . Elavsky and McAuley indicated that the higher intensity of exercise training might be a crucial factor for sleep quality improvement. In the present study, we used moderate- to high-intensity training programs. The participants in the TG performed 3 training sessions per week, involving 40–45 minutes of step aerobics per ses-
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sion. The relative intensity during each training session reached 75–85% HRR, being within the range of moderate to high intensity. The current study was conducted from late autumn to winter (10 weeks); however, the PSQI score did not change within the CG. Therefore, the PSQI might not be affected by seasonal variations. After the 10week step aerobics training program, the mean PSQI score in the TG exhibited a significant reduction of 2 points (9.40–7.40 points) when compared with that of the CG; this change was similar to the findings of King et al. (15), who reported an average reduction of 3 points (8–5.8 points) after a 16-week moderate endurance training program in older women (aged 50–76 years). However, no significant differences were observed in the PSQI scores within the groups at posttest (TG: 7.56 points, CG: 7.78 points). In other words, the mean PSQI of the participants in both the present study and King’s study was still higher than 5 at posttest. It was speculated that a higher intensity with a long-term exercise program might be useful to improve the sleep quality of sleep-impaired PMW. Melatonin is believed to facilitate sleep. An age-associated large decrease in melatonin levels often explains why older people experience sleep problems (18,40). To the best of our knowledge, this is the first study to investigate the effect of step aerobics exercise training on sleep quality and melatonin levels. The current study demonstrated that step aerobics training improved sleep quality and enhanced the melatonin levels in PMW. Most studies on the link between exercise and melatonin have revealed that acute exercise leads to transiently increased melatonin levels (1,7,21,29,34). However, few studies have focused on chronic training effects. The results of cross-sectional studies conflict with the melatonin levels of trained sports girls, female runners, and untrained controls (8,29). The inconsistency in the results most likely lies in the training status of the participants or the routine training programs. Previous studies have indicated that endurance exerciseenhanced melatonin levels play an inhibitory role in menstrual hormone patterns and might lead to an impaired reproductive function (3,8). Serum melatonin changes during the menstrual cycle; the nadir of serum melatonin was detected in the ovulatory phase of the menstrual cycle (36). However, suppression of reproductive physiology by melatonin in humans has not been reliably documented (11). Recent studies have regarded melatonin as an antioxidant and immune system booster rather than a source of impairment to the reproductive function (2,6,20,28). The current study was designed to investigate the response of melatonin on PMW after chronic training. The menopause status in the current study was not only self-reported by the participants as an absence of menstrual cycles for more than 12 consecutive months, but the FSH levels were also further confirmed (ranging from 47.6 to 150.2 mIU$ml21 . 40 mIU$ml21) (26). Thus, the possible influence of melatonin on the menstrual cycle was excluded. The results of the present study indicated VOLUME 28 | NUMBER 9 | SEPTEMBER 2014 |
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Sleep Quality and Melatonin Levels Adapt to Training that 10 weeks of exercise training significantly increased the melatonin level. The findings of the present study are similar to those of Serrano et al., who found that professional road cyclists displayed an increased melatonin level after just a 4day road-cycling competition (31). Serrano et al. indicated that an increase in the melatonin levels can provide a modulatory role in adaptive stress responses, offering protective effects against free radical-mediated damage (31). Taken together, enhanced melatonin production in sleep-impaired PMW may reflect, at least in part, the adaptation of the human body to an exercise-induced increase in antioxidants and immune system activity. Nevertheless, the group-based step aerobics exercise training course in the current study achieved a high attendance rate, and no one dropped out. After the 10-week step aerobics training program, the V_ O2max of the sleep-impaired PMW was significantly improved (9.17 ml$kg21$min21 improvement). This study revealed that step aerobics training might be an appropriate option to persistently motivate PMW to exercise. Not including many participants in both groups might be a limitation of the current study. The participants were rigorously screened not only for postmenopausal sedentary females who were willing to attend a 10-week intervention but also for poor sleep quality (PSQI score .5). In conclusion, our results suggested that a 10-week group-based step aerobics training program at moderateto high-intensity is an effective strategy for improving sleep quality and increasing the melatonin levels in sleepimpaired PMW.
PRACTICAL APPLICATIONS Exercise is a nonpharmacological strategy that has been recommended for improving sleep quality in older adults. This study extended the findings of previous research by demonstrating that moderate- to high-intensity step aerobics training can improve sleep quality in sleep-impaired PMW. This study considered that an exercise strategy to improve sleep quality in PMW should focus, in part, in using moderate- to high-intensity exercise. Based on the interest shown in this training program (high attendance rate), we suggest that PMW may enjoy groupbased step aerobics training for their practice routines (32), and it may be worthwhile to popularize this program for sleep-impaired PMW in fitness clubs and community centers. Hence, coaches should consider using step aerobics training when using physical exercise for improving sleep quality because this may be an appropriate option for PMW. In addition, this study also revealed that step aerobics training improved melatonin levels and aerobic fitness in PMW. Strength and conditioning specialists can educate their members to realize the added value of participating in a step aerobics training program designed to improve sleep quality by increasing melatonin levels and boosting antioxidant capacity and aerobic fitness. Furthermore,
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because the step bench is more portable and less expensive than other exercise equipment, and performing step aerobics training requires little space, strength and conditioning specialists can also teach their student members how to perform step aerobics in private homes.
ACKNOWLEDGMENTS This study was funded by Tzu-Chi University (TCMRC-P99003) and National Science Council (NSC100-2410-H-320014), Taiwan. The authors thank the contribution of all participants and the Union Clinical Laboratory of Taipei, Taiwan, for skillful laboratory assistance.
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