EFFECTS OF DIFFERENT TRAINING AMPLITUDES HEART RATE AND HEART RATE VARIABILITY IN YOUNG ROWERS MARCELO S. VAZ, LUAN M. PICANC¸O,
AND
ON
FABRI´CIO B. DEL VECCHIO
Superior School of Physical Education, Federal University of Pelotas, Brazil ABSTRACT Vaz, MS, Picanc¸o, LM, and Del Vecchio, FB. Effects of different training amplitudes on heart rate and heart rate variability in young rowers. J Strength Cond Res 28(10): 2967–2972, 2014—The aim of this study was to investigate the autonomic nervous system recovery and the psychological response as a result of 3 training amplitudes on heart rate (HR), heart rate variability (HRV), and rate of perceived exertion (RPE) in rowing. Eight young rowers (16.8 6 1.4 years) performed, in a randomized fashion, 2 sessions of highintensity interval training, with high and low amplitude and a continuous training (CT) session, with the same exercise duration (10 minutes) and mean intensity (60% of maximal stroke test). The data of HR, HRV, and RPE were collected 5 minutes before, immediately after each session, and 24 hours later. High amplitude promoted higher impact in maximum HR (p # 0.05) and RPE (p , 0.001) when compared with CT. For the time domain HRV variable, there was a statistically significant difference between moments of rest (pretraining or post 24 hours) and posttraining in all training sessions. Originally, we conclude that training with higher load variation between effort and recovery impacts HRV, HR, and RPE with greater intensity, but the younger rowers were ready for new training sessions 24 hours after either training method. Coaches can use the polarized training method, observing the stimulus nature and time required for recovery, because it may be an adequate strategy for the development of rower’s conditioning.
KEY WORDS athletes, autonomic nervous system, physical fitness, rate of perceived exertion
Address correspondence to Marcelo dos Santos Vaz, marcelo.dsvaz@ gmail.com. 28(10)/2967–2972 Journal of Strength and Conditioning Research Ó 2014 National Strength and Conditioning Association
INTRODUCTION
I
n rowing, the training commonly applied is characterized with low intensity and long duration (15,23), especially, because the competitions are conducted in 2,000-m races, which lasts from 6 to 8 minutes, and the aerobic metabolism is predominant, with a contribution of 87 6 2% (21). Furthermore, recent studies have found that high-intensity interval training (HIIT) is an adequate method for the improvement of physical fitness components required in rowing (9,12). For the HIIT program organization, different variables need to be manipulated at the same time (7). Studies frequently evaluate the effects of different effort intensities and recovery (15–17). However, the amplitude, which is characterized by the magnitude of variation between effort and rest, allows prescriptions of training with distinct effort-pause ratios, but with equal mean intensity. Although this is an important tool in the control of training load (3,4), it has been poorly investigated. Parameterizing the training sessions by the mean intensity may be interesting to handle the training load over an entire period (12). Until recently, most HIIT protocols have adopted the strategy of manipulating the duration and intensity as load components; only lately has the amplitude been studied (3,4). In this context, 2 training protocols were matched for the duration, mean intensity, and covered distance but with different amplitudes (0 and ;30%), and the authors found no differences between the protocols for heart rate (HR), RPE, and blood lactate concentration during exercise (3). In another case, researchers who studied 3 types of training over the same distance covered but with different intensities and effort duration noted that the protocols with greater variation between effort and pause were those that produced the greatest impact on the autonomic nervous system (ANS), obtaining statistically significant correlations between RPE and HR using the heart rate variability (HRV) parameters (17). In this context, some HRV components have been associated with organic overload (17), and that also could contribute to the process of training load control by assessing day after day the HRV data in different moments as pretraining, immediate posttraining, and after 24 hours (22,24). When studied with constant load exercises and with VOLUME 28 | NUMBER 10 | OCTOBER 2014 |
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Different Training Amplitudes in Young Rowers interval exercises, HRV showed a delay in the recovery after the HIIT exercises (17). In relation to HIIT, other studies have explored how this type of exercise affects activity of the ANS, which can be inferred by HRV (28,30). Additionally, the manipulation of the stimuli duration and intensity and its relation to HRV were studied in endurancetrained adults, and the results indicated that the posttraining HRV data may offer important information about the training load in different durations and intensities of HIIT (17); however, no information has been provided regarding how the ANS responds acutely and 24 hours after to amplitude manipulation (4,13), especially considering similar mean intensities. The amplitude allows comparing different training protocols with the same mean intensity and different effort and recovery loads. In this sense, low and average amplitudes can promote similar impacts on metabolic and performance variables (10), and the coaches can choose the better training stimulus considering this information. Moreover, these data could help in the prescription of the training, especially an HIIT approach, which does not have a gold standard for the training load measurement. Thus, the objective of this study was to investigate the ANS recovery and rating of perceived effort (RPE) as a result of 3 training amplitudes (0, 50, and 100%) in young rowers.
METHODS Experimental Approach to the Problem
This is a counterbalanced experimental study with repeated measures. The training amplitude was considered as the independent variable, and rate of perceived exertion (RPE), HR, and HRV parameters were considered as the dependent variables.
Figure 1.
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The study consisted of 4 different sessions, separated by 48 hours. In the first session, an anamnesis was obtained, and the maximum stroke test was performed. In the 3 subsequent sessions, training with different amplitudes was conducted, with the execution order determined randomly (Figure 1). The rowers performed 3 training sessions with the execution order determined randomly, using the same exercise duration (10 minutes) and matched average intensity; this was calculated from the sum of effort and pause intensities divided by two. The detail that distinguished the 3 protocols was the amplitude of effort-pause ratio (Figure 2), i.e., the ratio of the difference between exercise intensity and the average intensity divided by the average intensity (4). The idea of equating the training sessions by time and intensity was to isolate the amplitude as the only variable that distinguished the protocols, enabling the comparison and assuming the amplitude as the main reason of the different impact in the dependent variables. Subjects
Eight young male rowers, free of injuries with at least 1 year of practice in the sport, were involved in the study; the participants were selected by convenience from the only amateur club of the city. All rowers and their parents signed a consent form of participation, which was approved by the local ethics committee (protocol 005/2012). The subjects were 16.8 6 1.4 years old (15–19 years), 180 6 7 cm tall, and had a body mass of 71.3 6 12.6 kg. Maximal Stroke Test
To estimate the maximum stroke (Smax) in strokes per minute (spm), a progressive maximum test was conducted with a Single Skiff (Canoe Simples; Holos, Brazil) equipped with a stroke counter (Speed Coach Gold; NK, Boothwyn, PA, USA). The evaluation procedure consisted of a 5-minute warm-up that was intensity and cadence free. Immediately after, the test began with a cadence of 14 spm. Each stage lasted for 2 minutes with 30-second interval between them (29). After each stage was completed, an increase of 2 spm was applied, and the test was ended when the rower could not complete the stage. As a parameter for interruption, the inability to sustain the pace of the stage for more than 5 strokes was considered. During testing, the evaluators followed the rowers with a motorized boat and used a counter stroke (Interval 2000; NK) to maintain the cadence control. In the maximal stroke Experimental design. HR = heart rate; RPE = rate of perceived exertion; HRV = heart rate variability. test, a frequency of 24.71 6 1.36 spm was obtained. the
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average intensity remained at 60% (120:0), but the amplitude was 100%. Data Collection Figure 2. Amplitude equation.
Training Session Procedures
The training sessions involved a continuous training (CT) and 2 interval training, one with low (LAT) and another with high amplitude (HAT), which are presented in Table 1 and described below. For all training sessions, the subjects were instructed to sleep adequately (8 hours at minimum), have a habitual breakfast, not perform vigorous exercise in the 24 hours preceding assessment, and avoid ingesting caffeine, which modifies different HRV parameters (18). Continuous Training
Continuous training was composed of a constant stimulus with an intensity of 60% Smax obtained in the maximal stroke test. The athletes rowed uninterruptedly for 10 minutes. The effort in the CT was 14.85 6 1.56 spm. Interval Training With Low Amplitude
Low amplitude was structured with 5 effort-pause blocks with a 1:1 ratio. During efforts lasting 60 seconds, the intensity was 90% Smax; during active recovery, which was also a period of 60 seconds, the intensity was 30% Smax. The LAT effort-pause ratio was 22.8 6 2.3:7.4 6 0.8 spm. Although the average intensity was fixed at 60% (90:30) of Smax, the training amplitude was 50%. Interval Training With High Amplitude
High amplitude was composed of 10 effort-pause blocks with the same ratio of LAT (1:1) but with an intensity of 120% Smax during the 60 seconds of effort and passive recovery during the 60-second pause. The effort-pause ratio in the HAT was 29.7 6 2.6:0 spm. In this case, the
and Recording
For each subject, HR monitoring was recorded for 5 minutes before and 5 minutes after the end of each session (acute response) and during 5 minutes 24 hours after training (considered a delayed response). The period of 300 seconds is considered valid and sufficient for obtaining the adequate information about HRV variables (14). The pretraining and posttraining data recordings were conducted with the subject seated and immobile in the boat, and after 24 hours, the data were collected with the subjects sitting on the floor to simulate the position taken in the boat. The HRV parameters, properly registered with validated procedures and equipment for data filtering (25), were organized into 2 domains: time and frequency (11). For the time domain, the root mean square of successive differences squared was collected and analyzed. In the frequency domain, spectral components were assessed: (a) very low frequency: 0–0.04 Hz, (b) low frequency: 0.04–0.15 Hz (LF), (c) high frequency: 0.15–0.4 (HF), and (d) the LF/HF ratio (16). The HR and HRV data were collected with an HR monitor (Polar RS800CX; Polar Electro OY, Kempele, Finland), transferred to the Polar ProTrainer 5 software, and analyzed using the software Kubios HRV 2.0 (University of Kuopio, Finland). For HR, we considered the average values of HR across the test interval and maximum HR as the highest at any given point in the collection. The RPE information was collected with the Borg scale (0–10) (5) after the end of each session and is shown as arbitrary units (au). Statistical Analyses
Data analysis was performed using the software OriginPro 8.5. For descriptive presentation, the mean and SD were used. Mauchly’s test was used to test the data sphericity, and the Greenhouse-Geisser correction TABLE 1. General characteristics of continuous and interval training sessions.* was used when appropriate CT LAT HAT (20). We conducted 2-way analysis of variance (ANOVA), trainTotal duration of exercise (min) 10 10 10 Effort: pause ratio NA 1:1 1:1 ing type and time of analysis, Effort intensity (% Smax) 60 90 120 with repeated measures over Pause intensity (% Smax) NA 30 0 the second factor. When signifiAverage training intensity (% Smax) 60 60 60 cance was detected by ANOVA, Training amplitude (%) 0 50 100 we used the Bonferroni test to Total duration of session (min) 10 10 20 identify differences. For the cor*CT = continuous protocol; LAT = intermittent protocol with average amplitude; HAT = relations between variables of intermittent protocol with large amplitude; % Smax = percentage of maximum intensity interest, we used the Pearson’s reached in the test; NA = not applicable. test. The statistically significant level was set at 5%. VOLUME 28 | NUMBER 10 | OCTOBER 2014 |
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Different Training Amplitudes in Young Rowers
TABLE 2. Mean 6 SD from HRV time and frequency domains parameters.* HAT RMSSD (ms) Pretraining Posttraining Post-24 h VLF (ms2) Pretraining Post-24 h LF (ms2) Pretraining Post-24 h HF (ms2) Pretraining Post-24 h LF/HF (%) Pretraining Post-24 h
LAT
47.7 6 21.3† 4.2 6 1.4 53.1 6 28.9†
CT
54.3 6 22.9† 9.9 6 7.4 48.5 6 24.1†
55.98 6 2† 11.0 6 8.1 65.9 6 43.8†
3,992.1 6 2,669.4 4,314.9 6 3,752.5
5,297.7 6 4,258 2,975 6 2,465
3,281.7 6 1,259.0 3,084.6 6 2,619.7
2,411.7 6 1,348.6 2,893.9 6 1,839.4
2,082.38 6 1,028 2,625.88 6 1,647
1,533 6 1,144.7 3,165.5 6 3,543.4
1,040.2 6 721.2 1,207.2 6 1,227.3
1,357.63 6 1,081 1,180.7 6 1,248
1,427.1 6 1,239.1 2,600.2 6 2,769.1
2.84 6 1.6 4.89 6 3.5
1.9 6 1.1 3.4 6 3.1
1.4 6 1.4 2.3 6 2.2
*HAT = intermittent protocol with large amplitude; LAT = intermittent protocol with average amplitude; CT = continuous protocol; RMSSD = root mean square of successive differences squared; LF = low frequency; HF = high frequency. †Statistically different from posttraining, in the same effort protocol, p , 0.001.
RESULTS Regarding RPE, among the training types, there was a difference in the posttraining results between HAT and LAT (9.2 6 1.2 and 4.5 6 1.3 au, respectively; p , 0.001) and between HAT and CT (3.7 6 1.1 au; p , 0.001). Regarding the cardiovascular demands, there was a significant increase in mean HR from pretraining (HAT: 80.5 6 10.3 b$min21; LAT: 80.1 6 7.9 b$min21; CT: 79.2 6 8.5 b$min21) to posttraining (HAT: 139.4 6 12.7 b$min21; LAT: 135 6 10.8 b$min21; CT: 120.2 6 10.9 b$min21), and this returned to the resting levels after 24 hours (HAT: 79.6 6 14.2 b$min21; LAT: 78.5 6 10.7 b$min21; CT: 75.6 6 16.3 b$min21); pretraining and 24 hours after training
showed a significant difference in relation to posttraining (p , 0.001). Between sessions, HAT showed higher mean HR in comparison to CT in the posttraining measurements (HAT: 139.4 6 12.7 b$min21 and CT: 120.2 6 10.9 b$min21; p = 0.01). Maximum HR significantly increase from the pretraining (HAT: 106.63 6 9.55 b$min21; LAT: 106.88 6 4.45 b$min21; CT: 106.63 6 15.6 b$min21) to the posttraining (HAT: 196.5 6 7.13 b$min21; LAT: 189 6 9.72 b$min21; CT: 175.63 6 11.12 b$min21) and returned to the resting values after 24 hours (HAT: 103 6 12.26 b$min21; LAT: 101.5 6 8.7 b$min21; CT: 99.25 6 15.61 b$min21); pretraining and 24 hours after training showed a significant difference in relation to posttraining (p , 0.001). Additionally, a difference was found between
TABLE 3. Correlation values, magnitude and significance level between variables.* Variables Effort spm and RPE posttraining Effort spm and maximum HR posttraining Effort spm and mean HR posttraining RPE and maximum HR posttraining RPE and mean HR posttraining RPE and RMSSD posttraining RPE and HF posttraining RPE and LF posttraining
Correlation value
R2
Magnitude
p
0.80 0.80 0.57 0.61 0.53 20.53 20.47 20.45
0.64 0.64 0.32 0.37 0.28 0.28 0.22 0.20
Large Large Moderate Moderate Moderate Moderate Small Small
,0.001 ,0.001 0.003 0.001 0.007 0.006 0.02 0.02
*RPE = rate of perceived exertion; spm = stroke per minute; HR = heart rate; LF = low frequency; HF = high frequency; RMSSD = root mean square of successive differences squared.
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Journal of Strength and Conditioning Research HAT and CT in the posttraining HR (196.5 6 7.13 b$min21 and 175.63 6 11.12 b$min21, respectively; p # 0.05). The results of HRV in the time (pretraining, posttraining, and post-24 hours) and frequency (only the rest moments: pretraining and post-24 hours) domains are shown in Table 2. There were no significant differences between the rest moments for any variable in the 3 protocols or between protocols at the same collecting moment. Some significant correlations between stroke and RPE were found, which are presented in Table 3. There were significant correlations (r = 0.80, p , 0.001) with large magnitude between both: effort stroke and RPE and effort stroke and maximum HR.
DISCUSSION The purpose of this study was to investigate the ANS recovery and RPE as a result of different training amplitudes in young rowers. The main finding was the differences in the HRV time domain variable from pretraining and 24 hours after training in comparison with the posttraining moment of the same session, thus representing the impact promoted by different types of training on the ANS and its complete recovery after 24 hours. In this study, the higher RPE recorded at the HAT posttraining in comparison with the other 2 protocols is directly related to the load used (17,19), which is reinforced by the high correlation coefficient found between training RPE and stroke (r = 0.80, p , 0.001). Additionally, it is relevant to point out that the larger the amplitude, the more marked was the difference in RPE. A significant relationship between RPE and physiological variables also were evident (27). It is interesting that the correlation between HR and RPE was only moderate, whereas the relation between stroke per minute and RPE posttraining was strong (Table 3). From the cardiovascular viewpoint, the difference found for maximum HR immediate posttraining between HAT and CT indicates the larger instantaneous impact of the interval training stimulus, with great effort load compared with the CT (4). This can be associated with the large sympathetic nervous system activation from harder stimulus (HAT) that influences their recovery process (6,17). In addition, the correlation between HR and stroke and between HR and RPE demonstrates the influence of training load on increased HR, which can be explained by the increase in effort intensity to generate increased HR and, consequently, greater RPE (7,27). Regarding HR, the post-24-hour record values was found to return to the levels close to those found for pretraining resting measures. Thus, considering HR, the recovery time may be demonstrated to be appropriate between training sessions for the HR recovery, regardless of whether efforts were conducted continuously or using intervals (1,29). This fast HR recovery in young athletes can be due to different mechanisms, such as the greater parasympathetic efferent nervous activity to the heart, the relatively lower contribution of cardiac sympathetic nervous activity in comparison with adults, and a smaller exercise-induced increase in catecholamine activity (26).
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Heart rate variability has been used as a noninvasive indicator of stress induced by exercise and consequent impairment to the autonomic cardiac modulation (2,33) in endurance activities with different intensities and durations (16,17,29). In this study, HRV reduction during the application of training with great amplitudes was shown, indicating that efforts with higher loads are sufficient to promote changes in relation to the rest; i.e., modifications in the sympathetic and parasympathetic activity relation may be dependent on the exercise intensity (2). Although the CT at lower intensities can be interesting for technical improvement in cyclical modalities (28), the highintensity efforts made in the HIIT sessions promote greater organic impact. The combination of these types of exercise, such as in polarized training programs, seems to be the best model for the endurance athletes’ conditioning (12,15,28,30). Similar to HR, the HRV parameter that was changed significantly after the training sessions had the values returned to basal levels after 24 hours, regardless of the type of workout. This also occurred in another study that evaluated the same variable, i.e., a significant decrease of the ANS parasympathetic contribution to cardiac activity (8). In this context, even with different amplitude loads, all protocols affect cardiac control by the ANS (29). A study limitation was the absence of a stroke counter in the boat during the trainings is pointed out. The stroke counter was not used in the boat during training because it has magnets that could interfere with the HR monitor data transmission and distort the HR and HRV results. To overcome this limitation, the evaluators used a manual stroke counter for cadence control during all training sessions, which is a strategy that is widely used in training prescription to control rowing rhythm. Additionally, our study used 3 isolated training sessions of 10 minutes, and future investigations can apply longer stimulus, with accumulated sessions in subsequent days. From the results, it can be concluded that the immediate impact promoted by the HAT on maximum HR and RPE was superior to the CT protocol when using a large interval load (100%). Regarding the HRV time domain variable, a statistically significant difference of the resting moments (pretraining or after 24 hours) in relation to posttraining in all the protocols was identified, signaling that the younger rowers were recovered from the ANS viewpoint between training sessions. Furthermore, there is a strong and significant correlation between RPE posttraining and effort intensity (spm), as well as between effort intensity (spm) and maximum HR after training.
PRACTICAL APPLICATIONS Coaches can consider training programs with the use of the polarized training logic, observing the stimulus nature and time required for recovery. Training sessions at lower intensities may be interesting to improve technique together with physical fitness development, with lower HR stress than interval with large amplitude, whereas 24 hours of rest are VOLUME 28 | NUMBER 10 | OCTOBER 2014 |
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Different Training Amplitudes in Young Rowers sufficient to recover from interval training with high intensities in young rowers. However, to complement this information and to have appropriate planning, data about other physiological variables should be sought, considering the cumulative effects of these training loads in rowing. The application of this study with different training protocols in water provides greater specificity in relation to the rowing training demands.
15. Ingham, SA, Carter, H, Whyte, GP, and Doust, JH. Physiological and performance effects of low-versus mixed-intensity rowing training. Med Sci Sports Exerc 40: 579–584, 2008.
ACKNOWLEDGMENTS
18. Karapetian, GK, Engel, HJ, Gretebeck, KA, and Gretebeck, RJ. Effect of caffeine on LT, VT and HRVT. Int J Sports Med 33: 507– 513, 2012.
The authors would like to thank the coach Oguener Tissot, from “Academia de Remo Tissot,” for his involvement and concessions of boats and materials required in the data collection process, and the rowers, for their dedication to training and the testing stipulated.
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AND
ON
FABRI´CIO B. DEL VECCHIO
Superior School of Physical Education, Federal University of Pelotas, Brazil ABSTRACT Vaz, MS, Picanc¸o, LM, and Del Vecchio, FB. Effects of different training amplitudes on heart rate and heart rate variability in young rowers. J Strength Cond Res 28(10): 2967–2972, 2014—The aim of this study was to investigate the autonomic nervous system recovery and the psychological response as a result of 3 training amplitudes on heart rate (HR), heart rate variability (HRV), and rate of perceived exertion (RPE) in rowing. Eight young rowers (16.8 6 1.4 years) performed, in a randomized fashion, 2 sessions of highintensity interval training, with high and low amplitude and a continuous training (CT) session, with the same exercise duration (10 minutes) and mean intensity (60% of maximal stroke test). The data of HR, HRV, and RPE were collected 5 minutes before, immediately after each session, and 24 hours later. High amplitude promoted higher impact in maximum HR (p # 0.05) and RPE (p , 0.001) when compared with CT. For the time domain HRV variable, there was a statistically significant difference between moments of rest (pretraining or post 24 hours) and posttraining in all training sessions. Originally, we conclude that training with higher load variation between effort and recovery impacts HRV, HR, and RPE with greater intensity, but the younger rowers were ready for new training sessions 24 hours after either training method. Coaches can use the polarized training method, observing the stimulus nature and time required for recovery, because it may be an adequate strategy for the development of rower’s conditioning.
KEY WORDS athletes, autonomic nervous system, physical fitness, rate of perceived exertion
Address correspondence to Marcelo dos Santos Vaz, marcelo.dsvaz@ gmail.com. 28(10)/2967–2972 Journal of Strength and Conditioning Research Ó 2014 National Strength and Conditioning Association
INTRODUCTION
I
n rowing, the training commonly applied is characterized with low intensity and long duration (15,23), especially, because the competitions are conducted in 2,000-m races, which lasts from 6 to 8 minutes, and the aerobic metabolism is predominant, with a contribution of 87 6 2% (21). Furthermore, recent studies have found that high-intensity interval training (HIIT) is an adequate method for the improvement of physical fitness components required in rowing (9,12). For the HIIT program organization, different variables need to be manipulated at the same time (7). Studies frequently evaluate the effects of different effort intensities and recovery (15–17). However, the amplitude, which is characterized by the magnitude of variation between effort and rest, allows prescriptions of training with distinct effort-pause ratios, but with equal mean intensity. Although this is an important tool in the control of training load (3,4), it has been poorly investigated. Parameterizing the training sessions by the mean intensity may be interesting to handle the training load over an entire period (12). Until recently, most HIIT protocols have adopted the strategy of manipulating the duration and intensity as load components; only lately has the amplitude been studied (3,4). In this context, 2 training protocols were matched for the duration, mean intensity, and covered distance but with different amplitudes (0 and ;30%), and the authors found no differences between the protocols for heart rate (HR), RPE, and blood lactate concentration during exercise (3). In another case, researchers who studied 3 types of training over the same distance covered but with different intensities and effort duration noted that the protocols with greater variation between effort and pause were those that produced the greatest impact on the autonomic nervous system (ANS), obtaining statistically significant correlations between RPE and HR using the heart rate variability (HRV) parameters (17). In this context, some HRV components have been associated with organic overload (17), and that also could contribute to the process of training load control by assessing day after day the HRV data in different moments as pretraining, immediate posttraining, and after 24 hours (22,24). When studied with constant load exercises and with VOLUME 28 | NUMBER 10 | OCTOBER 2014 |
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Different Training Amplitudes in Young Rowers interval exercises, HRV showed a delay in the recovery after the HIIT exercises (17). In relation to HIIT, other studies have explored how this type of exercise affects activity of the ANS, which can be inferred by HRV (28,30). Additionally, the manipulation of the stimuli duration and intensity and its relation to HRV were studied in endurancetrained adults, and the results indicated that the posttraining HRV data may offer important information about the training load in different durations and intensities of HIIT (17); however, no information has been provided regarding how the ANS responds acutely and 24 hours after to amplitude manipulation (4,13), especially considering similar mean intensities. The amplitude allows comparing different training protocols with the same mean intensity and different effort and recovery loads. In this sense, low and average amplitudes can promote similar impacts on metabolic and performance variables (10), and the coaches can choose the better training stimulus considering this information. Moreover, these data could help in the prescription of the training, especially an HIIT approach, which does not have a gold standard for the training load measurement. Thus, the objective of this study was to investigate the ANS recovery and rating of perceived effort (RPE) as a result of 3 training amplitudes (0, 50, and 100%) in young rowers.
METHODS Experimental Approach to the Problem
This is a counterbalanced experimental study with repeated measures. The training amplitude was considered as the independent variable, and rate of perceived exertion (RPE), HR, and HRV parameters were considered as the dependent variables.
Figure 1.
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The study consisted of 4 different sessions, separated by 48 hours. In the first session, an anamnesis was obtained, and the maximum stroke test was performed. In the 3 subsequent sessions, training with different amplitudes was conducted, with the execution order determined randomly (Figure 1). The rowers performed 3 training sessions with the execution order determined randomly, using the same exercise duration (10 minutes) and matched average intensity; this was calculated from the sum of effort and pause intensities divided by two. The detail that distinguished the 3 protocols was the amplitude of effort-pause ratio (Figure 2), i.e., the ratio of the difference between exercise intensity and the average intensity divided by the average intensity (4). The idea of equating the training sessions by time and intensity was to isolate the amplitude as the only variable that distinguished the protocols, enabling the comparison and assuming the amplitude as the main reason of the different impact in the dependent variables. Subjects
Eight young male rowers, free of injuries with at least 1 year of practice in the sport, were involved in the study; the participants were selected by convenience from the only amateur club of the city. All rowers and their parents signed a consent form of participation, which was approved by the local ethics committee (protocol 005/2012). The subjects were 16.8 6 1.4 years old (15–19 years), 180 6 7 cm tall, and had a body mass of 71.3 6 12.6 kg. Maximal Stroke Test
To estimate the maximum stroke (Smax) in strokes per minute (spm), a progressive maximum test was conducted with a Single Skiff (Canoe Simples; Holos, Brazil) equipped with a stroke counter (Speed Coach Gold; NK, Boothwyn, PA, USA). The evaluation procedure consisted of a 5-minute warm-up that was intensity and cadence free. Immediately after, the test began with a cadence of 14 spm. Each stage lasted for 2 minutes with 30-second interval between them (29). After each stage was completed, an increase of 2 spm was applied, and the test was ended when the rower could not complete the stage. As a parameter for interruption, the inability to sustain the pace of the stage for more than 5 strokes was considered. During testing, the evaluators followed the rowers with a motorized boat and used a counter stroke (Interval 2000; NK) to maintain the cadence control. In the maximal stroke Experimental design. HR = heart rate; RPE = rate of perceived exertion; HRV = heart rate variability. test, a frequency of 24.71 6 1.36 spm was obtained. the
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average intensity remained at 60% (120:0), but the amplitude was 100%. Data Collection Figure 2. Amplitude equation.
Training Session Procedures
The training sessions involved a continuous training (CT) and 2 interval training, one with low (LAT) and another with high amplitude (HAT), which are presented in Table 1 and described below. For all training sessions, the subjects were instructed to sleep adequately (8 hours at minimum), have a habitual breakfast, not perform vigorous exercise in the 24 hours preceding assessment, and avoid ingesting caffeine, which modifies different HRV parameters (18). Continuous Training
Continuous training was composed of a constant stimulus with an intensity of 60% Smax obtained in the maximal stroke test. The athletes rowed uninterruptedly for 10 minutes. The effort in the CT was 14.85 6 1.56 spm. Interval Training With Low Amplitude
Low amplitude was structured with 5 effort-pause blocks with a 1:1 ratio. During efforts lasting 60 seconds, the intensity was 90% Smax; during active recovery, which was also a period of 60 seconds, the intensity was 30% Smax. The LAT effort-pause ratio was 22.8 6 2.3:7.4 6 0.8 spm. Although the average intensity was fixed at 60% (90:30) of Smax, the training amplitude was 50%. Interval Training With High Amplitude
High amplitude was composed of 10 effort-pause blocks with the same ratio of LAT (1:1) but with an intensity of 120% Smax during the 60 seconds of effort and passive recovery during the 60-second pause. The effort-pause ratio in the HAT was 29.7 6 2.6:0 spm. In this case, the
and Recording
For each subject, HR monitoring was recorded for 5 minutes before and 5 minutes after the end of each session (acute response) and during 5 minutes 24 hours after training (considered a delayed response). The period of 300 seconds is considered valid and sufficient for obtaining the adequate information about HRV variables (14). The pretraining and posttraining data recordings were conducted with the subject seated and immobile in the boat, and after 24 hours, the data were collected with the subjects sitting on the floor to simulate the position taken in the boat. The HRV parameters, properly registered with validated procedures and equipment for data filtering (25), were organized into 2 domains: time and frequency (11). For the time domain, the root mean square of successive differences squared was collected and analyzed. In the frequency domain, spectral components were assessed: (a) very low frequency: 0–0.04 Hz, (b) low frequency: 0.04–0.15 Hz (LF), (c) high frequency: 0.15–0.4 (HF), and (d) the LF/HF ratio (16). The HR and HRV data were collected with an HR monitor (Polar RS800CX; Polar Electro OY, Kempele, Finland), transferred to the Polar ProTrainer 5 software, and analyzed using the software Kubios HRV 2.0 (University of Kuopio, Finland). For HR, we considered the average values of HR across the test interval and maximum HR as the highest at any given point in the collection. The RPE information was collected with the Borg scale (0–10) (5) after the end of each session and is shown as arbitrary units (au). Statistical Analyses
Data analysis was performed using the software OriginPro 8.5. For descriptive presentation, the mean and SD were used. Mauchly’s test was used to test the data sphericity, and the Greenhouse-Geisser correction TABLE 1. General characteristics of continuous and interval training sessions.* was used when appropriate CT LAT HAT (20). We conducted 2-way analysis of variance (ANOVA), trainTotal duration of exercise (min) 10 10 10 Effort: pause ratio NA 1:1 1:1 ing type and time of analysis, Effort intensity (% Smax) 60 90 120 with repeated measures over Pause intensity (% Smax) NA 30 0 the second factor. When signifiAverage training intensity (% Smax) 60 60 60 cance was detected by ANOVA, Training amplitude (%) 0 50 100 we used the Bonferroni test to Total duration of session (min) 10 10 20 identify differences. For the cor*CT = continuous protocol; LAT = intermittent protocol with average amplitude; HAT = relations between variables of intermittent protocol with large amplitude; % Smax = percentage of maximum intensity interest, we used the Pearson’s reached in the test; NA = not applicable. test. The statistically significant level was set at 5%. VOLUME 28 | NUMBER 10 | OCTOBER 2014 |
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Different Training Amplitudes in Young Rowers
TABLE 2. Mean 6 SD from HRV time and frequency domains parameters.* HAT RMSSD (ms) Pretraining Posttraining Post-24 h VLF (ms2) Pretraining Post-24 h LF (ms2) Pretraining Post-24 h HF (ms2) Pretraining Post-24 h LF/HF (%) Pretraining Post-24 h
LAT
47.7 6 21.3† 4.2 6 1.4 53.1 6 28.9†
CT
54.3 6 22.9† 9.9 6 7.4 48.5 6 24.1†
55.98 6 2† 11.0 6 8.1 65.9 6 43.8†
3,992.1 6 2,669.4 4,314.9 6 3,752.5
5,297.7 6 4,258 2,975 6 2,465
3,281.7 6 1,259.0 3,084.6 6 2,619.7
2,411.7 6 1,348.6 2,893.9 6 1,839.4
2,082.38 6 1,028 2,625.88 6 1,647
1,533 6 1,144.7 3,165.5 6 3,543.4
1,040.2 6 721.2 1,207.2 6 1,227.3
1,357.63 6 1,081 1,180.7 6 1,248
1,427.1 6 1,239.1 2,600.2 6 2,769.1
2.84 6 1.6 4.89 6 3.5
1.9 6 1.1 3.4 6 3.1
1.4 6 1.4 2.3 6 2.2
*HAT = intermittent protocol with large amplitude; LAT = intermittent protocol with average amplitude; CT = continuous protocol; RMSSD = root mean square of successive differences squared; LF = low frequency; HF = high frequency. †Statistically different from posttraining, in the same effort protocol, p , 0.001.
RESULTS Regarding RPE, among the training types, there was a difference in the posttraining results between HAT and LAT (9.2 6 1.2 and 4.5 6 1.3 au, respectively; p , 0.001) and between HAT and CT (3.7 6 1.1 au; p , 0.001). Regarding the cardiovascular demands, there was a significant increase in mean HR from pretraining (HAT: 80.5 6 10.3 b$min21; LAT: 80.1 6 7.9 b$min21; CT: 79.2 6 8.5 b$min21) to posttraining (HAT: 139.4 6 12.7 b$min21; LAT: 135 6 10.8 b$min21; CT: 120.2 6 10.9 b$min21), and this returned to the resting levels after 24 hours (HAT: 79.6 6 14.2 b$min21; LAT: 78.5 6 10.7 b$min21; CT: 75.6 6 16.3 b$min21); pretraining and 24 hours after training
showed a significant difference in relation to posttraining (p , 0.001). Between sessions, HAT showed higher mean HR in comparison to CT in the posttraining measurements (HAT: 139.4 6 12.7 b$min21 and CT: 120.2 6 10.9 b$min21; p = 0.01). Maximum HR significantly increase from the pretraining (HAT: 106.63 6 9.55 b$min21; LAT: 106.88 6 4.45 b$min21; CT: 106.63 6 15.6 b$min21) to the posttraining (HAT: 196.5 6 7.13 b$min21; LAT: 189 6 9.72 b$min21; CT: 175.63 6 11.12 b$min21) and returned to the resting values after 24 hours (HAT: 103 6 12.26 b$min21; LAT: 101.5 6 8.7 b$min21; CT: 99.25 6 15.61 b$min21); pretraining and 24 hours after training showed a significant difference in relation to posttraining (p , 0.001). Additionally, a difference was found between
TABLE 3. Correlation values, magnitude and significance level between variables.* Variables Effort spm and RPE posttraining Effort spm and maximum HR posttraining Effort spm and mean HR posttraining RPE and maximum HR posttraining RPE and mean HR posttraining RPE and RMSSD posttraining RPE and HF posttraining RPE and LF posttraining
Correlation value
R2
Magnitude
p
0.80 0.80 0.57 0.61 0.53 20.53 20.47 20.45
0.64 0.64 0.32 0.37 0.28 0.28 0.22 0.20
Large Large Moderate Moderate Moderate Moderate Small Small
,0.001 ,0.001 0.003 0.001 0.007 0.006 0.02 0.02
*RPE = rate of perceived exertion; spm = stroke per minute; HR = heart rate; LF = low frequency; HF = high frequency; RMSSD = root mean square of successive differences squared.
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Journal of Strength and Conditioning Research HAT and CT in the posttraining HR (196.5 6 7.13 b$min21 and 175.63 6 11.12 b$min21, respectively; p # 0.05). The results of HRV in the time (pretraining, posttraining, and post-24 hours) and frequency (only the rest moments: pretraining and post-24 hours) domains are shown in Table 2. There were no significant differences between the rest moments for any variable in the 3 protocols or between protocols at the same collecting moment. Some significant correlations between stroke and RPE were found, which are presented in Table 3. There were significant correlations (r = 0.80, p , 0.001) with large magnitude between both: effort stroke and RPE and effort stroke and maximum HR.
DISCUSSION The purpose of this study was to investigate the ANS recovery and RPE as a result of different training amplitudes in young rowers. The main finding was the differences in the HRV time domain variable from pretraining and 24 hours after training in comparison with the posttraining moment of the same session, thus representing the impact promoted by different types of training on the ANS and its complete recovery after 24 hours. In this study, the higher RPE recorded at the HAT posttraining in comparison with the other 2 protocols is directly related to the load used (17,19), which is reinforced by the high correlation coefficient found between training RPE and stroke (r = 0.80, p , 0.001). Additionally, it is relevant to point out that the larger the amplitude, the more marked was the difference in RPE. A significant relationship between RPE and physiological variables also were evident (27). It is interesting that the correlation between HR and RPE was only moderate, whereas the relation between stroke per minute and RPE posttraining was strong (Table 3). From the cardiovascular viewpoint, the difference found for maximum HR immediate posttraining between HAT and CT indicates the larger instantaneous impact of the interval training stimulus, with great effort load compared with the CT (4). This can be associated with the large sympathetic nervous system activation from harder stimulus (HAT) that influences their recovery process (6,17). In addition, the correlation between HR and stroke and between HR and RPE demonstrates the influence of training load on increased HR, which can be explained by the increase in effort intensity to generate increased HR and, consequently, greater RPE (7,27). Regarding HR, the post-24-hour record values was found to return to the levels close to those found for pretraining resting measures. Thus, considering HR, the recovery time may be demonstrated to be appropriate between training sessions for the HR recovery, regardless of whether efforts were conducted continuously or using intervals (1,29). This fast HR recovery in young athletes can be due to different mechanisms, such as the greater parasympathetic efferent nervous activity to the heart, the relatively lower contribution of cardiac sympathetic nervous activity in comparison with adults, and a smaller exercise-induced increase in catecholamine activity (26).
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Heart rate variability has been used as a noninvasive indicator of stress induced by exercise and consequent impairment to the autonomic cardiac modulation (2,33) in endurance activities with different intensities and durations (16,17,29). In this study, HRV reduction during the application of training with great amplitudes was shown, indicating that efforts with higher loads are sufficient to promote changes in relation to the rest; i.e., modifications in the sympathetic and parasympathetic activity relation may be dependent on the exercise intensity (2). Although the CT at lower intensities can be interesting for technical improvement in cyclical modalities (28), the highintensity efforts made in the HIIT sessions promote greater organic impact. The combination of these types of exercise, such as in polarized training programs, seems to be the best model for the endurance athletes’ conditioning (12,15,28,30). Similar to HR, the HRV parameter that was changed significantly after the training sessions had the values returned to basal levels after 24 hours, regardless of the type of workout. This also occurred in another study that evaluated the same variable, i.e., a significant decrease of the ANS parasympathetic contribution to cardiac activity (8). In this context, even with different amplitude loads, all protocols affect cardiac control by the ANS (29). A study limitation was the absence of a stroke counter in the boat during the trainings is pointed out. The stroke counter was not used in the boat during training because it has magnets that could interfere with the HR monitor data transmission and distort the HR and HRV results. To overcome this limitation, the evaluators used a manual stroke counter for cadence control during all training sessions, which is a strategy that is widely used in training prescription to control rowing rhythm. Additionally, our study used 3 isolated training sessions of 10 minutes, and future investigations can apply longer stimulus, with accumulated sessions in subsequent days. From the results, it can be concluded that the immediate impact promoted by the HAT on maximum HR and RPE was superior to the CT protocol when using a large interval load (100%). Regarding the HRV time domain variable, a statistically significant difference of the resting moments (pretraining or after 24 hours) in relation to posttraining in all the protocols was identified, signaling that the younger rowers were recovered from the ANS viewpoint between training sessions. Furthermore, there is a strong and significant correlation between RPE posttraining and effort intensity (spm), as well as between effort intensity (spm) and maximum HR after training.
PRACTICAL APPLICATIONS Coaches can consider training programs with the use of the polarized training logic, observing the stimulus nature and time required for recovery. Training sessions at lower intensities may be interesting to improve technique together with physical fitness development, with lower HR stress than interval with large amplitude, whereas 24 hours of rest are VOLUME 28 | NUMBER 10 | OCTOBER 2014 |
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Different Training Amplitudes in Young Rowers sufficient to recover from interval training with high intensities in young rowers. However, to complement this information and to have appropriate planning, data about other physiological variables should be sought, considering the cumulative effects of these training loads in rowing. The application of this study with different training protocols in water provides greater specificity in relation to the rowing training demands.
15. Ingham, SA, Carter, H, Whyte, GP, and Doust, JH. Physiological and performance effects of low-versus mixed-intensity rowing training. Med Sci Sports Exerc 40: 579–584, 2008.
ACKNOWLEDGMENTS
18. Karapetian, GK, Engel, HJ, Gretebeck, KA, and Gretebeck, RJ. Effect of caffeine on LT, VT and HRVT. Int J Sports Med 33: 507– 513, 2012.
The authors would like to thank the coach Oguener Tissot, from “Academia de Remo Tissot,” for his involvement and concessions of boats and materials required in the data collection process, and the rowers, for their dedication to training and the testing stipulated.
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