Pediatric Exercise Science, 2015, 27, 185 -191 http://dx.doi.org/10.1123/pes.2014-0094 © 2015 Human Kinetics, Inc.
ORIGINAL RESEARCH
Left Ventricular Morphology in Different Periods of the Training Season in Elite Young Swimmers Eszter Csajági Semmelweis University
Ipoly Szauder Cardiologic Diagnostic Center
Zsuzsanna Major Semmelweis University
Gábor Pavlik Semmelweis University Training adaptation of the left ventricle (LV) and it’s reversibility following the cessation of training in adults is well known and also studied in children. In the current study we describe the changes in the LV morphology in association with the training season during a 1.5 year follow-up period. 15 elite adolescent swimmers, seven girls and 8 boys with 6 years of swimming history and 20 hr per week training were observed. Their data were compared with 15 age and gender matched nonathletes. LV adaptation was measured with 2D-echocardiography at the baseline preseason and every 3 months, according to the macro cyclic periods of training. Nonathletes were observed at the first and fifth stage of the study. Remarkable LV morphological adaptation has been detected in the swimmers. The greatest LV muscle mass (LVMM: 228 ± 46g) and smallest end-diastolic diameter (LVIDd:44.9 ± 3.4mm) were observed at the end of the second general endurance preparation period (GEP2), but the LVMM/BSA3/2 (Rel.LVMM: 85 ± 10g/m) failed to change during the follow-up in athletes. On the basis of our results, we suggest comparing absolute LV dimensions only in studies made at the same training period to avoid bias due to alterations with the training season. Keywords: athlete’s heart, young swimmer, echocardiography, seasonal change, left ventricle In the past decades athlete’s heart has been the focus of attention in sport medicine and cardiology. Several reviews were published indicating a slightly concentric type of left ventricular (LV) hypertrophy in adult athletes (18,19,24,30) and showing an eccentric type of hypertrophy at an early stage in young athletes (7,8,13,16–20,29,30). Physiologic cardiac adaptation is known to be reversible with the cessation of training (6,14). Also recent studies suggest that characteristics of the athlete’s heart are not constant, they may change with the actual fitness level of the athletes (5,8,21). Therefore, it can be postulated that the characteristics of the athlete’s Csajági, Major, and Pavlik are with the Dept. of Health Sciences and Sports Medicine, Semmelweis University, Budapest, Hungary. Szauder is with the Cardiologic Diagnostic Center, Budapest, Hungary. Address author correspondence to Eszter Csajági at [email protected].
heart might change during the different phases of the yearly training period as well (2,5,25,26). Moreover, athletic characteristics including cardiac adaptation are expected to change more quickly in the early years; hence, seasonal variations can be expected to be more prominent in children than in adults. In younger athletes physiologic maturation also has to be considered in the development of the characteristics of the athlete’s heart. In some previous studies authors found increased LV dimensions in the active period of the yearly training program: Smith et al. (25) found thicker LV wall in wrestlers, D’Ascenzi et al. (5) and Cabanelas et al. (2) greater LV muscle mass (LVMM) in elite soccer players. On the other hand Snoeckx et al. (26) in runners and cyclists and Randers et al. (21) in elite female football players found no differences among parameters measured in the different phases of the training program. Data in young athletes are limited: Hansen et al. (8) reported a thicker LV posterior wall (LVPW) after 3 months of
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soccer training in overweight children. The Muscatine Study (10) described the dynamics of the heart development in puberty in healthy individuals. Evaluating the seasonal changes in the characteristics of the athlete’s heart can be a reliable way to characterize the athlete’s physical condition, especially the endurance ability (4). Also interindividual differences in the adaptation to training can be observed (4). The present study aimed to investigate the seasonal variations in the morphological characteristics of the athlete’s heart in young swimmers to better understand the physiologic cardiac adaptation in the young.
Subjects and Methods
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Subjects 18 top-level young swimmers were invited to participate in the study. All of them were members of the same leading swimming club, and invited to the national team in their age category (13–15 yrs). Children performed regular training for at least the last 4 years, for an average of more than 20 hr per week (Table 1.). Seven girls and 8 boys completed the 1.5-year observational period, 2 girls and 1 boy stopped participation before completion of observational period. In the first and fifth stage of the study their results were compared with healthy, nontrained, age and gender matched nonathletes (Table 1.). This comparison aimed to differentiate between training effect and physiological development. Subjects who didn’t show adequate compliance or had any disorders that would preclude training eligibility were excluded from the study (3). All participants and parents gave written consent to the study, which was approved by the Regional and Institutional Committee of Science and Research Ethics of the university (TUKEB Nr: 121/2010). Basic anthropometric data and training history are presented in Table 1.
Methods The longitudinal study contained 6 follow-up examinations during 18 months adjusted to the macro and micro cyclic variations in the training period: every 3 month in the preseason baseline (S), at the end of the general endurance preparation period 1 (GEP1), in the race specific training period 1 (RP1), after detraining (DT), at the end of the general endurance preparation period 2 (GEP2), and in the race specific training period 2 (RP2). At baseline a questionnaire used in sport medicine was completed with parental guide documenting the training habits and history, medical and family history. Blood pressure, body height, and weight were measured followed by physical examination and a 12-lead ECG (Innomed Heart Screen, Budapest, Hungary). Sexual maturation was judged according to the recommendations of Janz et al. (10). 2D-, Doppler-, and TDI echocardiography was carried out with a Philips HD15 Echocardiograph (1–5 MHz, Koninkiljke Philips, NV, USA) according to the standards of the American Society of Echocardiography
(11) in the steep left lateral decubitus position. Followup examinations have been performed every third month (8,10,21). All examinations were carried out by the same physician. Nonathletic children were examined according to the timing of the first (S) and fifth (GEP2) occasion. Echocardiography examinations were analyzed offline. Each parameter was estimated on 3–5 heart cycles to minimize intraobserver variability. The averages were used in the further analysis. Heart rate (HR) was measured on the Doppler echocardiographic curves. From the parasternal 2D-guided M mode recordings, the following data were acquired: LV end diastolic septal (IVSd) and posterior wall thickness (LVPWTd), and LV end diastolic (LVIDd) and end systolic (LVIDs) dimensions. Meanwhile, the left ventricular long axis (LVLA) in systole and diastole were obtained from the apical 4-chamber view. Relative values were referred to the indexed BSA: so that the nominator and the denominator have the same power (13,19,20). Calculated values were the LVMM according to the ASE recommendations (11). Statistical analysis was carried out with Statistica for Windows 11.0 (Stat Soft, Tulsa, OK, USA). Distribution of the parameters was tested with the Shapiro-Wilks test. Data of nonathletes were compared with Wilcoxon test, data of athletes with repeated measure or Friedmann ANOVA and post hoc tests. Level of significance was set at 5%.
Results Anthropometric Parameters and Basic Echocardiographic Data Athletes: changes in height followed the normal development predicted by the age and appeared parallel in boys and girls, but no difference was observed between genders (Table 1). Weight was developing nearly the same way. No differences in the resting heart rate (HR): boys: 63 ± 9 bpm; girls: 57 ± 4 bpm and in the blood pressure values systolic (BPS): boys: 112.5 ± 2.7 mmHg; girls: 111.2 ± 11.7 mmHg; diastolic (BPD): boys: 67.5 ± 2.7 mmHg, girls: 67.5 ± 5.2 mmHg were observed with the training season or between the genders. The nonathletic group was age and gender matched. There was no difference in the height, weight and resting BP values and sexual maturation. Swimmer girls had lower HR than controls (Table 1).
Left Ventricular Morphological Changes with the Training Season Changes in the absolute and indexed (values are indexed to the BSA1/2 for LVWT and dimensions and BSA3/2 for the LVMM) parameters describing the left ventricular morphology are presented in Table 2 for boys and Table 3 for girls. Differences are shown in the last columns, when significant. Figure 1 indicates the seasonal changes in LVMM. The greatest LVMM and smallest LVIDd were detected in GEP2, but the Rel.LVMM didn’t change during the follow-up in athletes.
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Table 1 Basic Anthropometric Data and Training History Athletes
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Characteristics Age (y) Height (m) Weight (kg) HR (1/min) BPS (mmHg) BPD (mmHg) Training history (y) Training (hr/week) Sexual maturation
Boys 13.8 ± 0.7 1.66 ± 0.07 50.8 ± 6.4 63 ± 9 112.5 ± 2.7 67.5 ± 2.7 6.4 ± 1.4 23.2 ± 4.1 2.87 (1–4)
Girls 13.8 ± 0.9 1.67 ± 0.08 54.8 ± 8.8 57 ± 4 111.2 ± 11.7 67.5 ± 5.2 5.9 ± 1.7 20.3 ± 5.5 3.3 (3–4)
Nonathletes Boys Girls 13.8 ± 0.7 13.8 ± 0.9 1.60 ± 0.12 1.63 ± 0.06 49.8 ± 10.7 55.3 ± 6.2 69 ± 12 75 ± 11 120.0 ± 7.0 121.4 ± 11.1 64.4 ± 6.8 67.1 ± 9.1 0.28 (0–1) 0.23 (0–0.6) 3 (1–4) 3.6 (2–5)
Note. Sexual maturation was judged on a 5 point scale: 1: pre, 2: early-, 3: mid, 4: late-, 5: post puberty. Values are shown as mean ± SD for normal distribution parameters and median with minimum and maximum for nonnormal distribution. Significant difference between athletic and nonathletic group are marked bold. HR = heart rate; BPS = systolic blood pressure; BPD = diastolic blood pressure.
Figure 1 — Changes in the LVMM with the training season. LVMM = left ventricular muscle mass; S = starting preseason value; GEP1,2 = general endurance preparation period 1,2; RP1, 2 = race-specific training period 1,2; DT = detraining (DT). Level of significance: *p < .05, ***p < .001. Values are presented as mean ± SD.
Differences Between the Athletes and Nonathletes Differences between the athletic and nonathletic children are presented in Table 4. Even in the starting values marked differences were observed in the absolute and relative wall thickness and the LVMM between the two groups in both genders. The difference was even more definite in GEP2. No changes occurred in the nonathletic group, but the LVMM and relative LVMM in boys.
Discussion Baseline Values Basic anthropometric data failed to differ between genders in both athletes and nonathletes that is due to the different maturational status of boys and girls in this age (10). Resting heart rate in nonathletic children at this age ranges between 73–80 bpm. In some studies athletic children showed similar (20) in other studies lower HR
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50.8 ±6.4 9.3 ±0.9 43.3 ±1.3 9.3 ±1.0 30.9 ±1.1 84.3 ±7.6 62.3 ±4.7 7.7 ±0.5 34.5 ±1.9 7.8 ±0.4
Weight (kg)
IVSd (mm)
LVIDd (mm)
LVPWd (mm) LVIDs (mm) LVLAd (mm) LVLAs (mm) rel. IVSd (mm/m) rel. LVIDd (mm/m) rel. LVPWd (mm/m)
9.7 ±1.3 33.5 ±2.1 81.5 ±7.4 63.4 ±5.3 7.6 ±0.7 36.3 ±1.4 7.6 ±0.9
46.0 ±1.4
9.6 ±0.9
52.6 ±6.6
171.2 ±6.4
Endurance (GEP1)
9.6 ±1.0 34.0 ±2.1 83.1 ±8.2 62.9 ±11.1 6.86 ±0.4 37.7 ±0.6 7.4 ±0.8
48.9 ±1.7
8.9 ±0.6
57.0 ±5.1
174.2 ±4.8
Race1 (RP1)
9.2 ±0.4 34.3 ±3.5 83.7 ±6.7 64.3 ±6.2 7.2 ±0.5 39.0 ±2.4 7.0 ±0.4
51.6 ±3.8
9.5 ±0.3
61.2 ±6.7
176.7 ±4.6
Detraining (DT)
11.9 ±0.5 30.8 ±3.2 91.9 ±4.9 65.2 ±4.2 8.8 ±0.4 34.4 ±1.4 8.9 ±0.5
45.9 ±3.5
11.7 ±0.5
63.3 ±8.3
176.6 ±7.8
Endurance (GEP2)
10.5 ±0.5 30.4 ±2.6 86.6 ±4.8 62.7 ±4.8 7.7 ±0.6 35.9 ±1.2 7.9 ±0.4
48.2 ±3.1
10.4 ±0.7
63.9 ±7.8
178.0 ±6.7
Race 2 (RP2) S < RP1, DT, GEP2,RP2 GEP1 < DT, RP2 S < RP1, DT, GEP2, RP2 GEP1 < RP1, DT, GEP2, RP2 RP1 < GEP2,RPC2 GEP2 > RP1, DT S > DT,RPC2 GEP2 < DT, RP2 GEP2 > DT GEP2 < GEP1 RP1 < GEP2 GEP2 < RP1, DT GEP2 > RP1, DT
Difference
54.8 ±8.8 9.1 ±0.8 44.2 ±0.6 9.4 ±0.3 31.6 ±0.9 84.8 ±4.7 61.7 ±4.6 7.2 ±0.7 35.0 ±1.7 7.5 ±0.4
Height (cm)
Weight (kg) IVSd (mm) LVIDd (mm)
LVPWd (mm) LVIDs (mm) LVLAd (mm) LVLAs (mm) rel. IVSd (mm/m) rel. LVIDd (mm/m) rel. LVPWd (mm/m)
9.3 ±1.1 30.7 ±3.4 83.4 ±7.1 59.0 ±6.7 7.1 ±0.5 36.3 ±2.4 7.3 ±0.9
53.3 ±7.2 8.9 ±0.8 45.1 ±4.0
Endurance (GEP1) 166.9 ±8.3
9.2 ±0.8 31.9 ±3.2 83.9 ±5.1 64.6 ±4.4 6.6 ±0.5 35.6 ±2.3 7.2 ±0.8
55.3 ±6.7 8.7 ±0.8 45.6 ±2.7
Race1 (RP1) 168.9 ±6.8
8.9 ±0.5 31.4 ±2.5 84.4 ±6.8 62.0 ±6.2 6.5 ±0.4 36.8 ±1.9 6.8 ±0.4
57.1 ±5.0 8.4 ±0.7 47.6 ±2.1
Detraining (DT) 172.0 ±6.1
10.6 ±1.0 27.8 ±2.1 86.7 ±6.1 64.9 ±5.6 8.0 ±1.0 33.6 ±1.9 8.1 ±0.8
60.3 ±5.2 10.5 ±1.3 44.0 ±3.4
Endurance (GEP2) 172.6 ±6.7
9.6 ±1.0 30.3 ±2.0 85.0 ±3.1 62.6 ±4.7 7.2 ±0.7 36.2 ±2.9 7.4 ±0.8
60.4 ±5.1 9.4 ±0.8 47.5 ±3.8
Race2 (RP2) 173.3 ±6.5
Difference S < RP1, DT, GEP2,RPC2 GEP1 < RP2 GEP2,RP2 > S, GEP1,RPC1 GEP2> GEP1, RP1, DT S< RP1, DT GEP2< DT GEP2> GEP1, RP1, DT GEP2< GEP1 GEP2> GEP1, RP1 GEP1< RP1, GEP2 GEP2 > RP1, DT GEP2 < GEP1, DT, RP2 -
Note. Differences are marked significant if p < .05. Values are presented as mean ± SD. IVS = interventricular septum; LVID = left ventricular internal dimension; LVPW = left ventricular posterior wall; LVLA = left ventricular long axis; d = diastolic; s = systolic; rel. = relative/BSA1/2; S = starting preseason value; GEP1,2 = general endurance preparation period 1, 2; RP1,2 = race specific training period 1, 2; DT = detraining (DT).
Start (S) 167.2 ±8.4
Table 3 Anthropometrical and LV Morphological Changes During the Training Season in Girls
Note. Differences are marked significant if p < .05. Values are presented as mean± SD. IVS = interventricular septum; LVID = left ventricular internal dimension; LVPW = left ventricular posterior wall; LVLA = left ventricular long axis; d = diastolic; s = systolic; rel. = relative/BSA1/2, S = starting preseason value, GEP1,2 = general endurance preparation period 1, 2,. RP1,2 = race specific training period 1, 2,. DT = detraining (DT).
166.2 ±6.7
Height (cm)
Start (S)
Table 2 Anthropometrical and LV Morphological Changes During the Training Season in Boys
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(1,16,17,19,23). Our results are in agreement with those reporting lower HR in athletes (13,17,19,20); the 63 bpm in boys and the 57 bpm in girls indicate a definite training bradycardia. Resting blood pressure values were in normal range.
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Changes in the Anthropometric and Resting Cardiac Parameters Both athletic and nonathletic boys and girls grew significantly during the training season and gained weight in the same proportion, which is due to normal maturational and developmental changes. During the 1.5 years observation sexual maturational status changed significantly (boys: p = .018, girls p = .028), difference among the boys were greater, just as evident from the literature (10). The resting heart rate did not change during the observation period, which is in concordance with the findings of Snoeckx et al. (26) and Rowland et al. (23). A definite LV morphological adaptation could be detected in the swimmers similar to that described
before (1,9,13,15,17,18,20,22,24,27,28,30,31). The wall thickness (both IVS and LVPW) was greater in athletes even in the starting values, suggesting a concentric hypertrophy (1,15,17,28) such as in other trained young (9,13,18,20,22,24,27,30,31). The LVIDd of our swimmers did not differ significantly from that of sedentary boys and girls supporting the concentric hypertrophy theory (22,27,29). LVIDd was in the normal range at every measurement according to the threshold limit of Makan et al. (12) and Griffet et al. (7). Both the diastolic and systolic IVS and LVPW of athletes thickened with the endurance period; the thickest walls were measured rather at the end of the GEP2 than in the RP. This emphasizes the importance of the well-designed general endurance preparation that gives the foundations to the maximal performance achievable during the competition period. Wall thicknesses get thinner when detraining. Meanwhile, no differences could have been observed in the control group. Our results are in accordance with the results of Smith et al. (25) and Hansen et al. (8), but are different from Snoeckx et al. (26).
Table 4 Differences Between Athletes and Nonathletes Starting Values Boys IVSd (mm) Rel. IVSd (mm/m) LVIDd (mm) Rel.LVIDd (mm/m) LVPWd (mm) Rel.LVPWd (mm/m) LVMM (g) Rel.LVMM (g/m3) LVLAd (mm) LVLAs (mm) E/A IVSd (mm) Rel. IVSd (mm/m) LVIDd (mm) Rel.LVIDd (mm/m) LVPWT (mm) Rel.LVPWT (mm/m) LVMM (g) Rel.LVMM (g/m3) LVLAd (mm) LVLAs (mm) E/A
Athletes 9.3 ± 0.9 7.7 ± 0.5 43.3 ± 1.3 34.5 ± 1.9 9.3 ± 1.0 7.8 ± 0.4 183 ± 37 144 ± 23 84.3 ± 7.6 62.3 ± 4.7 1.85 ± 0.32 11.7 ± 0.5 8.8 ± 0.4 45.9 ± 3.5 34.4 ± 1.4 11.9 ± 0.5 8.9 ± 0.5 245 ± 45 182 ± 29 91.9 ± 4.9 65.2 ± 4.2 2.19 ± 0.28
Girls Athletes Nonathletes ** 9.1 ± 0.8 7.3 ± 1.3 7.6 ± 0.9* *** 7.2 ± 0.7 5.8 ± 0.7 5.9 ± 0.7** 44.7 ± 3.9 44.2 ± 0.6 46.1 ± 1.9 35.7 ± 2.6 35.0 ± 1.7 35.8 ± 1.3 * 9.4 ± 0.3 8.0 ± 0.9* 8.1 ± 1.0 ** 7.5 ± 0.4 6.4 ± 0.4 6.2 ± 0.7** *** 169 ± 10 145 ± 18 125 ± 18 133 ± 9 113 ± 13 99 ± 9*** 83.9 ± 9.8 84.8 ± 4.7 82.9 ± 6.3 60.9 ± 9.3 61.7 ± 4.6 64.6 ± 5.4 2.12 ± 0.58 2.59 ± 0.55 1.94 ± 0.69 General Endurance Preparation Period 2 (GEP2) 10.5 ± 1.3 7.8 ± 0.5*** 7.8 ± 0.4*** *** 8.0 ± 1.0 6.1 ± 0.6 6.1 ± 0.3*** 46.6 ± 3.9 44.0 ± 3.4 44.7 ± 2.9 36.1 ± 2.6 33.6 ± 1.9 35.1 ± 1.9 10.6 ± 1.0 7.8 ± 0.5*** 8.1 ± 0.6*** 8.1 ± 0.8 6.3 ± 0.7 *** 6.1 ± 0.4*** *** 203 ± 39 151 ± 18 137 ± 17** *** 154 ± 27 119 ± 12 107 ± 12** 84.5 ± 5.7 86.7 ± 6.8 83.9 ± 8.2 66.0 ± 8.2 64.9 ± 5.6 71.4 ± 6.4 2.05 ± 0.76 2.62 ± 0.61 2.12 ± 0.69 Nonathletes
Note. Values are presented as mean± SD. IVS = interventricular septum; LVID = left ventricular internal dimension; LVPW = left ventricular posterior wall; LVLA = left ventricular long axis; d = diastolic; s = systolic; LVMM = left ventricular muscle mass; rel = relative (indexed to BSA so that the nominator and the denominator have the same power); Level of significance: *: p < .05, **: p < .01, ***p < .001 between the athletic and nonathletic group.
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Also Cabanelas et al. (2) found the greatest LVPWT and LVMM results in the competition period. The latter 2 studies however, were performed in senior athletes. LVIDd followed the opposite tendency as it dilates first in the RP1 and DT period, but narrows in GEP2, which was also the findings of Ayabakan et al. (1) in swimmers. As adaptation to regular physical training is believed to begin with an increase of the LV cavity, the thickening of the LV wall occurs a bit later (13,15–18,28,31), it seems that our swimmers were already in the concentric phase. This is due to the fact that they were top-level swimmers with a long history of regular training and a high number of weekly training hours. As a result of it, the LVMM was also higher in the swimmers than in untrained individuals of similar age as described before (13,17,20,22,30,31). LVMM also reached its maximum in the GEP2 period. Our findings are congruent with the observations of D’Ascenzi et al. (5) and Smith et al. (25). Results are also similar to those of Cabanelas et al. (2). No changes were observed in the nonathletic group. The BSA indexed relative LVMM failed to change during the follow-up period. This may suggest that training adaptation of the heart develops parallel to the growth of the body size that was also the findings of Janz et al. (10). Considering our findings, it can be concluded that the characteristics of the athlete’s heart are dependent on the training period. It would be important to compare the results of studies performed at the same stage of training. Even if it is difficult to carry out since different sports require different types and periods of exercise. It would also be desirable that reports dealing with cardiac adaptation data also report the phase of the yearly training program.
Limitation of Study There are limitations to be considered when interpreting the results: our study contained a relatively low number of subjects; however, elite swimming teams of this age are this size or even smaller, and the same training in different groups cannot be carried out. Nevertheless the power of the most important tests are over 85%. No examinations were carried out to regularly check the aerobic capacity of the swimmers. Acknowledgments First of all we express our acknowledgment to the trainer and the athletes, who took part in our study voluntarily. We also thank our colleagues for their assistance; especially the help of fellow cardiologist, Katalin Eperjessy MD is appreciated. We are grateful to János László PhD, CSc for his exceptionally valuable advices and with Robert Pike for the grammatical correction.
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16. Obert P, Mandigout S, Vinet A, N’Guyen LD, Stecken F, Courteix D. Effect of aerobic training and detraining on left ventricular dimensions and diastolic function in prepubertal boys and girls. Int J Sports Med. 2001; 22(2):90–96. PubMed doi:10.1055/s-2001-11343 17. Obert P, Stecken F, Courteix D, Lecoq AM, Guenon P. Effects of long-term intensive endurance training on left ventricular structure and diastolic function in prepubertal children. Int J Sports Med. 1998; 19(2):149–154. PubMed doi:10.1055/s-2007-971897 18. Pavlik G, Major Z, Csajági E, Jeserich M, Kneffel Z. The athlete’s heart. Part II: influencing factors on the athlete’s heart: types of sports and age (review). Acta Physiol Hung. 2013; 100(1):1–27. PubMed doi:10.1556/ APhysiol.100.2013.1.1 19. Pavlik G, Olexó Zs, Osváth P, Sidó Z, Frenkl R. Echocardiographic characteristics of male athletes of different age. Br J Sports Med. 2001; 35(2):95–99. PubMed doi:10.1136/ bjsm.35.2.95 20. Petridis L, Kneffel Zs, Kispéter Zs, Horváth P, Sidó Z, Pavlik G. Echocardiographic characteristics in adolescent junior male athletes of different sport events. Acta Physiol Hung. 2004; 91(2):99–109. PubMed doi:10.1556/ APhysiol.91.2004.2.2 21. Randers MB, Andersen LJ, Orntoft C, et al. Cardiovascular health profile of elite female football players compared to untrained controls before and after short-term football training. J Sports Sci. 2013; 31(13):1421–1431. PubMed doi:10.1080/02640414.2013.792950 22. Rizzo M, Gensini F, Fatini C, et al. ACE I/D polymorphism and cardiac adaptations in adolescent athletes. Med Sci Sports Exerc. 2003; 35(12):1986–1990. PubMed doi:10.1249/01.MSS.0000098993.51693.0B 23. Rowland TW, Unnithan VB, MacFarlane NG, Paton JY. Clinical manifestations of the ‘athlete’s heart’ in prepubertal male runners. Int J Sports Med. 1994; 15(8):515–519. PubMed doi:10.1055/s-2007-1021097
24. Sharma S. Athlete’s heart – effect of age, sex, ethnicity and sporting discipline. Exp Physiol. 2003; 88(5):665–669. PubMed doi:10.1113/eph8802624 25. Smith SA, Humphrey RH, Wohlford JC, Flint DL. Myocardial adaptation and weight fluctuation in college wrestlers. Int J Sports Med. 1994; 15(2):70–73. PubMed doi:10.1055/s-2007-1021022 26. Snoeckx LH, Abeling HF, Lambregts JA, Schmitz JJ, Verstappen FT, Reneman RS. Cardiac dimensions in athletes in relation to variations in their training program. Eur J Appl Physiol Occup Physiol. 1983; 52(1):20–28. PubMed doi:10.1007/BF00429020 27. Somauroo JD, Pyatt JR, Jackson M, Perry RA, Ramsdale DR. An echocardiographic assessment of cardiac morphology and common ECG findings in teenage professional soccer players: reference ranges for use in screening. Heart. 2001; 85(6):649–654. PubMed doi:10.1136/ heart.85.6.649 28. Triposkiadis F, Ghiokas S, Skoularigis I, Kotsakis A, Giannakoulis I, Thanapoulos V. Cardiac adaptation to intensive training in prepubertal swimmers. Eur J Clin Invest. 2002; 32(1):16–23. PubMed doi:10.1046/j.00142972.2001.00939.x 29. Vasiliauskas D, Venckunas T, Marcinkeviciene JE, Bartkeviciene A. Development of structural cardiac adaptation in basketball players. Eur J Cardiovasc Prev Rehabil. 2006; 13(6):985–989. PubMed doi:10.1097/01. hjr.0000238394.04600.fc 30. Venckunas T, Lionikas A, Marcinkeviciene JE, Raugaliene R, Alekrinskis A, Stasiulis A. Echocardiographic parameters in athletes of different sports. J Sports Sci Med. 2008; 7(1):151–156. PubMed 31. Zdravkovic M, Perunicic J, Krotin M, et al. Echocardiographic study of left ventricular remodeling in highly trained preadolescent footballers. J Sci Med Sport. 2010; 13(6):602–606. PubMed doi:10.1016/j.jsams.2010.03.005
PES Vol. 27, No. 2, 2015
ORIGINAL RESEARCH
Left Ventricular Morphology in Different Periods of the Training Season in Elite Young Swimmers Eszter Csajági Semmelweis University
Ipoly Szauder Cardiologic Diagnostic Center
Zsuzsanna Major Semmelweis University
Gábor Pavlik Semmelweis University Training adaptation of the left ventricle (LV) and it’s reversibility following the cessation of training in adults is well known and also studied in children. In the current study we describe the changes in the LV morphology in association with the training season during a 1.5 year follow-up period. 15 elite adolescent swimmers, seven girls and 8 boys with 6 years of swimming history and 20 hr per week training were observed. Their data were compared with 15 age and gender matched nonathletes. LV adaptation was measured with 2D-echocardiography at the baseline preseason and every 3 months, according to the macro cyclic periods of training. Nonathletes were observed at the first and fifth stage of the study. Remarkable LV morphological adaptation has been detected in the swimmers. The greatest LV muscle mass (LVMM: 228 ± 46g) and smallest end-diastolic diameter (LVIDd:44.9 ± 3.4mm) were observed at the end of the second general endurance preparation period (GEP2), but the LVMM/BSA3/2 (Rel.LVMM: 85 ± 10g/m) failed to change during the follow-up in athletes. On the basis of our results, we suggest comparing absolute LV dimensions only in studies made at the same training period to avoid bias due to alterations with the training season. Keywords: athlete’s heart, young swimmer, echocardiography, seasonal change, left ventricle In the past decades athlete’s heart has been the focus of attention in sport medicine and cardiology. Several reviews were published indicating a slightly concentric type of left ventricular (LV) hypertrophy in adult athletes (18,19,24,30) and showing an eccentric type of hypertrophy at an early stage in young athletes (7,8,13,16–20,29,30). Physiologic cardiac adaptation is known to be reversible with the cessation of training (6,14). Also recent studies suggest that characteristics of the athlete’s heart are not constant, they may change with the actual fitness level of the athletes (5,8,21). Therefore, it can be postulated that the characteristics of the athlete’s Csajági, Major, and Pavlik are with the Dept. of Health Sciences and Sports Medicine, Semmelweis University, Budapest, Hungary. Szauder is with the Cardiologic Diagnostic Center, Budapest, Hungary. Address author correspondence to Eszter Csajági at [email protected].
heart might change during the different phases of the yearly training period as well (2,5,25,26). Moreover, athletic characteristics including cardiac adaptation are expected to change more quickly in the early years; hence, seasonal variations can be expected to be more prominent in children than in adults. In younger athletes physiologic maturation also has to be considered in the development of the characteristics of the athlete’s heart. In some previous studies authors found increased LV dimensions in the active period of the yearly training program: Smith et al. (25) found thicker LV wall in wrestlers, D’Ascenzi et al. (5) and Cabanelas et al. (2) greater LV muscle mass (LVMM) in elite soccer players. On the other hand Snoeckx et al. (26) in runners and cyclists and Randers et al. (21) in elite female football players found no differences among parameters measured in the different phases of the training program. Data in young athletes are limited: Hansen et al. (8) reported a thicker LV posterior wall (LVPW) after 3 months of
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soccer training in overweight children. The Muscatine Study (10) described the dynamics of the heart development in puberty in healthy individuals. Evaluating the seasonal changes in the characteristics of the athlete’s heart can be a reliable way to characterize the athlete’s physical condition, especially the endurance ability (4). Also interindividual differences in the adaptation to training can be observed (4). The present study aimed to investigate the seasonal variations in the morphological characteristics of the athlete’s heart in young swimmers to better understand the physiologic cardiac adaptation in the young.
Subjects and Methods
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Subjects 18 top-level young swimmers were invited to participate in the study. All of them were members of the same leading swimming club, and invited to the national team in their age category (13–15 yrs). Children performed regular training for at least the last 4 years, for an average of more than 20 hr per week (Table 1.). Seven girls and 8 boys completed the 1.5-year observational period, 2 girls and 1 boy stopped participation before completion of observational period. In the first and fifth stage of the study their results were compared with healthy, nontrained, age and gender matched nonathletes (Table 1.). This comparison aimed to differentiate between training effect and physiological development. Subjects who didn’t show adequate compliance or had any disorders that would preclude training eligibility were excluded from the study (3). All participants and parents gave written consent to the study, which was approved by the Regional and Institutional Committee of Science and Research Ethics of the university (TUKEB Nr: 121/2010). Basic anthropometric data and training history are presented in Table 1.
Methods The longitudinal study contained 6 follow-up examinations during 18 months adjusted to the macro and micro cyclic variations in the training period: every 3 month in the preseason baseline (S), at the end of the general endurance preparation period 1 (GEP1), in the race specific training period 1 (RP1), after detraining (DT), at the end of the general endurance preparation period 2 (GEP2), and in the race specific training period 2 (RP2). At baseline a questionnaire used in sport medicine was completed with parental guide documenting the training habits and history, medical and family history. Blood pressure, body height, and weight were measured followed by physical examination and a 12-lead ECG (Innomed Heart Screen, Budapest, Hungary). Sexual maturation was judged according to the recommendations of Janz et al. (10). 2D-, Doppler-, and TDI echocardiography was carried out with a Philips HD15 Echocardiograph (1–5 MHz, Koninkiljke Philips, NV, USA) according to the standards of the American Society of Echocardiography
(11) in the steep left lateral decubitus position. Followup examinations have been performed every third month (8,10,21). All examinations were carried out by the same physician. Nonathletic children were examined according to the timing of the first (S) and fifth (GEP2) occasion. Echocardiography examinations were analyzed offline. Each parameter was estimated on 3–5 heart cycles to minimize intraobserver variability. The averages were used in the further analysis. Heart rate (HR) was measured on the Doppler echocardiographic curves. From the parasternal 2D-guided M mode recordings, the following data were acquired: LV end diastolic septal (IVSd) and posterior wall thickness (LVPWTd), and LV end diastolic (LVIDd) and end systolic (LVIDs) dimensions. Meanwhile, the left ventricular long axis (LVLA) in systole and diastole were obtained from the apical 4-chamber view. Relative values were referred to the indexed BSA: so that the nominator and the denominator have the same power (13,19,20). Calculated values were the LVMM according to the ASE recommendations (11). Statistical analysis was carried out with Statistica for Windows 11.0 (Stat Soft, Tulsa, OK, USA). Distribution of the parameters was tested with the Shapiro-Wilks test. Data of nonathletes were compared with Wilcoxon test, data of athletes with repeated measure or Friedmann ANOVA and post hoc tests. Level of significance was set at 5%.
Results Anthropometric Parameters and Basic Echocardiographic Data Athletes: changes in height followed the normal development predicted by the age and appeared parallel in boys and girls, but no difference was observed between genders (Table 1). Weight was developing nearly the same way. No differences in the resting heart rate (HR): boys: 63 ± 9 bpm; girls: 57 ± 4 bpm and in the blood pressure values systolic (BPS): boys: 112.5 ± 2.7 mmHg; girls: 111.2 ± 11.7 mmHg; diastolic (BPD): boys: 67.5 ± 2.7 mmHg, girls: 67.5 ± 5.2 mmHg were observed with the training season or between the genders. The nonathletic group was age and gender matched. There was no difference in the height, weight and resting BP values and sexual maturation. Swimmer girls had lower HR than controls (Table 1).
Left Ventricular Morphological Changes with the Training Season Changes in the absolute and indexed (values are indexed to the BSA1/2 for LVWT and dimensions and BSA3/2 for the LVMM) parameters describing the left ventricular morphology are presented in Table 2 for boys and Table 3 for girls. Differences are shown in the last columns, when significant. Figure 1 indicates the seasonal changes in LVMM. The greatest LVMM and smallest LVIDd were detected in GEP2, but the Rel.LVMM didn’t change during the follow-up in athletes.
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Table 1 Basic Anthropometric Data and Training History Athletes
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Characteristics Age (y) Height (m) Weight (kg) HR (1/min) BPS (mmHg) BPD (mmHg) Training history (y) Training (hr/week) Sexual maturation
Boys 13.8 ± 0.7 1.66 ± 0.07 50.8 ± 6.4 63 ± 9 112.5 ± 2.7 67.5 ± 2.7 6.4 ± 1.4 23.2 ± 4.1 2.87 (1–4)
Girls 13.8 ± 0.9 1.67 ± 0.08 54.8 ± 8.8 57 ± 4 111.2 ± 11.7 67.5 ± 5.2 5.9 ± 1.7 20.3 ± 5.5 3.3 (3–4)
Nonathletes Boys Girls 13.8 ± 0.7 13.8 ± 0.9 1.60 ± 0.12 1.63 ± 0.06 49.8 ± 10.7 55.3 ± 6.2 69 ± 12 75 ± 11 120.0 ± 7.0 121.4 ± 11.1 64.4 ± 6.8 67.1 ± 9.1 0.28 (0–1) 0.23 (0–0.6) 3 (1–4) 3.6 (2–5)
Note. Sexual maturation was judged on a 5 point scale: 1: pre, 2: early-, 3: mid, 4: late-, 5: post puberty. Values are shown as mean ± SD for normal distribution parameters and median with minimum and maximum for nonnormal distribution. Significant difference between athletic and nonathletic group are marked bold. HR = heart rate; BPS = systolic blood pressure; BPD = diastolic blood pressure.
Figure 1 — Changes in the LVMM with the training season. LVMM = left ventricular muscle mass; S = starting preseason value; GEP1,2 = general endurance preparation period 1,2; RP1, 2 = race-specific training period 1,2; DT = detraining (DT). Level of significance: *p < .05, ***p < .001. Values are presented as mean ± SD.
Differences Between the Athletes and Nonathletes Differences between the athletic and nonathletic children are presented in Table 4. Even in the starting values marked differences were observed in the absolute and relative wall thickness and the LVMM between the two groups in both genders. The difference was even more definite in GEP2. No changes occurred in the nonathletic group, but the LVMM and relative LVMM in boys.
Discussion Baseline Values Basic anthropometric data failed to differ between genders in both athletes and nonathletes that is due to the different maturational status of boys and girls in this age (10). Resting heart rate in nonathletic children at this age ranges between 73–80 bpm. In some studies athletic children showed similar (20) in other studies lower HR
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50.8 ±6.4 9.3 ±0.9 43.3 ±1.3 9.3 ±1.0 30.9 ±1.1 84.3 ±7.6 62.3 ±4.7 7.7 ±0.5 34.5 ±1.9 7.8 ±0.4
Weight (kg)
IVSd (mm)
LVIDd (mm)
LVPWd (mm) LVIDs (mm) LVLAd (mm) LVLAs (mm) rel. IVSd (mm/m) rel. LVIDd (mm/m) rel. LVPWd (mm/m)
9.7 ±1.3 33.5 ±2.1 81.5 ±7.4 63.4 ±5.3 7.6 ±0.7 36.3 ±1.4 7.6 ±0.9
46.0 ±1.4
9.6 ±0.9
52.6 ±6.6
171.2 ±6.4
Endurance (GEP1)
9.6 ±1.0 34.0 ±2.1 83.1 ±8.2 62.9 ±11.1 6.86 ±0.4 37.7 ±0.6 7.4 ±0.8
48.9 ±1.7
8.9 ±0.6
57.0 ±5.1
174.2 ±4.8
Race1 (RP1)
9.2 ±0.4 34.3 ±3.5 83.7 ±6.7 64.3 ±6.2 7.2 ±0.5 39.0 ±2.4 7.0 ±0.4
51.6 ±3.8
9.5 ±0.3
61.2 ±6.7
176.7 ±4.6
Detraining (DT)
11.9 ±0.5 30.8 ±3.2 91.9 ±4.9 65.2 ±4.2 8.8 ±0.4 34.4 ±1.4 8.9 ±0.5
45.9 ±3.5
11.7 ±0.5
63.3 ±8.3
176.6 ±7.8
Endurance (GEP2)
10.5 ±0.5 30.4 ±2.6 86.6 ±4.8 62.7 ±4.8 7.7 ±0.6 35.9 ±1.2 7.9 ±0.4
48.2 ±3.1
10.4 ±0.7
63.9 ±7.8
178.0 ±6.7
Race 2 (RP2) S < RP1, DT, GEP2,RP2 GEP1 < DT, RP2 S < RP1, DT, GEP2, RP2 GEP1 < RP1, DT, GEP2, RP2 RP1 < GEP2,RPC2 GEP2 > RP1, DT S > DT,RPC2 GEP2 < DT, RP2 GEP2 > DT GEP2 < GEP1 RP1 < GEP2 GEP2 < RP1, DT GEP2 > RP1, DT
Difference
54.8 ±8.8 9.1 ±0.8 44.2 ±0.6 9.4 ±0.3 31.6 ±0.9 84.8 ±4.7 61.7 ±4.6 7.2 ±0.7 35.0 ±1.7 7.5 ±0.4
Height (cm)
Weight (kg) IVSd (mm) LVIDd (mm)
LVPWd (mm) LVIDs (mm) LVLAd (mm) LVLAs (mm) rel. IVSd (mm/m) rel. LVIDd (mm/m) rel. LVPWd (mm/m)
9.3 ±1.1 30.7 ±3.4 83.4 ±7.1 59.0 ±6.7 7.1 ±0.5 36.3 ±2.4 7.3 ±0.9
53.3 ±7.2 8.9 ±0.8 45.1 ±4.0
Endurance (GEP1) 166.9 ±8.3
9.2 ±0.8 31.9 ±3.2 83.9 ±5.1 64.6 ±4.4 6.6 ±0.5 35.6 ±2.3 7.2 ±0.8
55.3 ±6.7 8.7 ±0.8 45.6 ±2.7
Race1 (RP1) 168.9 ±6.8
8.9 ±0.5 31.4 ±2.5 84.4 ±6.8 62.0 ±6.2 6.5 ±0.4 36.8 ±1.9 6.8 ±0.4
57.1 ±5.0 8.4 ±0.7 47.6 ±2.1
Detraining (DT) 172.0 ±6.1
10.6 ±1.0 27.8 ±2.1 86.7 ±6.1 64.9 ±5.6 8.0 ±1.0 33.6 ±1.9 8.1 ±0.8
60.3 ±5.2 10.5 ±1.3 44.0 ±3.4
Endurance (GEP2) 172.6 ±6.7
9.6 ±1.0 30.3 ±2.0 85.0 ±3.1 62.6 ±4.7 7.2 ±0.7 36.2 ±2.9 7.4 ±0.8
60.4 ±5.1 9.4 ±0.8 47.5 ±3.8
Race2 (RP2) 173.3 ±6.5
Difference S < RP1, DT, GEP2,RPC2 GEP1 < RP2 GEP2,RP2 > S, GEP1,RPC1 GEP2> GEP1, RP1, DT S< RP1, DT GEP2< DT GEP2> GEP1, RP1, DT GEP2< GEP1 GEP2> GEP1, RP1 GEP1< RP1, GEP2 GEP2 > RP1, DT GEP2 < GEP1, DT, RP2 -
Note. Differences are marked significant if p < .05. Values are presented as mean ± SD. IVS = interventricular septum; LVID = left ventricular internal dimension; LVPW = left ventricular posterior wall; LVLA = left ventricular long axis; d = diastolic; s = systolic; rel. = relative/BSA1/2; S = starting preseason value; GEP1,2 = general endurance preparation period 1, 2; RP1,2 = race specific training period 1, 2; DT = detraining (DT).
Start (S) 167.2 ±8.4
Table 3 Anthropometrical and LV Morphological Changes During the Training Season in Girls
Note. Differences are marked significant if p < .05. Values are presented as mean± SD. IVS = interventricular septum; LVID = left ventricular internal dimension; LVPW = left ventricular posterior wall; LVLA = left ventricular long axis; d = diastolic; s = systolic; rel. = relative/BSA1/2, S = starting preseason value, GEP1,2 = general endurance preparation period 1, 2,. RP1,2 = race specific training period 1, 2,. DT = detraining (DT).
166.2 ±6.7
Height (cm)
Start (S)
Table 2 Anthropometrical and LV Morphological Changes During the Training Season in Boys
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(1,16,17,19,23). Our results are in agreement with those reporting lower HR in athletes (13,17,19,20); the 63 bpm in boys and the 57 bpm in girls indicate a definite training bradycardia. Resting blood pressure values were in normal range.
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Changes in the Anthropometric and Resting Cardiac Parameters Both athletic and nonathletic boys and girls grew significantly during the training season and gained weight in the same proportion, which is due to normal maturational and developmental changes. During the 1.5 years observation sexual maturational status changed significantly (boys: p = .018, girls p = .028), difference among the boys were greater, just as evident from the literature (10). The resting heart rate did not change during the observation period, which is in concordance with the findings of Snoeckx et al. (26) and Rowland et al. (23). A definite LV morphological adaptation could be detected in the swimmers similar to that described
before (1,9,13,15,17,18,20,22,24,27,28,30,31). The wall thickness (both IVS and LVPW) was greater in athletes even in the starting values, suggesting a concentric hypertrophy (1,15,17,28) such as in other trained young (9,13,18,20,22,24,27,30,31). The LVIDd of our swimmers did not differ significantly from that of sedentary boys and girls supporting the concentric hypertrophy theory (22,27,29). LVIDd was in the normal range at every measurement according to the threshold limit of Makan et al. (12) and Griffet et al. (7). Both the diastolic and systolic IVS and LVPW of athletes thickened with the endurance period; the thickest walls were measured rather at the end of the GEP2 than in the RP. This emphasizes the importance of the well-designed general endurance preparation that gives the foundations to the maximal performance achievable during the competition period. Wall thicknesses get thinner when detraining. Meanwhile, no differences could have been observed in the control group. Our results are in accordance with the results of Smith et al. (25) and Hansen et al. (8), but are different from Snoeckx et al. (26).
Table 4 Differences Between Athletes and Nonathletes Starting Values Boys IVSd (mm) Rel. IVSd (mm/m) LVIDd (mm) Rel.LVIDd (mm/m) LVPWd (mm) Rel.LVPWd (mm/m) LVMM (g) Rel.LVMM (g/m3) LVLAd (mm) LVLAs (mm) E/A IVSd (mm) Rel. IVSd (mm/m) LVIDd (mm) Rel.LVIDd (mm/m) LVPWT (mm) Rel.LVPWT (mm/m) LVMM (g) Rel.LVMM (g/m3) LVLAd (mm) LVLAs (mm) E/A
Athletes 9.3 ± 0.9 7.7 ± 0.5 43.3 ± 1.3 34.5 ± 1.9 9.3 ± 1.0 7.8 ± 0.4 183 ± 37 144 ± 23 84.3 ± 7.6 62.3 ± 4.7 1.85 ± 0.32 11.7 ± 0.5 8.8 ± 0.4 45.9 ± 3.5 34.4 ± 1.4 11.9 ± 0.5 8.9 ± 0.5 245 ± 45 182 ± 29 91.9 ± 4.9 65.2 ± 4.2 2.19 ± 0.28
Girls Athletes Nonathletes ** 9.1 ± 0.8 7.3 ± 1.3 7.6 ± 0.9* *** 7.2 ± 0.7 5.8 ± 0.7 5.9 ± 0.7** 44.7 ± 3.9 44.2 ± 0.6 46.1 ± 1.9 35.7 ± 2.6 35.0 ± 1.7 35.8 ± 1.3 * 9.4 ± 0.3 8.0 ± 0.9* 8.1 ± 1.0 ** 7.5 ± 0.4 6.4 ± 0.4 6.2 ± 0.7** *** 169 ± 10 145 ± 18 125 ± 18 133 ± 9 113 ± 13 99 ± 9*** 83.9 ± 9.8 84.8 ± 4.7 82.9 ± 6.3 60.9 ± 9.3 61.7 ± 4.6 64.6 ± 5.4 2.12 ± 0.58 2.59 ± 0.55 1.94 ± 0.69 General Endurance Preparation Period 2 (GEP2) 10.5 ± 1.3 7.8 ± 0.5*** 7.8 ± 0.4*** *** 8.0 ± 1.0 6.1 ± 0.6 6.1 ± 0.3*** 46.6 ± 3.9 44.0 ± 3.4 44.7 ± 2.9 36.1 ± 2.6 33.6 ± 1.9 35.1 ± 1.9 10.6 ± 1.0 7.8 ± 0.5*** 8.1 ± 0.6*** 8.1 ± 0.8 6.3 ± 0.7 *** 6.1 ± 0.4*** *** 203 ± 39 151 ± 18 137 ± 17** *** 154 ± 27 119 ± 12 107 ± 12** 84.5 ± 5.7 86.7 ± 6.8 83.9 ± 8.2 66.0 ± 8.2 64.9 ± 5.6 71.4 ± 6.4 2.05 ± 0.76 2.62 ± 0.61 2.12 ± 0.69 Nonathletes
Note. Values are presented as mean± SD. IVS = interventricular septum; LVID = left ventricular internal dimension; LVPW = left ventricular posterior wall; LVLA = left ventricular long axis; d = diastolic; s = systolic; LVMM = left ventricular muscle mass; rel = relative (indexed to BSA so that the nominator and the denominator have the same power); Level of significance: *: p < .05, **: p < .01, ***p < .001 between the athletic and nonathletic group.
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190 Csajági et al.
Also Cabanelas et al. (2) found the greatest LVPWT and LVMM results in the competition period. The latter 2 studies however, were performed in senior athletes. LVIDd followed the opposite tendency as it dilates first in the RP1 and DT period, but narrows in GEP2, which was also the findings of Ayabakan et al. (1) in swimmers. As adaptation to regular physical training is believed to begin with an increase of the LV cavity, the thickening of the LV wall occurs a bit later (13,15–18,28,31), it seems that our swimmers were already in the concentric phase. This is due to the fact that they were top-level swimmers with a long history of regular training and a high number of weekly training hours. As a result of it, the LVMM was also higher in the swimmers than in untrained individuals of similar age as described before (13,17,20,22,30,31). LVMM also reached its maximum in the GEP2 period. Our findings are congruent with the observations of D’Ascenzi et al. (5) and Smith et al. (25). Results are also similar to those of Cabanelas et al. (2). No changes were observed in the nonathletic group. The BSA indexed relative LVMM failed to change during the follow-up period. This may suggest that training adaptation of the heart develops parallel to the growth of the body size that was also the findings of Janz et al. (10). Considering our findings, it can be concluded that the characteristics of the athlete’s heart are dependent on the training period. It would be important to compare the results of studies performed at the same stage of training. Even if it is difficult to carry out since different sports require different types and periods of exercise. It would also be desirable that reports dealing with cardiac adaptation data also report the phase of the yearly training program.
Limitation of Study There are limitations to be considered when interpreting the results: our study contained a relatively low number of subjects; however, elite swimming teams of this age are this size or even smaller, and the same training in different groups cannot be carried out. Nevertheless the power of the most important tests are over 85%. No examinations were carried out to regularly check the aerobic capacity of the swimmers. Acknowledgments First of all we express our acknowledgment to the trainer and the athletes, who took part in our study voluntarily. We also thank our colleagues for their assistance; especially the help of fellow cardiologist, Katalin Eperjessy MD is appreciated. We are grateful to János László PhD, CSc for his exceptionally valuable advices and with Robert Pike for the grammatical correction.
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