Echocardiographic dimensions and maximal oxygen uptake in oarsmen during training

The athlete's heart: allometric considerations on published papers and relation to cardiovascular variables

To evaluate the morphology of the "athlete's heart", left ventricular (LV) wall thickness (WT) and end-diastolic internal diameter (LVIDd) at rest were addressed in publications on skiers, rowers, swimmers, cyclists, runners, weightlifters (n = 927), and untrained controls (n = 173) and related to the acute and maximal cardiovascular response to their respective disciplines. Dimensions of the heart at rest and functional variables established during the various sport disciplines were scaled to body weight for comparison among athletes independent of body mass. The two measures of LV were related (r = 0.8; P = 0.04) across athletic disciplines. With allometric scaling to body weight, LVIDd was similar between weightlifters and controls but 7%-15% larger in the other athletic groups, while WT was 9%-24% enlarged in all athletes. The LVIDd was related to stroke volume, oxygen pulse, maximal oxygen uptake, cardiac output, and blood volume (r =  ~ 0.9, P < 0.05), while there was no relationship between WT and these variables (P > 0.05). In conclusion, while cardiac enlargement is, in part, essential for the generation of the cardiac output and thus stroke volume needed for competitive endurance exercise, an enlarged WT seems important for the development of the wall tension required for establishing normal arterial pressure in the enlarged LVIDd.

Low- and high-volume blood-flow restriction treadmill walking both improve maximal aerobic capacity independently of blood volume

AIM

Assess the effect of low- and high-volume blood flow restriction training (BFR) on maximal aerobic capacity (VO2 max) and determine if alteration in VO2 max is mediated through changes in hemoglobin mass (Hbmass) and blood volume.

METHODS

Participants' Hbmass (CO-rebreathe), single, and double-leg VO2 max and blood volume regulating hormonal responses (renin and copeptin) were measured before and after BFR training. Training consisted of treadmill walking either (1) twice-daily for 4week (CON and BFRHV ) or (2) twice-weekly for 6week (BFRLV ). Each session consisted of five intervals (3 min, 5% incline, 5 km/h, 100% of lowest occlusion pressure), with 1 min of standing rest between sets.

RESULTS

VO2 max increased using both training exposures, in as quickly as 2-weeks (BFRLV baseline to 4week: +315 ± 241 mL (8.7%), p = 0.02; BFRHV baseline to 2week: +360 ± 261 mL (7.9%), p < 0.01), for the BFRLV and BFRHV groups, with no change in CON. Single- and double-leg VO2 max improved proportionately (single/double-leg VO2 max ratio: BFRLV 78 ± 4.9-78 ± 5.8%, BFRHV 79 ± 6.5-77 ± 6.5%), suggesting that the mechanism for increased VO2 max is not solely limited to central or peripheral adaptations. Hbmass remained unchanged across groups (CON: +10.2 ± 34 g, BFRLV : +6.6 ± 42 g, BFRHV : +3.2 ± 44 g; p = 0.9), despite a significant release of blood volume regulating hormones after initial BFR exposure (renin +20.8 ± 21.9 ng/L, p < 0.01; copeptin +22.0 ± 23.8 pmol/L, p < 0.01), which was blunted following BFRHV training (renin: +13.4 ± 12.4 ng/L, p = 0.09; copeptin: +1.9 ± 1.7 pmol/L, p = 0.98).

CONCLUSION

BFR treadmill walking increases VO2 max irrespective of changes in Hbmass or blood volume despite a large release of blood volume regulating hormones in response to BFR treadmill walking.

Cardiac Structure and Cardiorespiratory Fitness in Young Male Japanese Rugby Athletes

Limited data are available on athlete's heart for rugby athletes. This study aimed to investigate cardiac structure and its relationship with cardiorespiratory fitness in young Japanese rugby athletes. A prospective cross-sectional study using echocardiography and cardiopulmonary exercise testing (CPET) was conducted on 114 male collegiate rugby players. There was a higher prevalence of increased left ventricular (LV), atrial, and aortic dimensions in the young athletes than that in previously published reports, whereas the wall thickness was within the normal range. Anthropometry and CPET analyses indicated that the forwards and backs presented muscular and endurance phenotypes, respectively. Indexed LV and aortic dimensions were significantly larger in the backs than in the forwards, and the dimensions significantly correlated with oxygen uptake measured by CPET. On the four-tiered classification for LV hypertrophy, abnormal LV geometry was found in 16% of the athletes. Notably, the resting systolic blood pressure was significantly higher in athletes with concentric abnormal geometry than in the other geometry groups, regardless of their field positions. Japanese young athletes may exhibit unique phenotypes of cardiac remodeling in association with their fitness characteristics. The four-tiered LV geometry classification potentially offers information regarding the subclinical cardiovascular risks of young athletes.

The physiology of rowing with perspective on training and health

PURPOSE

This review presents a perspective on the expansive literature on rowing.

METHODS

The PubMed database was searched for the most relevant literature, while some information was obtained from books.

RESULTS

Following the life span of former rowers paved the way to advocate exercise for health promotion. Rowing involves almost all muscles during the stroke and competition requires a large oxygen uptake, which is challenged by the pulmonary diffusion capacity and restriction in blood flow to the muscles. Unique training adaptations allow for simultaneous engagement of the legs in the relatively slow movement of the rowing stroke that, therefore, involves primarily slow-twitch muscle fibres. Like other sport activities, rowing is associated with adaptation not only of the heart, including both increased internal diameters and myocardial size, but also skeletal muscles with hypertrophy of especially slow-twitch muscle fibres. The high metabolic requirement of intense rowing reduces blood pH and, thereby, arterial oxygen saturation decreases as arterial oxygen tension becomes affected.

CONCLUSION

Competitive rowing challenges most systems in the body including pulmonary function and circulatory control with implication for cerebral blood flow and neuromuscular activation. Thus, the physiology of rowing is complex, but it obviously favours large individuals with arms and legs that allow the development of a long stroke. Present inquiries include the development of an appropriately large cardiac output despite the Valsalva-like manoeuvre associated with the stroke, and the remarkable ability of the brain to maintain motor control and metabolism despite marked reductions in cerebral blood flow and oxygenation.

Cardiovascular Adaptations to Exercise Training

Aerobic exercise training leads to cardiovascular changes that markedly increase aerobic power and lead to improved endurance performance. The functionally most important adaptation is the improvement in maximal cardiac output which is the result of an enlargement in cardiac dimension, improved contractility, and an increase in blood volume, allowing for greater filling of the ventricles and a consequent larger stroke volume. In parallel with the greater maximal cardiac output, the perfusion capacity of the muscle is increased, permitting for greater oxygen delivery. To accommodate the higher aerobic demands and perfusion levels, arteries, arterioles, and capillaries adapt in structure and number. The diameters of the larger conduit and resistance arteries are increased minimizing resistance to flow as the cardiac output is distributed in the body and the wall thickness of the conduit and resistance arteries is reduced, a factor contributing to increased arterial compliance. Endurance training may also induce alterations in the vasodilator capacity, although such adaptations are more pronounced in individuals with reduced vascular function. The microvascular net increases in size within the muscle allowing for an improved capacity for oxygen extraction by the muscle through a greater area for diffusion, a shorter diffusion distance, and a longer mean transit time for the erythrocyte to pass through the smallest blood vessels. The present article addresses the effect of endurance training on systemic and peripheral cardiovascular adaptations with a focus on humans, but also covers animal data.

A Meta-Analysis of Aortic Root Size in Elite Athletes

Background—

The aorta is exposed to hemodynamic stress during exercise, but whether or not the aorta is larger in athletes is not clear. We performed a systematic literature review and meta-analysis to examine whethere athletes demonstrate increased aortic root dimensions compared with nonathlete controls.

Methods and Results—

We searched MEDLINE and Scopus from inception through August 12, 2012, for English-language studies reporting the aortic root size in elite athletes. Two investigators independently extracted athlete and study characteristics. A multivariate linear mixed model was used to conduct meta-regression analyses. We identified 71 studies reporting aortic root dimensions in 8564 unique athletes, but only 23 of these studies met our criteria by reporting aortic root dimensions at the aortic valve annulus or sinus of Valsalva in elite athletes (n=5580). Athletes were compared directly with controls (n=727) in 13 studies. On meta-regression, the weighted mean aortic root diameter measured at the sinuses of Valsalva was 3.2 mm ( P =0.02) larger in athletes than in the nonathletic controls, whereas aortic root size at the aortic valve annulus was 1.6 mm ( P =0.04) greater in athletes than in controls.

Conclusions—

Elite athletes have a small but significantly larger aortic root diameter at the sinuses of Valsalva and aortic valve annulus, but this difference is minor and clinically insignificant. Clinicians evaluating athletes should know that marked aortic root dilatation likely represents a pathological process and not a physiological adaptation to exercise.

Influence of 12 weeks of jogging on magnetic resonance-determined left ventricular characteristics in previously sedentary subjects free of cardiovascular disease

Hypertrophy of the left ventricle is a diagnostic dilemma in subjects who engage in regular endurance exercise. We studied prospectively whether endurance training in previously sedentary young and middle-aged men and women can alter left ventricular (LV) characteristics. We recruited 33 healthy young and middle-aged subjects (18 women, 15 men, ages 21 to 59 years) to undergo 12 weeks of home-based brisk walking and jogging at a target heart rate > or =120 beats/min for > or =30 minutes 3 times a week. LV characteristics were measured by cine magnetic resonance imaging. Training intensity as estimated by heart rate correlated positively with the increase in LV myocardial area (r = 0.51, p = 0.005) in the 28 men and women completing the study. In the 13 men and women who trained with heart rate of > or =120 beats/min, LV myocardial area was larger after than before training (17.7 +/- 2.9 vs 16.8 +/- 2.8 cm(2), p <0.05). Moreover, in these subjects LV myocardial area increased more (5.5 +/- 9.0% vs -3.0 +/- 5.0%) than in the 15 men and women who trained at a lower intensity (p <0.05). LV end-systolic and end-diastolic area and ejection fraction did not change significantly. In conclusion, moderate-to-vigorous endurance training at moderate volumes does not influence LV end-diastolic volume or ejection fraction, but has a minor influence on LV hypertrophy in previously sedentary young and middle-aged men and women.

Training-specific changes in cardiac structure and function: a prospective and longitudinal assessment of competitive athletes

This prospective, longitudinal study examined the effects of participation in team-based exercise training on cardiac structure and function. Competitive endurance athletes (EA, n = 40) and strength athletes (SA, n = 24) were studied with echocardiography at baseline and after 90 days of team training. Left ventricular (LV) mass increased by 11% in EA (116 ± 18 vs. 130 ± 19 g/m2; P < 0.001) and by 12% in SA (115 ± 14 vs. 132 ± 11 g/m2; P < 0.001; P value for the compared Δ = NS). EA experienced LV dilation (end-diastolic volume: 66.6 ± 10.0 vs. 74.7 ± 9.8 ml/m2, Δ = 8.0 ± 4.2 ml/m2; P < 0.001), enhanced diastolic function (lateral E ′: 10.9 ± 0.8 vs. 12.4 ± 0.9 cm/s, P < 0.001), and biatrial enlargement, while SA experience LV hypertrophy (posterior wall: 4.5 ± 0.5 vs. 5.2 ± 0.5 mm/m2, P < 0.001) and diminished diastolic function (E′ basal lateral LV: 11.6 ± 1.3 vs. 10.2 ± 1.4 cm/s, P < 0.001). Further, EA experienced right ventricular (RV) dilation (end-diastolic area: 1,460 ± 220 vs. 1,650 ± 200 mm/m2, P < 0.001) coupled with enhanced systolic and diastolic function (E′ basal RV: 10.3 ± 1.5 vs. 11.4 ± 1.7 cm/s, P < 0.001), while SA had no change in RV parameters. We conclude that participation in 90 days of competitive athletics produces significant training-specific changes in cardiac structure and function. EA develop biventricular dilation with enhanced diastolic function, while SA develop isolated, concentric left ventricular hypertrophy with diminished diastolic relaxation.

Relationships between sports-specific characteristics of athlete's heart and maximal oxygen uptake

BACKGROUND

Improvement to maximal oxygen uptake is mainly due to myocardial adaptations brought about by physical training. As a consequence, the athlete's heart echocardiographic modifications associated with these adaptations are already well-known. We studied the relationships between maximal oxygen uptake (ml/min) and resting echocardiographic patterns in three athlete groups.

METHODS

Tumbling (n=16), canoeing (n=12), cycling (n=12) and untrained (n=19) participants performed clinical examination and an echocardiogram. Trained groups performed a maximal graded exercise test on a cycle ergometer with gas exchange analysis.

RESULTS

Sport-specific cardiac hypertrophy was observed. No significant echocardiographic difference was noted between untrained and tumbling participants. Canoeists showed higher end-diastolic thickness of the interventricular septum (P<0.001) and left ventricle mass (P<0.05) than untrained and higher posterior wall thickness (P<0.001) and than untrained and tumbling participants. In comparison between untrained, tumbling and cycling participants, left ventricular end-diastolic diameter (P<0.001) and left ventricular mass (P<0.001) was higher in cyclists. In trained subjects studied as a global group, the main linear correlation with maximal oxygen uptake concerned left ventricular end-diastolic diameter (r=0.92; P<0.001), left ventricular mass (r=0.60; P<0.001) and to a lesser extent aortic (r=0.39; P<0.01) and left atrium (r=0.36; P<0.05) diameters and E (r=0.38; P<0.05) and A (r=-0.33; P<0.05) Doppler peak velocities. Each trained group showed specific correlations between echocardiographic parameters and absolute maximal oxygen uptake. No further correlation was noted with left ventricular end-diastolic diameter or left ventricle mass when each group was studied individually.

CONCLUSIONS

In athletes, maximal oxygen uptake is partly linked to some resting echocardiographic parameters. Specific relationships between maximal oxygen uptake and some echocardiographic parameters in relation to the sport practised are also observed.

Physiological upper limits of ventricular cavity size in highly trained adolescent athletes

OBJECTIVES

To define physiological upper limits of left ventricular (LV) cavity size in trained adolescent athletes.

DESIGN

Cross sectional echocardiographic study.

SETTING

British national sports training grounds and Olympic Medical Institute.

SUBJECTS

900 elite adolescent athletes (77% boys) aged 15.7 (1.2) years participating in ball, racket, and endurance sports and 250 healthy controls matched for age, sex, and size.

MAIN OUTCOME MEASURES

LV end diastolic cavity size.

RESULTS

Compared with controls, athletes had a larger LV cavity (50.8 (3.7) v 47.9 (3.5) mm), a difference of 6%. The LV cavity was > 54 mm in 18% athletes, whereas none of the controls had an LV cavity > 54 mm. The LV cavity exceeded predicted sizes in 117 (13%) athletes. Among the athletes with LV dilatation, 78% were boys, LV size ranged from 52-60 mm, and left atrial diameter and LV wall thickness were enlarged. Systolic and diastolic function were normal. None of the athletes in the study had an LV cavity size > 60 mm. LV cavity size correlated with age, sex, heart rate, and body surface area.

CONCLUSION

Highly trained junior athletes usually have only modest increases in LV cavity size. A proportion of trained adolescent athletes have LV cavity size exceeding predicted values but, in absolute terms, LV cavity rarely exceeds 60 mm as in patients with dilated cardiomyopathy. In highly trained adolescent athletes with an LV cavity size > 60 mm and any impairment of systolic or diastolic function, the diagnosis of dilated cardiomyopathy should be considered.

Concentric adaptation of the left ventricle in response to controlled upper body exercise training

Upper body exercise has many applications to the rehabilitation and maintenance of cardiovascular health of individuals who are unable to exercise their lower body. The hemodynamic loads of upper body aerobic exercise are characterized by relatively high blood pressure and relatively low venous return. It is not clear how the left ventricle adapts to the specific hemodynamic loads associated with this form of exercise training. The purpose of this study was to measure left ventricular structure and function in previously sedentary men by using echocardiography before and after 12 wk of aerobic arm-crank exercise training (n = 22) or a time control period (n = 22). Arm-crank peak oxygen consumption (in ml x kg(-1) x min(-1)) increased by 16% (P < 0.05) after training, and significant differences (P < 0.05) were found in wall thickness (from 0.86 to 0.99 cm) but not in left ventricular internal dimension in diastole or systole. This suggested a concentric pattern of left ventricular hypertrophy that persisted after scaling to changes in anthropometric characteristics. No differences (P < 0.05) were found for any measurements of resting left ventricular function. We conclude that upper body aerobic exercise training results in a specific left ventricular adaptation that is characterized by increased left ventricular wall thickness but no change in chamber dimension.

Physiologic limits of left ventricular hypertrophy in elite junior athletes: relevance to differential diagnosis of athlete's heart and hypertrophic cardiomyopathy

OBJECTIVES

The present study was undertaken to define physiologic limits of left ventricular hypertrophy in elite adolescent athletes.

BACKGROUND

Systematic sports training may cause increased left ventricular wall thickness (LVWT), creating uncertainty regarding the differential diagnosis of athlete's heart from hypertrophic cardiomyopathy (HCM). This distinction is crucial because HCM is responsible for about one-third of all sudden deaths in young athletes. Echocardiographic data defining athlete's heart are limited largely to adults, with little information specifically in adolescent athletes (14 to 18 years old), for whom the risk of sudden death from HCM is highest.

METHODS

Seven hundred and twenty elite adolescent athletes (75% male) aged 15.7 +/- 1.4 years participating in ball, racket, and endurance sports and 250 healthy sedentary controls of similar age, gender, and body surface area underwent echocardiography.

RESULTS

Compared with controls, athletes had greater absolute LVWT (9.5 +/- 1.7 mm vs. 8.4 +/- 1.4 mm; p < 0.0001). Maximal LVWT exceeded predicted upper limits in 38 athletes (5%); however, no female athlete had a LVWT >11 mm and only three trained male athletes had absolute LVWT >12 mm (0.4%). Each of the 38 athletes with a LVWT exceeding predicted limits also showed enlarged left ventricular cavity dimension (54.4 +/- 2.1 mm; range 52 to 60 mm).

CONCLUSIONS

Trained adolescent athletes demonstrated greater absolute LVWT compared with nonathletes. Only a small proportion of athletes exhibited a LVWT exceeding upper limits, very rarely >12 mm, and then always with chamber enlargement. Hypertrophic cardiomyopathy should be considered strongly in any trained adolescent male athlete with LVWT >12 mm (females >11 mm) and nondilated left ventricle.

Heart size estimated by echocardiography correlates with maximal oxygen uptake

Maximum oxygen uptake also appears to correlate to athletic performance in horses. In the Thoroughbred industry, there has long been an empirical theory that heart size is related to athletic performance, despite a lack of scientific evidence supporting this assertion. To investigate the relationship between peak oxygen consumption (VO2max) and cardiac size measured by echocardiography, guided M-mode and 2-dimensional echocardiography were performed in 17 conditioned Thoroughbreds with a range of VO2max from 126 to 217 ml/min/kg STPD (mean +/- s.d. 158 +/- 28 m/min/kg). Horses were age 2-10 years and weighed 430-510 kg. Echocardiography was performed using a Vingmed System V echocardiograph with a 2.25 MHz phased array ultrasound transducer. All images were obtained from the right hemithorax using a short axis view of the left ventricle (LV) at the level of the chordae tendinae. All horses were free from significant regurgitation at the aortic or mitral valves. Maximal oxygen uptake was measured during a standardised incremental treadmill exercise test to fatigue. Maximal oxygen uptake was correlated significantly with LVIDd (r = 0.71; P = 0.001), MWT (r = 0.72; P = 0.001), LV mass (r = 0.78; P = 0.0002) and LV short-axis area (r = 0.69; P = 0.003). When indices of heart size were indexed to bodyweight, the correlation between VO2max and indices of heart size were LVIDd (r = 0.57; P = 0.01), MWT (r = 0.44; P = 0.07), LV mass (r = 0.78; P = 0.0002) and LV short-axis area (r = 0.69; P = 0.003). The current study suggests there is a strong relationship between VO2max and measurements of left ventricular size in Thoroughbred horses when individuals with a range of VO2max are compared.

Peak aerobic performance and left ventricular morphological characteristics in university students

OBJECTIVE

To determine whether a relationship exists between left ventricular morphology and aerobic capacity in large numbers of male university students with a physically inactive and active life style.

DESIGN

A prospective study.

SETTING

Sports medicine research center.

PARTICIPANTS

Eleven sedentary normal-weight university students, 17 sedentary overweight university students, and 215 university athletes.

MAIN OUTCOME MEASURES

After the echocardiographic examination, an incremental treadmill exercise test until exhaustion was performed to measure peak oxygen uptake (VO2).

RESULTS

In sedentary students, absolute peak VO2 in the overweight students was slightly higher than that in normal-weight students (3,024 vs. 2.912 ml/min). Relative peak VO2 (ml/min/kg) was highly negatively correlated with body mass index (kg/m2) in a total of 28 sedentary students. The correlation between absolute peak VO2 and left ventricular dimension was weak in the sedentary overweight students; however, a correlation coefficient of 0.55 was obtained in athletic students. A stepwise multiple regression showed significant determinants of absolute peak VO2 in athletic students for body surface area (45%), left ventricular dimension (7%), and certain sports (6%).

CONCLUSIONS

A physically active life style plays a role in increasing both aerobic capacity and left ventricular enlargement. Body size appeared to be a potent stimulus to left ventricular enlargement.

The athlete's heart. A meta-analysis of cardiac structure and function

BACKGROUND

It has been postulated that depending on the type of exercise performed, 2 different morphological forms of athlete's heart may be distinguished: a strength-trained heart and an endurance-trained heart. Individual studies have not tested this hypothesis satisfactorily.

METHODS AND RESULTS

The hypothesis of divergent cardiac adaptations in endurance-trained and strength-trained athletes was tested by applying meta-analytical techniques with the assumption of a random study effects model incorporating all published echocardiographic data on structure and function of male athletes engaged in purely dynamic (running) or static (weight lifting, power lifting, bodybuilding, throwing, wrestling) sports and combined dynamic and static sports (cycling and rowing). The analysis encompassed 59 studies and 1451 athletes. The overall mean relative left ventricular wall thickness of control subjects (0.36 mm) was significantly smaller than that of endurance-trained athletes (0.39 mm, P=0.001), combined endurance- and strength-trained athletes (0.40 mm, P=0.001), or strength-trained athletes (0.44 mm, P<0.001). There was a significant difference between the 3 groups of athletes and control subjects with respect to left ventricular internal diameter (P<0. 001), posterior wall thickness (P<0.001), and interventricular septum thickness (P<0.001). In addition, endurance-trained athletes and strength-trained athletes differed significantly with respect to mean relative wall thickness (0.39 versus 0.44, P=0.006) and interventricular septum thickness (10.5 versus 11.8 mm, P=0.005) and showed a trend toward a difference with respect to posterior wall thickness (10.3 versus 11.0 mm, P=0.078) and left ventricular internal diameter (53.7 versus 52.1 mm, P=0.055). With respect to cardiac function, there were no significant differences between athletes and control subjects in left ventricular ejection fraction, fractional shortening, and E/A ratio.

CONCLUSIONS

Results of this meta-analysis regarding athlete's heart confirm the hypothesis of divergent cardiac adaptations in dynamic and static sports. Overall, athlete's heart demonstrated normal systolic and diastolic cardiac functions.

The morphologic consequences of systemic training

The development of echocardiography in the 1970s led to the flourishing of the study of the athlete's heart. From the earliest studies, it was apparent that athletes develop enlargement of the left ventricular cavity and thickening of myocardium in response to prolonged repetitive training. The changes in echocardiographic measurements are small and often within quoted normal ranges. By comparison to sedentary controls, however, left ventricular end-diastolic dimension is increased by approximately 10%, posterior wall dimension by 15% to 20%, and calculated mass by up to 45%.

Impact of different sports and training on cardiac structure and function

There is overwhelming evidence, particularly from echocardiography, that the heart of competitive athletes may differ from that of nonathletes, matched for age, gender, and body size. A larger left ventricular mass has been shown in athletes performing predominantly dynamic aerobic and anaerobic sports, in athletes engaged in static training, and in players of ball sports. Enlargement of the left ventricular internal diameter was most pronounced and reached about 10% in athletes performing predominantly dynamic sports; mainly strength training athletes had a lesser increase of the internal dimension, which was limited to 2.5%. Also the left ventricular wall appeared to be thickened in all types of athletes compared with controls. In sports with high dynamic and low static demands, wall thickness was proportionate or slightly disproportionate to the size of the internal diameter so that relative wall thickness was not different from controls or slightly increased (predominantly eccentric hypertrophy). In strength athletes, the disproportionate increase of wall thickness averaged about 12% (predominantly concentric hypertrophy). In sports with high dynamic and high static demands and requiring prolonged training, such as cycling, the increases of absolute and relative wall thickness reached 29% and 19% and were more pronounced than in runners (mixed hypertrophy). A plausible interpretation of these results is that the development of so-called eccentric or concentric left ventricular hypertrophy according to the type of sports cannot be regarded as an absolute or dichotomous concept because training regimens and sports activities are not exclusively dynamic or static and because the load on the heart is not purely of the volume or the pressure type. Most studies agree that left ventricular systolic and diastolic function is normal in the athlete at rest, whereas diastolic function seems to be enhanced in the exercising endurance athlete. The consistency of the results of studies on athletes in the competitive and the resting season, of training of sedentary subjects, and of spinal cord-injured patients suggests that variations in physical activity can alter left ventricular structure; genetic factors do not seem to be involved in the size of the left ventricular internal diameter but have to be taken into account to interpret wall thickness.

Echocardiographic criteria of physiological left ventricular hypertrophy in combined strength- and endurance-trained athletes

In combined strength- and endurance-trained athletes who are showing both unusual large body dimensions as well as a high physical fitness, the dimensions of the 'athlete's heart' are expected to reach physiological limits. Therefore we investigated 75 male and 77 female competitive rowers by means of doppler-echocardiography. The absolute "critical" heart weight of 500 g was exceeded by 61% of the male and 10% of the female rowers. Maximal values of the left ventricular (LV) muscle mass were measured at 170 (men) and 133 (women) g.m-2 body surface area, respectively. The LV end-diastolic internal diameter was measured to be above the upper clinical limit of 55 mm in 55% of the male and 17% of the female rowers. A LV wall thickness of 13 and 12 mm was only exceeded by 3 male and 1 female athlete, respectively (maximal values: 14 and 12.5 mm). The LV wall/internal diameter ratio did not exceed 48-50%. The systolic LV function as well as ECG and blood pressure did not reveal any pathological finding, the diastolic LV function was always measured within the normal range. The LV wall thicknesses, internal diameter and hypertrophic index (relation between wall thickness and internal diameter) of the rowers were significantly higher than those of 62 non-endurance trained athletes (pairwise matched according to the body dimensions) and similar to 28 male 'pure' endurance athletes (pairwise matched according to the absolute heart volume). In conclusion, upper limits of echocardiographic volume measurements that are considered critical may be clearly exceeded by healthy strength-endurance trained athletes with simultaneously high body dimensions. The clinical limits, however, are still valid in subjects with a body mass up to approximately 70 kg. The LV wall thickness only exceptionally exceed the clinical limits. A specific influence of the strength elements in training on the LV hypertrophy had not be found.

Seasonal variation in fitness parameters in competitive athletes

In many sports, training for successful competition has become virtually a year-round endeavour. To assist in better preparation, a competitor's year may be divided into phases such as off-season and in-season, indicating reduced or increased competition commitments, respectively. A number of studies have described the effects of seasons or periods of competition, training, detraining and reduced training on aspects of physical fitness. Depending on performance level, the type of sport and the fitness parameter in question, the swings in fitness variables reported may be as high as 18% from one season to another. In elite competitors, anaerobic parameters, heart frequencies, subcutaneous fat, flexibility and haemoglobin levels remain relatively unchanged throughout the year. Aerobic metabolism and muscular strength may demonstrate noticeable (mostly unfavourable) changes, and plasma hormonal levels normally follow changes in training intensities. Aspects related to long term fatigue and genetics, and to appropriate training are just a few explanations for these observations. It is still not known whether greater fitness gains attainable with longer off-season training programmes can be successfully maintained over the duration of the competition season. However, the consensus would seem to be that specialised training (based on technique and competition tactics only) is inadequate for fitness maintenance and/or improvements. This is perhaps supported by the general trends found in the literature regarding muscular strength: while supervised off-season conditioning programmes may result in significant improvements for both recreational and competitive athletes, no such changes are normally observed after competition seasons. These findings may reflect, amongst other factors, a lack of optimal training intensity to bring about strength increases during in-season periods. In novices and in athletes at low competitive levels, training seasons may lead to considerable functional improvements of the cardiorespiratory system, coupled with occasional increases in muscular strength and decreases in body fat. Relatively low fitness levels at the beginning of training have been put forward as an explanation for these improvements. Seasons of training and competition result in no significant changes in flexibility measurements. Similar changes to those found in novices and in athletes at low competitive levels may also be seen in children and adolescents engaged in sport, although their fitness improvements are consistent with normal patterns of growth and development. No differences have been identified between male and female athletes participating at different competition levels.

Morphology of the "athlete's heart" assessed by echocardiography in 947 elite athletes representing 27 sports

In the present study, we used echocardiography to investigate the morphologic adaptations of the heart to athletic training in 947 elite athletes representing 27 sports who achieved national or international levels of competition. Cardiac morphology was compared for these sports, using multivariate statistical models. Left ventricular (LV) diastolic cavity dimension above normal (> 54 mm, ranging up to 66 mm) was identified in 362 (38%) of the 947 athletes. LV wall thickness above normal (> 12 mm, ranging up to 16 mm) was identified in only 16 (1.7%) of the athletes. Athletes training in the sports examined showed considerable differences with regard to cardiac dimensions. Endurance cyclists, rowers, and swimmers had the largest LV diastolic cavity dimensions and wall thickness. Athletes training in sports such as track sprinting, field weight events, and diving were at the lower end of the spectrum of cardiac adaptations to athletic training. Athletes training in sports associated with larger LV diastolic cavity dimensions also had higher values for wall thickness. Athletes training in isometric sports, such as weightlifting and wrestling, had high values for wall thickness relative to cavity dimension, but their absolute wall thickness remained within normal limits. Analysis of gender-related differences in cardiac dimensions showed that female athletes had smaller LV diastolic cavity dimension (average 2 mm) and smaller wall thickness (average 0.9 mm) than males of the same age and body size who were training in the same sport.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological and biomechanical aspects of rowing. Implications for training

The drag force on a racing shell increases with the square of velocity corresponding to a 3.2 power increase in energy expenditure. However, the metabolic cost increases with only an approximately 2.4 power function of shell velocity. During international races the metabolic cost corresponds to an oxygen uptake of 6.7 to 7.0 L/min over 6.5 min. The relative anaerobic contribution to 6.5 min of 'all-out' rowing has not been determined but is estimated to range from 21 to 30%. Because of the large muscle mass involved in rowing, blood variables reach extreme values: adrenaline 19 nmol/L; noradrenaline 74 nmol/L; pH 7.1; and bicarbonate 9.8 mmol/L. Because of the static component of the rowing stroke at the catch, blood pressure increases to near 200mm Hg, and the heart of oarsmen has adapted to this load by increasing wall thickness and internal diameters. The maximal oxygen uptake of oarsmen may reach 6.6 L/min and ventilation 243 L/min. Arterial oxygen tension decreases by 20mm Hg during 'all-out' rowing corresponding to a decrease in pulmonary diffusion capacity. A force of approximately 800 to 900N is developed on the oar. Force generation during rowing is relatively slow, 0.3 to 0.4 sec. Oarsmen are strongest in low velocity movement with 70 to 75% slow twitch fibres in skeletal muscle. Data indicate that rowing technique and training may improve explaining why results become approximately 0.7 sec faster per year.

Effects of 4 weeks endurance training on cardiac left ventricular structure and function

1. The effect of 4 weeks of moderate exercise training on cardiac left ventricular structure and function was examined by repeated echocardiographic/Doppler examination in 10 previously sedentary volunteers participating in a single blind, sedentary phase controlled, cross-over study. 2. Left ventricular internal diastolic diameter increased after 4 weeks of training from 4.98 to 5.11 cm with a further increase to 5.24 cm after 2 weeks of detraining (s.e.d. 0.05 cm, P < 0.01). These increases were still significant after adjustment for heart rate which fell from a pretraining average of 67.0-59.9 beats/min after 4 weeks of training. 3. There were no significant changes in systolic diameter or function and left ventricular wall thicknesses were unchanged during training, but were thinned after 2 weeks subsequent detraining. 4. The ratio of early to late transmitral filling velocity (E/A ratio) was significantly increased by training. Although E/A ratio was shown to be heart rate sensitive, training effects were still evident after adjustment for heart rate. 5. These changes in left ventricular volumes and function may contribute to the cardiovascular reflex changes previously shown to be produced by identical training programmes.

Echocardiographic findings in strength- and endurance-trained athletes

Assessment of echocardiographic measurements in athletes should take into account the specific sport and the quantity and quality of training. In addition, values corrected for body dimensions, especially the active body mass, should be used rather than absolute values. All parts of the athlete's heart are enlarged and its performance increases. Highly trained endurance athletes show the most enlarged hearts. Athlete's heart can be observed in athletes of all ages including the young. However, it is rarer than generally assumed. To differentiate between physiological and pathological myocardial changes, the relationship between heart size and ergometric performance as well as the echocardiographically measured ratio between left ventricular (LV) myocardial thickness and volume are useful; the latter remains unchanged, on the whole, in endurance- and strength-trained athletes. Concentric hypertrophy cannot be induced by strength training alone; additional factors, such as hypertension, aortic stenosis, cardiomyopathy or anabolic steroid use can play an important role. When corrected for body dimensions, non-endurance-trained, e.g. strength-trained, athletes have standard heart sizes even if considerable time is devoted to training. Findings in healthy untrained persons with large body dimensions also indicate no significant difference between the increase of echocardiographic measures caused by training and that caused by growth. An LV myocardial thickness of 13mm is seldom exceeded even in the highly endurance-trained or anabolic drug-free strength trained athletes under physiological conditions. However, the echocardiographic differentiation of cardiomyopathy can be difficult if an individual is highly trained and has large body dimensions. In such cases, LV end-diastolic diameter may be up to 66 to 70mm. The upper normal value of LV muscle mass is 170 g/m2 for a physiological heart enlargement. Future areas of investigation should include: adaptative changes; of the right ventricle; differences in the regression of the athlete's heart after cessation of training; the differentiation between echocardiographic changes; in highly endurance-trained or combined strength-endurance-trained persons and pathological changes; the importance of heart size and endurance sports performance; and finally the influence of genetic factors.

The 'athletic heart syndrome'. A critical review

Cardiological findings in athletes are often similar to those observed in clinical cases. Electrocardiographic and cardiac imaging abnormalities as well as physical findings may be the same in both of these groups. Bradycardia and rhythm disturbances are the most common abnormalities in athletes. Most athletes with abnormal electrocardiograms are asymptomatic and numerous investigators have failed to detect heart disease in association with such electrocardiograms. In contrast to cardiac dysfunction observed in clinical cases, enhanced or normal ventricular systolic and diastolic function have been reported in athletes. In endurance athletes, this is associated with very high values for maximal aerobic power (VO2max). Absolute and body size-normalised cardiac dimensions in most athletes do not approach values from chronic disease states, and may not exceed echocardiographic normal limits. In addition, pathological and physiological enlargement appear to be biochemically and functionally different. Myosin ATPase enzyme expression and calcium metabolism are different in rats with pathologically or physiologically induced enlargement. The reported biochemical differences underlie systolic and diastolic dysfunction in pathological enlargement. Conversely, trained rodents and humans have demonstrated enhanced systolic and diastolic function. It is important to note that cardiac enlargement observed in athletes is the result of normal adaptation to physical conditioning and/or hereditary influences. Conversely, pathological changes result from disease processes which can lead in turn to reduced function, morbidity and mortality. Since the mid 1970s echocardiography has been used to compare cardiac dimensions in male endurance- and resistance-trained athletes. A sport-specific profile of eccentric and concentric enlargement has been documented in endurance and resistance athletes, respectively. Subsequent studies of athletes have examined factors such as age, sex and degree of competitive success to determine their contribution to these sport-specific cardiac profiles. Unique athletic subgroups have also been analysed and have included ballet dancers, rowers, basketball players and triathletes. However, there is a paucity of data on cardiac dimensions in female athletes. Finally, physical conditioning studies have also examined echocardiographic dimensions before and after endurance and resistance training. Significant enlargement of internal dimensions, wall thickness or left ventricular mass have been reported but such increases are relatively small and by no means universal. Several conflicting explanations for enlarged cardiac dimensions appear in the literature. Chronic volume and pressure haemodynamic overloading during physical conditioning has been proposed to explain eccentric and concentric cardiac enlargement in endurance- and resistance-trained athletes respectively. However, twin studies suggest that hereditary factors may be important determinants of cardiac dimensions and/or the degree of cardiac adaptability to physical conditioning.(ABSTRACT TRUNCATED AT 400 WORDS)

The upper limit of physiologic cardiac hypertrophy in highly trained elite athletes

BACKGROUND

In some highly trained athletes, the thickness of the left ventricular wall may increase as a consequence of exercise training and resemble that found in cardiac diseases associated with left ventricular hypertrophy, such as hypertrophic cardiomyopathy. In these athletes, the differential diagnosis between physiologic and pathologic hypertrophy may be difficult.

METHODS

To address this issue, we measured left ventricular dimensions with echocardiography in 947 elite, highly trained athletes who participated in a wide variety of sports.

RESULTS

The thickest left ventricular wall among the athletes measured 16 mm. Wall thicknesses within a range compatible with the diagnosis of hypertrophic cardiomyopathy (greater than or equal to 13 mm) were identified in only 16 of the 947 athletes (1.7 percent); 15 were rowers or canoeists, and 1 was a cyclist. Therefore, the wall was greater than or equal to 13 mm thick in 7 percent of 219 rowers, canoeists, and cyclists but in none of 728 participants in 22 other sports. All athletes with walls greater than or equal to 13 mm thick also had enlarged left ventricular end-diastolic cavities (dimensions, 55 to 63 mm).

CONCLUSIONS

On the basis of these data, a left-ventricular-wall thickness of greater than or equal to 13 mm is very uncommon in highly trained athletes, virtually confined to athletes training in rowing sports, and associated with an enlarged left ventricular cavity. In addition, the upper limit to which the thickness of the left ventricular wall may be increased by athletic training appears to be 16 mm. Therefore, athletes with a wall thickness of more than 16 mm and a nondilated left ventricular cavity are likely to have primary forms of pathologic hypertrophy, such as hypertrophic cardiomyopathy.

ECG variants and cardiac arrhythmias in athletes: clinical relevance and prognostic importance

These findings permit the following conclusions on cardiac changes induced by high-performance sports and high levels of training. Sinus bradycardia and AV block can frequently be observed in athletes, but they do not require attention as long as they are asymptomatic or do not produce pauses exceeding 4 seconds. Persistent rather than transient second-degree AV block or Mobitz second- or third-degree AV block is an extremely unusual finding even in athletes and should be considered a sign of organic lesions until proved otherwise. Supraventricular and AV node ectopic beats are not more frequent in athletes than in the general population except for atrial fibrillation. WPW syndrome is of particular importance, since rapid conduction to the ventricle via the accessory AV pathway is possible, especially if there is a tendency toward atrial fibrillation. Likewise caution is required in athletes with hypertrophic cardiomyopathy. Here hemodynamic deterioration must be anticipated with the occurrence of supraventricular tachycardia. Simple ventricular arrhythmias occur among athletes with the same frequency as in the general population, but they usually disappear with exercise. The occurrence of complex ventricular forms of arrhythmia should always prompt cardiologic examination in search of underlying cardiac disease, particularly hypertrophic or dilated cardiomyopathy. The presence of ventricular arrhythmias without evidence of underlying heart disease does not indicate a special or increased risk of sudden cardiac death. A higher incidence of right and/or left ventricular hypertrophy, exercise-reversible ST elevation, and exercise-reversible changes in T waves (T negativity, sharp and/or excessive T waves) can be considered physiologic changes in the ECGs of athletes. These changes correlate closely with the type of sports activity and degree of training and are reversible when the activity is stopped. Horizontal ST segment depression are by contrast very rare in athletes and should always be clarified by cardiologic examination. Exercise-induced sudden cardiac death in athletes is unusual without preexisting heart disease. The cause of sudden cardiac death among athletes less than 40 years of age can be predominantely ascribed to congenital heart diseases (such as hypertrophic cardiomyopathy or coronary anomalies). In athletes more than 40 years of age and with increasing age, coronary heart disease is the most frequent autopsy finding. A corresponding risk stratification should take these partial dangers into account.

The veteran athlete: an echocardiographic comparison of veteran cyclists, former cyclists and non-athletic subjects

To determine the effects of prolonged endurance training on the heart, a comparison was made of veteran cyclists aged 41-51 years, former cyclists, and non-athletic subjects, including echocardiography, ECG, systolic and diastolic time intervals, and maximal oxygen uptake. The veterans had significantly larger diastolic diameter, systolic diameter, thickness of septum, posterior wall, and left ventricular mass. The enlargement of the left ventricle was found to be proportionate, as the ratio of diastolic diameter to wall thickness showed no change. In contrast to earlier reports, no indication of reduced cardiac function was found in the veterans, as echocardiographically measured function parameters, systolic, and diastolic time intervals were similar in the three groups. In the former athletes, whose previous training experience was similar to that of the veterans, no significant variation in cardiac structure and function was found in relation to the control group. This indicates that the physiological hypertrophy caused by physical training can be reversible.

Assessment of stiffness of the hypertrophied left ventricle of bicyclists using left ventricular inflow Doppler velocimetry

Sixteen male bicyclists and 16 control subjects were studied to assess whether the left ventricular hypertrophy of athletes is associated with changes in diastolic left ventricular function. The cyclists had a larger left ventricular internal diameter on echocardiography (55.2 versus 47.9 mm; p less than 0.001) and a disproportionate increase in wall thickness relative to the internal diameter (0.48 versus 0.41; p less than 0.01), indicating a mixed eccentric-concentric type of hypertrophy. Left ventricular inflow Doppler velocimetry showed similar results in athletes and control subjects for peak flow velocities in the atrial contraction phase (30 versus 32 cm/s; p = NS) and in the early diastolic rapid filling phase (71 versus 67 cm/s; p = NS). The similar ratio of both velocities, that is, 0.43 in the cyclists and 0.49 in the control subjects, suggests that left ventricular distensibility is unaltered in cyclists. It is concluded that the left ventricular hypertrophy observed in cyclists is not associated with changes in ventricular stiffness, as estimated from left ventricular inflow Doppler velocimetry.

Structural features of the athlete heart as defined by echocardiography

The morphologic concepts of the "athlete heart" have been enhanced and clarified over the last 10 years by virtue of M-mode echocardiographic studies performed on more than 1,000 competitive athletes. Long-term athletic training produces relatively mild but predictable alterations in cardiac structure that result in an increase in calculated left ventricular mass. This increase in mass observed in highly trained athletes is due to a mild increase in either transverse end-diastolic dimension of the left ventricle or left ventricular wall thickness, or both. Cardiac dimensions in athletes compared with matched control subjects show increases of about 10% for left ventricular end-diastolic dimension, about 15 to 20% for wall thickness and about 45% for calculated left ventricular mass. Furthermore, there is evidence that the modest degree of "physiologic" left ventricular hypertrophy (both the cavity dilation and wall thickening) observed in athletes is dynamic in nature, that is, it may develop rapidly within weeks or months after the initiation of vigorous conditioning and may be reversed in a similar time period after the cessation of training. Several echocardiographic studies also suggest that the precise alterations in cardiac structure associated with training may differ depending on the type of athletic activity undertaken (that is, whether training is primarily dynamic [isotonic] or static [isometric]). Although the ventricular septal to free wall thickness ratio (on M-mode echocardiogram) is almost always within normal limits (less than 1.3), occasionally an athlete will show mild asymmetric thickening of the anterior basal septum (usually 13 to 15 mm). This circumstance may mimic certain pathologic conditions characterized by primary left ventricular hypertrophy such as nonobstructive hypertrophic cardiomyopathy. The long-term significance of increased left ventricular mass in trained athletes has not been conclusively defined. However, there is no evidence at this time suggesting that this form of hypertrophy is itself deleterious to the athlete or predisposes to (or prevents) the natural occurrence of cardiovascular disease later in life.

Physiological left ventricular hypertrophy

Echocardiograms were recorded in 154 active athletes (from various sports) and 21 ex-athletes and compared with those in 40 normal control subjects (non-athletes). Diastolic cavity dimension and posterior wall and septal thickness were measured and left ventricular mass and the ratio of posterior wall thickness to cavity radius and of septum to posterior wall thickness calculated. As a group athletes had a significantly increased diastolic cavity dimension, posterior wall and septal thickness, and left ventricular mass. The ratio of posterior wall thickness to cavity radius was distributed as a single continuous variable with a significantly increased mean, and there was no separate subgroup of shot putters or weight lifters with inappropriate hypertrophy. The mean ratio of septum to posterior wall thickness was normal, but there was a wide range of values up to 2.1:1. Ex-athletes had entirely normal left ventricular dimensions and wall thickness. When athletes are categorised by their standard of competition national standard competitors had a significantly increased posterior wall and septal thickness and left ventricular mass compared with university and non-competitive sportsmen. In conclusion, strenuous activity results in left ventricular hypertrophy which is appropriate to the body size of the athlete and the degree of activity but not to its type.

Effect of training on left ventricular structure and function. An echocardiographic study

To study the cardiac effects of running, 15 healthy non-athletic male volunteers underwent a moderate training schedule for six weeks; thereafter five continued to run at a similar intensity for a further six weeks and 10 stopped. Left ventricular wall thickness and dimension, relaxation, and diastolic function were studied by digitised echocardiography at entry and at two, four, and six weeks, and again at 12 weeks. Significant increases in running ability and maximum oxygen consumption were observed. Maximum oxygen consumption was unchanged in those who continued to run but a reduction was noted in those who stopped. No significant changes in left ventricular dimensions were observed, but the thickness of the posterior wall and the septum increased during six weeks' running. Left ventricular mass (cube volume formula) increased significantly during the first six weeks. Comparison of those who continued to train and those who stopped showed that the former had no change in mass, whereas in the latter mass returned towards pre-exercise values. Systolic function (fractional shortening) was unchanged throughout the study. In addition, no abnormalities of relaxation or diastolic function were detected. Exercise induced left ventricular hypertrophy may develop rapidly during training and the increased myocardial mass resulting from six or 12 weeks' running is not associated with impaired relaxation and diastolic function as found in pathological forms of hypertrophy.

Electrocardiographic changes after physical training in patients with myocardial infarction

Electrocardiographic voltage measurements were performed in 24 men with an inferior myocardial infarction before and after 14 +/- 0.5 weeks of physical training. Oxygen uptake at peak exercise increased 42% and heart rate at rest was significantly decreased after training. Increases were found in the magnitude of the R waves in leads II, aVF and V4 to V6; of the S wave in leads V1 and V3; of the T waves in V5 and V6; and of the Sokolow index of QRS voltage. Also, the magnitude of the mean electrical vector in the frontal plane was significantly higher after training. These data were compared with those derived from two electrocardiographic tracings, separated by an average of 19 +/- 1.5 weeks, of 20 other patients with an inferior myocardial infarction who were comparable in age, weight, risk factor and delay between infarction and first examination, but who were not trained. When the electrocardiographic changes between the two observations were compared for the two groups, the trained patients show significant increases in the magnitude of the R wave in the left precordial leads, and leads II and aVF and the Sokolow voltage criterion; in the magnitude of the T wave in leads V5 and V6; and in the magnitude of the mean electrical vector in the frontal plane. It is concluded that physical training in patients with myocardial infarction can alter cardiac structure, as evaluated by voltage measurements on the electrocardiogram.