Exercise-induced cardiac hypertrophy. Fact or fallacy?

After a century of research reports, the notion of exercise-induced cardiac hypertrophy is still an expected adaptation to regular exercise training. Experimental evidence reported both in animals and in humans over the past 3 decades suggests, however, that this conclusion may not be totally warranted. Data from 20 years of echocardiographic investigations of athletes and nonathletes indicate that differences in cardiac dimensions are not very large. Cross-sectional comparisons of over 1000 athletes and roughly 800 control individuals indicate an average difference of 1.6 mm in left ventricular (LV) wall thickness and of 5.3 mm in end-diastolic diameter. Differences reported after training programmes lasting 4 to 52 weeks are even smaller, with average increases of 0.3 mm in LV wall thickness and only 2.1mm in end-diastolic diameter. This article reviews data from animal and human studies concerning cardiac morphology and exercise training to show that the traditional interpretation of the literature has failed to take into account several methodological considerations or factors that may act as confounders in the interpretation of data. Results from animal studies indicate that the observation of cardiac hypertrophy is equivocal at best. In many reports the reported changes in heart size are not significant, and in instances where significant changes are reported these may be seen to be confounded by a number of factors. For example, in rats the reported training-induced hypertrophy may be related to gender differences in the responsiveness of cardiac dimensions or body and/or organ growth rather than to true heart hypertrophy. Furthermore, the interpretation of results from training studies in rats has often been based on the assumption that the metabolic, haemodynamic and thermoregulatory requirements of swimming and running exercise in rats are similar, which may in fact not be the case. In addition, the use of the heart weight/body weight ratio as an index of cardiac hypertrophy, although widespread in animal studies, is open to criticism owing to failure to control for concurrent changes in body weight. Several methodological considerations and factors confounding the outcome of exercise training in humans have also been omitted when interpreting echocardiographic cross-sectional and longitudinal findings. For example, in adult echocardiography the practical resolution of the echocardiographic technique amounts to roughly 2.2mm. It follows, therefore, that unless differences of changes in cardiac dimensions exceed the limit of resolution they are meaningless although statistically significant.(ABSTRACT TRUNCATED AT 400 WORDS)

An on-site test battery to evaluate giant slalom skiing performance.

The purpose of this study was to determine if an on-site test battery would distinguish among three levels of giant slalom skiing ability. The test battery consisted of a 20-m shuttle run test, Wingate 60s cycling test, hexagonal obstacle test, high box test, double leg jumping test and vertical jump test. These tests were selected since previous studies have identified aerobic endurance, anaerobic endurance, power and agility as important components for Alpine skiers. Both construct validity and criterion related validity of the test battery were examined using data from 11 club skiers, 14 divisional level skiers, and 9 provincial level skiers. To establish construct validity, univariate F tests examined differences among the three levels of skiers. Significant (P less than 0.05) differences were found between the club skiers and the better skiers (divisional and provincial level) for the following test variables: peak power, mean power, and post-exercise lactate for a 60s Wingate cycle ergometer test, high box test, hexagonal obstacle test, double leg jumping test, and shuttle run test. Criterion related validity was established since there were significant correlations between giant slalom performance time and the hexagonal obstacle test (r = 0.82), high box test (r = -0.80), and double leg jumping (r = -0.86). These data illustrate that an on-site test battery can be used to distinguish among giant slalom Alpine skiers.

Recoil effect of the ice hockey stick during a slap shot.

The purpose of this study was to examine the "recoil" effect of the ice hockey stick shaft during a stationary slap shot. Nine male adult subjects (four elite and five recreational) were tested. Their performances were evaluated by simultaneously recording stick movement and internal bending from high-speed digital video (1,000 Hz) and puck acceleration from a triaxial accelerometer positioned inside the puck. In addition, an electrical circuit measured blade-puck contact time. Data were analyzed with a one-way MANOVA for several dependent variables, including final puck velocity, puck acceleration, maximum stick shaft bending (angle and distance deflection), stick shaft angular velocities, blade-puck contact time, and corresponding time events. The results indicate the following. First, blade-puck contact time was greater for the elite than for recreational players (38 +/- 9 ms and 27 +/- 5 ms); however, measures for puck acceleration were essentially the same (63.8 g +/- 9.9 and 61.8 g +/- 19.5). Two, the elite players were able to generate greater puck velocities (120 +/- 18 km/h and 80.3 +/- 11.6 km/h). Three, the recoil timing was found to be reater for elite players (59.8% of blade-puck contact).

Time dependent response of cardiac myofibrillar ATPase activity to exercise.

1. The purpose of the present study was to investigate the time course of run training effects on the Ca2+ kinetics of the cardiac myofibrillar ATPase activity in female Sprague-Dawley rats. 2. The cardiac myofibrillar ATPase activity was measured at varying Ca2+ levels, and the Hill-n and pCa50 were measured in the hearts of rats after 3, 6 and 9 weeks of running training with a training program that began with an initially high intensity (HINT) and a training program with a more progressive increase in intensity (PROG). 3. After 3 and 6 weeks of training cardiac myofibrillar ATPase activity in the hearts of the trained rats in both training programs was elevated by 28-40% over the control group (P less than 0.05) at a pCa5 but was not different from the control groups after 9 weeks of training (P greater than or equal to 0.05). 4. Also the Ca2+ co-operativity as measured by the Hill-n was elevated in the hearts of the trained rats after 6 and 9 weeks of training when compared to control groups suggesting changes in the regulatory proteins of the myofibrils of hearts from trained rats. 5. The elevations in cardiac myofibrillar ATPase activity suggest that the myocardium responded to the training stimulus in a phasic manner. 6. The regression of cardiac myofibrillar ATPase in the late weeks of training might be related to a reduction or a loss of a specific training stimulus for the myocardium.

Biochemical adaptation of cardiac and skeletal muscle to physical activity.

1. Female Wistar rats were randomly assigned to control (C) or exercising (T) groups and subsequently portioned into 1, 3, 5 and 10 day T and C groups. The T groups completed a progressive endurance running program. Biochemical indices of adaptation were measured in cardiac muscle and in plantaris and soleus muscles of C and T animals after their last exercise bout. 2. In cardiac muscle, myofibrillar ATPase activity was significantly elevated in the 3T (0.241 +/- 0.031) and 5T (0.242 +/- 0.013) groups (P less than or equal to 0.05) compared to their respective controls (3C = 0.187 +/- 0.015 and 5C = 0.190 +/- 0.007). 3. After 10 days of training cardiac myofibrillar ATPase activity was elevated by 17% but this was not significant (P greater than or equal to 0.05). 4. No changes in myofibrillar ATPase activity were seen in skeletal muscle (P greater than or equal to 0.05), however, hexokinase activity progressively increased and was significantly elevated in the 3T, 5T and 10T soleus and plantaris muscles of rats over controls (P less than or equal to 0.05). 5. Minimal nonsignificant changes were noted in the hexokinase activity of the hearts of all T groups (P greater than or equal to 0.05). 6. These results indicate that metabolic adaptation of the heart and skeletal muscles takes place after as little as three training sessions. 7. Although the adaptation of the skeletal muscles continually progresses, the adaptation of the heart appears to be transitory.(ABSTRACT TRUNCATED AT 250 WORDS)

Ca2+ activation properties of myofibrillar ATPase from fatigued rat plantaris.

1. Muscle fatigue following long-duration rhythmic activity is often characterized by reduced force following a single impulse and at low-frequencies of stimulation. 2. Although this response is generally attributed to an alteration in excitation-contraction coupling, the possibility that the responsiveness of myofibrillar proteins to a given Ca2+ signal is altered has never been ruled out. 3. In this study, rat plantaris muscles were subjected to an in situ regimen of contractions (100 Hz, lasting 100 msec, once every 750 msec, for 1 hr), and allowed to recover for 15 min. 4. Twitch, 100 Hz, and 200 Hz forces were reduced by 79%, 49% and 17% respectively, at this time. 5. In myofibrils isolated from these muscles, maximum activity of Ca2+ activated myofibrillar ATPase, Ca2+ sensitivity (pCa 50), and co-operatively (Hill n), were not different from non-fatigued muscles. 6. It appears, therefore, that the Ca2+ activation properties of myofibrillar ATPase do not contribute to this pattern of fatigue.

A test for the measurement of pulmonary diffusion capacity during high-intensity exercise.

The most commonly used technique for the measurement of pulmonary diffusing capacity (DL) is the single-breath hold technique requiring a 10-s breath-hold after the maximal inspiration of carbon monoxide (0.3% CO) and helium (10% He). To measure pulmonary diffusing capacity in our experiments, we had the added advantage of the use of the Gould Pulmonary Function Laboratory that automates the collection and recording of data and the calibration of equipment for each test. However, this technique, DL(CO), is difficult to use during exercise of moderate or elevated intensity because of the lengthy breath-hold. Thus, the purpose of the present study was to compare DL(CO) with 3-s and 5-s breath-holds to a 10-s breath-hold at rest and during moderate and intense exercise in 14 subjects. As expected, an increase in the DL(CO) was observed during moderate and intense exercise when compared to resting values (45.7 +/- 10.0 and 53.0 +/- 7.6 vs 32.1 +/- 7.7 ml CO min-1 mmHg-1). No difference was observed between values for DL(CO) measured at varying breath-hold times at rest (3 s: 32.9 +/- 7.4; 5 s: 32.0 +/- 7.5; 10 s: 31.4 +/- 8.2 ml CO min-1 mmHg-1) or during moderate exercise (3 s: 45.9 +/- 10.1; 5 s: 45.9 +/- 10.6; 10 s: 45.2 +/- 10.4 ml CO min-1 mmHg-1) or intense exercise (3 s: 52.1 +/- 8.3; 5 s: 54.3 +/- 9.3; 10 s: 52.6 +/- 5.2 ml CO min-1 mmHg-1). Reliability coefficients indicated that the use of a 3-s breath-hold was appropriate.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of skating economy on-ice and on the skating treadmill.

The purpose of this study was to compare skating economy and oxygen uptake (VO2) on-ice and on the skating treadmill (TM). Male varsity hockey players (n = 15, age = 21.0 yr) performed skating tests on a TM and on-ice. The subjects skated for 4 min at each of 3 submaximal velocities (18, 20, and 22 km . h(-1)), separated by 5 min of passive recovery. A VO2max test followed the submaximal tests and commenced at 24 km . h(-1) with the velocity increasing by 1 km . h(-1) every minute until volitional fatigue. VO2 was 39.7, 42.9, 46.0, and 53.4 ml . kg(-1) . min(-1) at 18, 20, 22, and maximum speed (km . h(-1)) on the TM. VO2 was significantly lower (p < .05) 31.5, 36.9, and 42.7 ml . kg(-1) . min(-1) at 18, 20, and 22 km . h(-1) on-ice. The on-ice VO2max (54.7 ml . kg(-1) . min(-1)) was similar to TM. Stride rate, stride length and heart rate (HR) were significantly different on-ice compared to TM. These results show that at submaximal velocities, VO2, HR, and stride rate are higher on TM compared to on-ice. VO2max was similar while HRmax was higher on the skating treadmill compared to on-ice

Acute effects of intense interval training on running mechanics.

The aims of this study were to determine if there are significant kinematic changes in running pattern after intense interval workouts, whether duration of recovery affects running kinematics, and whether changes in running economy are related to changes in running kinematics. Seven highly trained male endurance runners (VO2max = 72.3+/-3.3 ml x kg(-1) x min(-1); mean +/- s) performed three interval running workouts of 10 x 400 m at a speed of 5.94+/-0.19 m x s(-1) (356+/-11.2 m x min(-1)) with a minimum of 4 days recovery between runs. Recovery of 60, 120 or 180 s between each 400 m repetition was assigned at random. Before and after each workout, running economy and several kinematic variables were measured at speeds of 3.33 and 4.47 m x s(-1) (200 and 268 m x min(-1)). Speed was found to have a significant effect on shank angle, knee velocity and stride length (P < 0.05). Correlations between changes pre- and post-test for VO2 (ml x kg(-1) x min(-1)) and several kinematic variables were not significant (P > 0.05) at both speeds. In general, duration of recovery was not found to adversely affect running economy or the kinematic variables assessed, possibly because of intra-individual adaptations to fatigue.