Left Ventricular Structure and Function in Elite Swimmers and Runners

Sport-specific differences in the left ventricle (LV) of land-based athletes have been observed; however, comparisons to water-based athletes are sparse. The purpose of this study was to examine differences in LV structure and function in elite swimmers and runners. Sixteen elite swimmers [23 (2) years, 81% male, 69% white] and 16 age, sex, and race matched elite runners participated in the study. All athletes underwent resting echocardiography and indices of LV dimension, global LV systolic and diastolic function, and LV mechanics were determined. All results are presented as swimmers vs. runners. Early diastolic function was lower in swimmers including peak early transmitral filling velocity [76 (13) vs. 87 (11) cm ⋅ s-1, p = 0.02], mean mitral annular peak early velocity [16 (2) vs. 18 (2) cm ⋅ s-1, p = 0.01], and the ratio of peak early to late transmitral filling velocity [2.68 (0.59) vs. 3.29 (0.72), p = 0.005]. The diastolic mechanics index of time to peak untwisting rate also occurred later in diastole in swimmers [12 (10)% diastole vs. 5 (4)% diastole, p = 0.01]. Cardiac output was larger in swimmers [5.8 (1.5) vs. 4.7 (1.2) L ⋅ min-1, p = 0.04], which was attributed to their higher heart rates [56 (6) vs. 49 (6) bpm, p < 0.001] given stroke volumes were similar between groups. All other indices of LV systolic function and dimensions were similar between groups. Our findings suggest enhanced early diastolic function in elite runners relative to swimmers, which may be attributed to faster LV untwisting

The effect of creatine supplementation on the response of central and peripheral pulse wave velocity to high-intensity resistance exercise

Following a bout of high-intensity resistance exercise, a transient increase in arterial stiffness, as measured through central pulse wave velocity has been shown to occur. Preliminary creatine supplementation research has demonstrated the potential for creatine to alter select measures of arterial stiffness. This study examines whether creatine supplementation independently influences the resistance exercise response of both central and peripheral pulse wave velocity. Forty healthy participants completed a high-intensity knee extension protocol demonstrated to cause increases in pulse wave velocity, both before and after 7 days of supplementing with creatine (n = 21) or placebo (n = 19) at 21 g/day. Resting and post-exercise measures of blood pressure, central (immediately and 20 min post) and peripheral (25 min post) pulse wave velocity were collected. No significant difference in the response of central pulse wave velocity was observed between creatine or placebo supplementation (p < 0.05) following high-intensity resistance exercise, as both groups revealed increases from pre-exercise to immediately post-exercise (p < 0.01). Similarly, no differences between groups were apparent for the peripheral pulse wave velocity response to exercise (p = 0.4). The current evidence does not support creatine supplementation as an effective intervention for reductions in arterial stiffness occurring with resistance exercise

Comparison of measures using the first test of 15 leg extensions per leg between a gold standard dynamometer (Humac Norm) and two variations of a custom-built isokinetic dynamometer (1080 Quantum).

<p>Comparison of measures using the first test of 15 leg extensions per leg between a gold standard dynamometer (Humac Norm) and two variations of a custom-built isokinetic dynamometer (1080 Quantum).</p

Configuration of the 1080 Quantum attached to Model A leg extension.

<p>The power outputs (W) would be presented on the <b>A.</b> tablet, calculated from the <b>B.</b> 1080 Quantum. The participant would sit in the leg extension machine and kick the <b>C.</b> movement arm outwards to complete the leg extension. The <b>D.</b> range of motion apparatus was in place to suspend the extension, bringing the participant’s leg back to the neutral position to be prepared for subsequent extensions. Finally, the participant was secured with a <b>E.</b> harness.</p

Schematic timeline of experimental protocol.

<p>Warm-up of both legs was initiated before the exercise protocol of 15 maximal concentric leg extensions at an equivalent of 180° s^-1 on both legs at each visit. Repeated tests were performed on Model A and Model B, with a single test performed on the Humac Norm, separated by at least 48 hours.</p

Reliability of measures between two tests (pre and post) of 15 leg extensions per leg on two variations of a custom-built isokinetic dynamometer, the 1080 Quantum.

<p>Reliability of measures between two tests (pre and post) of 15 leg extensions per leg on two variations of a custom-built isokinetic dynamometer, the 1080 Quantum.</p

Testing a novel isokinetic dynamometer constructed using a 1080 Quantum

<div><p>This study sought to assess the reliability and comparability of two custom-built isokinetic dynamometers (Model A and Model B) with the gold-standard (Humac Norm). The two custom-built dynamometers consisted of commercially available leg extension machines attached to a robotically controlled resistance device (1080 Quantum), able to measure power, force and velocity outputs. Twenty subjects (14m/6f, 26±4.8yr, 176±7cm, 74.4±12.4kg) performed concentric leg extensions on the custom-built dynamometers and the Humac Norm. Fifteen maximal leg extensions were performed with each leg at 180° s^-1, or the linear equivalent (~0.5m s^-1). Peak power (W), mean power (W), and fatigue indexes (%) achieved on all three devices were compared. Both custom-built dynamometers revealed high reliability for peak and mean power on repeated tests (ICC>0.88). Coefficient of variation (CV) and standard error of measurement (SEM) were small when comparing power outputs obtained using Model A and the Humac Norm ( CV = 9.0%, SEM = 49W; peak CV = 8.4%, peak SEM = 49W). Whereas, Model B had greater variance ( CV = 13.3% SEM = 120W; peak CV = 14.7%, peak SEM = 146W). The custom-built dynamometers are capable of highly reliable measures, but absolute power outputs varied depending on the leg extension model. Consistent use of a single model offers reliable results for tracking muscular performance over time or testing an intervention.</p></div