Neuromuscular Impact of Acute Hypertrophic Resistance Loading with And Without Blood-Flow Restriction.

Exploring acute neuromuscular fatigue induced by different modalities of resistance exercise would help understand the adaptation subsequent to specific training programs. Therefore, we investigated the acute impact of high-intensity and low-intensity blood flow-restricted resistance exercise on the development of explosive torque throughout the torque-time curve. Seventeen healthy, young participants were included in a randomized, counterbalanced within-subjects design study, in which participants underwent two experimental conditions, separated by a 1-wk period. Low-intensity blood-flow restricted exercise and high-intensity resistance exercise were performed using dynamic elbow flexion at 20 and 75% of 1 repetition maximum, respectively. Maximal voluntary contraction (MVC) and the sequential rate of torque development (absolute and relative) were measured before and after exercise. Both protocols elicited a similar decrement in MVC (~ 25%) and in the peak rate of torque development after exercise (~ 45%). The absolute rate of torque development (0-50 and 50-100 ms) was also reduced (p<0.05) similarly between conditions. After normalizing torque values to MVC, this was only sustained for the rate of torque development 0-50ms (p<0.05). We found that both exercise protocols induced similar acute attenuation of the absolute rate of torque development up to the first 100 ms of MVC. We also demonstrated that the reduction in the rate of torque development between 50-100ms (in both protocols) was largely explained by an acute deficit in muscle strength post-exercise. Conversely, the impact of each protocol on the first 50ms of muscle torque did not depend on lower levels of muscle strength after exercise.

Sexual dimorphism in heart rate recovery from peak exercise.

PURPOSE: There is lack of consensus on whether sex, per se, affects heart rate recovery (HRR). To discriminate between the role of sex and that of cardiovascular fitness on HRR, we compared two groups of male and female participants matched for age and peak oxygen uptake (VO2peak) percentile. METHODS: Forty healthy individuals with above-average cardiovascular fitness (VO2peak >50th percentile), aged 18-27 years (23 men; 17 women), performed maximal cycle-ergometer tests with cardiorespiratory measurements. HRR was obtained at 1 and 2 min of passive recovery. Multiple linear regression analysis was used to determine whether the relationship between VO2peak and HRR differed between sexes. RESULTS: Men attained greater peak values for VO2 and work rate (p < 0.05). Both groups of participants exhibited similar heart rate response to peak exercise and no sex differences were observed in VO2peak percentile or ventilatory threshold. HRR at 1 and 2 min of passive recovery was similar between sexes. In multiple linear models, VO2peak explained 11.2% of the variance in HRR1min both in men and women (p < 0.05). Most importantly, sex, VO2peak, and their interaction were all significant predictors of HRR2min (explained variance 29.2%) (p < 0.05). CONCLUSIONS: This study shows that, for a given VO2peak percentile (>50th percentile), there is no sexual dimorphism in HRR obtained at 1 or 2 min of recovery. It also demonstrates that, in persons with similar VO2peak values, HRR obtained at 2 min of peak exercise cessation is affected by sex.

Analysis of power output time series in response to supramaximal exercise: an approach through dynamic factor analysis.

The responses to supramaximal exercise testing have been traditionally analyzed by means of standard parametric and nonparametric statistics. Unfortunately, these statistical approaches do not allow insight into the pattern of variation of a given parameter over time. The purpose of this study was to determine if the application of dynamic factor analysis (DFA) allowed discriminating different patterns of power output (PO), during supramaximal exercise, in two groups of children engaged in competitive sports: swimmers and soccer players. Data derived from Wingate testing were used in this study. Analyses were performed on epochs (30 s) of upper and lower body PO obtained from twenty two healthy boys (11 swimmers and 11 soccer players) age 11-12 years old. DFA revealed two distinct patterns of PO during Wingate. Swimmers tended to attain their peak PO (upper and lower body) earlier than soccer players. As importantly, DFA showed that children with a given pattern of upper body PO tend to perform similarly during lower body exercise.