Post-Activation Potentiation Increases Recruitment of Fast Twitch Fibers: A Potential Practical Application in Runners.

To determine the relationship between fatigue and post-activation potentiation, we examined the effects of sub-maximal continuous running on neuromuscular function tests, as well as on the squat jump and counter movement jump in endurance athletes. The height of the squat jump and counter movement jump and the estimate of the fast twitch fiber recruiting capabilities were assessed in seven male middle distance runners before and after 40 min of continuous running at an intensity corresponding to the individual lactate threshold. The same test was then repeated after three weeks of specific aerobic training. Since the three variables were strongly correlated, only the estimate of the fast twitch fiber was considered for the results. The subjects showed a significant improvement in the fast twitch fiber recruitment percentage after the 40 min run. Our data show that submaximal physical exercise determined a change in fast twitch muscle fiber recruitment patterns observed when subjects performed vertical jumps; however, this recruitment capacity was proportional to the subjects' individual fast twitch muscle fiber profiles measured before the 40 min run. The results of the jump tests did not change significantly after the three-week training period. These results suggest that pre-fatigue methods, through sub-maximal exercises, could be used to take advantage of explosive capacity in middle-distance runners.

Muscular viscoelastic characteristics of athletes participating in the European Master Indoor Athletics Championship.

PURPOSE: To investigate how the viscoelastic characteristics of muscles (non-neural tone, elasticity and stiffness) vary as a function of age and gender in a sample of track and field master athletes. To compare these findings with data on related sedentary subjects in literature. METHODS: A total of 390 athletes (aged 35-99) were assessed during the European Master Athletics Indoor Championship 2016. A non-invasive measurement device called MyotonPro was used to measure tone, stiffness, and elasticity in the biceps brachii and rectus femoris muscles at rest. Linear regression analysis was used to assess the correlation between age and the measured parameters. To compare our results with previously reported data, we stratified participants according to gender and age. RESULTS: Tone was found to not be dependent on age, whereas stiffness was found to be age dependent. Elasticity was found to be both physical activity and age dependent. Tone (only for men), elasticity, and stiffness were lower in master athletes than in sedentary subjects. CONCLUSIONS: Tone, elasticity, and stiffness change with aging; nevertheless, our findings suggest that physical activity can delay the effects of muscular aging, improving fitness in older people.