Evolution of contractile properties of the lower limb muscles throughout a season in elite futsal players.

Background: Futsal is a team sport involving intermittent technical actions of high intensity, and high physical (strength) and muscular demands. In this regard, the tensiomyography (TMG) is a useful and non-invasive tool for the monitoring and assessment of the muscle's contractile capacity. This study aimed to analyze the changes in the contractile properties produced during the season, as well as to determine the potential cumulative effect of a resistance training (RT) program in futsal players.
Methods: Fourteen elite futsal players (2 goalkeepers, 4 defenders, 4 wingers and 3 pivots) were assessed by TMG at 11th, 18th, and 28th week of the season. The maximal radial displacement of the muscle belly (Dm); contraction time (Tc); delay time (Td) and radial displacement velocity (90%) Dm (VrD90) were assessed. After the second measurement, a RT program was included in the regular training sessions and focused on the lower body musculature. It was performed during 9 weeks (1-weekly). Finally, a third measurement was performed between 28th-29th weeks. Repeated measures analysis of variance was used to detect in-season changes. Two factors were included: Time (changes detected after resistance training program) was used as the within-subject factor and the specific position was used as the between-subject factor.
Results: An increment in Tc for several muscles: biceps femoris (BF; P=0.02), semitendinosus (ST; P=0.04), adductor longus (AL; P=0.008) and gastrocnemius medialis (GM; P=0.009) was observed throughout the season. Similarly, significant increments in Dm for GM (P=0.02) and AL (P=0.05), as well as increments in Td for BF (P=0.002) were found. Moreover, no significant changes in VrD90 between time points 2-3 (analysis of RT effect) were observed. Additionally, the player´s positions reported no significant changes for any of the variables analyzed.
Conclusions: An increase respect to baseline levels was observed for Tc, Td and Dm during the season. However, the adaptations to contractile properties were muscle specific. In addition, an in-season 9-week RT program (1-weekly), had no significant effects (time points 2-3) on the contractile properties of futsal players. In addition, there were no differences when comparing different positions.