Differences in muscle mechanical properties between elite power and endurance athletes: a comparative study

The aim of this study was to compare muscle mechanical properties (using tensiomyography – TMG) and jumping performance of endurance and power athletes, and to quantify the associations between TMG parameters and jumping performance indices. Forty-one high-level track and field athletes from power (n=22; mean ± SD age, height, and weight were 27.2 ± 3.6 years; 180.2 ± 5.4 cm; 79.4 ± 8.6 kg) and endurance (endurance runners and triathletes; n=19; mean ± SD age, height, and weight were 27.1 ± 6.9 years; 169.6 ± 9.8 cm; 62.2 ± 13.1 kg) specialties had the mechanical properties of their rectus femoris (RF) and biceps femoris (BF) assessed by TMG. Muscle displacement (Dm), contraction time (Tc), and delay time (Td) were retained for analyses. Furthermore, they performed squat jumps (SJ), countermovement jumps (CMJ) and drop jumps to assess reactive strength index (RSI), using a contact platform. Comparisons between groups were performed using differences based on magnitudes and associations were quantified by the Spearman's ρ correlation. Power athletes showed almost certain higher performance in all jumping performance indices when compared with endurance athletes (SJ = 44.9 ± 4.1 vs. 30.7 ± 6.8 cm; CMJ = 48.9 ± 4.5 vs. 33.6 ± 7.2 cm; RSI = 2.19 ± 0.58 vs. 0.84 ± 0.39, for power and endurance athletes, mean ± SD, respectively; 00/00/100, almost certain, P< 0.05), along with better contractile indices reflected by lower Dm, Tc and Td (Tc BF = 14.3 ± 2.3 vs. 19.4 ± 3.3 ms; Dm BF = 1.67 ± 1.05 vs. 4.23 ± 1.75 mm; Td BF = 16.8 ± 1.6 vs. 19.6 ± 1.3 ms; Tc RF = 18.3 ± 2.8 vs. 22.9 ± 4.0 ms; Dm RF = 4.98 ± 3.71 vs. 8.88 ± 3.45 mm; Td RF = 17.5 ± 1.0 vs. 20.9 ± 1.6 ms, for power and endurance athletes, mean ± SD, respectively; 00/00/100, almost certain, P< 0.05). Moderate correlations (Spearman's ρ between -0.61 and -0.72) were found between TMG and jumping performance. The power group presented better performance in vertical jumps, supporting the validity of these tests to distinguish between endurance and power athletes. Furthermore, TMG can discriminate the "athlete-type" using non-invasive indices moderately correlated with explosive lower-body performance. In summary, both vertical jump and TMG assessments could be useful in identifying and selecting young athletes.