Gastrocnemius medialis tendon properties do not differ between male academy soccer players and control participants but are related to jump performance

The aims of this study were to investigate (i) differences in gastrocnemius medialis (GM) tendon properties between adult male soccer players from an English category one academy (ASP) and male control participants (CON); and (ii) the relationships between GM tendon properties and jump performance. The GM tendon force-elongation relationship was measured in 13 ASP (mean ± SD height 1.81 ± 0.07 m; mass 73.6 ± 5.4 kg; age 18.8 ± 1.2 years) and 11 CON (1.74 ± 0.05 m; 71.2 ± 7.6 kg; 22.3 ± 3.0 years) using a combination of dynamometry, ultrasonography and electromyography. Participants also performed a series of unilateral and bilateral countermovement jumps (CMJ) and bilateral drop jumps on a force platform. GM tendon properties did not differ between groups but maximal tendon elongation correlated inversely with unilateral vertical CMJ peak power (r = -0.427, P = 0.037). Furthermore, leg stiffness and peak force during a drop jump correlated with GM tendon stiffness (r = 0.431-0.462, P = 0.035-0.023), maximal tendon force and Achilles tendon CSA (r = 0.409-0.737, P ≤ 0.047). These results suggest that GM tendon properties do not differ between ASP and CON but a stiffer GM tendon may facilitate the production of larger forces to increase power output during a unilateral vertical CMJ. Furthermore, higher force and stiffness outputs are achieved during a drop jump by stronger individuals with larger and stiffer GM tendons, which could lead to greater pitch-based performance and may represent a protective mechanism to shield the tendon against injury.