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Muscle tone in young soccer players is key for optimizing performance and reducing injury risk. This study evaluated an 8-week predominantly eccentric training protocol’s impact on triceps surae/Achilles tendon mechanical properties and ankle dorsiflexion.

Thirty players were randomized to an intervention group (IG, n = 15; additional 2 weekly eccentric sessions) or control group (CG, n = 15; regular training). Mechanical properties were assessed via myotonometry and ankle dorsiflexion via the Weight-Bearing Lunge Test.

Results at 8 weeks showed in IG vs. CG: 1) Reduced active tension (muscle frequency: lateral gastrocnemius left d = −0.82, right d = −1.40; medial gastrocnemius left d = −1.29, right d = −1.30; soleus right d = −0.80; Achilles tendon left d = −0.68; all p < 0.05). 2) Decreased stiffness in lateral gastrocnemius right (d = −1.12) and medial gastrocnemius (left d = −0.68, right d = −0.86; p < 0.05). 3) Increased passive tension properties: creep in lateral gastrocnemius right (d = 0.94; p < 0.05) and medial gastrocnemius (left d = 0.79, right d = 0.97; p < 0.05); relaxation in medial gastrocnemius (left d = 0.64, right d = 1.03; p < 0.05). 4) Reduced ankle dorsiflexion in the right leg (d = −0.68; p < 0.05).

These findings indicate that eccentric training modulates musculotendinous mechanical properties, potentially influencing neuromechanical factors related to injury-related mechanisms.

Keywords: injury, muscle tension, musculotendinous, myotonometry, stiffness

The findings of this study suggest that an 8-week eccentric training intervention generated significant changes in the musculotendinous biomechanics, the active tension and passive tension variables of the gastrocnemius musculature and the Achilles tendon of young footballers. Decreasing the frequency may reflect a modulation of musculotendinous tension, which could be relevant for mechanical load management strategies, although no direct conclusions regarding injury reduction can be drawn from the present findings. In turn, the increase in the corresponding passive tension variables (stiffness, creep, stress relaxation) and the decrease of the decrement provided an optimal adaptation of force transmission and elastic energy storage. All these elements combine to improve the stability of the lower limb under conditions involving fatigue. In functional terms, the reduced dorsiflexion of the right leg does not entail an adverse effect, but rather an adjustment of the muscular tension and less tendon and ligament overload. Together, these adaptations reflect the existence of a balance between the active and passive tension that may contribute to a more balanced musculotendinous profile that is theoretically linked to injury-related mechanisms.