Addressing muscle–tendon imbalances in adult male athletes with personalized exercise prescription based on tendon strain

Imbalances of muscle strength and tendon stiffness can increase the operating strain of tendons and risk of injury. Here, we used a new approach to identify muscle–tendon imbalances and personalize exercise prescription based on tendon strain during maximum voluntary contractions (ε_max) to mitigate musculotendinous imbalances in male adult volleyball athletes.

Four times over a season, we measured knee extensor strength and patellar tendon mechanical properties using dynamometry and ultrasonography. Tendon micromorphology was evaluated through an ultrasound peak spatial frequency (PSF) analysis. While a control group (n = 12) continued their regular training, an intervention group (n = 10) performed exercises (3 × /week) with personalized loads to elicit tendon strains that promote tendon adaptation (i.e., 4.5–6.5%).

Based on a linear mixed model, ε_max increased significantly in the control group over the 9 months of observation (p_Con = 0.010), while there was no systematic change in the intervention group (p_Int = 0.575). The model residuals of ε_max, as a measure of imbalances in muscle–tendon adaptation, demonstrated a significant reduction over time exclusively in the intervention group (p_Int = 0.007). While knee extensor muscle strength increased in both groups by ~ 8% (p_Con < 0.001, p_Int = 0.064), only the intervention group showed a trend toward increased normalized tendon stiffness (p_Con = 0.824, p_Int = 0.051). PSF values did not change significantly in either group (p > 0.05).

These results suggest that personalized exercise prescription can reduce muscle–tendon imbalances in athletes and could provide new opportunities for tendon injury prevention.