Influence of Quadriceps Femoris Muscle and Tendon Morphology on Mechanical Efficiency During Stretch–Shortening Cycles

Currently, limited information is available on the influence of quadriceps femoris muscle–tendon unit morphological parameters on mechanical efficiency; therefore, the aim of this study was to investigate the interaction between these variables. The morphological characteristics of the quadriceps femoris muscle–tendon unit of nine healthy females (22 ± 0.9 years) were assessed using magnetic resonance imaging. The mechanical efficiency was assessed using a dynamometer. During contractions, the electromyographic activity of the vastus lateralis and rectus femoris was recorded. The highest mechanical efficiency was achieved with moderate pretension and a 20 J stretch load, resulting in an efficiency of 54.14 ± 2.24%. A large correlation was found between the patella tendon cross-sectional area and mechanical efficiency (r = 0.93; p < 0.01). No correlation was observed between the muscle-to-tendon cross-sectional ratio and mechanical efficiency. The association between the patella tendon cross-sectional area and mechanical efficiency aligns with previous research, suggesting that a larger cross-sectional area can reduce tendon stress under a given force, potentially lowering the risk of strain injuries. The lack of association between the muscle-to-tendon cross-sectional ratio and mechanical efficiency indicates that the relative cross-sectional dimensions of muscle and tendon do not influence muscle–tendon dynamics.