Muscular lower leg asymmetry in middle-aged people

BACKGROUND: The purpose of this study was to determine whether muscular asymmetries were present in the lower legs of recreationally active middle-aged people grouped by leg dominance. METHODS: Twelve healthy middle-aged subjects were analyzed bilaterally. The clinical variables included leg dominance, sports level, range of motion, lower leg alignment, calf circumference, and AOFAS (American Orthopaedic Foot and Ankle Society) ankle score. The biomechanical variables included maximal voluntary isometric ankle joint torque and surface electromyography (EMG) with determination of mean EMG frequency and intensity of four lower leg muscles: anterior tibial (AT), medial gastrocnemius (MG), soleus (SO), and peroneus longus (PL). RESULTS: The mean EMG frequency was significantly lower in the dominant leg for the AT (dominant, 148.6 Hz; nondominant, 157.8 Hz) and MG muscles (dominant, 183.9 Hz; nondominant, 196.8 Hz). A significantly higher plantarflexion torque was found in the dominant leg (27.1 Nm) compared to the nondominant leg (22.9 Nm). Higher (not significant) dorsiflexion torque was found in the dominant leg (dominant, 27.3 Nm; nondominant, 24.8 Nm). The calf circumference was marginally significantly higher (p =0.039) in the dominant leg (34.2 cm; nondominant leg, 33.8 cm). The dominant leg had a higher but not significantly different mean EMG intensity for all four muscles. CONCLUSIONS AND CLINICAL RELEVANCE: Differences in muscle EMG and torque were found between the dominant and nondominant lower leg. These results might be applicable to treatment, rehabilitation, and future research of lower leg and foot and ankle disorders.