Not All Hip Abductions Are Equal: The 45° Paradox Between Gluteus Medius and Tensor Fasciae Latae

Understanding how joint position influences muscle recruitment is essential for improving exercise prescription. This study examined how different hip flexion angles affect the electromyographic (EMG) activity of the gluteus medius (GMed) and tensor fasciae latae (TFL) during seated hip abduction — a popular movement in resistance training and rehabilitation. Fourteen recreationally trained volunteers performed the exercise at 45°, 90°, and 135° of hip flexion, with the load set at 60% of their individual six-repetition maximum (6RM). Surface EMG signals of GMed and TFL were recorded and normalized to maximal voluntary isometric contraction (%MVIC). Data were analyzed using Friedman’s test and Dunn’s post hoc comparisons (p < 0.05), with effect sizes (Hedges’ g) and 95% confidence intervals calculated via the Estimation Stats platform. Results showed a clear pattern: increased hip flexion significantly decreased TFL activation while maintaining moderate GMed activity. Peak and average GMed activation were notably higher at 45° compared to 135° (p < 0.001), whereas TFL activation decreased progressively across 45°, 90°, and 135° (all p < 0.01). Most importantly, the GMed:TFL activation ratio tripled at 135°, indicating a significant shift toward targeted GMed recruitment and reduced TFL dominance. Therefore, increasing hip flexion during seated abduction enhances the neuromuscular selectivity of the gluteus medius while reducing tensor fasciae latae overactivation — a finding with direct implications for both hypertrophy-focused training and clinical rehab. These findings redefine how a simple change in hip angle can transform one of the most common lower-body exercises.