Muscle activation pattern and onset times during a semi-orthostatic, unilateral closed-kinetic hip extension exercise in adolescent males.

The hip extensors are an important muscle group for sporting and functional movements, but assessing this muscle group for musculoskeletal dysfunction and strength testing has been performed in adult males and females as a prone, open-chain exercise, which provides little posture specificity for locomotive activities. Given the importance of closed-kinetic chain exercises for strength and rehabilitation requirements, there is an obvious need to assess hip extension but little is known about executing a closed-kinetic chain hip extension exercise for adolescents. Therefore, the aim of this study was to ascertain hip extensor muscle activation pattern and force production using a semi-orthostatic position while performing a unilateral closed-kinetic hip extension exercise. Fourteen young healthy adolescent male participants performed three maximal repetitions of closed-kinetic chain left and right hip extension on a glute machine. Electromyography (EMG) from left and right rectus femoris (RF), gluteus maximus (GM), and biceps femoris (BF) was recorded and RF, GM, and BF EMG mean amplitude, EMG area and onset times were analysed. There was no significant difference in EMG mean amplitude and EMG area between RF, GM, and BF but the right hip showed a significantly higher EMG (p < 0.05) than the left hip. The relative onset difference between GM and BF was similar in both hips, suggesting that there was no dominant muscle firing order. The closed-kinetic chain hip extension could be advantageous when assessing neuromuscular function and training muscle strength because the semi-orthostatic position of hip extension exercise provides a posture similar to functional activities.