Inverse activation between the deeper vastus intermedius and superficial muscles in the quadriceps during dynamic knee extensions

• Published in: Muscle & nerve 2013-05, Vol.47 (5), p.682-690
• Main Authors: Akima, Hiroshi, Saito, Akira
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; concentric contraction; eccentric contraction; Electromyography; EMG-angle relationship; Humans; Isometric Contraction - physiology; Knee - physiology; Knee Joint - physiology; Male; quadriceps femoris; Quadriceps Muscle - physiology; surface electromyogram
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/mus.23647

Introduction: We sought to determine the neuromuscular activation patterns of 4 synergistic muscles of the quadriceps femoris (QF), including the vastus intermedius (VI) muscle, during dynamic knee extensions. Methods: Nine healthy men performed dynamic knee extensions in the range of 20–100% of the one‐repetition maximum (1RM) load. Surface electromyography (EMG) was recorded from the 4 muscles of the QF. Results: The normalized EMG amplitude of the VI was significantly higher at knee joint angles between 90° and 115° during both the concentric and eccentric phases, and it was significantly lower between 140° and 165° during concentric and eccentric phases, compared with those of vastus lateralis at 60–100% of 1RM load (P < 0.05). Conclusions: These results suggest that the VI plays a key role during dynamic knee extension with flexed joint angles and specifically contributes to the initial concentric and final eccentric phases of knee joint movements. Muscle Nerve 47: 682–690, 2013