Increased rate of force development and neural drive of human skeletal muscle following resistance training

• Published in: Journal of applied physiology (1985) Vol. 93; no. 4; pp. 1318 - 1326
• Main Authors: Aagaard, Per, Simonsen, Erik B, Andersen, Jesper L, Magnusson, Peter, Dyhre-Poulsen, Poul
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.10.2002; American Physiological Society
• Subjects: Adult; Biological and medical sciences; Efferent Pathways - physiology; Electromyography; Exercise; Fundamental and applied biological sciences. Psychology; Humans; Leg; Male; Muscle Contraction; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Muscular system; Nervous System Physiological Phenomena; Physical Education and Training; Physical training; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system; Weight Lifting; Human; Physical training; Force; Electrophysiology; Development; Quadriceps muscle; Electromyography; Striated muscle; Muscle contraction; Motor control
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00283.2002

1  Department of Neurophysiology, Institute of Medical Physiology, 3  Anatomy Department C, Panum Institute, 4  Copenhagen Muscle Research Centre, Rigshospitalet, and 2  Team Danmark Testcentre, Sports Medicine Research Unit, Bispebjerg Hospital, University of Copenhagen, DK-2200 Copenhagen, Denmark The maximal rate of rise in muscle force [rate of force development (RFD)] has important functional consequences as it determines the force that can be generated in the early phase of muscle contraction (0-200 ms). The present study examined the effect of resistance training on contractile RFD and efferent motor outflow ("neural drive") during maximal muscle contraction. Contractile RFD (slope of force-time curve), impulse (time-integrated force), electromyography (EMG) signal amplitude (mean average voltage), and rate of EMG rise (slope of EMG-time curve) were determined (1-kHz sampling rate) during maximal isometric muscle contraction (quadriceps femoris) in 15 male subjects before and after 14 wk of heavy-resistance strength training (38 sessions). Maximal isometric muscle strength [maximal voluntary contraction (MVC)] increased from 291.1 ± 9.8   to 339.0 ± 10.2 N · m after training. Contractile RFD determined within time intervals of 30, 50, 100, and 200 ms relative to onset of contraction increased from 1,601 ± 117 to 2,020 ± 119 ( P  <   0.05), 1,802 ± 121 to 2,201 ± 106 ( P  < 0.01), 1,543 ± 83 to 1,806   ± 69 ( P  < 0.01), and 1,141 ± 45 to 1,363 ± 44 N · m · s 1 ( P  < 0.01), respectively. Corresponding increases were observed in contractile impulse ( P  < 0.01-0.05). When normalized relative to MVC, contractile RFD increased 15% after training (at zero to one-sixth MVC; P  < 0.05). Furthermore, muscle EMG increased ( P  < 0.01-0.05) 22-143% (mean average voltage) and 41-106% (rate of EMG rise) in the early contraction phase (0-200 ms). In conclusion, increases in explosive muscle strength (contractile RFD and impulse) were observed after heavy-resistance strength training. These findings could be explained by an enhanced neural drive, as evidenced by marked increases in EMG signal amplitude and rate of EMG rise in the early phase of muscle contraction. electromyography; neural adaptation; quadriceps muscle