Chronic Resistance Training Does Not Ameliorate Unloading-Induced Decrements in Neuromuscular Function.

Abstract

The aim of this study was to assess the efficacy of long-term resistance training in preventing the detrimental effects of muscle unloading on neuromuscular function. Eleven untrained men and 11 men with extensive backgrounds in resistance training were tested for several parameters of neuromuscular function at various isokinetic contractile velocities before and after 7 days of muscle unloading. Measurements included muscle mass, strength, power, total work, electromyography, and neuromuscular transmission efficiency using superimposed electrical stimulation of maximally contracting muscles. Muscle performance was superior in resistance-trained subjects before and after unloading. In both groups of participants, unloading resulted in significantly (P < 0.05) diminished muscle performance, but only at isometric or slower isokinetic contractile velocities. Electromyography activity was significantly higher in trained than in untrained subjects before and after unloading. Thigh muscle mass was greater among trained subjects before and after unloading. Neither electromyography activity, thigh muscle mass, nor neuromuscular transmission efficiency was significantly altered by unloading in trained or untrained participants. Chronic resistance training was found to be ineffective in neutralizing the deleterious effects of unloading on neuromuscular function. It appears that positive adaptations associated with long-term resistance training provide no prophylactic effect when neuromuscular systems are subjected to unloading.