Neuromuscular adaptations associated with the onset of rapid strength gains in the elderly
Date
2005
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Publisher
University of Delaware
Abstract
Rapid neuromuscular adaptations were evaluated in response to a two-day strength training protocol designed to elicit quick jumps in strength and improved muscular performance in older adults. The protocol produced rapid improvements in strength without the soreness typically observed at the onset of strength training. Twenty older adults (7 men and 13 women, 76 +- 6 years) participated in two strength-training sessions of low-resistance, high-velocity plantar flexion exercises separated by 48-hours. On three test days separated by 48 hours, maximal voluntary torque, muscle contractility, motor neuron excitability, and electromyographic activity of the triceps surae were measured. Exercise training followed testing on days 1 and 2. The voluntary tests provided measures of maximal plantar flexion torque (MVT), maximal rate of torque development (RTD), and reaction time. Resting muscle twitches were recorded before and after a 10-second maximal voluntary contraction (MVC) and provided measures of contractility for resting and potentiated muscle. The H-reflex was recorded from the soleus to provide a measure of motor neuron excitability. There were significant increases in MVT (F 2,38 = 5.606, p = 0.007) and the extent of post-activation potentiation (F 2,38 = 3.901, p = 0.029). RTD showed a trend parallel to MVT toward improved performance, increasing 23.7%, but the improvement was not significant (F 2,38 = 1.244, p = 0.300). No changes were observed in reaction time or motor neuron excitability (H-reflex). The brief duration of this training protocol was sufficient to improve strength prior to hypertrophy and post activation potentiation exhibited rapid enhancement in older adults.