Abstract
Strength training performed with heavy loads and maximal intended velocity is documented to enhance efferent neural drive in older individuals. However, it remains unclear whether the neural plasticity following training result from motor skill learning or if external resistance is a prerequisite. PURPOSE: To investigate the importance of external resistance on neural plasticity in older individuals. METHODS: Electrically evoked potentials (H-reflex and V-waves normalized to maximal M-wave) and voluntary activation (VA) were assessed in 36 older individuals (73±4 years). Participants were randomized to 3 weeks of plantar flexion strength training, with (maximal strength training; MST) or without (unloaded ballistic training; UBT) heavy external loading (90% of one repetition maximum), or a control group. Both training groups aimed to execute the concentric phase of movement as fast and forcefully as possible. RESULTS: The MST group improved maximal voluntary contraction (MVC) and rate of force development (RFD) by 18±13% (p<0.01) and 35±17% (p<0.01), respectively, and this was different (p<0.01) from the UBT group which exhibited a 7±8% (p<0.05) increase in MVC (p<0.05) and a tendency of an increase in RFD (p=0.12). Concomitant improvements in efferent neural drive, evident as a 79±80% increase in V/M-ratio (p<0.01) and a tendency towards increased VA (p=0.11), were only apparent after MST. No changes were observed in H/M-ratio for any of the groups. CONCLUSION: External loading following exercise training appears to be a prerequisite for efferent neural drive enhancement in older individuals, and advocates that heavy resistance training should be recommended to counteract the typically observed age-related decline in motoneuron firing frequency and recruitment.
Published Version
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