Affiliations: [a] Department of Kinesiology, University of New
Hampshire, Durham, NH, USA
Note: [] Address for correspondence: Dain P. LaRoche, Ph.D., 124 Main
Street, Durham, NH 03824, USA. Tel.: +1 603 862 4859; Fax: +1 603 862 0154;
E-mail: [email protected]
Abstract: The purpose of the study was to identify both demographic and
neuromuscular traits that characterize successful or unsuccessful adaptation to
resistance training in older ± women. Twelve, older women underwent electrically
evoked muscle twitches for the knee extensors; and performed maximal,
voluntary, isometric knee extensions, followed by eight weeks of resistance
training. Prior to training nonresponders had 67% higher twitch peak torque
than responders (0.29 ± 0.05 vs. 0.18 ±0.06 Nm·kg^{-1}
respectively), 64% higher twitch rate of torque development (RTD) (3.96 ±
0.47 vs. 2.42 ± 0.62 Nm·s^{-1}·kg^{-1}), 51% higher
voluntary peak torque (1.86 ± 0.40 vs. 1.23 ± 0.33
Nm·kg^{-1}), 101% greater RTD (9.43 ±1.52 vs. 4.70 ±
2.40 Nm·s^{-1}·kg^{-1}), 86% greater impulse (0.13 ±
0.01 vs. 0.07 ± 0.03 Nm·s·kg^{-1}) and 27% faster motor
time (80 ± 13 vs. 109 ± 34 ms), (all P < 0.05). Following
training, responders showed an 11% increase in twitch peak torque over
baseline (0.18 ± 0.06 to 0.20 ± 0.05 Nm·kg^{-1}), 15%
increase in voluntary peak torque (1.23 ± 0.33 to 1.41 ± 0.36
Nm·kg^{-1}), 47% increase in RTD (4.70 ± 2.40 to 6.93 ±
2.02 Nm·s^{-1}·kg^{-1}), 43% increase in impulse (0.07
± 0.03 to 0.10 ± 0.04 Nm·s·kg^{-1}), and 26% increase in
rate of EMG rise (886 ± 214 to 1116 ± 102% pEMG·s^{-1})
(all P < 0.05). Initially higher muscle mass and contractility, coupled
with greater neural drive, likely explains why older women with good muscle
performance seem to have a lower capacity for improvement than women with low
initial levels of performance.
Keywords: Electromyography, aging, training adaptations, strength, power, nervous activation, reaction time
