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.
