Changes in antagonist muscles' coactivation in response to strength training in older women.
BACKGROUND
The purpose of this study was to assess changes in neuromuscular function of the plantarflexor and dorsiflexor muscles after 1 year of strength training of these muscles in elderly women. Twelve participants were assigned to a training (74.2 +/- 3.1 years) group and eight to a nontraining group (73.6 +/- 4.3 years).


METHODS
Isometric maximum voluntary contractions (MVC) and muscle activation based on surface electromyography (EMG) were recorded before and after the 12-month training program at six different joint angles.


RESULTS
After training (in the training group), (a) plantarflexion (PF) MVC increased on average by 14.4% (p <.05) across ankle joint angles from -20 degrees dorsiflexion (DF) to +30 degrees PF, (b) DF MVC decreased by 5.7% (p <.05), (c) PF EMG root mean square increased on average by 22.3% (p <.05), and (d) PF antagonists' coactivation increased on average by 7.5% across the tested joint angles. No changes were observed in the nontraining group.


CONCLUSIONS
The present results show a significant increase in antagonist muscle coactivation with strength training in older women. The hypothesis is put forward that with a training-induced gain in agonist muscles' torque, stabilization of the ankle joint by increasing antagonist coactivation is needed because of a changed ratio of maximal PF torque to maximal DF torque.
de Boer
Maarten D
MD
Institute for Biophysical and Clinical Research into Human Movement, Manchester Metropolitan University, Alsager, ST7 2HL, United Kingdom.
Morse
Christopher I
CI
Thom
Jeanette M
JM
de Haan
Arnold
A
Narici
Marco V
MV
D000368:Aged; D000375:Aging / Q000502:physiology*; D000843:Ankle Joint / Q000502:physiology; D016022:Case-Control Studies; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D053580:Muscle Strength / Q000502:physiology*; D019415:Torque