Age related neural adaptation following short term resistance training in women.

Background. This study examined the influence of age on neural facilitation and neural cross-education following short term unilateral dynamic resistance training with the hypothesis that older women may have a diminished ability for adaptation. Methods. Experimental design: this was a prospective, repeated measures design. The non-dominant left arm served as a control limb and follow-up testing was performed two weeks after pretesting. Setting: testing was conducted in the Neuromuscular Research Laboratory at the University of Oklahoma. Patients: 20 females (n=10, young (YF) 20.8±0.1 yrs; n=10, older (OF) 58.1±0.14) were assessed. Interventions: 14 days of training of the right elbow flexors only. On each day, subjects performed four sets of ten repetitions using 70% of maximal strength of the biceps brachii. Measures: the following variables in both right and left elbow flexor muscle groups were evaluated; isometric strength (IMS), efficiency of electrical activity (EEA) and estimated upper arm cross-sectional area (CSA). Results. There were significant increases (p<0.01) in IMS of both the right (28%) and left (12-15%) muscle groups for both age groups. Strength improvements were explained by neural adaptation since there were no changes in upper arm CSA but consistent decreases in EEA (12-16%). While OF had consistently lower values for all variables, there were no significant age effects. Conclusions. Short term unilateral dynamic resistance training is a sufficient stimulus to induce significant strength increases in both trained and untrained contralateral limbs and that a neural mechanism is responsible for the muscular adaptation in both young and older women. Implication exists for unilateral stroke victims, individuals with single hip or knee replacements, or single limb casts.