EFFECTS OF REAL AND IMAGINED TRAINING ON VOLUNTARY MUSCLE ACTIVATION DURING MAXIMAL ISOMETRIC CONTRACTIONS

In this study we directly tested the hypothesis that isometric strengt h training increases voluntary drive to muscles. In addition, it was a ttempted to replicate the findings of an earlier study that showed ima gined training increases voluntary strength as much as actual training , as this finding provides key support for the hypothesis that trainin g increases voluntary drive (Yue & Cole 1992). Fifty-four subjects wer e randomly allocated to groups that performed 8 weeks of isometric tra ining of the elbow flexor muscles, imagined isometric training, or a c ontrol task involving the lower limbs. Voluntary isometric strength an d activation of the elbow flexor muscles were measured before and afte r training. Voluntary activation was measured with a sensitive form of twitch interpolation. Training, imagined training and control groups increased voluntary isometric elbow flexor strength by means of 17.8% (+/-3.1 SEM), 6.8% (+/-2.6) and 6.5% (+/-3.0), respectively. The train ing group increased in strength significantly more than imagined train ing and control groups (P = 0.01 for both comparisons), but the small difference between imagined training and control groups was not signif icant (P = 0.31). Prior to training, voluntary activation of all subje cts was high (96.2 +/- 0.5%). This did not change significantly with t raining and there were no significant differences between groups. Thes e data challenge the hypothesis that training of the elbow flexor musc les increases isometric strength by inducing adaptations of the centra l nervous system, because they show that training does not increase vo luntary activation and imagined training does not increase strength.