Resistance training can induce adaptations within the nervous system that result in altered patterns of muscular coordination. We sought to determine whether a period of resistance training altered the manner in which a complex co-ordination task was performed. Eleven participants were assigned to a training (n = 6) or a control (n = 5) condition. Over a four week period, the training group performed 12 resistance training sessions for the index finger extensor muscles at 70-85% of their original one repetition maximal load and the control group did not train. All participants completed a co-ordination task, before and after the experimental period, that involved 40 trials of rhythmic flexion and extension movements of the index finger. Ten trials were performed in each of four modes of co-ordination that required subjects to synchronise or syncopate their movements with an auditory metronome: extend-on-the-beat, flex-on-the-beat, extend-between-the-beats, flex-between-the-beats. The metronome frequency was increased either from 0.75 or 1.25 Hz in eight steps of 0.25 Hz throughout each trial. Electromyographic activity was recorded from the Extensor Digitorum Communis, Flexor Digitorum Superficialis and First Dorsal Interosseous muscles. Following the coordination task, the maximal voluntary isometric strength of the index finger extensors and flexors was assessed. The peak torque during isometric index finger extension increased for the training group (pre = 0.56 + 0.20 Nm; post = 0.77 + 0.23 Nm; p<0.01) but not the control group (pre = 0.79 + 0.25 Nm; post = 0.74 + 0.24 Nm; p>0.2). In many trials during the co-ordination task, transitions occurred from the prescribed pattern, to either flex-on-the-beat, or extend-on-the-beat, or to phase wandering. For the training group, the median time of successful execution, prior to transition, of the extend-off-the-beat pattern was greater following the period of resistance training (pre = 26.95 seconds; post = 34.5 seconds; p<0.05). Changes in the times to transition were not evident for the other co-ordination patterns, nor for the control group. These data indicate that resistance training has the potential to influence the execution of movements that bear little resemblance to the training task, and has important implications for the design and application of resistance training programs.
Supported by the Australian Research Council.