McGuire, J., Green, L., Calder, K. M., Patterson, J., & Gabriel, D. A. (2013). The effect of massed versus distributed practice on the variability of muscle activity and force. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 1543.

This study determined if the initial phase of learning a resistive exercise task is affected by the structure of the practice schedule. Females (N = 26) were randomly assigned to one of two experimental groups: massed, which performed 15 isometric elbow-flexion contractions on one day, or distributed, which performed the 15 contractions across three days (5 per day). All Ss performed two retention tests, each consisting of five contractions, which occurred two weeks and three months after the final test session. Each contraction was 5-seconds with a 3-minute inter-trial rest. Surface electromyographic activity and force were recorded concurrently. Mean amplitude values and variance ratios were calculated for the biceps and triceps surface EMG data and force.

There was a significant increase in force and biceps brachii surface EMG in both groups. That increase was maintained across both retention tests. The force-magnitude data revealed no significant difference between the two practice schedules. In contrast, the pattern of change in force variability was different between the two schedules. Force variability for the massed group decreased but plateaued after the first block of trials, whereas the distributed group exhibited a more gradual reduction of similar magnitude. Both groups maintained a nearly 60% decrease in force variability across the two retention tests. The variability in the biceps and triceps surface EMGs mirrored the variability in force but were not significant.

Implication. The magnitude of force and surface EMGs revealed no difference between massed and distributed practice schedules, but the force variability data followed the classic findings for massed versus distributed practice. The initial phase of learning a resistive exercise task was affected by the type of practice schedule.

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