Taylor, S. R., Rogers, G. G., & Driver, H. S. (1997). Effects of training volume on sleep, psychological, and selected physiological profiles of elite female swimmers. Medicine and Science in Sports and Exercise, 29, 688-693.

Excessive training is reported to cause sleep disturbances and mood changes. Sleep and psychological changes in female swimmers across a competitive swimming season, that is, at the start of the season (onset), during peak training period (peak), and after a precompetition reduction in training (taper), were examined.

For each study phase, polysomnographic recordings, body composition, psychological parameters, and swimming performance measures were obtained. A daily training log and sleep diary were maintained for the entire study period.

Sleep onset latency (SOL), time awake after sleep onset, total sleep time (TST), and rapid eye movement (REM) sleep times were similar at all three training levels. Slow wave sleep (SWS) formed a very high percentage of total sleep in the onset (26%) and peak (31%) training periods, but was significantly reduced following precompetition taper (16%), supporting the theory that the need for restorative SWS is reduced with reduced physical demand. The number of movements during sleep was significantly higher at the higher training volumes, suggesting some sleep disruption. In contrast to other studies, mood deteriorated with a reduction in training volume and/or impending competition.

Implication. Sleep and sleep variables are associated with training workloads and reductions in those loads. This may well be a major factor associated with adequate recovery from excessive training loads (overreaching) and restorative recovery when preparing for a major competition.

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