Sustained sleep restriction reduces resistance exercise quality and quantity in females

Introduction
Female athletes sleep less and report more sleep problems than their male counterparts. Inadequate sleep reduces maximal strength in male athletes; however, little is known about the impact of sleep restriction (SR) on the quantity and quality of resistance exercise performed by female athletes. This study investigated the effect of nine nights of moderate SR on repeated resistance exercise performance, hormonal responses, and perceived fatigue in females.

Methods
Ten healthy, resistance-trained, eumenorrheic females age 18–35 yr underwent nine nights of SR (5-h time in bed) and normal sleep (NS; ≥7-h time in bed) in a randomized, crossover fashion with a minimum 6-wk washout. Participants completed four resistance exercise sessions per trial, with blood samples collected before and after exercise. Exercise performance was assessed using volume load, reactive strength index, and mean concentric velocity with rating of perceived exertion recorded after exercise. Participants completed awakening saliva sampling and the Multi-component Training Distress Scale daily.

Results
Volume load decreased trivially (<1%, P < 0.05) with SR. Mean concentric velocity per set was slower during SR for the lower-body (up to 15%, P < 0.05), but not the upper-body, compound lifts. Intraset velocity loss was up to 7% greater during SR for back squats (P < 0.05). SR increased salivary cortisol area under the curve (by 42%), total training distress (by 84%), and session perceived exertion (by 11%).

Conclusions
Sustained SR reduces markers of resistance exercise quality (bar velocity) more than quantity (volume load) and increases perceived effort at the same relative intensity in resistance-trained females. Markers of exercise quality and internal load may be more sensitive than volume load, to advise coaches to the decline in lifting performance for female athletes experiencing SR.