The hormones cortisol (C) and testosterone (T) are inversely impacted by prolonged endurance exercise. C is elevated and T suppressed creating a hormonal imbalance which may adversely affect recovery. Most existing research studies track the acute recovery of C and T for only a few minutes up to 24 h into recovery, but not extended durations.
PURPOSE: Therefore, this study was conducted to determine the length of time required for C and free T to return to resting basal levels following an exhaustive exercise session (EES).
METHODS: 12 endurance-trained males (X±SD: VO2max : 66.3±4.8 ml/kg/min, age: 22.8±3.1 y, body fat: 11.0±1.4 %, training: 7.1 ±3.2 y) completed a treadmill EES at ventilatory threshold (74.7±4.6% of VO2max ; 96.9±10.8 min). Basal blood C and free T were collected at baseline -48 h (48B), -24 h (24B), and immediately before (0B) the EES as well as immediately (0Post), +24 h (24Post), +48 h (48Post), and +72 h (72Post) after the EES. Blood glucose (GLU) was measured to confirm no undue influence on C, and diet and physical activity were controlled. Statistically data were analyzed with repeated measures ANOVA (LSD post-hoc).
RESULTS: C increased significantly from all baseline measures to 0Post (48B, 24B, 0B; p<0.001). At 24Post C was lower than any baseline value (p<0.03), by 48Post C returned to baseline values. GLU had no significant or trending changes at any time point (p =0.645). Free T was significantly reduced at 0Post and 24Post from all baseline measures (p<0.01). Free T did not return to baseline levels until 72Post (p>0.51).
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CONCLUSIONS: Findings show EES results in substantial disturbances in blood C and free T levels, requiring between 48 h and 72 h for recovery and return to normal basal levels. It is recommended that endurance athletes allow adequate time for rest following an EES to ensure complete hormonal equilibrium is established.
