The effect of Interaction circadian and menstrual rhythm on lactate recovery after a maximal exercise

The purpose of this study was to determine the effect of Interaction circadian and menstrual rhythm on lactate recovery after a maximal exercise. Twelve physical education female students (Mean ± SD، aged 20. 75±1. 60 yrs، height 164. 75±3. 62 cm، weight 55. 08±5. 45 kg،) participated in this study. All subjects performed Bruce test to exhaustion and then walked for 20 min، with 1. 7 speeds (mph) and 0% grade of slope (%) at recovery period. Blood lactate concentrations were assessed immediately after the test and at 5th، 10th and 20th min of recovery period at two times of day (06:00 h and 18:00 h) and two phases of the menstrual cycle (mid luteal and mid follicular phases). Two-way repeated-measures analysis of variance ANOVA was used for analyzing data. No significant menstrual cycle (F=1. 10، P=0. 36)، and interaction effect (menstrual cycle & time of day) was observed for lactate recovery (F=0. 67، P=0. 55). also there was no significant variation for blood lactate concentrations at 5th and 10th min of recovery between 06:00 h and 18:00 h. But a significant decrease was found for blood lactate concentrations at 20th min of recovery between 06:00 h and 18:00 h (F=2. 99، P=0. 04). It can be concluded that lactate recovery in the afternoon occurred faster compared to the morning. But follicular and luteal phases of the menstrual cycle had no any effects on the lactate recovery.