Leptin And Prolactin Responses During And After Exercise At Constant Or Alternating Intensity

Abstract

Differential hormonal responses have been reported during exercise and recovery depending on the intensity and/or duration of exercise. PURPOSE: The aim of the present study was to examine leptin and prolactin responses during and after exercise protocols of the same mean intensity and duration but performed at constant (CON) or alternating (ALT) intensity in healthy participants. METHODS: Ten healthy males (age: 24.7 ± 4.7 yrs, body mass: 78.5 ± 8.9 kg, height: 180.8 ± 6 cm, body fat: 9.1 ± 3.1%, VO2max: 47.9 ± 6.5 ml/kg/min, lactate threshold (LT): 67.4 ± 3.6% of VO2max, hear rate (HR)max: 188 ± 12 b/min) underwent in a random order two cycling exercise protocols, each lasting 1 hour. On one occasion, exercise intensity was alternated between 47% of VO2max for 40 seconds and 120% of VO2max for 20 seconds, so as the mean intensity was the same, i.e., at 105% of LT. On the other occasion, exercise was constant at 105% of LT. Two-way ANOVA with repeated measures was used for statistics and data are presented as mean ± SD. RESULTS: No significant differences were observed in leptin and prolactin concentrations between the two protocols at any time point measured (p = 0.77 and p = 0.80, respectively). However, in CON leptin decreased (p < 0.05) between Rest and 30 min and 60 min Exercise, as well as 60 min Post Exercise, in contrast with ALT, where leptin values did not significantly alter over time (Rest: 1.70 ± 1.22 ng/ml vs 1.36 ± 1.14 ng/ml, 30 min Exercise: 0.84 ± 0.51 ng/ml vs 1.38 ± 1.10, 60 min Exercise: 0.70 ± 0.47 ng/ml vs 0.86 ± 0.50 ng/ml, 60 min Post Exercise: 1.03 ± 0.71 vs 1.21 ± 1.01 ng/ml in CON and ALT, respectively). In ALT, prolactin levels decreased (p = 0.01) at 60 min Exercise (1.30 ± 0.64 ng/ml), compared to Rest (2.20 ± 0.88 ng/ml), while in CON there were not significantly changes over time (Rest:1.94 ± 0.95 ng/ml, 30 min Exercise: 1.57 ± 0.51 ng/ml, 60 min Exercise: 1.52 ± 0.73 ng/ml, 60 min Post Exercise: 1.61 ± 0.74 ng/ml). CONCLUSIONS: CON and ALT exercise performed at mean intensity of 70% of VO2max appeared to induce similar leptin and prolactin responses during and 1 hour after the end of exercise. These findings suggest that specific hormonal responses to cycling exercise protocols of the same mean intensity and duration are not affected by the form (constant or alternating intensity) of exercise.