Effects of Intensive Training on Prolactin Responses to Submaximal Exercise in Males

The purpose of this study was to determine if serum prolactin responses to submaximal exercise were affected by 8 weeks of intensive training (5 d/wk, 90 min/d 65-200% VO₂max). Nine males performed 90 minute continuous exercise bouts (cycle ergometry; 65% VO₂ max) at the end of 1, 4, and 8 weeks of training. Blood samples were obtained pre-training, and pre-, post-exercise. Significant differences were not seen in pre- and post-exercise prolactin levels at weeks 1 and 4. However, at week 8 the post-exercise prolatin was significantly greater than the pre-exercise levels (6.8 ± 0.9 vs 3-8 ± 1.0 ng·ml P<0.05). When post-exercise serum prolactin levels were expressed as a percentage of pre-exercise concentrations, changes of - 30.6%, + 101.1%, and + 233.3% were observed at weeks 1, 4, and 8, respectively. Resting prolaction levels (pre-exercise) were found to decrease significantly from pre-training and week 1 to week 8 (12.3 ± 1.2 and 11.1 ± 1.1 vs 3.8 ±0.9 ng•ml^-1, respectively). The findings suggest intensive training results in a relative augmentation of the post-exercise prolactin response; however, this effect seems to be due primarily to the training induced lowered resting prolactin levels.