An exploratory study into the effect of exhausting bicycle exercise on endocrine and immune responses in post-menopausal women: Relationships betweenvigour and plasma cortisol concentrations and lymphocyte proliferation following exercise

It is well-established that bicycle exercise alters the endocrine and immun e responses in men, but little information is available for women, especial ly middle-aged, post-menopausal women. The purpose of our study was to docu ment the endocrine and immune reactivity to exhausting bicycle exercise in post-menopausal women, and to explore whether complaints of fatigue or low vigour are related to these exercise-induced responses. Thirteen healthy po st-menopausal women participated in this study. We used a graded exercise p rotocol to study the kinetics of activation of the endocrine and immune sys tem. We chose to examine hormones related to the hypothalamus-pituitary-adr enal (HPA) system such as adrenocorticotropin hormone (ACTH) and cortisol a nd hormones related to the pituitary such as prolactin (PRL) and growth hor mone (GH). With regard to the immune system, we examined the natural killer (NK) cell activity and pokeweed (PWM)-induced lymphocyte proliferation in addition to changes in peripheral blood cell counts. Our results demonstrat e that acute physical stress results in a strong release of ACTH, cortisol, GH and PRL. The bicycle test significantly increased the number of CD3(+), CD4(+), CD16/56(+) (NK cells) and CD8(+) cells in our group of post-menopa usal women. Interestingly, NK activity did not increase significantly despi te an increase in NK cell numbers. PWM-induced lymphocyte proliferation did not change either. In addition, our data support the hypothesis that low v igour in post-menopausal women interferes with the endocrine and immune res ponses to exhausting exercise. In women with complaints of low vigour we fo und lower cortisol responses and higher increments in the proliferative cap acity of lymphocytes as compared to those with high vigour scores. NK activ ity was unrelated to exhaustive mood states. These data indicate that endoc rine as well as immune system activity changes in response to exhausting ex ercise in middle-aged, post-menopausal women. In addition, exhaustive mood states may contribute to cortisol responses and function of peripheral immu ne cells in post-menopausal women following exhausting exercise.