The menstrual cycle implies a basic difference in the biology of women and men but the
effect of the hormonal variation on training protocols and physical performance is still
not fully understood. Despite no existing evidence, the advice to periodize exercise
according to the menstrual cycle has been widely spread among elite athletes, coaches,
and sports federations. The advice is based on underpowered studies with considerable
methodological weaknesses regarding determination of cycle phase, inclusion of athletes
and lack of adequate control groups.
The purpose of this randomized, controlled study is to evaluate the effect of exercise
periodization on aerobic fitness during different phases of the menstrual cycle. Further,
the effect will be related to premenstrual symptoms, body composition and skeletal muscle
morphology, sex hormone receptors, metabolic enzymes, and markers of muscle protein
synthesis. This study will be well controlled and follow methodology recommendations for
menstrual cycle research in sports and exercise.
Female athletes of fertile age will be randomized to different training regimens during
three menstrual cycles (12 weeks):
Group A: Training three times a week throughout the menstrual cycle. Group B: Follicular
phase-based training five times a week during the follicular phase and thereafter once a
week during the luteal phase.
Group C: Luteal phase-based training five times a week during the luteal phase and once a
week in the follicular phase.
The exercise will consist of high intensity intermittent spinning classes. Assessment of
aerobic fitness and power will be performed at baseline, and again after three completed
menstrual cycles. On the same day, body composition will be examined by DXA and blood
samples will be collected for analysis of hormones and binding proteins. To confirm
menstrual cycle phase, blood samples will be collected for hormone determination, and
urinary stick will be used for detection of ovulation. Subjective ratings of menstrual
cycle related symptoms will be performed every day. In a subgroup of women, muscle
biopsies will be collected from m vastus lateralis at baseline and at the end of the
study. This study will contribute to improved knowledge about exercise periodization in
relation to the menstrual cycle. Well-grounded data is crucial to give evidence-based
recommendations to female athletes when planning their training protocol to optimize
training results and performance.
