Overview
Post-menopausal women who request to begin hormone-replacement therapy (HRT) are directed to the research team. The participants are tested before beginning HRT, after two months of HRT, and five months of HRT. Tests include strength performance, central nervous system functioning, body composition, resting metabolic rate, and vascular screening. The participants are provided a 12-week training intervention (2 x strength, 2 x endurance per week) that can be voluntarily followed between tests at month 2 and 5. Compliance with the training program is recorded. A minimum of 15 participants are needed a priori, but the investigators aim to recruit and test 20 women.
Description
Study aim: To determine cortico-reticular functioning during low and high female sex hormone, estrogen and progesterone, concentrations.
Hypothesis: Greater functioning/response during neurophysiological tests will occur in the presence of high compared to low estrogen concentrations accompanying greater force production capacity. In addition, pathways reliant on a greater number of synapses, i.e. cortico-reticulospinal, will demonstrate the greatest difference between hormone concentrations.
Justification: Several studies in monkeys and humans suggest that the methodology employed is sensitive to distinguish between high and low force production capacity. Estrogen is a neurotransmitter agonist exerting its influence at least via glutamate and GABA interneuron functioning, respectively.
The MENSA study is a locally administered trial where volunteers who request to be put on combined hormone replacement therapy will be recruited through cooperation with gynaecologists in the Jyväskylä area. Participants visit the University of Jyväskylä laboratories 1-5 days before beginning treatment (baseline), 2 months after beginning treatment and 5 months after beginning treatment having completed a 12-week non-supervised exercise intervention.
The experimental sessions will be conducted in the morning (beginning at approximately 7 am) following an overnight fast, and the time of the day kept constant for each individual participant (± 1 h). The posteriori measurement of serum follicular-stimulating hormone, estradiol and progesterone concentrations will be used to verify the hormonal status of the participants.
A recent study showed that a sample of 12-15 participants would be expected to lead to moderate-to-large (0.2-0.9) effect sizes in the tests of cortico-cortico and cortico-reticular functioning. The target muscle is the biceps brachii performing voluntary unilateral isometric elbow flexion actions. MENSA aims to recruit 20 females; this attempts to overcome potential reduced sample size through drop-out or measurement/technical error, as well as sufficiency for detection of possible changes in secondary outcome measures.
Eligibility
Inclusion Criteria:
- at least 6 months since their last period but no more than being 5 years post-menopausal
- basal follicular-stimulating hormone concentration \> 30 IU/L (confirmed post-recruitment)
- willing to start combined hormonal treatment
- womb and ovaries intact with normal functioning throughout reproductive age
- willing to provide informed consent
- does not have any of the exclusion criteria for TMS measurements according to Rossi et al. (2021 Clin Neurophysiol. 132(1):269-306.) (i.e. arterial hypertension, heart attack/seizure history, migraine, pacemaker or cochlear implant or other implanted metal/electronic device)
Exclusion Criteria:
- classified as excessively obese via BMI assessment (i.e., \>35 kg/m2)
- intra-uterine device usage during transition to menopause
- cardiovascular or skeletomuscular disease preventing strenuous physical activity
- smoker
- diagnosed psychiatric illness
- epilepsy
- other diagnosed injuries/illness affecting the neuromuscular system
