The role of oestrogen in exercise-induced muscle damage.
Year: 2003
Type: dissertation
Abstract: Oestrogen is believed to be a potent antioxidant, with potential membrane stabilising \nand gene regulatory effects. Oestrogen has been shown to be an effective \ncardioprotectant, with for example a lower incidence of atherosclerosis in pre \nmenopausal females compared to age-matched males and in post menopausal \nfemales on hormone replacement therapy compared to age-matched males. What has \nyet to be determined is the extent to which oestrogen can protect skeletal muscle. It \nhas been shown that certain markers of exercise-induced muscle damage (EIMD) are \nlower in females in both animal and human studies, but as yet no conclusive \nevidence from human studies has shown that oestrogen provides a protective \nmechanism against ERvID or whether susceptibility to EIKID varies across the \nnormal menstrual cycle, where oestrogen fluctuations are high. Furthermore, if \noestrogen provides a protective mechanism against EIlVID, it is unknown at which \nphase during the muscle damage and repair cycle this occurs. It is also debatable if \nthe potential inhibitory effects that oestrogen has on the inflammatory response, with \nregard to repair and regeneration of the skeletal muscle are positive or negative. \nThe thesis is comprised of a critical review of the nature of EIMD and the potential \neffects that oestrogen has on the muscle damage and repair cycle. This is followed by \nthree empirical studies which were designed to explore this question. These are \noutlined below: \n \nStudy 1 \n \nStudy one was in two parts. The first part of this study aimed at determining if the \nphase of the menstrual cycle, could in anyway affect eumennorheic (normally \n2 \nmenstruating) females in their susceptibility to exercise-induced muscle damage. An \neccentric exercise procedure (elbow flexor muscle group) was performed on a \nrandomly assigned arm during either the menses or ovulatory phase of the menstrual \ncycle. The contra-lateral limb underwent the same procedure during the alternate \nphase (random assignment determined in which phase the participant was first \ndamaged). Simple markers of EDM were assessed at baseline and every 24 h up to \nthree days post exercise, during both phases. No significant differences were seen in \nany markers of BIMD across phases of the menstrual cycle. \nThe second part of this study investigated whether prolonged ingestion of exogenous \noestrogen, in the form of the combined oral contraceptive pill attenuated any of the \nsymptoms associated with EIMD. The only symptom to show a significant \ninteraction between groups was perceived soreness, with the pill users reporting \nsignificantly (P<0.01) less soreness than the eumennorheic females in the days \nfollowing the exercise protocol. This suggested that oestrogen may modulate the pain \nassociated with EIMD. \n \nStudy 2 \n \nThe second study focussed on gender differences in exercise-induced muscle \ndamage, with particular focus on the secondary symptoms and events which occur \nfollowing ERVID. Male and female participants performed a bout of eccentrically \nbiased exercise. Markers of both EIMD and inflammation were taken prior to the \neccentric exercise and across a 7-day follow up period. Gender differences in the \nresponse to EIMD were seen in creatine kinase activity and mid-thigh circumference, \nwith males showing a larger response on both variables. In addition to this, males \nreported significantly less soreness than females following the exercise protocol. \n3 \nInterestingly, with the exception of neutrophil elastase release, there were no \ndifferences in other markers of inflammation between men and women. Total \nelastase concentration, a marker of neutrophil activation, did not differ between \ngenders. However, elastase release per neutrophil was significantly lower in females, \nwhich may be indicative of gender differences in the inflammatory response \nassociated with EDvID. \n \nStudy 3 \n \nWith the recognition that oestrogen could potentially reduce or inhibit the \ninflammatory response the third and final study investigated whether female skeletal \nmuscle was more susceptible to exercise-induced muscle damage after a second bout \nof eccentric exercise, due to poor regeneration and repair following the initial bout. \nMales and females performed a bout of eccentrically biased exercise. Markers of \nEEVM included creatine kinase, soreness, isometric strength and isokinetic strength \nassessment. The procedure was then repeated two weeks later to determine if gender \ndifferences existed in terms of the repeated bout effect associated with EIlvID. Only \none variable showed a gender x time x bout interaction (P<0.05), that was the fatigue \nindex. It was shown that following the initial bout of damage, males and females \nresponded very differently, with female muscle being less fatiguable in the 48 h \nfollowing damage compared to the males, but with both groups responding very \nsimilarly in the repeated bout. This may be due to differences in gender and their \nresponse to EIlVID, or due to differences in fibre type between genders
Author: Becky Kendall
Language: English
Subfield: Physiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W1743453976