Changes in maximal voluntary force of human adductor pollicis muscle during the menstrual cycle.

Abstract

1. Muscle strength of the adductor pollicis (AP) was studied throughout the menstrual cycle to determine whether any variation in force is similar to the known cyclical changes in ovarian hormones. Three groups of young women were studied: trained regularly menstruating athletes (trained), untrained regularly menstruating (untrained) and trained oral contraceptive pill users (OCU). In addition a group of untrained young men was studied as controls. 2. Maximum voluntary force (MVF) of AP was measured over a maximum period of 6 months.Ovulation was detected by luteinizing hormone measurements or change in basal body temperature. There was a significant increase in MVF (about 10%) during the follicular phase of the menstrual cycle when oestrogen levels are rising, in both the trained and untrained groups. This was followed by a similar drop in MVF around the time of ovulation. Neither the OCU nor the male subjects showed cyclical changes in MVF.We have shown previously that the maximum voluntary force (MVF) which can be exerted by the adductor pollicis muscle (AP) relative to its cross-sectional area (CSA) is 28 % lower in old than in young people (Phillips, Rook, Siddle, Bruce & Woledge, 1993b). In women this decline in MVF/CSA occurs at the time of the menopause, i.e. at the time when ovarian failure leads to a permanent decline in sex hormone secretion. In postmenopausal women using hormone replacement therapy MVF/CSA is greater than in age-matched controls and not less than that of young women (Phillips et al. 1993b). These facts suggest that oestrogen may have a muscle-strengthening action. If this is correct, and if the action is exerted within a few days, then we could expect to see changes in MVF during the menstrual cycle. It is well recognized that, during the follicular phase of the menstrual cycle, oestrogen levels rise to a peak and then fall during the day or two before ovulation, while during the luteal phase the oestrogen levels remain relatively stable but at a higher level than that at the start of the cycle. In contrast, progesterone levels are negligible during the follicular phase but, after ovulation, rise to a peak during the luteal phase (Moghissi, Syner & Evans, 1972). Therefore, it would be predicted from the hypothesis of oestrogen increasing muscle strength, that a rise in MVF would be seen during the follicular phase of the cycle followed by a fall near the time of ovulation. Moreover, if the action of oestrogen was not opposed by that of progesterone, MVF would remain higher during the luteal phase than at the start of the cycle. This paper reports the results of experiments carried out to test these predictions. We compared highly trained athletes, during their training season, with non-training subjects for two reasons: (1) the highly physically active subjects may have developed oligomenorrhoea or amenorrhoea giving anovulatory cycles with little change in cyclical hormones or force; and (2) physical activity itself may saturate any force effect caused by changes in the levels of s...

The influence of menstrual cycle phase on skeletal muscle contractile characteristics in humans

“…For women not taking oral contraceptives, however, the quadriceps were stronger, more fatiguable and had a longer relaxation time at mid-cycle (day 12-18). Phillips et al (1996) reported a higher adductor pollicis strength during the follicular phase than during the luteal phase, with a rapid decrease in strength around ovulation. They suggested that oestrogen has a strengthening action on skeletal muscle, although the underlying mechanism is not clear.…”

A perspective on current research investigating the effects of hormonal contraceptives on determinants of female athlete performance

“…N et al 34 assessed the response of athletes using various preparations of OCs (n = 13) and athletes not using hormonal contraception (n = 18) to 12 weeks of resistance training. Strength was improved in both groups, with no apparent di erences between groups, although this study did not control for menstrual cycle phase when measuring strength in the control group, which has been shown to a ect force production 36 . In contrast, L et al 35 found that non-OC users (n = 39) gained signi cantly more muscle mass (+3.5%) than OC users (n = 34; +2.1%) following a 10 week training programme.…”

The relationship between oestrogen and muscle strength: a current perspective

“…During the eighties and nineties there was much debate and controversy about the e ects of ovarian hormones on muscle strength in females [1][2][3][4][5] . Researchers used various models of reproductive functioning to investigate this relationship including; the menstrual cycle 6 , the menopause 7 , in vitro fertilisation (IVF) treatment 8 , pregnancy 9 , oral contraceptives 10 (OC's) and hormone replacement therapies 11 (HRT's).…”

“…Since then, several authors have linked cyclical changes in muscle strength, in eumenorrheic females, with uctuations in ovarian hormone levels across the menstrual cycle 3,4,10,[16][17] . However, there is also substantial evidence to the contrary 1,5,[18][19][20] .…”

“…e in uence of OC's on muscle function is also confusing with some authors 16,26 suggesting an e ect and others showing no di erence 4,10 . For a comprehensive review of the literature published between 1980 and 2000 see C and E…”