Effects of a sexual assault scenario on handgrip strength across the menstrual cycle
Introduction
Pregnancy as a result of rape carries high costs for a woman: (1) inability to exercise mate choice, (2) lack of provisioning and protection by the father, (3) possible abandonment or punishment by her current mate, and (4) reduced likelihood of attracting future mates Shields & Shields, 1983, Thornhill & Thornhill, 1983, Thornhill & Thornhill, 1990. The risk of conception ought to vary as a function of where the woman was in her menstrual cycle at the time of the assault. Did selection operate during human evolutionary history to produce mechanisms that lower the likelihood of conception as a consequence of rape? This question breaks down into two corollary questions. First, do women engage in behaviors that reduce the likelihood of rape during the ovulatory phase of their menstrual cycles? Second, are women in the ovulatory phase, when the risk of conception is greatest, better able to resist, fend off, and/or deter instances of sexual assault?
At the time of sexual assault, women are less likely to be in the ovulatory phase of the menstrual cycle Morgan, 1981, Rogel, 1976, despite the fact that women in their reproductive years are more likely to be raped than prepubertal and postmenopausal women (Thornhill & Thornhill, 1983). One reason for the disproportionately small number of women who are raped during the ovulatory phase is the finding that ovulating women engage in less risk-taking behavior (Chavanne & Gallup, 1997).
Given the higher costs of conception as a consequence of rape, the question we attempted to examine in this study is whether a woman's capacity to resist sexual assault varies across the menstrual cycle.
Section snippets
Methods
These methods were approved by the Institutional Review Board at the State University of New York at Albany and participants were treated in accordance with ethical guidelines for research with human participants. Female college students (N=232) between the ages of 18 and 35 (mean age 19.4) from introductory psychology classes at the State University of New York at Albany received course credit for their participation in this study.
Participants were asked, in the following sequence, to provide
Results
There were no differences between groups in pretreatment handgrip strength, F(4,187)=1.13. Since the difference between the two posttreatment measures did not vary across menstrual phase or experiment context, the difference between the pretreatment and the average of the two posttreatment handgrips was used in the following analyses. Dominant and nondominant handgrip measurements were summed as a measure of total handgrip strength, resulting in an interaction between menstrual phase and
Discussion
Previous research has produced conflicting results in performance across the menstrual cycle. Studies of nonendurance-based tests of strength show no cycle-dependent differences in handgrip strength (e.g., Allen & Bailey, 1982), knee extension and flexor strength (Dibrezzo, Fort, & Brown, 1988), or isometric strength (Petrovsky, LeDonne, Rinehardt, & Lind, 1976); however, others report cycle-dependent fluctuations in standing long-jump distance and handgrip strength (Davies, Elford, & Jameison,
Acknowledgements
We thank Inverness Medical, 200 Prospect Street, Waltham, MA 02453 for donating the ovulation test sticks and Donald Graves and Keith Hutchinson for assistance with the reaction time software. Also, we thank Kristin McGrath, Malinda Stockwell, and Andrea Thorne for assistance in data collection.
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