The major finding of this study was that no significant differences in strength or isokinetic peak torque gains occurred between those using combination OCAs and those not taking exogenous hormones. A number of factors may have influenced the results. The overall sample size was relatively small, and no attempt was made to differentiate between sport participation within the OCA or non-OCA groups. Compliance with OCA prescriptions by subjects was based on self-reporting and was not verified by other means. Additionally, we did not obtain hormonal assessments or differentiate between monophasic and multiphasic combination OCAs or between different progestin agents. Furthermore, no attempt was made to control for menstrual cycle phase during strength or isokinetic testing, which may have affected strength and torque production in the control group as women may show increases in maximum voluntary force production during the follicular phase (32). However, previous studies using isokinetic testing to assess differences in torque production throughout the menstrual cycle have reported no differences between the luteal and follicular phases (11,23). Finally, it was assumed that the results of isokinetic peak torque, 1RM, and 10RM strength testing were reliable based on previous research (4,12,16,26,34), although reliability was not assessed in the present study. Although the present study has some important limitations, it was concluded that the use of OCAs had no effect on strength gains achieved in a preseason conditioning program as practiced at an NCAA Division I institution. However, since this study did not differentiate between various OCA hormonal preparations, it is possible that certain OCAs may affect the expression of strength or power in response to training under different conditions. For example, levonorgestrol and norethindrone have been shown to have both androgenic and antiandrogenic properties (36). However, Burrows and Peters (7) asserted that the androgenic component of current OCA formulations is not great enough to influence strength gains but suggested further research into this contention was necessary. Results of the present study support their supposition that OCA use does not produce androgenic responses beyond those normally seen due to strength training.
Combination OCAs consist of estrogen and progestin components. These agents prevent ovulation through the inhibition of gonadotropin-releasing hormone release from the hypothalamus and luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release from the pituitary. OCAs maintain serum estrogen and progesterone levels at early follicular phase levels throughout the menstrual cycle. Combination OCAs may affect circulating free testosterone levels by influencing ovarian production of testosterone and sex hormone-binding globulin levels. The estrogen component of OCAs generally reduces free testosterone levels, whereas the progestin component has a balancing antiestrogenic effect. The net effect in average women is to reduce free testosterone levels (15). However, since different progestins have various levels of androgenicity, it is possible that various combination OCA preparations may also have different effects on serum testosterone levels. This was not tested in the present study.
As expected, our results identified significant strength gains as measured by 1RMBP and 10RMLE in all subjects who completed a 12-week free weight strength training program. These results are consistent with a previous study on female athletes that demonstrated significant gains in 1RMBP, shoulder press, and leg press torque production following a similar 12-week strength training program (3). Similar strength gains in female athletes have also been reported in previous training studies (8,21,25). Our results also showed that OCA users and NOCA users developed significant gains in isokinetic knee extension torque but not in isokinetic bench press torque production. Because the 12-week resistance training program in the present study used constant external resistance, increases in isokinetic peak torque may not be expected based on the findings of Pearson and Costill (29) who previously reported that strength gains from isokinetic and constant external resistance exercise training were specific to the training modality.
Although our results do not indicate that OCAs affect torque production in women athletes participating in a resistance training program, OCA use may provide other potential advantages in women athletes. OCAs help maintain stable gonadotropin levels at early follicular phase levels (17). The follicular phase has been associated with improved aerobic performance (23), muscle strength (32), and enhanced growth hormone levels (14). Additionally, increases in strength and muscle cross-sectional area were greater when using menstrual cycle-triggered training, in which subjects train more frequently during the follicular phase and less frequently during the luteal phase, as opposed to regular training throughout the menstrual cycle (33). Finally, OCA use has been shown to attenuate delayed-onset muscle soreness following exercise (37).
Oral contraceptive agents suppress ovulation, the preovulatory LH/FSH level surge, and the relatively increased progesterone levels of the luteal phase. Progesterone has well-known thermogenic effects on the female body. Mean exercise heart rate, metabolic rate, aerobic performance, and perceived effort may all be negatively affected by the resultant higher body core temperature (33). Peak core temperatures occur during the luteal phase when progesterone levels are elevated when compared with the follicular phase (18). Since OCAs stabilize serum estrogen and progesterone levels, they provide some consistency of thermoregulation throughout the menstrual cycle and facilitate the ability to exercise consistently throughout the cycle.
Oral contraceptive agents may adversely affect athletic performance. The use of OCAs has been associated with delayed strength recovery following eccentric exercise (35) and may have negative effects on muscular strength (30) and aerobic exercise performance (9,22,28). Further, the cost and potential risks and side effects of OCAs, including thromboembolic disease, hypertension, nausea, breakthrough menstrual bleeding, edema, and headache, must be considered.
To our knowledge, this is the first study that prospectively examined resistance training-induced strength gains in athletes who are masked to the main outcome of interest, i.e., differences between OCA users and NOCA users. The present study failed to identify any difference in repetition maximum or isokinetic torque production gains between women collegiate athlete OCA users and NOCA users who participated in a 12-week strength development program. It was concluded that, within the limitations of the study, the use of combination OCAs did not provide sufficient androgenic effect to increase strength gains beyond the stimulus of the training protocol.
The use of combination oral contraceptives (birth control pills) did not positively or negatively affect strength gains in collegiate women athletes participating in a 12-week preseason supervised strength training program. Therefore, the use of combination OCAs, as used in this study, did not appear to function as anabolic agents. However, it remains possible that certain types of combination oral contraceptive pills or other forms of hormonal contraception may potentially affect strength gains. Oral contraceptives have a number of potential side effects and complications as well as potential benefits that may negatively or positively affect an athlete's performance.
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