Every day, more women are moving from the cardio room to the weight room. It’s a welcome transition; getting stronger can transform their self-esteem, confidence and self-efficacy.
Supporting your female clients’ strength-training ambitions is fundamental to their long-term success. Women and girls enjoy a wealth of benefits from resistance exercise:
- reduced injury risk;
- better cardiovascular health;
- stronger bones;
- protection against diabetes; and
- less inflammation, to name a few.
As more women flock to strength training, however, fitness professionals face a host of challenges. For starters, the research on weight training for women is relatively new, and there are fewer studies on women than there are on men. Also, the physiological differences between genders is either misrepresented or not discussed.
We aren’t that much different. In equally trained men and women, research finds most strength differences result from differences in muscle size, not gender (Bishop, Cureton & Collins 1987). These findings suggest that a man and a woman with the same muscle size should display the same amount of strength. Thus, we can retire terms like “toned” and “girl pushups&rquo;—and the pictures of pink dumbbells—because women should and can do the same exercises your male clients do. You, of course, already know this.
You should consider two crucial points, however:
- Women and men have different muscular fiber type compositions, making women less prone to fatigue (Hunter 2014).
- Female sex hormones, especially those involved in the menstrual cycle, can affect program timing and recovery (Sung et al. 2014).
Understanding these differences is pivotal to building programs that will help your female clients achieve muscle growth, strength gains and training success.
Fiber Types in Women vs. Men
Type I and Type II Fibers
Generally speaking, the skeletal muscles of men are larger than those of women, and, in men, some muscles possess “a greater proportional area of metabolically and functionally faster muscle fibers,” whereas in women there is “a greater proportional area of the ‘slow’ type I fibers” (Hunter 2014). The higher concentration of type I fibers makes women more resistant to muscle fatigue. Men have a higher glycolytic capacity based on their larger concentration of type II fibers, priming males for quick, explosive activities like sprinting and weightlifting.
While muscle fiber type plays a large role, it is important to remember that the tendency to fatigue depends a lot on task conditions, including:
- contraction type, speed and intensity;
- the muscle group involved;
- environmental conditions; and
- state of arousal (Hunter 2014).
The makeup of muscular tissue affects the energy substrates that each gender uses. Women typically carry 6%–12% more fat than men. Women are also better at handling fat and using it for energy during exercise, which spares muscle glycogen and decreases exertion ratings—again, playing into fatigue resistance. Additionally, women are more sensitive to insulin across the entire body and are better able to take up glucose (Lundsgaard & Kiens 2014).
If muscle growth is a female client’s main goal, keep in mind that she is probably more resistant to fatigue than a male client would be. Programming sets in the 6- to 10-rep range seems to yield maximal muscle growth (Schuenke et al. 2012) and maximal increases in strength.
Because women can theoretically handle more work, your general-population clients might benefit from harder-intensity training sessions with supersets and timed rest periods. Consider challenging them to fatigue a little faster than they normally would, since you need to push them beyond their comfort zone to achieve muscle growth.
Sex Hormone Differences
Women’s menstrual hormones fluctuate throughout their cycle, which usually lasts 28 days (hormonal contraceptives and other issues can alter the cycle). Hormonal fluctuations play a huge role in strength training, a reality only recently discussed in academic literature. By opening up this conversation with your female clients, you can tap into their strengths a little more and use biology in their favor (Sung et al. 2014).
The menstrual cycle has four phases:
- menstrual (days 1–5)
- follicular (days 1–13)
- ovulation (day 14)
- luteal (days 15–28).
The luteal phase triggers sharp hormonal changes—progesterone peaks and then plunges, along with estradiol. Hunger increases, moods change suddenly, core temperature rises, and more calories are burned; in fact, basal metabolic rate has been shown to increase by as much as 9% (Webb 1986). In this phase, symptoms of premenstrual syndrome often discourage interest in going to the gym.
The follicular phase, by contrast, is the time for women to really push themselves in hard workouts because estrogen hits its peak at this time, improving mood, energy and strength.
Estrogen vs. Testosterone
These sex hormones have the most impact on the relative strength of women and men. Men have much more testosterone, affecting their baseline strength. Thus, men start out stronger with higher absolute strength, but relative strength gains are about the same for both genders.
Estrogen, on the other hand, has proved to have some anabolic and protective effects against various injuries and diseases. Within muscle, estrogen has been shown to influence contractions and postexercise muscle damage by acting as an antioxidant and a stabilizing membrane and by binding to estrogen receptors (Enns & Tidius 2010). Estrogen also has regenerative properties, which is why combining exercise and hormonal therapies can increase lean tissue mass (Velders & Diel 2013).
For a sample program design, see “A Woman’s Place Is in the Weight Room” in the online IDEA Library or in the February 2019 issue of IDEA Fitness Journal). If you cannot access the full article and would like to, please contact the IDEA Inspired Service Team at 800-999-4332, ext. 7.
Bishop, P., Cureton, K., & Collins, M. 1987. Sex difference in muscular strength in equally-trained men and women. Ergonomics, 30 (4), 675–87.
Enns, D.L., & Tidius, P.M. 2010. The influence of estrogen on skeletal muscle: Sex matters. Sports Medicine, 40 (1), 41–58.
Hunter, S.K. 2014. Sex differences in human fatigability: Mechanisms and insight to physiological responses. Acta Physiologica, 210 (4), 768-89.
Lundsgaard, A.M., & Kiens, B. 2014. Gender differences in skeletal muscle substrate metabolism—molecular mechanisms and insulin sensitivity. Frontiers in Endocrinology, 5, 195.
Schuenke, M.D., et al. 2012. Early-phase muscular adaptations in response to slow-speed versus traditional resistance-training regimens. European Journal of Applied Physiology, 112 (10), 3585–95.
Sung, E., et al. 2014. Effects of follicular versus luteal phase-based strength training in young women. SpringerPlus, 3 (668).
Velders, M., & Diel, P. 2013. How sex hormones promote skeletal muscle regeneration. Sports Medicine, 43 (11), 1089–1100.
Webb, P. 1986. 24-hour energy expenditure and the menstrual cycle. The American Journal of Clinical Nutrition, 44 (5), 614–19.
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