Why you should care
Because Mother Nature gave half the population a monthly competitive edge.
After finishing fourth in the 4x100-meter medley relay at the Rio Olympics, Fu Yuanhui made sports history. Wincing, she told an interviewer postrace that she had just started her period, leaving her weak and fatigued. It’s a struggle many women know to be all too real. Yet talking about periods still remains taboo among female athletes. But research suggests we might have grounds to be a little louder and prouder about Aunt Flo.
Women who time athletic training to their periods improve athletic performance.
In a new study, women who strength-trained during the first two weeks of their cycle had greater gains in muscle mass, strength and power than those who trained during the last two weeks. Once the provenance of hippie-dippie Mother Moon types, menstrual cycle monitoring could help female athletes optimize their training and minimize the risk of injury.
Most studies on athletic training have focused on men; few have examined how female athletes can use hormonal fluctuations to their advantage. To that end, Lisbeth Wikström-Frisén of Sweden’s Umeå University recruited 59 women to participate in a four-month leg-resistance training program that included vertical jumping to test power and an exercise machine to test strength. The high-frequency portion of the program involved training five times a week, while the low-frequency portion involved training only once a week. Wikström-Frisén’s team assigned the women to three groups. One group completed the high-frequency portion during the first two weeks of each four-week menstrual cycle, while another did so during the last two weeks. A control group trained three times a week for the entire four-month period.
The study is comprehensive and well-controlled, and might have implications for older women.
Women who completed the high-frequency portion during the first two weeks of each menstrual cycle showed significant gains in power, strength and lean body mass in their legs. Those who completed the high-frequency portion during the last two weeks of each cycle did not show significant increases in these measurements. The control group showed increases in strength and power, but not in lean body mass. Wikström-Frisén saw the same trends regardless of whether women were on the pill, which mimics the natural menstrual cycle. Female athletes could use this knowledge to design their training regimens — for instance, scheduling a recovery period during the second half of their cycle to avoid overtraining and injury, Wikström-Frisén, who led the study as part of a doctoral dissertation, wrote in an email.
It’s not exactly clear why women who bulked up on training during the first half of their cycle had an edge, but estrogen likely plays a role. During the first half of the menstrual cycle, estrogen levels peak, while progesterone levels fall. Peter Tiidus of Brock University has found in animal studies that estrogen activates so-called muscle satellite cells to mature and then potentially fuse to existing muscle fibers, synthesizing the proteins muscles need to contract, maintain their structure and perform other crucial functions. (Exercise also activates satellite cells, but estrogen might offer a slight boost.) Meanwhile, estrogen levels fall and progesterone levels peak during the second half of the menstrual cycle. Progesterone counteracts many of estrogen’s effects, which might also include its ability to trigger muscle growth and repair.
To be sure, the findings are mostly relevant to elite athletes, especially those who compete in sports that keep body fat levels extremely low — like distance running and gymnastics— which can lead to low estrogen levels, impairing their ability to build muscle (as well as menstruate and increase bone density, important for preventing osteoporosis). For us mere mortals wondering whether to time our strength training before or after our period, “don’t worry about it,” Tiidus tells OZY. The effects in the study were relatively small — enough to “make the difference between first and second place in the Olympics, but for women training for their first 10K, it probably doesn’t matter all that much.” Still, he says, the study is comprehensive and well-controlled, and might have implications for older women, who experience a steep drop in estrogen as they approach menopause, a major reason why they lose muscle mass faster than men. Exercise could help offset that loss.
Wikström-Frisén’s plans for future research include studying how menstrual cycles affect women with different types of training goals — not just elite athletes, but also women pursuing recreational exercise or undergoing rehabilitation. As #TweetYourPeriod and #PeriodsAreNotAnInsult hashtags shatter the silence surrounding menstruation on social media, Wikström-Frisén’s research is following suit. “It’s a totally natural physiological ongoing event in half the population,” she says. “It is hard to understand why it still is such a taboo.”