More for less – actually, the same for less
Most people do not get enough physical activity in their lives. Studies estimate that less than 25% of us meet physical activity (PA) guidelines, and despite public health panic, that number continues to shrink. I get why many are reluctant to commit to long exercise sessions, where they likely feel pressured to endure discomfort and get sweaty for some promised health benefit in a distant future. Maybe, just maybe, we build expectations around too much exercise, driving a deeper wedge into already fragile motivations.
A neat study just out (Ji et al., 2024), used pooled US data to uncover flaws in our assumptions about how much activity we should be recommending. This study linked self-reported physical activity data from more than 400,000 individuals (average age 44 years, and just over half female) with death records, all to explore how activity behaviours protected from mortality. The authors describe a long standing gender gap, with females engaging less with physically activity; a trend they say begins early in life. That was a bit of a surprise for me. I had always assumed that women were more active, but that may have been my mistake in conflating the ubiquitous activewear we see with physical activity. Seems there is a lot of wear without the active!
Anyway, back on topic, Ji et al. (2024) found that fewer women (32% versus 43% of men) regularly undertook aerobic PA, and were less likely to engage in strength training (20%) than men (30%). In fact, all major measures of PA were significantly more frequent in men. And here’s where things get interesting – while the greatest mortality benefit for men peaked at around 300 min/week of moderate to vigorous PA (MVPA; with an 18% lower risk of both all-causes mortality and cardiac related deaths), women could get the same benefit with only 140 min of MVPA/week. Women who exercise more, peaking at 300 min/wk enjoyed a 24% lower risk. The pattern was similar for strength training with men reducing their overall risk by 11% compared with for women at 19%. So straight and simple – women get the same exercise health benefits as men, by doing and less, and more benefits by doing the same amount.
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There are several potential explanations for these findings. Males (in general) have measurably greater exercise capacity than female individuals across all ages. Unfair sure, but proportionately more lean body mass, larger hearts, better respiratory apparatus, and larger muscle fibers compared with females. Ok – but muscle mass in women may be proportionately more efficiently improved by strengthened muscles. While there may be greater female sensitivity to disuse loss of muscle, it seems that women are also more sensitive to training stimuli. Overall, females experience greater relative improvements in strength, and this is thought to be a stronger predictor of mortality than the amount of muscle. Sexual differences in muscle fiber type, metabolic, contractile, and dynamic function may also explain some of the differences in responses to the same dose of PA.
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In summary this study shows that females stand to gain proportionately more than male individuals in reduction of cardiovascular and all-cause mortality risk for a given dose of regular exercise. They note that although the existing PA guidelines and recommendations are gender blind. This is great news for females who are already active, and for those thinking about starting. Ji et al. argue that we should be focusing on equalising levels of engagement in physical activity rather than trying to equate specific exercise guidelines. Using their reasoning, I would be cutting those guidelines in half, well at least the aerobic ones, and encouraging a more sustainable routine that can always be built on. We want more females active, and hopefully they will be more encouraged knowing that they can do less.
Reference
Ji, H. et al. (2024). Sex differences in association of physical activity with all-cause and cardiovascular mortality. Journal of the American College of Cardiology, 83(8), 783-793.