Sex and CrossFit

As a carnivore doing CrossFit, I have issues with maintaining energy. I have a whole post on it here. Thing is, I’ve looked at research that says people can do high-intensity training while on a very-low carb diet with few problems. “People” being 20-something year old men.

But finally, I stumbled across some research that addresses the sex differences in metabolism and muscle tissue, and even touches on age differences, such as for post-menopausal women. We need more of this research to include sex and age differences.

I entered a new masters category this season.

Muscle metabolism and atrophy: let’s talk about sex, a 2019 review, emphasizes how research including sex differences is pursued far less than research normalized on men. The researchers blame the failure of many clinical trials on the fact research is done on men, but then trialed on both men and women. I really expect more from those who call themselves scientists.

The focus of this paper is on applications for drug therapy. I don’t care about drugs, but unfortunately, that’s pretty much all that drives research these days. Still, there are some interesting points:

  • women lose muscle faster from disuse than men, men lose more from inflammation, which suggests women need to work out more regularly than men, but men suffer more severe wasting from cancer
  • women have more mitochondria, burn fat preferentially, and have more oxidative fibers, while men have more glycolytic fibers, which suggests women handle endurance exercise better and men high-intensity, yet when stressed, women’s mitochondria produce less ATP than men’s, so more may not mean much in the long run
  • estrogen mediates anabolism and promotes mitochondrial energy in women so that postmenopausal women have smaller muscle mass and lower energy output, but estrogen or testosterone injections increase protein synthesis
Muscle Phenotype (From Muscle metabolism and atrophy: let’s talk about sex)
Mitochondrial Differences (From Muscle metabolism and atrophy: let’s talk about sex)
Hormonal Differences (From Muscle metabolism and atrophy: let’s talk about sex)

Abstract: Skeletal muscle health is a strong predictor of overall health and longevity. Pathologies affecting skeletal muscle such as cancer cachexia, intensive care unit treatment, muscular dystrophies, and others are associated with decreased quality of life and increased mortality. Recent research has begun to determine that these muscular pathologies appear to present and develop differently between males and females. However, to our knowledge, there has yet to be a comprehensive review on musculoskeletal differences between males and females and how these differences may contribute to sex differences in muscle pathologies. MUSCLE METABOLISM AND ATROPHY: LET’S TALK ABOUT SEX

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