Health Claims

Trans women runners get slower over time after starting hormone therapy, especially in longer races — their race times go up by about 14-17%, while sprints are less affected.

One transgender woman cyclist on hormone therapy for a year might have lost some physical edge over cis women cyclists, but her performance changed in different ways depending on the type of test.

A female-to-male cyclist started hormone therapy, and within a year, some of her performance numbers looked more like other women's, while others didn’t — showing a mix of changes.

A female-to-male cyclist saw her strength, jumping power, and stamina drop after a year of hormone therapy as part of her transition.

Trans women on hormone therapy might not jump as high as cis women.

Trans women on hormone therapy perform just as well—or just as poorly—as cis women in sports, with no real difference between them.

Depending on how fast you lower weights during strength training, your muscles might work together differently — some fast techniques make opposing muscles activate more, others make them activate less.

If healthy guys train one arm with heavy weights three times a week for three months—whether they push to total muscle exhaustion or not—they’ll get stronger, their muscles will grow, and their brains will activate those muscles better.

If you're lifting weights at about 85% of your max for 12 weeks, going until your muscles can't do another rep doesn't make you stronger or bigger than stopping just before exhaustion — you'll still get great results without hitting failure.

For older guys who are healthy, doing about half as many reps as they possibly can during strength workouts is enough to get the best results for muscle and nerve performance—especially if they also do cardio.

For older guys doing strength and cardio workouts, their leg muscles only get bigger if they do enough total exercise—how close they push themselves to failure during each set doesn't matter, as long as the overall amount of work is high enough.

For older guys who do both strength and cardio workouts, pushing their muscles to the max on every set doesn’t help them get stronger or faster than stopping just short of exhaustion.

If untrained guys do leg exercises to failure using medium-heavy weights, going slow or going a bit faster on each rep gives about the same strength gains.

When untrained guys do leg extensions with a medium weight until they can't do any more, moving faster (2 seconds per rep) makes their quads work harder for most of the movement — but moving slower (6 seconds per rep) makes them work harder right at the end. So, how fast you lift changes which part of the move your muscles feel most.

If untrained guys do leg extensions slowly (6 seconds per rep) vs. quickly (2 seconds), they’ll push harder at the end of the movement with the slow version, but harder at the start with the fast one — so speed changes where you’re strongest during the lift.

If new guys do leg exercises to failure using medium weights, slowing down the movement doesn’t make their muscles grow more than doing faster reps — both ways work about the same.

If new guys do leg exercises with slow reps (6 seconds) instead of faster ones (2 seconds), they might get stronger in a specific knee position—even if they do the same number of sets and their muscles grow the same amount.

If a woman who's already fit does strength training, doing 5 to 10 sets per muscle each week might build more muscle than doing even more sets—like 15 or 20. Sometimes, more isn't better when it comes to muscle growth.

If women who already work out do too many sets each week, they might gain less muscle and strength than if they did fewer sets.

If you're a woman who's already been working out, doing 5 to 10 sets of strength training per muscle group each week seems to be enough to build muscle and get stronger over half a year — doing more doesn't seem to help extra.

When researchers combine few studies in a review, common statistical tests often miss signs that some results were hidden — making it look like there's no bias when there might actually be.

The more studies a meta-analysis includes, the more likely it is to show 'statistically significant' signs of bias—even if there's no real bias, just because there are more studies.

When scientists use certain tests to check if a review of studies is missing some results, those tests don't work as well if there aren't many studies in the review — they miss problems about a third more often when there are only a few studies.

If young, healthy guys do leg workouts twice a week for six weeks, they get stronger — and doing lighter weights for more reps works about as well as heavier weights for fewer reps, except for hamstring curls, where more reps seem to help more.