Across 4,871 tests, submaximal equations put people in the right fitness third 51% of the time. Guessing gets 33%. Here is what a real test is, and when you actually need one.
Something real does happen: blood levels of the vitamins go up. What has not been shown is that it buys you anything. The biggest brand's own trial ran thirty people for four weeks.
A diet nobody markets beat 21 other lifestyle interventions. The best exercise was a wall sit. And the supplements sold for blood pressure came last, by their own numbers.
The US reference standard is 22,379 measured tests. Three things move your percentile before you train: which machine, which edition of the chart, and whether anyone measured you at all.
Fitness falls about 4.0 mL/kg/min a decade. Interval training adds about 5.5. The catch is that the device on your wrist misses by more than that.
A 2018 review of 99 studies set the common recovery methods side by side, and massage came first for soreness and fatigue. Whether it makes you any stronger or faster afterwards is unproven, which is not the same as disproven.
In pooled trials, compression boots ease soreness a little and show nothing clear for strength, power or the blood markers a flush should clear. Most of the trials had no dummy treatment to compare against.
In pooled trials, cold water eased soreness for up to four days after muscle-damaging exercise. It has not clearly beaten warm water, and used straight after lifting it can blunt muscle growth, by an amount that is small and not yet certain.
The big gum effect in the 2024 review came from two small trials in 70 children and teenagers. In two eight-week trials in adults, swishing plain water did as much for bleeding gums, and where tooth colour was compared fairly, oil did no better than water.
The sleepy girl mocktail runs on a study that finished with eight completers. Pooled, ten trials of tart cherry show no clear effect on sleep, and the recovery evidence, though better, is not good.