Edith Cowan University research revealed that muscle strength benefits are seen with consistent, short exercise sessions. Participants performing a three-second eccentric bicep contraction thrice weekly saw strength improvements. Daily 20-minute exercises might be more beneficial than a single 2-hour weekly session. Regularity, even in short durations, is key to health benefits.
3 SECONDS every other day?!?!?
Daily 20-minute exercises might be more beneficial than a single 2-hour weekly session
Because 7*20 minutes is more than 2 hours. :)
While this is true, it is not the reason.
Your body gets stronger during the recovery period AFTER exercise, not during the exercise (technically). During recovery your body builds back a little stronger than before the exercise so that you're more capable of handling the same effort next time. After your body has had time to recover, you start detraining slowly.
Keeping your body in a more consistent state of recovery (within reason, you don't want to overdo it of course) is more beneficial than allowing your body time to fully recover and then slide back a bit before your next effort. So moderate exercise more regularly can be said to be more beneficial because you have just enough time to recover with minimal backsliding.
Note: I've simplified and left a LOT of science out of this explanation in the interest of brevity. Please don't come for me. I'm just a guy who likes to exercise and learn about exercise.
Welp, time to start a 20 minutes 6 days a week study for parity!
If the answer is anything other than never, I’m screwed.
Evolutionarily, it makes sense if you're pushing a muscle to 100% exertion, even for only a few seconds a week.
Otherwise, animals would have to spend a large amount of energy to maintain or increase muscle mass, which is wasteful and inefficient — the species who needed more energy to maintain muscles are likely extinct or limited in number.
There's another element to this. Muscle tissue is metabolically expensive, so it's beneficial for an organism to limit muscle mass to only as much as it needs to succeed, thus reducing how much food is necessary. There's actually a protein, myostatin, that directly works to inhibit muscle growth. Some specific breeds of cow lack this; search up Belgian Blue cattle for a look.
Yes. The key difference is the near 100% exertion. If the muscles are used to they're maximum on a regular basis, the body will consider them necessary for survival.
If you suddenly dropped the weight by 20%, so that you exert those muscles less, you would expect them to gradually weaken by a similar margin over time; eventually, to the point that lifting the 80% weight would require near 100% exertion.