When you train one muscle at a time (like leg extensions), you get a bit better at holding still with that muscle—more than if you train big compound moves like squats. But either way, you get way stronger at moving than holding.

Whether you train with one joint (like leg extensions) or multiple joints (like squats), you get just as strong at the movement you train — but if you train a simple movement, you get a bit stronger at holding still too, compared to complex movements.

Lifting weights with one joint (like leg extensions) transfers better to holding a static position than complex lifts like squats, because it’s easier for your body to use the same muscle pattern in both cases.

For exercises that move just one joint—like bicep curls—lifting heavier weights leads to better strength gains than lifting lighter weights, even if both are done until exhaustion.

Getting stronger at lifting weights doesn’t make you much stronger at pushing or holding something still — they’re like two different kinds of strength, not just one ability measured two ways.

Being strong at lifting weights doesn’t mean you’re strong at pushing or holding something still—even with the same muscles—because your body uses different systems for moving vs. holding.