If you only work out one leg with resistance training, that leg gets stronger, but the other leg doesn’t get stronger at all—even if you don’t train it.

If you lift heavy weights (80–85% of your max) instead of doing lots of lighter reps (60% of your max), your legs get stronger faster — after 6 weeks, you’ll likely gain 5–6 kg more in leg strength.

When people train one leg at a time, that leg gets much stronger than the other leg, even if the other leg didn’t do any training.

When guys who don't usually exercise try a special workout called pre-exhaustion training, they get 17% stronger in their legs—that's more than the 11% boost from regular workouts, probably because the special training targets the muscles more directly.

To get stronger, it matters more how heavy the weight is than whether you push to your absolute limit—lifting heavier weights makes you stronger, no matter if you stop short of failure.

If you're a young guy who already lifts weights, doing workouts until you can't do another rep for 12 weeks will make your legs and shoulders just as strong whether you use light or heavy weights—but for the bench press, heavy weights make you stronger than light ones.