If you're already used to lifting weights, whether you use free weights or machines, you'll likely feel about the same amount of less joint pain in your arms and legs after 8 weeks of training.

If you're a guy who already lifts weights, using free weights or machines for 8 weeks will both help ease joint pain in your arms and legs — and neither one is better than the other at doing it, as long as you lift carefully and move through the full range of motion.

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.

Doing extra arm isolation exercises like bicep curls and triceps extensions doesn't help you get stronger or build more arm muscle than just doing big compound moves like bench presses and pull-downs — at least not for beginners after 10 weeks.

Using light weights for arm exercises can make your arms slightly more muscular, but using light or heavy weights for leg exercises doesn’t change leg muscle size in young women who haven’t trained before.