If gym guys use an app to switch up their workouts every time, they might enjoy training more — without losing gains in leg strength or muscle size.

If gym guys switch up their workouts randomly every time, they stay more motivated over 8 weeks compared to doing the same routine every time.

If you're already used to lifting weights, using free weights or machines won't make a noticeable difference in how much stronger you get or how fast you can push the weight after 8 weeks of training.

For men who already train with weights, lifting lighter weights to exhaustion can build strength and muscle just as much as lifting heavier weights, as long as the total amount of work done and the effort level are the same.

If you're already trained in lifting weights, whether you use free weights or machines, you'll get about the same strength gains after 8 weeks—as long as you're lifting the same amount, at the same intensity, and moving through the same range of motion.

If young guys lift weights all over their body 3 times a week for 9 weeks, they'll get stronger — no matter if they switch up their exercises or stick to the same ones.