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 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 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.

In adults who regularly lift weights, performing workouts close to failure or with some reserve in the last rep produces similar improvements in how long they can sustain effort, with no meaningful difference between the two approaches.

When guys who regularly lift weights do more sets of squats and leg exercises in one workout, they feel like they worked harder afterward.

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.