We don’t really know if variable resistance training works well for athletes or over long periods—most studies have only looked at beginners and for a few months at most.

Using machines or bands that change how hard they feel as you move might make your muscles work more evenly during an exercise, but that doesn’t always mean you’ll grow bigger muscles faster than with regular weights—especially if you’re just starting out.

If you're new to lifting weights, whether you switch up your weights and reps (variable training) or stick to the same routine (conventional training), you'll build muscle at about the same rate—neither method is better than the other for getting bigger muscles in the first few months.

Whether you use machines that change resistance as you lift or keep the same weight all the way through, after 20 weeks of training, healthy men gain about the same strength and muscle size either way.

If you do the same total number of reps and sets, fancy techniques like drop sets or rest-pause won’t make your muscles bigger than regular training—your muscles grow the same no matter how you structure the sets.

How much you lift in total each week matters more for results than whether you do it in 2 days or 5 days—unless you’re trying to get stronger, then frequency helps a bit.