If you're looking to isolate a certain muscle-the hamstring, for example-using a machine is an ideal option. But if you want to work more muscles simultaneously-the key to staying strong over the long term, according to experts-free weights are what you need. Using free weights strengthens your whole core, says Busch of Boulder's Body Balance gym.
Free weights can also work your muscles more completely by allowing a larger range of motion. (With most machines, you're locked into a specific, simple movement, such as straight up and straight down.) Trainers say this more complete movement is a great way to work out because it's comparable to how we move on the hill and throughout our daily lives.
Free weights also improve balance, a crucial component for staying strong and upright on the slopes. You have to use balance every time you pick up a weight, says Susan Moses, a personal trainer and the ski school director at Belleayre Mountain in Highmount, N.Y.
But there are drawbacks to free weights. Because they're more complicated to use than machines, you need more training to learn proper form. It's also easier to get hurt with free weights, and when you use them you usually need a spotter.
For the best-rounded workouts, incorporate both free weights and machines into your weekly routine. As Busch attests, the two are complementary and, used together, can keep you primed for the slopes.