Gym machines are tricky in that they can range from the extremely useful to a complete waste of your time.

It's not always easy to see the difference and we've criticized machines a lot in the past for not being nearly as functional or as effective as free weights. But they're not all bad. In fact, if you suffer from joint pain, are recovering from an injury, or just feel as if you need a break from free weights, some machines can do your muscles good.

Here are a few of our favorite machines to use at the gym and the best exercises to do using them. Or if you'd rather skip the machines altogether, check out these ultra-effective at-home workouts.