Leg Curl Help?!

Leg Curl Help?

At my gym there is a machine called the leg curl. Will that make my legs stronger so I can run better/longer/faster?

The leg curl machine is what's known as an "isolation exercise." Basically that means it isolates one specific group of muscles -- in this case your hamstrings -- and removes the assistance of other stablizing muscles like your quads, glutes, and core (abs and lower back.)

Isolation machines and exercises are usually better performed by advanced weight trainers who need to etch out extra mass or definition in a particular set of muscles after building a foundation. And even then, they are no substitution for compound, multi-joint exercises like squats, lunges, leg presses or deadlifts.

Consider this: These machines usually rely on only one joint for pivoting. In the case of the leg curl, it's your knees. However, when running, you actually pivot at three places: your hips, your knees and your ankles.

It's usually more effective to work all of the major muscles in your legs, than to isolate out one or two. Over reliance on isolation exercises also extends your time in the gym, because to work your legs completely, you would need to perform three isolation exercises: one for your quads, one for your glutes and one for your hams. A good, full-range squat will work all of those groups (and your core, to boot) with a single set of exercises.

One place that isolation exercises can come in handy is in correcting imbalances that may have developed over the years. For example, many people have over-developed quads and under-developed hamstrings. This can cause all kinds of issues, including back pain and increased risk of injury. Isolation exercises can help you bring up a lagging body part. But once you get that balance back, you'll want to return to compound movements for the majority of your exercises.

If leg development, strength and endurance is what you're after, focus on squats, lunges and deadlifts, and skip the machine. You'll get better results.

Best of luck!