Gyms contain a machine to work every conceivable muscle in your body. The idea is to provide something for everybody, meeting as many peoples’ exercise needs as possible so they’ll be willing to pay for a gym membership. But not all of the leg machines in the gym are worth your time. Stay away from inner and outer thigh machines, for example. They work muscles best worked with free weight exercises, so focus on multi-joint or large muscle group development, instead, when you use leg machines at the gym.
The leg press works your quads, hamstrings and glutes together in a multi-joint movement. Doing squats works the same muscles, plus your core, forcing your body to stabilize the extra weight you’re lifting. But squats require greater technique and expose you to greater risk of injury, if done incorrectly, than the leg press. This makes the leg press ideal for beginners just learning lifting techniques or anyone that wants to move a lot of weight for building mass, with relatively less risk of injury.
Avoid the inclined leg press machine, if possible, because it’s very easy to flatten your back too much when pushing large amounts of weight on this machine. If you must use the inclined leg press, or when lifting large amounts of weight on any leg press, focus on maintaining the natural curve in your spine. Placing a lumbar roll in the small of your back can help you maintain proper posture.
Weak hamstrings, the three muscles in the back of each thigh, are a common muscular imbalance that puts you at increased risk of knee injury and instability. The leg curl machine isolates your hamstrings, allowing you to strengthen them until they’ve “caught up” with your quadriceps instead of perpetuating the muscular imbalance. According to ExRX.net, your hamstrings should be more than 56 to 80 percent as strong as your quads, depending on your population.
The leg extension machine isolates your quadriceps, the large four-muscle group on the front of your thigh. Although this muscle is often stronger than the hamstrings to the point of imbalance, and may not need to be strengthened individually, the leg extension machine is still ideal for building definition in the quads. If one leg is weaker than the other, you can use the leg extension machine to work that quad individually, helping develop it to match the other leg’s strength.