Free weight exercises help you gain muscle strength and size, but machine exercises are much easier to learn. You can quickly increase the weight in machine exercises because the learning curve is smaller, while the risk of injury is lower.
The squat is one of the best lower-body exercises, but the leg press machine is a worthwhile alternative if you need something different. Whether you should use free weights or machines depends on your goals. If you're training for sports, you should probably stick to free weight exercises. They work your muscles, as well as your balance and stability. However, the leg press machine will still make your legs work hard.
If your goals are just to look good or do some basic strength training, the leg machine is a good alternative option to free weight squats. With the machine, you don't have to take the time to learn the movement—all you have to do is sit in the proper position and press with your legs.
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That means if you're in a rush to build up your leg muscles and haven't learned how to properly squat with weight, the leg press is the best alternative. The only thing you need to know is how to properly adjust the distance from the seat to the platform where you press. At the bottom of the movement, your hips and your knees should be in line with each other. It should look like the bottom of a squat position.
Other than adjusting the seat height, there isn't much left to do other than select an appropriate weight. After that you're ready to get on the machine and sit with your back flat against the back rest. Place your feet on the platform as though you were about to squat.
By using different foot placements, it's easy to emphasize different muscles on the leg press machine. If you walk your feet up on the platform and press from there, you'll work your hamstrings and glutes. Walk your feet down, and the emphasis goes to your quadriceps.
When you work out on a machine, especially something that works the lower body, it's safer to fail on an exercise. Failure during a set means that you hit a point where your muscle simply can't contract anymore. Leg presses have a safety catch where you can stop the machine from moving back. In a free weight squat, you either need to have a spotter or ditch the weight mid-rep.
Because it's safer to push to failure on a leg press machine, you can use slightly heavier weight without feeling like you're in danger. You can also do workouts with more reps that eventually bring you to failure without feeling like you're in danger.
Read More: The Average Weight for Leg Press Exercises
Working Around Injuries
The leg press is a better option than free weights if you're injured in the neck, shoulders or back. There is very little stress on your upper body on the leg press because it's not holding any weight. In an exercise such as the back squat, the weight is all resting on your shoulders, neck and back. On a leg press, you can work one leg at a time, reducing the amount of pressure on your upper body even further while still working your leg muscles.