Monday, August 27, 2007

Proper Range of Motion Part 2: Leg Press

A few years ago I met an enthusiastic young man just starting out lifting. He carried a book containing different exercises around the gym with him, studying form between sets. Consequently, he had excellent technique for most exercises.

Somehow, the topic of leg press came up one day. For building practical strength throughout the body, the leg press is inferior to the squat and deadlift, but for raw leg power, nothing beats it. Without the need to balance, you can throw every bit of strength into it, and while squat won't increase your leg press, leg press will allow you to improve your squat more quickly. However, this is one exercise that the young man avoided.

It made his lower back hurt.

This confused me for a long time. It wasn't until I watched a trainer on Fit TV demonstrating the leg press that I understood: too great a range of motion!

The man on television, a very well paid trainer with his own program, said that at the bottom of the exercise, the thighs should touch the chest. Consequently, his lower back rolled away from the seat.

Unlike the squat or deadlift, the leg press isn't a good core-building exercise. With your butt pressed firmly into the corner of the seat, there is little pressure on your lower back, probably just enough that your lower back is flat against the seat, unlike in a bench press where your shoulder blades and glutes would be the two points on the bench. You are able to handle massive weights because your lowerback isn't involved. What would happen if all that weight were suddenly transferred to your lower back? Pain or injury.

That's exactly what happens when your lowerback rolls off the back of the seat.

Your lower back is then suddenly between the 2 points of contact: your upper back against the seat, and your feet suspending many hundreds of pounds above you. And it's supporting all that weight in a curled position.

You'd never purposefully curl your back under a squat or a deadlift, because no one goes looking for a spine full of herniated disks. But you'll frequently see descriptions of the leg press in which the lifter is tacitly encouraged to curl their spines under twice the weight they can squat.

So when should you stop the negative portion of the movement? Your knees should be at approximately a 90 degree angle at the bottom. It is impossible to give the exact angle because of several determining factors:

1. The position of the seat back. Largely because your hamstrings attach across two joints, the knees and the hips, the lower you lay the back down, the further you'll be able to lower the weight without straining your lower back. However, it will also increase the chance you'll be squeezed out the back of the machine like a slippery bar of soap.

2. The flexibility of your glutes and hamstrings. How well can you touch your toes? This is a great indicator of how far you'll be able to lower the leg press sled.

With practice, you'll be able to feel when your lower back is going to roll up off the seat. Then you'll be able to leg press safely.

Dominant body builder Ron Coleman leg pressing 2300 pounds, for reps

Next: Lat Pulldown

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