The truth about sports, nutrition and pain!

Posts tagged ‘compression force’

Abdominal part 2

Last week we talked a little about certain myths that exist around the abdominal and about what the abdominal really is. This time we will talk about how to properly train the abdominal and things you shouldn´t be doing, like for example sit-ups.

Before talking about sit-ups, I first have to talk a little about the lower back, so that everyone understands what I will be saying later on in this blog.

As most people know, the back is made up of vertebrae and in between these vertebrae we have discs. A herniation occurs when a disc comes out posteriorly (it can also come out anteriorly but this is very rare). The bad thing of a herniation is when it ¨pinches¨ a nerve, this can lead to the terrible ¨sciatica pain¨. Well, recent studies have shown that a herniation is almost impossible without full flexion of the back, to be exact you need a compressive load and flexion (1). This is where it gets interesting: a compressive load doesn´t have to be produced by an external weight, like for example carrying a backpack, but compressive load is also produced by our own muscle!!

Every time a muscle contracts, it produces a compressive load somewhere in the body. That is normal but some exercises produce more than others and the traditional full sit-up imposes approximately 3300 N of compression load on the spine (2), you might think this is not a lot but the National Institute for Occupational Safety and Health (NIOSH) has set the action limit for low back compression at 3300 N (3); repetitive loading above this level is linked with higher injury rates in workers!! So if you take into account that when performing a sit-up you are in flexion, and then the compression force produced by the exercise, you realize just how bad sit-ups really are. A curl-up, for example, produces a compression force of 2009 N (2) but the good thing is that with a curl-up you don´t really flex your back. But even a curl-up really doesn´t work the abdominal the way it is supposed to. So how do you really train the abdominal? Let´s first explain what the abdominal really does.

The main purpose of the abdominal is not to flex the body, most of  us think that is the main purpose and that is why we have always done curl-ups and sit-ups and other flexion exercises, but it really isn´t. The main purpose of the abdominal is to transmit forces produced in our hips to our shoulder, or the other way around, and it does this by preventing as little movement as possible and maintaining a stiff torso. For example, if a sprinter didn´t have a stiff torso he would lose energy, that is why most sprinters run with very little motion in the spine (Michael Johnson, Usain Bolt) and have a great abdominal. There are of course exceptions, if your job or your physical activity requires a lot of flexion then maybe you should train with curl-ups and sit ups, but very few people have those kinds of activities. So to train the abdominal we should be ¨straight¨. For example, most people don´t know this but, when you are doing push-ups your abdominal is working and it only produces a compression force of 1838 N on the back (2).

With this information you should be able to think of some good abdominal exercises, but just in case I will name some. These exercises are not for everybody because some of them are quite hard, but even the hard ones can be made easy. You just have to remember that in all the exercises there should be spine stability, meaning there should not be any movement in the spine. Let us take an example of a hard exercise that can be made easy: the plank on the ground. This is quite hard but can be done on the wall standing up, which is much easier and for beginners. So let´s start listing a couple of good abdominal exercises. I will just mention four. These exercises are quite hard and are not for beginners.

  1. Planks: You are in a typical push-up position but instead of resting on your hands, you rest on your forearms. In that position, squeeze your ass as hard as possible, and at the same time try to bring your elbows back towards your legs. You are not actually moving your elbows, you are just producing a force without movement. You should really feel it in your abdominal.
  2. Side bridge: this one is hard to describe so I add a link so that you can take a look at it.
  3. Stir the pot: this is a very hard exercise. You are in a plank position but your forearms are on a fitball. From this position you make circles with your arms. The important thing here is that there should not be any movement in your spine. Everything comes from your arms and shoulders:
  4. Medicine ball tosses are an excellent progression to power and speed strength. Quick catch and throw sequences are a form of plyometric training to enhance the elastic energy storage and recovery system of the abdominal wall. The important thing with medicine ball tosses is that the hip and the shoulder move at the same time. This video explains 3 medicine ball tosses perfectly:

And to finish off, I will recommend this video where Dr. Stuart Mcgill explains different exercises and basically everything I have written about in this blog:  I highly recommend you guys watch this one, it´s only 5 minutes long!!


  1. Callaghan JP, Mcgill S. Intervertebral disc herniation: Stuides on a porcine model exposed to highly repetitive flexion/extension motion with compressive force. Clinical Biomechanics 2001, 16(1):28-37.
  2. Axler C, Mcgill S. Low back loads over a variety of abdominal exercises: Searching for the safest abdominal challenge. Med Sci.Sports.Ex 1997,29(6):804-11.
  3. The National Institude for Occupational Safety and Health 1981.

Tag Cloud