I have gone to the gym somewhat regularly throughout high school, and now  into college. Whenever the time comes for me do legs, there is always one machine I will avoid like the plague. This of course being the leg extension machine. The leg extension machine is a bigger mystery than bigfoot. The leg extension machine just sits in the corner collecting cobwebs, with no one ever using it. No one knows anything about it, either. Most people are worried that it may be unsafe, and if that is the case the possible muscle gains a person could stand to benefit from the machine would be totally not worth it. If this were true it would also bring into question why a gym would even have a leg extension in the first place.

There is obviously a right and wrong way to use every piece of equipment in the gym. This video is a very good example of how to ruin your knees, it doesn’t take any science to figure that out. In this post it is assumed that your using the machine correctly and not doing anything crazy that would put you knees in obvious jeopardy. I could use any piece of equipment in the gym incorrectly and injure myself but that does not mean it should be removed. For argument’s sake it will be assumed that all form is correct.

(image via afproducts.com)

To be clear, there are no decisive scientific studies pointing to the leg extension machine being harmful, or causing injuries. Instead we are left with differing opinions from sports doctors and knee specialists giving hypotheses on the subject. Due to the lack of experimental or observational studies, whether or whether not to use this machine has become a very ambiguous debate. What is known, is that the leg extension  does put a lot of stress on your anterior cruciate ligament. The fact remains to be seen however, if this stress can result in a knee injury further down the road. For example, in this interview with Brad Schofield, he says it is fine so long as you do not have a pre-existing knee condition. Then there is this article written by Eric Cressey stating that you should stay away from it. Research for this can become very frustrating very quickly, as for every one article stating one viewpoint, another article will pose the exact opposite one.

It is important to note that the leg extension is an open chain exercise, meaning it is done with your feet not planted and they are free to move. Studies do exist that show closed chain movements are more beneficial to recovering and rehabbing injuries to the knee. It is also important to note that this exercise entirely works the quadriceps, and the hamstrings are neglected entirely. When the quadricep is is overdeveloped in relation to the glutes and the hamstrings, it can leave a person susceptible to knee injury.

Winding up, there is a lack of information surrounding the leg extension machine safety with regard the knee. This lack of information certainly explains why no one uses the machine in the gym, and until there is some legitimate information, people will continue to avoid it. At this point in time, there is no reason for gyms to throw away these machines, but those who do use it should know that there is certainly more risk associated with it than a normal piece of equipment in the gym.