One Leg Squat Exercise and hamstrings 片足スクワットとハムストリングの関係


I wish to explain why and how we should practice one or single leg squat exercise. If you do not know the full extent of the exercise or not understand the functions of the different leg muscles, most likely you will not be able to achieve the full benefit from this excellent exercise.


I decided to write this short essay because one karate friend of mine who teaches Shotokan karate in the Bay Area (California) reached out to me yesterday. A few days ago, I had posted a video of the one leg squat exercise that we did at the ASAI seminar in India. In that post I described that this exercise was to strengthen the hamstrings. He kindly pointed out that this exercise is mainly used to strengthen the quadriceps (front of the thighs) rather than the hamstrings (back of the thighs).


He was correct about this point. However, I strongly believe that we should pay attention to the hamstrings when we do this exercise. I will explain in this essay why I say this.

There are two body movements that are involved in squatting both two legs and single leg versions. One move is, of course, to go down by bending the knee. The other is, naturally, to stand up by straightening the bent leg. Most of the people depend on the quadriceps (image left) to go down, thus they also try to use the same muscles to stand up. This is the problem I find. To bring your body down, the quadriceps must work to bring your body down in control as they will slow down the speed of body movement. I think of these muscles as a “brake”.




At the same time, this down movement will stretch the hamstrings. As you stand up or straighten your bent leg, you should switch your attention from the front of the thighs to the back or the hamstrings (image right). You should minimize using the quadriceps. Why? Because I consider the hamstrings an “accelerator”.


Let me explain further. Did you know that you use the hamstrings for walking and running? According to the article of Anatomy of the Hamstring Muscles by the verywell fit site (, the main function of the hamstrings is described as

You use the hamstrings for walking, running and jumping. They flex the knee and extend the the beginning of each step. In walking and running, they are antagonists to the quadriceps muscles in the action of deceleration of knee extension.


Isn’t it interesting to find that the hamstrings are antagonists to the quadriceps? It also says that the quadriceps are the muscles to decelerate of knee extension. This is why I consider the quadriceps as a brake. Yes, these muscles are there to slow you down. On the other hand, the hamstrings function as the accelerator or enable you to walk, run and jump.


Among professional athletes such as Olympic runners, basketball players, and tennis players, they know all about the importance of hamstrings. In other words, to be able to move quickly you must have strong hamstrings. Unfortunately, the knowledge of kinesiology is not shared among karate practitioners. They still engage in the exercises that are not beneficial or are even damaging to our karate techniques. One of them is putting the rubber tube around your waist and do oizuki against the pulling of the rubber tube. I will not go into the explanation why this exercise is not good for karate in this essay. I wish to focus on one legged squat for now.


To develop the ability to move the body faster, you need to strengthen the hamstrings. This is exactly why I say not to pay attention to the front of the thighs or the quadriceps as you do the one leg squat exercise. In fact, if you develop only the quadriceps, you are simply increasing your braking power or slowing your motion ability. On the other hand, if you would strengthen the hamstrings you are increasing strength to the muscles that can make you move or shift faster or quicker. Isn’t this what you want?


You can read the full article about the hamstrings at the following link:


One thing I must add is that squat exercise including one leg version is not the best exercise to strengthen the hamstrings. In fact, the dead lift and the leg curls are more effective exercises, especially if you are thinking of developing bigger hamstrings. Those two exercises, however, require either weights or some sort of equipment. For karate, we prefer to find a way to exercise without these tools.



When I introduce this exercise at the ASAI seminars, I ask the participants to pay particular attention to the hamstrings (back side of the thighs) as they stand up. By doing this, they will not forget to work on the hamstrings that are very critical and necessary for the quick body moving and shifting.


This essay was proof read by Sensei L. O’Neill of NY on Feb 12.

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