Body and Breath - Yoga Shop Talk

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Yoga shoptalk, April, 2002

I am puzzled by your analysis of the arch posture. Starting in a semi-supine position, the knees are fully flexed. Rising into the arch, the degree of flexion diminishes to about 90-100 degrees. Relatively speaking, therefore, moving into the posture partially extends the knees. The agonist knee extensors are the quadriceps femori, and they are working hard as I lift up. Gravity and the fixed foot position prevent further extension of the knee. You say in your text that the hamstrings are working : how can this be, as their activity would increase knee flexion? Also, my hamstrings seem quite relaxed as I move into the posture, and in Figure 9.21, the hamstrings appear quite slack. (The situation may be different in the bridge.) I don't want to mislead my students. Please comment.

That's a good comment and thoughtful question, and a little more explanation in the text would have been helpful. For clarification, try the following experiment. Lie down supine with the knees bent fully and feet fairly close to the buttocks. Then reach around the lateral aspects of your thighs with your hands and place your fingertips firmly against the posteromedial aspects of the hamstrings. Notice that they are quite soft. Next, slowly start to lift up in the arch. You will immediately notice that these muscles firm up, and that the more you lift the tighter they become. It's true that the hamstring muscles tend to flex the knees, but with the feet held in position against the floor, and with the quadriceps femoris in a strong state of contraction (extending the knees, as you pointed out), the hamstrings can do no more in regard to knee flexion than act as antagonists to the quadriceps femoris muscles (in limiting knee extension). But there's something else that you have overlooked, and that is that the hamstring muscles also act as hip extensors (which is actually the action that defines them as hamstrings), and this activity is what you feel with your fingertips as you try to lift up, first extending and then hyperextending the hips. And as for the bridge pose, it is entirely different, but opposite from your first thought. Supporting the back with the hands in the bridge makes the hamstrings redundant as far as supporting hip extension is concerned, so in the latter posture they can remain relaxed.