Body and Breath

Each month a new series of 10 questions will be posted on the Test Yourself page. The following month the questions will then be posted here along with the answers and explanations.

Answers to the June 2002 questions are posted below. ( View Archive )

Test yourself, June, 2002, with answers, posted July, 2002

You are teaching practical aspects of anatomy to a group of experienced hatha yoga teachers. The assignment: Using the postures discussed in chapter one through five of Anatomy of Hatha Yoga as a frame of reference, find examples (where applicable) of both stretching and exercise for the hip flexors (the psoas and iliacus muscles). Distinguish between active stretch and passive stretch in the instances of stretching, and distinguish between isotonic and isometric situations in the instances of exercise. Also distinguish between the psoas muscles and the iliacus muscles where applicable, and make comments on their effects on sacroiliac nutation and counternutation.

121. Figure 1.2. Right side hip flexors shorten concentrically to help gravity pull the right thigh parallel to the floor (isotonic movement), while the left hip flexors eccentrically resist hyperextension (active stretch). There are no marked differences between the action of the psoas vis-à-vis the iliacus on either side.

Figure 1.15. Psoas and iliacus are both moderately stretched (equally on each side) as they lengthen eccentrically and resist gravity.

Figure 1.16. Psoas and iliacus shorten concentrically, aiding gravity in pulling the lumbar spine (psoas muscles) down and forward, as well as aiding the flexion of the hip bones (iliacus muscles) forward toward the femurs.

122. Figure 2.10. Similar to figure 1.15, but less intense.

Figures 2.19, 2.20, and 2.25. Psoas and iliacus help maintain the 90 degree angle between the thighs and the spine. The iliacus muscles pull the pelvis forward, flexing the hip bones selectively, thus favoring counternutation, and the psoas muscles pull the lumbar spine forward, thus favoring nutation.

123. Figure 3.1. Iliacus and psoas act symmetrically as synergists to brace the pelvis while the abdominal muscles act as prime movers to lift the spine up and forward. More detailed: the iliacus muscles act purely to brace the pelvic bones in a moderately flexed position while the psoas muscles are more active in actually lifting the lumbar spine (and thus the entire upper body) up and away from the floor.

Figure 3.15. The right psoas and iliacus are relatively inactive, and the left iliacus and psoas actively (and concentrically) flex the left hip. Both are equally active under ordinary circumstances, but if you purposely let the lower back lift away from the floor and then focus your attention on muscular activity that assists that lift even more while pulling the thigh perfectly perpendicular, you will be selectively and powerfully engaging the left psoas, and thereby encouraging nutation of the left sacroiliac joint.

Figure 3.16. In this symmetrical pose, both the iliacus and psoas muscles are active, but the iliacus muscles carry the brunt of flexing the hip bones (thus encouraging counternutation) while the psoas muscles brace the posture moderately. If the latter muscles took center stage as agonists (prime movers), they would pull the lumbar region forward in addition to flexing the thigh, which is not wanted here.

Figure 3.17. The supine double leglift is similar to 3.16, except it is even more important to restrain the psoas muscles from lifting the lumbar region forward, or at least to counteract that tendency by powerfully activating the abdominal muscles.

Figure 3.19b. Here the psoas muscles act as agonists (prime movers) to flex the femurs from a stabilized lumbar arch, also encouraging nutation, while the iliacus muscles act as synergists to aid flexion.

Figure 3.20a. Here the psoas muscles are prime movers and the iliacus muscles are synergists for lifting the lumbar region forward. Once stabilized the muscles act strongly but isometrically. The psoas muscles frankly accentuate the lumbar lordosis and the iliacus muscles aid the motion by pulling up and forward on the ilia. The actions of the psoas muscles favor nutation, and the actions of the iliacus muscles favor counternutation.

Figure 3.20b. Continuing, the psoas muscles act as agonists to lift the thighs, flexing the hips a few degrees and favoring sacroiliac nutation, while the iliacus muscles synergistically brace the posture. The iliacus muscles have to support the movement and yet be restrained, else they would pull the ilia forward relative to the sacrum (counternutation) and overwhelm the action of the psoas in keeping the lumbar region forward and sharply accentuated. The key to the posture is of course a relaxed abdomen.

Figure 3.21b. While the abdominal muscles are initiating the movement into the sit-up, the iliacus and psoas muscles brace the posture. Then, as soon as the abdominal muscles have gone as far as they can go, the psoas and even more the iliacus muscles pull forward on the spine (psoas) and pelvic bones (iliacus muscles) to complete the posture.

Figure 3.22a. Iliacus muscles are agonists, psoas muscles are synergists. Sacroiliac counternutation is favored.

Figure 3.22b. Psoas muscles are agonists, iliacus muscles are synergists. Sacroiliac nutation is favored.

Figure 3.23d. In the completed peacock, the psoas and iliacus muscles are in a state of active stretch, acting as antagonists to the extensor muscles on the posterior aspect of the body.

124. Figures 4.19 and 4.20. The psoas and iliacus resist both backbends as antagonists to the muscles on the back side of the body, but in the whole-body backbend, anterior muscles from top to bottom aid their resistance synergistically, whereas in the relaxed standing backbend, the psoas and iliacus muscles act more in isolation.

Figure 4.23. Psoas and iliacus muscles aid this intermediate forward bend by tugging on both the pelvic bones (iliacus muscles) and the lumbar spine (psoas muscles).

Figure 4.24. In this advanced forward bend, the psoas muscles are relatively inactive, except for mildly bracing the posture, but the iliacus muscles pull strongly from their working origins on the thighs to their working insertions on the ilia.

Figure 4.25. The right psoas and iliacus are both active in pulling the torso forward from the hips. The left iliopsoas combination is relatively inactive.

Figure 4.26. The right psoas eases up in its activity while the right iliacus pulls even more strongly on the ilia, particularly when the practitioner is making a strong effort and not just depending on gravity. The left hip flexors are again inactive.

Figure 4.35. The right psoas and iliacus are both active in pulling the torso forward whereas the left psoas and iliacus are inactive.

Figure 4.36. The completed revolving triangle is unusual in that the right hip flexors end up in an actively stretched position and the left hip flexors end up in a more passively stretched position.

125. Figure 5.1. The psoas and iliacus assist gravity in completing 120 degrees of hip flexion. The psoas muscles pull on the lumbar lordosis and encourage nutation, and the iliacus muscles pull on the pelvic bones and encourage counternutation.

Figure 5.2. In this moderate backbend, the psoas and iliacus muscles resist stretching eccentrically.

Figure 5.3. The psoas muscles are responsible for the continued emphasis on the lumbar lordosis and nutation, whereas the iliacus muscles are relatively inactive.

Figure 5.4. Now the psoas muscles are relatively inactive, and the iliacus muscles are assisting gravity in flexing the hip bones relative to the femurs.

Figure 5.6. The psoas and iliacus muscles here act synergistically with the respiratory diaphragm in restricting backbending where it is manifested at the hip joints.

Figure 5.7. The iliacus muscles remain relaxed, and the psoas muscles tug sharply against the lumbar lordosis, thus emphasizing nutation and acting synergistically with the respiratory diaphragm to sharpen the backbend from the pelvis up.

Figure 5.9. The psoas and iliacus muscles are moderately and passively stretched in the classic cobra.

Figure 5.11. The supported cobra facing the ceiling stretches the hip flexors more convincingly than the classic cobra.

Figure 5.12. The hip flexors along with the abdominal muscles resist completion of this advanced cobra.

Figure 5.13 and 5.14. The hip flexors resist hyperextension at the hips by remain in a state of active tension in the upward-facing dog postures.

Figure 5.15. The left hip flexors strongly resist extension of the left thigh.

Figure 5.16. The left hip flexors here passively resist extension of the left thigh. If they are tight, this supported half locust is a real stretch.

Figures 5.17 and 5.18. Hip hyperextension in both these postures is strongly resisted by the hip flexors.

Figure 5.19. If you can come into this pose easily, the hip flexors will end up passively stretched.

Figures 5.20 and 5.21. As in figure 1.15, the psoas and iliacus are both moderately stretched (equally on each side) as they lengthen eccentrically and resist gravity.

Figures 5.22 and 5.23. The hip flexors strongly resist hip flexion in the beginner's bow, and yield, albeit actively, in the advanced bow.

Figure 5.29. The hip flexors are the first line of protection against hip hyperextension in the wheel. They have to relax and yet they resist excess extension. They are especially resistant when someone without quite enough flexibility tries to drop down in the wheel from a standing position.

Figure 5.30. With the playground ball under the pelvis, the hip flexors are stretched passively in anyone who has good flexibility. Otherwise, they resist strongly. If one has mobile sacroiliac joints, the pose encourages nutation and stretches the psoas muscles selectively.

Figures 5.31 and 5.32. The hip flexors are moderately relaxed in the first figure, and completely relaxed in the second.

Figures 5.34 and 5.35. The hip flexors resist the camel strongly in anyone who is marginally flexible. If they cannot yield and permit enough hip hyperextension to complete the poses, they quickly pull the hips to the rear, causing the practitioner to drop back and sit on his or her heels. Nutation and stretch of the psoas muscles are emphasized in anyone who does the advanced camel easily, and counternutation and stretch of the iliacus muscles are emphasized in anyone who is less flexible.