Ask AFAA: not so hip

Question:

As part of my resistance training workout, I work my inner and outer thigh muscles. My gym has a cable machine with a fleece-lined leather strap that fits around the ankle in order to perform the outward and inward "side kick" movement. Since I have seen this done for many years, I assume it is OK. However, when I do this exercise it hurts the sides of my knees. Is it me or is this exercise unsafe?

Kim Smyser

Chicago, Illinois

Answer:

Ever since the birth of "aerobic exercise," the fitness community has worked hard to identify harmful, and possibly, dangerous exercise positions and movements. The Aerobics and Fitness Association of America (AFAA), American Council on Exercise (ACE) and other certifying agencies have successfully discouraged many unsafe exercises. The criterion is relatively simple--if a position or movement is contrary, to safe and normal biomechanical patterning, it is generally disallowed. For instance, the "plough" position is unacceptable because of potential hyper-flexion of the cervical vertebrae. Likewise, orbital rotation of the head has also been outlawed for similar reasons. Although these movements are practiced within yoga and dance, they are virtually non-existent in the group exercise arena.

The exercise that concerns you appears to have escaped the scrutiny of many fitness professionals. Its appropriate biomechanical description is leg abduction (i.e., moving the leg away from the midline of the body in the frontal plane) and adduction (i.e., bringing the leg back to the midline of the body, in the frontal plane). Although the movement itself is not problematic, the technique used to achieve it is highly questionable. Placing the strap around the ankle to perform the adduction is considered valgus loading of the knee. Varus loading of the knee occurs when performing the abduction. According to Gardiner, et al., (2001), the medial collateral ligament (MCL), the one primarily affected during valgus loading, is one of the most frequently injured knee ligaments. Likewise, the combination of valgus/varus loading and internal/external rotation, which all occur during the cable adduction/abduction activity, can damage both the collateral ligaments as well as the anterior cruciate ligament (ACL) (Besier, et al., 2001).

The problem is simply where the force is applied. Placing the strap on the ankle clearly jeopardizes the knee joint. It is no wonder your knees hurt after doing this exercise. If the force were applied above the knee, the problem would be solved. For example, the multi-hip machine is a great alternative because it safely allows leg adduction/abduction as well as hip flexion and extension to be performed with the direction of force placed appropriately above the knee.

Sometimes rules are created after an increasing number of injuries are reported. Remember when "high-impact" aerobics took the country by storm in the late 1970s and early 1980s? People were achieving a cardiovascular training effect by performing many variations of dance combined with running in place. After awhile, problems appeared primarily because instructors were unaware of "overuse" injuries. The high volume of foot strikes took its toll and injuries, ranging from plantar fasciitis and bone bruising to shin splints and patellar tendonitis, occurred. As a result, "low-impact" aerobics, in which one foot stays in contact with the floor at all times, evolved. This certainly helped but substantially reduced workout intensity. The introduction of the "step" helped increase intensity and minimized overuse problems by reducing the volume of repetitions. However, as movements with "step" aerobics became more complex, it was discovered that pivoting on the ball of the foot on top of the step could be placing a dangerous level of valgus/varus torque on the knee. Therefore, the fitness community no longer accepts that movement.

Why dangerous stress to a body part in one form of exercise is identified as high risk of injury while another is tolerated is certainly baffling. The multi-hip machine is a sensible alternative to the leg adduction/abduction cable pull, but where is the protest to this exercise? It is up to fitness professionals to pay attention to this issue--we can't expect health club management to be so prudent.

References

Gardiner, J.C., Weiss, J.A. and Rosenberg, J.D. "Strain in the human medial collateral ligament during valgus loading of the knee." Clinical Orthopaedics, 2001 Oct.; (391): 266-74.

Besier, T.F., et al. "External loading of the knee joint during running and cutting maneuvers." Medicine Science in Sports and Exercise, 2001 July; 33 (7): 1168-75.

Gregory L. Welch, M.S., is an exercise physiologist and president of SpeciFit, An Agency of Wellness and Competitive Performance Enhancement, located in Seal Beach, California. He is also the wellness director for the Wellness Institute at the Downey Family YMCA. Welch is an accomplished writer and lecturer dedicated to raising the level of academia within the fitness industry. He can be reached at (562) 862-4201.

COPYRIGHT 2003 Aerobics and Fitness Association of America
COPYRIGHT 2008 Gale, Cengage Learning