Medicine & Science in Sports and Exercise
Stretching at the ankle joint: viscoelastic responses to holds and continuous passive motion
To the sports enthusiast, a sprained ankle means waiting 4 to 6 weeks before returning to full activity. To the emergency physician, it means a potential radiograph, RICE (rest, ice, compression, elevation), and discharge. Neither patients nor physicians are usually very alarmed by ankle sprains, yet there can be significant long-term morbidity from severe sprains. Moreover, millions of health care dollars are spent each year in treating this common injury. Better methods of prevention and shorter rehabilitation times could have a great impact, and proper stretching might be the key. The authors of this study have objectively analyzed how the ankle responds to different types of stretching.
Twenty-four men and women (mean age 26 years) who were currently involved in recreational and/or competitive sports for at least 1 to 2 hours, 3 to 4 times per week participated in the study. All subjects were reported to be healthy, and none were engaged in “formal” stretching programs. Four groups were formed in order to test 4 types of stretching programs. The 4 programs were a continuous hold for 60 seconds, 2 sequential holds for 30 seconds each, 4 sequential holds for 15 seconds each, and continuous passive motion for 60 seconds. Specially designed equipment moved the subjects’ ankles through 1 of the 4 programs. A “hold” was defined as dorsiflexion at 80% of each person's maximum range of motion. Each person had 60 seconds of stretching per day for 1 week in each of the 4 groups.
Sensors within the equipment measured stiffness and force relaxation. “Stiffness” was defined as resistance to movement, while “force relaxation” referred to the tension of the muscles of dorsiflexion at any given position. According to the results, only continuous passive motion significantly reduced stiffness (P < .05), as measured over the first 10% and last 10% of motion. Muscle tension was found to be most reduced by holds. Continuous motion reduced tension by an average of 10.5%, whereas holds decreased tension by 19% to 21.7%, with the greatest decreases in the first 20 seconds of a hold or series of holds.
The authors of this study propose that these results have ramifications for both injury prevention and rehabilitation. They conclude that one should perform holds to decrease peak forces, and that one should perform continuous motion to decrease stiffness. As with all bench research, however, there are several caveats in applying study results to real life. First, the internal validity of the study itself must be solid. In this study, it must be noted that stiffness was reported only at the 30-second point of each program, and not at all during the 60-second hold. Consequently, one must ask if significant differences in stiffness might have been seen after all four 15-second holds, after both 30-second holds, or at the end of the 60-second hold. Secondly, laboratory conditions must simulate real life. This study assessed how the ankles and legs of healthy athletes respond to stretching. It cannot be inferred that this applies to people in all degrees of physical condition. Nor can one postulate that the viscoelastic properties of injured ankles are the same as those in this study, thus giving this study little applicability for rehabilitation. It seems that the most valuable finding that this study provides is that both holds and continuous motion change the biomechanics of the ankle in healthy athletes. The ramifications of these findings have yet to be determined.
(Med Sci Sports Exerc. 2001;33:354–357) P. J. McNair, E. W. Dombroski, D. J. Hewson, and S. N. Stanley.
© 2001 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.