Knee Extension Torque During Repeated Knee Extension-Flexion Reversals and Separated Knee Extension-Flexion Dyads RICHARD W. BOHANNON I measured the knee extension torque, produced by eight hemiparetic patients during repeated knee extension-flexion reversals and during separated knee extension-flexion dyads, to determine the effect of "reversal of antagonists" on knee extension torque. The hemiparesis in these eight patients was secondary to intracranial lesions. I tested their involved lower extremity on an isokinetic dynamometer at 60°/sec. Using a sequential medical-trials design, I found knee extension torque to be significantly greater during repeated knee extension- flexion reversals than during separated knee extension-flexion dyads (p < .05). I, therefore, concluded that reversal of antagonists may facilitate knee extension torque production in the type of patients tested, under the specific conditions of their testing. Key Words:zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Hemiplegia, Knee, Muscles, Physical therapy. Among the facilitation techniques es- poused by Knott and Voss is that of "reversal of antagonists." 1 According to these experts in therapeutic exercise, the stimulation effect of the technique that incorporates the resisted contraction of an antagonist before contraction of an agonist "is readily demonstrated in the normal subject." Although their state- ment has a neurophysiological basis, 2 " 4 the statement has not, as far as I am aware, been experimentally verified. Contrary to the claim by Knott and Voss, my associates and I did not find knee extension torque enhanced in healthy subjects by the contraction of the knee flexor muscles before the con- traction of the quadriceps femoris mus- cles. 5 Gibson and I did, however, find that a quadriceps femoris muscle stretch may have a limited early facilitatory effect on subsequent knee extension torque production in healthy subjects. 6 We suggested, therefore, that muscle stretch may be partly responsible for the apparent effects of reversal of antago- nists. Although these two studies com- prise a preliminary investigation into the claimed effects of reversal of antag- onists, the studies are both limited be- cause my associates and I tested healthy subjects. 5,6 If clinicians are to base their practice on objective research findings, rather than on less sound foundations, 7 the validity of techniques such as reversal of antagonists must be confirmed on pa- tients. The purpose of this investigation was to test the effect of reversal of an- tagonists on paretic quadriceps femoris muscles by comparing the knee exten- sion torque produced during repeated knee extension-flexion reversals with that produced during separated knee ex- tension-flexion dyads. Because knee ex- tension is preceded immediately by knee flexion during repeated reversals but not during separated dyads, this model seemed appropriate for our purpose. Given our findings with healthy sub- jects, 5 I did not expect to find that re- versal of antagonists affected knee ex- tension torque production. METHOD My institution's ethics committee ap- proved the protocol for this investiga- tion. A sequential medical-trials design was selected to compare between the knee extension torque produced during repeated knee extension-flexion re- versals and the torque produced during separated knee extension-flexion dyads. I selected this design because it allows the confirmation of treatment effect with a minimum number of subjects. 8,9 Subjects who met the admission cri- teria for the study were admitted as they became available. The admission crite- ria required that subjects were affected by an intracranial lesion (cerebrovascu- lar accident, tumor, or closed head in- jury), able to generate measurable static kneeflexiontorque in sitting, capable of completing knee extension through the full range against gravity, competent to follow instructions, and willing to grant informed consent. Two subjects had closed head injuries and six patients had cerebrovascular accidents (N = eight, four men and four women). Four were hemiparetic on the right and four were hemiparetic on the left. Subjects ranged in age from 21 to 79 years and were two months to two years postonset of the intracranial lesion. Procedure The knee extension torque generated during repeated knee extension-flexion reversals and separated extension-flex- ion dyads was measured on a Cybex® II isokinetic dynamometer.* Repeated knee extension-flexion reversals con- sisted of uninterrupted maximum vol- untary knee extension-flexion reversals. These reversals, which were begun with the knee in full extension, represented the reversal of antagonist condition. Knee extension-flexion dyads consisted * Cybex, Division of Lumex, Inc, 2100 Smith- town Ave, Ronkonkoma, NY 11779. Mr. Bohannon is Chief, Department of Physical Therapy, Southeastern Regional Rehabilitation Center, Cape Fear Valley Medical Center, Fayette- ville, NC 28302 (USA). This study was supported, in part, by a grant from the Maggie Knott Memorial Fund. This article was submitted June 29, 1984; was with the author for revision eight weeks; and was accepted December 12, 1984. 1052 PHYSICAL THERAPY