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Effects of a functional knee brace for ACL insufficiency during treadmill running
L Q Wilson1, J Y Weltman, D E Martin
1General Clinical Research Center, Health Sciences Center University of Virginia, Charlottesville 22908, USA.
Purpose:
To assess the effects of a functional knee brace (FKB) for anterior cruciate ligament insufficiency (ACLI) on physiological and perceptual parameters during treadmill running.
Methods:
Thirteen ACLI subjects (time since injury, 5.8 +/- 5.3 yr), performed an incremental test to exhaustion and two constant load 20-min tests, one at an intensity below lactate threshold (bLT), and the other at an intensity above LT (aLT) each with and without their FKB.
Results:
Bracing had no effect on peak variables except for higher ratings of perceived exertion at the legs (RPE-L) at the velocities associated with a blood lactate concentration [HLa] of 4.0 mM and at peak. Bracing had no effect when exercising at bLT but did significantly alter the metabolic profile developed during the performance of the aLT tests (83 +/- 0.03% VO2peak). In particular, FKB resulted in elevated blood [HLa] (23%), VO2 (4%), VE (12%), VCO2 [corrected] (7%), and VE/VO2 (7%). HR and slow component VO2 did not differ between the brace and no brace aLT tests. RPE-L and RPE-knee were significantly elevated during aLT when the brace was worn. Suspected mechanisms include alterations in muscle recruitment patterns and/or occlusion.
Conclusions:
When ACLI individuals wear a FKB during high intensity straight-ahead running exercise of long duration, physiological parameters are affected.