Persistent Muscle Inhibition after Anterior Cruciate Ligament Reconstruction: Role of Reflex Excitability. Issue 12 (December 2016)

• Record Type: Journal Article
• Authors: HARKEY, MATTHEW S.; LUC-HARKEY, BRITTNEY A.; LEPLEY, ADAM S.; GRINDSTAFF, TERRY L.; GRIBBLE, PHILLIP; BLACKBURN, J. TROY; SPANG, JEFFREY T.; PIETROSIMONE, BRIAN
• Is Part Of: Medicine and science in sports and exercise. Volume 48:Issue 12(2016)
• Publication Date: 2016-12
• Subjects: QUADRICEPS -- VOLUNTARY ACTIVATION -- CENTRAL ACTIVATION RATIO -- SPINAL REFLEX -- HOFFMANN REFLEX; Sports medicine -- Periodicals; Exercise -- Physiological aspects -- Periodicals; Exercise -- Health aspects -- Periodicals; 612.044
• DOI: 10.1249/MSS.0000000000001046
• Languages: English
• ISSNs: 0195-9131

Abstract

ABSTRACT: Purpose: Persistent voluntary quadriceps activation deficits are common after anterior cruciate ligament reconstruction (ACLR), but the direct causes are unclear. The primary purpose of this study was to determine whether spinal reflex excitability deficits are present in individuals with a history of ACLR, and secondarily to determine whether spinal reflex excitability predicts which individuals possess full voluntary quadriceps activation. Methods: One hundred and forty-seven individuals (74 healthy and 73 ACLR) participated in this cross-sectional case–control study. Quadriceps spinal reflex excitability was quantified using the Hoffmann reflex normalized to the maximal muscle response (H:M ratio). Voluntary quadriceps activation was evaluated with the burst superimposition technique and calculated via the central activation ratio (CAR). Separate 2 × 2 ANCOVA tests were used to compare between-limb and between-group differences for H:M ratio and CAR. A receiver operating characteristic curve was used to determine the accuracy of H:M ratio to predict if ACLR participants present with full voluntary activation (CAR ≥ 0.95). Results: The ACLR H:M ratio was not different between limbs or compared with the healthy group ( P > 0.05). Although ACLR CAR was lower bilaterally compared with the healthy group ( P < 0.001), it did not differ between limbs. The H:M ratio has poor accuracy for predicting which individuals exhibit full voluntary activation (receiver operating characteristic area under the curve = 0.52, 95% CI = 0.37, 0.66; odds ratio = 2.2, 95% CI = 0.8, 5.9). Conclusions: Spinal reflex excitability did not differ between limbs in individuals with ACLR or compared with healthy participants. The level of quadriceps spinal reflex excitability has poor accuracy at predicting which ACLR individuals would demonstrate full voluntary quadriceps activation.