Induced Anterior Knee Pain Immediately Reduces Involuntary and Voluntary Quadriceps Activation
ABSTRACT OBJECTIVE:: To examine the immediate effects of experimentally induced anterior knee pain (AKP) on involuntary and voluntary quadriceps strength and activation. DESIGN:: Crossover 3 × 3 randomized controlled laboratory study with repeated measures. SETTING:: Human Performance Research Center, Brigham Young University. PARTICIPANTS:: Thirteen neurologically sound volunteers (age, 21.9 ± 3.2 years). INTERVENTIONS:: Subjects underwent 3 different conditions (pain, sham, and control). To induce AKP and sham condition, 5% sodium chloride and 0.9% sodium chloride (total volume of 1.0 mL for each condition), respectively, were injected into the infrapatellar fat pad on the dominant leg. No injection was performed for the control condition. MAIN OUTCOME MEASURES:: The vastus medialis peak Hoffmann reflex normalized by the peak motor response (H:M ratio) was used to measure involuntary quadriceps activation. Quadriceps central activation ratio (CAR) using maximal isometric knee extension torque (N·m) was calculated to assess voluntary quadriceps activation. The visual analog scale was used to measure pain perception. RESULTS:: Our pain model increased perceived pain immediately after the 5% hypertonic saline injection and pain lasted for 12 minutes on average (F40,743 = 16.85, P < 0.001). During the pain condition, subjects showed a 12% decrease in H:M ratio (F2,59 = 8.64, P < 0.001), a 34% decrease in maximal isometric knee extension torque (F2,59 = 5.89, P < 0.01), and a 5% decrease in CAR (F2,59 = 3.83, P = 0.03). CONCLUSIONS:: Our data showed that joint pain may be an independent factor to alter function of the muscles surrounding the painful joint. Both involuntary and voluntary inhibitory pathways may play a role in an immediate reduction of muscle activation.
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ABSTRACT: Patellar taping is frequently used to treat patellofemoral pain (PFP). This systematic review and meta-analysis (1) evaluates the efficacy of patellar taping for patients with PFP, (2) compares the efficacy of various taping techniques and (3) identifies potential biomechanical mechanisms of action. The MEDLINE, CINAHL, SPORTSDiscus, Web of Science and Google Scholar databases were searched in January 2013 for studies evaluating the effects of patellar taping on pain and lower-limb biomechanics in individuals with PFP. Three independent reviewers assessed each paper for inclusion and two assessed for quality. Means and SDs were extracted from each included study to allow effect size calculations. Twenty studies were identified. There is moderate evidence that (1) tailored (customised to the patient to control lateral tilt, glide and spin) and untailored patellar taping provides immediate pain reduction of large and small effect, respectively and (2) tailored patellar taping promotes earlier onset of vastus medialis oblique (VMO) contraction (relative to vastus lateralis contraction). There is limited evidence that (1) tailored patellar taping combined with exercise provides superior pain reduction compared to exercise alone at 4 weeks, (2) untailored patellar taping added to exercise at 3-12 months has no benefit and (3) tailored patellar taping promotes increased internal knee extension moments. Tailoring patellar taping application (ie, to control lateral tilt, glide and spin) to optimise pain reduction is important for efficacy. Evaluation of tailored patellar taping beyond the immediate term is limited and should be a research priority. Possible mechanisms behind patellar taping efficacy include earlier VMO onset and improved knee function capacity (ie, ability to tolerate greater internal knee extension moments).British Journal of Sports Medicine 12/2013; 48(6). DOI:10.1136/bjsports-2013-092437 · 5.03 Impact Factor
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ABSTRACT: Comparative control trial OBJECTIVE: To compare the efficacy of posterolateral hip muscle strengthening versus quadriceps strengthening in reducing pain and improving health status in persons with patellofemoral pain (PFP). Comparative control trial. Private rehabilitation facility PARTICIPANTS: Thirty-six persons with a diagnosis of PFP (18 males and 18 females). Male and female patients were alternately assigned to a posterolateral hip muscle strengthening group (9 males and 9 females) or a quadriceps strengthening group (9 males and 9 females). The posterolateral hip muscle strengthening group performed hip abductor and external rotator strengthening exercises while the quadriceps strengthening group performed quadriceps strengthening exercises (3 times a week for 8 weeks). Pain (VAS) and health status (WOMAC) were assessed at baseline, post-intervention, and at a 6 month follow-up. Significant improvements in VAS and WOMAC scores were observed in both groups from baseline to post-intervention and from baseline to 6 month follow-up (p<.001). Improvements in VAS and WOMAC scores in the posterolateral hip exercise group were superior to those in the quadriceps exercise group post-intervention and at the 6 month follow up (p<.05). Although both intervention programs resulted in decreased pain and improved function in persons with PFP, outcomes in the posterolateral hip exercise group were superior to the quadriceps exercise group. The superior outcomes obtained in the posterolateral hip exercise group were maintained 6 months post-intervention.Archives of physical medicine and rehabilitation 01/2014; 95(5). DOI:10.1016/j.apmr.2013.12.022 · 2.57 Impact Factor
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ABSTRACT: The superimposed burst technique is used to estimate quadriceps central activation ratio during a maximal voluntary isometric contraction, which is calculated from force data during an open-chain knee extension task. Assessing quadriceps activation in a closed-chain position would more closely simulate the action of the quadriceps during activity. Our aim was to determine the test-retest reliability of the quadriceps central activation ratio in the closed chain. Twenty-two healthy, active volunteers (13M/12F; age=23.8±3; height=72.7±14.5cm; mass=175.3±9.6kg) were recruited to participate. Knee extension MVIC torque and the peak torque during a superimposed electrical stimulus delivered to the quadriceps during an MVIC were measured to estimate quadriceps CAR. Interclass correlation coefficients were used to assess test-retest reliability between sessions, and Bland-Altman plots to graphically assess agreement between sessions. Test-retest reliability was fair for CAR (ICC2,k=0.68; P=0.005), with a mean difference of -2.8±10.3%, and limits of agreement ranging -23.1-18.1%. CAR calculated using the superimposed burst technique is moderately reliable in a closed-chain position using technique-based instruction. Although acceptable reliability was demonstrated, wide limits of agreement suggest high variability between sessions.Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 04/2014; 24(3). DOI:10.1016/j.jelekin.2014.03.008 · 1.65 Impact Factor