Quadriceps Muscle Function After Exercise in Men and Women With a History of Anterior Cruciate Ligament Reconstruction

Abstract

Context: Sex differences in lower extremity neuromuscular function have been reported after anterior cruciate ligament reconstruction (ACLR). Research evidence supports different levels of fatigability in men and women and between patients with ACLR and healthy controls. The influence of sex on the response to continuous exercise in patients with ACLR is not clear.Objective: To compare quadriceps neuromuscular function after exercise between men and women with ACLR.Design: Descriptive laboratory study. Setting: Laboratory.Patients or Other Participants: Twenty-six active volunteers (13 men [50%]: age ¼ 24.1 6 4.4 years, height ¼ 179.1 6 9.8 cm, mass ¼ 80.1 6 9.4 kg, months since surgery ¼ 43.5 6 37.0; 13 women [50%]: age ¼ 24.2 6 5.6 years, height ¼ 163.0 6 5.9 cm, mass ¼ 62.3 6 8.3 kg, months since surgery ¼ 45.8 6 42.7) with a history of unilateral primary ACLR at least 6 months earlier. Intervention(s):Thirty minutes of continuous exercise comprising 5 separate 6-minute cycles, including 5 minutes of uphill walking and 1 minute of body-weight squatting and stepups.Main Outcome Measure(s): Normalized knee-extension maximal voluntary isometric contraction torque, quadriceps superimposed-burst torque, and quadriceps central activation ratio before and after exercise. We performed separate 2 (sex: men, women) 3 2 (time: preexercise, postexercise) repeatedmeasures analyses of variance for the 3 variables. Separate, independent-samples t tests were calculated to compare preexercise with postexercise change in all dependent variables between sexes.Results: A significant group-by-time interaction was present for knee-extension torque (P ¼ .04). The percentage reduction in knee-extension maximal voluntary isometric contraction torque (men ¼ 1.94%, women ¼ À10.32%; P ¼ .02) and quadriceps central activation ratio (men ¼ À1.45%, women ¼ À8.69%; P ¼ .03) experienced by men was less than that observed in women.Conclusions: In the presence of quadriceps dysfunction, female participants experienced greater-magnitude reductions in quadriceps function after 30 minutes of exercise than male participants. This indicates a reduced ability to absorb knee-joint loads, which may have significant implications for reinjury and joint osteoarthritis in women after ACLR.Key Words: knee injury, fatigue, quadriceps activation Key PointsAfter anterior cruciate ligament reconstruction, quadriceps muscle dysfunction may reduce the ability to dynamically absorb knee-joint loading during activity. Compared with women, the quadriceps muscle in men is less susceptible to fatigue after anterior cruciate ligament reconstruction; however, sex differences have not been investigated. In the presence of preexercise quadriceps muscle dysfunction, women experienced greater reductions in normalized knee-extension maximal voluntary isometric torque and quadriceps central activation ratio after 30 minutes of exercise than men. The greater magnitude of exercise-induced alterations observed in women compared with men may put them at increased risk for reinju...

Quadriceps Strength and Volitional Activation After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis

“… 24 However, recuperation from ACLR requires extensive rehabilitation and results in significant time loss from activity. 24 Quadriceps function is consistently identified as an important aspect of recovery for individuals after ACLR because of its primary role in knee stability and association with many short-term, 15 , 28 , 29 , 36 patient-oriented outcomes, including functional performance, 4 , 36 , 42 , 43 , 54 self-reported function, 27 , 45 rates of return to play, 2 and secondary ACL injury risk. 15 Despite the clear importance of recovering quadriceps function during rehabilitation, regaining function after treatment may not always be possible, and inability to address these limitations may predispose individuals to long-term functional limitations, 49 declines in physical activity, 3 and an elevated risk of developing knee osteoarthritis.…”

Anterior Cruciate Ligament Reconstructed Female Athletes Exhibit Relative Muscle Dysfunction After Return to Sport

“…central activation failure) has been suggested to prevent full quadriceps activation by decreasing motor unit recruitment and firing frequency during quadriceps muscle contraction and may contribute to sustained quadriceps weakness [40,41]. Arthrogenic muscle inhibition may therefore prevent INV leg quadriceps strengthening during rehabilitation due to a lack of muscle fiber stimulation, potentially leading to muscle atrophy, weakness and reduced joint stability [37,38,40]. Finally, psychological factors such as motivation and confidence, expectations and fear of re-injury may also affect ACLR athletes' training, rehabilitation and RTS outcomes [42,43].…”

The Immediate Effects of Transcranial Direct Current Stimulation on Quadriceps Muscle Function in Individuals With a History of Anterior Cruciate Ligament Reconstruction: A Preliminary Investigation

“…This may speak to the increased fatigability of the quadriceps muscle following ACLR, even during low demand task such as walking. 27,28 Even with a decline in EMG activity from the walking session, we still believed that tDCS would at least be protective to the EMG decline comparative to the sham session. Thus, our results are contrary to our hypothesis, as we had believed that tDCS would increase muscle activity from pretreatment to posttreatment (or preserve muscle activity), allowing for more muscle activation to be available during exercise.…”