Background:It has been shown that chronic ankle instability (CAI) leads to abnormalities in neuromuscular control of more proximal joints than the ankle. Although strength of the hip and the ankle muscles has been largely investigated providing concordant results, limited evidence with contrasting results has been reported regarding knee extensor and flexor muscles.Purpose:To investigate maximal and submaximal isometric muscle strength in individuals with CAI.Study Design:Controlled laboratory study.Methods:Fifteen participants with unilateral CAI and 15 healthy matched controls were recruited. To quantify maximal strength, peak forces were recorded during a maximal isometric voluntary contraction of knee extensor and flexor muscles at 30° and 90° of knee flexion and normalized by the body weight of each participant. At both angles, submaximal isometric contractions at 20%, 50%, and 80% of the maximal voluntary isometric contraction were performed to analyze strength steadiness, in terms of coefficient of variation, and strength accuracy, in terms of absolute error. During all the assessments, knee extensor and flexor muscle activation was recorded by means of surface electromyography.Results:Knee flexor maximal isometric strength was significantly lower in the injured limb of individuals with CAI in comparison with healthy controls at both 30° (0.15 ± 0.05 vs 0.20 ± 0.05; P < .05) and 90° (0.14 ± 0.04 vs 0.18 ± 0.05; P < .05). Knee extensor and flexor steadiness was significantly lower (higher coefficient of variation) in both the injured and the noninjured limbs of individuals with CAI in comparison with healthy individuals at 90° and at 30° for knee flexor steadiness of the injured limb. Knee extensor and flexor accuracy was lower (higher absolute error) in both the injured and noninjured limbs of individuals with CAI in comparison with healthy individuals, mainly at 30°, while at 90° it was lower only in the injured limb. No differences between the 2 groups were found for maximal isometric strength of knee extensor muscles, as well as for muscle activations.Conclusion:Individuals with CAI show abnormalities in maximal and submaximal isometric strength of knee flexor muscles, and submaximal strength of the knee extensor muscles. Further studies should deeply investigate mechanisms leading to these abnormalities.Clinical Relevance:Rehabilitation interventions should consider abnormalities of neuromuscular control affecting joints more proximal than the ankle in individuals with CAI.Registration:NCT05273177 (ClinicalTrials.gov identifier).

中文翻译：

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患有慢性踝关节不稳定性的个体在膝关节伸肌和屈肌的最大和次最大等长肌力方面表现出异常


背景：研究表明，慢性踝关节不稳定（CAI）会导致比踝关节更近端的关节的神经肌肉控制异常。尽管对髋部和踝部肌肉的力量进行了广泛的研究，得出了一致的结果，但关于膝关节伸肌和屈肌的证据却有限，结果却相反。目的：研究 CAI 患者的最大和次最大等长肌力。研究设计：对照实验室研究。方法：招募了 15 名单侧 CAI 参与者和 15 名健康匹配对照。为了量化最大力量，在膝关节屈曲 30° 和 90° 时记录膝关节伸肌和屈肌的最大等长自主收缩期间的峰值力，并通过每个参与者的体重进行标准化。在两个角度，分别进行最大自主等长收缩的 20%、50% 和 80% 的次最大等长收缩，以分析力量稳定性（变异系数）和力量准确性（绝对误差）。在所有评估过程中，通过表面肌电图记录膝关节伸肌和屈肌的激活情况。结果：与健康对照相比，CAI 患者受伤肢体的膝屈肌最大等长肌力在 30° 和 30° 下均显着较低（0.15 ± 0.05与 0.20 ± 0.05；P < .05) 和 90° (0.14 ± 0.04 与 0.18 ± 0.05；P < .05)。与健康个体相比，在 90° 和 30° 时，CAI 患者的受伤肢体和未受伤肢体的膝关节伸肌和屈肌稳定性均显着较低（变异系数较高）。 与健康个体相比，CAI 患者的受伤肢体和未受伤肢体的膝关节伸肌和屈肌精度均较低（绝对误差较高），主要在 30° 时，而在 90° 时仅在受伤肢体中较低。两组之间的膝伸肌最大等长肌力以及肌肉激活没有差异。结论：患有 CAI 的个体在膝屈肌最大和次最大等长肌力以及膝伸肌次最大肌力方面表现出异常。进一步的研究应深入调查导致这些异常的机制。临床相关性：康复干预应考虑神经肌肉控制异常影响 CAI 患者比踝关节更近端的关节。注册：NCT05273177（ClinicalTrials.gov 标识符）。