The stability of EMG median frequency under different muscle contraction conditions and following anterior cruciate ligament injury

摘要: Musculoskeletal injuries are commonly associated with muscle atrophy as a function of immobilization or change normal function. For example, to the anterior cruciate ligament (ACL) which may involve reconstruction, results in "quadriceps avoidance" gait leads knee extensormuscles. In these situations it is not clear whether loss specific fibre types accompanying functional deficits. Such knowledge would be helpful implementing exercise regimes designed compensate for particular types. It believed that isokinetic performed at speeds below 180° per second strengthens type I fibres, and II fibres fast speeds. However, there no evidence indicate response different rates contraction. Identification most directly determined by biopsy technique but too invasive routine measurement. Electromyography median frequency has been used non-invasive measure infer composition various studies. reliability and accuracy this questioned improvement necessary. This research was provide more accurate reliable protocol determination EMG median frequency may be used, after validation against direct techniques, method inferring composition. The investigation also explored muscular measured varying contraction, fatiguing following ACL reconstruction. The ultimate aim improve the determination enhance its application predictor This provides information rehabilitation programs restore prevent have previously targeted current programs. conducted three studies. Study one stability bilaterally quadriceps hamstrings muscles identified mode contraction greatest reliability. strength vastus lateralis, medial medialis 55 subjects was determined across 5 from 0° 240° using Kin-Com dynamometer an data acquisition system. Isometric found least bilateral discrepancy (4.01% ±3.06) between trials standard deviation (4.50) medialis. Study two investigated changes lateralis occur immediately point fatigue subjects. Thirty-four participated study, 90-second period activate extensors either 30° 300° second. before, after 7 minutes fatiguing exercise. percentage drop gnificantly (p<0.05) greater slow speed (27.9%) than (20.25%) exercise, while significant difference extension torque. Full recovery By reference previous showing relationship type, increase activation II muscle observed. Study reconstruction evaluated differences muscles. relationships measures ability, strength, age time since surgery were investigated. Twelve who had undergone semitendinosus gracilis graft 6 12 months earlier, study. 8-second isometric ability assessed Cincinnati Rating Scale. Bilateral shifts inconsistent among On basis indicated a relationship consistent pattern subsequent occurred within 12 months (ranged -43 57 Hz). Additionally, correlations between the score flexion torques, age, operation frequency. investigation will serve range conditions been evaluated. Further needed confirm observations predictive value measure. Following possible evaluate shift atrophy, use determining efficacy programs. In conclusion * An recommended frequency. * decreases significantly exercise. * There generalised group reconstruction. * study procedures determine under contractile conditions. require further validations future.