Abstract: Background: As the knee joint is a common site for injury among younger people,\nthe purpose of this study was to measure the skeletal muscle endurance and strength on people\nwith prior anterior cruciate ligament (ACL) knee reconstruction surgery. Method: Young healthy\nfemale subjects who reported having knee reconstruction surgery more than one-year prior were\ntested. The skeletal muscle endurance index (EI) of the hamstrings and quadriceps muscles was\ndetermined as the decline in the specific muscle acceleration in response to 2 Hz, 4 Hz, and 6 Hz\nelectrical stimulation. Maximal isometric muscle strength (MVC) was measured in the hamstrings\nand quadriceps muscles. Results: The hamstrings muscles in the injured leg had less endurance\nthan the non-injured leg at 6 Hz stimulation (55.5 Â} 13.2% versus 78.0 Â} 13.3%, p < 0.01). Muscle\nendurance was not reduced in the quadriceps muscles in the injured leg compared to the non-injured\nleg at 6 Hz stimulation (78.0 Â} 13.3% versus 80.3 Â} 10.0%, p = 0.45). There were no differences in MVC\nbetween the injured and non-injured legs for either the hamstrings (p = 0.20) or quadriceps muscles\n(p = 0.67). Conclusions: Muscle endurance was reduced in the hamstrings muscles at least one-year\npost injury, while hamstrings strength was recovered. Reduced hamstrings muscle endurance could\nbe a result of lack of endurance training during rehabilitation. This may contribute to re-injury in the\nmuscle, even in people who have recovered muscle strength.
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