Background Resistive lateral leg reach exercise (RLLR), a single-limb squat with resistance, increases load on the gluteal muscles and is effective for preventing knee valgus moment, a major factor in anterior cruciate ligament (ACL) injury. To enhance the load during RLLR, we devised a novel isokinetic exercise machine.
Objective To investigate the biomechanical and electromyographic (EMG) characteristics of the support leg during RLLR with isokinetic resistance (RLLR-I).
Setting Controlled laboratory setting.
Participants 8 asymptomatic recreational-level female college athletes.
Intervention Participants performed RLLR-I and lateral leg reach without resistance (LLR). The resistance device was set to 25 cm/s during RLLR-I. A three-dimensional motion capture system and force plate were used for motion analysis. Surface electrodes recorded the EMG at each muscle site: gluteus maximus (GMa), gluteus medius (GMe), rectus femoris, vastus medialis (VM), biceps femoris, adductor longus, soleus, and gastrocnemius.
Main outcome measurements The external knee valgus/varus moment and the internal joint moment of the support leg were calculated using software. EMG root mean squared amplitude was normalized as a percentage of maximum voluntary contraction (%MVC).
Results RLLR-I was characterized by a significantly larger internal hip abduction moment (2.2±1.0 Nm/kg) and significantly larger VM (152±54 %MVC), GMa (92±47 %MVC), and GMe (97±33 %MVC) activity compared with LLR (hip abduction moment: 1.5±0.7 Nm/kg; VM: 102±40 %MVC; GMa: 35±25 %MVC; and GMe: 38±13 %MVC). No significant external knee valgus moment occurred during RLLR-I.
Conclusion RLLR-I serves to increase the load on the VM and gluteal muscles and is effective for preventing external knee valgus moment. These findings suggest that this novel isokinetic exercise will be useful for preventing ACL injury and in rehabilitation after ACL reconstruction.
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