TITLE: THE EFFECT OF KNEE ANGLE AND RESISTANCE PLACEMENT ON THE EMG ACTIVITY AND ISOMETRIC TORQUE PRODUCTION OF KNEE MUSCLES IN PATIENTS WITH OSTEOARTHRITIS.
AUTHORS: Mohamed Kohia, Kelsey Brucks, Ruthanne McCreary, Stephanie Schultz, Hailee Stover, and Jordan Zuccarelli; Rockhurst University, Kansas City, MO.
PURPOSE/HYPOTHESIS: Resistance training has shown promising results in the non-operative treatment of knee osteoarthritis (OA). As of today, no study has examined the combined effect of resistance placement and knee joint angle on torque production and electromyography (EMG) activity of knee muscles. The purpose of this study was to determine the optimal resistance placement and knee angle to maximize muscle activity and torque production of the quadriceps and hamstrings during resistance training in patients with knee OA.
SUBJECTS: A total of 8 subjects (2 male, 6 female), ages 42 to 64 (mean age 52.4 ± 8.2 years) with a diagnosis of knee OA participated in this study.
METHOD: The quadriceps and hamstrings peak torque of both legs was tested using Biodex Isokinetic Dynamometer at two resistance placements (proximal and distal) and three knee flexion angles (30°, 45°, and 75°). The order of angle selection and resistance placement was randomized to avoid effects of fatigue. Surface bipolar electrodes were secured to the vastus medials (VM), vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), and semintendenosis (ST) / semimebranosis (SM) to record the EMG activity of those muscles during maximal isometric contraction. Rest periods were allotted between trials to avoid fatigue.
RESULTS: For quadriceps isometric torque, there was a significant difference between the 3 angles (P=.031) with 75o>45o>30o. Torque production of the quadriceps was significantly greater when the resistance was placed distally (P=.031). For hamstrings, the torque produced was significantly greater at 30o (P=.001). The EMG activity of the VM, VL, RF, and BF didn’t significantly differ between angles or resistance placement. However, the semitendinosus EMG activity was dependent on angles (P<.000), with 75o being significantly higher.
CONCLUSION: The results of this study suggest that the quadriceps are more efficient in isometric torque production at 75° of knee flexion and with a distal resistance placement. During isometric knee flexion, the hamstrings are more efficient in torque production at 30°, and the semitendinosus is more active at 75°. It is our recommendation to consider this application when strengthening the quadriceps and hamstrings in patients with knee OA. The results of this study will guide physical therapists to apply more efficient and effective treatments during knee rehabilitation of patients with OA.
AUTHORS: Mohamed Kohia, Kelsey Brucks, Ruthanne McCreary, Stephanie Schultz, Hailee Stover, and Jordan Zuccarelli; Rockhurst University, Kansas City, MO.
PURPOSE/HYPOTHESIS: Resistance training has shown promising results in the non-operative treatment of knee osteoarthritis (OA). As of today, no study has examined the combined effect of resistance placement and knee joint angle on torque production and electromyography (EMG) activity of knee muscles. The purpose of this study was to determine the optimal resistance placement and knee angle to maximize muscle activity and torque production of the quadriceps and hamstrings during resistance training in patients with knee OA.
SUBJECTS: A total of 8 subjects (2 male, 6 female), ages 42 to 64 (mean age 52.4 ± 8.2 years) with a diagnosis of knee OA participated in this study.
METHOD: The quadriceps and hamstrings peak torque of both legs was tested using Biodex Isokinetic Dynamometer at two resistance placements (proximal and distal) and three knee flexion angles (30°, 45°, and 75°). The order of angle selection and resistance placement was randomized to avoid effects of fatigue. Surface bipolar electrodes were secured to the vastus medials (VM), vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), and semintendenosis (ST) / semimebranosis (SM) to record the EMG activity of those muscles during maximal isometric contraction. Rest periods were allotted between trials to avoid fatigue.
RESULTS: For quadriceps isometric torque, there was a significant difference between the 3 angles (P=.031) with 75o>45o>30o. Torque production of the quadriceps was significantly greater when the resistance was placed distally (P=.031). For hamstrings, the torque produced was significantly greater at 30o (P=.001). The EMG activity of the VM, VL, RF, and BF didn’t significantly differ between angles or resistance placement. However, the semitendinosus EMG activity was dependent on angles (P<.000), with 75o being significantly higher.
CONCLUSION: The results of this study suggest that the quadriceps are more efficient in isometric torque production at 75° of knee flexion and with a distal resistance placement. During isometric knee flexion, the hamstrings are more efficient in torque production at 30°, and the semitendinosus is more active at 75°. It is our recommendation to consider this application when strengthening the quadriceps and hamstrings in patients with knee OA. The results of this study will guide physical therapists to apply more efficient and effective treatments during knee rehabilitation of patients with OA.