Effect of Contraction Type, Angular Velocity, and Arc of Motion on VMO:VL EMG Ratio.

This research was supported by a grant from the Walter P. Inman Fund through the Duke University Medical Research Council. Selected quadriceps muscle action may influence the movement path of the patella in the malaligned patellofemoral joint. The purpose of this study was to investigate the effects of arc of motion, angular velocity, and contraction type on the vastus medialis obliques:vastus lateralis (VMO:VL) absolute averaged electromyographic (AAEMG) ratio. Thirty healthy subjects performed maximum concentric and eccentric isokinetic quadriceps muscle contractions on the Kin-Com(R) dynamometer at velocities of 60 and 120 degrees /sec. Electromyography data from the VMO and the VL were acquired, and a VMO:VL AAEMG ratio was calculated for all combinations of the three independent variables. The results indicate that the VMO:VL AAEMG ratio for the 60 degrees -85 degrees arc was significantly greater than the ratio for the 35 degrees -60 degrees arc (p < 0.05), the ratio for the 60 degrees -85 degrees arc was significantly greater than the ratio for the 10 degrees -35 degrees arc (p < 0.05), and the ratio for the 35 degrees -60 degrees arc was significantly greater than the ratio for the 10 degrees -35 degrees arc (p < 0.05). The VMO:VL AAEMG ratio for concentric contraction at 120 degrees /sec was significantly greater than the ratio for concentric contraction at 60 degrees /sec (p < 0.05) and was significantly greater than the ratio for eccentric contraction at 120 degrees /sec (p < 0.05). The results indicate that the VMO:VL AAEMG ratio is affected by isokinetic exercise parameters. The use of isokinetic exercise parameters that produce a greater VMO:VL AAEMG ratio may be effective in altering muscular imbalance between the VMO and VL. J Orthop Sports Phys Ther 1991;14(6):256-262.

[1]  I. Fiebert,et al.  EMG Biofeedback as Treatment for Patellofemoral Pain Syndrome*. , 1984, The Journal of orthopaedic and sports physical therapy.

[2]  D. C. Howell.  Statistical Methods for Psychology , 1987 .

[3]  K. M. Singer,et al.  Patellofemoral disorders: physical and radiographic evaluation. Part II: Radiographic examination. , 1984, Clinical orthopaedics and related research.

[4]  J. Richards,et al.  Analysis of the reliability and validity of the kinetic communicator exercise device. , 1986, Medicine and science in sports and exercise.

[5]  B. Brownstein,et al.  Quadriceps torque and integrated electromyography*. , 1985, The Journal of orthopaedic and sports physical therapy.

[6]  J. C. Hughston,et al.  Patellar subluxation and dislocation , 1984 .

[7]  G. Bentley,et al.  Current concepts of etiology and treatment of chondromalacia patellae. , 1984, Clinical orthopaedics and related research.

[8]  D. Kettelkamp.  Management of patellar malalignment. , 1981, The Journal of bone and joint surgery. American volume.

[9]  Michael T. Gross,et al.  Comparison of Vastus Medialis Obliquus:Vastus Lateralis Muscle Integrated Electromyographic Ratios Between Healthy Subjects and Patients with Patellofemoral Pain , 1991 .

[10]  P. G. Kramer.  Patella malalignment syndrome: rationale to reduce excessive lateral pressure. , 1986, The Journal of orthopaedic and sports physical therapy.

[11]  Case study: persistent ankle pain- the os trigonurn duly considered. , 1987, The Journal of orthopaedic and sports physical therapy.

[12]  J. Perry,et al.  Quadriceps function. An anatomical and mechanical study using amputated limbs. , 1968, The Journal of bone and joint surgery. American volume.

[13]  W C Hayes,et al.  Patellofemoral contact pressures. The influence of q-angle and tendofemoral contact. , 1984, The Journal of bone and joint surgery. American volume.

[14]  J. Fulkerson.  The etiology of patellofemoral pain in young, active patients: a prospective study. , 1983, Clinical orthopaedics and related research.

[15]  J. Goodfellow,et al.  Patello-femoral joint mechanics and pathology. 2. Chondromalacia patellae. , 1976, The Journal of bone and joint surgery. British volume.

[16]  M. M. Malek,et al.  Patellofemoral pain syndromes: a comprehensive and conservative approach. , 1981, The Journal of orthopaedic and sports physical therapy.

[17]  T A Fox,et al.  Dysplasia of the quadriceps mechanism: hypoplasia of the vastus medialis muscle as related to the hypermobile patella syndrome. , 1975, The Surgical clinics of North America.