Vastus Lateralis Ratio Research Articles

Vastus Lateralis and Vastus Medialis Obliquus Activity during a Straight-Leg Raise and Knee Extension with Lateral Hip Rotation

Objective:To compare average electromyogram (EMG) activity of the vastus medialis obliquus (VMO) and vastus lateralis (VL) during straight-leg raise (SLR) and knee extension (KE) with the hip in neutral and lateral rotation.Design:1 × 4 factorial repeated-measures.Setting:Laboratory.Participants:13 male college students.Intervention:SLR with hip flexed at 40°, in neutral position, and maximally laterally rotated and KE with hip in neutral and maximally laterally rotated.Main Outcome Measure:Average EMG activity during each of the 4 conditions, normalized against peak muscle activity during that trial.Results:No differences were observed between exercises in VMO activity (F3,36 = 0.646, P > .05), VL activity (F3,36 = 1.08, P > .05), or VMO:VL ratio (F3,36 = 0.598, P > .05).Conclusions:Electrical activity of the VMO or VL and VMO:VL ratio do not change with hip position or exercise.

Electromyographic fatigue characteristics of the quadriceps in patellofemoral pain syndrome

This study compared the fatigue characteristics of the vastus medialis oblique (VMO), vastus lateralis (VL) and rectus femoris (RF) muscles. Ten healthy subjects with 10 patients with patellofemoral pain syndrome (PFPS) performed an isometric leg press for 60 seconds at 60% MVIC with data collected using surface EMG. The power spectrum was analyzed and the extracted median frequency normalised to calculate a linear regression slope for each muscle. A repeated measures ANOVA revealed no significant differences, neither between the groups (P=0.592) nor the muscles (P=0.434). However, the slopes for the VMO and VL were different between the two groups with similar slopes for the RF. There was much larger variability of MF values in the PFPS group. The VMO:VL ratio calculated from these slopes for the healthy subjects was 1.17 and for the PFPS group was 1.78. These results may indicate unusual features in the fatigue indices of the quadriceps in PFPS.

Medial and Lateral Quadriceps Muscle Activity during Weight-Bearing Knee Extension Exercise

The purpose of this study was to determine the effect of weight-bearing terminal knee extension (WBKE) on normalized mean electromyographic (EMG) activity of the vastus medialis oblique (VMO) and vastus lateralis (VL) and the VMO/VL ratio. Sixteen subjects with no history of knee dysfunction participated. Surface EMG data were recorded from the VMO and VL of subjects' test legs as they performed the WBKE exercise under four conditions, three involving elastic resistance and one involving no elastic resistance. EMG data were normalized relative to a maximal isometric quadriceps contraction, and overall mean VMO and VL activity and the VMO/VL ratio were determined for all conditions. The three conditions utilizing elastic resistance showed higher mean VMO and VL activity than the no-resistance condition. The VMO/ VL ratio was not significantly altered during any exercise condition as compared to maximal, quadriceps setting exercise. WBKE against elastic resistance was superior to the same exercise without resistance for generating mean VMO and VL activity. Performance of the WBKE, regardless of the position of lower extremity rotation, does not selectively activate the VMO apart from, or to a greater degree than, the VL.

Effect of the vastus medialis obliquus on the patellofemoral joint.

In this study, the effect of dynamic stabilizers on the patellofemoral (PF) joint was investigated in normal volunteers (group I) and in patients with patellar pain (group II) or instability (group III) by using computed tomography (CT) analysis and integrated electromyography (iEMG) of the quadriceps muscle. Nine subjects (16 knees) from group I, 10 patients (12 knees) from group II and 8 patients (12 knees) from group III were included in the study. CT scans of the PF joint with quadriceps contracted (QC) and uncontracted (QU) and iEMG of vastus medialis obliquus (VMO), vastus lateralis (VL) and rectus femoris (RF) were obtained with the aid of a specially designed jig at 0 degree, 15 degrees, 30 degrees and 45 degrees of knee flexion. The same muscle contraction pattern simulating closed kinetic chain exercise was used for both CT and iEMG. The difference between the congruence angles (CA) and tilt angles (PTA) in QC and QU positions and VMO:VL ratio from the iEMG were calculated separately for each flexion angle. CA was increased in all groups with quadriceps contraction at 0 degree and 15 degrees of flexion. PTA was decreased in group I and increased in groups II and III with quadriceps contraction at the same flexion angles. This difference was statistically significant in group III at 0 degree and 15 degrees of flexion. Quadriceps contraction did not affect the patellar position significantly even in the instability group at 45 degrees of flexion. In all flexion angles the balanced VMO:VL activity ratio was observed only in group I. In the other groups, VL activity was higher than VMO activity except at 45 degrees of flexion. These findings do not support the hypothesis of dominant centralizing effect of VMO on the patella in extension, but the effect of the VMO may be more clearly demonstrated by measuring PTA in both QC and QU positions.

Vastus Medialis Obliquus and Vastus Lateralis Activity in Patients with and without Patellofemoral Pain Syndrome

The purpose of this study was to examine the efficacy of closed kinetic chain exercises in preferentially recruiting the oblique fibers of the vastus medialis obliquus (VMO). Fifteen athletically active females, 6 with patellofemoral pain syndrome (PFPS) and 9 without PFPS, performed two isometric and two dynamic closed kinetic chain exercises. The isometric exercises were a static lunge with 30° of knee flexion (SL@30°) and with 70° of knee flexion (SL@70°). The dynamic exercises were a step-up/step-down exercise (SUSD) and a modified wall slide (MWS). Selective recruitment of the VMO occurred during the MWS (p <.05) and the SUSD in the subjects without PFPS (p <.05). For the SL@70° (p <.01), the MWS (p <.01), and the SUSD (p <.05), subjects with PFPS had greater activity of the vastus lateralis (VL), resulting in a lower VMO: VL ratio for those exercises (p < .05). It was concluded that the closed kinetic chain exercises examined in this study do not preferentially recruit the VMO in individuals with PFPS. In addition, individuals with PFPS have a lower VMO:VL ratio during these exercises compared to individuals without PFPS.

THE EFFECT OF KNEE TAPING ON THE EMG ACTIVITY OF THE VASTUS MEDIALIS OBLIQUE AND VASTUS LATERALIS MUSCLES 1202

Patellofemoral pain syndrome is a common complaint in athletes and physically active individuals and has long been a major concern of Sports Medicine practitioners. The purpose of this investigation was to examine the effect of different patella taping procedures on the electromyographic (EMG) activity of the Vastus Medialis Oblique (VMO) and Vastus Lateralis (VL) muscles. Four female university students volunteered for this study. The subjects had a history of previous knee pathology and current symptoms of Patellofemoral pain. The EMG signals were recorded using surface electrodes. Average EMG was obtained by rectifying and smoothing the raw waveform using an electronic contour follower integrator with a time constant of 50 ms. The EMG activity was normalized to the percentage of maximum activity for each muscle before being analyzed. An electro-goniometer was used to measure knee flexion angle. After placement of the surface electrodes each subject performed 2 maximum isometric trials with a knee angle of 90°. After 10 minutes of rest the subjects performed three 10 sec repetitions of a submaximal wall squat exercise at a rate of 30 per sec under four conditions; control (No Tape), taping on a medial, lateral and no glide position. The results indicated that the total EMG activity produced by the VMO and VL muscles throughout the ROM was significantly different between the taping conditions(p<.05). The VL activity was reduced for all taping conditions. The peak EMG activity of the VMO and VL muscles was significantly different between the two muscles and between the taping conditions (p<.05). The most important finding was that the VMO:VL ratio increased for all taping conditions and were all above 1.0.

EMG Activity of Six Muscles and VMO:VL Ratio Determination during a Maximal Squat Exercise

During knee rehabilitation, squats are a commonly used closed kinetic chain exercise. We have been unable to locate data reporting electromyographic (EMG) activity of lower extremity musculature during maximal effort squats and the contribution of gastrocnemius and gluteus maximus muscles. Therefore, the purposes of this study were (a) to quantify EMG activity of selected lower extremity muscles during a maximal isometric squat and during a maximal voluntary isometric contraction (MVIC), and (b) to determine ratios between the vastus medialis oblique (VMO) and vastus lateralis (VL) during maximal isometric squat and MVIC testing. Twenty-three subjects participated in a single testing session. Results are as follows: intraclass correlations for MVIC testing and squat testing ranged from .60 to .80 and .70 to .90, respectively. Percentage MVIC during the squat was as follows: rectus femoris 40 ± 30%, VMO 90 ± 70%, VL 70 ±40%, hamstrings 10 ± 10%, gluteus maximus 20 ± 10%, and gastrocnemius 30 ± 20%. No statistical difference existed in VMO:VL ratios during MVIC or squat testing. We conclude that large variations in muscle recruitment patterns occur between individuals during isometric squats.

Quadriceps femoris muscle activity in patellofemoral pain syndrome.

To elucidate and attempt to dissociate the two mechanisms, neuromuscular and mechanical, underlying patellofemoral pain syndrome, 18 subjects, divided into two groups based on a diagnosis of patellofemoral pain syndrome and the knee Q angle, were studied. The control group was asymptomatic and exhibited a normal Q angle (mean, 8.25 degrees), whereas the other group, diagnosed as patellofemoral pain syndrome patients, reported knee pain and had an above-normal Q angle (mean, 21.05 degrees). All subjects were tested for isometric maximum knee extension at 90 degrees, 30 degrees, and 15 degrees of knee flexion while they were seated in a special restraining chair. During testing, surface electromyography at the oblique and long fibers of the vastus medialis, and at the vastus lateralis were recorded along with the knee moment of force. The integrated electromyographic signals associated with the peak torque for all of the vastus muscles, along with the vastus medialis obliquus:vastus lateralis and vastus medialis longus:vastus lateralis activity ratios showed no significant differences between groups nor between the three angles, suggesting that all vasti measured were consistently active throughout the studied range of motion. This suggests that the neural drive was not affected in the patellofemoral pain syndrome patients. However, when the five patients showing the largest Q angles were isolated, they revealed a significantly smaller vastus medialis obliquus:vastus lateralis ratio when compared to the other group. The same ratio was also significantly smaller at 15 degrees compared to 90 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)