Vastus Medialis Oblique Activity Research Articles

Is muscle activation diverse in females with isolated patellofemoral osteoarthritis contrasted with age-matched healthy controls during stair descent task?

Background: Patellofemoral osteoarthritis (PF OA) is exceptionally predominant and limiting. However, little is known about the risk factors that contribute to its onset and progression. Purpose: The aim of this study was to decide if women with PF OA descend stairs using different muscular activation strategies compared to similarly aged healthy controls. Methods: Thirty-one women with isolated PF OA and 11 similarly aged healthy women took part in this study. The activation onset and duration of PF OA in vastus medialis oblique (VMO), vastus lateralis (VL), gluteus medius (GM), transversus abdominis (TrA), and multifidus muscles were evaluated during the stair descent task using surface electromyography (EMG). Results: There was a non-significant difference between women with PF OA and healthy controls regarding all tested variables, except for the GM activation onset that was significantly delayed in women with PF OA, with the p-value of 0.011. Conclusion: The causes of PF OA differ and might not always be due to a lack of quadriceps strength or VMO activation deficiency, and prospective longitudinal studies are required to confirm this assumption.

Activation, strength, and resistance: Which variables predict the kinematics of women with and without patellofemoral pain?

IntroductionInvestigating the possible relationship between neuromuscular changes and movement alterations could help to describe the mechanisms underlying patellofemoral pain (PFP). ObjectiveTo investigate whether activation and muscle strength of the trunk and lower limb and muscle resistance of the trunk predict the knee frontal and trunk sagittal kinematics in women with and without PFP. MethodSixty women (PFP, n = 30; asymptomatic, n = 30) underwent the single-leg squat test to collect electromyographic and kinematic data. Activation of transversus abdominis/internal oblique, gluteus medius (GMed), and vastus medialis oblique (VMO); knee frontal and trunk sagittal angles were analyzed. Participants also underwent maximal isometric tests to determine lateral trunk, hip abductor, and knee extensor torques and performed a lateral trunk resistance test. Multiple regression was used to determine predictive models. ResultsIn the PFP group, knee frontal angle (R2 = 0.39, p = 0.001) was predicted by GMed activation (β = 0.23, p = 0.000) and hip abductor torque (β = 0.08, p = 0.022). No variable was able to predict trunk sagittal kinematics in this group. In the asymptomatics, knee frontal angle (R2 = 0.16, p = 0.029) was predicted by hip abductor torque (β = 0.07, p = 0.029), while trunk sagittal angle (R2 = 0.24, p = 0.024) was predicted by VMO activation (β = 0.12, p = 0.016). ConclusionKinematics is predicted by the muscles acting in the respective planes, such that hip abductors capacities are related to the knee frontal alignment in both groups, and that of the VMO is related to the trunk sagittal alignment only in asymptomatic women.

Neuromotor Treatment of Arthrogenic Muscle Inhibition After Knee Injury or Surgery.

Persistent weakness of the quadriceps muscles and extension deficit after knee injuries are due to specific alterations in neural excitability - a process known as arthrogenic muscle inhibition (AMI). The effects of a novel neuromotor reprogramming (NR) treatment based on the use of proprioceptive sensations associated with motor imagery and low frequency sounds have not been studied in AMI after knee injuries. This study aimed to assess quadriceps electromyographic (EMG) activity and the effects on extension deficits in persons with AMI who completed 1 session of NR treatment. We hypothesized that the NR session would activate the quadriceps and improve extension deficits. Case series. Level 4. Between May 1, 2021 and February 28, 2022, patients who underwent knee ligament surgery or sustained a knee sprain with a deficit of >30% of the vastus medialis oblique (VMO) on EMG testing in comparison with the contralateral limb after their initial rehabilitation were included in the study. The maximal voluntary isometric contraction of the VMO measured on EMG, the knee extension deficit (distance between the heel and the table during contraction), and the simple knee value (SKV) were assessed before and immediately after completion of 1 session of NR treatment. A total of 30 patients with a mean age of 34.6 ± 10.1 years (range, 14-50 years) were included in the study. After the NR session, VMO activation increased significantly, with a mean increase of 45% (P < 0.01). Similarly, the knee extension deficit significantly improved from 4.03 ± 0.69 cm before the treatment to 1.93 ± 0.68 after the treatment (P < 0.01). The SKV was 50 ± 5.43% before the treatment, and this increased to 67.5 ± 4.09% after the treatment (P < 0.01). Our study indicates that this innovative NR method can improve VMO activation and extension deficits in patients with AMI. Therefore, this method could be considered a safe and reliable treatment modality in patients with AMI after knee injury or surgery. This multidisciplinary treatment modality for AMI can enhance outcomes through the restoration of quadriceps neuromuscular function and subsequent reduction of extension deficits after knee trauma.

Improvement of Pain and Function by Using Botulinum Toxin Type A Injection in Patients with an Osteoarthritic Knee with Patellar Malalignment: An Electromyographic Study.

Objective: To determine the pain and electromyographic (EMG) amplitude ratio of the vastus medialis oblique (VMO) to the vastus lateralis (VL) after botulinum toxin type A (BTA) was injected in the bilateral osteoarthritic knee of patients with patellar malalignment for analysis. Material and methods: A total of fifteen patients were recruited; the more symptomatic knee of each patient received a BTA injection (BTA side). The other set of patients were left untreated. In all, fifteen healthy participants comprised the control group. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and numeric rating scale (NRS) for pain were assessed. The EMG amplitude of VL and VMO activity was recorded using an isokinetic dynamometer and synchronized using the BIOPAC MP100. The data were collected before and at 4, 8, and 12 weeks post−BTA injection. Results: The EMG ratios of the patient group were lower than those of the control group at all testing velocities (p < 0.05). The VMO/VL ratio improved significantly on the BTA side only. The VMO/VL ratios on the BTA side were higher than those on the untreated side (p < 0.05). Knee pain decreased significantly after the BTA injection. The EMG ratios were negatively correlated with the NRS and WOMAC scores. Conclusion: BTA injection effectively reduces knee pain and restores the EMG ratio between the VMO and VL.

Quadriceps Electromyographic Activity in Closed and Open Kinetic-Chain Exercises with Hip-Adductor Co-Contraction in Sedentary Women.

Background: Different closed and open kinetic-chain exercises with hip-adductor co-contraction have different effects on quadriceps activity. The aim of this study was to investigate the difference in quadriceps activity during the squat (SQ) and knee extension (KE) and straight leg raise (SLR) exercises with and without hip adduction in sedentary women. Methods: Twenty-eight sedentary women aged 44.5 ± 8.5 years were recruited. They performed three exercises with and without hip adduction. Surface electromyography (sEMG) activity was measured on the rectus femoris (RF), vastus medialis oblique (VMO) and vastus lateralis (VL) muscles. The levels of sEMG activities of the three muscles were compared among the six exercises using a repeated-measures ANOVA. Results: The findings showed that RF activity was lowest during the SQ alone and highest during the SLR exercise (p < 0.05 to 0.001). The VMO activity was significantly greater in the SQH than in the five types of exercises (p < 0.05 to 0.001), which led to a significant VMO/VL ratio as well. VL activity increased while the squat with hip adduction and knee extension with hip adduction exercise compared with SQ alone. Conclusion: This study indicates that a closed-chain squat with hip co-contraction can produce the VMO and VMO/VL ratio activity, while an open chain of SLR better activates the RF activity. The findings support the understanding of quadriceps activity in different exercises to be an alternative home-based exercise for physical therapy in women facing muscle weakness.

Effects of the ankle angle on the electromyographic activity of the trunk and lower extremities during isometric squat exercises

Background: Life in modern society has become convenient, but the lack of exercise due to a sedentary lifestyle has led to muscle weakness. The quadriceps femoris is essential for walking, standing, and using stairs in daily life. Muscle weakness can lead directly to impaired function. Squatting is the most representative exercise for effective muscle development and increasing the knee extensor strength. This study examined the effects of ankle angle during wall squats on the muscle activity of the vastus medialis oblique (VMO), vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), rectus abdominis (RA), and erector spinae (ES) to determine which ankle angle can better strengthen the vastus medialis oblique as a method of rehabilitation training after a knee joint injury. Methods: All subjects (n = 20) performed the following three types of wall squats randomly: (1) GWS (General Wall Squat), (2) WSD 10° (Wall Squat with dorsiflexion 10°), and (3) WSP 10° (Wall Squat with plantarflexion 10°). Each subject completed all three kinds of wall squatting exercises three different times, and the muscle activity data of the VMO, VL, RF, BL, RA, and ES were recorded. Results: Compared to GWS exercise, the VMO and RF muscle activity increased significantly under WSP 10° exercise (p &lt; 0.05), whereas the VL, BF, RA, and ES activity did not increase significantly (p &gt; 0.05). No significant change between WSD 10° and WSP 10° was observed (p &gt; 0.05). Conclusions: WSP 10° can help increase the quadriceps muscle activity. Wall squat exercise with different ankle angles can be used for quadriceps muscle strengthening training for normal people and for recovery training for patellofemoral pain syndrome (PFPS) patients in the rehabilitation stage.

A Study to Compare the Activation of Vastus Medialis Oblique by EMG for three Different Exercises in Patient with Osteoarthrosis of Knee Joint: An Observational Study

Background and Objectives: Osteoarthritis (OA) also called as Osteoarthrosis or degenerative jointdisease,it is the most common form of common disorder of synovial joint.OA represents a major cause ofmorbidity and disability and as well as it having a significant economic burden on patients and health careresources.Dysfunction of the quadriceps muscle,specially vastus medialis (VM) ,has been hypothesized ascause of OA knee.Various studies evaluating the EMG activity for VMO in straight leg raise,knee extensionand weight bearing exercises like single leg stance to strengthen the quadriceps muscle in patient with OAknee but results are different.So,aim of the study is to compare the activation of VMO by EMG for threedifferent exercises in patients with osteoarthritis of knee joint.Methods: The study was conducted on 100 patients with OA knee with mean age of 49.36+5.58 (SD years).EMG activity of VMO was compared during MVIC with 10 RM in three different positions:1)straight legraise(SLR),2) terminal knee extension with medial rotation of hip ,3) Single leg stance at 30 degrees kneeflexion.Results : ANOVA and Tukey Kramer Multiple Comparison Test were used for statistical analysis.The resultrevealed that there is a significant increase in VMO muscle activity when testing position 1 compared withtesting position 2 and 3 but there was no significant difference was found between testing position 2 and 3.Conclusion: The result showed that terminal knee extension with medial rotation of hip and single leg stanceat 30 degrees knee flexion significantly activate the VMO than straight leg raise (SLR) .The comparison ofthese therapeutic exercises have been advanced to strengthen the quadriceps muscles and hence can be usedas early rehabilitation program in patient with OA knee.

Muscle Activation and Kinematic Analysis during the Inclined Leg Press Exercise in Young Females.

Knee joint muscle activation imbalances, especially weakness in the vastus medialis oblique, are related to patellofemoral pain within the female population. The available literature presents the leg press as an exercise which potentially targets vastus medialis oblique activation, thus reducing imbalances in the quadriceps muscles. The main aim of the present study was to compare thigh muscle activation and kinematic parameters under different conditions during the inclined leg press exercise in a young female population. A cross-sectional study was conducted on 10 young, trained females. Muscle activation of the vastus medialis oblique, vastus lateralis, rectus femoris and gluteus medialis was analyzed under five different inclined leg press conditions, modifying the feet rotation (0–45° external rotation) and the stance width (100–150% hip width) on the footplate. All the conditions were performed at two different movement velocities: controlled velocity (2″ eccentric–2″ concentric) and maximal intended velocity. Mean propulsive velocity, maximum velocity and maximum power were also assessed. The results show that both controlled velocity conditions and maximal intended velocity conditions elicited a similar muscle activation pattern with greater activation during the concentric phase (p < 0.001, ηp2 = 0.96). The maximal intended velocity conditions showed greater overall muscle activation (p < 0.001, ηp2 = 0.91). The vastus medialis oblique presented the greatest muscle activation, followed by the rectus femoris, vastus lateralis and, the gluteus medialis. Furthermore, the inclined leg press condition with 0º feet rotation, 100% hip width distance and the maximal intended velocity generated the greatest kinematic parameter outputs. In conclusion, the inclined leg press exercise might be an optimal exercise to target vastus medialis activation regardless of the feet rotation and stance width conditions.

Lower Limb Muscles Activity and Inclined Squat Position in Normal Children (Cross Sectional Study)

Background: Benefits associated with squat performance are not limited to the athletic population. Given that most activities of daily living necessitate the simultaneous coordinated interaction of numerous muscle groups, the squat is considered one of the best exercises for improving quality of life because of its ability to recruit multiple muscle groups in a single maneuver. Objective: To determine the effect of inclined squat position on the vastus medialis oblique (VMO) and gluteus maximus (GM) at the different ankle angles 5°-10° degrees of inclination in normal children. Subjects and methods: thirty non-athletic children of both genders, age ranged from 14 to 18 years, were selected from the Egyptian governmental schools at Sixth of October City and Sixth of October Sporting Club. The maximum voluntary isometric contraction (MVIC) was measured after the electrodes were attached to the GM and the VMO of the subject during squat postures which applied on two inclined borders 5 and 10 degree of inclination; the feet are spread out shoulder width, hip 70° flexion, knee 75° flexion and in the erect posture. Results: There was a significant increase in the VMO activity in 5° ankle angle compared with that of 10° ankle angle (p = 0.0001). There was a significant decrease in the GM activity in 5° ankle angle compared with that of 10° ankle angle (p = 0.0001). Conclusion: modification of ankle dorsiflexion during squat position should be integrated in the rehabilitation programs of the different injuries.

Lower Limb Muscles Activity and Inclined Squat Position in Normal Children (Cross Sectional Study)

Background: Benefits associated with squat performance are not limited to the athletic population. Given that most activities of daily living necessitate the simultaneous coordinated interaction of numerous muscle groups, the squat is considered one of the best exercises for improving quality of life because of its ability to recruit multiple muscle groups in a single maneuver. Objective: To determine the effect of inclined squat position on the vastus medialis oblique (VMO) and gluteus maximus (GM) at the different ankle angles 5°-10° degrees of inclination in normal children. Subjects and methods: thirty non-athletic children of both genders, age ranged from 14 to 18 years, were selected from the Egyptian governmental schools at Sixth of October City and Sixth of October Sporting Club. The maximum voluntary isometric contraction (MVIC) was measured after the electrodes were attached to the GM and the VMO of the subject during squat postures which applied on two inclined borders 5 and 10 degree of inclination; the feet are spread out shoulder width, hip 70° flexion, knee 75° flexion and in the erect posture. Results: There was a significant increase in the VMO activity in 5° ankle angle compared with that of 10° ankle angle (p = 0.0001). There was a significant decrease in the GM activity in 5° ankle angle compared with that of 10° ankle angle (p = 0.0001). Conclusion: modification of ankle dorsiflexion during squat position should be integrated in the rehabilitation programs of the different injuries.

Electromyographic analysis of VMO and VL across straight leg raise, short arc quad, medial tibial rotation and hip adduction in normal individuals.

The lateral malalignment of patella is considered to be the main cause of patellofemoral pain syndrome (PFPS). PFPS, in an occupational setup, is aggravated by prolonged sitting, climbing stairs, squatting, and kneeling. Strengthening of vastus medialis oblique (VMO) opposes the lateral force produced by vastus lateralis (VL) and helps in stabilizing patella. The main objective was to compare six common rehabilitation exercises (REs) and to identify those which could possibly activate VMO selectively to alleviate PFPS of occupational workers. Ten subjects, having no history of PFPS, performed six REs, namely, straight leg raise with neutral hip position (SLRN), straight leg raise with externally rotated hip position (SLRER), short arc quad with neutral hip position (SAQN), short arc quad with externally rotated hip position (SAQER), medial tibial rotation and hip adduction (HA). REs were compared on the basis of integrated electromyographic activity of VMO and VL. Results demonstrated that VMO activity was more than that of VL during all REs. However, this difference was not statistically significant in any of the six REs. HA produced significantly higher VMO activity than SLRN, SLRER and SAQN. The results provided a wider range of options for selecting apposite REs for treating patients diagnosed with PFPS.

Myoelectric Responses of Lower-Body Muscles Performing Squat and Lunge Exercise Variations Adopting Visual Feedback With a Laser Sensor.

Cross-over study. The squat, single-leg squat, forward lunge, and reverse lunge are fundamental movements often performed in activities of daily living, sports competitions, and sport-specific training. The purpose of this study was to investigate the effect of visual feedback with a laser sensor (VFLS) versus a control condition on the myoelectric activity (surface electromyography [sEMG]) of the vastus medialis oblique (VMO), vastus lateralis, gluteus medius (Gmed), and erector spinae muscles during the performance of several squat variations with bodyweight. Nineteen female college students (20 [2.5]y, 165.3 [10.2]cm, 66.4 [4.1]kg, 2 [1.2]y of resistance training experience) with a background in strength or sports training volunteered to participate in this study. Over 4 separate visits, subjects performed 2 sets of 10 repetitions of a squat variation exercise in random order (ie,squat, single-leg squat, forward lunge, and reverse lunge). The first set of a given squat variation condition was considered a control set, and then after 3-minute rest, a second set was performed with VFLS. Significant decreases in VMO and Gmed myoelectric activity were observed during the VFLS set versus the control set for the forward lunge exercise (P = .03). No differences were observed between the control set and VFLS set in the sEMG normalized signal for all muscles analyzed for the squat and single-leg squat, respectively. However, the sample entropy of the sEMG signal for the erector spinae became more irregular during the VFLS set versus the control set for the squat exercise (P = .01), whereas the Gmed presented a more irregular sEMG signal during the VFLS set versus the control set for the single-leg squat (P = .08). Laser sensor biofeedback may induce significant decreases in VMO and Gmed activation performing forward lunge exercise. Therefore, laser sensor biofeedback may induce a reduction in muscle activity of neutralizers muscles during a few squat bodyweight variations (bilateral, single-leg, forward, and reverse lunge).

Differences in Gluteal and Quadriceps Muscle Activation Among Adults With and Without Lumbar Hyperlordosis.

Many factors have been reported contributing to altering the neuromuscular function of hip and knee muscles. The lumbar hyperlordosis, as a poor posture in some athletes, is thought to be associated with the alteration of the hip and knee muscles activity. To examine the activation of selected hip and knee muscles in athletes with and without lumbar hyperlordosis during functional activities. Case-control study. University laboratory. Twenty-six college male athletes (n = 13 with and n = 13 without lumbar hyperlordosis). Surface electromyography of gluteus maximus (GMAX), gluteus medius (GMED), vastus medialis oblique (VMO), and vastus lateralis (VL) were recorded during single-leg squat and single-leg jump landing (SLJL) tasks. Preactivity; reactivity; and onset muscle during SLJL and eccentric activity during single-leg squat (GMAX, GMED, VMO, and VL along with the ratio of VMO:VL) were assessed. Athletes with lumbar hyperlordosis had a higher level of activity in their GMAX (P = .003), VMO (P = .04), and VL (P = .01) muscles at the moment before foot contact during SLJL. These athletes also demonstrated a higher level of GMAX activity (P = .01) immediately after foot contact. Finally, athletes with lumbar hyperlordosis activated their GMAX sooner (P = .02) during the SLJL. Athletes with normal lumbar lordosis had more activity in their GMED muscle (P = .001) in the descending phase of the single-leg squat task and a higher VMO:VL (P = .01) at the moment after the foot contact during the SLJL. The altered activation of GMAX, GMED, VMO, VL, and VMO:VL can reveal the role of lumbar hyperlordosis in the knee and hip muscles' alteration in athletes. Further study is needed to identify whether these alterations in the hip and knee muscles contribute to injury in athletes.

Differences in Gluteal and Quadriceps Muscle Activation During Weight-Bearing Exercises Between Female Subjects With and Without Patellofemoral Pain.

Glaviano, NR and Saliba, S. Differences in gluteal and quadriceps muscle activation during weight-bearing exercises between female subjects with and without patellofemoral pain. J Strength Cond Res 36(1): 55-62, 2022-Therapeutic exercises targeting gluteal and quadriceps muscles have been previously investigated; however, these studies have only been conducted on healthy individuals. Female subjects with patellofemoral pain (PFP) present with weakness in their gluteal and quadriceps muscles and commonly perform exercises that target these muscles. Therefore, the purpose of this study was to compare lower extremity muscle activity during 5 weight-bearing exercises between female subjects with and without PFP. Twenty female subjects with PFP and 20 healthy female subjects completed 5 weight-bearing tasks: a single-leg squat (SLS), lateral step-down, step-up task, step-down task, and lunge. Surface electromyography of the gluteus medius (GMed), gluteus maximus (GMax), vastus lateralis (VL), and vastus medialis oblique (VMO) were collected. Electromyography activity were normalized to maximal voluntary isometric contractions to represent each gluteal and quadriceps muscle as a percentage. Female subjects with PFP completed a SLS and step-up tasks with less GMed and GMax activity (p < 0.05) compared with those without PFP. Female subjects with PFP also had greater VMO activity (p < 0.05) during the step-up, step down, and lunge and VL activity (p < 0.05) during the step-up and SLS compared with healthy female subjects. Practitioners should be aware that there are differences in gluteal and quadriceps muscle activation between female subjects with and without PFP while performing weight-bearing exercises. These findings should influence both the selection of specific exercises and exercise progression when developing a treatment program that has the intended focus to address gluteal or quadriceps strength deficits in female subjects with PFP.

Backward walking alters vastus medialis oblique/vastus lateralis muscle activity ratio in females with patellofemoral pain syndrome.

This study aims to examine the effect of backward walking (BW) and forward walking (FW) on the myoelectric activity ratio of the vastus medialis oblique (VMO)/vastus lateralis (VL) in females with patellofemoral pain syndrome (PFPS). Between September 2016 and December 2016, a total of 40 female participants (mean age 20.9±1.9 years; range, 19 to 26 years) were included in the study. The participants were divided into two groups as those with unilateral PFPS (PFPS group, n=20) and healthy controls (Control group, n=20). Surface electromyography (EMG) from VMO and VL muscles were collected during FW and BW at a speed of 3 km/h using the Myomonitor® IV EMG system. There was a significant increase in the EMG activities of the VMO and VL muscles during BW compared to FW in PFPS and healthy groups (p=0.001). During BW, the VMO activity of PFPS was significantly higher than the healthy controls (p=0.013) without any significant difference in the VL activity (p=0.916). During FW, there was no significant difference in the VMO and VL activities between the groups (p=0.348 and p=0.705), respectively. The VMO/VL ratio of the PFPS group during BW was significantly higher than the FW ratio (p=0.001) without any significant difference between BW and FW of the healthy group (p=0.841). During BW, the ratio of the PFPS group was significantly higher than compared to the healthy controls (p=0.016) without any significant difference between the groups during FW (p=0.100). Our study results show that BW increases the VMO muscle activation and preserve the ideal VMO/VL ratio in PFPS patients. Therefore, clinicians should consider BW training when developing rehabilitation programs for females with PFPS.

Effects of Squatting with Different Foot Positions on Muscle Activations in Subjects with Genu Varum

Purpose: This study examined the effects of squatting with different foot positions on the muscle activation of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles in subjects with genu varum. Methods: Thirty four subjects participated in this study. Surface electromyography was used to measure the muscle activation of the VMO and VL muscles at the knee angles ($15^{\circ}$, $60^{\circ}$) at three foot positions (internal rotation, neutral position, external rotation) during squatting. Results: Muscle activation differences at different knee angles and foot positions differed significantly between the VMO and VL muscles in both the varus and normal groups. In addition, there was a significant difference according to the knee angles with the foot in external rotation in the VMO and VL ratio. In the varus group, however, the VMO and VL ratio were significantly different only with the feet in internal rotation. In the muscle activation changes of the knee angle differences in the foot position, there was no significant difference in the varus group, but both the VMO and VL muscles were significant different in the normal group. Conclusion: In both groups, regardless of the foot position, muscle activation of the VMO and VL muscles increased with increasing knee flexion angle. In the normal group, when squatting with the feet in external rotation, the VMO and VL muscles activations increased with increasing knee angle. In the varus group, however, the foot position did not affect the VMO or VL muscle activation. This study shows that subjects with genu varum and normal subjects have different VMO and VL muscle activation patterns during squat exercises.

Exercises to Increase Vastus Medialis Oblique Activity: A Review

Exercises to Increase Vastus Medialis Oblique Activity: A Review

Electromyographic activity of the hip and knee muscles during functional tasks in males with and without patellofemoral pain

BackgroundPatellofemoral pain (PFP) is a common overuse injury in physically active individuals. It is characterized by anterior knee, retropatellar, or prepatellar pain associated with activities that increase patellofemoral joint stress such as squatting, stair ascending and descending, running, jumping, prolonged sitting, and kneeling. The etiology of PFP is believed to be multifactorial. Recently, proximal factors have been shown to influence the biomechanics of patellofemoral joint. ObjectiveThe aim of the study was to assess hip and knee muscle activity during single leg stance and single leg squat in males with PFP and a control group without PFP. MethodsEighteen males with PFP (age 24.2 ± 4.4 years) and 18 healthy subjects as controls (age 23.5 ± 3.8 years) were included. We evaluated gluteus medius, gluteus maximus, vastus medialis oblique (VMO), and vastus lateralis (VL) electromyographic (EMG) activity. The muscle activity and reaction time of the proposed muscles were assessed during single leg stance and single leg squat tasks. Independent t-test was used to identify significant differences between PFP and control groups. ResultsNo difference in activity of the gluteus maximus muscle was found in either task (p > 0.5). Significant differences were found in activity of gluteus medius and VMO in both tasks (p < 0.05). VL muscle activity had significant difference in single leg stance (p = 0.01), however, had no significant difference in single leg squat (p = 0.1). No significant differences were found in reaction time of the four studied muscles during both single leg stance and single leg squat (p > 0.5). ConclusionMales with PFP demonstrated altered gluteus medius, VMO, and VL muscle activity during single leg stance and single leg squat compared to healthy subjects. Gluteus maximus activity did not show any changes between groups. Moreover, muscle recruitment patterns were different between PFP and healthy groups.

Preferential strengthening of VMO muscle during selected biomechanical rehabilitative exercises of automotive workers with patellofemoral pain syndrome.

Automotive workers are engaged in occupational activities like engine tune-ups, oil changes, tire rotation, wheel balancing, replacing filters etc. These activities involve prolonged sitting, awkward postures, squatting and kneeling, which are known risk factors to cause patellofemoral pain syndrome (PFPS). This paper aims to investigate the effects of selected biomechanical rehabilitative exercises (BRE) on integrated electromyography (iEMG) activity of vastus medialis oblique (VMO) and vastus lateralis (VL) muscles so as to identify suitable ones to alleviate PFPS of automotive workers. Eleven subjects, automotive workers having PFPS, performed four BRE: (1) short arc quad with neutral hip position (SAQN), (2) short arc quad with externally rotated hip position (SAQER), (3) medial tibial rotation (MTR), and (4) hip adduction (HA). Mean iEMG activity of VMO muscle is more than that of VL muscle during all BRE. However, one way ANOVA with repeated measures indicates that mean iEMG activity of VMO muscle is significantly higher than that of VL muscle during SAQER only. VMO/VL ratio is not significantly different across the four BRE. Results suggest a range of options for choosing appropriate BRE for treating automotive workers with PFPS. However, SAQER may directly be recommended for preferential strengthening of VMO muscle.

Hip position and sex differences in motor unit firing patterns of the vastus medialis and vastus medialis oblique in healthy individuals.

Weakness of the vastus medialis oblique (VMO) has been proposed to explain the high prevalence of knee pain in female subjects. Clinicians commonly use exercises in an attempt to preferentially activate the VMO. Recently, our group found evidence to support clinical theory that the VMO is neurologically distinct from the vastus medialis (VM). However, the ability to voluntarily activate these muscle subsections is still disputed. The aim of this study was to determine if VM and VMO activation varies between sexes and if control of the two muscles is different between rehabilitation exercises. Thirteen men and 13 women performed isometric straight leg raises in two hip positions, neutral hip rotation and 30 degrees lateral hip rotation. Bipolar intramuscular fine-wire electrodes were inserted into the VM and VMO to obtain motor unit recruitment thresholds and initial firing rates at recruitment. Linear mixed models and Tukey post hoc tests were used to assess significant differences in 654 motor units. Women demonstrated faster motor unit firing rate at recruitment, 1.18 ± 0.56 Hz higher than men. Motor units fired 0.47 ± 0.19 Hz faster during neutral hip rotation compared with lateral hip rotation. The VMO motor units were recruited 2.92 ± 1.28% earlier than the VM. All motor units were recruited 3.74 ± 1.27% earlier during neutral hip rotation than lateral hip rotation. Thus the VM and the VMO can be activated differentially, and their motor unit recruitment properties are affected by sex and hip position. NEW & NOTEWORTHY This is the first study to reveal differential activation of the vastus medialis oblique from the vastus medialis in clinical exercise protocols. Our research group used fine-wire electrodes to examine EMG signals of the vastus medialis oblique and vastus medialis to avoid possible cross talk. We also consider the effect of sex on motor unit firing patterns because of higher prevalence of knee pain in women, and yet few studies evaluating the sex differences in neuromuscular control.