Quadriceps muscle contraction causes medial patellofemoral ligament elongation by intermeshed fibers of vastus medialis oblique muscle.

The first aim of this study was to compare the medial patellofemoral length between contracted and relaxed quadriceps muscle and second to assess the importance of the intermeshed vastus medialis oblique fibers. After a priori power analysis (α = 0.05, power [1-ß] = 0.95), 35 healthy males aged 18-30 were prospectively examined with a 3.0-T magnetic resonance imaging (MRI) scanner in 10-15° of knee flexion. Two axial MRI sequences (25 s each) were made with relaxed and contracted quadriceps. Two blinded, independent raters measured twice medial patellofemoral ligament length (curved line) and attachment-to-attachment length (straight line). Mean medial patellofemoral ligament length and attachment-to-attachment length with relaxed quadriceps was: 65.5 mm (SD = 3.7), 59.7 mm (SD = 3.6), and after contraction, it increased to 68.7 mm (SD = 5.3), 61.2 mm (SD = 4.7); p < 0.01 and <0.001, respectively. Intraclass correlation coefficients for intra- and inter-rater reliabilities ranged from 0.55 (moderate) to 0.97 (excellent). Mean medial patellofemoral ligament length elongation after quadriceps contraction was significantly greater (3.2 mm, SD = 3.9) than mean attachment-to-attachment length elongation (1.6 mm, SD = 2.8); p < 0.001. Contraction of quadriceps muscle causes elongation of the medial patellofemoral ligament to the extent greater than the elongation of distance between its attachments. This confirms that medial patellofemoral ligament elongation after quadriceps contraction results not only from movement of its patellar attachment but also directly from intermeshed vastus medialis oblique fibers pulling medial patellofemoral ligament in a different direction creating a bow-like construct in agreement with the "pull-and-guide mechanism" proposed in the literature.

The vastus medialis oblique compensates in current patellar dislocation patients with the increased femoral anteversion.

PURPOSE: The purpose of this study was to investigate whether the vastus medialis oblique (VMO) muscle compensates in patellar dislocation (PD) patients with the increased femoral anteversion angle (FAA). METHODS: Between 2021 and 2024, we included 60 patients with recurrent PD (RPD group). Inclusion criteria were at least two episodes of PD, as well as complete CT scans of the knee and hip. Exclusion criteria included traumatic or habitual dislocation, previous knee surgery, etc. Of these patients, 30 with excessive FAA (≥ 30°) were assigned to the A group, and 30 without excessive FAA (< 30°) to the B group. A control group of 120 patients without patellofemoral disorders was also included (C group). The cross-sectional areas of the VMO and vastus lateralis muscle (VLM) were measured 20 mm above the patella on CT scans, and the VMO/VLM area ratio was calculated. The correlation between FAA and the VMO/VLM ratio was analyzed. RESULTS: The RPD group had a significantly larger FAA (15.0 ± 1.9° vs. 30.1 ± 9.6°, P = 0.040) and a smaller VMO/VLM ratio (4.2 ± 1.5 vs. 3.5 ± 1.0, P = 0.014) compared to the C group. Within the RPD group, the A group had a higher VMO/VLM ratio than the B group (4.0 ± 1.1 vs. 3.0 ± 0.7, P = 0.029). The B group's VMO/VLM ratio was lower than that of the C group (3.0 ± 0.7 vs. 4.2 ± 1.5, P = 0.004). However, there was no significant difference in the VMO/VLM ratio between the A group and the C group. The VMO/VLM ratio showed a moderate positive correlation with FAA in the RPD group, with a correlation coefficient of r = 0.4 (P = 0.012), indicating a statistically significant relationship between the two. CONCLUSION: Patients with recurrent PD showed a smaller VMO/VLM ratio compared to controls. Increased FAA was correlated with compensatory thickening of the VMO and a higher VMO/VLM ratio in PD patients. This suggests that increased FAA may drive biomechanical adaptations in the quadriceps, stabilizing the patella. Clinicians should consider changes in FAA when assessing and treating PD. LEVEL OF EVIDENCE: Level III.

Comparison between the effects of Maitland's mobilization versus its combination with vastus medialis oblique neuromuscular stimulation on two scales (NPRS & WOMAC) in knee osteoarthritis patients.

Background & objectives: Osteoarthritis (OA) is the most common form of arthritis that increases with age affecting the population from the middle age to the elderly. The present study was undertaken to find whether neuromuscular stimulation of vastus medialis oblique (VMO) in combination with Maitland's mobilization and exercises was more effective as compared to Maitland's mobilization with exercises alone in patients with knee OA. Methods: Sixty patients with knee OA were purposively selected and randomly distributed to two groups that received an intervention for eight weeks. Group A patients received Maitland's mobilization in combination with exercises and group B patients received the same intervention as group A in combination with neuromuscular stimulation of VMO muscle. After eight weeks, outcome measures, i.e. Numeric Pain Rating Scale (NPRS) and Western Ontario and McMaster University Osteoarthritis Index (WOMAC) index, were reassessed. Results: Both groups showed significant (P<0.05) within-group improvement in the knee pain levels and stiffness as reflected by NPRS and WOMAC index. Interpretation & conclusions: Patients of both the groups (A and B) were found to be improving significantly in pain and disability, group A patients receiving Maitland's mobilization in combination with exercises were found to get more relief in pain and disability.

Effects of McConnell taping combined with strengthening exercises of vastus medialis oblique in females with patellofemoral pain syndrome.

Objective of the study was to determine the effects of McConnell taping combined with strengthening exercises of vastus medialis oblique muscle in females with Patellofemoral Pain Syndrom. Females with Patellofemoral Pain Syndrome with an age group of 25-45 years having a less than 30/80 score on a Lower Extremity Functional Index (LEFI), anterior knee pain and painful/limited range of motion (ROM) at knee, were included in the study. A total of 51 subjects were randomly assigned into two groups. They were assigned a 30-40 minute per session for 5 days per week over a length of 2 weeks. Numeric Pain Rating Scale, Lower Extremity Functional Index and Goniometry tools were used to assess the measure of interest. These samples only comprised of females with a mean age of 36.04+7.35 years. After 2 weeks, significant improvement was recorded in the Numeric Pain Rating Scale (NPRS) (p<0.001) and Lower Extremity Functional Index (LEFI) (p<0.001). Flexion range of motion of the knee also improved significantly. No statistically significant difference in extension range of the knee was noted in either groups as it was normal at base line.

A study on muscle activity and ratio of the knee extensor depending on the types of squat exercise.

[Purpose] For preventing the patellofemoral pain syndrome, this study aims to suggest a proper squat method, which presents selective muscle activity of Vastus Medialis Oblique and muscle activity ratios of Vastus Medialis Oblique/Vastus Lateralis by applying squat that is a representative weight bearing exercise method in various ways depending on the surface conditions and knee bending angles. [Subjects and Methods] An isometric squat that was accompanied by hip adduction, depending on the surface condition and the knee joint flexion angle, was performed by 24 healthy students. The muscle activity and the ratio of muscle activity were measured. [Results] In a comparison of muscle activity depending on the knee joint flexion angle on a weight-bearing surface, the vastus medialis oblique showed a significant difference at 15° and 60°. Meanwhile, in a comparison of the muscle activity ratio between the vastus medialis oblique and the vastus lateralis depending on the knee joint flexion angle on a weight-bearing surface, significant differences were observed at 15° and 60°. [Conclusion] An efficient squat exercise posture for preventing the patellofemoral pain syndrome is to increase the knee joint bending angle on a stable surface. But it would be efficient for patients with difficulties in bending the knee joint to keep a knee joint bending angle of 15 degrees or less on an unstable surface. It is considered that in future, diverse studies on selective Vastus Medialis Oblique strengthening exercise methods would be needed after applying them to patients with the patellofemoral pain syndrome.

Entrainment of vastus medialis complex activity differs between genders.

INTRODUCTION: That the vastus medialis oblique (VMO) is a functional unit of the vastus medialis (VM) is disputed. Delayed VMO activation predicts patellofemoral pain, which has higher rates in women. METHODS: Single MUs and surface electromyogram (EMG) were collected from the VMO and VM of 9 men and 9 women. Men were tested once; women were tested during 5 menstrual phases. Coherence was assessed for motor unit (MU) firings within and between the VM and VMO using multilevel logistic models to determine statistical significance. RESULTS: Compared with women, men have 741% (MU pairs) and 256% (MU-EMG pairs) greater odds of common drive (0-5 Hz) coherent oscillations. MU pairs from the VMO and the dual VM/VMO complex have 228% and 212% greater odds of coherent oscillations in the beta band (15-35 Hz) compared with VM pairs. CONCLUSIONS: The VM and VMO are neurologically different muscles; control of the VM complex is sexually dimorphic.

Analysis of vastus lateralis and vastus medialis oblique muscle activation during squat exercise with and without a variety of tools in normal adults.

[Purpose] The present study investigated the effects of squat exercises with and without a variety of tools including a gym ball, wedge, and elastic band on the vastus lateralis and vastus medialis oblique muscles. [Subjects and Methods] A total of twenty healthy subjects with no history of neurological, musculoskeletal injury, or pain in the lower extremities were recruited. All subjects performed four types of exercise (conventional squat exercise, squat exercise with a gym ball, squat exercise with a wedge, squat exercise with an elastic band). [Results] There were no significant differences between exercises in comparison of the vastus lateralis muscle activity. In the squat exercise with a wedge, significantly higher activity of the vastus medialis oblique muscle was found compared with in the squat exercise with an elastic band. [Conclusion] The present study suggests that the conventional squat exercise can be one of the useful interventions for patients with patellofemoral pain syndrome.

Effects of squats accompanied by hip joint adduction on the selective activity of the vastus medialis oblique.

[Purpose] This study evaluated the effective selective activation method of the vastus medialis oblique for knee joint stabilization in patients with patellofemoral pain syndrome. [Subjects and Methods] Fifteen healthy college students (9 males, 6 females); mean age, height, and weight: 22.2 years, 167.8 cm, and 61.4 kg, respectively) participated. The knee angle was held at 60°. Muscle activities were measured once each during an ordinary squat and a squat accompanied by hip joint adduction. The muscle activities of the vastus medialis oblique and vastus lateralis were measured by electromyography for five seconds while maintaining 60° knee flexion. Electromyography signals were obtained at a sampling rate of 1,000 Hz and band pass filtering at 20-50 Hz. The obtained raw root mean square was divided by the maximal voluntary isometric contraction and expressed as a percentage. The selective activity of the vastus medialis oblique was assessed according to the muscle activity ratio of the vastus medialis oblique to the vastus lateralis. [Results] The activity ratio of the vastus medialis oblique was higher during a squat with hip joint adduction than without. [Conclusion] A squat accompanied by hip joint adduction is effective for the selective activation of the vastus medialis oblique.

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.

SMOC approach for total knee arthroplasty in valgus knees.

OBJECTIVE: This study was performed to compare clinical outcomes among patients with valgus knees undergoing total knee arthroplasty via the medial parapatellar approach and the subvastus with minimal oblique cut approach. METHODS: A total of 232 patients (246 knees) undergoing total knee arthroplasty between December 2014 and December 2016 were retrospectively included in the investigation. The study population consisted of 120 patients (128 knees; 32 men and 88 women) with a mean age of 62.43 ± 8.12 years treated via the medial parapatellar approach, and 112 patients (118 knees; 30 men and 82 women with a mean age of 63.15 ± 7.83 years) treated via the subvastus with minimal oblique cut approach. Nine preoperative parameters (number of patients, sex, age, body mass index, number of knees, valgus angle, visual analogue scale score, range of motion, Hospital for Special Surgery score), five perioperative parameters (operative time, amount of drainage, Visual analogue scale score at 24 h after the operation, time to straight leg raising, radiological alignment), and two postoperative parameters (range of motion, Hospital for Special Surgery score) were assessed at 1 day, 1 week, 6 weeks, 8 weeks and 1 year after the operation, along with postoperative complications. RESULTS: There were no significant differences in the nine preoperative parameters between the two groups. The subvastus with minimal oblique cut group had a longer operative time, while the parapatellar approach group showed more drainage and a higher mean Visual analogue scale score. Compared to the medial parapatellar group, the subvastus with minimal oblique cut group had a shorter time to straight leg raising. There were no differences in radiological alignment between the two groups. The groups showed similar range of motion and Hospital for Special Surgery scores at 8 weeks and 1 year, but both were higher in the subvastus with minimal oblique cut group at 1 day, 1 week and 6 weeks. During postoperative follow-up, postoperative subluxation of the patella occurred in five cases in the medial parapatellar group. Neither group showed any instability, recurrent valgus deformity or radiographic loosening. CONCLUSION: The subvastus with minimal oblique cut approach provides excellent early recovery for total knee arthroplasty of valgus knees with no increase in complications.

Differences in Muscle Fatigability of Vastus Medialis between Sexes Using Surface Electromyographic Power Spectral Analysis in Healthy Adults.

Objectives: With a relatively high percentage of type I fibers in the vastus medialis (VM), its fatigability may be more sensitive to the effects of muscle activity in the quadriceps. However, sex-related differences in the muscle fatigability of the VM remain unknown. The purpose of the present study was to assess the differences in fatigability of the VM between healthy adult men and women. Methods: Surface electromyographic (EMG) activities of VM oblique (VMO) and VM long (VML) were recorded during sustained isometric contraction on a leg press machine. The results of EMG power spectral analysis were compared between healthy adult men and women. The decline in the median frequency (MF), defined as MF slope, was calculated using spectrum analysis after fast Fourier transform of the raw EMG signals of VMO and VML. Results: The endurance time and the MF slopes of the VMO and VML were significantly longer and lower, respectively, in women than in men. The present results demonstrated that both VMO and VML are more fatigue-resistant in women than in men. Conclusions: Understanding the sex differences in fatigability could help to design more effective exercise regimens for VMO and VML in healthy individuals. A similar approach should be considered when prescribing practical exercise regimens for patients with muscle atrophy.

The Effect of Self-Myofascial Release on the Pennation Angle of the Vastus Medialis Oblique and the Vastus Lateralis in Athletic Male Individuals: An Ultrasound Investigation.

Background: Maintenance of patellar stability requires a balance between the vastus medialis oblique (VMO) and the vastus lateralis (VL). The imbalance between these muscles is thought to be implicated in the etiology of patellofemoral pain (PFP). Where there is hypertrophy of the VL in PFP patients, self-myofascial release (SMR) may be utilized for its management. However, there is no current evidence regarding SMR and its effects on VMO and VL architecture. The aim of this study, therefore, was to use ultrasound to gain further understanding of the effects of a program of SMR on the fiber angles of the VMO and VL. Hypothesis: There will be a significant decrease in the pennation angles of the VMO and VL after seven weeks of SMR using a foam roller. Study Design: Cohort Study. Methods: Twenty-five young, athletic, male participants were recruited to use a foam roller, along the full length of both anterior thighs, three times weekly, on three separate days, for seven weeks. Ultrasound was used to determine the initial and final VMO and VL pennation angles on both limbs. One eligible participant was chosen as an intra-rater control and did not partake in the SMR regimen. Results: There was a statistically significant (p < 0.001) decrease in the pennation angles of the VMO and VL after the SMR regime. Mean combined right and left VL angle change was -6.65° (-18% mean change) and the mean combined right and left VMO angle change was -7.65° (-11.5% mean change). A weak negative correlation was found between initial VMO fiber angle and the angle change (Rsquared = -0.21), as well as moderate negative correlation for the VL (Rsquared = -0.51). Conclusion: A program of SMR on the anterior thighs of young, asymptomatic males resulted in changes to the fiber angles of both the VMO and VL. There was a significant decrease in pennation angle after seven weeks of SMR using a foam roller.

Change of the cross-sectional area of vastus medialis oblique in patients with recurrent patellar dislocation treated by tibial tubercle transfer combined with medial patellofemoral ligament reconstruction on axial CT.

PURPOSE: To investigate the change of the cross-sectional area (CSA) of vastus medialis oblique (VMO) in patients with recurrent patellar dislocation (RPD) treated by tibial tubercle transfer combined with medial patellofemoral ligament (MPFL) reconstruction by imaging methods, and to guide clinical treatment and rehabilitation. METHODS: From October 2015 to March 2022, 23 patients with RPD who underwent tibial tubercle transfer combined with MPFL reconstruction were retrospectively enrolled. All patients were assessed by CT in the supine position with the knee fully extended and the quadriceps relaxed. The CSA of VMO and the ratio of CSA of VMO to body weight (CSA/BW) were measured at the upper pole of the patella, 5 mm above the upper pole of the patella and 5 mm below the upper pole of patella. The differences of measured parameters were compared before surgery and at follow-up, including CSA of VMO and CSA/BW. Test level α = 0.05. RESULTS: The tibial tubercle-trochlear groove (TT-TG) distance was significantly reduced at follow-up compared with that before surgery (27.91 ± 1.95 mm vs 12.33 ± 1.07 mm, P < 0.001). The CSA of VMO was significantly increased at follow-up compared with that before surgery at 5 mm below the upper pole of the patella (473.06 ± 106.32 mm2 vs 562.97 ± 157.90 mm2, P < 0.001), at the upper pole of the patella (641.23 ± 188.45 mm2 vs 700.23 ± 177.55 mm2, P = 0.029), and at 5 mm above the upper pole of the patella (788.25 ± 238.62 mm2 vs 849.79 ± 180.84 mm2, P = 0.018). The CSA/BW was significantly increased at follow-up compared with that before surgery at 5 mm below the upper pole of the patella (7.83 ± 2.52 mm2/kg vs 9.22 ± 3.54 mm2/kg, P < 0.001), at the upper pole of the patella (10.48 ± 3.62 mm2/kg vs 11.42 ± 4.14 mm2/kg, P = 0.020), and at 5 mm above the upper pole of the patella (12.86 ± 4.65 mm2/kg vs 13.68 ± 3.86 mm2/kg, P = 0.017). CONCLUSION: After tibial tubercle transfer combined with MPFL reconstruction, CSA of VMO increased in patients with RPD, which will help to enhance patellar stability and reduce recurrence.

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.

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

BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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: 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. CONCLUSIONS: The results provided a wider range of options for selecting apposite REs for treating patients diagnosed with PFPS.

Acute Effects of Open Kinetic Chain Exercise Versus Those of Closed Kinetic Chain Exercise on Quadriceps Muscle Thickness in Healthy Adults.

This study aimed to compare immediate changes in the thickness of the rectus femoris (RF), vastus intermedius (VI), vastus lateralis (VL), vastus medialis (VM), and vastus medialis oblique (VMO) muscles after open kinetic chain exercise (OKCE) and closed kinetic chain exercise (CKCE) and identify the effect of both exercise types on each quadricep muscle for early rehabilitation to prevent knee joint injury. Twenty-six healthy participants (13 males and 13 females) were randomly divided into the OKCE (n = 13) and CKCE (n = 13) groups. The thickness of their quadriceps muscles was measured using a portable ultrasonic imaging device before and after exercise in the sequence RF, VI, VL, VM, and VMO. A two-way repeated measures analysis of variance was used to compare the thickness of each component of the quadriceps muscles between the two groups. The thickness of the RF, VL, VM, and VMO muscles increased after OKCE, and the thickness of the VI muscle showed the greatest increase with a medium-large effect size (F = 8.52, p = 0.01, and d = 0.53). The thickness of the VI, VL, VM, and VMO muscles increased after CKCE, and the VMO muscle had the largest effect size (F = 11.71, p = 0.00, and d = 1.02). These results indicate that the thickness of the quadriceps muscles can be selectively improved depending on the type of exercise.

Traumatic bilateral medial patellar instability in a 15-year-old girl.

Introduction: Patellar dislocation encompasses the 2-3% of the knee joint injuries, and lateral patellar luxation is by far more common than the medial one. Medial patellar dislocation is described only by few reports and generally as a consequence of previous surgeries. The purpose of this case report is to describe the surgical management of a rare case of traumatic bilateral medial patellar dislocation in a 15-year-old girl with no previous patellofemoral surgeries. Case Report: The patient underwent a traumatic medial patellar dislocation on the left knee, and 18 months later also on the right one. In both cases, the first proposed treatment was a conservative therapy, encompassing the use of a brace and muscular imbalance correction. After a 6-month period, the patient still referred to the persistent sensation of "giving away," so surgery was advised. The surgical operation consisted of an open medial retinacular release with complete dissection of the hypertrophic medial patellofemoral ligament and a transfer of the vastus medialis oblique to the superior border of the patella. Seven years after surgery, the patient declared to be satisfied with the procedure, referring only slight difficulty in squatting, jumping, and running. So far, no further episodes of dislocation occurred. Conclusions: The present case report showed the favorable result of surgical correction of a unique case of bilateral non-iatrogenic medial patellar luxation, in the absence of any underlying bony-structural abnormality. No other papers dealing with medial traumatic bilateral patellar dislocation are found in current literature.

Differences in myoelectric manifestations of fatigue during isometric muscle actions.

INTRODUCTION: Muscle fatigue has been studied for a long time with the use of a wide variety of exercise models, protocols and assessment methods, among which surface electromyography (sEMG) is most commonly used. The main sEMG parameters (amplitude and frequency) are prevalently used to evaluate the level of muscle fatigue in static and dynamic contractions. OBJECTIVE: The purpose of this study is to determine and compare 2 separate indices: IF1 basis of the sEMG signal amplitude analysis and IF2 basis of the sEMG median frequency analysis, related to muscles fatigue during an isometric contraction. MATERIAL AND METHODS: The study was performed on 60 professional runners divided into 2 equal groups. The first group comprised sprinters, competing in short distance track and field events (100 and 200 meters). The second group consisted of middle-distance runners, competing in middle-distance track and field events (800 and 1,500 meters). The electrical activity of the VMO muscles of the right and left lower limbs was recorded simultaneously during isometric activity in a squatting position. The sEMG data was used to determine and compare IF1 and IF2 indices. RESULTS: During isometric measurement, sprinters presented a much more significant increase in the mean amplitude of sEMG signal in comparison to middle-distance runners (mean IF1 difference: 0.228; p=0.007). Analysis of the median frequency did not show significant differences between the 2 groups (mean IF2 difference: 0.037; p=0.12). CONCLUSIONS: Change in sEMG amplitude during isometric exercise may be related to muscles fatigue. The use of fatigue indices, based on sEMG amplitude, as an objective indicator of the efficacy of an endurance training programme for sportsmen requires further research.

Characterastics of muscle architectural parameters for early knee osteoarthritis in middle-aged and elderly women / 中国康复理论与实践

ObjectiveTo observe the architectural parameter changes of the muscles around the knee in middle-aged and elderly women with early knee osteoarthritis (KOA) by musculoskeletal ultrasound, and to clarify the indicators of muscles that affect early KOA. MethodsFrom January to August, 2022, 20 healthy middle-aged and elderly healthy women (controls) and 20 middle-aged and elderly women with unilateral early KOA (KOA group) were recruited through Beijing Bo'ai Hospital, to measure muscle thickness of the popliteus muscle, the muscle thickness and the pennation angle of the quadriceps, as rectus femoris, vastus intermedius, vastus lateralis, vastus medialis longus and vastus medialis oblique. ResultsCompared with the healthy limb of KOA group, and the controls, the muscle thickness of vastus medialis longus, vastus medialis oblique and popliteus muscle of the affected limb of KOA group became thinner (t > 2.133, P < 0.05); the proportion of thickness of vastus medialis oblique to thickness of vastus lateralis became smaller (t > 3.660, P < 0.05). The pennation angle was smaller in the affected limb of KOA group than in the matched dominant side of the controls (t = 3.101, P < 0.05). Logistic regression analysis showed that the muscle thickness of vastus medialis oblique (OR = 0.235, 95%CI 0.068 to 0.805, P = 0.021) and popliteus muscle (OR = 0.387, 95%CI 0.152 to 0.980, P = 0.045) were related to the onset of early KOA. ConclusionThe thickness of vastus medialis longus, vastus medialis oblique and popliteus muscle decrease, and the balance of the strength of vastus medialis oblique and vastus lateralis weakens in the affected limbs of the middle-aged and elderly women with early KOA. The thickness of vastus medialis oblique and popliteus muscle are protective factors for onset of KOA.

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

BACKGROUND: 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). OBJECTIVE: 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. METHODS: 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). RESULTS: 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. CONCLUSIONS: 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.