Electromyographic Activity Ratio Research Articles

Altered muscle recruitment patterns during isometric shoulder abduction in individuals with chronic upper trapezius pain: a cross sectional study

BackgroundUpper trapezius (UT) pain with myofascial trigger points (MTrPs) can affect movement at the glenohumeral joint as well as at the scapulothoracic joint. The investigation of muscle recruitment patterns can discern motor control strategies. The purpose of this study was to compare shoulder muscle recruitment patterns and muscle activity according to various loads between individuals with and without chronic UT pain.MethodsIn this cross-sectional study, twenty-four participants that had UT pain with MTrPs and sex, age, body weight matched 24 controls with no UT pain were recruited. Surface EMG electrodes were attached to the UT, the serratus anterior (SA), the lower trapezius (LT) and the middle deltoid (MD). All participants performed isometric shoulder abduction with a load of 25%, 50%, or 75% of the maximum strength at 60° of shoulder abduction. The EMG activity, the activity ratio (SA/UT, LT/UT, MD/UT), and the relative contribution of each muscle activity were calculated.ResultsMD activity was significantly decreased in the UT pain group compared to that in the control group (p < 0.05). The EMG activity ratio of SA/UT (p < 0.025) and the relative contribution of SA activity to shoulder abduction (p < 0.05) were significantly greater in the UT pain group than in the control group in the 25% loading condition.ConclusionThe results of present study showed that UT pain with MTrPs may increase the relative contribution of SA activity and decrease MD activity at low loads. Altered recruitment patterns of scapular upward rotators can be altered in the proper scapular position, which results in decreased MD activity. Clinicians should consider altered recruitment patterns when managing UT pain.Trial registrationClinical Research Information Service: Clinical Research Information Service (KCT0007370; 08/06/2022).

Isolated rapid eye movement sleep behavior disorder combined with obstructive sleep apnea: response to treatment and its associated factors

Objective/BackgroundWhen isolated rapid eye movement (REM) sleep behavior disorder (iRBD) is combined with obstructive sleep apnea (OSA), the pattern of temporal association between REM without atonia (RWA) and apnea-hypopnea events may be related to improvements in RBD symptoms after positive airway pressure (PAP) treatment. We evaluated the frequency of improvement in RBD symptoms after PAP and the relationship of the degree of co-occurrence between RWA and apnea-hypopnea events to RBD symptom improvement after PAP treatment. Patients/methodsIn an institutional cohort with sleep disorders, 31 patients with video-polysomnography confirmed iRBD and concomitant OSA with an apnea-hypopnea index (AHI) of ≥15/h who received PAP treatment were included. Along with gross video-polysomnography parameters such as AHI and electromyography activity index during REM sleep, a mini-epoch-based parameter apnea–hypopnea–electromyography activity ratio (AH EMG activity ratio) was used to evaluate the co-occurrence between RWA and apnea-hypopnea events. Improvement in RBD symptoms after PAP treatment was designated as a clinical global impression-improvement (CGI-I) score of 0–3 at three-month. ResultsTwenty-three (74.2%) patients exhibited improvement in RBD symptoms after PAP treatment. No patient was taking an antidepressant medication. An AH EMG activity ratio of ≥15% (Odds ratio [OR] 10.146, 95% CI 1.302–79.032, P = 0.027) was significantly associated with clinical improvement after PAP treatment in a regression model adjusted for age, sex, AHI, and electromyography activity index during REM. ConclusionsTreatment of concomitant OSA with PAP can improve symptoms of iRBD. Respiratory events that co-occur with RWA may predict improvement in RBD symptoms after PAP treatment.

Comparison of the VMO/VL EMG Activity Ratio According to Resistance Condition in Partial Lunge Exercise

Comparison of the VMO/VL EMG Activity Ratio According to Resistance Condition in Partial Lunge Exercise

An electromyographic and kinematic study of the scapular stabilisers.

BackgroundThe scapular stabilisers, especially the actions of the force couples around the scapula, have an impact on the biomechanics of the scapula and the orientation of the glenoid.ObjectivesThe aim of our study was to determine both the muscle activity and the correlation between the muscle activity ratio of the lower force couple (the serratus anterior lower fibres and the lower trapezius).MethodsThis was a quantitative cross-sectional study. Muscle activity of the dominant serratus anterior lower fibres and the lower trapezius muscles was collected with surface electromyographic (EMG) sensors and an inertial motion capture system was used to measure the three-dimensional (3D) shoulder flexion in the sagittal plane and abduction in the frontal plane. Graph Pad 5 (Prism, San Diego, CA, USA) was used for the statistical analysis. The confidence level was set at 95% (p < 0.05).ResultsSixteen men and women participated in our study, with a mean (standard deviation) age of 25.4 (± 4.6) years, weight of 80.2 (± 25.1) kg and height of 171.6 (± 10.3) cm. A strong negative correlation was found at the start of the abduction (r = −0.623; p = 0.01) between the muscle activity of the serratus anterior lower fibres and the lower trapezius.ConclusionsThe only significant increase in the mean EMG ratio of serratus anterior lower fibres versus the lower trapezius was present at 60% (from baseline) of abduction (p = 0.03).Clinical implicationsThe EMG activity ratio of serratus anterior lower fibres and lower trapezius remains variable in different movement planes.

Individualized Whole-Body Vibration: Neuromuscular, Biochemical, Muscle Damage and Inflammatory Acute Responses.

Objective. We aimed to investigate the acute residual hormonal, biochemical, and neuromuscular responses to a single session of individualized whole-body vibration (WBV) while maintaining a half-squat position. Methods. Twenty male sport science students voluntarily participated in the present study and were randomly assigned to an individualized WBV group (with the acceleration load determined for each participant) or an isometric group (ISOM). A double-blind, controlled parallel study design with repeated measures was employed. Results. Testosterone and growth hormone increased significantly over time in the WBV group (P < .05 and P < .01, respectively; effect size [ES] ranged from 1.00 to 1.23), whereas cortisol increased over time in both groups (P < .01; ES ranged from 1.04 and 1.36). Interleukin-6 and creatine kinase increased significantly over time only in the WBV group (P < .05; ES = 1.07). The maximal voluntary contraction decreased significantly over time in the ISOM group (P = .019; ES = 0.42), whereas in the WBV group, the decrease did not reach a significant level (P = .05). The ratio of electromyographic activity and power decreased significantly over time in the WBV group (P < .01; ES ranged from 0.57 to 0.72). Conclusion. Individualized WBV increased serum hormonal concentrations, muscle damage, and inflammation to levels similar to those induced by resistance training and hypertrophy exercises.

Correlation between the Q angle and the isokinetic knee strength and muscle activity.

The aim of this study was to investigate the correlation between the Q angle and the isokinetic knee strength and muscle activity. Between March 2016 and April 2016, a total of 50 healthy and right-leg dominant men (mean age 22.3±2.3 years; range, 18 to 27 years) with a Q angle between 5° and 20° and active in sports were included. An isokinetic strength test of the knee joint extensor and flexor muscles at angular velocities of 60, 120, 180, 240, and 300°·s-1 was tested who had a Q angle of 5 to 20° and were active in sports. Surface electromyography (sEMG) was used to determine these muscles' activity levels. Negative correlations were between the Q angle and the average peak torque (APT) in extension (E) and flexion (F), the average power (APE,F) at all angles, the joint angle at the PT (JAPTE) at 240, 180, 120 and 60°·s-1; JAPTF at 300, 240 and 180°·s-1; and the time to PT (TPTF) at 180°·s-1. There was a positive correlation between the Q angle and TPTE (at 60°·s-1). No significant relationship between the Q angle and the level of EMG activity at any angular velocity of the muscles, as well as the VM:VL EMG activity ratio was found. A higher Q angle is associated with decreased isokinetic knee strength, power output, and torque angles. It is thought that possible high Q angle-related knee joint disorders and sports injuries can be avoided by including proper quadriceps strength exercises in exercise prescriptions to be prepared.

Does hip joint positioning affect maximal voluntary contraction in the gluteus maximus, gluteus medius, tensor fasciae latae and sartorius muscles?

BackgroundMinimally invasive total hip arthroplasty (THA) is presumed to provide functional and clinical benefits, whereas in fact the literature reveals that gait and posturographic parameters following THA do not recover values found in the general population. There is a significant disturbance of postural sway in THA patients, regardless of the surgical approach, although with some differences between approaches compared to controls: the anterior and anterolateral minimally invasive approaches seem to be more disruptive of postural parameters than the posterior approach. Electromyographic (EMG) study of the hip muscles involved in surgery [gluteus maximus (GMax), gluteus medius (GMed), tensor fasciae latae (TFL), and sartorius (S)] could shed light, the relevant literature involves discordant methodologies. We developed a methodology to assess EMG activity during maximal voluntary contraction (MVC) of the GMax, GMed, TFL and sartorius muscles as a reference for normalization. A prospective study aimed to assess whether hip joint positioning and the learning curve on an MVC test affect the EMG signal during a maximal voluntary contraction. HypothesisHip positioning and the learning curve on an MVC test affect EMG signal during MVC of GMax, GMed, TFL and S. MethodsThirty young asymptomatic subjects participated in the study. Each performed 8 hip muscle MVCs in various joint positions recorded with surface EMG sensors. Each MVC was performed 3 times in 1 week, with the same schedule every day, controlling for activity levels in the preceding 24h. EMG activity during MVC was expressed as a ratio of EMG activity during unipedal stance. Non-parametric tests were applied. ResultsStatistical analysis showed no difference according to hip position for abductors or flexors in assessing EMG signal during MVC over the 3 sessions. Hip abductors showed no difference between abduction in lateral decubitus with hip straight versus hip flexed: GMax (19.8±13.7 vs. 14.5±7.8, P=0.78), GMed (13.4±9.0 vs. 9.9±6.6, P=0.21) and TFL (69.5±61.7 vs. 65.9±51.3, P=0.50). Flexors showed no difference between hip flexion/abduction/lateral rotation performed in supine or sitting position: TFL (70.6±45.9 vs. 61.6±45.8, P=0.22) and S (101.1±67.9 vs. 72.6±44.6, P=0.21). The most effective tests to assess EMG signal during MVC were for the hip abductors: hip abduction performed in lateral decubitus (36.7% for GMax, 76.7% for GMed), and for hip flexors: hip flexion/abduction/lateral rotation performed in supine decubitus (50% for TFL, 76.7% for S). DiscussionThe study hypothesis was not confirmed, since hip joint positioning and the learning curve on an MVC test did not affect EMG signal during MVC of GMax, GMed, TFL and S muscles. Therefore, a single session and one specific test is enough to assess MVC in hip abductors (abduction in lateral decubitus) and flexors (hip flexion/abduction/lateral rotation in supine position). This method could be applied to assess muscle function after THA, and particularly to compare different approaches. Level of evidenceIII, case-matched study.

Dynamic functional leg alignment in healthy young adults during a stair ascent and descent: an explorative pilot study

Minimally invasive total hip arthroplasty (THA) is presumed to provide functional and clinical benefits, whereas in fact the literature reveals that gait and posturographic parameters following THA do not recover values found in the general population. There is a significant disturbance of postural sway in THA patients, regardless of the surgical approach, although with some differences between approaches compared to controls: the anterior and anterolateral minimally invasive approaches seem to be more disruptive of postural parameters than the posterior approach. Electromyographic (EMG) study of the hip muscles involved in surgery [gluteus maximus (GMax), gluteus medius (GMed), tensor fasciae latae (TFL), and sartorius (S)] could shed light, the relevant literature involves discordant methodologies. We developed a methodology to assess EMG activity during maximal voluntary contraction (MVC) of the GMax, GMed, TFL and sartorius muscles as a reference for normalization. A prospective study aimed to assess whether hip joint positioning and the learning curve on an MVC test affect the EMG signal during a maximal voluntary contraction.Hip positioning and the learning curve on an MVC test affect EMG signal during MVC of GMax, GMed, TFL and S.Thirty young asymptomatic subjects participated in the study. Each performed 8 hip muscle MVCs in various joint positions recorded with surface EMG sensors. Each MVC was performed 3 times in 1 week, with the same schedule every day, controlling for activity levels in the preceding 24 h. EMG activity during MVC was expressed as a ratio of EMG activity during unipedal stance. Non-parametric tests were applied.Statistical analysis showed no difference according to hip position for abductors or flexors in assessing EMG signal during MVC over the 3 sessions. Hip abductors showed no difference between abduction in lateral decubitus with hip straight versus hip flexed: GMax (19.8 ± 13.7 vs. 14.5 ± 7.8, P = 0.78), GMed (13.4 ± 9.0 vs. 9.9 ± 6.6, P = 0.21) and TFL (69.5 ± 61.7 vs. 65.9 ± 51.3, P = 0.50). Flexors showed no difference between hip flexion/abduction/lateral rotation performed in supine or sitting position: TFL (70.6 ± 45.9 vs. 61.6 ± 45.8, P = 0.22) and S (101.1 ± 67.9 vs. 72.6 ± 44.6, P = 0.21). The most effective tests to assess EMG signal during MVC were for the hip abductors: hip abduction performed in lateral decubitus (36.7% for GMax, 76.7% for GMed), and for hip flexors: hip flexion/abduction/lateral rotation performed in supine decubitus (50% for TFL, 76.7% for S).The study hypothesis was not confirmed, since hip joint positioning and the learning curve on an MVC test did not affect EMG signal during MVC of GMax, GMed, TFL and S muscles. Therefore, a single session and one specific test is enough to assess MVC in hip abductors (abduction in lateral decubitus) and flexors (hip flexion/abduction/lateral rotation in supine position). This method could be applied to assess muscle function after THA, and particularly to compare different approaches.III, case-matched study.

슬개대퇴통증증후군 환자의 체중부하운동 유형별 하지 근활성량의 차이

[PURPOSE] The purpose of this study was to investigate analysis of difference of electromyographic activity on rectus femoris(RF), vastus medialis oblique(VMO), vastus lateralis(VL) and gluteus medius(GM) on type of weight-bearing in patients with patellofemoral pain syndorme. [METHODS] The subjects of this study were 13 female patients with patellofemoral pain syndorme 16 case(Right 8 case, Left 8 case) who are 20 - 30 years. The subjects of the study were rectus femoris, vastus medialis oblique, vastus lateralis and gluteus medius attached EMG electrodes to measure the electromyographic activity during weight-bearing exercise. Weight-bearing exercise was conducted half squat(HS), wall half squat(WHS), pillow wall half squat(PWHS) and single lim wall squat(SLWS). The investigator measured and analyzed the factors related to iEMG of muscle and electromyographic activity ratio during four type weight-bearing exercise the experiment collected data through measures of one-way ANOVA with the statistical significance level set at α=.05. [RESULTS] Weight-bearing exercise effective way to increase muscle activation of the VMO during weight-bearing eccentric contraction was shown to SLWS, weight-bearing exercise effective way to increase muscle activation of the GM were to PWHS. Second, weight-bearing exercise effective way to increase muscle activation of the GM during weight-bearing isometric contraction was shown to WHS and PWHS. Third, the weight-bearing concentric contraction of muscles during four kinds of effective weight-bearing exercise to increase muscle activation of specific muscles were not. [CONCLUSIONS] This study the results of the four type weight-bearing exercise according to the class of muscle contraction in the muscle activity with PFPS patients through each muscle was confirmed that the most efficient forms of exercise.

Electromyographic activity after latissimus dorsi transfer: testing of coactivation as a simple tool to assess latissimus dorsi motor learning

The purpose of this study was to investigate coactivation (CoA) testing as a clinical tool to monitor motor learning after latissimus dorsi tendon transfer. We evaluated 20 patients clinically with the American Shoulder and Elbow Surgeons (ASES) and University of California-Los Angeles (UCLA) outcomes scores, visual analog scale, active external rotation (aER), and isometric strength testing in abduction and external rotation. Measurements of aER were performed while the latissimus dorsi was activated in its new function of external rotation with concomitant activation (coactivation) of its native functions (adduction and extension). Bilateral surface electromyographic (EMG) activity was recorded during aER measurements and the strength testing procedure (EMG activity ratio: with/without CoA). Patients were divided into two groups (excellent/good vs fair/poor) according to the results of the ASES and UCLA scores. The mean follow-up was 57.8 ± 25.2 months. Subdivided by clinical scores, the superior outcome group lost aER with CoA, whereas the inferior outcome group gained aER (UCLA score: -2.2° ± 7.4° vs +4.3° ± 4.1°; P = .031). Patients with inferior outcomes in the ASES score showed higher latissimus dorsi EMG activity ratios (P = .027), suggesting an inadequate motor learning process. Isometric strength testing revealed that the latissimus dorsi transfer had significantly greater activity compared with the contralateral side (external rotation, P = .008; abduction, P = .006) but did not have comparable strength (external rotation, P = .017; abduction, P = .009). Patients with inferior clinical results were more likely to be dependent on CoA to gain external rotation. Therefore, CoA testing may be used as a tool to evaluate the status of postoperative motor learning after latissimus dorsi transfer.

몸통 안정화 방법에 따른 몸통근육의 근활성도 비교

Purpose: The purpose of this study was to investigate electromyographic (EMG) activity of deep and superficial trunk muscles during trunk stabilization exercises with and without stabilization maneuvers. Methods: The relative muscle activity ratios and local muscle activities of 25 healthy males were measured using the 8 channel surface EMG system (Myosystem 1400A, Noraxon Inc., U.S.A). The surface EMG activities were tested during performing abdominal hollowing maneuver (AHM), abdominal bracing maneuver (ABM) and no stabilization maneuver (NSM) in random order. Data were analyzed using <TEX>$1{\times}3$</TEX> repeated measures ANOVA. Results: During bridging exercises, the EMG activity ratio of transverse abdominis/internal oblique abdominis relative to rectus abdominis was significantly lower in NSM than in AHM and ABM. During bridging and kneeling exercises, the EMG activity ratio of multifidus relative to erector spinae was significantly higher in AHM than in NSM. Conclusion: The AHM can be clinically used by the physical therapist to activate selectively the trunk muscles when designing selective training programs for patients.

Effect of isometric horizontal abduction on pectoralis major and serratus anterior EMG activity during three exercises in subjects with scapular winging

The aim of this study was to determine the effect of isometric horizontal abduction using Thera-Band during three exercises (forward flexion, scaption, and wall push-up plus) in subjects with scapular winging by investigating the electromyographic (EMG) amplitude of the pectoralis major, serratus anterior and the pectoralis major/serratus anterior activity ratio. Twenty-four males with scapular winging participated in this study. The subjects performed the forward flexion, scaption, and wall push-up plus with and without isometric horizontal abduction using Thera-Band. Surface EMG was used to collect the EMG data of the pectoralis major and serratus anterior during the three exercises. Two-way repeated analyses of variance with two within-subject factors (isometric horizontal abduction condition and exercise type) were used to determine the statistical significance of pectoralis major and serratus anterior EMG activity and the pectoralis major/serratus anterior EMG activity ratio. Pectoralis major EMG activity was significantly lower during forward flexion and wall push-up plus with isometric horizontal abduction, and serratus anterior EMG activity was significantly greater with isometric horizontal abduction. Additionally, the pectoralis major/serratus anterior activity ratio was significantly lower during the forward flexion and wall push-up plus with isometric horizontal abduction. The results of this study suggest that isometric horizontal abduction using Thera-Band can be used as an effective method to facilitate the serratus anterior activity and to reduce excessive pectoralis major activity during exercises for activating serratus anterior.

Does long‐term use of unstable dentures weaken jaw muscles?

Although it is well known that conventional denture wearers have lower maximum bite forces than dentate subjects, no previous studies have compared the strength of the jaw muscles between these two groups. This study compared maximum bite forces, electromyographic (EMG) activity and estimated jaw muscle strength among three groups: (i) 17 edentulous subjects using newly acquired implant-retained overdentures (seven men, 10 women; mean age 60.3 +/- 13.0 years); (ii) 10 age-matched, fully dentate subjects (five men, five women; mean age 57.9 +/- 11.0 years); and (iii) 39 young, fully dentate subjects (19 men, 20 women; mean age 24.4 +/- 3.5 years). Electromyographic activity was recorded from subjects' bilateral superficial masseter and anterior temporalis muscles while they generated maximum voluntary bite forces at the right central incisor, right first premolar and right first molar positions. Jaw muscle strength was estimated as the ratio of average EMG activity for all four muscles to the maximum bite force. At all three bite positions, edentulous subjects produced maximum bite forces that were less than half that of dentate subjects. Edentulous subjects also produced significantly less EMG activity and had significantly lower estimated jaw muscle strength. Our results suggest that weakened jaw muscles are one factor contributing to lower maximum bite forces among users of conventional dentures.

Do asymmetries exist in the trunk muscles and is this influenced by sporting task?

Background: Trunk flexor-extensor asymmetry has been attributed a role in spinal function. However, left-right asymmetry within muscle groups (extensors or flexors) has received little attention. Objective: To examine left-right symmetry within trunk extensors and flexors and the influence of different sporting tasks on this symmetry. Method: Thirty-five subjects (21 males) were recruited and written informed consent obtained; 12 subjects participated in unilateral (UL) sports e.g. tennis, 13 in bilateral (BL) activities e.g. running and 10 controls (C) who were not involved in sport. Isokinetic and isometric trunk flexions and extensions including a fatiguing isometric hold were performed using a Cybex isokinetic dynamometer synchronised with bilateral electromyographic (EMG) recordings from the erector spinae at L4 and rectus abdominis at T10. A ratio of left-right EMG activity was calculated for each set of muscles, to examine asymmetry. Results: No differences were seen in left:right extensor EMG ratios across any of the test protocols. However, the UL group had higher (P < 0.05) left:right flexor EMG ratios than the BL group during pre-fatigue (UL: 1.32 ± 0.15 vs BL: 0.84 ± 0.07) and post-fatigue (UL: 1.30 ± 0.18 vs BL: 0.84 ± 0.07) isometric flexion. Torque data showed that the trunk extensor-flexor ratio was larger (P < 0.05) in the BL group compared to the C in the isokinetic exercises at the 30°/s (BL: 1.27 ± 0.05; C: 1.00 ± 0.06) and at the 90°/s (BL: 1.28 ± 0.05; C: 0.95 ± 0.08), but no differences were seen during isometric testing. Conclusion: This study suggests that participation in different activities such as sports may generate asymmetry in the trunk flexors, the importance of which requires further research.

Biofeedback exercise improved the EMG activity ratio of the medial and lateral vasti muscles in subjects with patellofemoral pain syndrome

Patellofemoral pain syndrome (PFPS) is usually due to weakness of vastus medialis obliquus (VMO) resulting in abnormal patellar tracking. One of the objectives of rehabilitation is to strengthen the VMO so as to counterbalance the vastus lateralis (VL) action during normal activities. This study compared the effects of an 8-week exercise program with and without EMG biofeedback on the relative activations of VMO and VL. Twenty-six subjects with PFPS were randomly allocated into an “exercise” group (Group 1) and a “biofeedback + exercise” group (Group 2). Both groups performed the same exercise program but subjects in Group 2 received real time EMG biofeedback information on the relative activations of VMO and VL during the exercises. After 8 weeks of training, Group 1 had insignificant changes in their VMO/VL EMG ratio ( p = 0.355), whereas Group 2 had significantly greater VMO/VL EMG ratio ( p = 0.017) when performing normal activities throughout a 6-h assessment period. The present result reveals that the incorporation of an EMG biofeedback into a physiotherapy exercise program could facilitate the activation of VMO muscle such that the muscle could be preferentially recruited during daily activities.

Force production of the genioglossus as a function of muscle length in normal humans.

Resting muscle length affects both maximum force production and force maintenance. The strength and force maintenance characteristics of the genioglossus as a function of resting muscle length have not been described. We hypothesized that genioglossus optimum length (L(o)) could be defined in vivo and that the ability of the genioglossus to sustain a given workload would decrease as resting length deviated from L(o). To test this, 11 normal men repeated maximal isometric genioglossus protrusions at different muscle lengths to determine L(o). L(o) was also obtained by using submaximal efforts while simultaneously recording electromyographic activity of the genioglossus, with L(o) defined as the length at which the force-to-genioglossus electromyographic activity ratio was maximum. Both methods provided similar results. Force maintenance was measured at four muscle lengths on separate days. Target efforts representing 60% of each subject's maximum at L(o) and lasting 5 s were performed at 12-s intervals. Time limit of endurance of the genioglossus was defined as the time from trial onset at which 90% of the target could not be maintained for three consecutive efforts. Time limit of endurance was greatest at L(o) and fell to 47.5% at L(o) + 1 cm, 53.8% at L(o) - 1 cm, and 47.4% at L(o) - 1.5 cm. We conclude that L(o) of the genioglossus can be determined in vivo and that force maintenance of the genioglossus is decreased when operating length deviates from L(o).

Effects of Corrective Taping of the Patella on Patients with Patellofemoral Pain

Patellofemoral pain syndrome (PFPS) is a common problem presenting to physiotherapists. One successful approach to treatment involves taping of the patella, which theoretically facilitates the vastus mediallis oblique (VMO) muscle, the main transverse stabiliser of the patella, as well as relieving pain. The purpose of this study was to establish the effect of taping of the patella on VMO and vastus lateralis (VL) EMG activity patterns and patients' perceived pain levels, during maximal isometric quadriceps contractions. Twenty subjects (10 men, 10 women) aged 16–43 years were examined. Subjects reported pain to occur most frequently and of the highest intensity at 0 and 30 of knee flexion before taping. There were significant reductions in pain after the application of tape (p < 0.06) at all joint angles tested. After the application of tape, there was a non-significant increase in VMO EMG activity (P = 0.12) and large variations in the VMO:VL EMG activity ratio. Within the limitations of this study it seems that taping of the patella in patients with PFPS brings about a significant reduction in pain. The results of the study, however, do not support the hypothesis previously forwarded that taping facilitates VMO activity.

Was Sherrington right about co-contractions?

Differences in electromyographic (EMG) activity between brief isometric maximum voluntary contractions under conditions of (1) agonist contraction and (2) agonist-antagonist co-contractions were assessed for elbow flexors (biceps brachii) and elbow extensors (triceps, long head). Expressing maximum EMG co-contraction activity as a ratio of agonist maximum EMG activity of the same muscle yielded EMG ratios consistently below 1.0 ( mean= 0.48for flexion and0.76for extension). Flexor EMG ratios did not co-vary with elbow position but extensor EMG ratios approached 1.0 or sometimes greater at shorter muscle lengths (elbow extension). Findings were in general accord with Sherrington's original proposal of ‘double reciprocal innervation’. Neural circuitry designed to limit full muscle activation during co-contractions may serve to protect the joint against excessive tangential or compressive forces.