John Dixon

The relative timing of VMO and VL in the aetiology of anterior knee pain: a systematic review and meta-analysis

BackgroundAnterior knee pain (AKP) is a common musculoskeletal complaint. It has been suggested that one factor that may contribute to the presence of AKP is a delay in the recruitment of the vastus medialis oblique muscle (VMO) relative to the vastus lateralis muscle (VL). There is however little consensus within the literature regarding the existence or nature of any such delay in the recruitment of the VMO within the AKP population. The purpose of this systematic review and meta-analysis was to examine the relative timing of onset of the VMO and VL in those with AKP in comparison to the asymptomatic population.MethodsThe bibliographic databases AMED, British Nursing Index, CINAHL, EMBASE, Ovid Medline, PEDro, Pubmed and the Cochrane Library were searched for studies comparing the timing of EMG onset of the VMO and VL in those with AKP versus the asymptomatic population. Studies fulfilling the inclusion criteria were independently assessed. Heterogeneity across the studies was measured. A meta-analysis of results was completed for those studies where adequate data was supplied. Where comparable methodologies had been used, results were pooled and analysed.ResultsFourteen studies met the inclusion criteria; one prospective and thirteen observational case control. Eleven compared VMO and VL EMG onset times during voluntary active tasks while four investigated reflex response times. All used convenience sampling and did not state blinding of the assessor. Study methodologies/testing and assessment procedures varied and there was considerable heterogeneity within individual samples. Whilst a trend was identified towards a delay in onset of VMO relative to the VL in the AKP population during both voluntary active tasks and reflex activity, a substantial degree of heterogeneity across the pooled studies was identified (I2 = 69.9–93.4%, p < 0.01).ConclusionFindings are subject to substantial and unexplained heterogeneity. A trend was demonstrated towards a delayed onset of VMO relative to VL in those with AKP in comparison to those without. However not all AKP patients demonstrate a VMO-VL dysfunction, and this is compounded by normal physiological variability in the healthy population. The clinical and therapeutic significance is therefore difficult to assess.

The impact of subacromial impingement syndrome on muscle activity patterns of the shoulder complex: a systematic review of electromyographic studies

BackgroundSubacromial impingement syndrome (SIS) is a commonly reported cause of shoulder pain. The purpose of this study was to systematically review the literature to examine whether a difference in electromyographic (EMG) activity of the shoulder complex exists between people with SIS and healthy controls.MethodsMedline, CINAHL, AMED, EMBASE, and grey literature databases were searched from their inception to November 2008. Inclusion, data extraction and trial quality were assessed in duplicate.ResultsNine studies documented in eleven papers, eight comparing EMG intensity and three comparing EMG onset timing, representing 141 people with SIS and 138 controls were included. Between one and five studies investigated each muscle totalling between 20 and 182 participants. The two highest quality studies of five report a significant increase in EMG intensity in upper trapezius during scaption in subjects with SIS. There was evidence from 2 studies of a delayed activation of lower trapezius in patients with SIS. There was otherwise no evidence of a consistent difference in EMG activity between the shoulders of subjects with painful SIS and healthy controls.ConclusionsA difference may exist in EMG activity within some muscles, in particular upper and lower trapezius, between people with SIS and healthy controls. These muscles may be targets for clinical interventions aiding rehabilitation for people with SIS. These differences should be investigated in a larger, high quality survey and the effects of therapeutically targeting these muscles in a randomised controlled trial.

Effect of shoe heel height on vastus medialis and vastus lateralis electromyographic activity during sit to stand

BackgroundIt has been proposed that high-heeled shoes may contribute to the development and progression of knee pain. However, surprisingly little research has been carried out on how shoe heel height affects muscle activity around the knee joint. The purpose of this study was to investigate the effect of differing heel height on the electromyographic (EMG) activity in vastus medialis (VM) and vastus lateralis (VL) during a sit to stand activity. This was an exploratory study to inform future research.MethodsA repeated measures design was used. Twenty five healthy females carried out a standardised sit to stand activity under 4 conditions; barefoot, and with heel wedges of 1, 3, and 5 cm in height. EMG activity was recorded from VM and VL during the activity. Data were analysed using 1 × 4 repeated measures ANOVA.ResultsAverage rectified EMG activity differed with heel height in both VM (F2.2, 51.7 = 5.24, p < 0.01), and VL (F3, 72 = 5.32, p < 0.01). However the VM: VL EMG ratio was not significantly different between conditions (F3, 72 = 0.61, p = 0.609).ConclusionWe found that as heel height increased, there was an increase in EMG activity in both VM and VL, but no change in the relative EMG intensity of VM and VL as measured by the VM: VL ratio. This showed that no VM: VL imbalance was elicited. This study provides information that will inform future research on how heel height affects muscle activity around the knee joint.

The effect of textured surfaces on postural stability and lower limb muscle activity.

Textured insoles may enhance sensory input on the plantar surfaces of the feet, thereby influencing neuromuscular function. The aim of this study was to investigate whether textured surfaces alter postural stability and lower limb muscle activity during quiet bipedal standing balance with eyes open. Anterior-posterior (AP) and mediolateral (ML) sway variables and the intensity of electromyographic (EMG) activity in eight dominant lower limb muscles were collected synchronously over 30s in 24 young adults under three randomised conditions: control surface (C), texture 1 (T1) and texture 2 (T2). Repeated measures ANOVA showed that the textured surfaces did not significantly affect AP or ML postural sway in comparison to the control condition (p>0.05). Neither did the textured surfaces significantly alter EMG activity in the lower limbs (p>0.05). Under the specific conditions of this study, texture did not affect either postural sway or lower limb muscle activity in static bipedal standing. The results of this study point to three areas of further work including the effect of textured surfaces on postural stability and lower limb muscle activity: (i) in young healthy adults under more vigorous dynamic balance tests, (ii) post-fatigue, and (iii) in older adults presenting age-related deterioration.

Can vastus medialis oblique be preferentially activated? A systematic review of electromyographic studies

Debate exists as to whether the vastus medialis oblique (VMO) can be activated to a greater degree than the vastus lateralis to produce preferential strengthening. This systematic review aims to determine whether preferential activation of VMO can be achieved by altering lower limb joint orientation or muscular co-contraction. A search of pertinent specialist journals and of the electronic databases AMED, CINAHL, the Cochrane database, EMBASE, ovid Medline, Physiotherapy Evidence Database (PEDro), Pubmed, and Zetoc from their inception to February 2008 was undertaken. All English-language clinical papers assessing the electromyographic activity of the human VM against the vastus lateralis (VL) muscles, in a neutral lower limb joint orientation, compared to a different hip, knee, ankle, and foot position; or with the addition of a co-contraction were included. Twenty papers reviewing 387 participants were reviewed. These reported principally that altering lower limb joint orientation or the addition of a co-contraction does not preferentially enhance VMO activity over VL. Nonetheless, the evidence-base presented with a number of significant methodological limitations. Accordingly, well-designed studies evaluating large samples of patients with patellofemoral joint disorders are required, to rectify the present limitations in the evidence-base, and to thoroughly investigate this topic.

AN EXPLORATORY THERMOGRAPHIC INVESTIGATION OF THE EFFECTS OF CONNECTIVE TISSUE MASSAGE ON AUTONOMIC FUNCTION

OBJECTIVE The purpose of this study was to measure effects of connective tissue massage (CTM) on the autonomic nervous system using thermography and physiological measurements. METHODS A repeated-measures design was used. The setting was a university laboratory. Skin temperature at the site of massage, blood pressure, heart rate, and dorsal foot temperature were measured in 8 healthy participants before CTM, immediately after, and at 15-minute intervals for 1 hour. RESULTS The effect of CTM on skin temperature was statistically significant, P = .011. Post hoc pairwise comparisons revealed that the 15-, 30-, 45-, and 60-minute data all differed significantly from the pre-CTM data (all P < .05) and also from the immediately post-CTM data (all P < .05). For diastolic blood pressure, the main analysis of variance showed a statistical significance at P = .062. For other variables, there was no evidence for an effect. CONCLUSIONS Evidence was seen of some effects of CTM on autonomic function. This is information that will increase our knowledge of how CTM affects the autonomic nervous system.

Standing on textured surfaces: effects on standing balance in healthy older adults

BACKGROUND standing on textured surfaces or wearing textured shoe insoles can alter balance performance. This evidence, although inconclusive, offers a potential intervention for improving balance in older adults. This study explored the effect of standing on textured surfaces on double-limb balance in older adults and changes in muscle activity as a possible mechanism of effect. METHODS 50 healthy older adults (29 female, age mean [1SD] 75.1 [5.0]) stood quietly in six conditions-eyes open and closed on two different textured surfaces and a smooth surface control. Mediolateral sway, anterior-posterior sway and centre of pressure velocity were extracted from a force platform and lower limb muscle activity collected using surface electromyography (EMG) over 30 s. RESULTS for mediolateral range with eyes closed, there was a statistically significant effect of texture (F [2, 47] = 3.840, P = 0.033). This was attributed to a 9.2% decrease with Texture 1 compared with Control. No such effects were seen in any other balance variable or lower limb EMG activity for either visual condition. CONCLUSION the results suggest an effect of standing on textured surfaces on mediolateral sway in older adults, supporting further work to develop the therapeutic benefits of textured surfaces as an intervention to improve balance.

Hamstring length in patellofemoral pain syndrome

OBJECTIVES To investigate whether there was a difference in hamstring length between patients with patellofemoral pain syndrome and healthy asymptomatic controls aged 18 to 35 years. DESIGN A cross-sectional observational study measuring hamstring length in patients and asymptomatic controls. SETTING Hospital physiotherapy department. PARTICIPANTS Two groups were tested; one group diagnosed with patellofemoral pain syndrome (mean age 27 years, n=11, six males, five females) and one group of asymptomatic controls (mean age 25 years, n=25, 13 males, 12 females). MAIN OUTCOME MEASURES Hamstring length was evaluated using the passive knee extension method to measure popliteal angle. RESULTS The mean (standard deviation) values for hamstring length were 145.6 (8.7) degrees for patients with patellofemoral pain syndrome and 153.7 (10.1) degrees for the asymptomatic controls. The mean (95% confidence interval) difference between the groups was 8.0 (0.8 to 15.1) degrees , and analysis with a t-test revealed that this was statistically significant (P<0.05). CONCLUSIONS This study found that patients with patellofemoral pain had shorter hamstring muscles than asymptomatic controls. It is not clear whether this is a cause or effect of the condition. Further research is suggested to study how hamstring length changes with rehabilitation, and the relationship with pain.

Altering gait by way of stimulation of the plantar surface of the foot: the immediate effect of wearing textured insoles in older fallers

BackgroundEvidence suggests that textured insoles can alter gait and standing balance by way of enhanced plantar tactile stimulation. However, to date, this has not been explored in older people at risk of falling. This study investigated the immediate effect of wearing textured insoles on gait and double-limb standing balance in older fallers.MethodsThirty older adults >65 years (21 women, mean [SD] age 79.0 [7.1]), with self-reported history of ≥2 falls in the previous year, conducted tests of level-ground walking over 10 m (GAITRite system), and double-limb standing with eyes open and eyes closed over 30 seconds (Kistler force platform) under two conditions: wearing textured insoles (intervention) and smooth (control) insoles in their usual footwear.ResultsWearing textured insoles caused significantly lower gait velocity (P = 0.02), step length (P = 0.04) and stride length (P = 0.03) compared with wearing smooth insoles. No significant differences were found in any of the balance parameters (P > 0.05).ConclusionsA textured insole worn by older adults with a history of falls significantly lowers gait velocity, step length and stride length, suggesting that this population may not have an immediate benefit from this type of intervention. The effects of prolonged wear remain to be investigated.

Footwear interventions: a review of their sensorimotor and mechanical effects on balance performance and gait in older adults.

Footwear interventions, including shoe insoles and foot orthoses, have the capacity to enhance balance control and gait in older people. This review assessed the evidence for the effect of footwear interventions on static and dynamic balance performance and gait in older populations and explored proposed theories for underlying sensorimotor and mechanical mechanisms. We searched the Medline, EMBASE, CINAHL (the Cumulative Index to Nursing and Allied Health Literature), and AMED databases and conducted hand searches. Of 115 relevant articles screened, 14 met the predefined inclusion criteria. Articles were grouped into one of three categories based on balance task (static balance performance during quiet standing, dynamic balance performance during walking, and dynamic balance performance during perturbed standing or functional tasks) and were scored for methodological quality using the Downs and Black Quality Index tool. Footwear interventions seem to alter underlying strategies controlling static and dynamic movement patterns through a combination of sensorimotor and mechanical mechanisms in older people, including those with chronic sensory and musculoskeletal conditions. Evidence shows a consistent trend toward footwear interventions markedly improving lateral stability measures, which are predictors of falls in the elderly. In-depth investigation of neurophysiologic responses to footwear interventions is necessary to help confirm any sensorimotor adaptations. The long-term effects of footwear interventions on balance, gait, and the prevention of falls in older people require further investigation.