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Background: It 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. Methods: A 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 x 4 repeated measures ANOVA. Results: Average 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). Conclusion: We 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. [ABSTRACT FROM AUTHOR]

It was hypothesized that onset of reflex electromyographic (EMG) activity of vastus medialis oblique (VMO) was delayed relative to that of vastus lateralis (VL) in patients with osteoarthritis (OA) of the knee compared to controls. Three subject groups were tested: young asymptomatics ( n =20), mean (±SD) 31.1±7.9 years; older asymptomatics ( n =17), 56.7±8.6 years; and symptomatic OA knee patients, diagnosed by an orthopaedic surgeon ( n =16), 65.9±7.8 years. The patellar tendon reflex latencies of VMO and VL were measured using surface EMG, and the reflex latency difference (RLD) between the two muscles was calculated for each subject. Mean RLD values were 0.75±1.17, 1.05±1.06 and 1.27±0.81 ms for young asymptomatics, older asymptomatics and OA knee patients respectively, indicating that on average VMO was activated after VL in all groups. However, analysis of variance showed that these RLD values were not significantly different between the groups, F (2,50)=1.140, p =0.33. The results demonstrate that the onset of reflex VMO EMG activity relative to VL is not delayed in OA knee patients compared to controls. This has important implications for rehabilitation programmes aimed at developing preferential activation of VMO compared to VL in OA knee. [ABSTRACT FROM AUTHOR]