The influence of high and low heeled shoes on EMG timing characteristics of the lumbar and hip extensor complex during trunk forward flexion and return task

BACKGROUND: Recent studies suggest that wearing high-heel shoes increases the risk of developing certain musculoskeletal pain conditions. In this study we sought to examine whether heel height alters lumbar and hip extensor muscle timing characteristics during a standardized trunk flexion task. METHODS: Thirty-one young, healthy women (22-27 years; 168.6 +/- 5.1 cm; 57.1 +/- 11.8 kg) participated in this study. Lumbar erector spinae (ES), gluteus maximus (GM), and biceps femoris (BF) electromyographic (EMG) signals were recorded during a trunk flexion task where subjects were instructed to flex their trunk in the sagittal plane and then return to a neutral posture. The task was repeated under three footwear conditions: while wearing no footwear, while wearing shoes with 4-cm heels, and while wearing shoes with 10-cm heels. EMG onset and offset times, as well as EMG duration, were calculated for each muscle and compared across conditions. RESULTS: We observed a significantly earlier onset of the ES EMG activity (1.36 +/- 0.61 vs. 1.56 +/- 0.67 s), and significantly delayed onset of the GM EMG activity (1.72 +/- 0.66 vs. 1.28 +/- 0.58 s) during the flexion phase of movement in the 10-cm heeled compared to the no footwear condition. The GM muscle also exhibited an earlier offset time in the 10-cm heel condition compared to the no footwear condition during the flexion movement (2.57 +/- 0.67 vs. 3.30 +/- 0.61 s) as well as during the return from flexion movement phase (10.87 +/- 0.58 vs. 11.69 +/- 0.65 s). These alterations in timing characteristic resulted in an overall decrease in the EMG duration for the GM muscle during the flexion movement. CONCLUSION: The results of this study suggest that high-heels alter trunk and hip extensor muscle coordination patterns. These findings, when considered in combination with other recent findings on the biomechanical effects of wearing high-heels, raise concern about whether wearing high heels results in abnormal spine loading patterns and increases the risk for developing musculoskeletal injuries.