title: 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.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors: Department of Clinical Rehabilitation, University School of Physical Education in Krakow, Al. Jana Pawla II 78, 31-571 Krakow, Poland. Electronic address: anna.mika@awf.krakow.pl.
authors: Anna
authors: A
authors: Mika
authors: Brian C
authors: BC
authors: Clark
authors: Łukasz
authors: Ł
authors: Oleksy
mesh_terms: D000328:Adult; D064131:Back Muscles / Q000502:physiology; D001696:Biomechanical Phenomena / Q000502:physiology; D001827:Body Height / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D008161:Lumbosacral Region / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D012775:Shoes
keywords: Heel shoes; Lumbar spine; Pelvic crossed syndromes; Surface electromyography