title: Altering muscle activity in the lower extremities by running with different shoes.
abstract: OBJECTIVE
  To provide evidence that lower-extremity muscle activity during running is tuned in response to the loading rate of the impact forces at heel-strike.
  
  
  METHODS
  Six runners ran two 30-min trials per week for 4 wk. The trials tested two shoes which differed only in the material hardness of the midsole. The shoes were tested in a randomized sequence. Bipolar surface EMG was recorded from the muscles of the rectus femoris, biceps femoris, medial gastrocnemius, and tibialis anterior. EMG was resolved into time-frequency space using wavelet techniques. EMG was analyzed for the 150 ms time window immediately before heel-strike.
  
  
  RESULTS
  The intensity of the EMG and the ratio of the EMG intensity between high and low frequency components both showed significant changes between shoes, subjects, and muscles. Additionally, the intensity ratio showed a significant change over the course of each 30-min run.
  
  
  CONCLUSIONS
  Lower-extremity muscle activity used to tune the muscles for the impact task can be altered by changing the material hardness of the shoe. The changes in the EMG frequency ratio suggest that muscle fiber-type recruitment patterns can also be altered by the choice of midsole material.
authors.affiliation: Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, T2N 1N4, Canada. wakeling@kin.ucalgary.ca
authors.forename: James M
authors.initials: JM
authors.lastname: Wakeling
authors.forename: Silvia A
authors.initials: SA
authors.lastname: Pascual
authors.forename: Benno M
authors.initials: BM
authors.lastname: Nigg
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D012420:Running / Q000502:physiology*; D012775:Shoes