Document Detail

Preferred and optimal stride frequency, stiffness and economy: changes with fatigue during a 1-h high-intensity run.
MedLine Citation:
PMID:  17602239     Owner:  NLM     Status:  MEDLINE    
Metabolic cost of submaximal running at constant speed is influenced by various factors including fatigue and kinematic characteristics. Metabolic costs typically drift upwards during extended running while stride characteristics often shift away from initial. When non-fatigued, experienced runners naturally optimize stride frequency in a manner that minimizes oxygen uptake. An initial objective was to determine whether runners demonstrate a similar self-optimizing capability when fatigued where stride characteristics have perhaps shifted away from the initial state. A secondary objective involved measurement of vertical and leg stiffness characteristics as a potential explanation for frequency changes with fatigue. We hypothesized that runners decrease stride frequency and stiffness with fatigue while optimizing these characteristics to minimize metabolic cost. Sixteen experienced runners completed a near maximal effort 1-h treadmill run at a constant speed. Preferred and optimal stride frequencies (PSF and OSF) were measured near the beginning and end of the hour run using frequencies +/-4 and +/-8% around PSF. From vertical force data recorded throughout the run, leg and vertical stiffness were determined. As expected, oxygen uptake significantly increased during the run from 45.9 to 47.4 ml kg(-1) min(-1) (P = 0.004). There was no difference between preferred and optimal stride frequencies at the beginning or the end of running (P = 0.978), however both PSF and OSF significantly decreased from 1.45 to 1.43 Hz (P = 0.026). All runners self-optimized stride frequency at the beginning and end of one-hour of running despite changes of optimal stride frequency. Stiffness and stride frequency changes were subject specific with some runners exhibiting little to no change. No clear relationship of frequency or stiffness changes to economy was found.
Iain Hunter; Gerald A Smith
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Publication Detail:
Type:  Journal Article     Date:  2007-06-30
Journal Detail:
Title:  European journal of applied physiology     Volume:  100     ISSN:  1439-6319     ISO Abbreviation:  Eur. J. Appl. Physiol.     Publication Date:  2007 Aug 
Date Detail:
Created Date:  2007-07-30     Completed Date:  2008-01-24     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100954790     Medline TA:  Eur J Appl Physiol     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  653-61     Citation Subset:  IM    
Department of Exercise Sciences, Brigham Young University, Provo, UT, USA.
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MeSH Terms
Body Weight / physiology
Energy Metabolism / physiology*
Leg / physiology
Linear Models
Muscle Fatigue / physiology*
Oxygen Consumption / physiology
Running / physiology*

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