Graduate Thesis Or Dissertation
 

The effect of a near-maximal effort one-hour run on preferred and optimal stride rate and vertical stiffness

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/08612q973

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  • Experienced runners naturally optimize stride rate in a manner that minimizes oxygen uptake at given running speeds. However, as runners become fatigued, preferred stride rate often decreases. Whether such changes with fatigue occur in parallel with changes in optimal stride rate is unknown. This study's focus was on determining whether experienced runners self-optimize stride rate throughout a near-maximal one-hour run. A secondary focus was to determine if vertical stiffness is associated with decreases in stride rate. Seventeen subjects completed a one-hour near-maximal effort run on a treadmill. After the first five minutes, preferred and optimal stride rates were measured. Ground reaction force data were used to determine preferred stride rate averaged over ten strides. Runners completed five two-minute segments of running at preferred stride rate, 4% and 8% above and below their preferred rate. Oxygen uptake was measured during the second minute of each two-minute segment. Fitting a second-degree polynomial through oxygen uptake versus stride rate data provided a minimum value for oxygen uptake from which optimal stride rate was determined. Fifty minutes into the run, optimal stride rate was measured again. Repeated measures ANOVA showed no difference between preferred and optimal stride rates at the beginning or at the end of the run, but a decrease in optimal stride rate was observed from beginning to end. About half of the subjects decreased preferred and optimal stride rate over the course of the hour run while the other half showed little or no change. Vertical stiffness was measured based upon center of mass vertical displacement and active peak force. Decreases in preferred stride rate over the course of the hour run were expected to be associated with decreases of vertical stiffness. However, the changes in stride rate and vertical stiffness were small; no strong relationship was observed (R²=0.12). Experienced runners have demonstrated the capability to self-optimize stride rate at the beginning and near the end of a one hour run. This ability was observed for runners with substantial shifts of stride rate with fatigue as well as for runners with no change of stride rate with fatigue.
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