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. / Graduation date: 2002

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The purposes of this study were to determine if (1) RE is adversely affected by intense interval bouts of 10 x 400-m, and (2) if there is an interaction effect between RE and recovery duration during the workouts. Twelve highly trained male runners (VO$ rm sb{2max} = 72.5 pm 4.3 ml cdot kg sp{-1} cdot min sp{-1}$) performed 3 interval workouts of 10 x 400-m with a minimum of 4 days between runs. Recovery between repetitions was randomly assigned at 60, 120 or 180 s. The velocity for each 400-m run was determined from a treadmill VO$ rm sb{2max}$ test. The average running velocity was 357.9 $ pm$ 9.0 $ rm m cdot min sp{-1}$. Following the workout, rating of perceived exertion (RPE) increased significantly (p $<$ 0.01) as recovery duration decreased (14.4 at 180 s; 16.1 at 120 s; 17.7 at 60 s recovery). Prior to and following each workout, RE was measured at speeds of 200 and 268 $ rm m cdot min sp{-1}$. Changes from pre to post RE tests in VO$ sb2$, HR, and RER were similar for the three recovery conditions. Averaged across conditions, VO$ sb2$ increased significantiy (p $<$ 0.01) pre to post tests (38.5 to 40.5 $ rm ml cdot kg sp{-1}min sp{-1}$ at 200 $ rm m cdot min sp{-1}$ and from 53.1 to 54.5 $ rm ml cdot kg sp{-1}min sp{-1}$ at 268 $ rm m cdot min sp{-1}$) HR increased (124 to 138; and 151 to 157 bpm) and RER decreased (0.90 to 0.78; and 0.93 to 0.89) at 200 and 268 $ rm m cdot min sp{-1}$, respectively (p $<$ 0.01). This study showed that RE can be perturbed after a high-intensity interval workout and that changes in VO$ sb2$, HR and RER were independent of the recovery duration between repetitions.

The biomechanics of running on level surfaces has been extensively researched, but there is limited knowledge on the biomechanical adaptations of curvilinear running. The purpose of this study was to investigate the electromyographic activity (EMG) of the lower leg muscles while running at two speeds (3.8 and 7.0 m/s) under three conditions (straight-away, flat curve, and banked curve of 11 degrees). Seven male elite track runners participated. Surface electrodes were placed bilaterally on the tibialis anterior (TA), peroneus longus (PL), and gastrocnemius lateralis (GL) muscles. In general, there was greater EMG activity and body lean at the higher speeds for each muscle (p&lt; 0.05); however minimal differences in EMG between the three surface running conditions (except for the second peak of TA). No bi-lateral asymmetry in muscle activation occurred during curved running, whether flat or banked. Future study should address more proximal segment and trunk muscular adaptations.

The purpose of this study was to investigate the dynamic patterns of pressure distribution of curved running with and without banked surfaces at two speeds. Seven male elite runners ran at 3.8 m/s and 7.0 m/s in three different conditions: (1) straight, and along a curve with either (2) no side inclination or (3) an inclination of 19%. Running speed significantly affected peak pressure for plantar foot regions (p&lt;0.05); however, few significant main effects were found for surface running condition or foot side. Center of pressure displacement showed similar patterns in both the medial-lateral and heel to toe excursion regardless the running condition, speed, or foot side. Future study needs to reduce measurement variability as well as to consider other dynamic foot-to-shoe components such as shear stresses.

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Graduation date: 2000

Graduation date: 1995