Stride Length, Frequency, And Velocity Relationships During Treadmill And Overground Running.

Abstract

Mathematically, running velocity is the product of stride length (SL) and stride frequency (SF), with the relationship between these parameters well documented. With the increase in availability and accuracy of wearable technology, parameters such as SL, SF, and velocity can be easily measured while running outdoors as well as on a treadmill. However, there are no data directly comparing the relationship between these parameters during treadmill running and overground running. PURPOSE: To compare the relationship between SL, SF, and velocity using wearable Global Positioning System (GPS) technology while running at different velocities on the treadmill and overground. METHODS: Subjects (n=10 ; 22.3±2.6yrs; 1.71±.08m; 71.4±15.5kg) completed a total of 14 runs (7 treadmill, 7 overground) with each run at a different velocity. SL, SF, and velocity data were recorded using a GPS watch with footpod (Garmin, Fenix2). Overground runs (approximately 1 min per velocity) were completed first, with treadmill run velocities matching the range of overground velocities. Raw data were exported to excel via a combination of proprietary software (Garmin Connect) and custom software to convert data to excel format. A global 2nd order polynomial lines were fit to the SL vs. velocity as well as to the SF vs. velocity plots for treadmill and overground. Additionally, for each individual subject, SL vs. velocity data sets were fit with a 2nd order polynomial with coefficients averaged across subjects and compared overground vs. treadmill (paired t-tests). RESULTS: The global SL vs. velocity relationship during treadmill running was described as SL=-0.046v2 +0.86v+0.01 (where ‘v’ represents velocity) (R2=0.94) and during overground running SL=-0.11v2+1.04v-0.18 (R2=0.95). The global SF vs. velocity relationship during treadmill running was SF=0.38v2+3.18v+69.8 (R2=0.38) and during overground was SF=3.03v2-5.7v+81.4 (R2=0.68). For the SL vs. velocity relationship, the squared coefficient was greater during overground vs. treadmill (p=0.031) while the linear coefficient (p-0.136) and constant (p=0.260) were not. CONCLUSIONS: The larger SL vs. velocity v2 coefficient for overground running is an indication that subjects used different strategies to achieve faster velocities running overground and on a treadmill.