The Impact Of Bmi On The Cadence-Based Walk-To-Run Transition Threshold

BACKGROUND: The walk-to-run transition (WRT) is characterized by the spontaneous and abrupt change in gait from walking to running. Previous research has identified cadence thresholds of 135 and 140 steps per minute as predictors of the WRT (accuracy >90%). However, there is limited evidence showing whether anthropometric characteristics, such as body mass index (BMI) affect the cadence-based WRT. PURPOSE: To examine potential differences in the cadence-based WRT among BMI groups. METHODS: Forty-four young adults (22 ± 3.5 years, BMI 24.5 ± 4.0 kg/m2, 68% Female) performed 4 × 3-min treadmill bouts at 0.89, 1.34, 1.78 and 2.24 m/s (2, 3, 4, and 5 mph). BMI was categorized as underweight/normal (<25 kg/m2) and overweight/obese (≥25 kg/m2). Cadence was calculated from the directly observed step count per bout (hand tallied steps, verified from video recording) divided by bout duration. The WRT was identified via direct observation of walking vs. running gait during each trial (confirmed from video recording). Receiver operating characteristic (ROC) curve analysis was used to identify the optimal cadence threshold (Youden’s index; sensitivity + specificity - 1) for each BMI group, including 95% confidence intervals (bootstrap n = 20,000 replicates). Subsequently, sensitivity, specificity and accuracy values were obtained for these optimal thresholds using confusion matrices. RESULTS: The optimal cadence-based WRT thresholds varied by BMI group. Specifically, the underweight/normal BMI group had a higher WRT threshold (142 [95% CI: 140, 145] steps/min, sensitivity = 100%, specificity 94.4%, accuracy = 95.7%), compared to the overweight/obese BMI group (138 [95% CI: 137, 143] steps/min, sensitivity = 100%, specificity = 100%, accuracy = 100%). However, these differences were not statistically different (based on overlap of 95% CIs). CONCLUSION: Our analysis revealed an earlier (lower) cadence-based WRT in the overweight/obese BMI group compared to the underweight/normal BMI group. These findings reiterate the importance of considering anthropometric characteristics, not limited to but including BMI when examining gait variables.