Morphological Influences and Energetic Walking Flexibility in Determining Preferred vs. Optimal Speeds: An...

Locomotion is fundamental to the survival of our species. The most comfortable walking speed may be the most efficient for allocating conserved energy for other functions. However, whether preferred (PLS) and optimal (OLS) speeds align in children and adolescents remains unclear. This study aimed to determine whether OLS and PLS are similar in children and adolescents and how anthropometry influences both speeds and their differences.

Eleven females and 17 males (8-17 years of age) were anthropometrically characterized. Five treadmill walking pace tests were used to identify the OLS and U-shaped relationship between energy expenditure and speed (χ² CoT), indicating walking flexibility. Additionally, PLS was self-selected using the same protocol. Differences between OLS and PLS were calculated (mean difference [MD]).

No significant sex differences in anthropometry and speed-related variables were found. OLS, PLS, and their MD in the pooled sample were 3.05 ± 0.13, 2.46 ± 0.51, and 0.60 ± 0.46, respectively, with significant differences between OLS and PLS (p < 0.0001). Femur length (FL), Bi-iliac breadth (BIL), and χ² CoT explained variance in OLS, PLS, and MD, respectively, in the forward stepwise regression models.

Unlike adults, OLS and PLS are not interchangeable in children and adolescents. Participants with lower χ² CoT (greater flexibility) can select comfortable speeds farther from OLS without energetic penalty. Taller individuals with longer femurs and wider hips might have biomechanical advantages in reaching higher OLS and PLS, but this reduces flexibility. These traits, along with the growth and development pattern of Homo sapiens, may reflect evolutionary advantages relevant to interspecies competition.