Mechanical work and muscular efficiency in walking children.

Area of Science:

• Biomechanics
• Human locomotion
• Developmental physiology

Background:

• Understanding age-related changes in walking mechanics is crucial for pediatric development and mobility.
• Previous research has explored energy expenditure but detailed mechanical work analysis across childhood is less understood.

Purpose of the Study:

• To investigate the effects of age and body size on total mechanical work during walking in children (3-12 years) and adults.
• To compare external work (W ext), internal work (W int,k), and double support work (W int,dc) between age groups and across speeds.
• To assess the relationship between mechanical work, metabolic energy cost, and efficiency in developing individuals.

Main Methods:

• Measured total mechanical work per stride (W tot) by summing external work and internal work components.
• Normalized mechanical work (W ext, W int,k) to body mass and per unit distance (J kg(-1) m(-1)).
• Analyzed the relationship between normalized mechanical work, metabolic energy cost, and walking speed in children and adults.

Main Results:

• Normalized external work and internal limb work (W int,k) were higher in children than adults, particularly at higher speeds and in younger children.
• Normalized double support work (W int,dc) exhibited an inverted U-shape with speed, peaking at higher speeds for older subjects.
• Children showed higher metabolic energy costs, but younger children (under 6) had a lower increase in mechanical work relative to energy cost, indicating reduced efficiency.

Conclusions:

• Young children exhibit less efficient positive muscular work production during walking compared to adults.
• Differences in mechanical work, energy cost, and efficiency between children and adults converge and disappear by approximately age 10.
• Age-related maturation significantly influences the biomechanics and energetic cost of locomotion.