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When mechanical work meets energetics: Obese versus non-obese children walking
Henrique Bianchi Oliveira1, Rodrigo Gomes da Rosa1, Natalia Andrea Gomeñuka1,2
1Exercise Research Laboratory, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
Insights
Obese children walk at a slower optimal speed than non-obese children, but their walking economy and mechanical efficiency are similar. This suggests that reduced mobility in obese children is linked to a slower preferred walking pace.
Area of Science:
- Pediatric obesity research
- Biomechanics and human movement
- Metabolic cost of locomotion
Background:
- Limited understanding of gait biomechanics and metabolic economy in obese children.
- Previous studies focused on adults and adolescents, leaving a knowledge gap in younger populations.
Purpose of the Study:
- To compare the cost of transport and mechanical work in obese versus non-obese children at various walking speeds.
- To investigate the relationship between gait biomechanics, mechanical work, and walking economy in pediatric obesity.
Main Methods:
- Comparison of metabolic cost of transport, mechanical efficiency, and gait biomechanics (mechanical energy fluctuations) between obese and non-obese children.
- Participants walked on a treadmill at speeds ranging from 1 to 5 km/h.
- Involved 12 obese and 12 non-obese children, matched for age and sex.
Main Results:
- Mechanical efficiency was highest at 3 km/h for both groups.
- Despite greater internal mechanical work in obese children at higher speeds, external and total mechanical work, and mechanical efficiency were similar across all speeds and groups.
- Cost of transport was comparable between obese and non-obese children, but optimal walking speed was reduced by 0.4 km/h in obese children.
Conclusions:
- Walking economy in children is associated with total mechanical work, irrespective of obesity status.
- Reduced functional mobility observed in obese children may be attributed to a slower optimal walking speed compared to their non-obese peers.
New Findings:
What is the central question of this study? The aim was to compare the cost of transport and mechanical work between obese and non-obese children at different walking speeds. What is the main finding and its importance? Our data show that the cost of transport, mechanical efficiency and work are similar and directly mass dependent in obese and non-obese children. The optimal walking speed (most economical walking speed) is reduced in obese children.
Abstract:
Although studies have shown the influence of gait biomechanics on the metabolic economy in obese adults and adolescents, little is known regarding obese children. We compared the metabolic cost of transport, apparent mechanical efficiency and gait biomechanics (assessed by mechanical energy fluctuations) in obese children (n = 12; mean ± SD: 8.6 ± 0.51 years of age, 1.38 ± 0.04 m, 44.6 ± 6.65 kg, 24.1 ± 3.50 kg m-2 ) and age- and sex-matched non-obese children (n = 12, 7.8 ± 0.90 years of age, 1.31 ± 0.08 m, 26.8 ± 2.24 kg, 16.4 ± 1.40 kg m-2 ) while walking at different speeds (from 1 to 5 km h-1 ) on a treadmill. We found that the mechanical efficiency was higher at 3 km h-1 compared with the remaining speeds for both groups (P < 0.05). Although the internal mechanical work has been greater in obese compared with non-obese children at 4 and 5 km h-1 , the external, total mechanical work and the mechanical efficiency remained similar between obese and non-obese children at all speeds. Likewise, the cost of transport was similar in the two groups, although the optimal walking speed was an average of 0.4 km h-1 slower in obese children. Clearly, these results show that the walking economy is associated with the total mechanical work in obese and non-obese children. Finally, the reduced functional mobility in obese children observed in previous studies seems to be associated with a reduction in optimal walking speed in comparison to non-obese children.
