Biology subjects

Dewolf, A. H.

Publications and source records attributed to Dewolf, A. H..

2 recordsLinked to original sources

bioRxiv2024

The Role of Physical Activity in Mitigating Age-Related Changes in the Neuromuscular Control of Gait

Exercise is known to induce several neural and muscular adaptations, such as increased muscle mass and functional capacity in older adults. In this study, we investigated its impact on the neuromuscular control of gait among young and older adults, divided into two groups: more active (young: n=15; 5185 {+/-} 1471 MET-min/week; old: n=14; 6481 {+/-} 4846 MET-min/week) and less active participants (young: n=14; 1265 {+/-} 965 MET-min/week; old: n=14; 1473 {+/-} 859 MET-min/week). Maximal isometric tests of ankle and knee extension revealed a reduction in force among older adults, with differences associated with the level of physical activity at the ankle level. Gait mechanics revealed no significant differences between young adults and the more active older adults. In contrast, less active older adults exhibited shorter steps, higher mechanical cost, and greater collision at heel strike. These changes cannot be attributed solely to reductions in muscle strength. Instead, they are likely the result of modifications in neuromuscular control and mechanical properties of muscles in less active older adults. Specifically, wider activation (and greater coactivation) of lumbar and sacral motor pools as well as a different timing of activation were observed. Also, their muscle-tendon stiffness was reduced. In conclusion, our findings highlight that the age-related decline in gait efficiency is exacerbated by a sedentary lifestyle. Even modest increases in physical activity appear to preserve neuromuscular control and improve walking performance. This suggests that interventions aiming to enhance physical activity levels could mitigate age-related declines in gait mechanics.

neuroscience↗

bioRxiv2024

Locomotion Efficiency of Elephants: Mechanical work and energetics

The size scaling of energy expenditure during locomotion has long puzzled researchers seeking biological invariants. Existing data, most of it from animals smaller than 200 kg, show that the mass specific mechanical work of locomotion is nearly independent of size, yet the metabolic cost of locomotion decreases with increasing size. Major questions remain concerning heavier animals: extrapolating mechanical work and metabolic cost to animals the size of an elephant comes to the uncomfortable conclusion that elephants would produce more energy than they would consume. Our study addresses this longstanding size-scaling conundrum by focusing on the locomotion mechanics and energetics of elephants, the largest extant land animals. In this study, the work required to move the limbs relative to the centre of mass of the whole body (COM) was measured in 27 Asian elephants (872-4000 kg). The total mechanical work was calculated by adding the external work required to maintain the movements the COM. Our investigation challenges the belief that mass-specific mechanical work of locomotion is independent of size. Furthermore, our study unveils a surprising aspect of elephant locomotion--the substantial fraction of total mechanical work dedicated to limb swinging. At high speeds, elephants allocate [~]75% of their work to limb swinging. Also, by quantifying the metabolic cost and mechanical work, we provide the first estimation of the efficiency of converting metabolic energy into mechanical work in elephants. Elephants exhibit an efficiency of at best 45%, which is similar to that in other large mammals such as horses and humans. This study not only addresses a significant gap in our understanding of size scaling in locomotion but also opens new avenues for exploring the evolution of energy expenditure across diverse animal sizes.

physiology↗