Developmental Plasticity of Locomoter Eonomy in Response to Chronic Limb Loading in An Avian Bipedal Model
Open Access
- Author:
- Johnson, Talayah
- Graduate Program:
- Kinesiology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 15, 2021
- Committee Members:
- Jonas Rubenson, Thesis Advisor/Co-Advisor
Stephen Piazza, Committee Member
Robert L Sainburg, Committee Member
Jonathan Bates Dingwell, Program Head/Chair - Keywords:
- locomotor economy
energetics
plasticity
limb load - Abstract:
- Over an evolutionary time scale, natural selection has resulted in specializations for animal locomotor economy (Alexander, 2003). Whether adaptations in locomotor economy (metabolic cost) occur across an individual’s life span, however, remains less clear. To understand better the scope of developmental plasticity of locomotor economy, we adopted a bipedal model (guinea fowl) that permitted drastic alteration of musculoskeletal loads across the growth span. At two weeks of age, animals were randomly assigned to a control group (CON, n=6) or a limb-loaded experimental group (LL, n=6). A lead strip equalling, on average, 4.0% of the individual's weekly measured body mass was chronically applied to the right leg of the LL group throughout growth (with mass adjusted weekly). Metabolic power was measured during standing and during treadmill walking (0.5 ms-1) using a flow-through metabolic chamber system. Metabolic power was measured in the habitual conditions (unloaded in CON; limb-loaded in LL), as well as in their novel condition (matched limb load in CON; unloaded in LL). Lastly, we used an interlimb design to investigate load carrying economy on the habitually loaded (right) leg versus the habitually unloaded (left) leg in the LL group. The LL group carried the added limb load 24% more economically compared to the CON group (p < 0.05). Surprisingly, the large addition in habitual limb mass in LL did not result in a difference in walking metabolic power compared to unloaded walking in the CON group. There was also a significant lower metabolic cost (p = 0.05) associated with carrying additional mass on the habitually loaded (right) leg compared to the habitually unloaded (left) leg. Nevertheless, contrary to our hypothesis, the CON group did not have a lower metabolic cost than the LL group in the unloaded condition. Overall, our results support our hypothesis that locomotor economy responds plastically to altered amounts of load (functional demand) during growth and is tuned to the habitual loading environment. The exception was the unloaded group comparison. The musculoskeletal factors leading to altered locomotor economy are currently being explored. Here we provide new evidence that locomotor economy can be altered based on the loading history during growth. These data have important implications for understanding the long-term effects of childhood activity and inactivity.