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Boebinger S, Payne A, Martino G, Kerr K, Mirdamadi J, McKay JL, Borich M, Ting L. Precise cortical contributions to sensorimotor feedback control during reactive balance. PLoS Comput Biol 2024; 20:e1011562. [PMID: 38630803 PMCID: PMC11057980 DOI: 10.1371/journal.pcbi.1011562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 04/29/2024] [Accepted: 03/25/2024] [Indexed: 04/19/2024] Open
Abstract
The role of the cortex in shaping automatic whole-body motor behaviors such as walking and balance is poorly understood. Gait and balance are typically mediated through subcortical circuits, with the cortex becoming engaged as needed on an individual basis by task difficulty and complexity. However, we lack a mechanistic understanding of how increased cortical contribution to whole-body movements shapes motor output. Here we use reactive balance recovery as a paradigm to identify relationships between hierarchical control mechanisms and their engagement across balance tasks of increasing difficulty in young adults. We hypothesize that parallel sensorimotor feedback loops engaging subcortical and cortical circuits contribute to balance-correcting muscle activity, and that the involvement of cortical circuits increases with balance challenge. We decomposed balance-correcting muscle activity based on hypothesized subcortically- and cortically-mediated feedback components driven by similar sensory information, but with different loop delays. The initial balance-correcting muscle activity was engaged at all levels of balance difficulty. Its onset latency was consistent with subcortical sensorimotor loops observed in the lower limb. An even later, presumed, cortically-mediated burst of muscle activity became additionally engaged as balance task difficulty increased, at latencies consistent with longer transcortical sensorimotor loops. We further demonstrate that evoked cortical activity in central midline areas measured using electroencephalography (EEG) can be explained by a similar sensory transformation as muscle activity but at a delay consistent with its role in a transcortical loop driving later cortical contributions to balance-correcting muscle activity. These results demonstrate that a neuromechanical model of muscle activity can be used to infer cortical contributions to muscle activity without recording brain activity. Our model may provide a useful framework for evaluating changes in cortical contributions to balance that are associated with falls in older adults and in neurological disorders such as Parkinson's disease.
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Affiliation(s)
- Scott Boebinger
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States of America
| | - Aiden Payne
- Department of Psychology, Florida State University, Tallahassee, Florida, United States of America
| | - Giovanni Martino
- Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Kennedy Kerr
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States of America
| | - Jasmine Mirdamadi
- Division of Physical Therapy, Department of Rehabilitation Medicine, Emory University, Atlanta, Georgia, United States of America
| | - J. Lucas McKay
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States of America
- Departments of Biomedical Informatics and Neurology, Emory University, Atlanta, Georgia, United States of America
| | - Michael Borich
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States of America
- Division of Physical Therapy, Department of Rehabilitation Medicine, Emory University, Atlanta, Georgia, United States of America
| | - Lena Ting
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States of America
- Division of Physical Therapy, Department of Rehabilitation Medicine, Emory University, Atlanta, Georgia, United States of America
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Reiter DA, Bellissimo MP, Zhou L, Boebinger S, Wells GD, Jones DP, Ziegler TR, Alvarez JA, Fleischer CC. Increased adiposity is associated with altered skeletal muscle energetics. J Appl Physiol (1985) 2023; 134:1083-1092. [PMID: 36759162 PMCID: PMC10125027 DOI: 10.1152/japplphysiol.00387.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 02/08/2023] [Accepted: 02/08/2023] [Indexed: 02/11/2023] Open
Abstract
The objective of this pilot study was to characterize relationships between skeletal muscle energy metabolism and body composition in healthy adults with varied amounts and distribution of adipose tissue. In vivo muscle energetics were quantified using dynamic 31P magnetic resonance spectroscopy with knee extension exercise standardized to subject lean body mass. Spearman's correlation analysis examined relationships between muscle metabolism indices and measures of adiposity including body mass index (BMI), total body fat, and quadriceps intermuscular adipose tissue (IMAT). Post hoc partial correlations were examined controlling for additional body composition measures. Kruskal-Wallis tests with Dunn-Sidak post hoc comparisons evaluated group differences in energy metabolism based on body composition profiles (i.e., lean, normal-weight obese, and overweight-obese) and IMAT tertiles. BMI negatively correlated with end-exercise muscle pH after correcting for IMAT and total body fat (r = -0.46, P = 0.034). Total adiposity negatively correlated with maximum oxidative capacity after correcting for IMAT (r = -0.54, P = 0.013). IMAT positively correlated with muscle proton buffering capacity after correcting for total body fat (r = 0.53, P = 0.023). Body composition groups showed differences in end-exercise fall in [PCr] with normalized workload (P = 0.036; post hoc: overweight-obese < lean, P = 0.029) and maximum oxidative capacity (P = 0.021; post hoc: normal-weight obese < lean, P = 0.016). IMAT tertiles showed differences in end-exercise fall in [PCr] with normalized workload (P = 0.035; post hoc: 3rd < 1st, P = 0.047). Taken together, these results support increased adiposity is associated with reduced muscle energetic efficiency with more reliance on glycolysis, and when accompanied with reduced lean mass, is associated with reduced maximum oxidative capacity.NEW & NOTEWORTHY Skeletal muscle energy production is influenced by both lean body mass and adipose tissue but the effect of their distribution on energy metabolism is unclear. This study examined variations in quadriceps muscle energy metabolism in healthy adults with varied relative amounts of lean and adipose tissue. Results suggest increased adiposity is associated with reduced muscle energetic efficiency with more reliance on glycolysis, and when accompanied with reduced lean mass, is associated with reduced maximum oxidative capacity.
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Affiliation(s)
- David A Reiter
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia, United States
- Department of Orthopedics, Emory University School of Medicine, Atlanta, Georgia, United States
- Department of Biomedical Engineering, Emory University and Georgia Tech, Atlanta, Georgia, United States
| | - Moriah P Bellissimo
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
- Department of Internal Medicine, Virginia Commonwealth University School of Medicine, Richmond, Virginia, United States
| | - Lei Zhou
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Scott Boebinger
- Department of Biomedical Engineering, Emory University and Georgia Tech, Atlanta, Georgia, United States
| | - Greg D Wells
- Department of Translational Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Dean P Jones
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Thomas R Ziegler
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Jessica A Alvarez
- Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Candace C Fleischer
- Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia, United States
- Department of Biomedical Engineering, Emory University and Georgia Tech, Atlanta, Georgia, United States
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