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Norberto MS, Torini JVG, Firmino MS, Papoti M. Validation of Air Storage System for Hypoxia Exposure During Exercise. High Alt Med Biol 2024; 25:122-128. [PMID: 38488104 DOI: 10.1089/ham.2023.0122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2024] Open
Abstract
Norberto, Matheus S., João Victor G. Torini, Matheus S. Firmino, and Marcelo Papoti. Validation of air storage system for hypoxia exposure during exercise. High Alt Med Biol. 00:000-000, 2024.-Considering the importance of optimizing normobaric hypoxia exposure (i.e., higher delivery capacity), the current study aims to validate a hypoxic air storage system. The study has a cross-over, one-blind randomized design. The air storage is composed of a piping system that directs hypoxic air from a hypoxia generator into nylon bags. Sixteen men (age, 25.4 ± 4.8 years; height, 174.9 ± 9.4 cm; weight, 77.1 ± 17.2 kg) performed three incremental treadmill tests until exhaustion on different days. For test-retest, the subjects repeated two tests in similar hypoxia conditions (H1 and H2; fraction of inspired O2 [FIO2] = ∼0.13; reliability analysis), and one time in normoxia (FIO2 = ∼0.20; condition comparison). Subjects' performance, blood lactate concentration ([La-]), arterial oxygen saturation (SpO2), oxygen consumption (VO2), heart rate (HR), and several respiratory-derived variables were evaluated. A comparison was made between the rest, moderate intensity, and exhaustion stages. All variables were compared using the Friedman test with Durbin-Conover post hoc (p < 0.05). The hypoxia test-retest showed no statistical differences for any variable. Time analysis showed similar behavior for SpO2, HR, and cardiorespiratory variables (p < 0.01) for both conditions. The mean FIO2 at rest and during the incremental treadmill test was higher for normoxia (20.6 ± 0.2%) than for H1 (13.8 ± 0.8%) and H2 (13.7 ± 0.3%) (p < 0.001). The VO2 response was higher in normoxia than during hypoxia exposure at moderate intensity (Normoxia = 43.1 ± 8.1; H1 = 38.7 ± 5.7; H2 = 35.8 ± 8.8 ml.kg-1.min-1) and at the exhaustion stage (Normoxia = 52.7 ± 12.5; H1 = 41.9 ± 8.8; H2 = 40.5 ± 8.9 ml.kg-1.min-1) (p < 0.01). SpO2 and HR showed excellent intraclass correlation coefficient (ICC) during all moments, whereas VO2, SpO2, ratio between ventilation and CO2 production (VE/VCO2), ratio between oxygen consumption and ventilation (VE/VO2), and HR showed moderate or good ICC and coefficient of variation <9% during hypoxia test-retest exercises. Thus, the air storage system showed validity for its application and reliability in the measurements associated.
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Affiliation(s)
- Matheus S Norberto
- Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - João Victor G Torini
- School of Physical Education and Sports of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Matheus S Firmino
- Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
- School of Physical Education and Sports of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Marcelo Papoti
- Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
- School of Physical Education and Sports of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
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Bogard AT, Hembree TG, Pollet AK, Smith AC, Ryder SC, Marzloff G, Tan AQ. Intermittent Hypoxia-Induced Enhancements in Corticospinal Excitability Predict Gains in Motor Learning and Metabolic Efficiency. RESEARCH SQUARE 2024:rs.3.rs-4259378. [PMID: 38746438 PMCID: PMC11092812 DOI: 10.21203/rs.3.rs-4259378/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Acute intermittent hypoxia (AIH) enhances human motor function after incomplete spinal cord injury. Although the underlying mechanisms in humans are unknown, emerging evidence indicates that AIH facilitates corticospinal excitability to the upper limb. However, the functional relevance of this plasticity remains unexplored, and it is unclear whether similar plasticity can be induced for lower limb motor areas. We recently demonstrated that AIH improves motor learning and metabolic efficiency during split-belt walking. Thus, we hypothesized that AIH increases lower limb excitability and that these enhancements would predict the magnitude of motor learning and the corresponding reductions in net metabolic power. We assessed tibialis anterior (TA) excitability using transcranial magnetic stimulation and quantified changes in spatiotemporal asymmetries and net metabolic power in response to split-belt speed perturbations. We show that AIH enhances TA excitability, and that the magnitude of this facilitation positively correlates with greater spatiotemporal adaptation. Notably, we demonstrate a novel association between increased excitability and reduced net metabolic power during motor learning and savings. Together, our results suggest that AIH-induced gains in excitability predict both the magnitude of motor learning and the associated metabolic efficiency. Determining indices of AIH-induced improvements in motor performance is critical for optimizing its therapeutic reach.
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Affiliation(s)
- Alysha T. Bogard
- Sensorimotor Recovery and Neuroplasticity Lab at the University of Colorado, Boulder, Dept. of Integrative Physiology, 80309, USA
| | - Thomas G. Hembree
- Sensorimotor Recovery and Neuroplasticity Lab at the University of Colorado, Boulder, Dept. of Integrative Physiology, 80309, USA
| | - Aviva K. Pollet
- Sensorimotor Recovery and Neuroplasticity Lab at the University of Colorado, Boulder, Dept. of Integrative Physiology, 80309, USA
| | - Andrew C. Smith
- University of Colorado School of Medicine, Dept. of Physical Medicine and Rehabilitation, Aurora, 80045, USA
| | | | - George Marzloff
- Rocky Mountain Regional VA Medical Center, Aurora, 80045, USA
| | - Andrew Q. Tan
- Sensorimotor Recovery and Neuroplasticity Lab at the University of Colorado, Boulder, Dept. of Integrative Physiology, 80309, USA
- Rocky Mountain Regional VA Medical Center, Aurora, 80045, USA
- Center for Neuroscience, University of Colorado, Boulder, 80309, USA
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Tan AQ, Tuthill C, Corsten AN, Barth S, Trumbower RD. A single sequence of intermittent hypoxia does not alter stretch reflex excitability in able-bodied individuals. Exp Physiol 2024; 109:576-587. [PMID: 38356241 PMCID: PMC10988685 DOI: 10.1113/ep091531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Accepted: 12/21/2023] [Indexed: 02/16/2024]
Abstract
Spasticity attributable to exaggerated stretch reflex pathways, particularly affecting the ankle plantar flexors, often impairs overground walking in persons with incomplete spinal cord injury. Compelling evidence from rodent models underscores how exposure to acute intermittent hypoxia (AIH) can provide a unique medium to induce spinal plasticity in key inhibitory pathways mediating stretch reflex excitability and potentially affect spasticity. In this study, we quantify the effects of a single exposure to AIH on the stretch reflex in able-bodied individuals. We hypothesized that a single sequence of AIH will increase the stretch reflex excitability of the soleus muscle during ramp-and-hold angular perturbations applied to the ankle joint while participants perform passive and volitionally matched contractions. Our results revealed that a single AIH exposure did not significantly change the stretch reflex excitability during both passive and active matching conditions. Furthermore, we found that able-bodied individuals increased their stretch reflex response from passive to active matching conditions after both sham and AIH exposures. Together, these findings suggest that a single AIH exposure might not engage inhibitory pathways sufficiently to alter stretch reflex responses in able-bodied persons. However, the generalizability of our present findings requires further examination during repetitive exposures to AIH along with potential reflex modulation during functional movements, such as overground walking.
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Affiliation(s)
- Andrew Q. Tan
- Department of Integrative PhysiologyUniversity of ColoradoBoulderColoradoUSA
| | - Christopher Tuthill
- Department of Physical Medicine and RehabilitationHarvard Medical SchoolBostonMassachusettsUSA
- Department of Physical Medicine and RehabilitationINSPIRE LaboratorySpaulding Rehabilitation HospitalBostonMassachusettsUSA
| | - Anthony N. Corsten
- Department of Physical Medicine and RehabilitationINSPIRE LaboratorySpaulding Rehabilitation HospitalBostonMassachusettsUSA
| | - Stella Barth
- Department of Physical Medicine and RehabilitationINSPIRE LaboratorySpaulding Rehabilitation HospitalBostonMassachusettsUSA
| | - Randy D. Trumbower
- Department of Physical Medicine and RehabilitationHarvard Medical SchoolBostonMassachusettsUSA
- Department of Physical Medicine and RehabilitationINSPIRE LaboratorySpaulding Rehabilitation HospitalBostonMassachusettsUSA
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Muter WM, Mansson L, Tuthill C, Aalla S, Barth S, Evans E, McKenzie K, Prokup S, Yang C, Sandhu M, Rymer WZ, Edgerton VR, Gad P, Mitchell GS, Wu SS, Shan G, Jayaraman A, Trumbower RD. A Research Protocol to Study the Priming Effects of Breathing Low Oxygen on Enhancing Training-Related Gains in Walking Function for Persons With Spinal Cord Injury: The BO 2ST Trial. Neurotrauma Rep 2023; 4:736-750. [PMID: 38028272 PMCID: PMC10659019 DOI: 10.1089/neur.2023.0036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2023] Open
Abstract
Brief episodes of low oxygen breathing (therapeutic acute intermittent hypoxia; tAIH) may serve as an effective plasticity-promoting primer to enhance the effects of transcutaneous spinal stimulation-enhanced walking therapy (WALKtSTIM) in persons with chronic (>1 year) spinal cord injury (SCI). Pre-clinical studies in rodents with SCI show that tAIH and WALKtSTIM therapies harness complementary mechanisms of plasticity to maximize walking recovery. Here, we present a multi-site clinical trial protocol designed to examine the influence of tAIH + WALKtSTIM on walking recovery in persons with chronic SCI. We hypothesize that daily (eight sessions, 2 weeks) tAIH + WALKtSTIM will elicit faster, more persistent improvements in walking recovery than either treatment alone. To test our hypothesis, we are conducting a placebo-controlled clinical trial on 60 SCI participants who randomly receive one of three interventions: tAIH + WALKtSTIM; Placebo + WALKtSTIM; and tAIH + WALKtSHAM. Participants receive daily tAIH (fifteen 90-sec episodes at 10% O2 with 60-sec intervals at 21% O2) or daily placebo (fifteen 90-sec episodes at 21% O2 with 60-sec intervals at 21% O2) before a 45-min session of WALKtSTIM or WALKtSHAM. Our primary outcome measures assess walking speed (10-Meter Walk Test), endurance (6-Minute Walk Test), and balance (Timed Up and Go Test). For safety, we also measure pain levels, spasticity, sleep behavior, cognition, and rates of systemic hypertension and autonomic dysreflexia. Assessments occur before, during, and after sessions, as well as at 1, 4, and 8 weeks post-intervention. Results from this study extend our understanding of the functional benefits of tAIH priming by investigating its capacity to boost the neuromodulatory effects of transcutaneous spinal stimulation on restoring walking after SCI. Given that there is no known cure for SCI and no single treatment is sufficient to overcome walking deficits, there is a critical need for combinatorial treatments that accelerate and anchor walking gains in persons with lifelong SCI. Trial Registration ClinicalTrials.gov, NCT05563103.
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Affiliation(s)
- William M. Muter
- Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA
| | - Linda Mansson
- Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts, USA
| | - Christopher Tuthill
- Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts, USA
| | - Shreya Aalla
- Shirley Ryan AbilityLab, Max Nader Center for Rehabilitation Technologies and Outcomes Research, Chicago, Illinois, USA
| | - Stella Barth
- Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA
- UMass Chan Medical School, University of Massachusetts, Worcester, Massachusetts, USA
| | - Emily Evans
- Department of Physical Therapy, Boston University, Boston, Massachusetts, USA
| | - Kelly McKenzie
- Shirley Ryan AbilityLab, Max Nader Center for Rehabilitation Technologies and Outcomes Research, Chicago, Illinois, USA
| | - Sara Prokup
- Shirley Ryan AbilityLab, Max Nader Center for Rehabilitation Technologies and Outcomes Research, Chicago, Illinois, USA
| | - Chen Yang
- Shirley Ryan AbilityLab, Max Nader Center for Rehabilitation Technologies and Outcomes Research, Chicago, Illinois, USA
| | - Milap Sandhu
- Shirley Ryan AbilityLab, Max Nader Center for Rehabilitation Technologies and Outcomes Research, Chicago, Illinois, USA
| | - W. Zev Rymer
- Shirley Ryan AbilityLab, Max Nader Center for Rehabilitation Technologies and Outcomes Research, Chicago, Illinois, USA
| | - Victor R. Edgerton
- Department of Integrative Biology and Physiology, University of California–Los Angeles, Los Angeles, California, USA
- SpineX Inc., Northridge, California, USA
| | - Parag Gad
- Department of Integrative Biology and Physiology, University of California–Los Angeles, Los Angeles, California, USA
- SpineX Inc., Northridge, California, USA
| | - Gordon S. Mitchell
- Department of Physical Therapy, University of Florida, Gainesville, Florida, USA
| | - Samuel S. Wu
- Department of Biostatistics, University of Florida, Gainesville, Florida, USA
| | - Guogen Shan
- Department of Biostatistics, University of Florida, Gainesville, Florida, USA
| | - Arun Jayaraman
- Shirley Ryan AbilityLab, Max Nader Center for Rehabilitation Technologies and Outcomes Research, Chicago, Illinois, USA
| | - Randy D. Trumbower
- Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts, USA
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Trumbower RD, Barth S, Tuthill C, Slocum C, Shan G, Zafonte R, Mitchell GS. Caffeine Enhances Intermittent Hypoxia-Induced Gains in Walking Function for People with Chronic Spinal Cord Injury. J Neurotrauma 2022; 39:1756-1763. [PMID: 35686460 PMCID: PMC9734018 DOI: 10.1089/neu.2022.0120] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Incomplete spinal cord injury (iSCI) often results in lifelong walking impairments that limit functional independence. Thus, treatments that trigger enduring improvement in walking after iSCI are in high demand. Breathing brief episodes of low oxygen (i.e., acute intermittent hypoxia, AIH) enhances breathing and walking function in rodents and humans with chronic iSCI. Pre-clinical studies found that AIH also causes the accumulation of extracellular adenosine that undermines AIH-induced functional plasticity. Pharmacologically blocking adenosine A2a receptors (A2aR) prior to AIH resulted in a dramatic improvement in motor facilitation in rodents with iSCI; however, a similar beneficial effect in humans is unclear. Thus, we conducted a double-blind, placebo-controlled, crossover randomized study to test the hypothesis that a non-selective A2aR antagonist (i.e., caffeine) enhances AIH-induced effects on walking function in people with chronic (≥1yr) iSCI. We enrolled 12 participants to receive daily (5 days) caffeine or placebo (4 mg/kg) 30 min before breathing 15, 1.5-min low oxygen (AIH; FIO2 = 0.10) or SHAM (FIO2 = 0.21) episodes with 1-min intervals. We quantified walking function as the change in the 10-meter walk test (speed) and 6-min walk test (endurance) relative to baseline, on Day 5 post-intervention, and on follow-up Days 12 and 19. Participants walked faster (Day 19; p < 0.001) and farther (Day 19; p = 0.012) after caffeine+AIH and the boost in speed persisted more than after placebo+AIH or caffeine+SHAM (Day 19; p < 0.05). These results support our hypothesis that a caffeine pre-treatment to AIH training shows promise as a strategy to augment walking speed in persons with chronic iSCI.
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Affiliation(s)
- Randy D. Trumbower
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts, USA.,Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA.,Address correspondence to: Randy D. Trumbower, PT, PhD, Department of Physical Medicine and Rehabilitation, Harvard Medical School and Spaulding Rehabilitation Hospital, 1575 Cambridge Street, Cambridge, MA 02138, USA
| | - Stella Barth
- Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA
| | - Christopher Tuthill
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts, USA
| | - Chloe Slocum
- Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA
| | - Guogen Shan
- Department of Biostatistics, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Ross Zafonte
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts, USA.,Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA
| | - Gordon S. Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy, College of Medicine, University of Florida, Gainesville, Florida, USA
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Golcuk A. Design and implementation of a hybrid FLC + PID controller for pressure control of sleep devices. Biomed Signal Process Control 2022. [DOI: 10.1016/j.bspc.2022.103702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Vose AK, Welch JF, Nair J, Dale EA, Fox EJ, Muir GD, Trumbower RD, Mitchell GS. Therapeutic acute intermittent hypoxia: A translational roadmap for spinal cord injury and neuromuscular disease. Exp Neurol 2022; 347:113891. [PMID: 34637802 PMCID: PMC8820239 DOI: 10.1016/j.expneurol.2021.113891] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 09/29/2021] [Accepted: 10/03/2021] [Indexed: 01/03/2023]
Abstract
We review progress towards greater mechanistic understanding and clinical translation of a strategy to improve respiratory and non-respiratory motor function in people with neuromuscular disorders, therapeutic acute intermittent hypoxia (tAIH). In 2016 and 2020, workshops to create and update a "road map to clinical translation" were held to help guide future research and development of tAIH to restore movement in people living with chronic, incomplete spinal cord injuries. After briefly discussing the pioneering, non-targeted basic research inspiring this novel therapeutic approach, we then summarize workshop recommendations, emphasizing critical knowledge gaps, priorities for future research effort, and steps needed to accelerate progress as we evaluate the potential of tAIH for routine clinical use. Highlighted areas include: 1) greater mechanistic understanding, particularly in non-respiratory motor systems; 2) optimization of tAIH protocols to maximize benefits; 3) identification of combinatorial treatments that amplify plasticity or remove plasticity constraints, including task-specific training; 4) identification of biomarkers for individuals most/least likely to benefit from tAIH; 5) assessment of long-term tAIH safety; and 6) development of a simple, safe and effective device to administer tAIH in clinical and home settings. Finally, we update ongoing clinical trials and recent investigations of tAIH in SCI and other clinical disorders that compromise motor function, including ALS, multiple sclerosis, and stroke.
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Affiliation(s)
- Alicia K Vose
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA; Brooks Rehabilitation, Jacksonville, FL 32216, USA
| | - Joseph F Welch
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA; Brooks Rehabilitation, Jacksonville, FL 32216, USA
| | - Jayakrishnan Nair
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
| | - Erica A Dale
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL 32610, USA
| | - Emily J Fox
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA; Brooks Rehabilitation, Jacksonville, FL 32216, USA
| | - Gillian D Muir
- Department of Biomedical Sciences, WCVM, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
| | - Randy D Trumbower
- Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA
| | - Gordon S Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA.
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Editorial: Intermittent hypoxia. Exp Neurol 2021; 348:113951. [PMID: 34955452 DOI: 10.1016/j.expneurol.2021.113951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Daily acute intermittent hypoxia combined with walking practice enhances walking performance but not intralimb motor coordination in persons with chronic incomplete spinal cord injury. Exp Neurol 2021; 340:113669. [PMID: 33647273 DOI: 10.1016/j.expneurol.2021.113669] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 02/14/2021] [Accepted: 02/25/2021] [Indexed: 12/15/2022]
Abstract
Persons living with incomplete spinal cord injuries (SCI) often struggle to regain independent walking due to deficits in walking mechanics. They often dedicate many weeks of gait training before benefits to emerge, with additional training needed for benefits to persist. Recent studies in humans with SCI found that daily bouts of breathing low oxygen (acute intermittent hypoxia, AIH) prior to locomotor training elicited persistent (weeks) improvement in overground walking speed and endurance. AIH-induced improvements in overground walking may result from changes in control strategies that also enhance intralimb coordination; however, this possibility remains untested. Here, we examined the extent to which daily AIH combined with walking practice (AIH + WALK) improved overground walking performance and intralimb motor coordination in persons with chronic, incomplete SCI. METHODS We recruited 11 persons with chronic (> 1 year), incomplete SCI to participate in a randomized, double-blind, balanced, crossover study. Participants first received either daily (5 consecutive days) AIH (15, 90-s episodes of 10.0% O2 with 60s intervals at 20.9% O2) or SHAM (15, 90s episodes at 20.9% O2 with 60s intervals at 20.9% O2) followed by 30-min of overground walking practice. They received the second treatment after a minimum 2-week washout period. We quantified overground walking performance, in terms of speed and endurance, using the 10-Meter Walk Test (10MWT) and 6-Minute Walk Test (6MWT), respectively. We quantified intralimb motor coordination using kinematic variability measures of foot trajectory (i.e., endpoint variability, EV) and of inter-joint coupling between the hip and knee, as well as between the knee and ankle joints (i.e., angular coefficient of correspondence, ACC). We compared the changes in walking performance relative to baseline (BL) between daily AIH + WALK and daily SHAM+WALK on treatment day 5 (T5), 1-week follow-up (F1), and 2-weeks follow-up (F2). We also compared these changes between participants who used bilateral walking aids (N = 5) and those who did not. To assess the effects of daily AIH + WALK on intralimb coordination, we compared potential treatment-induced changes in EV and ACC relative to BL at F1 and F2. RESULTS Participants improved overground walking performance (speed and endurance) after daily AIH + WALK, but not SHAM+WALK. Following daily AIH + WALK, participants decreased their 10MWT time at T5 by 28% (95% CI 0.2-10.1 s, p = 0.04), F1 by 28% (95% CI 1.1-13.5 s, p = 0.01), and F2 by 27% (95% CI 1.4-13.9 s, p = 0.01) relative to BL. The greatest decreases in the 10MWT occurred in participants who used bilateral walking aids (p < 0.05). We also found daily AIH + WALK resulted in an increase in 6MWT distance at T5 by 22% (95% CI 13.3-72.6 m, p = 0.001), F1 by 21% (95% CI 13.1-72.5 m, p = 0.001), and F2 by 16% (95% CI 2.9-62.2 m, p = 0.02). However, measures of EV and ACC during self-selected walking conditions did not change following daily AIH + WALK (all p-values >0.50). CONCLUSIONS Consistent with prior studies, daily AIH + WALK triggered improvements in walking speed and endurance that persisted for weeks after treatment. Greatest improvements in speed occurred in participants who used bilateral walking aids. No change in EV and ACC may suggest that intralimb motor coordination was not a significant gait training priority during daily AIH + WALK.
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