The interaction of macronutrients and body composition among individuals with chronic spinal cord injury.

Changes in body composition and dietary intake occur following spinal cord injury (SCI). The Geometric Framework for Nutrition (GFN) is a tool that allows the examination of the complex relationships between multiple nutrition factors and health parameters within a single model. This study aimed to utilize the GFN to examine the associations between self-reported macronutrient intakes and body composition in persons with chronic SCI. Forty-eight individuals with chronic SCI were recruited. Participants completed and returned 3- or 5-day self-reported dietary recall sheets. Dietary intake of macronutrients (fats, proteins, and carbohydrates) were analysed. Anthropometric measures (circumferences), dual-energy x-ray absorptiometry (DXA), and magnetic resonance imaging (MRI) were used to assess whlole-body composition. Associations between all circumference measures and carbohydrates were observed. Among MRI measures, only significant associations between subcutaneous adipose tissue and protein x carbohydrate as well as carbohydrates alone were identified. Carbohydrates were negatively associated with several measures of fat mass as measured by DXA. Overall, carbohydrates appear to play an important role in body composition among individuals with SCI. Higher carbohydrate intake was associated with lower fat mass. Additional research is needed to determine how carbohydrate intake influences body composition and cardiometabolic health after SCI.

Assessment of mitochondrial respiratory capacity using minimally invasive and noninvasive techniques in persons with spinal cord injury.

PURPOSE: Muscle biopsies are the gold standard to assess mitochondrial respiration; however, biopsies are not always a feasible approach in persons with spinal cord injury (SCI). Peripheral blood mononuclear cells (PBMCs) and near-infrared spectroscopy (NIRS) may alternatively be predictive of mitochondrial respiration. The purpose of the study was to evaluate whether mitochondrial respiration of PBMCs and NIRS are predictive of respiration of permeabilized muscle fibers after SCI. METHODS: Twenty-two individuals with chronic complete and incomplete motor SCI between 18-65 years old were recruited to participate in the current trial. Using high-resolution respirometry, mitochondrial respiratory capacity was measured for PBMCs and muscle fibers of the vastus lateralis oxidizing complex I, II, and IV substrates. NIRS was used to assess mitochondrial capacity of the vastus lateralis with serial cuff occlusions and electrical stimulation. RESULTS: Positive relationships were observed between PBMC and permeabilized muscle fibers for mitochondrial complex IV (r = 0.86, P < 0.0001). Bland-Altman displayed agreement for complex IV (MD = 0.18, LOA = -0.86 to 1.21), between PBMCs and permeabilized muscles fibers. No significant relationships were observed between NIRS mitochondrial capacity and respiration in permeabilized muscle fibers. CONCLUSIONS: This is the first study to explore and support the agreement of less invasive clinical techniques for assessing mitochondrial respiratory capacity in individuals with SCI. The findings will assist in the application of PBMCs as a viable alternative for assessing mitochondrial health in persons with SCI in future clinical studies.

Accuracy and precision of a wrist movement when vibrotactile prompts inform movement speed.

Purpose: This study investigated the effect of movement speed on task accuracy and precision when participants were provided temporally oriented vibrotactile prompts. Materials and methods: Participants recreated a simple wrist flexion/extension movement at fast and slow speeds based on target patterns conveyed via vibrating motors affixed to the forearm. Each participant was given five performance-blinded trials to complete the task at each speed. Movement accuracy (root mean square error) and precision (standard deviation) were calculated for each trial in both the spatial and temporal domains. Results: 28 participants completed the study. Results showed temporal accuracy and precision improved with movement speed (both: fast > slow, p < 0.01), while all measures improved across trials (temporal accuracy and precision: trial 1 < all other trials, p < 0.05; spatial accuracy: trial 1 and 2 < all other trials, p < 0.05; spatial precision: trial 1 < all other trials, p < 0.05). Conclusions: Overall, temporal and spatial results indicate participants quickly recreated and maintained the desired pattern regardless of speed. Additionally, movement speed seems to influence movement accuracy and precision, particularly within the temporal domain. These results highlight the potential of vibrotactile prompts in rehabilitation paradigms aimed at motor re-education.

The feasibility of using exoskeletal-assisted walking with epidural stimulation: a case report study.

Spinal cord epidural stimulation (SCES) exhibits a rehabilitation potential of restoring locomotion in individuals with spinal cord injury (SCI). However, this is linked to an intensive rehabilitation locomotion approach, which is impractical to apply among a large clinical SCI population. We, hereby, propose a rehabilitation approach of using SCES to enhance motor control during exoskeletal-assisted walking (EAW). After 24 sessions (12 weeks) of EAW swing assistance decreased from 100% to 35% in a person with C7 complete SCI. This was accompanied by 573 unassisted steps (50% of the total number of steps). Electromyographic pattern improved during EAW, reflecting the subject's ability to rhythmically activate paralyzed muscles. Rate perceived exertion increased during EAW with SCES compared to stepping without SCES. These preliminary findings suggest that using SCES with EAW may be a feasible rehabilitation approach for persons with SCI.

Methodological considerations for near-infrared spectroscopy to assess mitochondrial capacity after spinal cord injury.

Background: Skeletal muscle mitochondrial activity is reduced by ∼ 50-60% after SCI, resulting in impaired energy expenditure, glucose utilization and insulin sensitivity. Near infra-red spectroscopy (NIRS) is a non-invasive tool that can be used to assess mitochondrial capacity. Objectives: (1) Highlight methodological limitations impacting data acquisition and analysis such as subcutaneous adipose tissue (SAT) thickness, movement artifacts, inadequate muscle stimulation, light interference, and ischemic discomfort. (2) Provide technical considerations to improve data acquisition and analysis. This may serve as guidance to other researchers and clinicians using NIRS. Study Design: cross-sectional observational design. Settings: Clinical research medical center. Participants: Sixteen men with 1 > year post motor complete SCI. Methods: NIRS signals were obtained from right vastus lateralis muscle utilizing a portable system. Signals were fit to a mono-exponential curve. Outcome Measures: Rate constant and r2 values for the fit curve, indirectly measures mitochondrial capacity. Results: Only four participants produced data with accepted rate constants of 0.002-0.013 s-1 and r2 of 0.71-0.87. Applications of studentized residuals ≥2.5 resulted in sparing data from another four participants with rate constants of 0.010-0.018 s-1and r2 values ranging from 0.86-0.99. Conclusions: Several limitations may challenge the use of NIRS to assess mitochondrial capacity after SCI. Acknowledging these limitations and applying additional data processing techniques may overcome the discussed limitations and facilitate data sparing.

Testosterone and Resistance Training Improve Muscle Quality in Spinal Cord Injury.

PURPOSE: Spinal cord injury (SCI) negatively impacts muscle quality and testosterone levels. Resistance training (RT) has been shown to increase muscle cross-sectional area (CSA) after SCI, whereas testosterone replacement therapy (TRT) has been shown to improve muscle quality in other populations. The purpose of this pilot study was to examine if the combined effects of these interventions, TRT + RT, may maximize the beneficial effects on muscle quality after SCI. METHODS: Twenty-two SCI subjects randomized into either a TRT + RT (n = 11) or TRT (n = 11) intervention for 16 wk. Muscle quality measured by peak torque (PT) at speeds of 0°·s (PT-0°), 60°·s (PT-60°), 90°·s (PT-90°), and 180°·s (PT-180°), knee extensor CSA, specific tension, and contractile speed (rise time [RTi], and half-time to relaxation [½TiR]) was assessed for each limb at baseline and postintervention using 2 × 2 mixed models. RESULTS: After 16 wk, subjects in the TRT + RT group increased PT-0° (48.4%, P = 0.017), knee extensor CSA (30.8%, P < 0.0001), and RTi (17.7%, P = 0.012); with no significant changes observed in the TRT group. Regardless of the intervention, changes to PT-60° (28.4%, P = 0.020), PT-90° (26.1%, P = 0.055), and PT-180° (20.6%, P = 0.09) for each group were similar. CONCLUSIONS: The addition of mechanical stress via RT to TRT maximizes improvements to muscle quality after complete SCI when compared with TRT administered alone. Our evidence shows that this intervention increases muscle size and strength while also improving muscle contractile properties.