Neuromuscular Adaptations Following Slope Walking in Individuals Post-Stroke

Background: The excitability of the H-reflex pathway in the non-impaired nervous system can be augmented by altering the different parameters of a walking task, specifically slope. We sought to examine the adaptations in soleus H-reflex excitability and foot force control following an acute bout of upslope or downslope treadmill walking in people post-stroke compared to those who are non- impaired. Methods: We recruited 12 individuals with chronic post-stroke hemiparesis and 9 age-similar non- neurologically impaired individuals. Each subject was tested over 2 sessions separated by at least 7 days. For each session, subjects walked at a self-selected walking speed on an instrumented treadmill for 20 minutes under a level and then an upslope condition, or a level and then a downslope condition, with at least an hour rest between the conditions. The vertical component of ground reaction force was used to determine the stance and swing phase of the gait cycle. Peak propulsion and braking forces were analyzed offline for the first (T1) and last minute (T20) of each walking condition to examine adaptations in foot force control. Soleus H-reflexes (Hmax) were tested before and after each walking condition in the paretic legs of the post-stroke group and the right legs of the control group. To ensure consistency, a control M wave (Mmax) preceding the Hmax was kept constant across all conditions for each subject. Peak to peak amplitudes of the maximal H-reflexes and maximal M waves were measured offline and expressed as an Hmax/Mmax ratio. Results: The paretic legs generated higher propulsion force during upslope (11.75±1.04 %BW), but comparable propulsion forces during downslope, when compared to level walking (6.14±0.67 %BW). However, we did observe statistical significance in main effect for slope in paretic (F(2,22)=33.178, p\u3c0.001), non-paretic (F(1.144, 12.585)=23.246, p\u3c0.001) and non-impaired legs (F(1.137, 10.998)=22.766, p\u3c0.001). Pairwise comparisons between slope types indicated that on average, peak braking forces were higher when walking downslope and lower when walking upslope, when compared to level walking. We observed an overall change in Hmax/Mmax ratio following 20 minutes of walking, and the change was different for post-stroke compared to control group, as suggested by the significant interaction between time and group (F(1,19)=16.84, p=0.001). Conclusion: Our observations suggest that when the biomechanics of the walking task is altered, through adjusting the slope of the walking surface, paretic legs exhibit increased propulsion forces during upslope walking. Paretic propulsive forces were greatest in the upslope condition and lowest in the downslope condition. Regardless of group, individuals had greatest braking forces during the downslope condition and lowest during the upslope condition. We believe, based on current studies, that increased paretic propulsion forces in the upslope condition may be due to the increased difficulty of the environmental condition. In the level condition, spinal circuits in the stroke-impaired nervous system are trending towards adaptations similar to the non-impaired nervous system, such that the Hmax/Mmax ratios were depressed. However, in the more challenging upslope condition, adaptations of the paretic soleus H-reflexes were impaired such that the Hmax/Mmax ratios were trending towards elevated. Future studies will examine the optimal walking duration and degree of slope to induce neural adaptations, as well as determine any long-term retention of plasticity

Impaired H-Reflex Adaptations Following Slope Walking in Individuals With Post-stroke Hemiparesis

Background and Purpose: Short term adaptations in the Ia afferent-motoneuron pathway, as measured using the H-reflex, in response to altered ground reaction forces (GRFs) applied at the feet during slope walking have been observed in the non-impaired nervous system. The ability of the stroke-impaired nervous system to adapt to altered GRFs have not been examined. The purpose of this study was to examine the acute effects of altered propulsive and braking forces applied at the feet, which naturally occurs when walking on different slopes, on adaptations of the H-reflex pathway in individuals with chronic post-stroke hemiparesis

Markers of Neuroinflammatory and Degenerative Processes in Professional Athletes with Traumatic Encephalopathy Syndrome

Introduction: The clinical criteria for Traumatic encephalopathy syndrome (ccTES) were developed to improve the diagnosis of Chronic traumatic encephalopathy (CTE). This study aimed to determine whether there was an association between a clinical diagnosis of Traumatic encephalopathy syndrome (TES) and changes in serum biomarkers, balance, neuroimaging, and cognition among athletes in the Professional Athletes Brain Health Study (PABHS).Methods: Of the cohort, 130 professional fighters met age or retirement criteria and went to a consensus conference, with 52 fighters (40%) meeting the criteria for TES. A generalized linear model with generalized estimating equations was utilized to assess the odds of disease for balance and serum biomarker outcomes, while multiple linear regression models compared MRI regional brain volumes and cognitive performance between TES+ and TES- groups. Results: At a threshold of 15 professional fights, significantly greater odds of disease were present for every unit increase in serum GFAP. Likewise, the odds of a TES diagnosis significantly increased by 3% with every additional professional fight completed. A significant association was observed between the presence of a TES diagnosis and worsening performance on single-leg and tandem balance assessments. Significant total mean differences were found in all MRI volumetric regions of interest among TES+ compared to TES-. The rate of volumetric change significantly increased for lateral and inferior lateral ventricles and decreased for the hippocampus, subcortical gray matter, total gray matter, and posterior corpus callosum. Conclusion: The 2021 ccTES distinguishes group differences in the longitudinal presentation and odds of disease for serum biomarkers, balance assessments, regional volumetric loss, and cognitive decline among professional fighters 35 years of age and older. This study indicates a TES diagnosis may be useful in professional sports, further suggesting the application of the ccTES may be valuable clinically in predicting cognitive and functional decline