Functional Implications of Impaired Control of Submaximal Hip Flexion Following Stroke

Introduction: We quantified sub-maximal torque regulation during low to moderate intensity isometric hip flexion contractions in individuals with stroke and the associations with leg function. Methods: 10 participants with chronic stroke and 10 controls performed isometric hip flexion contractions at 5%, 10%, 15%, 20%, and 40% of maximal voluntary contraction (MVC) in paretic, non-paretic, and control legs. Results: Participants with stroke had larger torque fluctuations (coefficient of variation, CV), for both the paretic and non-paretic legs, than controls (Pr2 =0.45) and Berg Balance Score (r2=0.38). At 5% MVC, there were larger torque fluctuations in the contralateral leg during paretic contractions compared with the control leg. Conclusions: Impaired low-force regulation of paretic leg hip flexion can be functionally relevant and related to control versus strength deficits post stroke

The interaction of solid-density nano-scale clusters with high-intensity XUV laser pulses

Studies of the interaction between high intensity, high frequency pulsed lasers and nano-scale material have a broad range of potential applications, from ultrafast biomolecular imaging to fundamental questions of the time scales associated with molecular electronic processes. ̀̀Table-top'' XUV lasers utilizing HHG to produce a broad range of photon energies are a promising new source of this ultrafast high frequency radiation. Here, we present data generated by the irradiation of nano-scale cluster targets, composed of both solids and van der Waals-bound gases, by high-intensity XUV pulses generated using the new HHG beamline of the UT THOR laser system. On-target intensities are 1 x 10¹³ W/cm², and photon energies range from 26.4 eV to 32.6 eV. These interactions consistently produce anomalously high charge states in the loosely-bound dense gas clusters; charge states of Xe⁸⁺, Kr⁶⁺, Ar⁵⁺, Ne³⁺, and N²⁺ were observed. The yield ratios of these charge states, as well as the ion and electron kinetic energies collected during these interactions, help to shed light on the processes of formation and dissociation of these dense plasmas.Physic

Retributive Justice: The Gacaca Process in Rwanda

After decades of cycling violence between Hutu and Tutsi groups in Rwanda and Burundi, violence peaked in 1994 with a genocide of Tutsis in Rwanda, during which the Hutu majority slaughtered 800,000 Tutsi and moderate Hutus, leaving the country with 120,000 accused génocidaires awaiting trial. Rwanda\u27s gacaca courts were established as a response to the backlog of untried genocide cases. These courts disturbingly distinguish between genocide and war crimes committed during the same era, trying only those accused of genocide. This article argues that the gacaca process will contribute to the insecurity of all Rwandan citizens in the future, since it pursues inequitable justice, accentuates the ethnic divide and will be interpreted as revenge

Stroke-related Changes in Neuromuscular Fatigue of the Hip Flexors and Functional Implications

Objective: The aim of this study was to compare stroke-related changes in hip flexor neuromuscular fatigue of the paretic leg during a sustained isometric submaximal contraction with those of the nonparetic leg and controls and to correlate fatigue with clinical measures of function. Design: Hip torques were measured during a fatiguing hip flexion contraction at 20% of the hip flexion maximal voluntary contraction in the paretic and nonparetic legs of 13 people with chronic stroke and 10 age-matched controls. In addition, the participants with stroke performed a fatiguing contraction of the paretic leg at the absolute torque equivalent to 20% maximal voluntary contraction of the nonparetic leg and were tested for self-selected walking speed (10-m Walk Test) and balance (Berg). Results: When matching the nonparetic target torque, the paretic hip flexors had a shorter time to task failure compared with the nonparetic leg and controls (P \u3c 0.05). The time to failure of the paretic leg was inversely correlated with the reduction of hip flexion maximal voluntary contraction torque. Self-selected walking speed was correlated with declines in torque and steadiness. Berg-Balance scores were inversely correlated with the force fluctuation amplitude. Conclusions: Fatigue and precision of contraction are correlated with walking function and balance after stroke

The Stroke-related Effects of Hip Flexion Fatigue on Over Ground Walking

Individuals post stroke often rely more on hip flexors for limb advancement during walking due to distal weakness but the effects of muscle fatigue in this group is not known. The purpose of this study was to quantify how stroke affects the influence of hip flexor fatigue on over ground walking kinematics and performance and muscle activation. Ten individuals with chronic stroke and 10 without stroke (controls) participated in the study. Maximal walking speed, walking distance, muscle electromyograms (EMG), and lower extremity joint kinematics were compared before and after dynamic, submaximal fatiguing contractions of the hip flexors (30% maximal load) performed until failure of the task. Task duration and decline in hip flexion maximal voluntary contraction (MVC) and power were used to assess fatigue. The stroke and control groups had similar task durations and percent reductions in MVC force following fatiguing contractions. Compared with controls, individuals with stroke had larger percent reductions in maximal walking speed, greater decrements in hip range of motion and peak velocity during swing, greater decrements in ankle velocity and lack of modulation of hip flexor EMG following fatiguing dynamic hip flexion contractions. For a given level of fatigue, the impact on walking function was more profound in individuals with stroke than neurologically intact individuals, and a decreased ability to up regulate hip flexor muscle activity may contribute. These data highlight the importance of monitoring the effect of hip flexor muscle activity during exercise or performance of activities of daily living on walking function post stroke

Stroke-related Effects on Maximal Dynamic Hip Flexor Fatigability and Functional Implications

Introduction: Stroke-related changes in maximal dynamic hip flexor muscle fatigability may be more relevant functionally than isometric hip flexor fatigability. Methods: Ten chronic stroke survivors performed 5 sets of 30 hip flexion maximal dynamic voluntary contractions (MDVC). A maximal isometric voluntary contraction (MIVC) was performed before and after completion of the dynamic contractions. Both the paretic and nonparetic legs were tested. Results: Reduction in hip flexion MDVC torque in the paretic leg (44.7%) was larger than the nonparetic leg (31.7%). The paretic leg had a larger reduction in rectus femoris EMG (28.9%) between the first and last set of MDVCs than the nonparetic leg (7.4%). Reduction in paretic leg MDVC torque was correlated with self-selected walking speed (r2 = 0.43), while reduction in MIVC torque was not (r2 = 0.11). Conclusions: Reductions in maximal dynamic torque of paretic hip flexors may be a better predictor of walking function than reductions in maximal isometric contractions

Book Discussion

Book discussion of Persepolis: The Story of a Childhood by Marjane Satrapi. Faculty panelists include Sandra Gandy, JoAnne Smith, and Jason Zingsheim with Provost Terry Allison as moderator