Neuromuscular and gene signaling responses to passive whole-body heat stress in young adults.

This study aimed to investigate whether acute passive heat stress 1) decreases muscle Maximal Voluntary Contraction (MVC); 2) increases peripheral muscle fatigue; 3) increases spinal cord excitability, and 4) increases key skeletal muscle gene signaling pathways in skeletal muscle. Examining the biological and physiological markers underlying passive heat stress will assist us in understanding the potential therapeutic benefits. MVCs, muscle fatigue, spinal cord excitability, and gene signaling were examined after control or whole body heat stress in an environmental chamber (heat; 82 °C, 10% humidity for 30 min). Heart Rate (HR), an indicator of stress response, was correlated to muscle fatigue in the heat group (R = 0.59; p < 0.05) but was not correlated to MVC, twitch potentiation, and H reflex suppression. Sixty-one genes were differentially expressed after heat (41 genes >1.5-fold induced; 20 < 0.667 fold repressed). A strong correlation emerged between the session type (control or heat) and principal components (PC1) (R = 0.82; p < 0.005). Cell Signal Transduction, Metabolism, Gene Expression and Transcription, Immune System, DNA Repair, and Metabolism of Proteins were pathway domains with the largest number of genes regulated after acute whole body heat stress. Acute whole-body heat stress may offer a physiological stimulus for people with a limited capacity to exercise.

The relationship between trunk acceleration parameters and kinematic characteristics during walking in patients with stroke.

[Purpose] Limited literature has investigated the relationships between acceleration-based gait characteristics and kinematic information from motion analysis systems in gait analysis. The purpose of this study is to determine whether acceleration-based gait characteristics were associated with gait characteristics by motion analysis systems in patients with stroke. [Participants and Methods] Seventeen patients with stroke walked along a 10-m-long walkway at their comfortable speed. Trunk acceleration was measured with an accelerometer. Several reflective markers over bony landmarks on the lower extremities were used to capture movements. We evaluated the correlations of variables calculated between the trunk accelerometers and the motion analysis system. [Results] Walking speed was positively correlated with harmonic ratios along the anteroposterior axis and stride regularity along the vertical and anteroposterior axes. Harmonic ratios were associated with the stance phase percent on the unaffected side. Stride regularity was associated with the stance phase percent on both sides. Smaller interstride variability was associated with smaller peak ankle plantarflexion during both phases and greater peak ankle dorsiflexion during swing phase. Stride regularity is positively associated with maximal knee flexion during swing phase. [Conclusion] Relationships with spatiotemporal and joint kinematic parameters from the motion analysis system support the potential use of accelerometers.

Rehabilitation Reduced Readmission and Mortality Risks in Patients With Stroke or Transient Ischemic Attack: A Population-based Study.

BACKGROUND: It remains unclear whether rehabilitation has an impact on reducing the long-term risk of mortality or readmission following stroke or transient ischemic attack (TIA). OBJECTIVES: To investigate the association between the dosage and continuation of rehabilitation and the risk of outcome events (OEs) after stroke or TIA. RESEARCH DESIGN: A retrospective cohort study using Taiwan's National Health Insurance database. SUBJECTS: In total, 4594 patients admitted with first-ever acute stroke or TIA were followed-up for 32 months. MEASURES: The occurrence of 3 OEs: (1) vascular readmissions/all-cause mortality [vascular event (VE)], (2) all-cause readmissions/mortality (OE1), and (3) all-cause mortality (OE2), in model 1: none, low-intensity, and high-intensity rehabilitation; and model 2: inpatient plus/or outpatient rehabilitation. RESULTS: Comparing with patients without rehabilitation, in model 1, patients receiving low-intensity rehabilitation had a lower risk of VE [Hazard ratio (HR), 0.77; 95% CI, 0.68-0.87] and OE1 (HR, 0.77; CI, 0.71-0.84), but not OE2 (HR, 0.91; CI, 0.77-1.07). Patients receiving high-intensity rehabilitation had lower risks of all VE (HR, 0.68; CI, 0.58-0.79), OE1 (HR, 0.79; CI, 0.71-0.88), and OE2 (HR, 0.56; CI, 0.44-0.71). In model 2, patients receiving inpatient plus outpatient rehabilitation had a lowest risk of VE (HR, 0.55; CI, 0.47-0.65), OE1 (HR, 0.65; CI, 0.58-0.72), and OE2 (HR, 0.45; CI, 0.35-0.59). Sensitivity analysis with TIA excluded rendered the similar trend. Subgroup analyses found that the positive effect was not demonstrated in hemorrhagic stroke patients. CONCLUSIONS: Rehabilitation use was associated with reduction of readmissions/mortality risks following stroke or TIA. The optimal intensity and duration of rehabilitation and the discrepancy shown in hemorrhagic stroke need further clarification.

A Pilot Randomized Controlled Trial of Botulinum Toxin Treatment Combined with Robot-Assisted Therapy, Mirror Therapy, or Active Control Treatment in Patients with Spasticity Following Stroke.

Effects of the combined task-oriented trainings with botulinum toxin A (BoNT-A) injection on improving motor functions and reducing spasticity remains unclear. This study aims to investigate effects of 3 task-oriented trainings (robot-assisted therapy (RT), mirror therapy (MT), and active control treatment (AC)) in patients with stroke after BoNT-A injection. Thirty-seven patients with chronic spastic hemiplegic stroke were randomly assigned to receive RT, MT, or AC following BoNT-A injection over spastic upper extremity muscles. Each session of RT, MT, and AC was 75 min, 3 times weekly, for 8 weeks. Outcome measures were assessed at pretreatment, post-treatment, and 3-month follow-up, involving the Fugl-Meyer Assessment (FMA), Modified Ashworth Scale (MAS), Motor Activity Log (MAL), including amount of use (AOU) and quality of movement (QOM), and arm activity level. All 3 combined treatments improved FMA, MAS, and MAL. The AC induced a greater effect on QOM in MAL at the 3-month follow-up than RT or MT. All 3 combined trainings induced minimal effect on arm activity level. Our findings suggest that for patients with stroke who received BoNT-A injection over spastic UE muscles, the RT, MT, or AC UE training that followed was effective in improving motor functions, reducing spasticity, and enhancing daily function.

NIH Toolbox Cognition Battery in Young and Older Adults: Reliability and Relationship to Adiposity and Physical Activity.

BACKGROUND AND PURPOSE: Executive function in normal aging may be modulated by body habitus and adiposity, both factors modified by physical therapist prescriptions. This study measured between-day reliability of executive function metrics in young and older individuals and examined associations between cognition, adiposity, and physical activity. METHODS: Forty-three young and 24 older participants underwent executive function assessment via the National Institutes of Health Toolbox Cognition Battery (Dimensional Change Card Sort, Flanker Inhibitory Control and Attention [Flanker], and List Sorting Working Memory [List Sorting]) at 7-day intervals. Between-day reliability was assessed via intraclass correlation (ICC). Responsiveness was assessed via between-day effect size and Cohen's d. Forward stepwise linear regression examined associations between cognition and age, body mass index, percent body fat, and a self-report measure of physical activity (International Physical Activity Questionnaire Short Form). RESULTS AND DISCUSSION: Executive function scores were higher for young participants than for older participants (all P < .002), consistent with typical age-related cognitive decline. Reliability of cognitive metrics was higher for older participants (ICC = 0.483-0.917) than for young participants (ICC = 0.386-0.730). Between-day effect sizes were approximately 50% smaller for older participants. Percent body fat significantly correlated with the Flanker Unadjusted Scale (P = .004, R2 = 0.0772). Neither vigorous nor total physical activity correlated with any cognitive metric. CONCLUSIONS: Older participants demonstrated greater between-day reliability for executive function measures, while young participants showed greater capacity to improve performance upon repeat exposure to a cognitive test (especially Flanker). Percent body fat correlated significantly with Flanker scores, while body mass index (an indirect measure of body fat) did not. Self-reported physical activity did not correlate with executive function. Cognitive response to physical therapist-prescribed exercise is a fertile ground for future research.

Low back pain-associated factors in female hospital-based personal care attendants.

BACKGROUND: Low back pain (LBP) is common in personal care attendants because this profession requires much physical work. Information about the prevalence of LBP and LBP-associated risk factors in this group is limited.OBJECTIVEThis study aimed to investigate the 1-year prevalence of LBP and identify LBP-associated factors in female hospital-based personal care attendants. METHODS: Forty-seven female hospital-based personal care attendants were recruited. The Nordic Musculoskeletal Questionnaire was used to investigate the prevalence of LBP during the recent 12 months. Participants completed a personal traits and associated factors questionnaire. Physical fitness and the knowledge test of body mechanics were assessed. Multivariable logistic regression analysis was used to explore LBP-associated factors. RESULTS: The 1-year prevalence of LBP was 46.8%. The strongest LBP-associated risk factor was poor abdominal muscle endurance, followed by insufficient knowledge on the test of body mechanics and higher psychological stress. CONCLUSIONS: The results demonstrate that the prevalence of LBP in female hospital-based personal care attendants appears to be high. Preventive programs should be initiated to reduce LBP-associated risk factors, such as improving abdominal muscle endurance, providing education in the proper use of body mechanics, and providing psychological intervention services for female hospital-based personal care attendants.

Musculoskeletal disorders, psychosocial stress and associated factors among home-based migrant care workers.

BACKGROUND: Prevalence of musculoskeletal disorders (MSDs) and psychological stress in home-based female migrant care workers (MCWs) remain unknown. OBJECTIVE: To 1) investigate the prevalence of MSDs and psychological stress and associations between subjective questionnaires on MSDs/psychological stress and biomedical examinations, and 2) identify the risk factors related to MSDs and psychological stress. METHODS: This study recruited 85 MCWs. Data was collected using questionnaires, urine analysis and X-ray examinations. Correlations between subjective questionnaires and biomedical examinations were investigated. Multivariable logistic regression analyses were used to explore risk factors. RESULTS: The prevalence of MSDs and psychological stress were 70.6% and 37.6%, respectively. MSDs were commonly reported over the neck, lower back, shoulders, and upper back. There was a moderate correlation between MSDs and abnormal X-ray findings. Risk factors associated with MSDs included higher education level, frequent transferring and bedside care activities, lacking caregiver training in Taiwan, inadequate sleep, and drinking tea or coffee. Risk factors associated with psychological stress included inadequate salary, lacking caregiver training in Taiwan, and insufficient knowledge of body mechanics techniques. CONCLUSIONS: MSDs and psychological stress were common among home-based female MCWs. Educational level, frequent transferring and bedside care activities, and lack of caregiver training in Taiwan, were the most dominant risk factors.

Gait training induced change in corticomotor excitability in patients with chronic stroke.

BACKGROUND: Numerous studies have reported the effects of gait training on motor performance after stroke. However, there is limited information on treatment-induced changes in corticomotor excitability. OBJECTIVES: The purpose of the study was to investigate the effects of additional gait training on motor performance and corticomotor excitability and to demonstrate the relationship between motor improvement and corticomotor excitability change in patients with chronic stroke. METHODS: Fourteen patients were randomly assigned to the experimental or control group. Participants in both groups participated in general physical therapy. Those in the experimental group received additional body weight- supported treadmill training for 4 weeks. All participants received baseline and posttreatment assessments. The outcome measures included assessment of the Berg Balance Scale (BBS) and gait parameters. Focal transcranial magnetic stimulation was used to measure the motor threshold, map size, and location of the amplitude-weighted center of gravity of the motor map for the tibialis anterior (TA) and abductor hallucis (AH) muscles. RESULTS: After general physical therapy, we noted that the patients showed an improvement only in walking speed and cadence, and there were no significant changes in corticomotor excitability. After additional gait training, participants improved significantly on BBS score, walking speed, and step length. Moreover, the motor threshold for TA decreased significantly in the unaffected hemisphere. The map size for TA was increased in both hemispheres, whereas that for AH was increased only in the affected hemisphere. There were significant differences between the change scores of the groups in terms of walking speed, step length, and motor threshold for TA in the unaffected hemisphere and map size for AH in the affected hemisphere. Additionally, the changes in corticomotor excitability correlated with functional improvement. CONCLUSIONS: Additional gait training may improve balance and gait performance and may induce changes in corticomotor excitability.

Low-Force Muscle Activity Regulates Energy Expenditure after Spinal Cord Injury.

Reduced physical activity is a primary risk factor for increased morbidity and mortality. People with spinal cord injury (SCI) have reduced activity for a lifetime, as they cannot volitionally activate affected skeletal muscles. We explored whether low-force and low-frequency stimulation is a viable strategy to enhance systemic energy expenditure in people with SCI. PURPOSE: This study aimed to determine the effects of low stimulation frequency (1 and 3 Hz) and stimulation intensity (50 and 100 mA) on energy expenditure in people with SCI. We also examined the relationship between body mass index and visceral adipose tissue on energy expenditure during low-frequency stimulation. METHODS: Ten individuals with complete SCI underwent oxygen consumption monitoring during electrical activation of the quadriceps and hamstrings at 1 and 3 Hz and at 50 and 100 mA. We calculated the difference in energy expenditure between stimulation and rest and estimated the number of days that would be necessary to burn 1 lb of body fat (3500 kcal) for each stimulation protocol (1 vs 3 Hz). RESULTS: Both training frequencies induced a significant increase in oxygen consumption above a resting baseline level (P < 0.05). Energy expenditure positively correlated with stimulus intensity (muscle recruitment) and negatively correlated with adiposity (reflecting the insulating properties of adipose tissue). We estimated that 1 lb of body fat could be burned more quickly with 1 Hz training (58 d) as compared with 3 Hz training (87 d) if an identical number of pulses were delivered. CONCLUSION: Low-frequency stimulation increased energy expenditure per pulse and may be a feasible option to subsidize physical activity to improve metabolic status after SCI.

Vibration training after chronic spinal cord injury: Evidence for persistent segmental plasticity.

H-reflex paired-pulse depression is gradually lost within the first year post-SCI, a process believed to reflect reorganization of segmental interneurons after the loss of normal descending (cortical) inhibition. This reorganization co-varies in time with the development of involuntary spasms and spasticity. The purpose of this study is to determine whether long-term vibration training may initiate the return of H-reflex paired-pulse depression in individuals with chronic, complete SCI. Five men with SCI received twice-weekly vibration training (30Hz, 0.6g) to one lower limb while seated in a wheelchair. The contra-lateral limb served as a within-subject control. Paired-pulse H-reflexes were obtained before, during, and after a session of vibration. Untrained limb H-reflex depression values were comparable to chronic SCI values from previous reports. In contrast, the trained limbs of all 5 participants showed depression values that were within the range of previously-reported Acute SCI and Non-SCI H-reflex depression. The average difference between limbs was 34.98% (p=0.016). This evidence for the return of H-reflex depression suggests that even for people with long-standing SCI, plasticity persists in segmental reflex pathways. The spinal networks involved with the clinical manifestation of spasticity may thus retain adaptive plasticity after long-term SCI. The results of this study indicate that vibration training may hold promise as an anti-spasticity rehabilitation intervention.

Speed, resistance, and unexpected accelerations modulate feed forward and feedback control during a novel weight bearing task.

We developed a method to investigate feed-forward and feedback movement control during a weight bearing visuomotor knee tracking task. We hypothesized that a systematic increase in speed and resistance would show a linear decrease in movement accuracy, while unexpected perturbations would induce a velocity-dependent decrease in movement accuracy. We determined the effects of manipulating the speed, resistance, and unexpected events on error during a functional weight bearing task. Our long term objective is to benchmark neuromuscular control performance across various groups based on age, injury, disease, rehabilitation status, and/or training. Twenty-six healthy adults between the ages of 19-45 participated in this study. The study involved a single session using a custom designed apparatus to perform a single limb weight bearing task under nine testing conditions: three movement speeds (0.2, 0.4, and 0.6Hz) in combination with three levels of brake resistance (5%, 10%, and 15% of individual's body weight). Individuals were to perform the task according to a target with a fixed trajectory across all speeds, corresponding to a∼0 (extension) to 30° (flexion) of knee motion. An increase in error occurred with speed (p<0.0001, effect size (eta2): η2=0.50) and resistance (p<0.0001, η2=0.01). Likewise, during unexpected perturbations, the ratio of perturbed/non-perturbed error increased with each increment in velocity (p<0.0014, η2=0.08), and resistance (p<0.0001, η2=0.11). The hierarchical framework of these measurements offers a standardized functional weight bearing strategy to assess impaired neuro-muscular control and/or test the efficacy of therapeutic rehabilitation interventions designed to influence neuromuscular control of the knee.

Distinct Skeletal Muscle Gene Regulation from Active Contraction, Passive Vibration, and Whole Body Heat Stress in Humans.

UNLABELLED: Skeletal muscle exercise regulates several important metabolic genes in humans. We know little about the effects of environmental stress (heat) and mechanical stress (vibration) on skeletal muscle. Passive mechanical stress or systemic heat stress are often used in combination with many active exercise programs. We designed a method to deliver a vibration stress and systemic heat stress to compare the effects with active skeletal muscle contraction. PURPOSE: The purpose of this study is to examine whether active mechanical stress (muscle contraction), passive mechanical stress (vibration), or systemic whole body heat stress regulates key gene signatures associated with muscle metabolism, hypertrophy/atrophy, and inflammation/repair. METHODS: Eleven subjects, six able-bodied and five with chronic spinal cord injury (SCI) participated in the study. The six able-bodied subjects sat in a heat stress chamber for 30 minutes. Five subjects with SCI received a single dose of limb-segment vibration or a dose of repetitive electrically induced muscle contractions. Three hours after the completion of each stress, we performed a muscle biopsy (vastus lateralis or soleus) to analyze mRNA gene expression. RESULTS: We discovered repetitive active muscle contractions up regulated metabolic transcription factors NR4A3 (12.45 fold), PGC-1α (5.46 fold), and ABRA (5.98 fold); and repressed MSTN (0.56 fold). Heat stress repressed PGC-1α (0.74 fold change; p < 0.05); while vibration induced FOXK2 (2.36 fold change; p < 0.05). Vibration similarly caused a down regulation of MSTN (0.74 fold change; p < 0.05), but to a lesser extent than active muscle contraction. Vibration induced FOXK2 (p < 0.05) while heat stress repressed PGC-1α (0.74 fold) and ANKRD1 genes (0.51 fold; p < 0.05). CONCLUSION: These findings support a distinct gene regulation in response to heat stress, vibration, and muscle contractions. Understanding these responses may assist in developing regenerative rehabilitation interventions to improve muscle cell development, growth, and repair.