Reevaluating Rehabilitation Practice for Patients Who Were Critically Ill After COVID-19 Infection: An Administrative Case Report.

OBJECTIVE: The goal of this case report is to describe the process, challenges, and opportunities of implementing rehabilitation for individuals who were critically ill and required both mechanical ventilation (MV) and extracorporeal membrane oxygenation (ECMO) support following a coronavirus 2019 (COVID-19) infection in an academic medical center. METHODS: This administrative case report is set in a heart and vascular intensive care unit, a 35-bed critical care unit that provides services for patients with various complex cardiovascular surgical interventions, including transplantation. Patients were admitted to the heart and vascular intensive care unit with either COVID-19 acute respiratory distress syndrome or pulmonary fibrosis for consideration of bilateral orthotropic lung transplantation. The authors describe the process of establishing rehabilitation criteria for patients who, by previously established guidelines, would be considered too ill to engage in rehabilitation. RESULTS: The rehabilitation team, in coordination with an interprofessional team of critical care providers including physicians, respiratory care providers, perfusionists, and registered nurses, collaborated to implement a rehabilitation program for patients with critical COVID-19 being considered for bilateral orthotropic lung transplantation. This was accomplished by (1) reviewing previously published guidelines and practices; (2) developing an interdisciplinary framework for the consideration of rehabilitation treatment; and (3) implementing the framework for patients in our heart and vascular intensive care unit. CONCLUSION: In response to the growing volume of patients admitted with critical COVID-19, the team initiated and developed an interprofessional framework and successfully provided rehabilitation services to patients who were critically ill. While resource-intensive, the process demonstrates that rehabilitation can be implemented on a case-by-case basis for select patients receiving extracorporeal membrane oxygenation and MV, who would previously have been considered too critically ill for rehabilitation services. IMPACT: Rehabilitating patients with end-stage pulmonary disease on extracorporeal membrane oxygenation and MV support is challenging but feasible with appropriate interprofessional collaboration and knowledge sharing.

Rehabilitation Characteristics and Outcomes for Lung Transplantation for COVID-19: A Case Series.

OBJECTIVE: Severe coronavirus disease 2019 (COVID-19) can result in irreversible lung damage, with some individuals requiring lung transplantation. The purpose of this case series is to describe the initial experience with the rehabilitation and functional outcomes of 9 patients receiving a lung transplant for COVID-19. METHODS: Nine individuals, ranging in age from 37 to 68 years, received bilateral orthotopic lung transplantation (BOLT) for COVID-19 between December 2020 and July 2021. Rehabilitation was provided before and after the transplant, including in-hospital rehabilitation, postacute care inpatient rehabilitation, and outpatient rehabilitation. RESULTS: Progress with mobility was limited in the pretransplant phase despite rehabilitation efforts. Following transplantation, 2 individuals expired before resuming rehabilitation, and 2 others had complications that delayed their progress. The remaining 5 experienced clinically important improvements in mobility and walking capacities. CONCLUSION: Considerable rehabilitation resources are required to care for individuals both before and after BOLT for COVID-19. Rehabilitation can have a profound impact on both functional and clinical outcomes for this unique patient population. IMPACT: There is limited literature on the rehabilitation efforts and outcomes for patients who received BOLT for COVID-19. Occupational therapists and physical therapists play an important role during the pretransplant and posttransplant recovery process for this novel patient population. LAY SUMMARY: Patients with a bilateral orthotopic lung transplant due to COVID-19 require a unique rehabilitation process. They have significant difficulties with activities of daily living and functional mobility across the pretransplant and posttransplant continuum of care, but progressive gains in functional performance may be possible with a comprehensive multidisciplinary rehabilitation program.

Development of the Lung Transplant Frailty Scale (LT-FS).

BACKGROUND: Existing measures of frailty developed in community dwelling older adults may misclassify frailty in lung transplant candidates. We aimed to develop a novel frailty scale for lung transplantation with improved performance characteristics. METHODS: We measured the short physical performance battery (SPPB), fried frailty phenotype (FFP), Body Composition, and serum Biomarkers representative of putative frailty mechanisms. We applied a 4-step established approach (identify frailty domain variable bivariate associations with the outcome of waitlist delisting or death; build models sequentially incorporating variables from each frailty domain cluster; retain variables that improved model performance ability by c-statistic or AIC) to develop 3 candidate "Lung Transplant Frailty Scale (LT-FS)" measures: 1 incorporating readily available clinical data; 1 adding muscle mass, and 1 adding muscle mass and research-grade Biomarkers. We compared construct and predictive validity of LT-FS models to the SPPB and FFP by ANOVA, ANCOVA, and Cox proportional-hazard modeling. RESULTS: In 342 lung transplant candidates, LT-FS models exhibited superior construct and predictive validity compared to the SPPB and FFP. The addition of muscle mass and Biomarkers improved model performance. Frailty by all measures was associated with waitlist disability, poorer HRQL, and waitlist delisting/death. LT-FS models exhibited stronger associations with waitlist delisting/death than SPPB or FFP (C-statistic range: 0.73-0.78 vs. 0.57 and 0.55 for SPPB and FFP, respectively). Compared to SPPB and FFP, LT-FS models were generally more strongly associated with delisting/death and improved delisting/death net reclassification, with greater improvements with increasing LT-FS model complexity (range: 0.11-0.34). For example, LT-FS-Body Composition hazard ratio for delisting/death: 6.0 (95%CI: 2.5, 14.2), SPPB HR: 2.5 (95%CI: 1.1, 5.8), FFP HR: 4.3 (95%CI: 1.8, 10.1). Pre-transplant LT-FS frailty, but not SPPB or FFP, was associated with mortality after transplant. CONCLUSIONS: The LT-FS is a disease-specific physical frailty measure with face and construct validity that has superior predictive validity over established measures.

Activity Measure for Post-Acute Care "6-Clicks" for the Prediction of Short-term Clinical Outcomes in Individuals Hospitalized With COVID-19: A Retrospective Cohort Study.

OBJECTIVE: To determine the ability of the Activity Measure for Post-Acute Care (AM-PAC) "6-Clicks" assessments of mobility and activity to predict key clinical outcomes in patients hospitalized with coronavirus disease 2019 (COVID-19). DESIGN: Retrospective cohort study. SETTING: An academic health system in the United States consisting of 5 inpatient hospitals. PARTICIPANTS: Adult patients (N=1486) urgently or emergently admitted who tested positive for COVID-19 and had at least 1 AM-PAC assessment. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Discharge destination, hospital length of stay, in-hospital mortality, and readmission. RESULTS: A total of 1486 admission records were included in the analysis. After controlling for covariates, initial and final mobility (odds ratio, 0.867 and 0.833, respectively) and activity scores (odds ratio, 0.892 and 0.862, respectively) were both independent predictors of discharge destination with a high accuracy of prediction (area under the curve [AUC]=0.819-0.847). Using a threshold score of 17.5, sensitivity ranged from 0.72-0.79, whereas specificity ranged from 0.74-0.83. Both initial AM-PAC mobility and activity scores were independent predictors of mortality (odds ratio, 0.885 and 0.877, respectively). Initial mobility, but not activity, scores were predictive of prolonged length of stay (odds ratio, 0.957 and 0.980, respectively). However, the accuracy of prediction for both outcomes was weak (AUC=0.659-0.679). AM-PAC scores did not predict rehospitalization. CONCLUSIONS: Functional status as measured by the AM-PAC "6-Clicks" mobility and activity scores are independent predictors of key clinical outcomes individual hospitalized with COVID-19.

Acute Rehabilitation of a Patient With COVID-19 Myocarditis: A Case Report.

OBJECTIVE: The purpose of this case report is to describe the acute rehabilitation of an individual with severe COVID-19 complicated by myocarditis, focusing on both facility-wide and patient-specific strategies. METHODS: A 50-year-old male presented to the emergency department with progressive dyspnea and confirmed COVID-19. He developed hypoxic respiratory failure and heart failure requiring prolonged mechanical ventilation. Mobility was limited by severe impairments in strength, endurance, balance, and cognition. The referral, screening, and rehabilitation of this patient were guided by a COVID-19 Service Delivery Plan designed to maximize the effectiveness and efficiency of care delivery while minimizing staff exposure to the virus. Coordinated physical and occupational therapy sessions focused on progressive mobility and cognitive retraining. Progress was monitored using a series of standardized outcome measures, including the Activity Measure for Post-Acute Care, Timed Up and Go test, and the Saint Louis University Mental Status examination. RESULTS: Rehabilitation was initiated on day 18, and the patient participated in 19 treatment sessions, each approximately 30 minutes, over the remaining 30 days of his hospital stay. His Activity Measure for Post-Acute Care mobility and function scores both improved from 100% to 0% disability, he experienced substantial improvements in both Timed Up and Go (Δ = 4.2 seconds) and Saint Louis University Mental Status (discharge score = 25). There were no adverse events. He was discharged to home with his family and home rehabilitation services. CONCLUSION: COVID-19 contributed to severe declines in mobility and function in this middle-aged man. He experienced substantial gains in his function, mobility, and cognition during his in-hospital rehabilitation, which was guided by a facility-wide plan to prevent virus transmission. IMPACT: The rehabilitation of individuals with severe COVID-19 presents significant challenges, both at the level of the individual patient and the whole facility. This report describes clinical decision-making required to manage these individuals in the setting of a global pandemic.

The 4-Element Movement System Model to Guide Physical Therapist Education, Practice, and Movement-Related Research.

The movement system has been adopted as the key identity for the physical therapy profession, and recognition of physical therapists' primary expertise in managing movement dysfunction is an important achievement. However, existing movement system models seem inadequate for guiding education, practice, or research. Lack of a clear, broadly applicable model may hamper progress in physical therapists actually adopting this identity. We propose a model composed of 4 primary elements essential to all movement: motion, force, energy, and control. Although these elements overlap and interact, they can each be examined and tested with some degree of specificity. The proposed 4-element model incorporates specific guidance for visual, qualitative assessment of movement during functional tasks that can be used to develop hypotheses about movement dysfunction and serve as a precursor to more quantitative tests and measures. Human movement always occurs within an environmental context and is affected by personal factors, and these concepts are represented within the model. The proposed scheme is consistent with other widely used models within the profession, such as the International Classification of Functioning, Disability and Health and the Patient Management Model. We demonstrate with multiple examples how the model can be applied to a broad spectrum of patients across the lifespan with musculoskeletal, neurologic, and cardiopulmonary disorders.

Discharge frailty following lung transplantation.

INTRODUCTION: Frailty at listing for lung transplant has been associated with waitlist and post-transplant mortality. Frailty trajectories following transplant, however, have been less well characterized, including whether recipient frailty improves. The objective of this study was to identify prevalence and risk factors for frailty at discharge and to evaluate changes in frail recipients enrolled in an outpatient physical therapy program. METHODS: This was a single-center prospective cohort study of lung transplant recipients. Enrollees completed a short physical performance battery (SPPB) to assess frailty at listing and at initial hospital discharge. RESULTS: Of the 111 enrolled recipients, none were frail at listing and 18 (16.2%) were prefrail. At discharge, however, 60 (54.1%) patients were frail. Discharge frailty was associated with prefrailty at listing, acute kidney injury post-transplant, and longer intensive care unit stay. Among the 35 patients who were frail at discharge and who were enrolled in an outpatient PT program, the median improvement in SPPB was 6 points (IQR = 5-7 points), and 85.7% became not frail over a median of 6 weeks. CONCLUSION: Discharge frailty is common following lung transplantation. In most frail patients, an intensive outpatient physical therapy program is associated with improvement in frailty, as assessed by the SPPB.

Methods and Impact of Correcting Heart Rate Data Errors during Exercise in Older Adults.

Heart rate (HR) by time curves could be useful as a measure of treatment fidelity. The purposes were to describe the frequency of common recording irregularities (e.g. errors) observed during exercise, validate a process to correct those errors, and determine whether there is a clinically meaningful benefit to data correction. 1895 exercise sessions from 69 older adults with hip fracture were inspected for errors in the placement of event markers (duration of exercise) and signal artifacts. Marker errors occurred in 33% of the participants, and corrected in 324 sessions. Signal artifacts occurred in 96% of the participants, and eliminated in 702 sessions. Computer code was 85% accurate in detecting signal artifacts, compared to 97% for investigators. HR was significantly higher after correction, but the average change was only 0.69 + 1.20 beats per minute. A HR monitor showing HR by time curves can be used to evaluate treatment fidelity during exercise.

The contribution of leg press and knee extension strength and power to physical function in people with knee osteoarthritis: A cross-sectional study.

The purposes of this study were to 1) determine the additional contributions of leg press and knee extensor power, over and above that of strength, to the performance of physical function tasks in people with knee osteoarthritis, and 2) compare the ability of bilateral leg press to unilateral knee extensor strength and power to predict functional task performance. METHODS: A cross-sectional, exploratory study of 40 individuals with tibiofemoral knee osteoarthritis resulting in moderate impairments in physical function was conducted. Physical function (Get-up and Go, timed stair climb and descent, and five time chair rise) and muscle performance (leg press and knee extension strength and power) were assessed. RESULTS: After controlling for covariates and strength, leg press, but not knee extensor, power explained additional variance in physical function (11% and 21%). Conversely, adding strength to regression models including covariates and power did not consistently improve the prediction of physical function. Additionally, leg press power consistently explained more variance in physical function (44 to 57%) than involved (24 to 34%) or uninvolved (28 to 48%) knee extension power. CONCLUSIONS: Leg press power may be a more functionally relevant measure of muscle performance than knee extension strength in this population. Future studies should investigate the effectiveness of interventions specifically designed to improve leg press power in people with knee osteoarthritis.

Hip abductor strength in people with knee osteoarthritis: A cross-sectional study of reliability and association with function.

BACKGROUND: To investigate the clinical importance of hip abductor (HA) strength in people with knee osteoarthritis (OA), the purposes of this study were to 1) compare the association of HA strength and physical function to that of knee extensor (KE) strength and physical function, and 2) determine the reliability of the assessment of HA strength using a hand-held dynamometer. METHODS: Thirty-five individuals [58 years standard deviation 10 years old] with knee osteoarthritis participated. Physical function was assessed with performance-based [Get-Up and Go (GUG), stair climb and descent (SC), and five times chair rise (CR)] and self-reported (WOMAC function) measures. The relationship between strength and function was assessed using bivariate correlation and hierarchical multiple regression models. Reliability across sessions was assessed in 25 subjects. RESULTS: In the bivariate models, both KE and HA strength were both significantly associated with performance-based measures of function, but not WOMAC function. After controlling for anthropometric factors and KE strength in the hierarchical models, HA made significant independent contributions to the prediction of GUG and SC, but not CR or WOMAC function. The reliability of HA strength was excellent (ICC2, 3=0.94; 95% CI=0.86-0.97), while the minimum detectable change (MDC95) was 0.29Nm/kg (95% CI=0.23-0.41). CONCLUSION: HA strength can be reliably measured and is closely associated with functional performance in people with knee OA. CLINICAL RELEVANCE: These results provide preliminary evidence suggesting that HA strength may be an important rehabilitation target for the conservative management of knee OA.

Longitudinal Evaluation of Stair Walking Biomechanics in Patients with ACL Injury.

PURPOSE: After anterior cruciate ligament (ACL) injury and reconstruction, abnormal biomechanics during daily tasks may have prominent and detrimental long-term consequences on knee joint health. The purpose of this study was to longitudinally evaluate hip and knee joint biomechanics during stair ascent and descent in patients with acute ACL injury and at return to activity after ACL reconstruction. METHODS: Twenty individuals with unilateral ACL injury (age, 20.9 ± 4.4 yr; height, 172.4 ± 7.5 cm; mass, 76.2 ± 12.2 kg) that were scheduled to undergo surgical reconstruction were compared with 20 healthy matched controls (age, 21.7 ± 3.7 yr; height, 173.7 ± 9.9 cm; mass, 76.1 ± 19.7 kg). Lower extremity biomechanics were recorded using three-dimensional motion analysis during stair ascent and descent at two testing sessions (before surgery and at approximately 6 months after surgery or when they were allowed to return to unrestricted physical activity). Time between sessions for healthy participants was matched on the basis of the ACL group. Peak sagittal and frontal plane knee and hip joint angles and moments, joint angles at initial contact, and joint excursions across stance phase were evaluated. RESULTS: The ACL-injured limb of patients experienced smaller knee extension moments than the uninjured limb and healthy controls during stair ascent and descent (P < 0.05) before and 6 months after ACL reconstruction. During stair ascent, ACL patients experienced more extended knee joint positions and less sagittal plane knee joint excursions, coupled with greater frontal plane hip joint excursions (P < 0.05). CONCLUSIONS: Patients with ACL injury experience reductions in knee flexion angle and knee extension moments during stair walking. These alterations were observed both before and after reconstruction, suggesting that early gait retraining interventions may be beneficial in these patients.

The associations between quadriceps muscle strength, power, and knee joint mechanics in knee osteoarthritis: A cross-sectional study.

BACKGROUND: Abnormal knee joint mechanics have been implicated in the pathogenesis and progression of knee osteoarthritis. Deficits in muscle function (i.e., strength and power) may contribute to abnormal knee joint loading. The associations between quadriceps strength, power and knee joint mechanics remain unclear in knee osteoarthritis. METHODS: Three-dimensional motion analysis was used to collect peak knee joint angles and moments during the first 50% of stance phase of gait in 33 participants with knee osteoarthritis. Quadriceps strength and power were assessed using a knee extension machine. Strength was quantified as the one repetition maximum. Power was quantified as the peak power produced at 40-90% of the one repetition maximum. FINDINGS: Quadriceps strength accounted for 15% of the variance in peak knee flexion angle (P=0.016). Quadriceps power accounted for 20-29% of the variance in peak knee flexion angle (P<0.05). Quadriceps power at 90% of one repetition maximum accounted for 9% of the variance in peak knee adduction moment (P=0.05). INTERPRETATION: These data suggest that quadriceps power explains more variance in knee flexion angle and knee adduction moment during gait in knee osteoarthritis than quadriceps strength. Additionally, quadriceps power at multiple loads is associated with knee joint mechanics and therefore should be assessed at a variety of loads. Taken together, these results indicate that quadriceps power may be a potential target for interventions aimed at changing knee joint mechanics in knee osteoarthritis.

Immediate increases in quadriceps corticomotor excitability during an electromyography biofeedback intervention.

The purpose of the study was to determine the effects of EMG-BF on vastus lateralis corticomotor excitability, measured via motor evoked potential (MEP) amplitudes elicited using Transcranial Magnetic Stimulation (TMS) during a maximal voluntary isometric contraction (MVIC). We also determined the effect of EMG-BF on isometric knee extensor strength. Fifteen healthy participants volunteered for this crossover study with two sessions held one-week apart. Participants were randomly assigned to condition order, during which five intervention MVICs were performed with or without EMG-BF. MEP amplitudes were collected with TMS during five knee extension contractions (5% of MVIC) at baseline and again during intervention MVICs within each session. During the control condition, participants were instructed to perform the same number of MVICs without any EMG-BF. Percent change scores were used to calculate the change in peak-to-peak MEP amplitudes that occurred during EMG-BF and Control MVICs compared to the baseline MEPs. Peak knee extension torque was recorded during MVICs prior to TMS for each condition. EMG-BF produced significantly increased MEP change scores and significantly greater torque than the control condition. The results of the current study suggest that EMG-BF may be a viable clinical method for targeting corticomotor excitability.

Effect of age on in vivo oxidative capacity in two locomotory muscles of the leg.

To determine the effects of age and sex on in vivo mitochondrial function of distinct locomotory muscles, the tibialis anterior (TA) and medial gastrocnemius (MG), of young (Y; 24 ± 3 years) and older (O; 69 ± 4) men (M) and women (W) of similar overall physical activity (PA) was compared. In vivo mitochondrial function was measured using phosphorus magnetic resonance spectroscopy, and PA and physical function were measured in all subjects. Overall PA was similar among the groups, although O (n = 17) had fewer daily minutes of moderate-to-vigorous PA (p = 0.001), and slowed physical function (p < 0.05 for all variables), compared with Y (n = 17). In TA, oxidative capacity (V max; mM s(-1)) was higher in O than Y (p < 0.001; Y = 0.90 ± 0.12; O = 1.12 ± 0.18). There was no effect of age in MG (p = 0.5; Y = 0.91 ± 0.17; O = 0.96 ± 0.24), but women had higher oxidative capacity than men (p = 0.007; M = 0.84 ± 0.18; W = 1.03 ± 0.18). In vivo mitochondrial function was preserved in healthy O men and women, despite lower intensity PA and physical function in this group. The extent to which compensatory changes in gait may be responsible for this preservation warrants further investigation. Furthermore, women had higher oxidative capacity in the MG, but not the TA.

The immediate effects of an anterior-to-posterior talar mobilization on neural excitability, dorsiflexion range of motion, and dynamic balance in patients with chronic ankle instability.

CONTEXT: Altered neuromuscular function and decreased dorsiflexion range of motion (DFROM) have been observed in patients with chronic ankle instability (CAI). Joint mobilizations are indicated for restoring DFROM and dynamic postural control, yet it remains unknown if a mobilization can alter neuromuscular excitability in muscles surrounding the ankle. OBJECTIVE: To determine the immediate effects of a Maitland grade III anterior-to-posterior joint mobilization on spinal-reflex and corticospinal excitability in the fibularis longus (FL) and soleus (SOL), DFROM, and dynamic postural control. DESIGN: Single-blinded randomized control trial. SETTING: Research laboratory. PATIENTS: 30 patients with CAI randomized into a mobilization (n = 15) or control (n = 15) group. INTERVENTION: Maitland grade III anterior-to-posterior joint mobilization. MAIN OUTCOME MEASURES: Spinal-reflex excitability was measured with the Hoffmann reflex, while corticospinal excitability was evaluated with transcranial magnetic stimulation. DFROM was measured seated with the knee extended, and dynamic postural control was quantified with the Star Excursion Balance Test. Separate 2 × 2 repeated-measures ANOVAs were performed for each outcome measure. Dependent t tests were used to evaluate individual differences within groups in the presence of significance. RESULTS: Spinal-reflex and corticospinal excitability of the SOL and FL were not altered in the mobilization or control group (P > .05). DFROM increased immediately after the mobilization (P = .05) but not in the control group, while dynamic postural control was unchanged in both groups (P > .05). CONCLUSION: A single joint-mobilization treatment was efficacious at restoring DFROM in participants with CAI; however, excitability of spinal reflex and corticospinal pathways at the ankle and dynamic postural control were unaffected.

Core muscle strengthening's improvement of balance performance in community-dwelling older adults: a pilot study.

To determine the effect of core muscle strengthening on balance in community-dwelling older adults, 24 healthy men and women between 65 and 85 years old were randomized to either exercise (EX; n = 12) or control (CON; n = 12) groups. The exercise group performed a core strengthening home exercise program thrice weekly for 6 wk. Core muscle (curl-up test), functional reach (FR) and Star Excursion Balance Test (SEBT) were assessed at baseline and follow-up. There were no group differences at baseline. At follow-up, EX exhibited significantly greater improvements in curl-up (Cohen's d = 4.4), FR (1.3), and SEBT (>1.9 for all directions) than CON. The change in curl-up was significantly correlated with the change in FR (r = .44, p = .03) and SEBT (r > .61, p ≤ .002). These results suggest that core strengthening should be part of a comprehensive balance-training program for older adults.

Reliability of corticomotor excitability in leg and thigh musculature at 14 and 28 days.

CONTEXT: Alterations in corticomotor excitability are observed in a variety of patient populations, including the musculature surrounding the knee and ankle after joint injury. Active motor threshold (AMT) and motor-evoked-potential (MEP) amplitudes elicited through transcranial magnetic stimulation (TMS) are outcome measures used to assess corticomotor excitability and have been deemed reliable in upper-extremity musculature. However, there are few studies assessing the reliability of TMS measures in lower-extremity musculature. OBJECTIVE: To determine the intersession reliability of AMT and MEP amplitudes over 14 and 28 d in the quadriceps and fibularis longus (FL). DESIGN: Descriptive laboratory study. SETTING: University laboratory PARTICIPANTS: 20 able-bodied volunteers (10 men, 10 women; 22.35 ± 2.3 y, 1.71 ± 0.11 m, 73.61 ± 16.77 kg). MAIN OUTCOME MEASURES: AMT and MEP amplitudes were evaluated at 95%, 100%, 105%, 110%, 120%, 130%, and 140% of AMT in the dominant and nondominant quadriceps and FL. Interclass correlation coefficients (ICCs) were used to assess reliability for absolute agreement and internal consistency between baseline and 2 follow-up sessions at 14 and 28 d postbaseline. Each ICC was fit with the best-fit straight line or parabola to smooth out noise in the observations and best determine if a pattern existed in determining the most reliable MEP value. RESULTS: All muscles yielded strong ICCs between baseline and both time points for AMT. MEPs in both the quadriceps and FL produced varying degrees of reliability, with the greatest reliability demonstrated on day 28 at 130% and 140% of AMT in the quadriceps and FL, respectively. The dominant FL muscle showed a significant pattern; as TMS intensity increased, MEP reliability increased. CONCLUSION: TMS can be used to reliably identify corticomotor alterations after therapeutic interventions, as well as monitor disease progression.

Inter-limb differences in quadriceps strength and volitional activation.

In this crossover study, we wished to determine if normalized inter-limb differences in strength differed from inter-limb differences in voluntary activation at 30°, 70°, and 90° of knee flexion. We also assessed the relationship between inter-limb differences in torque with the inter-limb differences in activation. Twenty-five healthy volunteers were used for final data analyses; the order of leg tested, joint angle, and measurement technique (isokinetic strength, voluntary activation) were randomly assigned. Quadriceps strength was measured isokinetically at 1.05 rad · s(-1), while quadriceps voluntary activation was assessed via the central activation ratio. Absolute values of inter-limb differences for both measures were calculated by subtracting the non-dominant leg values from those of the dominant leg. Inter-limb isokinetic strength differences were greater than inter-limb central activation ratio differences at all joint angles (P = 0.003). Interestingly, inter-limb deficits between measures were not strongly correlated, suggesting that these measurements may be evaluating completely different phenomena within the neuromuscular system. These measurement techniques may provide unique information regarding neuromuscular function, suggesting that researchers and clinicians must utilize information from both techniques to determine the true clinical nature of inter-limb deficits.

Skeletal muscle arteriolar function following myocardial infarction: Analysis of branch-order effects.

Diminished bioavailability of nitric oxide (NO) may impair skeletal muscle arteriolar function after myocardial infarction (MI). We tested the hypotheses that chronic MI induced would diminish 1) endothelial function in large (resting diameter ~75µm) feed arterioles, and 2) functional dilation in feed arterioles, but not smaller arcade (~25µm) or transverse (~15µm) arterioles, in the spinotrapezius muscle of female Sprague-Dawley rats. Additionally, we hypothesized that blockade of NO production with N(G)-nitro-l-arginine methyl ester (l-NAME; 30mg/kg i.v.) would have a greater blunting effect on control rats than MI rats. Endothelial function of the feed arterioles was assessed with an infusion of acetylcholine (1.5µg i.v.) after pretreatment with indomethacin (5mg/kgi.p.). MI blunted the response to acetylcholine in feed arterioles (p=0.037), but did not affect resting or post-contraction diameter at any branching order. l-NAME had similar effects on MI and SHAM rats; the response to acetylcholine was blunted in feed arterioles (p=0.003), resting diameter was diminished in arcade arterioles (p=0.003), and post-contraction diameter was diminished in both arcade arterioles (p=0.03) and transverse arterioles (p=0.05). In conclusion, despite endothelial dysfunction in feed arterioles, functional dilation was not affected by MI in any branching order studied. l-NAME had similar effects on MI and SHAM rats that were branch order-dependent. These branch-order effects should be considered in future studies of the control of blood flow.

Phosphorescence quenching microrespirometry of skeletal muscle in situ.

We have developed an optical method for the evaluation of the oxygen consumption (Vo(2)) in microscopic volumes of spinotrapezius muscle. Using phosphorescence quenching microscopy (PQM) for the measurement of interstitial Po(2), together with rapid pneumatic compression of the organ, we recorded the oxygen disappearance curve (ODC) in the muscle of the anesthetized rats. A 0.6-mm diameter area in the tissue, preloaded with the phosphorescent oxygen probe, was excited once a second by a 532-nm Q-switched laser with pulse duration of 15 ns. Each of the evoked phosphorescence decays was analyzed to obtain a sequence of Po(2) values that constituted the ODC. Following flow arrest and tissue compression, the interstitial Po(2) decreased rapidly and the initial slope of the ODC was used to calculate the Vo(2). Special analysis of instrumental factors affecting the ODC was performed, and the resulting model was used for evaluation of Vo(2). The calculation was based on the observation of only a small amount of residual blood in the tissue after compression. The contribution of oxygen photoconsumption by PQM and oxygen inflow from external sources was evaluated in specially designed tests. The average oxygen consumption of the rat spinotrapezius muscle was Vo(2) = 123.4 ± 13.4 (SE) nl O(2)/cm(3) · s (N = 38, within 6 muscles) at a baseline interstitial Po(2) of 50.8 ± 2.9 mmHg. This technique has opened the opportunity for monitoring respiration rates in microscopic volumes of functioning skeletal muscle.