Changes in brain functional connectivity and muscle strength independent of elbow flexor atrophy following upper limb immobilization in young females.

Muscle disuse induces a decline in muscle strength that exceeds the rate and magnitude of muscle atrophy, suggesting that factors beyond the muscle contribute to strength loss. The purpose of this study was to characterize changes in the brain and neuromuscular system in addition to muscle size following upper limb immobilization in young females. Using a within-participant, unilateral design, 12 females (age: 20.6 ± 2.1 years) underwent 14 days of upper arm immobilization using an elbow brace and sling. Bilateral measures of muscle strength (isometric and isokinetic dynamometry), muscle size (magnetic resonance imaging), voluntary muscle activation capacity, corticospinal excitability, cortical thickness and resting-state functional connectivity were collected before and after immobilization. Immobilization induced a significant decline in isometric elbow flexion (-21.3 ± 19.2%, interaction: P = 0.0440) and extension (-19.9 ± 15.7%, interaction: P = 0.0317) strength in the immobilized arm only. There was no significant effect of immobilization on elbow flexor cross-sectional area (CSA) (-1.2 ± 2.4%, interaction: P = 0.466), whereas elbow extensor CSA decreased (-2.9 ± 2.9%, interaction: P = 0.0177) in the immobilized arm. Immobilization did not differentially alter voluntary activation capacity, corticospinal excitability, or cortical thickness (P > 0.05); however, there were significant changes in the functional connectivity of brain regions related to movement planning and error detection (P < 0.05). This study reveals that elbow flexor strength loss can occur in the absence of significant elbow flexor muscle atrophy, and that the brain represents a site of functional adaptation in response to upper limb immobilization in young females.

Resting-state Functional Connectivity of the Motor and Cognitive Areas is Preserved in Masters Athletes.

Aging is characterized by a decline in physical and cognitive functions, often resulting in decreased quality of life. Physical activity has been suggested to potentially slow down various aspects of the aging process, a theory that has been supported by studies of Masters Athletes (MA). For example, MA usually have better cognitive and physical functions than age-matched sedentary and healthy older adults (OA), making them a valuable model to gain insights into mechanisms that promote physical and cognitive function with aging. The purpose of this study was to identify differences in resting-state functional connectivity (rs-FC) of motor and cognitive regions between MA and OA and determine if these differences in the resting brain are associated with differences in cognitive and physical performance between groups. Fifteen MA (9 males) and 12 age-matched OA (six males) were included. rs-FC images were compared to identify significant between-groups differences in brain connectivity. There was higher connectivity between the cognitive and motor networks for the OA group, whereas the MA group had stronger connectivity between different regions within the same network, both for the cognitive and the motor networks. These results are in line with the literature suggesting that aging reduces the segregation between functional networks and causes regions within the same network to be less strongly connected. High-level physical activity practiced by the MA most likely contributes to attenuating aging-related changes in brain functional connectivity, preserving clearer boundaries between different functional networks, which may ultimately favor maintenance of efficient cognitive and sensorimotor processing.

Reorganization of Brain Resting-state Functional Connectivity Following 14 Days of Elbow Immobilization in Young Females.

Limb immobilization is known to cause significant decreases in muscle strength and muscle mass as early as two days following the onset of immobilization. However, the decline in strength surpasses the decline in muscle mass, suggesting that factors in addition to muscle loss, such as neuroplasticity, contribute to the decrease in force production. However, little is known regarding immobilization-induced neural changes, although sensorimotor regions seem to be the most affected. The present study aimed to determine whether brain functional organization is altered following 14 days of unilateral elbow immobilization. Functional organization was quantified using resting-state functional connectivity, a measure of the synchronicity of the spontaneous discharge of different brain regions at rest. Data was obtained from twelve healthy young females before and after completing the immobilization period. A seed-to-voxel analysis was performed using seeds associated with cortical, subcortical, and cerebellar sensorimotor regions of the brain. The results showed changes predominantly involving cerebellar connectivity. For example, the immobilization period caused a decrease in connectivity between the motor cerebellar region of the immobilized arm and the left temporal lobe, and an increase between the same cerebellar region and the supplementary motor area. Overall, changes in connectivity occurred in regions typically associated with error detection and motor learning, suggesting a potential functional reorganization of the brain within 14 days of elbow immobilization.

Upregulation of the parietal cortex improves freezing of gait in Parkinson's disease.

BACKGROUND The posterior parietal cortex (PPC) is a key brain area for visuospatial processing and locomotion. It has been repetitively shown to be involved in the neural correlates of freezing of gait (FOG), a common symptom of Parkinson's disease (PD). However, current neuroimaging modalities do not allow to precisely determine the role of the PPC during real FOG episodes. OBJECTIVES The purpose of this study was to modulate the PPC cortical excitability using repetitive transcranial magnetic stimulation (rTMS) to determine whether the PPC contributes to FOG or compensates for dysfunctional neural networks to reduce FOG. METHODS Fourteen participants with PD who experience freezing took part in a proof of principle study consisting of three experimental sessions targeting the PPC with inhibitory, excitatory, and sham rTMS. Objective FOG outcomes and cortical excitability measurements were acquired before and after each stimulation protocol. RESULTS Increasing PPC excitability resulted in significantly fewer freezing episodes and percent time frozen during a FOG-provoking task. This reduction in FOG most likely emerged from the trend in PPC inhibiting the lower leg motor cortex excitability. CONCLUSION Our results suggest that the recruitment of the PPC is linked to less FOG, providing support for the beneficial role of the PPC upregulation in preventing FOG. This could potentially be linked to a reduction of the cortical input burden on the basal ganglia prior to FOG. Excitatory rTMS interventions targeting the PPC may have the potential to reduce FOG.

Same-Day Discharge Following Total Joint Arthroplasty: Examining Trends, Discharge Dispositions, and Complications Over Time.

Administrative database studies have reported on the safety of same-day discharge (SDD) following total joint arthroplasty (TJA); however, most patient cohorts have been defined by length of stay (LOS), and the proportion discharged directly home remains unknown. The purpose of this investigation was to (1) determine common dispositions for patients undergoing SDD TJA; (2) understand changes in discharge disposition over time; and (3) determine the safety of SDD TJA, stratified by discharge disposition. The PearlDiver Database was reviewed for patients who underwent SDD TJA (LOS of 0 days) from 2011 to 2016. Patients were stratified by discharge disposition, and rates and complications following SDD TJA were assessed accordingly. Chi-square analysis was performed to compare demographics and complications between patient groups stratified by disposition. From 2011 to 2016, there was an exponential increase in the annual rate of SDD TJA from 0.95% to 20.5%, respectively; however, the annual proportion of patients discharged directly home remained unchanged (approximately 68%), with the remaining discharged directly to an alternate care facility, most commonly inpatient rehabilitation. Patients discharged to an alternate facility were significantly older (P<.001), had significantly higher comorbidity scores (P<.001), and had significantly more complications (P<.001) than those patients discharged directly home. Although the annual rate of SDD TJA is increasing, up to one-third of patients are not discharged directly home-a proportion unchanged over time. Moving forward, administrative database studies examining SDD TJA must account for discharge disposition; moreover, there is a need to understand the practice of SDD TJA to an alternate care facility. [Orthopedics. 2020;43(4):204-208.].

The lower trapezius transfer: a systematic review of biomechanical data, techniques, and clinical outcomes.

BACKGROUND: Lower trapezius (LT) transfers were originally described to restore external rotation (ER) in the management of brachial plexus palsy; however, there is recent interest in the role of this transfer to restore shoulder function, specifically ER, in patients with a massive irreparable rotator cuff tear (RCT). The purpose of this systematic review is to summarize the current literature pertaining to LT transfers, including biomechanics, techniques, and clinical outcomes for patients with brachial plexus palsy and massive RCTs. METHODS: MEDLINE, EMBASE, and PubMed were searched for biomechanical and clinical studies, as well as technique articles. Four biomechanical studies reported on moment arms, range of motion (ROM), and force vectors. Seven clinical studies reported postoperative ROM and functional outcomes, and weighted mean improvements in ROM were calculated. RESULTS: Overall, 18 studies were included, and then subdivided into 3 themes: biomechanical, technique, and clinical. Biomechanical studies comparing LT and latissimus dorsi (LD) transfers observed an overall larger moment arm in abduction and ER in adduction for the LT transfer, with similar results in forward elevation. Clinical studies noted significant improvement in shoulder function following the LT transfer, including ROM and functional outcome scores. There were several described techniques for performing the LT transfer, including arthroscopically assisted and open approaches, and the use of both allograft and autograft augmentation. CONCLUSION: This study suggests that the LT transfer is generally safe, and the clinical and biomechanical data to date support the use of the LT transfer for restoration of function in these challenging patient populations.