Human Weight Compensation With a Backdrivable Upper-Limb Exoskeleton: Identification and Control

Active exoskeletons are promising devices for improving rehabilitation procedures in patients and preventing musculoskeletal disorders in workers. In particular, exoskeletons implementing human limb’s weight support are interesting to restore some mobility in patients with muscle weakness and help in occupational load carrying tasks. The present study aims at improving weight support of the upper limb by providing a weight model considering joint misalignments and a control law including feedforward terms learned from a prior population-based analysis. Three experiments, for design and validation purposes, are conducted on a total of 65 participants who performed posture maintenance and elbow flexion/extension movements. The introduction of joint misalignments in the weight support model significantly reduced the model errors, in terms of weight estimation, and enhanced the estimation reliability. The introduced control architecture reduced model tracking errors regardless of the condition. Weight support significantly decreased the activity of antigravity muscles, as expected, but increased the activity of elbow extensors because gravity is usually exploited by humans to accelerate a limb downwards. These findings suggest that an adaptive weight support controller could be envisioned to further minimize human effort in certain applications.

The Excitability of Ipsilateral Motor Evoked Potentials Is Not Task-specific and Spatially Distinct From the Contralateral Motor Hotspot

ObjectiveThe role of ipsilateral descending motor pathways in voluntary movement of humans is still a matter of debate. Few studies have examined the task dependent modulation of ipsilateral motor evoked potentials (iMEPs). Here, we determined the location of upper limb biceps brachii (BB) representation within the ipsilateral primary motor cortex. MethodsMR-navigated transcranial magnetic stimulation mapping of the dominant hemisphere was undertaken with twenty healthy participants who made tonic unilateral, bilateral homologous or bilateral antagonistic elbow flexion-extension voluntary contractions. Map center of gravity (CoG) and area for each BB were obtained. ResultsThe map CoG of the ipsilateral BB was located more anterior-laterally than those of the contralateral BB within the primary motor cortex. However different tasks had no effect on either the iMEP CoG location or the size. ConclusionOur data suggests that ipsilateral and contralateral MEP might originate in distinct adjacent neural populations in the primary motor cortex, independent of task dependence.

Characterization of stroke-related upper limb motor impairments across various upper limb activities by use of kinematic core set measures

Background Upper limb kinematic assessments provide quantifiable information on qualitative movement behavior and limitations after stroke. A comprehensive characterization of spatiotemporal kinematics of stroke subjects during upper limb daily living activities is lacking. Herein, kinematic expressions were investigated with respect to different movement types and impairment levels for the entire task as well as for motion subphases. Method Chronic stroke subjects with upper limb movement impairments and healthy subjects performed a set of daily living activities including gesture and grasp movements. Kinematic measures of trunk displacement, shoulder flexion/extension, shoulder abduction/adduction, elbow flexion/extension, forearm pronation/supination, wrist flexion/extension, movement time, hand peak velocity, number of velocity peaks (NVP), and spectral arc length (SPARC) were extracted for the whole movement as well as the subphases of reaching distally and proximally. The effects of the factors gesture versus grasp movements, and the impairment level on the kinematics of the whole task were tested. Similarities considering the metrics expressions and relations were investigated for the subphases of reaching proximally and distally between tasks and subgroups. Results Data of 26 stroke and 5 healthy subjects were included. Gesture and grasp movements were differently expressed across subjects. Gestures were performed with larger shoulder motions besides higher peak velocity. Grasp movements were expressed by larger trunk, forearm, and wrist motions. Trunk displacement, movement time, and NVP increased and shoulder flexion/extension decreased significantly with increased impairment level. Across tasks, phases of reaching distally were comparable in terms of trunk displacement, shoulder motions and peak velocity, while reaching proximally showed comparable expressions in trunk motions. Consistent metric relations during reaching distally were found between shoulder flexion/extension, elbow flexion/extension, peak velocity, and between movement time, NVP, and SPARC. Reaching proximally revealed reproducible correlations between forearm pronation/supination and wrist flexion/extension, movement time and NVP. Conclusion Spatiotemporal differences between gestures versus grasp movements and between different impairment levels were confirmed. The consistencies of metric expressions during movement subphases across tasks can be useful for linking kinematic assessment standards and daily living measures in future research and performing task and study comparisons. Trial registration: ClinicalTrials.gov Identifier NCT03135093. Registered 26 April 2017, https://clinicaltrials.gov/ct2/show/NCT03135093.

Aerobic Exercise Combination Intervention to Improve Physical Performance Among the Elderly: A Systematic Review

The benefits of aerobic exercise for the elderly are well-known. They extend beyond cardiovascular changes and can reduce the inactivity-induced loss of strength, mobility, balance, and endurance that are vital for the safe performance of daily activities in older adults. However, the benefits of combined aerobic exercise with other exercises such as strength/resistance, multi-component and aerobic exercise remain unknown. The purpose of this study is to examine the effects of combined aerobic exercise on physical performance among the elderly, as opposed to single aerobic exercise. We searched four databases of SCOPUS, PubMed, EBSCOhost, and CINAHL Plus to find 18 articles that met criteria. Data was extracted using PICOs extraction tool and summarized using a narrative synthesis approach. Studies have shown that aerobics combined resistance/strength training (CEX), multi-component training (ME), and dance combined training has positive and significant effects on the physical performance (upper body strength and lower body strength, dynamic balance, fall risk, mobility, gait, agility, flexibility) of the elderly. CEX had additional benefits compared to aerobic training (AER) and resistance/strength training (RES) in gait speed, lower limb strength, and trunk fat. Furthermore, CEX was more effective than AER in improving sitting and stretching, elbow flexion, knee flexion, shoulder flexion and stretching, strength and body fat, function reach test, 30-s chair standing test and 6-min walking test, self-evaluation of body function. Therefore, the combination of multiple components contributes to the overall improvement in physical fitness of the elderly, thus preventing them from losing balance and reducing susceptibility to injury.Clinical Trial Registration: [https://www.crd.york.ac.uk/prospero/#recordDetails], identifier [CRD42021213147].

Surgical Results of Chronic Distal Biceps Ruptures: A Systematic Review

Background: Distal biceps tendon tears can cause weakness and fatigue with activities requiring elbow flexion and supination. Surgical management of chronic tears (>21 days) is not well described in the literature. Purpose: To determine the clinical outcomes of chronic distal biceps repairs and reconstructions. Study Design: Systematic review; Level of evidence, 4. Methods: We performed a search of Medline (PubMed and Ovid), EMBASE, CINAHL physical therapy, Cochrane Database of Systematic Reviews and Central Register of Controlled Trials, and PubMed Central from inception until September 29, 2020, to identify articles on chronic distal biceps ruptures. The inclusion criteria were studies with at least 1 outcome measure and 10 patients with chronic distal biceps ruptures treated surgically. The quality of the included studies was assessed with the methodological index for nonrandomized studies (MINORS) score. Functional outcomes and complications were reviewed. Results: A total of 12 studies were included after systematic database screenings. The MINORS scores ranged from 5 to 19. There were a total of 1704 distal biceps ruptures, of which 1270 were acute and 434 were chronic. Average follow-up time was 12 months to 5.1 years. Single-incision (n = 3), 2-incision (n = 2), or both (n = 6) surgical techniques were used in these studies. Four studies described the use of autografts, and 4 articles used allografts in the chronic repair. Range of motion, function, and strength outcomes were similar when compared with the contralateral arm. Pain was reduced to minimal levels. Main postoperative complications were of paresthesia (specifically to the lateral antebrachial cutaneous nerve), which were temporary in 69.1% of cases. Conclusion: The results of this review indicate that surgical management of chronic distal biceps ruptures demonstrates improvement in outcomes including pain reduction and functional ability. Although there may be a slightly higher immediate complication rate, the functional outcomes remain comparable with those seen in the patient population with acute distal biceps.

Biceps Tenotomy Vs Tenodesis in Patients Younger Than 50, Systematic Review

Purpose: The objective of this meta-analysis was to offer an up-to-date comparison of clinical outcomes of tenotomy and tenodesis in the surgical treatment of LHB tendinopathy in patients under the age of 50. Methods: A literature search was conducted in EMBASE, PubMed/Medline and the Cochrane database from January 2010 to Dec 2020. All studies that compared the clinical results of LHB tenotomy and tenodesis were included. Results: The Meta- analysis data were from nine studies that comprised 669 participants who had LHB tenotomy or tenodesis with or without other shoulder surgeries (mainly rotator cuff repairs). There were no clinically significant changes in the Constant score, the American Shoulder and Elbow Society Score, shoulder pain, elbow flexion strength loss, or forearm supination strength when tenodesis and tenotomy were compared in randomized studies. Patients who have tenodesis were less likely to develop a Popeye deformity. Conclusion: In a meta-analysis, patients who had a tenotomy were more likely to have a Popeye deformity. There is no evidencebased benefit of LHB tenodesis over tenotomy in terms of shoulder function, shoulder discomfort, or biceps-related strength, according to a large number of studies. It's unknown whether LHB tenodesis is beneficial to some patient populations, such as children. Keywords: Biceps, Tenotomy, Tenodesis, Rotator cuff, Meta-analysis

Brachialis Muscle Activity Can Be Measured With Surface Electromyography: A Comparative Study Using Surface and Fine-Wire Electrodes

Muscle activities of the elbow flexors, especially the brachialis muscle (BR), have been measured with intramuscular electromyography (EMG) using the fine-wire electrodes. It remains unclear whether BR activity can be assessed using surface EMG. The purpose of this study was to compare the EMG patterns of the BR activity recorded during elbow flexion using surface and fine-wire electrodes and to determine whether surface EMG can accurately measure the BR activity. Six healthy men were asked to perform two tasks—a maximum isometric voluntary contractions (MVICs) task and an isotonic elbow-flexion task without lifting any weight. The surface and intramuscular EMG were simultaneously recorded from the BR and the long and short heads of the biceps brachii muscle (BBLH and BBSH, respectively). The locations of the muscles were identified and marked under ultrasonographic guidance. The peak cross-correlation coefficients between the EMG signals during the MVICs task were calculated. For the isotonic elbow-flexion task, the EMG patterns for activities of each muscle were compared between the surface and the fine-wire electrodes. All cross-correlation coefficients between the surface EMG signals from the muscles were lower than 0.3. Furthermore, the EMG patterns of the BR activity were not significantly different between the surface and the fine-wire electrodes. The BR has different EMG pattern from the BBLH and the BBSH. The BR activity, conventionally measured with intramuscular EMG, can be accurately accessed with surface EMG during elbow flexion performed without lifting any weight, independent from the BBLH and BBSH activities.

Kinetic and Kinematic Characteristics of Proficient and Non-Proficient 2-Point and 3-Point Basketball Shooters

The purpose of this study was to examine kinetic and kinematic characteristics of various types of 2-point and 3-point basketball shooting approaches and determine which variables have the greatest contribution in discriminating proficient (PRO) from non-proficient (N-PRO) shooters. While standing on a force plate, twenty-nine recreationally active males performed a total of 1740 shots by utilizing stationary and step-in shooting approaches. Two high-definition cameras were used to simultaneously capture kinematic parameters of shooting motions. The type of shooting approach showed as a non-influential factor. During the preparatory phase of the shooting motion, PRO 2-point shooters demonstrated higher elbow and basketball height placements, greater flexion in the shoulder and elbow joints while attaining greater release and entry ball angles during the release phase. PRO 3-point shooters demonstrated greater elbow flexion, higher basketball placement, and less hip flexion during the preparatory phase while attaining greater heel, release, and trajectory heights during the release phase. When entered into a full-model discriminant function analysis, elbow angle, elbow height, and release angle variables correctly classified PRO from N-PRO 2-point shooters in 62.1% of cases and hip angle, heel height, and elbow angle variables correctly classified PRO from N-PRO 3-point shooters in 81.6% of cases.