Effects of wrist posture and stabilization on precision grip force production and muscle activation patterns.

Most of the power for generating forces in the fingers arises from muscles located in the forearm. This configuration maximizes finger joint range of motion while minimizing finger mass and inertia. The resulting multiarticular arrangement of the tendons, however, complicates independent control of the wrist and the digits. Actuating the wrist impacts sensorimotor control of the fingers and vice versa. The goal of this study was to systematically investigate interactions between isometric wrist and digit control. Specifically, we examined how the need to maintain a specified wrist posture influences precision grip. Fifteen healthy adults produced maximum precision grip force at 11 different wrist flexion/extension angles, with the arm supported, under two conditions: 1) the participant maintained the desired wrist angle while performing the precision grip and 2) a robot maintained the specified wrist angle. Wrist flexion/extension posture significantly impacted maximum precision grip force (P < 0.001), with the greatest grip force achieved when the wrist was extended 30° from neutral. External wrist stabilization by the robot led to a 20% increase in precision grip force across wrist postures. Increased force was accompanied by increased muscle activation but with an activation pattern similar to the one used when the participant had to stabilize their wrist. Thus, simultaneous wrist and finger requirements impacted performance of an isometric finger task. External wrist stabilization can promote increased precision grip force resulting from increased muscle activation. These findings have potential clinical significance for individuals with neurologically driven finger weakness, such as stroke survivors.NEW & NOTEWORTHY We explored the interdependence between wrist and fingers by assessing the influence of wrist posture and external stabilization on precision grip force generation. We found that maximum precision grip force occurred at an extended wrist posture and was 20% greater when the wrist was Externally Stabilized. The latter resulted from amplification of muscle activation patterns from the Self-Stabilized condition rather than adoption of new patterns exploiting external wrist stabilization.

Estimation of Energy Expenditure in Wheelchair-Bound Spinal Cord Injured Individuals Using Inertial Measurement Units.

A healthy lifestyle reduces the risk of cardio-vascular disease. As wheelchair-bound individuals with spinal cord injury (SCI) are challenged in their activities, promoting and coaching an active lifestyle is especially relevant. Although there are many commercial activity trackers available for the able-bodied population, including those providing feedback about energy expenditure (EE), activity trackers for the SCI population are largely lacking, or are limited to a small set of activities performed in controlled settings. The aims of the present study were to develop and validate an algorithm based on inertial measurement unit (IMU) data to continuously monitor EE in wheelchair-bound individuals with a SCI, and to establish reference activity values for a healthy lifestyle in this population. For this purpose, EE was measured in 30 subjects each wearing four IMUs during 12 different physical activities, randomly selected from a list of 24 activities of daily living. The proposed algorithm consists of three parts: resting EE estimation based on multi-linear regression, an activity classification using a k-nearest-neighbors algorithm, and EE estimation based on artificial neural networks (ANNs). The mean absolute estimation error for the ANN-based algorithm was 14.4% compared to indirect calorimeter measurements. Based on reference values from the literature and the data collected within this study, we recommend wheeling 3 km per day for a healthy lifestyle in wheelchair-bound SCI individuals. Combining the proposed algorithm with a recommendation for physical activity provides a powerful tool for the promotion of an active lifestyle in the SCI population, thereby reducing the risk for secondary diseases.

Physical therapy is targeted and adjusted over time for the rehabilitation of locomotor function in acute spinal cord injury interventions in physical and sports therapy.

STUDY DESIGN: Prospective observational multicenter study. OBJECTIVES: Investigation of content, duration and adjustment of physical therapy for the rehabilitation of ambulation in acute spinal cord injury (SCI). SETTING: European Multicenter Study of SCI (EMSCI). METHODS: Physical therapy interventions during acute in-patient rehabilitation of eighty incomplete SCI patients (AIS B, C, D all lesion levels) were recorded using the SCI - Intervention Classification System. Mobility was documented using the Spinal Cord Independence Measurement (SCIM III), demographics and clinical data were retrieved from the EMSCI database. RESULTS: Overall recovery of locomotor function was categorized into three outcome groups (G1-G3). Of 76 initial wheelchair-using patients, 53.9% remained wheelchair user (G1), 25% regained moderate (G2) and 21.1% good walking (G3) capability. Strength training was the most frequently applied intervention of body function/-structure across all outcome groups (about 30% of all interventions), while interventions focusing on muscle tone and respiration were predominantly applied in wheelchair-dependent patients. Activity-focused interventions of transfer, transition, sitting were trained most intensively in outcome group G1, while walking and swimming were increasingly trained in patients with moderate and good walking outcomes. Physical therapy interventions of assistive and active trainings as well as corresponding training environments changed with the recovery of locomotor function. CONCLUSIONS: Physical therapy of locomotor function is targeted to individual patients' conditions and becomes adjusted to the progress of ambulation. Although the involved clinical sites were not following explicitly standardized rehabilitation programs, common patterns can be discerned which may form the basis of prospective standardized programs.