Comparison of Manual Wheelchair and Pushrim-Activated Power-Assisted Wheelchair Propulsion Characteristics during Common Over-Ground Maneuvers

Pushrim-activated power-assisted wheels (PAPAWs) are assistive technologies that use force sensor data to provide on-demand propulsion assistance to manual wheelchair users. However, available data about kinetic and kinematic of PAPAW use are mainly limited to experiments performed on a treadmill or using a dynamometer. In this work, we performed experiments to gather kinetics of wheelchair propulsion and kinematics of wheelchair motion for a variety of over-ground wheelchair maneuvers with a manual wheelchair with and without PAPAWs. Our findings revealed that using PAPAWs can significantly reduce the propulsion effort and push frequency. Both linear and angular velocities of the wheelchair were significantly increased when using PAPAWs. Less force and push frequency could potentially reduce risk of chronic upper limb injury. Higher linear velocity could be desirable for various daily life activities; however; the increase in the angular velocity could lead to unintended deviations from a desired path. Future research could investigate PAPAW controllers that amplify the desired intentions of users while mitigating any unwanted behaviours.

Augmented feedback for manual wheelchair propulsion technique training in a virtual reality simulator

Background Motor learning of appropriate manual wheelchair propulsion is critical, as incorrect technique elevates risk for upper extremity pain. Virtual reality simulators allow users to practice this complex task in a safe and realistic environment. Additionally, augmented feedback (AF) may be provided in order to optimize learning. The purpose of this study was to investigate the effects of providing AF with various delivery schedules on motor learning and transfer of this skill to over-ground propulsion. Methods Thirty healthy young adults were randomly assigned to three groups. During a virtual reality propulsion training session, the high-frequency AF group received AF in the form of knowledge of performance throughout all propulsion training; the faded AF group received this AF in a faded schedule (high relative frequency of AF early in practice, with relative frequency of AF provision diminishing throughout practice); and the control group underwent training with no AF. Propulsion assessments were performed at baseline and 48 h after practice in both virtual and real environments to measure retention and transfer, respectively. Results Compared to the control group, both feedback groups exhibited significant improvements in contact angle and push frequency in both environments after training. Small, non-significant between-group differences were also found between the high-frequency and faded feedback groups. Conclusion Virtual reality training is an effective learning intervention for acquisition, retention, and transfer of appropriate manual wheelchair propulsion technique when such training includes AF regarding propulsion biomechanics.

A Novel Push-pull Central-lever Mechanism Reduces Peak Forces and Energy-cost Compared to Hand-rim Wheelchair Propulsion During a Controlled Lab-based Experiment

Background: Hand-rim wheelchair propulsion is straining and mechanically inefficient, often leading to upper limb complaints. Previous push-pull lever propulsion mechanisms have shown to perform better or equal in efficiency and physiological strain. Propulsion biomechanics have not been evaluated thus far. A novel push-pull central-lever propulsion mechanism is compared to conventional hand-rim wheelchair propulsion, using both physiological and biomechanical outcomes under low-intensity steady-state conditions on a motor driven treadmill. Methods: In this 5-day (distributed over a maximum of 21 days) between-group experiment, 30 able-bodied novices performed 60 minutes (5x3x4 min) of practice in either the push-pull central lever wheelchair (n=15) or the hand-rim wheelchair (n=15). At the first and final sessions cardiopulmonary strain, propulsion kinematics and force production were determined in both instrumented propulsion mechanisms. Repeated measures ANOVA evaluated between (propulsion mechanism type), within (over practice) and interaction effects. Results: Over practice, both groups significantly improved on all outcome measures. After practice the peak forces during the push and pull phase of lever propulsion were considerably lower compared to those in the handrim push phase (42±10 & 46±10 vs 63±21 N). Concomitantly, energy expenditure was found to be lower as well (263±45 vs 298±59 W), on the other hand gross mechanical efficiency (6.4±1.5 vs 5.9±1.3 %), heart-rate (97±10 vs 98±10 bpm) and perceived exertion (9±2 vs 10±1) were not significantly different between modes.Conclusion: The current study shows the potential benefits of the newly designed push-pull central-lever propulsion mechanism over regular hand rim wheelchair propulsion. The much lower forces and energy expenditure might help to reduce the strain on the upper extremities and thus prevent the development of overuse injury. This proof of concept in a controlled laboratory experiment warrants continued experimental research in wheelchair-users during daily life.

Assessment of Wheelchair Propulsion Performance in an Immersive Virtual Reality Simulator

Maneuvering a wheelchair is an important necessity for the everyday life and social activities of people with a range of physical disabilities. However, in real life, wheelchair users face several common challenges: articulate steering, spatial relationships, and negotiating obstacles. Therefore, our research group has developed a head-mounted display (HMD)-based intuitive virtual reality (VR) stimulator for wheelchair propulsion. The aim of this study was to investigate the feasibility and efficacy of this VR stimulator for wheelchair propulsion performance. Twenty manual wheelchair users (16 men and 4 women) with spinal cord injuries ranging from T8 to L2 participated in this study. The differences in wheelchair propulsion kinematics between immersive and non-immersive VR environments were assessed using a 3D motion analysis system. Subjective data of the HMD-based intuitive VR stimulator were collected with a Presence Questionnaire and individual semi-structured interview at the end of the trial. Results indicated that propulsion performance was very similar in terms of start angle (p = 0.34), end angle (p = 0.46), stroke angle (p = 0.76), and shoulder movement (p = 0.66) between immersive and non-immersive VR environments. In the VR episode featuring an uphill journey, an increase in propulsion speed (p < 0.01) and cadence (p < 0.01) were found, as well as a greater trunk forward inclination (p = 0.01). Qualitative interviews showed that this VR simulator made an attractive, novel impression and therefore demonstrated the potential as a tool for stimulating training motivation. This HMD-based intuitive VR stimulator can be an effective resource to enhance wheelchair maneuverability experiences.