Skill acquisition of manual wheelchair propulsion due to implicit motor learning

Objective. To study wheelchair skill acquisition in handrim wheelchair propulsion on a motor-driven treadmill in able-bodied male novices to simulate early rehabilitation. Major content of paper. Mechanical efficiency (ME) is a measure to evaluate the performance of the wheelchair-user combination and is sensitive to changes in the wheelchair-user interface as well as to skill acquisition. ME is defined as the ratio between external power output and the energy consumption. When the wheelchair configuration is kept constant, changes in efficiency can be attributed to the user. Changes in propulsion technique due to continued, often implicit, motor learning account for a higher ME. The changes in ME and propulsion technique due to the implicit motor learning process were studied in a three week learning experiment (3 times a week for 8 min at 0.21 W/kg) with 9 able-bodied subjects, novice to handrim wheelchair propulsion, simulating early rehabilitation. No instructions on technique or feedback on results were given. Methods. Instrumented wheels allowed for measuring three-dimensional forces and torques on the handrim in real life situations. Combining these wheels during treadmill wheelchair propulsion with analysis of energy cost gives the possibility to compare physiological parameters to the biomechanics of wheelchair propulsion over the learning period. From the force data different propulsion technique parameters e.g. timing (frequency, push time, angle) and force application (force magnitude and direction, periods of negative power) were derived. Results. Already within the first 12 minutes changes in timing and force production occurred. Peak torques were reduced, work per cycle increased, while push frequency decreased, at a stable power output and speed of the treadmill. Over the three weeks of practice propulsion technique kept changing and was accompanied with an increase in ME. Conclusion. Results suggest skill acquisition because of motor learning by all users in the group. The rise in ME seems logically related to propulsion technique, but is not yet fully understood. More insight in motor learning and skill acquisition will contribute to understanding and optimizing rehabilitation strategies in the light of wheelchair provision in early rehabilitation.