Relationship between energy expenditure and muscular activity patterns in handrim wheelchair propulsion

Abstract

To study the muscular activity pattern adaptations to changes in handrim velocity, independent of external power output, forty wheelchair basketball players with extensive experience in wheelchair propulsion performed wheelchair exercise tests on a motor-driven treadmill in six situations: two exercise levels (60 and 80% of individual VO 2 peak) and three velocities (1.11, 1.67 and 2.22 m/s) with constant power output at each level. During each test, cardiorespiratory, kinematic and EMG data were recorded synchroniously. A two-factor analysis of variance, with “exercise level” and “wheelchair velocity” as the main factors ( p < 0.05), revealed a significant effect on gross mechanical efficiency when velocity was increased. Mechanical work increased significantly during the recovery phase, amounting to 1 3 of the entire mechanical work during the propulsion cycle. Calculation of the concentric muscular work (CMW i.e. muscular activity integrated for each muscle separately as a function of the corresponding angular displacement), gave insight into the energy contribution of each skeletal muscle, used to propel the wheelchair. A close relationship (mean correlation coefficient = +0.84) was demonstrated between metabolic energy expenditure (oxygen consumption) and CMW, indicating that CMW could be a valid standard to analyse individual energy patterns in wheelchair propulsion. Relevance to industry Wheelchairs are probably the most commonly used type of assistive device to enhance mobility of people with a motor impairment. To date, the design of manually propelled wheelchairs has accommodated a wide variety of user requirements. Under certain circumstances, such as in the home, maneuverability is of prime importance; in the outdoor environment, however, stability is equally important, and for sports, speed of movement is a crucial factor. In all situations maximum comfort of the supporting seat, and efficiency of propulsion are desired, but often compromised in the trade-off against “transportation requirements”. Improvement in design of manually propelled wheelchairs over the last decade has been well tuned to the increasing user demands. It is not surprising, therefore, that wheelchairs are using an increasingly larger proportion of budgets allocated to the purchase of assistive devices, both privately and by the government. Manual wheelchair propulsion is based on the use of the upper extremities, which are usually only capable of generating less force than the lower limbs, and with less mechanical efficiency. Further wheelchair design improvement therefore needs to be focused on optimising the use of energy generated by the arms. This study aims to analyse some of the crucial factors in movement during wheelchair propulsion, in order to understand the mechanical efficiency of this type of movement, in this way contributing to the further development of novel wheelchair design.