Early motor learning changes in upper-limb dynamics and shoulder complex loading during handrim wheelchair propulsion

Abstract

BackgroundTo propel in an energy-efficient manner, handrim wheelchair users must learn to control the bimanually applied forces onto the rims, preserving both speed and direction of locomotion. Previous studies have found an increase in mechanical efficiency due to motor learning associated with changes in propulsion technique, but it is unclear in what way the propulsion technique impacts the load on the shoulder complex. The purpose of this study was to evaluate mechanical efficiency, propulsion technique and load on the shoulder complex during the initial stage of motor learning.Methods15 naive able-bodied participants received 12-minutes uninstructed wheelchair practice on a motor driven treadmill, consisting of three 4-minute blocks separated by two minutes rest. Practice was performed at a fixed belt speed (v = 1.1 m/s) and constant low-intensity power output (0.2 W/kg). Energy consumption, kinematics and kinetics of propulsion technique were continuously measured. The Delft Shoulder Model was used to calculate net joint moments, muscle activity and glenohumeral reaction force.ResultsWith practice mechanical efficiency increased and propulsion technique changed, reflected by a reduced push frequency and increased work per push, performed over a larger contact angle, with more tangentially applied force and reduced power losses before and after each push. Contrary to our expectations, the above mentioned propulsion technique changes were found together with an increased load on the shoulder complex reflected by higher net moments, a higher total muscle power and higher peak and mean glenohumeral reaction forces.ConclusionsIt appears that the early stages of motor learning in handrim wheelchair propulsion are indeed associated with improved technique and efficiency due to optimization of the kinematics and dynamics of the upper extremity. This process goes at the cost of an increased muscular effort and mechanical loading of the shoulder complex. This seems to be associated with an unchanged stable function of the trunk and could be due to the early learning phase where participants still have to learn to effectively use the full movement amplitude available within the wheelchair-user combination. Apparently whole body energy efficiency has priority over mechanical loading in the early stages of learning to propel a handrim wheelchair.

Magnetic Resonance-Compatible Arm-Crank Ergometry: A New Platform Linking Whole-Body Calorimetry to Upper-Extremity Biomechanics and Arm Muscle Metabolism

“…Therefore, the outcome of the ratio of whole arm power-output and whole-body energy expenditure during ACT execution was skewed towards a higher ratio post-training ( Table 2). This particular nding was similar to results of a recent study of the effect of a low-intensity training intervention in manual wheelchair propulsion in naïve subjects (22). Speci cally, the authors reported improvement of gross ME of wheelchair propulsion concomitant with opposite rather than parallel changes in power-output over time for the biceps and brachialis muscles of the upper arm.…”

“…Speci cally, the authors reported improvement of gross ME of wheelchair propulsion concomitant with opposite rather than parallel changes in power-output over time for the biceps and brachialis muscles of the upper arm. Notably, power-output of the biceps muscle was found to increase, not decrease with training (22) Together, these studies indicate that ndings of increased ME after training of any form of upper body exercise based solely on whole body measurements of oxygen consumption should be interpreted with caution. The new experimental platform for upper-extremity cyclic exercise presented in this report uniquely affords to gather complementary data on energy expenditure in upper-extremity muscles to strengthen objective evaluation of the outcome of upper body training interventions.…”

Shoulder kinetics and ultrasonography changes after performing a high-intensity task in spinal cord injury subjects and healthy controls

“…The differences in shoulder forces seen with increasing resistance between experienced and novice MWUs is consistent with the literature on differences with the experiences and motor learning that occurs, demonstrating increased tangential forces with experience. 41 No differences were evident in the ultrasound parameters of MWUs before and after the propulsion test. Several studies have assessed the shoulder by ultrasonography before and after performing a specific task, yet the task performed did not coincide in any of these, including our present study.…”

Measuring Handrim Wheelchair Propulsion in the Lab: A Critical Analysis of Stationary Ergometers

“…Moreover, they can be expanded with extra equipment that is necessary for biomechanics and motor learning studies. Indeed, motor learning during overground propulsion [115], [116], and treadmill [81], [114], [117] or ergometer propulsion [77] show somewhat similar results. However, in overground and ergometer propulsion, it is possible for the self-selected speed to change during motor learning.…”