Effects of Visual Feedback-Induced Variability on Motor Learning of Handrim Wheelchair Propulsion

Abstract

BackgroundIt has been suggested that a higher intra-individual variability benefits the motor learning of wheelchair propulsion. The present study evaluated whether feedback-induced variability on wheelchair propulsion technique variables would also enhance the motor learning process. Learning was operationalized as an improvement in mechanical efficiency and propulsion technique, which are thought to be closely related during the learning process.Methods17 Participants received visual feedback-based practice (feedback group) and 15 participants received regular practice (natural learning group). Both groups received equal practice dose of 80 min, over 3 weeks, at 0.24 W/kg at a treadmill speed of 1.11 m/s. To compare both groups the pre- and post-test were performed without feedback. The feedback group received real-time visual feedback on seven propulsion variables with instruction to manipulate the presented variable to achieve the highest possible variability (1st 4-min block) and optimize it in the prescribed direction (2nd 4-min block). To increase motor exploration the participants were unaware of the exact variable they received feedback on. Energy consumption and the propulsion technique variables with their respective coefficient of variation were calculated to evaluate the amount of intra-individual variability.ResultsThe feedback group, which practiced with higher intra-individual variability, improved the propulsion technique between pre- and post-test to the same extent as the natural learning group. Mechanical efficiency improved between pre- and post-test in the natural learning group but remained unchanged in the feedback group.ConclusionThese results suggest that feedback-induced variability inhibited the improvement in mechanical efficiency. Moreover, since both groups improved propulsion technique but only the natural learning group improved mechanical efficiency, it can be concluded that the improvement in mechanical efficiency and propulsion technique do not always appear simultaneously during the motor learning process. Their relationship is most likely modified by other factors such as the amount of the intra-individual variability.

Effects of variable practice on the motor learning outcomes in manual wheelchair propulsion

“…This is quite a large increase compared to a control group in which mechanical efficiency remained unchanged (4.5% → 4.4%), as well as to the other studies. Participants in a feedback-induced variability study (80 min, low-intensity, 3 weeks) decreased their mechanical efficiency between the pre- and post-test (5.25% → 5.23%) [8]. Pre- and post-test protocol in that study was similar to the present study.…”

“…Natural learning protocols of various durations found an increase in mechanical efficiency. The natural learning group in the experiment of Leving et al (80 min, low-intensity, 3 weeks) increased the mechanical efficiency by 17% between pre- and posttest (5.71% → 6.67%) [8]. Another study, which also offered 80 min of low-intensity wheelchair training (within one day or 3-weeks), found 0% (5.5% → 5.5%) of relative improvement in slower learners and 20% improvement in faster learners (4.9% → 5.9%) [5].…”

“…All variables, except push frequency, were calculated as an average value of all pushes performed during the last minute of each practice block. Modified table from Leving et al [8]; Equations from Vegter et al [4]Propulsion variableUnitDescriptionEquationPush frequencypush/minuteThe number of pushes performed during one minuteN pushes /ΔtBraking torqueNmThe braking torque applied to the handrim with each push. The sum of braking torque exerted on the handrim during coupling and decoupling of the handΣ end (i) :start (i + 1) (Tz · ΔØ)Contact Angledegrees (°)The angle measured along the handrim, where subject’s hand maintained contact with the handrim during each pushØ end (i) −Ø start (i) Max TorqueNmThe maximum torque generated around the wheel axle within a pushMax start(i):end(i)  (Tz)Positive WorkJThe torque around the wheel axle intergrated over the contact angle of the pushΣ start (i) :end (i) (Tz · ΔØ)

Abbreviations: t : time(s); start(i) : start of the current push (sample); end(i) : end of the current push (sample); Tz : torque around wheel axle (Nm); Ø : angle (rad)

…”

“…This sort of variability is not present when propelling a wheelchair on a treadmill at a steady velocity in a laboratory. A study that attempted to increase variability on a treadmill, using visual feedback on the propulsion technique variables, found improvements in propulsion technique but no improvement in mechanical efficiency [8]. Authors suggested that the addition of an extra constraint, which was visual feedback, may have compromised the optimization of the energy efficiency of wheelchair propulsion.…”

“…While the feedback-induced variability required participants to ‘learn to be variable’, the current study aimed at facilitating ‘learning by being variable’. The participants in the present study were asked to perform tasks that require and stimulate variability, but contrary to the feedback-induced variability study [8], they were not explicitly asked to be variable. The tasks chosen for the current protocol were five isolated wheelchair skill tasks (such as a slalom or a sprint) and wheelchair basketball.…”