Effects of backrest positioning and gear ratio on nondisabled subjects' handcycling sprinting performance and kinematics
Journal of rehabilitation research and development
Backrest position is a significant parameter in handcycling that one must consider when seeking to optimize the user-to-chair interface. We studied the effects of backrest position on handcycle propulsion kinematics. Ten nondisabled participants with no handcycle propulsion experience repeated an 8 s sprint with three backrest positions (backrest angle between 45°a nd 50° to the horizontal, backrest angle between 65° and 70° to the horizontal, and without backrest) and three gear ratios (GRs)
... gear ratios (GRs) (GR22/21 = low, GR32/21 = medium, and GR44/21 = high). We used three-dimensional movement analysis to calculate the average maximal velocity, cycle frequency, and angle parameters for the arms and trunk. Our results showed statistically higher trunk flexion/extension (p < 0.001) and maximal velocity (p < 0.001) when a backrest was not used. Moreover, these differences were accentuated as the GR increased (GR44/21). Our results suggest that handcycle users with unimpaired upper-body and trunk function can improve handcycling performance by removing the backrest. Nevertheless, future studies on specific groups of subjects with spinal cord injury should be conducted. Abbreviations: Ad/Ab = adduction/abduction, ANOVA = analysis of variance, AP = arm power, ATP = arm and trunk power, B45 = backrest angle adjusted to between 45° and 50° to horizontal, B65 = backrest angle adjusted to between 65° and 70° to horizontal, C7 = seventh cervical (vertebra), F/E = flexion/extension, GR = gear ratio, L3 = third lumbar (vertebra), Ri/Re = internal/ external rotation, ROM = range of motion, SCI = spinal cord injury, SD = standard deviation, WB = without backrest.