Crank length alters kinematics and kinetics, yet not the economy of recumbent handcyclists at constant handgrip speeds

Abstract

Handcycling performance is dependent on the physiological economy of the athlete; however, handbike configuration and the biomechanical interaction between the two are also vital. The purpose of this study was to examine the effect of crank length manipulations on physiological and biomechanical aspects of recumbent handcycling performance in highly trained recumbent handcyclists at a constant linear handgrip speed and sport-specific intensity. Nine competitive handcyclists completed a 3-minute trial in an adjustable recumbent handbike in four crank length settings (150, 160, 170 & 180 mm) at 70% peak power output. Handgrip speed was controlled (1.6 m•s −1) across trials with cadences ranging from 102 to 85 rpm. Physiological economy, heart rate, and ratings of perceived exertion were monitored in all trials. Handcycling kinetics were quantified using an SRM (Schoberer Rad Messtechnik) powermeter, and upper limb kinematics were determined using a 10-camera VICON motion capture system. Physiological responses were not significantly affected by crank length. However, greater torque was generated (P < .0005) and peak torque occurred earlier during the push and pull phase (P ≤ .001) in longer cranks. Statistical parametric mapping revealed that the timing and orientation of shoulder flexion, shoulder abduction, and elbow extension were significantly altered in different crank lengths. Despite the biomechanical adaptations, these findings suggest that at constant handgrip speeds (and varying cadence) highly trained handcyclists may select crank lengths between 150 and 180 mm without affecting their physiological performance. Until further research, factors such as anthropometrics, comfort, and selfselected cadence should be used to facilitate crank length selection in recumbent handcyclists.

The Science of Handcycling: A Narrative Review

“…16 Kinematic investigations have also investigated the motion of the thorax, scapular, and wrist. 7,16 Shoulder internal and external rotation, thorax, scapular, and wrist kinematics do not follow a smooth parabolic pattern. 10,[13][14][15]19 Indeed, when compared with novice able-bodied riders, trained handcyclists demonstrate less shoulder internal rotation suggesting that there may be technical differences between users of different skill levels, independent of handbike configuration.…”

“…The cyclical flexion and extension of the elbow and shoulder generate the propulsive torque applied to the handgrips. The torque profile in handcycling demonstrates 2 distinct maxima and minima, which allow for dividing propulsion into a push and pull phase (Figure 1), [7][8][9] The highest torques are generated during the middle of the push and pull phase in which the arm flexors and extensors are in a favorable position to generate force. 10,11 However, the turnover phases, furthest reach, and closest reach, have been demonstrated to be less favorable positions to generate force.…”

“…12 Whereas able-bodied participants demonstrate an increasing shift toward pull phase propulsion, 9,[13][14][15] trained recumbent handcyclists tend to apply the majority of force during the push phase of the propulsion cycle. 7 Given the fact that the classification of trained handcyclists has been found to impact upon their ability to apply force throughout the crank cycle, it appears that H1 classified handcyclists with a SCI at C6 or above mainly apply force during the pull phase with nearly no force applied during the push phase. Conversely, handcyclists with a spinal lesion at or below C7 (H2-H4) apply force more equally across the push and pull phases, which has been suggested to improve movement efficiency.…”

“…These studies have suggested that crank axis, determined by the crank fore-aft position and crank height, and the trajectories of the handgrips, determined, by the crank length and handgrip angle may have a significant impact on handcycling technique. 7,9,16,18,20 Elite handcyclists understand the importance of handbike configuration on technique and performance, yet large differences exist between individuals, due to personal preference and a trial-anderror approach employed by many handcyclists.…”

“…It has been proposed shorter crank length (150 or 160 mm) may be more economical at a higher cadence (>90 rpm), while longer crank length (170 or 180 mm) may be more economical at a lower cadence (<90 rpm). 17 However, Mason et al, 7 studied the effects of varying crank lengths between 150 and 180 mm at a constant handgrip speed and identified no differences in handcycling economy (in milliliters per minute per Watt) suggesting that handcyclists should adopt a crank length of between 150 and 180 mm dependent upon personal preference. Finally, considering handgrip position, Krämer et al, 20 demonstrated that a pronated handgrip angle of +30°may be the optimal position from which to generate power.…”