Handcycling: different modes and gear ratios

Handrim wheelchair propulsion is a straining form of ambulation. In contras t, arm crank exercise in laboratory settings has shown a higher degree of g ross mechanical efficiency and increased levels of peak power output. Moreo ver, arm crank exercise can be conducted at different gear ratios and in as ynchronic or synchronic mode. Although tricycle crank exercise or handcycli ng has become increasingly popular for recreational use, sports and outdoor wheeling over the last decade, today little is known about the cardiopulmo nary strain in handcycling. The physiological and subjective responses duri ng handcycling were evaluated In a group of 12 male non-wheelchair users (a ge 24.6 +/- 2.7 yr; body weight 73.7 +/- 9.7 kg). During an incremental sub maximal exercise test on a motor driven treadmill (velocity: 1.8 m s(-1); a n incremental slope of 1% per 3 min; 0-3%; mean power output of the subject group varied between 7.6 +/- 1.6 W and 47.5 +/- 6.2 W), effects of asynchr onic and synchronic crank settings and three different gear ratios (1: 0.42 , 1:0.59, 1:0.74 (or 24, 36 and 44 rpm)) were evaluated in a random testing sequence. Significantly lower levels of mean oxygen uptake, ventilation re lative heart: rate and oxygen uptake were seen during synchronic arm use an d for the lighter gear ratios (i.e. higher movement frequency 44 rpm). Subj ective local perceived discomfort showed similar trends. Conversely, gross mechanical efficiency appeared higher for these conditions. The need for st rong medio-lateral stabilizing muscle effort during asynchronic ann use (to ensure a proper wheeling direction as well as simultaneous power transfer to the cranks) and the effective use of the trunk in this subject group may explain the advantage of sychronic arm use. Whether this advantage is cons olidated among wheelchair confined individuals needs further study. Apart f rom the important effects of a shift in force-velocity characteristics of t he contracting muscles with varying gear ratios, increased static finger fl exor and arm muscle activity may explain the increased strain in the somewh at unnatural heavy gear condition (24 rpm) at the studied velocity. Results need to be re-evaluated for wheelchair user populations and different high er velocities and power conditions. Moreover, other aspects of the wheelcha ir-user interface must be studied in tn-der to generate optimum fitting and design guidelines for different user groups and conditions of use.