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. 2014 Feb 21;9(2):e89729. doi: 10.1371/journal.pone.0089729

Table 2. Definitions of propulsion technique variables.

Variable: Description: Equation:
Energy expenditure (W) Calculated from the oxygen uptake and respiratory exchange ratioaccording to Garby and Astrup [47] ((4.94*RER+16.04)*(1000*VO2))/60
Gross mechanical efficiency (%) The percentage of internal power used for external power deliveredat the wheels Mean power output/Energyexpenditure
Frequency (push/min) The number of complete pushes per minute. (Cycletime)−1 ⋅ 60
Contact angle (°) Angle at the end of a push minus the angle at the start. Øend(i)−Østart(i)
Max Torque/push (Nm) The maximum torque generated around the wheel-axle within a push Maxstart(i):end(i) (Tz)
Pos. Work/push (J) The torque around the wheel-axle integrated over the contactangle of the push. start(i):end(i) (Tz ⋅ ΔØ)
Neg. Work/cycle (J) The torque around the wheel-axle integrated over the wheelrotation angle during the recovery phase end(i):start(i+1) (Tz ⋅ ΔØ)

Abbrevations: start(i), start of the current push (sample); end(i), end of the current push (sample); Ø, angle (rad); Tz, torque around wheel axle (Nm).