Abstract
Eccentric (ECC) cycling is used in rehabilitation and sports conditioning settings. We present the construction and mode of operation of a custom-built semi-recumbent ECC cycle designed to limit the production of lower limb muscle activity to the phase of the pedal cycle known to produce ECC contractions. A commercially available semi-recumbent frame and seat (Monarch, 837E Semi-recumbent Bike, Sweden) were used to assemble the ergometer. An electrical drive train system was constructed using individual direct drive servo motors. To avoid active muscle activation occurring during the non-ECC pedaling phase of cycling, a “trip” mechanism was integrated into the drivetrain system using a servo-driven regenerative braking mechanism based on the monitoring of the voltage produced over and above a predetermined threshold produced by the motors. The servo drive internal (DC bus) voltage is recorded and internally monitored during opposing (OPP) and non-opposing (N-OPP) phases of the pedal cycle. To demonstrate that the cycle functions as desired and stops or “trips” when it is supposed to, we present average (of 5 trials) muscle activation patterns of the principal lower limb muscles for regular ECC pedal cycles in comparison with one pedal cycle during which the muscles activated outside the desired phase of the cycle for a sample participant. This semi-recumbent ECC cycle ergometer has the capacity to limit the occurrence of muscle contraction only to the ECC phase of cycling. It can be used to target that mode of muscle contraction more precisely in rehabilitation or training studies.
Highlights
Semi-recumbent eccentric (ECC) cycling is frequently used in rehabilitation primarily due to the significantly reduced cardiorespiratory demand at a given workload, compared to traditional concentric (CON) cycling (Dufour et al, 2004; Hoppeler, 2016)
We have outlined the construction of a novel semi-recumbent ECC cycle ergometer, designed to limit semi-recumbent ECC cycling to only ECC muscle contractions during a phase where participants opposed the direction of the pedals
This is the first ECC cycle ergometer that has been purposely built with an integrated mechanism designed to minimize the potential for non-ECC muscle activations occurring during the non-OPP phase of semi-recumbent ECC cycling
Summary
Semi-recumbent eccentric (ECC) cycling is frequently used in rehabilitation primarily due to the significantly reduced cardiorespiratory demand at a given workload, compared to traditional concentric (CON) cycling (Dufour et al, 2004; Hoppeler, 2016). During ECC cycling (either upright or semi-recumbent), participants perform repetitive ECC muscle contractions by repeatedly applying resistive force against backward-rotating motor-driven pedals (Green et al, 2018; Barreto et al, 2021). ECC contraction of the knee extensors occurs within the “pushing” or “ECC extension” phase of ECC cycling (Elmer et al, 2010; Peñailillo et al, 2015), as the motor-driven pedals move from bottom dead center (BDC) to top dead center (TDC; Green et al, 2018). During ECC cycling, ECC muscle contractions can only occur when the backward-rotating pedal becomes opposable [as the backward pedal moves from slightly beyond BDC to TDC; opposing (OPP) phase], allowing the rider to apply an OPP, braking force. Muscle contractions that occur when the pedal is not an OPP force (from TDC to slightly beyond BDC; non-opposing (N-OPP) phase cannot be considered ECC, as the knee extensors would be shortening in length (i.e., CON contraction)
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