## 2 Materials and Methods
### Testing Protocol  
A commercially available stationary pedalling apparatus (BL3700, Novis Healthcare, Lane Cove West, NSW, Australia) was modified to provide real-time video engagement during pedalling as well as feedback on pedalling performance (Figure 1). The test setup comprised an adjustable seat, pedals, an exercise data recorder, and a computer with a display. To achieve optimal knee flexion and comfort during pedalling, the seat and pedal crank positions were adjusted to each subject's lower limb length and function. Speed and cadence were measured by instrumenting the pedalling apparatus crank using a magnet and hall-effects cadence sensor with a microcontroller board (Mega2560, Arduino, Ivrea, Italy). These data were wirelessly transmitted to a PC, which provided real-time data during pedalling via the display screen (Visual Studio 2017, Microsoft, Redmond, WA, USA), including pedalling speed and duration, target speed, and deviation from target speed data (Figure 2). Real-time video engagement was facilitated by displaying a prerecorded video of the participant's choice from a collection offered by the researchers. The video playback rate was synchronised to a target pedalling speed, and to maintain the video playback rate, participants were required to maintain their pedalling at the target speed. An increase or decrease in cadence from the target speed by 5 rotations per minute (RPM) or more from the target resulted in the video playback moving in fast-forward or slow motion, respectively.  
Each participant was first given one minute to familiarise themselves with the testing apparatus. They then undertook three randomly allocated 15-min sessions of pedalling targeting a set low cadence (60 RPM) which included (i) baseline pedalling without feedback or engagement and cadence information provided only in the first 20 s in order to establish target cadence (ii) real-time visual feedback of cadence data for the entire session, including pedalling duration, pedalling cadence, and cadence deviation from the target, and (iii) real-time engagement to maintain the playback rate of a prerecorded video by pedalling at the target speed. These testing conditions were subsequently repeated at a high target cadence (100 RPM). Thirty-second rest periods were provided after every 5 min of pedalling.  
On completion of the testing, participants completed a self-reported feedback survey that evaluated (i) perceptions of differences between pedalling with visual feedback and video-based engagement compared to the baseline pedalling; (ii) overall experience of pedalling with feedback or engagement, from enjoyment to hindrance; (iii) use of feedback during pedalling for future exercise therapy; and (iv) potential for feedback during pedalling to influence exercise motivation (Supplementary Materials). The survey was undertaken twice, once for pedalling sessions that provided cadence data feedback and a second time for sessions that employed real-time video-based engagement. Before providing responses, the survey questions were discussed with each participant to ensure consistency in question interpretation and reporting.