We hypothesized that the saddle vertical force would be a critical parameter to explain the sit-to-stand transition during cycling. A specific incremental test was used to determine the power at which the participants would spontaneously transit to the standing position (i.e., the Sit-to-Stand Transition Power; SSTP). Twenty-five participants were required to pedal at six different powers ranging from 20 (1.6 ± 0.3 W.kg-1) to 120% (9.6 ± 1.6 W.kg-1) of SSTP at 90 RPM. Five 6-component sensors recorded the loads applied on the saddle, pedals and handlebars. The results showed that the saddle vertical force decreased with increasing cycling power, from a static position on the bicycle (5.30 ± 0.50 N.kg-1) to 120% of SSTP (0.68 ± 0.49 N.kg-1). Pedal and handlebar force directions were reversed around SSTP, suggesting that the seated position may become constraining in these pedalling conditions. The present data suggest that the saddle vertical force may be predictive of the sit-to-stand transition in cycling, and that pedalling in the seated position at high crank forces may not be optimal, explaining the spontaneous change in coordination mode.