PurposeTo investigate the effect of functional electrical stimulation-assisted cycle ergometry (FES-cycling) on muscle strength, cognitive impairment and related outcomes.MethodsMechanically ventilated patients aged ≥18 years with sepsis or systemic inflammatory response syndrome were randomised to either 60 min of FES-cycling >5 days/week while in the intensive care unit (ICU) plus usual care rehabilitation versus usual care rehabilitation alone, with evaluation of two primary outcomes: (1) muscle strength at hospital discharge and (2) cognitive impairment at 6-month follow-up.ResultsWe enrolled 162 participants, across four study sites experienced in ICU rehabilitation in Australia and the USA, to FES-cycling (n=80; mean age±SD 59±15) versus control (n=82; 56±14). Intervention participants received a median (IQR) of 5 (3–9) FES-cycling sessions with duration of 56 (34–63) min/day plus 15 (10–23) min/day of usual care rehabilitation. The control group received 15 (8–15) min/day of usual care rehabilitation. In the intervention versus control group, there was no significant differences for muscle strength at hospital discharge (mean difference (95% CI) 3.3 (−5.0 to 12.1) Nm), prevalence of cognitive impairment at 6 months (OR 1.1 (95% CI 0.30 to 3.8)) or secondary outcomes measured in-hospital and at 6 and 12 months follow-up.ConclusionIn this randomised controlled trial, undertaken at four centres with established rehabilitation programmes, the addition of FES-cycling to usual care rehabilitation did not substantially increase muscle strength at hospital discharge. At 6 months, the incidence of cognitive impairment was almost identical between groups, but potential benefit or harm of the intervention on cognition cannot be excluded due to imprecision of the estimated effect.Trial registration numberACTRN 12612000528853, NCT02214823.