Two studies to date have used IC to examine the response to physical rehabilitation activities performed by patients in the ICU. Collings et al conducted a randomised cross-over study in which 10 ICU patients completed either a passive chair transfer or an active sit-over-the-edge-of-the-bed (SOEOB) on one day, followed by the alternative activity on the consecutive day. The 'active' SOEOB activity elicited a significantly greater increase in oxygen consumption than the passive activity (90.69 ml/min (95% CI 44.04 to 137.34) vs 14.43 ml/min (95% CI −27.28 to 56.14), p = 0.007). Hickmann et al examined active or passive cycling in critically ill patients and healthy controls, demonstrating increased oxygen consumption during the active exercise compared to passive in patients with differing energy requirements compared to healthy individuals.