Relaxed G-tolerance is traditionally determined in open-loop controlled centrifuges, i.e. the pilot/test subject is unable to influence the G-load, which instead is manoeuvred from the centrifuge control room. By contrast, in the Dynamic Flight Simulator at the Swedish Defence Materiel Administration, Malmslätt, Sweden, the subject is able to continuously control the G-load (closed-loop control). It is a widespread opinion amongst pilots that G-tolerance is higher under closed- than open-loop conditions. The aims were to investigate (1) whether it is possible to use closed-loop control of the G-load during determination of relaxed G-tolerance, and (2) if relaxed G-tolerance is higher when determined in closed- than in open-loop conditions. Method: Relaxed G-tolerance was determined in eight subjects under three conditions: (1) OL-VFB; open-loop control with visual feedback, (2) OL-NFB; open-loop control with no visual feedback, and (3) CL; closed-loop control. Result: In the CL condition the G-load varied substantially and was on average lower than during the OL conditions, at any stipulated G-time profile. The G-tolerance did not differ between CL (3.66 G), OL-VFB (3.70 G) and OL-NFB (3.64 G). Conclusions: During closed-loop control, precision and reproducibility of the G-load are too low to permit this functionality to be used for determination of relaxed G-tolerance. There is no systematic difference in relaxed G-tolerance as determined in closed- vs. open-loop controlled systems.