Commonly used reference values underestimate oxygen uptake in healthy, 50-year-old Swedish women.

Cardiopulmonary exercise testing (CPET) is the gold standard among clinical exercise tests. It combines a conventional stress test with measurement of oxygen uptake (VO 2 ) and CO2 production. No validated Swedish reference values exist, and reference values in women are generally understudied. Moreover, the importance of achieved respiratory exchange ratio (RER) and the significance of breathing reserve (BR) at peak exercise in healthy individuals are poorly understood. We compared VO 2 at maximal load (peakVO 2 ) and anaerobic threshold (VO 2@ AT ) in healthy Swedish individuals with commonly used reference values, taking gender into account. Further, we analysed maximal workload and peakVO 2 with regard to peak RER and BR. In all, 181 healthy, 50-year-old individuals (91 women) performed CPET. PeakVO 2 was best predicted using Jones et al. (100·5%), while SHIP reference values underestimated peakVO 2 most: 112·5%. Furthermore, underestimation of peakVO 2 in women was found for all studied reference values (P<0·001) and was largest for SHIP: women had 128% of predicted peakVO 2 , while men had 104%. PeakVO 2 was similar in subjects with peak RER of 1-1·1 and RER > 1·1 (2 328·7 versus 2 176·7 ml min-1 , P = 0·11). Lower BR (≤30%) related to significantly higher peakVO 2 (P<0·001). In conclusion, peakVO 2 was best predicted by Jones. All studied reference values underestimated oxygen uptake in women. No evidence for demanding RER > 1·1 in healthy individuals was found. A lowered BR is probably a normal response to higher workloads in healthy individuals.