The findings of previous studies investigating the strength of the relationships between the percentages of maximal heart rate (%HR(max)), heart rate reserve (%HRR), maximal oxygen uptake (%VO(2max)), and oxygen uptake reserve (%VO(2)R) have been equivocal. This inconsistency between studies could largely be due to differences in methodology. The purpose of this study was therefore to determine whether different VO(2max) test protocols and resting VO(2) assessment influence the relationships between the %HR(max), %HRR, %VO(2max), and %VO(2)R. Thirty-three young men performed maximal treadmill protocols (ramp, Bruce) to assess HR(max) and VO(2max). Resting VO(2) was assessed as follows: a) resting VO(2standard), using strict criteria (24 h exercise abstention, alcohol, soft drinks, or caffeine; 8 h fasting; 30 min assessment); b) resting VO(2sitting) and; c) resting VO(2standing) (both 5 min before exercise testing). The %HRR was closer to %VO(2max) than to %VO(2)R, especially in the ramp protocol (p<0.001). In the Bruce protocol, relationships were closer to the identity line, and there was no significant difference between %HRR and %VO(2max), or %VO(2)R. The VO(2max) was significantly higher in the ramp protocol compared to the Bruce protocol (p<0.001). In both protocols resting VO(2) assessment produced no significant difference in the intercepts and slopes of the %HRR-%VO(2)R relationships obtained from individual regression models. The %VO(2)R calculated using resting VO(2standard) was closer to %HRR compared to VO(2sitting) and VO(2standing). The premise that %HRR is more strongly related to %VO(2)R than to %VO(2max) was not confirmed. Methodological differences should be considered when interpreting previous studies investigating %HR(max), %HRR, %VO(2max), and %VO(2)R relationships.