Measures of cardiorespiratory fitness (CRF) may be an important predictor of all-cause mortality as well as being valuable in the assessment of training in athletes. CRF is usually quantified as the maximal oxygen consumption (VO2max). The measurement of VO2max involves an incremental test to reach maximal exertion. The difficulty in obtaining true VO2max highlights the need for surrogate parameters. Potential alternative measures include heart rate recovery (HRR) and heart rate variability (HRV). Previous investigations have provided contradictory evidence regarding the relationship between VO2max and HRR and HRV. In this study, the fidelity of the correlations between VO2max and both HRR and HRV were investigated in trained individuals. This study was approved by the local research ethics committee. 36 students (20 male, 16 female, age=20.5±1.23 yrs) actively engaged in sports clubs at the University of Bristol were recruited as volunteers. Subjects with a history of heart disease or diabetes were excluded. Subjects undertook an incremental exercise test on a cycle ergometer (25 W every 2 min) to volitional exhaustion to obtain VO2max and maximal power output (MPO). The electrocardiogram (ECG) was recorded during a pre-exercise supine rest period and HRV was calculated as the coefficient of variation in RR intervals over 5 minutes. HRR was measured as the reduction in heart rate within the first minute following cessation of exercise. Data are reported as mean±standard deviation. Differences were examined by Student’s unpaired t-test. Correlation was examined by Pearson’s correlation coefficient. Statistical significance was accepted for P<0.05.Males were heavier (81.8±12.4 kg) and taller (1.85±0.06 m) than females (64.8±9.0 kg, P<0.0001; 1.69±0.08 m, P<.0001), had greater MPO (362.5±51.0 W vs 264.1±36.5 W, P<0.0001) and absolute VO2max (4.17±1.04 l.min-1 vs 3.17±0.77 l.min-1, P=0.0029). There was no sex difference in heart rates at rest (66.2±11.0 bpm, n=36) or at maximal exertion (190.0±7.99 bpm). As expected, absolute VO2max correlated strongly with MPO for both sexes (r=0.6149, P<0.0001). On the other hand, VO2max relative to body weight did not differ between males and females (50.73±12.68 ml.kg-1.min-1, n=36) and did not correlate with MPO. Female HRR was significantly greater than males (P=0.0394). There was no sex difference in HRV (0.089±0.033, n=36).There was no correlation between HRR and either absolute (r=-0.099, P=0.565) or relative (r=0.008, P=0.962) VO2max. Similarly, HRV was not correlated with either absolute or relative VO2max. Thus, neither HRV nor HRR could be considered useful surrogate measures of CRF in this group of students. The lack of correlation may reflect the influence of autonomic cardiac control on HRV and HRR and further research is needed to investigate the underlying mechanisms.