Purpose To evaluate the information provided by Polar Vantage V, a new generation of heart rate monitor/watch (HRM-watch) to the user, regarding the acute:chronic load ratio (ACLR), based onthe external and internal load measures and examine the measures against psychological and physiological measures before and during a threshold test with VO2max testing.

Method A five-week prospective study with results and data collected during and after four normal training weeks and during a fifth week with a very high training load. The results from HRM-watchwere then evaluated against the results from physiological and psychological tests. Eight endurance runners were recruited.

Results Differences in ACLR against the differences in HRR show a R2 value of 0.77 (p<0.05). ACLR signicantly increased with an average of 0.33 from 0.93 to 1.26 (p=0.003, 95 % CI= 0.17 {0.49). Differences in ACLR against dierences in total mood disturbance (TMD) from POMS showin regression analyses a R2value of 0.67 (p=0.05). No significant difference was noted in neither resting HRV (p=0.3, 95% CI= -22.2 { 8.5) or standing HRV (p=0.15, 95% CI= - 4.15 { 20.8).

Conclusion Based on the result of the present study it can be concluded that training status, well-being and present mood state can be predicted fairly good with the information from the internal and external load measurements from the Polar Vantage V. However, the power of present exploratory study was low due to a low number of included participants. Future research with greater number of participants and an improved study design is needed to verify these interesting findings.