Aim: We investigated the effects of work different work load increments on the validity of non-invasive aerobic to anaerobic metabolic transition point estimation from heart rate-work rate relationships during incremental exercise tests.

Material and Method: Thirteen male subjects (21.0±0.4 yr) performed two incremental exercise tests with work rates of 15 W/min (W15) and 30 W/min (W30) until the limit of tolerance using an electromagnetically-braked cycle ergometer. During exercise, heart rate was measured using polar heart rate watch; respiratory parameters were estimated using spirometry. Aerobic to anaerobic metabolic transition point estimated from ventilation to work rate relationships and compared with heart rate-work rate relationship.

Results: We have found three different responses in heart rate-work rate relationships during incremental exercise test. A linear relationships observed in 6 (W15) and 7 (W30) subjects. Heart rate-work rate relationship showed a deflection to left side in 2 (W15) and 4 (W30) subjects and a right side deflection in 5 (W15) and 2 (W30) subjects. There was no an association between aerobic to anaerobic metabolic transition point and heart rate-work rate deflection point only in any subjects.

Conclusion: Consequently, heart rate-work rate deflection point may not provide accurate aerobic to anaerobic metabolic transition point estimation. The different work protocols may also lead changes in heart rate–work rate relationships. Thus, investigators or clinicians should be careful using heart rate deflection point.