The mathematical analysis of the heart rate and blood lactate curves during incremental exercise testing

This paper describes a new mathematical approach for the analysis of HR (heart rate) and BL (blood lactate) curves during incremental exercise testing using a HR/BL curve and its derivatives, taking into account the native shape of all curves, without any linear approximation. Using this approach the results indicate the appearance of three characteristic points (A, B and C) on the HR/BL curve. The point A on the HR/BL curve which is the value that corresponds to the load (12.73 ± 0.46 km h-1) at which BL starts to increase above the resting levels (0.9 ± 0.06 mM), and is analogous to Lactate Turn Point 1 (LTP1). The point C on the HR/BL curve which corresponds to a BL of approximately 4mM, and is analogous to LTP2. The point B on the HR/BL curve, which corresponds to the load (16.32 ± 0.49 km h-1) at which the moderate increase turns into a more pronounced increase in BL. This point has not been previously recognized in literature. We speculate this point represents attenuation of left ventricular ejection fraction (LVEF) increase, accompanied by the decrease in diastolic time duration during incremental exercise testing. Proposed mathematical approach allows precise determination of lactate turnpoints during incremental exercise testing.