ORIGINAL ARTICLE

Lactic acidosis, potassium, and the heart rate deflection point in professional road cyclists

A Lucía¹, J Hoyos², A Santalla¹, M Pérez¹, A Carvajal³ and J L Chicharro³

¹ Departamento de Ciencias Morfológicas y Fisiología, Universidad Europea de Madrid, Madrid, Spain
² Asociación Deportiva Banesto, Spain
³ Departamento de Enfermería y Unidad de Investigación, Universidad Complutense de Madrid, Madrid, Spain

Correspondence to:
Correspondence to:
Dr Lucía, Departamento de Ciencias Morfológicas y Fisiología, Edificio A, Despacho 330, Universidad Europea de Madrid, E-28670 Madrid, Spain;
alejandro.lucia{at} mrfs.cisa.uem.es

Objective: To determine the influence of lactic acidosis, the Bohr effect, and exercise induced hyperkalaemia on the occurrence of the heart rate deflection point (HRDP) in elite (professional) cyclists.

Methods: Sixteen professional male road cyclists (mean (SD) age 26 (1) years) performed a ramp test on a cycle ergometer (workload increases of 5 W/12 s, averaging 25 W/min). Heart rate (HR), gas exchange parameters, and blood variables (lactate, pH, P₅₀ of the oxyhaemoglobin dissociation curve, and K⁺) were measured during the tests.

Results: A HRDP was shown in 56% of subjects at about 88% of their maximal HR (HRDP group; n = 9) but was linear in the rest (No-HRDP group; n = 7). In the HRDP group, the slope of the HR-workload regression line above the HRDP correlated inversely with levels of K⁺ at the maximal power output (r = -0.67; p<0.05).

Conclusions: The HRDP phenomenon is associated, at least partly, with exercise induced hyperkalaemia.

Keywords: anaerobic threshold; Conconi test; cycling; heart rate; ramp test

Abbreviations: HR, heart rate; HRDP, heart rate deflection point; AT, anaerobic threshold; LVEF, left ventricular ejection fraction; ECG, electrocardiogram; RCP, respiratory compensation point; LT, lactate threshold; OBLA, onset of blood lactate accumulation

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