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Lactic acidosis, potassium, and the heart rate deflection point in professional road cyclists
1Departamento de Ciencias Morfológicas y Fisiología, Universidad Europea de Madrid, Madrid, Spain. alejandro.lucia@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, P(50) 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.