Heart rate variation after breath hold diving with different underwater swimming velocities.
BACKGROUND: The aim of this study was to demonstrate the kinetics of heart rate and blood lactate level obtained after repeated short breath holds with muscular effort in a swimming pool. METHODS EXPERIMENTAL DESIGN: each subject had to perform a series of breath hold diving at rest and three series for different underwater swimming velocities. A series corresponded to six dives of a 30 sec duration separated by a recovery period of 30 sec. Heart rates and blood lactate levels were measured at rest and at the end of each series of breath holds. PARTICIPANTS: the population was composed of 10 male subjects divided into one trained group (5 experts) and one group of 5 beginners. RESULTS: Results indicated a higher bradycardia for the expert group at static breath hold (54.25 vs 65.5 beats x min-1). At the end of a series of breath holds, tachycardia was higher for beginners at different underwater swimming velocities. These values were less significant than the heart rate measured in laboratory despite trials that were abandoned due to high blood lactate levels above 3.5 mmol x l-1. In order to avoid the breath hold breaking point, the maximum heart rate had to correspond to the heart rate of the ventilatory threshold measured in the laboratory, minus the variations of bradycardia measured at rest. CONCLUSIONS: For the training coach, bradycardia was determined by water immersion during a static breath hold. This permitted an evaluation of the level of diver training. A maximal heart rate was attempted to avoid the breath hold breaking point. The results of this study may be useful in creating an effective diver training program.