Heart rate responses of a master athlete during ultra-endurance swimming

Aim: Swimming races outside swimming pools take place all over the world, but studies focusing on their physiological aspects are scarce. In fact, rules forbid any direct contact with swimmers during sanctioned events. This case report presents heart rate responses of a master athlete during an ultra-endurance open water solo swim and analyzes results based on a prior cardiopulmonary exercise test. Methods: The swimmer performed a cardiopulmonary exercise test on a treadmill, following a ramp protocol, with continuous electrocardiogram recording. The athlete performed a 36 km swimming race with continuous heart rate recording. Description of swimming heart rate accordingly to heart rate training zones and correlation analysis between HR and swim speed was assessed. Results: The athlete swam the 36 km event in 11 hours, 16 minutes and 15 seconds. Most of the swim time was spent in training zone 3 (55%), and only 2% of race time was spent in zone 5. Swimming speed (3.2 ± 0.7 km/h) failed to correlate with HR during the event (r2 = 0.1334, p > 0.05). Conclusion: Although HR did not correlate with swimming speed it successfully indicated exercise intensity during this 36 km event. These results can be used in the preparation and monitoring of other solo long-distance swimmers.