Physiological Responses to Repeated Maximum Intensity Efforts in Surface and Underwater Fin Swimming

The purpose of the study was to compare physiological and performance responses during surface and underwater fin swimming. Thirteen male, elite fin swimmers performed four repetitions of 50-m sprints using a monofin (4 x 50 m) either on surface (S) or underwater with apnea (U). Performance time and the number of lower body kicks were recorded during 4 x 50-m sprints. Lactate was evaluated before the start, after the second and the fourth sprint and five minutes into recovery. The heart rate was measured continuously and respiratory function was recorded before and after each condition. Performance time was shorter and kicking frequency was higher in U compared to S (17.73 ± 1.18 vs. 19.94 ± 1.41 s, 135 ± 18 vs. 121 ± 15 kicks∙min^-1, p < 0.05). Lactate concentration was no different between conditions. Forced expiratory volume in 1 s and peak expiratory flow were no different before and after the sprints and between conditions (p > 0.05). Forced vital capacity and maximal voluntary ventilation were increased after sprints under both conditions (p < 0.05). The heart rate was decreased in U compared to S during both sprints (167-177 vs. 183-185 b∙min^-1) and the recovery period (141-151 vs. 166-174 b∙min^-1). Underwater and surface repeated sprint swimming present maximal dynamic and physiological responses that should be considered during fin swimming training.