Heart rate variability in free diving athletes..pdf

Heart rate variability in free diving athletes Vassiliki Christoforidi, Nikolaos Koutlianos, Pantazis Deligiannis, Evangelia Kouidi and Asterios Deligiannis Laboratory of Sports Medicine, Sports Medicine Division of TEFAA, Aristotle University, Thessaloniki, Greece Correspondence Nikolaos Koutlianos, 75 Loutron Str, 57200 Lagadas, Greece E-mail: koutlian@phed.auth.gr Accepted for publication Received 21 July 2011; accepted 2 November 2011 Key words Apnea; autonomic nervous system; breath-hold; diving; cardiac vagal activity Summary The aim of the study was to evaluate the cardiac autonomic activity in free diving (FD) athletes. Thirteen Greek male free divers (group I, aged 33?4 ± 6?3 years, 6?6 ± 4?5 years of training experience) volunteered to participate while 13 age- matched sedentary subjects served as control group (group II). All subjects were submitted to ambulatory 24-h ECG recording for heart rate variability (HRV) analysis on a day of regular activities with no exercise or training. The results showed that group I had significantly lower minimum and mean heart rate by 23?9% (P0?001) and 20?6% (P0?001), respectively. All the measured time and frequency domain indices of HRV which reflect cardiac parasympathetic activity were higher in group I than in group II by 37?6% to 146% (P0?001). Conclusively, the resting cardiac autonomic activity and especially the parasympathetic branch was significantly increased in free divers compared to untrained subjects. This finding should be rather attributed to the accumulated effect of both exercise training and frequent exposure to FD stimulus. Introduction Given the increasing popularity of various forms of breath-hold diving, breath-hold divers assay for greater depths and longer lasting apnea efforts is undoubtedly bringing the human body ever closer to absolute physiological limits. Indeed, the performance of the diving athletes is remarkably impressive. The current male world record for breath-hold duration of a p