Quantifying fatigue in working divers

Thirty professional divers involved in training, bounce dives, working saturations, and deep experimental saturations were observed over a 1-month period. The subjects themselves performed simple twice-daily measurements of oral temperature, heart rate, breathhold time, handgrip strength, length and quality of sleep, and a subjective estimation of fatigue. The data were analysed with respect to the type of work done by the diver, separating diving from nondiving days. The results showed that subjective estimation of fatigue corresponded to the increment of evening oral temperature and heart rate over morning values. Both inspiratory and expiratory breathhold times decreased from morning to evening in those situations deemed most tiring by the divers. Sleep was generally of average duration and quality; however, diving during the daytime was associated with a decreased amount of sleep in the 24-h period including the following night. Sleep was also of poorer quality during periods of saturation diving. In addition to such group variations, individual divers showed significant performance changes on the various tests, demonstrating the value of this approach to the practical question of deciding when a man is too tired to dive safely. Extension of this method can, we hope, aid in the definition of safe working rotations for professional divers.