The Physiological Basis of Rest Pauses in Heavy Work

There are two methods of approach to the problem of finding the right length and number of pauses in heavy work. The one, rough and only reliable in rather heavy work, is to take 4 kcal./min. as an overall limit of working capacity and to give enough pauses to keep the average energy expenditure of the whole shift on this level. The other method takes the pulse rate as an index of sufficient blood supply to all muscles, and a sufficient blood supply to the working muscles as the principal necessity in avoiding fatigue. This method aims at keeping the pulse rate during the shift at a constant average level and to prevent any kind of a pulse debt, which leads to an increased number of pulses during recovery after the end of work. The second method has proved useful in arranging pauses so as to allow a man to work within his endurance limit.