Physiological strains while pushing or hauling.

An experiment has been designed to compare two ways of load moving: pushing with a bar or hauling with a pelvic belt, against the same resistances, at the same speeds. This study has been carried out in the laboratory on a treadmill, using two groups: 15 healthy sedentary men and 10 endurance trained male athletes. The task consisted of pushing or hauling against the same resistance (3, 5 and 7 kg for the first group and 6, 8, 9 and 10 kg for the second) at two walking speeds (3 and 4 km. h-1 for the first group and 3.7 and 4.7 km.h-1 for the second). The physiological strains were studied by measuring heart rate (HR) and oxygen consumption (VO2) in both experiments. In addition, perceived exertion was estimated in the second group according to a rating scale of perceived exertion (RPE). Analysis of variance showed that pushing with the arms was more strenuous than hauling with a pelvic belt with regard to HR, VO2 and RPE (P < 0.01). When resistances and speeds were grouped, the differences between pushing and hauling were equal to 3 beats min-1, 0.85 ml. min-1. kg-1 for HR and VO2, respectively, for the first experiment (sedentary subjects), whereas the differences were equal to 11.4 beats. min-1, 1.66 ml.min-1.kg-1 and 2.15 for HR, VO2 and RPE, respectively, for the second experiment (trained endurance athletes). In the endurance athletes, there was a parallel upward shift of the VO2-HR linear relationship for pushing (covariance analysis, P < 0.01), which suggested that an element of static work (pushing with the upper limbs) added to the dynamic work could explain the higher physiological cost during pushing.