PHYSIOLOGICAL STRAINS WHILE PUSHING OR HAULING

An experiment has been designed to compare two ways of load moving: pu shing with a bar or hauling with a pelvic belt, against the same resis tances, at the same speeds. This study has been carried out in the lab oratory 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 seco nd). The physiological strains were studied by measuring heart rate (H R) and oxygen consumption (VO2) in both experiments. In addition, perc eived exertion was estimated in the second group according to a rating scale of perceived exertion (RPE). Analysis of variance showed that p ushing with the arms was more strenuous than hauling with a pelvic bel l with regard to HR, VO2 and RPE (P < 0.01). When resistances and spee ds were grouped, the differences between pushing and hauling were equa l to 3 beats . min(-1), 0.85 ml . min(-1) . kg(-1) for HR and VO2, res pectively, for the first experiment (sedentary subjects), wheras the d ifferences 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 experim ent (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 s tatic work (pushing with the upper limbs) added to the dynamic work co uld explain the higher physiological cost during pushing.