The Defeat of Gravity in Weight Lifting

Abstract

That weightlifting is the art of defeating gravity may seem a statement of the obvious. It is very rewarding however, as in all battles, to consider the nature of the adversary. Its relentless nature means that man can only win for a limited time. As we shall see, the earlier he engages the enemy, the more spectacular is his short-term advantage. A long, drawn-out struggle is to be avoided at all costs. Man, on the other hand, is apt to injure himself when he tries to mobilise his forces too rapidly. Like the battle commander, the weightlifter is presented with a dilemma and the information available about his own strength and resources is inadequate to eliminate the possibility of disaster. We must be thankful that at least the foe, gravity, is an entirely predictable one. These words are a fairly accurate summary of this paper. As far as the bar is concerned, the effects of both gravity and the jerks that the man exerts conform to the same rules which are known as Newton' s Laws of Motion. It does not matter, when applying the rules, that gravity acts continuously and man does not. Both gravity and jerk can be thought to consist of successions of impulses impinging on the weights, as in Fig. 1. GvRAVITY CA % I1 t+ .31111 1I1I1Llll Fig. 1. Forces on the bar depicted as successions of impulses. In the case of gravity, all the impulses are of the same magnitude whilst those of the jerk successively build up in magnitude and then die away. The impulse is more of a concept than a reality which engineers use to denote a force acting for such a short period of time that the whole event can be called instantaneous. 37