Athletics of To-Day 1929

210 Athletics of To-day where m= mass, or weight of the jumper's body, which is 140 lb. If this is worked out the reader will find that the impulse of the force required is: A for 24 ft. per second, 350 units of impulse. B for 20 ft. per second, 910 units of impulse. C for 17.14 ft. per second, 1,320 units of impulse. This proves of course that the faster a man runs to his take– off the less units of impulse will he need for making his jump, or, conversely, if C could approach at the speed of A and still generate his own previous increase on the first speed, he would easily win the contest. In other words, the greater the speed of the approach run the more units of energy the athlete will have at his command to put into the jump. Not every one, however, is blessed equally with speed and spring, wherefore long jumpers fall into two categories. There is the sprinter type, relying on speed for distance, and the jumping type, which relies mainly upon natural jumping powers to achieve the desired result. It seems rather obvious to say that jumpers must strive after speed and the sprinting type seek to develop its springing powers, but such is the case; for it is a just combination of the two qualities that brings the big results. The approach run as a rule supplies about seventy-five per cent. of the long jumper's difficulties. For even where the run has become standardized at say 92, 110 or 115 feet, and the athlete has developed an absolutely regular stride, it will be found that the run varies according to the physical condition of the athlete, the state of track and weath r, and the direction of the wind. As we have seen, De Hart Hubbard's 1 g gave him trouble at aris in 1924, and that was why he recorded two no-jumps in three trials. It was also, I imagine, due con– sideration of all these circumstances which led Lawson Rob rtson, the American chief Olympic coach, to recommend the development of a mechanical approach, pacing back an even number of strides from the take-off to get the starting spot in each competition. This, however, calls for considerable sighting judgm nt, such as I mentioned in Chapter XI on the