 What is momentum? What does it have to do with collisions in sport and how are jumping and sprinting momentum related? Momentum is the quantity of motion that a body possesses. Linear momentum is equal to the mass of a body multiplied by its velocity. The law of conservation of momentum necessitates that the total momentum before an impact is equal to the total momentum after an impact. In this example, the total momentum before impact is the mass times velocity of the smaller object. The larger object is stationary. Total momentum before impact is equal to the total momentum after impact, which is the sum of the mass times velocity of each individual body. The greater the momentum of a body, the more pronounced the effects that it produces on other bodies in its path. When analyzing or interpreting momentum, it's important to remember that it's influenced by both mass and velocity. For example, recent research suggested that vertical jump takeoff momentum should be used to predict sprint momentum in athletes, which would be useful in sports where pre-impact sprint momentum can influence the outcome of collisions. We were intrigued and we wanted to know whether this prediction was due to the relationship between jump height and sprint speed or the fact that both momentum calculations include the same body mass. In fact, if you take any two sets of random numbers and multiply each pair by the same body mass value, they might then correlate with each other. We simulated the relationships reported in previous studies and varied certain values to see what effect they had on the correlation between jump momentum and sprint momentum. Firstly, the higher the correlation between jump height and sprint speed, the higher the correlation between the two momenta. This correlation remained very large even when jump height and sprint speed had no relationship with each other or even when they related negatively with each other. The ability of jump takeoff momentum to predict sprint momentum was greatest under relatively high variation in body mass between individuals and relatively low variation in jump height. This is due to the increased emphasis on body mass in these situations. For example, if everybody had the same body mass, all of the correlation between momenta would be due to the weaker correlation between the velocities. If everybody had the same jump and sprint abilities, all of the correlation between momenta would be due to their mass. And we now know that body mass is the better predictor of sprint momentum. There were lots of conditions in which body mass was the best predictor of sprint momentum. A few conditions in which there was no significant difference between the predictors, and no conditions in which jump momentum was the best predictor of sprint momentum. It is recommended that any reason for calculating or monitoring jump takeoff momentum should be separate from its ability to predict sprint momentum, and that if necessary, body mass alone may be a better predictor of sprint momentum. For the coordination and control of counter movement jumps, check out this video linked in the top corner and in the description to see how momentum affects cricket bowling. Check out Paul Felton's lecture as part of the sports biomechanics lecture series and the science of cricket series, both on this channel.