The scientific article “Physical Fitness and Performance Age-Related Differences in 100-m Sprint Performance in Male and Female Master Runners” (Marko T. Korhonen, Antti Mero, Harri Suominen) has some interesting math and science in it.
They said: “There was a general decline in sprint performances with age, the decrease becoming more evident around 65–70 yr of age. The velocity during the different phases of the run declined on average from 5 to 6% per decade in males and from 5 to 7% per decade in females. Similarly, stride length showed clear reductions with increasing age, whereas stride rate remained unchanged until the oldest age groups in both genders. Furthermore, the ground contact time, which correlated with velocity, was significantly longer, and flight time, which correlated with both velocity and stride length, was shorter in older age groups.”