Similar slow down in running speed progression in species under human pressure.

The research article investigates how maximum running speeds in horses, dogs, and humans have increased rapidly over the past century but then reached a plateau. It analyzes this in relation to genetic, environmental factors, and changes in training practices.

Investigation of Maximal Running Speed

• The researchers collected data sets on the top ten performers in races over more than a century, covering a variety of distances up to 1500 meters among humans.
• They observed that running speed improved greatly in all three species, causing a considerable shift upwards, followed by a plateau or phase of stabilization.
• Based on a mathematical model called the Gompertz model, the velocities reached were calculated to be as high as 97.4% of the maximum predicted speed in greyhounds and 100.3% in humans.

Genetic Factors and Heritability

• Further analysis was conducted on a subset of individuals using an ‘animal model’. This analysis revealed suggestive evidence of heritability of running speed in horses and potentially in dogs too. This suggests that the capacity for high running speed may be a genetic trait which can be passed down through generations.
• Heritability (h^2) was 0.438 in horses and 0.183 in dogs, implying that genetic elements have a significant role in running speed.

Environmental Factors

• In humans, although genetics have a role, the observation of speed progression was mainly attributed to an increased population of runners and associated improved training techniques over the years.
• The researchers also found geographical disparities in speed progression, where East Africans have impressively improved their speed, now reaching the upper part of human distribution, while Nordic runners’ progress stagnated for the 800 m race and declined for the 1500 m race in the past 40 years.
• This regional distribution and trends in humans indicate environmental factors playing an essential part in speed progression besides genetic factors. Environmental influences might include altitudinal training, diet, lifestyle, or access to training facilities and methodology.

Future Progression

• The research concludes that even though the forces affecting speed progression in dogs and horses differ from those in humans, further progress in all three species is expected to be extremely limited due to the observed plateau in maximal running speed. It suggests that peak possible speeds may already have been reached, beyond which further improvement may be too challenging even with advanced training techniques or potential advances in genetics.