They contradict Thommo's claims.
To summarise, the results of this study show that jockeys in
more advanced placings at the 400 and 200 m positions before the
post in races whip their horses more frequently. To gain the
advantageous placings at 400 m positions, no horses were whipped
while between the 400 and 200 m positions only half were
whipped. On average, they achieved highest speeds when there
was no whip use, and the increased whip use was most frequent in
fatigued horses. That increased whip use was not associated with
significant maintenance of velocity as a predictor of superior race
placing at the finish of the race. Further studies with on-board
sensors of gait characteristics are required to study responses to
whipping in individual horses.
The authors conclude that, under an ethical framework that
considers costs paid by horses against benefits accrued by humans
[11], these data make whipping tired horses in the name of sport
very difficult to justify. However, it is worth noting that other
ethical frameworks would not condone the practice even if it did,
contrary to the findings of this study, cause horses to run faster.