From "This is the Spanish Horse" written by Juan Llamas Perdigo…

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"In the 17th century, referring to multi-kilometer races, William Cavendish said, "They were so much faster than all other horses known at that time that none was ever seen to come close to them, even in the many remarkable races that were run."

 

In 1831, horses at five years old were expected to be able to gallop, without changing pace, four or five leagues, about 12 to 15 miles (19 to 24 km). By 1925, the Portuguese military expected horses to "cover 40 km over uneven terrain at a minimum speed of 10 km/h, and to gallop a flat course of 8 km at a minimum speed of 800 metres per minute carrying a weight of at least 70 kg", and the Spanish military had similar standards."

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