| Swimming is unsuitable for training Thoroughbred | | | | be trained either for stamina or for speed. A training |
| racehorses but is suitable for endurance horses. The | | | | program which trains the fibres for the wrong energy |
| reason swimming is an excellent exercise for | | | | pathways clearly will reduce performance significantly. |
| endurance rather than racehorses is that swimming | | | | As swimming for training addresses only the slow |
| addresses the slow twitch muscle fibres. A horse | | | | twitch muscle fibres, it should not be used for |
| cannot be trained for both endurance and outright | | | | racehorses unless swimming races are introduced one |
| speed because each type of training has an opposite | | | | day! Research has also shown that swimming must |
| effect on muscle fibres. | | | | be avoided in the case of a racehorse which is a |
| Horses have two distinctly different types of muscle | | | | 'bleeder'. When a horse is swimming, it is harder for |
| fibre types: slow twitch and fast twitch (depending on | | | | them to breathe as most of their chest is submerged. |
| their contraction times). The slow twitch fibres are | | | | It's not wise to make the lungs of a 'bleeder' work |
| designed for endurance and use oxygen. The fast | | | | harder in this way. |
| twitch fibres produce speed, and their energy is | | | | However, swimming is excellent training for endurance |
| obtained through anaerobic pathways. They have very | | | | horses for the cardiovascular system and does not |
| limited endurance capacity. | | | | place stress on legs, muscles and tendons. Scientific |
| Long slow work conditions the slow twitch fibres | | | | studies have shown that swimming is a strenuous |
| (Type 1) which use aerobic pathways. Arabian horses | | | | exercise. Three minutes of swimming is said to be |
| have a far higher proportion of slow twitch fibres than | | | | equivalent to 1 mile (1,600 metres) of steady harness |
| other breeds of horses. Thoroughbred racehorses | | | | or ridden work. Swimming is an excellent conditioning |
| have a high proportion of fast twitch fibres. Slow | | | | procedure because it provides a hard workout while |
| twitch fibres operate on oxygen only and are | | | | avoiding injury to a horse's legs, and for this reason, |
| endurance muscles, able to operate for very long | | | | several leading endurance trainers have included |
| periods without fatigue. Type II fast twitch fibres can | | | | swimming as a supplement to their training routines. |