Jump jockeys are arguably the toughest sportsmen around.
Falls are a regular event - even for champion jockey Tony McCoy
They risk serious injury in every race - it has been calculated that on average a jump jockey will suffer a fall once every 10 rides.
In addition, most have to show extreme self-discipline, verging on the unhealthy, when it comes to weight.
Hours are spent in saunas and hot baths in an effort to shed crucial pounds, while eating a square meal is a rare luxury.
There is also the travel factor - driving hundreds of miles each week to courses from Ayr to Exeter.
Because of the shared physical demands and risks, there is a strong camaraderie between jockeys.
Many drive to courses together, socialise together and go on holiday together - although on the racecourse, all are extremely competitive.
The top jockeys earn a good living, but for most it is not a lucrative profession.
They are paid a fixed rate of £103.25 for each ride.
In addition, they earn a percentage of any prize money won.
While this sounds like good money, many riders often only get a handful of rides a week, and often these are not on the best - ie prize money-winning - horses.
Many jockeys have "retainers" with a trainer, or sometimes with an owner.
This means they are paid a separate fee by that trainer/owner, who then has first call on their services.
Most jockeys are professional but there are some amateurs, and some races which are restricted to amateurs - the most famous being the Foxhunters' Chase at the Cheltenham Festival.
Any amateur can be recognised on a racecard because he is always referred to as "Mr J Smith", whereas Richard Johnson's name would appear "R Johnson".
To help jockeys get a foothold in the sport, they can claim a weight allowance in certain races (they are known as conditional jockeys).
They can claim 7lb until they have ridden 20 winners, then 5lb until they have won 40 races and 3lb until they have won 75 races.
There used to be an age limit of 26 on conditional jockeys but this was changed in October, 2003.
There are female jump jockeys but few have enjoyed success at the highest level.