Joe O'Connor, fitness coach and strength and conditioning consultant, emphasised this point at the Horse Sport Ireland national coaching conference in November.
Mr O'Connor lectures in the Institute of Technology, Tralee and also runs NISUS fitness, providing fitness lectures and advice to both professional and amateur organisations and athletes.
The fitness expert regularly works with inter-county hurling and football players, but also comes from an equestrian background.
Mr O'Connor told the conference that scientific research has shown that unfit riders can make their horses anxious. Studies have highlighted that when the rider's heart rate goes up, the horse's behaviour score goes down.
He added that there was a significant difference between the elite event rider and the novice rider, in terms of their muscle control and control of head movements.
Studies have shown that advanced riders have more active control of their posture, because they have better control of their deep postural muscles than novice riders.
He advised novice riders to work on their mobility and stability core training to improve their postural control.
Dynamic pilates classes would be an ideal starting point for novice riders who want to improve, he told the 300 delegates at the conference.
Comparing event riders to other athletes, Mr O'Connor said that the constant shifting from one gait to another and the more forward position of the rider during jumping and fast work required postural control, tonic arm control and thigh muscle activity to keep the rider in balance.
The fitness expert advised riders who were serious about improving their fitness to purchase a heart rate monitor so that they could keep track of their exertion rates.
According to a 2010 study of female event riders (see Table 1, pg 19), the average heart rate recorded in riders during the dressage phase of a one-day event was 157 beats per minute (bpm).
This rose to 180bpm in the showjumping phase and rose even further to 184bpm in the most physically demanding phase, cross-country.
Oxygen consumption is considered the standard for measuring the physiological intensity of exercise.
In layman's language, if your heart rate is the speedometer, then your oxygen consumption is how much fuel per mile you're burning to achieve a certain speed.
Oxygen consumption is measured in millilitres of oxygen per kilogramme of bodyweight per minute (ml/kg/min).
The event rider study found that oxygen consumption during the dressage phase was 20.4ml/kg/min. This rose to 28.4ml/kg/min in showjumping and 31.24ml/kg/min in the cross-country phase.
"Event riders need to have both efficient hearts and lungs to generate enough oxygen to keep their muscles moving," Mr O'Connor told the conference.
"The showjumping and cross-country elements of the competition are more demanding on the body and fitness.
"Different disciplines require different levels of fitness. But research suggests that event riders need to operate at 75-85 per cent effort."
Table 2 shows the different heart-rate training zones used by fitness trainers to correctly work athletes for their individual sport.
If event riders typically operate at 75-85pc, then they need to train for those conditions, which means exercising both aerobically and anaerobic ally to improve their fitness.
Studies have shown that, compared to other athletes, riders have high thigh strength but low bone density.
Because of this lower bone density, riders are advised not to run for excessive periods on hard surfaces such as roads and tracks. Instead, cycling and swimming are advised for riders, in order to avoid injury.
Mr O'Connor also advised riders to try other forms of exercise to improve their aerobic and anaerobic systems. These include circuit training, zumba classes, body conditioning classes and Tabata training.
Circuit training high-intensity aerobics is a form of body conditioning or resistance training. It is easy to follow and targets strength building as well as muscular endurance.
An exercise 'circuit' is one completion of all prescribed exercises in the programme. Once you have completed one circuit, you start the first exercise again.
Typically the time between exercises in circuit training is short, often with rapid movement to the next exercise.
Zumba is a dance-based aerobic exercise that includes resistance training. Rumba choreography incorporates hip-hop, samba, salsa and belly dancing moves, as well as lunges and squats.
Body conditioning is the exercise and practice to build the body up for either improved normal performance (in the case of return from injury) or in preparation for sports performance. Most gyms offer body conditioning classes.
Tabata training is high-intensity training technique, typically lasting four minutes.
A training session typically includes 20 seconds of intense training, followed by 10 seconds of rest for a total of eight sessions or rounds.
Tabata was named after a Japanese scientist, Izumi Tabata, and his colleagues at a department of physiology in Japan.
In terms of specific strength training for riders, Mr O'Connor recommended both static and mobility-based exercises to strengthen the core muscles. These would include the plank, side plank and bridge exercises.
He also recommended compound exercises such as the overheard squat and the kneeling lunge to shoulder press.
To find out more about rider-specific exercises, the fitness expert referred riders to the website www.functionalmovement.com, where riders can look up:
nActive straight leg release
nTrunk push up
The Kerry-based coach also has his own exercise channel on Youtube, where riders can go to watch a 12-exercise programme designed specifically for equestrian athletes using a stability ball.
It also shows a Tabata training level one session.
Go to Mr O'Connor's Nisusfitness Youtube channel and his website www.nisusfitness.com for more.