What is ridden water submersion training (RWST)?

RWST is a ridden form of condition training that involves submerging the horse up to sternum height in water (at the beach or in an artificial lake) and trotting them for set intervals. While there has been no previous research on this form of training until now, the anecdotal basis behind RWST is to increase the horse’s fitness while minimising the risk of injury to the lower limbs, which is especially relevant to disciplines that have high rates of tendon injuries.

Why use RWST?

The tendons of the lower limb are integral for movement and stability and they are one of the most commonly injured structures in racing, eventing and show jumping. Nearly all tendon injuries occur in the forelimbs, and in 75-93% of reported cases the culprit is often the superficial digital flexor tendon (or ‘SDFT’). Most injuries are thought to occur because of repeated ‘sub-maximal’ bouts of biomechanical stress (due to activities such as jumping and galloping) without sufficient time for the tendon cells to repair in between.

A previous study even found subtle changes in the ultrastructure of the tendon using ultrasound after maximal exercise, despite these internal changes not causing any visible lameness in the horse. The structural changes didn’t return to baseline values until at least 72 hours after the exercise session, highlighting the importance of spreading out training activities that specifically put the SDFT under strain throughout a programme.

A lack of intervals in training leads to a build-up of inflammation, increasing the core temperature of the tendons in subsequent training sessions, leading to rupture and eventually lesions (i.e., scar tissue) on the tendon. Unlike muscle tissue, once a tendon ruptures the structure will never be as strong, and this is highlighted by re-injury rates of between 23-67% within two years of the initial injury using traditional treatment methods.

While new technologies such as stem cell treatment are becoming more popular, the cost and management implications of this treatment can be considerable for owners. As such, prevention is certainly better than cure. We already see a growing awareness of the benefits of cryotherapy in the equine industry. Various water-based training programmes (such as water treadmills and swimming) are also growing in popularity due to the benefits of this type of exercise in horses.

The use of these commercial facilities can be of limited use to owners/trainers however, due to geographic or financial constraints. Furthermore, these forms of training can be limited in their ability to increase the fitness of the animal, and so are often only applicable to the earlier stages of a fitness training programme or post-injury rehabilitation. In contrast, RWST is carried out under saddle and so the pace can be controlled by the rider, ensuring that the horse is working at a level to either maintain or increase fitness.

What happened in this study?

In this particular study, 15 performance horses from Karin Donckers’ Stables were recruited and measurements were taken during a RWST training session. Karin Donckers is an Olympic eventer who has competed in six Olympic Games. Karin uses RWST regularly as part of her condition training programmes. She is currently ranked fifth in the FEI Rankings for South Western Europe, and 71st globally.

The horses regularly underwent RWST as part of their training programme and were competing at between 3* and 5* international eventing level at the time of the study. The horses were transported to their local training venue and underwent a standardised warm-up phase in all three paces on inclining/declining land over a 25 minute period. They were then submerged up to the base of their sternum in an artificial lake and trotted for set intervals in the water (either 3x3 min or 3x4 min, depending on their current fitness level) by their regular exercise rider, with a one-minute break between each interval.

Once completed, horses underwent a final cool down phase in the water in walk. Heart rate monitors were used to quantify the workload of the session and thermal imaging cameras were used to measure distal limb temperatures.

What did researchers find?

Overall, the study found that RWST, on average, produced a heart rate max (HRmax) of approximately 65% in this group of elite event horses. This equates to 65% of the total capacity that the heart can produce in beats per minute. It is important to remember that as a horse gets fitter, their heart rate decreases due to hypertrophy (increase in muscle mass). Therefore, as a horse gets fitter, their heart rate (and HRmax) decreases when completing a particular activity each time, meaning they can go faster/for longer as they become fitter.

As such, the horses used in this study were already at peak fitness levels in elite eventing, meaning that RWST is likely to be a much more intensive form of training for non-elite performance horses, as well as horses who have never undergone RWST before.Therefore, we always recommend that trainers introduce this form of training slowly, and use heart rate monitors when using RWST so that objective measures can be used to tailor training sessions to the individual and reduce chances of injury/fatigue.

In addition to the cardiovascular response to training, thermal imaging showed a stark contrast in distal limb temperature responses when compared to condition training on land. Where previous studies have reported an increase in tendon temperature during gallop over time, RWST produced a significant decrease in distal limb temperature between the warm-up phase on land and RWST in water. This means that in contrast to more traditional forms of condition training, RWST decreases distal limb temperature, potentially limiting tendon temperature increase that commonly precedes tendon rupture. While further research is still needed to fully establish the effects of RWST in horses, this form of training could provide trainers with an additional form of condition training that can limit the increase of distal limb temperature.

Recommendations:

1. RWST could provide a useful adjunct (not alternative) to current forms of condition training utilised in equestrian disciplines that involve a high level of tendon injury

2. Training sessions that cause a lot of biomechanical strain to the tendons (such as jumping or galloping) should not occur within three days of each other.

3. Condition training sessions should ideally be spaced out every fifth day and should incorporate a good level of variety (hill training, interval training, RWST).

4. Condition training sessions should be monitored using heart rate monitors so that workload can be accurately assessed, injuries avoided due to fatigue and any health issues can be detected at an early stage.

5. The effects of RWST on the musculature of the horse are yet to be studied.

About the author

Claire O’ Brien studied the physiological effects of RWST as part of her MRes in Biological Sciences at the University of Portsmouth. She is now completing a PhD in Biological Sciences which specialises in Equine Cognition and Behaviour. She has lectured in equine science and equestrian performance management in the UK for four years and is also a BHS-accredited coach and trainer.