Equine Science Update
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Cold water spa hydrotherapy.
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A traditional therapy for soft tissue injuries is poised to make a come back according to Prof Evan Hunt. For the past 4 years Hunt, of the University of Sydney, Orange campus in Australia, has been researching the use of cold water hydrotherapy for treating soft tissue injuries. He claims it gives more rapid healing of tendon strain injuries compared with other methods.

The spa has a door at each end through which the horses enters and leaves. Once the doors are closed the spa is filled with water up to just above the horse`s knee. The water level can be taken up to reach the elbow, but the stifle is too high - it would require too much of the horse`s body to be in the water which could lead to hypothermia. The water is then aerated. Each treatment lasts about twenty minutes and would usually be repeated every other day as necessary.

According to Professor Hunt several characteristics of the treatment contribute to its beneficial effects:

Temperature. During the initial studies, water at room temperature was used. This gave a wide variation in temperature throughout the year. Hunt found that the spa gave better results, and the horses seemed more relaxed, during the winter. The spa has now been standardised to work at a temperature of 2- 4º C. "We know that cold has good antibacterial and anti-inflammatory effects" he adds. In humans, cold therapy after arthroscopy markedly reduces swelling and allows for early weight bearing.

Aeration. Water temperature significantly influences the level of dissolved oxygen in the water. Aerated water at temperatures below 4\'ba C has dramatically increased levels of dissolved oxygen. " I`m sure this is one of the reasons we get a response" says Hunt. According to Hunt this is analogous to the use of hyperbaric oxygen in human athletes. The high oxygen pressure increases the uptake of oxygen, not only through the lungs, but also through the skin. He suggests that a similar phenomenon may occur in the hydrotherapy spa, but adds "..we haven`t been able to test whether horses are absorbing oxygen". The agitation also has a massaging effect on the tissues.

Pressure. The pressure due to one metre of water is equivalent to one tenth atmospheric pressure.

Salt concentration. The water contains salts: 20g/l sodium chloride; and 30 g/l magnesium sulphate. This gives the solution a high osmotic pressure and high conductivity - roughly double that of sea water.

Chlorine is added for bacteriological control. Concentrations of 3 - 5ppm free chlorine are used - about twice that of human swimming pools. This is considered safe because it doesn't contact the horses eyes, and considered necessary because there is always some dirt on the horse`s leg when it enters the spa.

To investigate whether horses were stressed when in the spa, Hunt monitored their heart rates. Horses were put in the spa in water either at 4º C or at 15º C, both with or without aeration. He also compared the response of horses that had not been in the spa before and those that had been in more than three times. There were six horses in each treatment group.

He found that horses going into the spa for the first time showed an increase in heart rate after 2 - 3 minutes (corresponding to the water entering the spa and the air being turned on). The heart rate returned to normal more quickly if the water was at 4º C rather than at 15º C. In horses that had been in the spa three or more times he found that aerated water at 4º C gave significantly lower heart rates than the other groups. The combination of cold water and aeration seemed to have a calming effect on the horses.

According to Prof Hunt numerous cases of soft tissue injury have responded more rapidly than expected. Because of the nature of the cases it was not possible to carry out controlled trials. He points out "in all of the cases I`ve looked at I`ve had to compare the rate of response with my previous experience. Hydrotherapy is certainly helping in tendon and ligament cases, and in soft tissue injuries"

Sixty-five cases of acute tendon or ligament strain have responded well. Typically they would receive the spa treatment three times a week for three to four weeks. After seven days, healing changes were apparent on a tendon scan. "Core lesions" were getting smaller. Many tendon injury cases have returned to racing in 14 - 28 weeks. The more severe the case, the longer the recovery. A few cases have not recovered to undertake the previous level of activity, but all have returned to an improved life-style.

Cold water hydrotherapy has proved useful for promoting healing after operations. Suture lines healed more rapidly as a result of the reduced swelling when treated two days after surgery. After arthroscopy, cold water therapy reduced swelling and pain and gave more rapid recovery. It has also been used successfully for reducing oedema (swelling), and encouraging chronic wounds to heal.

Incidentally Prof Hunt has noticed that the spa helps treat mud fever - although he admits that there are probably better ways of treating the condition than using the spa.

"One of the side effects we`re finding with all the horses that go through the spa is that it increases hoof growth" reports Hunt. He has not done any studies on the rate of hoof growth - but says that farriers reckon it may double the rate of hoof growth .

"We have not researched the field of preventative use - but I think it will be useful." says Hunt. "My own two-year olds have gone through the spa and have not had sore shins - which was a first. It appears that it may improve bone density."


source: presentation atYorkshire Equine Clinic 2002