Keeping our horses’ legs cool has always been our mission at Cryochaps. Therefore, we made it our aim to not only cool horses’ legs down after exercise but to also keep the leg as cool as possible during exercise.
When we exercise our horses, the tendons in the lower leg act as coiled springs. As the hoof lands, the superficial digital flexor tendon (SDFT) is stretched as the fetlock joint hyperextends and sinks towards the ground. That stretch stores the energy until the hoof leaves the ground and the tendon elastically recoils, converting most of the stored energy back to kinetic energy, propelling the horse forward. This mechanism actually helps saves muscle energy during exercise too (Alexander, 1988).
The energy stored in the stretch is not all recoverable, and some 5–10% is released as heat. This is the reason our horses’ legs get so hot when we exercise and this, combined with the insulating effect of boots and bandages, could be a concern. So how hot do the legs get? Temperatures as high as 45°C have been recorded in the core of this tendon during gallop exercise, while the tendon surface temperature plateaued at 5°C lower, at 40°C (Wilson and Goodship, 1994).
In the huge amount of testing that Cryochaps have carried out using temperature loggers placed in the mid region of the lower leg underneath boots or bandages, we have seen surface leg temperatures rise as high as 39 degrees. This indicates that the core tendon temperatures could indeed be getting to levels as high as 45 °C. This temperature rise is usually associated with cantering, but if the horse is wearing boots and bandages the leg cannot cool itself when the horse slows back to trot and walk and these high temperatures can remain for some time.
There is clear evidence from two unrelated studies that in the lab, these temperatures are seen to affect the survival of the tendon cells (Birch et al. 1997; Hosaka et al. 2006). After 10 minutes of heating at 45°C, the tendon cell survival fraction was 91%, whereas heating for 10 min at 48°C resulted in a drop in the cell survival fraction to 22%. The study concluded that while temperatures experienced in the central core of the SDFT in vivo are unlikely to result in tendon cell death, repeated hyperthermic insults may compromise cell metabolism of matrix components, resulting in tendon central core degeneration (Birch et al. 1997).
The Exoskeleton brushing boots for horses uses a process known as forced convection cooling. As the leg moves forward through the flight phase, the horse’s tendons and ligaments relax, making an air gap at the back between the leg and the boot. This allows air to be forced over the back of the leg as it is channelled between the vents, cooling the rear of the leg where most heat build-up is created. The spacer fabric covering the holes is used a lot in the medical and defence industry to reduce the heat build-up of our bodies. It allows the air to circulate through the boot, wicking away moisture but also providing cushioning to help with protection. The Exoskeleton exercise boot provides superior patented ventilation, and as exercise intensity increases so does the convective cooling.
For protection, the external skeleton is the lightweight armour. It is able to withstand high and repeated impact, with maximum durability. Strike areas are fully protected by both the external and internal materials. The internal secondary strike protection is provided by a specialised blended polymer, giving softness, flexibility and hardiness. It can deform under sudden or sustained impact and revert to its original dimensions without damage, providing ultimate shock absorption. It does not hold water or sweat so keeps the boot lightweight during intense exercise.
We would always recommend removing tendon boots as quickly as you can after exercise and there is always a role for cooling the legs with ice boots for horses, such as Cryochaps, to help promote recovery after exercise.