Exoskeleton Airflow Tendon Boots | The Science
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.
Why do the legs get so hot when the horses exercises?
Tendons produce heat when the horse moves, 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. 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 exercising. Watch the slow motion video of the horses’ leg hitting the ground and see how much the fetlock drops, extending the tendons and ligaments to maximum stretch.
Insulating effect of boots and bandages
Boots and bandages do you need them? The most common reason for use is interference or brushing. “Brushing” refers to contact between opposite (right and left) fore or hind limbs. This can be caused by improper shoeing, conformation, it is also commonly seen in young horses who are still finding their balance under a rider or on the lunge and horses that are exhausted are also more likely to accidentally brush as limbs become fatigued. On the front limbs, brushing usually occurs from the knee to the hoof. On the hind legs, it usually occurs from the fetlock to the hoof. So brushing boots and bandages are sometimes a necessity, but this can lead to sweaty legs as they have an insulating effect.
Temperatures as high as 45°C have been recorded in the core of the tendon during gallop exercise, while the tendon surface temperature plateaued at 5°C lower, at 40°C (Wilson and Goodship, 1994). This study the horses legs were unbooted so you could extrapolate that the tendon temperatures may become higher if the leg is insulated with boots.
Cryochaps have tested and measured alarming temperature rises with what are termed vented boots. External temperature sensors placed over the middle of the tendon at the back of the leg, underneath a set of boots reached over 38°C. This in theory could mean the core tendon temperatures are in the range of temperatures that cause tendon cell death.
What does this mean for our horses legs?
There is clear evidence from two unrelated studies that in the lab, temperatures of 45°C 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 was 91%, whereas heating for 10 min at 48°C resulted in a drop in cell survival 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).
So why is Exoskeleton different?
The Exoskeleton Air flow 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 vents is commonly used for clothing and bandages in the medical and defence industry to reduce heat build-up in humans. Using this fabric as the internal layer of the vented boot allows air to circulate, wicking away moisture but also providing cushioning to help with protection.
The Exoskeleton exercise boot provides superior ventilation, and as exercise intensity increases so does the convective cooling as the air is forced over the leg. This will help keep the leg dry as wet and sweat can freely evaporate, creating a secondary cooling effect.
A graph of tests carried out and how temperatures rise with Exoskeleton (orange) versus a Market leading Vented Tendon Boot (MLTB) when the horse is asked to do 15mins or trot and canter followed by a 5 minute walk off
Between blue circles – The first trot and canter show how the vented MLTB leg temps steadily rise over and above the Exoskeleton
Between yellow circles – Walking, the leg temperatures initially rise and then plateau, as less air is being forced over the back of the leg as the leg is moving at a slower speed
between green circles – When the speed increases again there is a marked drop in temperature inside the Exoskeleton boot compared to vented MLTB as the air is being forced over the back of the leg much more rapidly
Between red circles – Walk off, temperatures initially increase but then start to fall. The Exoskeleton enhances cooling, dropping the leg temperatures to the initial starting temperatures far more quickly than the MLTB as the heat can escape along with moderate air flow to keep cooling.
Exoskeleton maintains temperatures under 36.5 degrees, other boots the surface leg temperatures often rise as high as 39°C. This indicates that the core tendon temperatures could indeed be getting to levels as high as 45 °C if the external temperatures are at 39°C.
Having the exoskeleton armour opened up with large vents, also allows the heat to escape when walking off, so the heat is dispersed much quicker than other boots, limiting the time the internal temperatures are at high levels