The body is able to maintain a stable core body temperature in a range of environments. This process – called thermoregulation – balances heat production and heat loss to the environment. Two important mechanisms involved in heat loss are the evaporation of sweat and the control of blood flow to the skin. But what happens if your whole body can’t do this? This is the situation people with spinal-cord injuries face.
People with a spinal-cord injury are not able to produce sweat or control blood flow below the level of their spinal injury. The extent of the thermoregulatory impairment depends on the level of the injury. For instance, the higher the spinal injury, the smaller the body surface that is able to sweat and so the greater the thermoregulatory impairment.
When able-bodied people exercise, a large amount of energy is released as heat (about 80% depending on the activity) causing a disturbance of heat balance. To stabilise core body temperature, skin blood flow and sweating are raised. But what happens when athletes with a spinal-cord injury exercise?
Previously, researchers have only investigated the thermoregulatory responses of people with a spinal-cord injury during continuous, steady-state exercise in warm environments. This doesn’t represent the nature or the environmental conditions of the sports many people with a spinal-cord injury play. For example, both wheelchair basketball and wheelchair rugby are played indoors in air-conditioned sport halls. Also, the exercise isn’t steady state, it involves intermittent, short bursts of activity.
A recent study from our lab has revealed that even at 20°C (typical ambient temperature of a sports hall) during intermittent sprint wheelchair exercise, athletes with tetraplegia – injury to the cervical (upper) region of the spine – experience a continual increase in core body temperature. Despite similar external workloads, core body temperature plateaued in people with paraplegia – injury to the thoracic or lumbar (lower) portions of the spinal cord. Even though both groups had a spinal-cord injury, large differences in their thermal response were apparent due to differences in their heat-loss capacity.
In wheelchair rugby, any person with an impairment to all four limbs can participate, including players with tetraplegia. Unpublished results from our lab have shown that, during a match, despite players with tetraplegia covering about 17% less distance and pushing on average about 10% slower than players with other physical impairments, their core body temperature increased by a much larger amount.
Cooling but no performance boost
In the able-bodied, cooling strategies have been heavily researched, but the same can’t be said for athletes with a spinal-cord injury, despite their thermoregulatory impairment. Previous studies on cooling methods for athletes with spinal injuries hasn’t considered whether or not they are practical. For instance, applying hand cooling during breaks in play is not practical for wheelchair athletes as their hand dexterity would be severely affected.
Two methods that are commonly used by athletes with a spinal-cord injury are the use of water sprays between breaks in play and the application of ice vests before exercise (pre-cooling). We recently investigated how effective these methods are at reducing the rise in core body temperature and the effect on wheelchair rugby performance.
We found that water spraying between breaks in play combined with pre-cooling with an ice vest lowered core body temperature to a greater degree than pre-cooling only or no cooling at all. Surprisingly, even pre-cooling only led to a lower increase in core body temperature throughout the 60 minutes of exercise compared with no-cooling. Despite this, neither cooling condition had a positive effect on wheelchair rugby performance. We currently don’t know how effective just water spraying is or whether other cooling methods used by able-bodied athletes could be more beneficial.
The specific sporting regulations and logistics of administering a cooling method need to be carefully considered. In the absence of evidence and large physiological differences between individuals, sport scientists and coaches should take an individualised approach when refining a cooling strategy for athletes with a spinal-cord injury and conduct their own tests prior to use in competition.
So look out for these athletes at Rio trying their best to keep cool.