The effect of head cooling on cognitive functioning in kickboxing; a pilot study.

Kickboxing is a combat sport, which consists mainly of kicking and punching.
It is accompanied by a high rate of injuries (390.1 per 1000 athlete-exposures
(AEs)), of which the head (57.8%) and lower limb (26.1%) are most frequently
affected (Lystad, 2015). That study also reported that 29.6% of all contests
were ended by technical knock-out (TKO), which means that a fight is stopped by
the referee or the ringside doctor. Knock-out (KO) occurred in 10.7% of the
cases (Lystad, 2015). Another study reported that of the fights ended by TKO in
an other combat sport, i.e. mixed martial arts (MMA), 90% was ended because of
head trauma due to repetitive striking in which the athlete was not able to
defend himself anymore (Hutchison et al., 2014). A study from Zazryn and
colleagues reported similar numbers regarding injury site. In that study, 51.6%
of all injuries that occurred during kickboxing were caused by injuries to the
head, neck and face, followed by injuries to the lower extremity (39.8%)
(Zazryn et al., 2003). These data emphasize that the head is an important
target in kickboxing. This could result in a concussion and subsequently to
traumatic brain injury (TBI) (Tanriverdi et al., 2007). One study investigated
the type of injuries leading to the end of a match amongst amateur kickboxers,
who where working in the U.S. military. Their results show that 65.2% of the
injuries that forced the referee to end match was due to TBI (20.3% of a total
of 74 matches) (Buse and Wood, 2006).
In sum, the high rate of head injuries in kickboxing due to repetitive head
trauma is clinical relevant, as it may lead to, among others, a decline in
cognitive functioning. Various brain areas that play a crucial role in
cognitive functioning, i.e. the thalamus, basal ganglia and hippocampus, can be
damaged (Lystad, 2015). A decline in volume of brain structures, such as the
thalamus and caudate nucleus has been reported as a consequence of repetitive
head trauma in boxers and MMA fighters (Bernick et al., 2015). They also showed
that the more an athlete has experienced head trauma, the greater the risk of
developing cognitive impairment, especially a decline in processing speed
(Bernick et al., 2015).
The question arises whether an intervention applied directly after the injury,
may limit its neuronal consequences. For example, a possible beneficial effect
on the neurological outcome after TBI has been seen after head cooling (Rupich,
2009). Head cooling took place by introducing a mild hypothermia, resulting in
an intracranial temperature of 32-35°C (Rupich, 2009). The rationale
underlying this application is that after TBI, inflammation, apoptosis and
excitotoxicity causes brain damage and that the temperature of the brain
increases (Harris et al., 2012). This may worsen neurological outcome.
Selective brain cooling, i.e. by a cooling helmet, could be beneficial. It
might reduce further damage to the brain by lowering the intracranial pressure
(ICP) and brain temperature, increase cerebral perfusing pressure (CPP) and
reduce brain oedema, inflammatory response and metabolic rate (Rupich, 2009;
Harris et al., 2012).

The goal of the present study is to investigate the effect of head cooling
after kickboxing matches on cognitive functioning amongst both amateur and
professional kickboxers. Based on the above mentioned studies, it is
hypothesized that head cooling, applied directly after the match, may limit the
negative consequences of TBI on cognitive functioning.

A prospective, single-blind, randomized, controlled, clinical trial.

A cooling helmet from The Game Ready System will be used. It will be applied
directly after a kickboxing match for 45 minutes. A study reports that within
30-40 minutes after applying a cooling helmet, like the cooling helmet of the
Game Ready System, the intracranial temperature will have been reduced to 35°C
(Gladen et al., 2014).
The Game Ready System (CoolSystems: Alameda, California) simultaneously
delivers both adjustable continuous-flow cold therapy and intermittent
compression through a portable control unit filled with ice and with water and
anatomically designed wraps.
The GRS has four pressure settings; no pressure, low pressure (5-15 mmHg),
medium pressure (5-50 mmHg) and high pressure (5-75 mmHg). Temperature can also
be adjusted and is indicated by one, two or three snowflakes. If tolerated, we
will use the coldest setting which is 3 snowflakes corresponding with a minimal
temperature of 4.0°C. We will start with the lowest pressure setting and
increase the setting stepwise. Cold or pressure settings are reduced if
requested by the patient.

The experimental group will be treated with a cooling helmet of the GRS. There
is a small risk of complications associated with this cooling helmet
(0.00225%). These are minor complications, i.e. small skin lacerations.
The potential benefits, when applying the cooling helmet, could be a less
decline in or preservation of cognitive function by reducing brain temperature
and therefore brain oedema and other negative consequences of repetitive head
striking. A quicker recovery of concussion and other brain injuries and
therefore a less recovery time to *return to play* is expected.