Nutrition in Combat Sports

278 W. Pieter
Valuable information was provided by Koh and Watkinson [80] when they also
identified the exact side of the head and face that was hit. Without subsequent concussion,
the head blows were mainly directed at the side of the head: 80% in the men and
86.4% in the women. This was also true when a cerebral concussion followed the
head blow: 35.7% in the men and 85.7% in the women. The men were also concussed
by blows to the center of the face and lower jaw: 28.6% each.
Pieter et al. [89] found attacking with the roundhouse kick in males and blocking
this kick in females to be the main situation in time-loss injuries with delivering the
roundhouse kick and receiving the kick the main mechanisms in males and females,
respectively. As mentioned above, spinning kicks, such as the roundhouse kick, were
suggested to have the greatest injury potential, especially soft tissue injury, by virtue
of the higher velocities generated with these kicks [40] . It is estimated that velocities
of 11 m s −1 have a negligible probability of leading to severe, i.e., time-loss injury,
while those exceeding 19 m s −1 have a 100% chance of causing damage [41] .
Although females recorded roundhouse kick velocities of around 11.0–13.3 m·s −1
and those of males ranged between 15.9 and 22.9 m.s −1 [22, 37– 40] , it was also suggested
that velocities of 8 m.s −1 would result in peak acceleration of the head of 200
G, provided there is no deflection [93] . Foot padding was found to increase peak acceleration
of the head, especially when kicking the side of the head [94] , which was
reported by Koh and Watkinson [80] to be the impact site of the majority of head blows
leading to cerebral concussion. The roundhouse kick to the midsection of the body was
faster than to the head. Sung et al. [37] reported a velocity of 21.61 m.s −1 for the kick
to the head, although, as expected, it will take longer to execute [95, 96] .
Rotational techniques, such as the roundhouse kick and spinning kicks, are suggested
to lead to higher head accelerations [93, 94] and subsequent cerebral concussions
[97] . About 48.5% of all techniques involved in head blows at the 1999 World
Championships were rotational kicks [85] , while 63.6% of all head blows resulting
in concussion were the result of rotational kicks at the 2001 Canadian national
championships [80] . Pieter et al. [69] reported similar findings for both time-loss
injuries and cerebral concussions, i.e., rotational kicks were involved in the majority
of those injuries.
The injury potential of the axe kick is suggested to depend on the execution of
the kick. In the classical version of the kick, the leg is kept straight in both the
upswing and downswing phases, which may lead to injury [98] . As alluded to
above, the axe kick was involved in head blows as well as concussions [80, 85] .
Pieter and Zemper [90] suggested that cervical hyperextension may occur as a
result of the axe kick, which may lead to cervical spine injuries. The spinning back
kick may, in its translational phase, also lead to cervical hyperextension and subsequently
to cerebral concussion as was reported by Pieter et al. [69] .
Koh and Watkinson [85] revealed that 51% of all head blows came from the axe
kick, which may be performed by either the front or back leg. Most second head blows
were the result of the axe kick (70%), as mentioned above. More than half of all head
blows (57%) were executed with the leading leg. Korean elite male taekwondo-in
recorded a performance time of 0.921 s for the back leg axe kick with a maximal foot
velocity of 11.3 m.s −1 [37] .