All gums blazing for Wales.
Warren Gatland's Six Nations squad are now using a gum shield which covers both the upper and lower jaw after researchers found the new type could prevent the automatic teeth-clenching that the body naturally performs when placed under stress.
Under Armour - the official WRU supplier which produces the new pieces of kit - claims that whenever a sportsman clenches their jaw, the body releases performance-sapping hormones that produce stress, fatigue and distraction. But other experts last night blasted the scientific reasoning for the switch - and even claim that the piece of kit may have a negative effect on the players' performance.
Dr Samuele Marcora, a senior lecturer in exercise physiology, said that preventing jaw-clenching with these new gum shields may actually reduce the performance of the Welsh rugby team.
He said: "Recently published experimental studies proved that clenching the jaw increases muscle strength and power.
"Several experimental studies show that cortisol has a positive effect on endurance performance.
"In fact, endurance athletes use drugs to increase the level of cortisol over and above the cortisol naturally produced by the body- which is called doping.
"Therefore, if it is true that these new gum shields reduce cortisol levels, their effect may be to reduce the stamina of the Welsh rugby squad."