Nitrate power! Run to the beet (beetroot beets!) and benefit from greater endurance and speed.
We have personally tested this, drinking pure beet juice before a 10 km race.
We drank 100ml of pure beetroot juice about 45 minutes before the start of the race and were shocked at the endurance boost in the last couple of km.
It definitely worked for us. Give it a go and let us know how you get on!
~ Cyprus Ultra team