Took 2 before a recent 10k and 2 during - felt good and achieved a 75+ PB of 59:22. I shall order more. Only comment is that the packet suggests 4 chews 5 minutes before activity. You need more than 5 minutes to get comfortably through 4 chews. But this is just something you learn. Excellent product and the strawberry chews are quite tasty.