I would check out your warm-up as a first priority. If your legs are burning at the start of a race, then get better, then you are not warmed up properly. You should feel like you have been doing a bit of work before you start.
If it's generally feeling tired, sick etc, check out pre-race preparations like nutrition and sleep. If I haven't slept well I not only feel tired, but I often feel sick up to the first hour of high-intensity riding - although this usually passes by about 40min.
For food, I generally eat rice balls (I'm in Japan) or pasta with a light, non-fatty sauce (I usually make a big batch of pasta salad about a day or 2 before, then a bunch of rice balls the day before).
I actually have more experience with training and racing for kayaking, but find the same principles apply. I find for the first 30mins of paddling I feel like ****, then I feel good (my average training paddles were around 4-6h when I was training hard). Try and get through this **** feeling BEFORE the race (ie the warmup), rather than during.
If it's generally feeling tired, sick etc, check out pre-race preparations like nutrition and sleep. If I haven't slept well I not only feel tired, but I often feel sick up to the first hour of high-intensity riding - although this usually passes by about 40min.
For food, I generally eat rice balls (I'm in Japan) or pasta with a light, non-fatty sauce (I usually make a big batch of pasta salad about a day or 2 before, then a bunch of rice balls the day before).
I actually have more experience with training and racing for kayaking, but find the same principles apply. I find for the first 30mins of paddling I feel like ****, then I feel good (my average training paddles were around 4-6h when I was training hard). Try and get through this **** feeling BEFORE the race (ie the warmup), rather than during.