No, those are not butterflies in your stomach when you toe the line at a triathlon start and are waiting for the gun — that is one of the symptoms from adrenaline: when one is nervous, blood is pulled away from the stomach and sent into the muscles.
Adrenalin is a “fight” hormone, and plays a central role in the short-term stress reaction. It is released from the adrenal glands when danger threatens or in an emergency. Such triggers may be threatening, exciting, or environmental stressor conditions such as a triathlon start!
When secreted into the bloodstream, it rapidly prepares the body for action in emergency situations. The hormone boosts the supply of oxygen and glucose to the brain and muscles, while suppressing other non-emergency bodily processes (digestion in particular). This reduced blood flow, in turn, causes the stomach to temporarily shut down.
Adrenaline has the opposite effect of insulin. The resulting rise in blood sugar enables the fermentation of glucose in the muscles. Adrenaline furthermore reinforces these effects, because it increases the secretion of glucagon (a hormone with the same effects as adrenaline) and decreases the release of insulin.
As a diabetic, I had no natural insulin to counter-effect this process when I was racing (who doesn’t get nervous before a triathlon anyway?), so it took me many races of super high blood glucose levels to really understand that no matter how low my sugar leves were BEFORE THE START, once I was on the bike, it had skyrocketed!! There were a few times that my glucometer read “HI” — that means the levels were so high that the meter couldn’t read it.
Once I was 100% sure this wasn’t a one-off process, I started to give myself a huge amount of insulin as soon as I jumped on the bike — to be more precise, eight (8) units of fast-acting insulin, more than enough to cover 120grams of carbohydrate in a “normal” situation. Now if you are diabetic you understand why it took me so many races of high glucose levels to be confident enough and inject 8u of insulin before even testing that. Outside of racing it would have killed me or at best, put me in a hypoglycemia coma (no sugar available for the brain).
Once with this part figured out and controlled, I got into that “steady-state” in pacing where I had no more pre-start tension and was focused on the race; my blood levels were not affected my adrenalin anymore and I could go back to my good old “calories VS insulin” combination.
And what can the “non-diabetic” learn from this?
— Race start: Don’t over do it in the gels and sports drinks. Even if your sugar level is low, it will raise some in those last 5 minutes before the race start. I remember when I first started racing, I use to wear a Heart Rate monitor, 130bpm while just there, standing waiting for the start, wasn’t a surprise.
— First few minutes on the bike: DO NOT EAT – No calories at all, not even sports drinks or energy gels, not only there is very limited blood that will access your stomach at this stage to digest and absorb anything, but since capillaries in arms are open and in legs are closed, your heart is forced to work hard to pump to legs. Start the bike EASY (VERY EASY if in an ironman) for the first few minutes to let capillaries in arms shut down and legs open up; blood sugar get stable, adrenalin loses effect, then eat/drink.
Be aware of your hormones, race faster!