Snipers are trained to shoot between Heartbeats:
The reason for this is that snipers don’t want the blood flow to mess up their fingers when aiming and shooting. While this is a smart method, it can become difficult when in harsh conditions, like extreme heat.
As the body gets hotter, the heart rate also increases. However, there are techniques that snipers use to keep their heart rate under control to get the shots they need. For instance, they breathe steadily, relax, clear their mind, and just think about the task at hand.