WHY DOES MY HEART RATE SPIKE AT THE START OF A RUN / TRAINING?
A lot of athletes see their heart rate spike at the start of a run of training session and then subsides after 5 min. I have noticed that most of these spikes is during early morning training sessions, especially running workouts. This type of spike can be because you did not warm-up properly or long enough.
Before starting exercise your body’s internal machinery works at very low rate. Your metabolism is slow and blood only moves to organs and back to lungs and heart. Muscles are fed with blood by tiny blood vessels existing in the muscle to make sure muscle get supplied by blood. During rest the majority of capillaries and vessels are constricted, so little blood goes to the muscle. Because of this the cardiac output gets reduced. The heart does not need to pump very hard to maintain blood pressure and this gives you a low heart rate.
During exercise the muscle demand a high volume of blood flow. This means that the capillaries should dilate to expand so blood can rush to the muscle. But our bodies is not designed so capillaries dilate before exercise, it expand due to exercise itself. Asking the body to exert from a cold start can be a major stressor to the body, as it needs to drain blood from major organs to the working muscle.
This is why proper warm-up or longer warm-up is important. As if the capillaries have not diluted properly the blood flow to the muscle is weak, which means no oxygen to the muscle and then your body needs to function anaerobically for a few minutes. This is why you sometimes feel very uncomfortable at the beginning, but not really out of breath yet. The heart rate goes down after a few minutes which then means the aerobic system is fully in function.
My suggestions would be to start by first walking a minute and then go into a very slow jog and pick it up from there on wards to make sure you give body the chance to activate fully aerobically. Also do longer warm-ups of 5 – 10 min. If you start your session very early, give your body a chance to wake up. Remember the body also needs to be activated by nervous system firing. Thus proper warm-up is very important.
This blog is written by the coach and athletes associated with Trivium.