Let look into a suddenly Hart Rate jump when doing Sport, we have 2 explanations ready

Ok we count on that the Hart rate monitor was not malfunctioning, while it’s difficult to comment upon each individual case, unusual heart-rate fluctuations or sudden jump in Hart rate experienced by athletes could be Hart palpitations which are common in athletes, which is usually felt as a regular pounding or racing of the heart, when you feel your puls you can feel there is more action than usual.