Q+A: Why did my heart rate shoot up 40 beats?

Q During a recent race, while I was running very comfortably, my heart rate suddenly shot up to nearly 40 beats above my usual level and remained there for the rest of the run. At no time did I feel ill or even out of breath, but understandably I was worried. I’ve since seen my GP and am waiting to see a cardiologist, but can you offer an explanation?

A Assuming that your heart rate monitor was not temporarily malfunctioning, and while it’s difficult to comment upon an individual case, I will try to offer an explanation of the commonest cause of unusual heart-rate fluctuations experienced by athletes. Heart palpitations are common in athletes and are usually felt as a regular pounding or racing of the heart in the chest, throat, and/or neck. Some athletes describe it as the heart stopping and then restarting, or a rapid fluttering. Many of the causes are innocent but some do require further specialist investigations.

The heart normally beats in a regular (sinus) rhythm with the upper chambers (atrium) contracting first, followed by the lower chambers (ventricles). The contraction of the heart is facilitated by an intricate ‘wiring’ system that can be examined using an electrocardiogram. Palpitations usually result from a premature contraction of the heart muscle, which causes the symptoms mentioned above. These premature contractions are normally short-lived and the heart quickly returns to its normal rhythm.

The low resting heart rate of many runners may be one of the causes of palpitations. Others include stress, caffeine, alcohol and certain drugs (including some cold cures). Many athletes will experience palpitations, which usually only last a couple of seconds, during their athletic career. Indeed, everyone will experience palpitations at some time in their lives, and the palpitations brought on by strenuous exercise or high emotions are rarely associated with underlying cardiovascular disease.

However if palpitations are a frequent occurrence or continue for many minutes, and/or there are other associated symptoms (such as unusual shortness of breath and sweating, dizziness or fainting) you should consult your doctor. This is especially important if you have a family history of heart disease.

Dr Gregory Whyte, research manager, British Olympic Medical Centre, Northwick Park Hospital, Harrow