Arrhythmia when exersicing at moderate intensity

[ArizonaHarry]

Some 4 months ago I started experiencing some mild, but still clearly distinguisable, arrhythmia, when exercising moderately  on my recumbent bike. From stable heart rates at 115-120bpm the rate would suddenly jump to 145-150bpm. After 2-3 minutes rates would gradually return to 115-120bmp. Some times this happens only once during the workout, but most often it repeats itself 2-6 times. All this happens while resistance level is stable. This has now happened many times, and I am 100% sure it is not due to malfunctioning of the monitor.

Apart from feeling more shortbreathness for the few minutes the arrhythmia last it is really not bothering me. I have experienced no kind of arrhythmia at more intense exercise levels or when resting.

I've done both moderate and intensive exercise on the same bike for several years, and can say with certainty that this never used to occur before it started 4 months ago.

Looking for advice on what to do, and whether to continue exercising.

[Bromley]

You could also capture this via portable heart monitor.

[kenkeith]

It seems you have an arrhythmia during exercise (faster heart rate than expected), and probably have the same underlying cause as arrhythmia (faster than normal heart rate) at rest. That would indicate the arrhythmia is triggered by a fast heart rate.

For some insight, physical exercise is related to vagal modulation of HR during exercise independent of aging. Experimental data have shown that vagal activity prevents ventricular fibrillation during exercise and that exercise training confers anticipatory protection from sudden death by enhancing cardiovascular autonomic function... damage to the vagus nerve my decrease parasympathetic tone and allow increases in heart rate...cardiac vagal modulation dysfunction. There could be a hyperthyroidism condition.

If you are experiencing a faster than expected heart rate, you would want to eliminate a potential abnormaility that could put your heart rate into a dangerous range that could damage your heart muscle, etc.

Mayo Clinic: "There is also experimental and clinical evidence that augmented sympathetic outflow is related to arrhythmogenesis and cardiovascular morbidity and mortality (20, 21). Rapid loss of vagal activity followed by sympathetic activation during mild-to-moderate exercise intensity may be one potential mechanism for adverse clinical events, and the present data support the concept that good aerobic fitness may exert cardioprotective effects by enhancing the cardiac vagal function during exercise".

You may want to see a doctor, and if the problem is consistant with exercise, a stress test would be able to diagnose.  
Thanks for sharing, take care.