I am a fit 67 year old and regularly take part in cycling sportives, both road and cross country. On three occasions recently I have experience rapid pulse rate at rest after 100 mile sportives.
My normal resting pulse is around 45-48, but after the ride 3 hours yesterday it was 103. During the 9 hour ride I drank 4.5 liters of fluid containing electrolye powder and also took caffiene gels.
Once it was still at 93 after a nights sleep.
A visit to ER was given the " Too old and too much exercise" talk but no cardiac investigation or other explanation.
At this moment, post 15 hours it has reduced to 55.
Any ideas on what is causing this?