Marr is a fairly high profile journalist / TV presenter in the UK. He suffered a stroke a few months ago that he is now blaming on interval training on the Concept 2.
Marr said he had followed the advice to "take very intensive exercise in short bursts – and that's the way to health … I went on a rowing machine and gave it everything I had, and had a strange feeling afterwards – a blinding headache, and flashes of light – served out the family meal, went to bed, [then] woke up the next morning lying on the floor unable to move".
As usual, the NHS piece is pretty balanced, although it is a little concerning the way in which the medics talk about the potential dangers of interval training:
"Regular exercise is an important factor in stroke prevention and recovery. We have heard anecdotally that some activities like vigorous exercise can sometimes cause blood vessels to burst. We need more research on the underlying factors that might make that happen.
"We do know that high blood pressure itself is the single biggest cause of stroke. Until more research is done on specific triggers, we'd suggest getting your blood pressure checked and taking steps to keep it under control – exercise can help with that."
Maybe there was more to it though:
Despite the media emphasis on the stroke risk exercise could pose, it should also be borne in mind that Andrew Marr has said that he had been "heavily overworked". Stress is a known risk factor for high blood pressure, and it is possible that this may have played a part in his condition.