Felt rubbish on the treadmill this lunchtime and in the search for an excuse it occurred to me - does breathing pretty heavily in exactly the same spot for a period of time deplete the oxygen around you? I know you'll all say "who cares - run outside" but a 40minute London lunch run = 20m waiting at traffic lights and 20m dodging tourists - what do you reckon?

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"Are you sure we're going fast enough?" - Emil Zatopek