• I'd say try it at 160bpm. If you complete that, move up to 165bpm next week; and so on - until it gets desperately hard to complete both efforts, or you bail during the second one, at which point stop adding 5bpm.

    You'll need to do it weekly, and preferably twice weekly, for a couple of months. If you keep records of each workout, you should be able to bask in improved fitness when 8 weeks are up. And maybe allow yourself an easier week somewhere in the middle e.g. do 2 x 10 instead.

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