Sorry, you will not like me for saying this but we are talking 6 weeks. You should have stopped the run as soon as your calf 'tweeked'. You can maintain your fitness by cross-training but running is out of the question until you are pain free
Thank you very much for your prompt answer SideBurn. Your answer is very helpful and has clarified what I thought i.e.. power output continues beyond VO2 max but using the anaerobic (lactic acid) pathway.