Hi i am thinking of entering the newham london run march 27th.have only been run/walking since middle dec 2010,have been doing 3 miles everyother day,mostly speed walking,average time 38mins.tried 6 miles last week(monday),but strained calf muscle on last half mile,rested this week,pain virtually disappeared,do you think it is a good idea to attempt the above considering,i am a complete beginner never entered a run and can only run walk 6miles ?