In the 18mths I've ridden ( 17,500k ), I've had the occassional sore back, or sore ass. Yesterday I put a cpl of hrs in at the spur in my attempt to improve my cornering & fear thereof. I arrived home after my 5hr outing to find myself sore in places I've never been. The back of my neck was killing me, as was both my inner thighs. I felt like I had just returned from a gym workout. The 2 hrs I actually spent going up & down the spur, I concentrated on my lines, my head postion ( pointing my chin at where I wanted to go ), and moving my head/upper body into the corner whilst also weighting the inner footpegs. I am assuming that the reason I am sore could be one of two reasons. 1: Confirmation that I had used my body correctly, using muscles repetitively that are not usually used in 'normal' circumstances ( ie commuting ) 2: I'm just plain unfit. .. or possibly BOTH. I still have trouble with my right-handers, but overall I feel it was a constructive day out.