Basically, I’m 65, I’m trying to improve stamina ,rather than speed. I’m doing about 75 miles a week, mostly on the trans-pennine trail, with no technical riding at the minute (not much available locally),having had a small stroke 10 years ago, a serum cholesterol which reached double figures, and a cardiac angiogram showing narrowing of the cardiac arteries 7 years ago, I’m very wary about overdoing things. I’ve done Polarises and mountain bike orienteering in the past,but not for years, and I worry about overtraining causing more problems, so was pleased MHR was so high. Since I started riding again, my cholesterol and BP are within normal limits,so something is working.