I'm 48, 5' 10'' and weigh 12.5 stone. I get out maybe once or twice a week on my bike, anywhere from 5-17 miles around the Calder valley, with plenty of hills to climb. My problem is I find it a struggle on the steeper climbs and my legs feel like jelly at the top of some cof them whereas the other guys seem to be sprinting away. It's not as if my lungs are collapsing or anything... just the tops of my thighs seem burned out. Any suggestions for either improving my technique, or any exercises that will strengthen my legs?