I could use a little insight here. But, first a bit of history. Two weeks ago on a club ride we did 48 mi. at about 15 mph and 2,000 ft of elevation. At the end of the ride I got up to the ride leader (50 yrs. old, ex-racer and zero body fat as far as I can tell! ) and said, "How about if I give you a lead out to the end?" We were about 100 yds. from the finish. So, I jumped and he held onto my wheel. When he started to slingshot past me I picked up my pace as best I could. He couldn't lose me and turned and said, "That's all I've got." I said, "Me too" and we rode in together. It was really a nice moment. FWIW, I'm 64 and about 190 lbs which is 15 lbs over my best cycling weight.
So, yesterday the club ride went out for 57 mi. at about 14.9 mph thanks to 3,000 ft of elevation. As you might imagine, thanks to that extra 15 lbs, hills are not my friends. With about 5 mi. to finish, the group started dropping me on hills. Not by a tremendous amount but significantly. The same group leader and another really strong rider took turns dragging me up to the group. Strangely, once over the hill I actually could crank it up and catch the group although it was work. With a mile or two to go I couldn't stand to pedal thanks to quads in spasm. During the ride I consumed two GU gels, two bottle of Gatorade and a cranberry scone. Just trying to get some insight as to why I lost my legs. I should mention that at no time did my lungs or heart feel particulary stressed. Anyone? TIA