Yesterday I went out on my club's B ride. We had 14 riders, male and female, and we did 56.6 mi. and 3700 ft. elevation. On the way out to mid-point I was hitting the climbs better than I ever do. Putting some effort into it instead of just hanging back which I normally do. After about 20 mi. I decided to go easy to save some for the end of the ride. At the mid-point I was feeling very strong and everything had been effortless. After about 10 mi. on the way back I started to lag. One of the ride leaders, and the strongest rider, told me to get on his wheel. I had been gapped by a couple hundred yards and was losing ground. I couldn't hang on his wheel and was truly confounded at my loss of strength. My legs weren't feeling like jello but my body just didn't want to respond. I guessed I might have been under-fueling even though I felt like I had been doing all the right things up to that point. I had eaten a pack of those gummy things, 2 GUs, a small energy bar, a bottle of water, a bottle of water with GU tab and had a large energy bar and a bottle of water w/GU tab left. So, because I couldn't think of anything else to do to rectify the situation, I ate the energy bar and drank the bottle. After we regrouped I found it easier to hang with the group. As the ride went on I got energy back and by the end of the ride, when people are tending to crank it up, we hit a straight section of road with some rolling hills. At that point I was with the ride leader and 5 other riders. At one point I went by two of the riders and chased the ride leader and two others who had opened a gap. When we hit the last small climb before our start/stop I blew by the others and rode up to the ride leader and smacked him on the ass. He said, "Damn, you're back. Nice." I guess I was. I've never had this happen before but it was encouraging to know that I can recover in the middle of a ride. It was an interesting day. FWIW my ride average was 15 mph.