Lack of Energy after 25 min. Bonking? Overating? Dehydration?

I don't know the name for it or exactly what happened, but today's bicycle ride was among the worst I've had in some time.

First 25 minutes or so (after a 15 minute warm-up) I felt OK and was going at about 98% of FTP. I just did a one hour time trial earlier in the week to confirm the FTP so I felt comfortable about that FTP number.

After the first 25 minutes though, my legs just started to feel like wood or possibly lead They almost felt numb - all over really - and my cadence kept getting slower and slower as my speed plummeted. I have never felt so lethargic on a bicycle. By the time I was nearing my home on the way back, I couldn't have been going more than 11 mph.

Now I ate about 400-450 calories (cereal) or so about an 75 minutes before the ride. I also had about 12 ounces of water in the hour before the ride too. This was a mid-morning ride - say about 11 am and I had a protein shake at about 8 am which I usually don't do.

It was a good 10 degrees warmer today during the ride than when I usually go.

I have searched threads here and it sounds like I either bonked or dehydrated or maybe both

I'm trying to figure out what happened so that I can learn from this and not make the same mistake.

Are there some obvious symptoms while cycling of being dehyrdating, bonking, or having overeaten prior to the ride?

First of all, not every day is an 98% FTP training day. Sometimes you just can't sustain a certain wattage due to built up fatigue or other stress factors. On days like that I simply spin home, call it a day, and on the next day pretend it didn't happen. Training goes on.

Secondly, how much you ate before the ride will not impact you (unless it's too much) as much as how much you ate the day before or the day before that. And of course, what you ate matters as well. Could it be that you didn't refuel your muscles shortly after your ride the day before? I usually blame my bad training days of nutritional shortcomings and closely associate recovery with proper refueling.

__________________

Hi - I always eat a good bit of complex carbs (with a bit of protein too) immediately after exercise. I mean immediately as in I have the meal prepped before I leave so when I return I can eat while stretching. So I think I'm prolly OK there, but I may have eaten too much (or too little) today. Not to mention the hydration question which from what I'm reading, too little to drink can have some bad effects.

Yeah I guess maybe I was training 'by power' rather than 'with power' today, as you guys like to say in sticking to the whole 98% of FTP thing. Still, I really did just fall off a cliff at 25 minutes, there was nothing gradual about it

+1 for Piotr's comments. The PM may be good at measuring precise power output, but our bodies aren't mechanical engines that will produce the same power day-in and day-out. My guess is that you are still recovering from your FTP hour effort. Hitting your max for an hour is a tremendous effort that requires a lot of recovery, more than just a couple of days. You can't expect to jump back 2-3 days later and put in the same performance.....hard training is only effective if you allow yourself to fully recover before hitting it again.