When I was working out today I felt like I had no energy to do anything. I was on the treadmill and I usually feel full of energy and do it about 60-80 minutes without any problems. Today, I was getting tired too quickly and had to slow down a lot. However I did complete 60 minutes but I didn't burn as much as calories I used to burn.
I had ate good and I don't feel sick.
I wonder what was wrong? Should I drink something before I start working out?