Endurance...

On the subject of endurance.....it seems like some days I've just got it, and some days, I just DON'T. Really strange. When I first started exercising I could only last for about 30 minutes tops-and that was usually WALKING on the treadmill. Over the course of the past 5 years, my endurance and intensity have increased gradually-as I would have expected it would. Last year when I did the Beachbody program INSANITY, I can say I was very proud of how far I've come. It was a gigantic step up the ladder to be able to complete one of THOSE workouts...and I was doing it!
BUT...
Over the last year something has changed. There is no gradual climb anymore...it's more like the hiccups now. Most days I feel mentally "ready" but sometimes my body just doesn't agree. And not just to the point where I have to "get out of my head about it" and just push through...I'm talking I. Cannot. Get. My. Body. To. Move. What is up with THAT?
MANY times in the past month or two I've been in a group fitness class where the teacher was instructing us to do a particular thing and in my mind, I was doing it-or going to do it...but when I looked up in the mirror I was moving in slow motion...or obviously struggling (and with a quick glance around the room)-struggling more than most of the people in there. On Tuesday we were sitting on the big ball doing triceps. You know where you hold hand weights up above your head and then lower your arms back (bending at the elbow). Some people were using 2 weights, I was using one 9-lb weight and after just a few, I couldn't do it. Like, I'm not being a sissy...I really couldn't get my arms back up once I lowered them down to the back of my neck.
And then yesterday in my Interval class I had them (us) doing Frog Squats for 45 seconds. By about 30 seconds my legs were shaking so bad, I was so out of breath and dizzy that I had to stop. I felt like the ultimate hypocrite! Here I am telling THEM to do something I can't even do!?!?! But I knew if I didn't stop, I was going to trip because I was already losing my balance and getting crooked with my jumps.
Anyway, this whole phenomenon is just WEIRD. Why am I LOSING my stamina? I haven't let up on my intensity. I should be getting better and stronger every day...but I feel like I'm going backwards. Things I could easily do last year, I can not do now.
Anyone else ever go through this? It's really pretty frustrating.
Okay well...that's my "rant" for today! :) Hope you are all doing well and keeping up with your workouts through this holiday season! Love you!!