Just trying to keep up

Interesting story. 2 weeks ago I was out of town for work, M-Th. So I was going to be a good guy and keep up with exercising. I brought my jump rope! The morning routine was jump for 3x 90s, 15 GS w/35lb dumbbell and 10 pushups. End it all with a 60s plank. I did this for 2 of the 3 mornings I was there. An accomplishment in itself! As fate would have it, on the last morning, I left the jump rope at the workout center. I realized it when I unpacked. I got another one and I was reading the recommendations on the back. 12 minutes, 5x a week, burn 650 calories. Hmm.. 12 minutes of continuous jump roping! I can barely do a minute and a half. I can’t imagine 12 minutes! 650 calories for 60 minutes it only 10.8 cal/min. Secondly, I get emails from the kettlebell blog and today’s was titled, 7 fun and whimsical kettlebell workouts. It was not the Kb weight or reps, but this statement, 15 minutes on the clock and accumulate as many quality rounds as you can. 15 minutes! I know from kb class, that after 8 stations of ~30 seconds (~6 min), my heart is going to pop out of my chest. And I am not using 24s. 20s, & 14s with a 32 for DLs. Am I just that completely out of shape? Is it the extra 40lbs? My last class was a technique/strength class. 532 cal / 50 min. 10.6 cal/min. HR max 158 (94%), 132 (78%) avg. Still sweating an hour later. But good news, my back didn’t cramp up! Barb kept on the lighter bells specifically to help with the back. A nice blood blister under my callous too.