This is the IGX challenge, that is where I got it.
When I did it last, was cruising along with doubles every 30 seconds, then switched to doubles every minute. At rep 58, felt a little something in my back, so I just stopped at 60. I believe that was at the 20-minute mark.
Lately, just screwing around with all kinds of ways. The dropping after each rep just sucks, cuz you can't get them in fast enough.
Starting with 4 sets of 5 on the minute is fun, then swtiching to doubles on the 30-second is nice for training. I don't go over 40 reps.
My goal is to get 61, but I'm not going to predict. Yesterday's training with 40 was a joke. Felt easy. When I actually do the challenge, going to have s pit crew to count, call out the time and slap the plates back tight.