Box squats, chins, and presses

I recently discovered the glory of box squats, so I decided to try them out tonight. My warm-up:

QM up+down stairs x2
Reverse QM up+down stairs x2
2:00 jumping jacks
2:00 skip rope, double-unders every third swing

Work-out:
3x5 box squats (100lbs - 50lb vest+25lb dumbbells on each shoulder)
3 sets of chin-ups (7, 6, 5)
3x15 atomic sit-ups
3x12 overhead press (30lb dumbbells on each arm)

Cool-down:
2:00 Front plank
stretch
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The box squats were pretty tiring.. Everything was, actually, and the chins just got worse and worse. Doing chins for the first time in a long time also made me realise that my pecs and serratus anterior are REALLY tight, so I need to work on that.