AMRAP 4×4, with 4 min rest between each
1) 400m Buy-In, then max DUs
2) 400m Buy-In, then max Burpee Target
3) 400m Buy-In, then max Wall Balls
4) 400m Buy-In, then max Cal Row
Intended Stimulus: this is interval work. Interval work is effective because of the rapid increase/decrease fluctuations in heart rate. You should aim for a true maximum effort in each of the work intervals. The rest intervals should be long enough for your heart rate to decrease significantly. Work at a fast pace as if the immediate four minute work interval is the only focus of the workout, and without regard for previous or subsequent work intervals.