From the CrossFit Open season 2012, 12.3 is a time-priority workout:
AMRAP (As Many Reps As Possible) in 18 minutes:
15 Box jumps 24″/20″ box
12 Push press 52/35kg
Do these unbroken, in a steady pace that you are able to increase in the last few minutes.
Jumping fast early on is pointless and will disrupt the other movements to soon. Mobilis rule: jump up and step down.
Break these up early, 12 reps are deceptively difficult, and so is the weight.
If you are not able to move this weight for 6 reps unbroken, scale it down. A good rep scheme could be 6-6 or 7-5.
Official rules state: A shoulder press, push press, push jerk or split jerk may be used, as long as the elbow, shoulder, hips and knees fully extend, and the bar finishes directly over the heels with the feet together. Each round, the barbell must begin on the ground. Using a rack is not permitted.
You just moved a barbell around for 12 reps, so shake your arms out before jumping on the bar and get your breathing under control. Aim for unbroken reps on this one.
Tape up your hands or use grips. Don’t use excessive chalk, this will make your hands rip faster.
To Rx or not Rx?
It all comes down to the push press, you can either handle the weight, or you can’t. Remember, it’s 18 minutes, an eternity in CrossFit.
When done Rx, most of us will get to 5-6 rounds. But if you are superhuman, you’ll end up in the 13+ range: