This is a technical cue that you hear quite often with athletes in Olympic Weightlifting. It is a great cue that can help quite a bit, but if it is not used properly and at the right time, it can mix up the lifter’s technique.
“Elbows up” is mostly used during the clean and jerk, and it is especially important for the clean part of that movement. When you catch the clean, the bar should be landing directly on your shoulders and collar bone so your whole body will absorb the weight. If you receive the bar with the elbows down, it is mostly your wrists, arms and shoulder that will absorb the load witch can cause injuries. The transfer of the weight on your shoulder and collar bone will most likely happen when you will actually lift your elbows up, and that is why we try as much as possible to catch the bar in that position.
Having the elbows up fast can also allow you to be in a better position to receive the bar. Having the elbows as high as possible when catching the bar will force you to keep your torso up right, witch will help you keep your balance once the load come back on you. If your elbows are down, you will most likely lean forward and with a heavy load being more in front of you instead of on you, and you might miss the clean.
Some people try to take advantage of the torso being more up right with the elbows up during the jerk as well, and that is when this cue gets misused. Have you ever tried to do a military press with your elbows pointing straight ahead? And if you compare that position with a military press with your elbow pointing down, or say on a 45 degree angle? Any difference?
Having the elbows down will put you in a way stronger position for the press part of the jerk. The ideal situation is to be able to have the bar resting on your shoulders and collarbone while elbows are at a 45 degree angle. You will have to control the dip of the jerk more, to make sure you will stay up right, but at least your arms and shoulders will be ready to help you out and make the jerk easier for you.
So all of this to say that using the cue “ Elbows up” to help for a clean or even a front squat is great, but it is not accurate to use that with the Jerk. It is way better to be able to adapt your position to be able to dip up right with your elbows angled. This position is not quite natural for most of us, but once you get it, your jerk will be way easier!