I'm a crossfit newbie and some colleagues from the gym and I agree that the most painful part (and the most breathe exhausting) is getting up from a burpee, that is, passing from the plank position to squat. What is the scientific reason behind this? Shouldn't the push-up part be harder to perform? Is there any way to focus on the getting up part? I can do 20 push-ups in a raw with too much of an effort but after only 10 burpees I'm already out of breathe. Thank you!
From a physiological standpoint, going from the plank to the squat requires you to hold a significant amount of bodyweight over your shoulders, and is bringing your abdomen into a compressed position that can naturally drive your wind out of you. Compare that to the pushup, which has the weight distributed between your hands and feet, or the moving to plank, where you're uncompressing your torso. Add to that many people lack the flexibility to be able to easy bring their feet up to their hands without lifting it, and you've basically added the need to be able to push yourself up enough off the ground to land in the squat, unlike the pushing out, where you can kind of more fall backwards.
The best way to practice the movement is to isolate it. If you need to make it a bit easier at first, elevate your hands a bit using a bench or a platform. Mountain-climbers may also help a bit for improving your flexibility and getting used to your diaphragm being compressed in the movement.
Getting up is harder than the push-up because work, by the physics definition, is "the product of force and displacement". In other words, you are moving more weight over a greater distance when getting up than you are when doing the push-up. It would take any machine (human or otherwise) more energy to stand up than to do a push up.
Burpees are exhausting, that is the exact reason to do them. Do not listen to those who tell you not to do hard things because they are hard. When you do hard things, you get stronger and they become easier. That is why you joined a crossfit gym. Stick with it, (do more burpees on your own time!) and you will look back in 6 months and be amazed by your improvement.
I have been doing crossfit for 10 years (32-42). Although I was very athletic before, and even played competitive high school and college sports, I am stronger and fitter than I have ever been, and I continue to improve in my 40s. I would easily beat my 18 year old self in anything.
Just something to think about: Burpees are a controversial movement. They are, as you mention, very hard, and they are also very hard on your body. Many people don't believe the payoffs of the exercise justify the cost. At 1:24 in this interview the spine expert Stuart McGill discusses burpees. He points out that the movement does not mimic anything in athletics. Another problem with burpees is that, in practice, nobody does them well. Go to the gym and observe people doing their burpees; you will see terrible form. For example, people fail to stand all the way up between repetitions (because they get lazy), and as a result they are training their body to slouch. Burpees might be good for 14 year old girls with their supple spines, but as we get older they become less appropriate.
@Claudix The fact that you have gone to the effort of writing to this board with your concern tells me something clearly: Your body does not like Burpees. Specifically, it does not like the part passing from the plank position to squat. This is a warning sign. Will you listen to your body before you get hurt? I gather from your question that you are doing Cross Fit. If you are, then I would recommend the following: Suppose the group is doing forty Burpees. I recommend that you do forty air squat leaps in the time they do twenty Burpees. Then go down to the floor and do forty pushup in the time they do the next twenty Burpees. You finish the exercise with everybody else, but you avoid that leap from plank to squat. Problem solved. The question is, do you have the courage to be different from the group? Can you do what is right for you body instead of following the herd? Let me know how it goes.