Idk, I heard it is the energy output equivalent of running for 12 to 14 miles on average. I gotta say, dealing with other people made the birth process harder than anything. I remember irritation being the predominate feeling from my other births. Much more so than how bad it hurt or how exhausting it was. Being a rugby player kicked my ass into exhaustion more than child birth did. But I may have a higher than average threshold for pain. Or not being afraid makes it less painful. Whatever the case, shame I can’t wear a HRM for posterity so we would know if it is really harder than running 14 miles or is going to cost you a weeks of stored calories.