Yes, running is extremely inefficient. The most efficient form of movement known is a human on a bicycle. One's choice depends on whether the goal is to burn calories, or travel efficiently.
I've burned an estimated 5000kcal daily on the bike for weeks.
Wait a minute, what? You're going to take the most efficient form of locomotion and use that as an example of how to burn calories? The only reason you burned that many calories is because you spent all day on the bike. Maybe I'm completely missing your point, but for time spent, running burns more calories.
This is not correct. They are relatively close, though in fact swimming on average will burn slightly less calories than running per hour of activity for most paces of comparative effort [0].
> I've burned an estimated 5000kcal daily on the bike for weeks
This is around 3.5 to 10 hours of cycling a day depending on your weight and speed... There is individual variation of course, but there is no way you are burning this many calories without A LOT of hours on the bike.
"Each day participants ride, on average, about 100 miles and burn some 6,071 calories"
As a competitive, but still amateur cyclist I would do something in this ballpark almost every day. Hence 3000 - 5000 calories. And I'd often run for an hour or play soccer on top of this since I wasn't a pro.
I did spend a lot of hours on the bike, as serious athletes tend to do. Years of experience with myself and many other national caliber athletes tells me that we do in fact get sick from strenuous exercise, all the time.
This is a very bad baseline for an average athlete. You are referring to pro athletes in a race event who average 40-45km/hr speeds on a notoriously hilly race. They don't maintain this level of exertion during training season, and an average athlete is nowhere even close to it.
> As a competitive, but still amateur cyclist I would do something in this ballpark almost every day. Hence 3000 - 5000 calories.
If you bike 160km a day, then you're cycling 4 - 6 hours a day. My original statement that you're not burning that many calories without ALOT of hours on the bike is correct.
> I did spend a lot of hours on the bike, as serious athletes tend to do. Years of experience with myself and many other national caliber athletes..
It's very impressive if you're able to sustain >30hrs week of exercise for weeks as you mention, but be cautious to not sound elitist.
Put another way, an average cyclist will find a 2 hour bike ride to be an average ride but an average runner will consider a 2 hour run to be quite long.
A serious endurance cyclist or swimmer will certainly go through 3000 kcal on a normal training day if not more.
I've burned an estimated 5000kcal daily on the bike for weeks. What's more is I know these numbers are very accurate as we train with power meters that record our energy expenditure with minimal error.
It's important to distinguish between serious athletes and average people who exercise. It's possible that truly competitive athletes - for instance, who run 120 miles a week to your 30 - will be much more likely to get ill from their efforts. It can take serious fitness - and a mentality acquired only by years of serious training - to push yourself to the extent that you fall ill, and maybe the recreational "athlete" described in this text can't reach that point.