Originally Posted by
Ranger Dan
I'd tend to agree with MetalPedaler on this one, but only on the basis of the experienced athlete being more efficient than the inexperienced rider. The difference in energy expenditure with experience is more pronounced in some activities than it is in others. For instance, not being much of a swimmer, I'm sure that I use much more energy to move through the water than my wife, the ex-life guard. I doubt the difference is as pronounced for cyclists, but I think there is some difference.
Yes, I'll buy that, but we're now talking about a different thing. The experienced and skilled cyclist will possibly have a more efficient pedal stroke. That may mean it takes her slightly less power, and therefore a few less calories, to achieve the same result. But in that case the power/calorie savings are the result of technique, not of increased fitness. When the fit athlete puts out 200w they are burning the same number of calories as the unfit athlete who puts out 200 watts, give or take individual variations in metabolism. I admit I'd be very interested in a physiologist's opinion about whether an individual's metabolic efficiency varies with aerobic fitness. If it does, you and metalpedaller may have a point. But it may go in the other direction. That is, the active, muscular individual may burn more calories at rest and therefore negate any reduction in consumption through increased efficiency during exercise.*
Originally Posted by
Jim Kukula
One funny thing to think about when considering the conversion of food energy to mechanical energy. Holding up some weight, just standing still holding weights in one's hands - pick your favorite position, arms down or straight out in front, whatever. No mechanical work is being done at all. But surely there are muscles contracting and glucose molecules getting metabolized.
Maybe less than you imagine. The most relaxed position you can adopt while on your feet in the "guardsman's posture" - feet slightly apart,, back straight, chest out, head balanced and looking straight ahead, arms by your sides. You're then taking maximum advantage of your skeletal structure, with the muscles having to do very little to support your weight. And in any event, the vast majority of our food energy is consumed not by movement, but to maintain our body temperature. Being warm-blooded has many advantages, but the price we pay is that we have to eat far more than would be needed just to repair ourselves and move around. Reptiles get by on tiny amounts of food relative to their bodyweight, because they rely on the sun to warm them up. They're not too quick in cold weather, of course....
This sort of thing can happen, surely happens, when pedaling a bike. For example, how much downward pressure is kept on the pedal as it reaches bottom dead center? That is muscular work that performs no mechanical work.
But if you are fortunate enough to have two legs, then a correct pedaling technique will limit the damage to close to zero, because as you reach the bottom of the pedal stroke with one leg, the other leg will be pushing through the top of the stroke to take over. When one "pulls up" on the upstroke one is actually exerting rather minor force, but the sensation of pulling up means that one is aggressively unweighting that pedal, and making sure that the leg pushing the pedal down does not have to overcome any resistance imposed by the weight of your other leg on the other pedal. So if you are doing it right, the small amount of mechnical energy expended on the upstroke isn't a waste, it is maximising the extent to which power exerted by the other leg goes into actually propelling the bike forward.