Is there much difference in energy expenditure between cycling with a really easy gear combo, or a really stiff one? (i.e. with an easy gear selection your legs have to pedal many more revolutions than with a stiff selection, to achieve the same distance, even though they’re obviously working harder with stiffer gears)
If you look just at the physics, then it will take a fixed amount of energy to move you from point A to point B in time T, no matter what gear you use. But if you look at the biology, there seems to be a certain pedalling cadence that works best for most cyclists. Lots of studies have been done and most recommend a pedaling cadence of 80-90 RPM. So choose a gear that lets you spin at 80 rpm at the desired level of effort, and this will determine your optimal speed.
Being a former road racing cyclist of some degree of success (I was an Australian National Team member back in the amateur days) I’d like to have a stab at this question.
I still average 300km per week in general fitness riding but I haven’t raced for 12 years now. Nonetheless, I’ve maintained very good speed and fitness - which I choose to do as a means of trying to stay as lean as a 41 year old man could reasonably attempt to do so.
There are some aspects involved - not the least of which is wind resistance and biological horsepower. Any way you look at it - to sit on 40+kph for an hour or two is gonna burn up a lot of calories due to the work output involved. I’ve found over the years that 90rpm is the LOWER limit of my own pedalling style - and bear in mind I’m 6’1" with pretty long legs - and they’re muscular legs too. Still, I’ve found that I personally sit on about 110rpm on a typical training ride.
My fave gearing is usually a 42-15 or a 42-14 into a slight headwind, and a 53-18 or 53-17 with a slight tailwind. I spin both of those gearings at about 36 and 42kph respectively. If I was still racing, those levels would be higher across the board - such is the nature of racing to raise the overall horsepower capacity of the human body.
If I wanted, I could push bigger gears, but then I find I’m starting to dip into my “anaerobic” strength - which is basically the innate strength that body builders kinda tap into. A 100m sprinter is all about “anaerobic” strength too. But it doesn’t last. You soon go into oxygen debt and your heart rate goes through the roof.
The trick is to maintain the highest possible “aerobic” output without tapping into “anaerobic” reserves. Your top flight pro cyclists deliberately train themselves to be able to spin at 110rpm or higher for every condition, and for every gradient. Lance Armstrong tends to sit on almost 120rpm - which is positively freakish. But the advantage for Lance is that he’s always in his “lung power” zone, which allows his body to recover quite miraculously overnight.
The fitter you get, the bigger your muscles get (as well as your veins too). The bigger your muscles get, the bigger the gear that you can still spin. The odd thing though is that good cycling technique is akin to being able to do 3000 push ups in one sitting. Obviously, by the time you’ve developed enough to do 500 push ups, to then go on and do 3000 is kinda academic.
But it takes many, many years to get to that level. Indeed, in my case, I’ve been a competitive cyclist since I was 15 so my own particular biology first started adapting itself an awful long time ago.
In short, spin, spin, spin my friend. And get yourself good pedals, and cycling shoes. Good pedalling technique is a true 270 degree motion for each leg with a dead zone approaching top dead centre. It can’t be achieved with only sand shoes. You gotta have the right shoes and cleats to get the most out of cycling as a fitness regime. And get your bike setup correctly too. The right saddle height (regardless of bike design) is critical to optimum efficiency.
Arrgh, I can’t find my copy of Whitt and Wilson (Bicycling Science) - I’m pretty sure it had a graph of pedal cadence vs. power output. IIRC it was consistent with Boo Boo Foo’s numbers, maximum power output occured somewhere around 80-120 rpm. Maximum efficiency occured at a somewhat lower RPM, around 60-80 RPM I believe. That is, if you go from 60 to 90 RPM, you might get 20% more power but burn 30% more calories. (These last numbers are WAG)
My own experience is consistent too. A couple of weeks ago I tried a well known hill climb route (10% average grade for 2.5 miles, 18% max). On my first try I had a 26t chainring and 11-27 cassette which forced me to drop down to 55 rpm, and it took 35 minutes. The next week I put a 24t chainring and 11-32 cassette which allowed me to maintain 80 rpm almost all the way. I did the hill in 25 minutes. I’d put even lower gears but that’d require a substantial modification to my bike.
But there is an even more important reason for maintaining high cadence: knee stress. Power is force times speed, so if you apply 100 lb of force on the pedal at 50 rpm, it’s the same power output as applying 50 lb force at 100 rpm. But you are applying half as much stress on your knees! For a given power output, faster you spin the less stress on your knees.
Thanks! BBF - that was really informative. scr4 too!
However- remember that the optimal RPM varies by rider. This year’s Tour de France is a key example. Jan Ullrich is the protypical gear masher who rides a larger and pedals at a slower cadance. He managed to pull in second overall (and came real close to winning). Lance used a sewing machine cadence and won.
There is no 100% right answer- only what suits you best. I tend to push a bigger gear myself but that’s what works for me.
Note that for a racer, maximum efficiency (max power per calorie) isn’t the goal. They really want maximum sustainable speed (sustainable over a full day of riding).
Generally, energy is not the limiting factor in the Tour de France-- it’s quite possible to eat and digest enough calories each day to ride 100 miles, even if your’re not riding at peak efficiency. So riders are happy to trade efficiency for speed.
The limiting factor is how fast you can ride (i.e. max power) without going anaerobic, as Boo said. Because if you go anaerobic, your muscles are going to want to recover before the end of the day, and you’ll slow way down.
It turns out max power without going anaerbic for most people is at the 90-110 cadence, which is higher cadence than max efficiency.