What is the most efficient way to ride up or down hills, and into or away from wind?

Question

I'm trying to work out how hard I should push myself when riding up or down a hill. Similarly, how hard should I push myself when riding into, or away from, or perpendicular to wind?

My aim is to arrive at a location in the shortest amount of time possible. I would assume that if I output more power going up a hill, then I would have to compensate by outputting less power going down the other side (let me know if you disagree). So, what is the most efficient way to achieve this aim? Is it better to work harder (and save time) up hills, or work harder (and save time) down hills. Similarly, how does wind affect this, both on the flat and concurrently? For the purposes of this question, assume I am riding by myself and hence ignore slipstreaming

Extra points for justification of your answer with links and/or physics. (N.B. there are no extra points.)

Answer 1

Basically whatever works.

If you're trying to conserve energy it's foolish to push yourself going downhill, since energy lost per mile to wind resistance increases with the square of speed -- just take advantage of the "free ride" on a reasonably steep hill.

Going uphill depends a lot on your physical condition and how steep the hill. You first need to ration your short-term energy availability so you don't run out of steam halfway up. Beyond that, though, there is a complex relationship between cadence and muscle efficiency, and the "sweet spot" in terms of force vs cadence is highly individualized, and also depends on the length of the hill.

On the flat it's a little clearer that maintaining a moderately high cadence is optimal in terms of preserving stamina, though "moderately high" again varies with the individual.

Running into the wind it's generally better to slow down, again because the higher your relative wind speed the more energy you "waste" per mile.

Running with the wind you can take advantage of it, of course. (But we all know that a tailwind is a fiction -- it never happens in real life.)

Whatever works.

Answer 2

As you have guessed, it is better to work harder on the uphill and rest on the downhill. And as others have mentioned, whatever works for you on the uphill in terms of balancing high cadence and mashing is best. However, there are a few guidelines that you can follow to approach each situation in the most efficient manner possible.

1. Downhill: Since wind resistance is the biggest factor in reducing your speed in this situation, you simply want to be as aerodynamic as possible. Tuck yourself into an aero position. Basically, you want your upper body as low and horizontal as possible. Check out pro riders on the downhill of a mountain for visual aids. Use this opportunity to rest and only pedal in short bursts coming out of corners that you've had to brake for.

2. Headwind: You want to maintain a somewhat aero position, so keep low. However, a complete aero tuck compresses your lungs in your abdomen and you can't breathe as fully as if you were sitting straight up. This means you'll need to find a balance between aerodynamics and being able to breathe efficiently while keeping up a constant cadence and pedal force. You'll also want to keep your arms farther apart because tucking them into the center also compresses your lungs within your chest. Most likely, you'll want to either be in your drops or hunched over a bit with your hands on the hoods.

3. Uphill and/or tailwind: You can pretty much treat these two the same way since wind resistance is less of a concern than your own aerobic fitness. Just sit up and keep your hands wide to keep your lungs as open as possible and pedal with whatever force and cadence works best for you. Studies confirm our everyday experience that standing while you pedal will increase your speed but is not sustainable for very long. You'll only want to stand up to maintain speed over short sections where the road rises steeply (or more steeply if you're already on a hill), when a brief gust of wind has slowed you down and then let up, or any other situation that briefly threatens to lower your otherwise sustainable speed. If you're running out of energy and only halfway up a hill, standing up won't help you.

Of course, in the real world you never have just a hill or just wind from the front or back. There are cross winds, cross-head winds, cross-tail winds, hills with wind from any direction, and everything in between. Add in traffic concerns, road conditions, etc., and you'll almost certainly have to find a balance between pedaling efficiency and dealing with the world around you.

If you'd like to read more, there is a great article on cycling up and down hills: http://www.sportsci.org/jour/9804/dps.html.

And the ever helpful sheldonbrown.com has an qually excellent article on the effects of wind resistantce here: http://sheldonbrown.com/brandt/wind.html.

Answer 3

The only thing that will work for everyone in all situations is to wear a heart rate monitor and ride right at your aerobic threshold. Otherwise, it will be mostly personal preference, for loose meanings of "shortest amount of time possible".

Answer 4

IF my hills are in the 4% or greater category, it is always going to take me longer to get up than to come back down. Example, a hill I ride frequently is about 4 - 5% and I ride it at about 7-8 mph and it takes me ~7 minutes to get up there. If I ride back down the same hill, I easily maintain 23-24 MPH and it takes me about 3-4 minutes to get down. If I work harder at coming down, I save maybe a minute at most. But if I could ride up at 10 mph, I'd get up the hill about 2-3 minutes faster. Unfortunately the limiting factor for me is my aerobic and physical ability. As I get in better shape and loose more weight, I'll go up faster. Two days ago, we had 15 mph winds gusting to 34 mph. Those winds were blowing up hill, I could not believe how fast I went up the hill, averaging about 11 - 13 MPH all the way up. Coming down, I had to WORK to stay above 15 mph. So the wind gave me an approximate 30% advantage going up and cost about 50% coming back down. Maybe someday I'll be able to ride up that hill like I had that tail wind, until then, I'll huff and puff my way to the top! I think hills make the man. (or woman).

Answer 5

I guess you may be working on the assumption that you have a total amount of energy for your ride and you choose which parts of the ride to use it on, or when to use it most quickly. Perhaps you suspect that, due to the lower wind resistance, you're better off spending more energy going uphill at the cost of needing to relax on the downhill?

Consider the simplest case of going up a hill and back down the same way, with no true wind (only what you induce by moving). My thinking used to be that I should go as hard as I possibly could up the hill, so that I had to coast down the other side. When climbing, I thought, very little of my effort would be lost to wind resistance. I'd be slower on the descent, but this would mean a smaller proportion of my work would be spent on overcoming (induced) wind resistance. I've read that at 20kph you are using 50% of your effort to overcome wind resistance and, as pointed out by Daniel R Hicks, wind resistance increases with the square of speed, so this strategy seems intuitively sensible.

However, my experience doesn't bear it out. I think the problem is pacing. I can't actually work hard enough on the climb to make this work. If I pedal flat out, then I need more than the same distance downhill to recover for the next hill or to keep me going on the flat. But working at, say, 40-80% of maximum is more sustainable for anything longer than a ten minute up and down. Extreme effort actually costs more than slightly above-average effort. (Also see a question about standing up to pedal).

Lately I've been concentrating more on my target average speed. Any time I'm below it I work a little harder and when I'm over my target I relax a bit. I don't have a heart rate monitor or power meter, but these might help too.

I'm afraid I don't know all the equations, but I think they'd have to take into account aspects of your body's performance, not just power and aerodynamics, so would be pretty complicated.

For me, working out through practice the best times to put the effort in on a 1-hour route is part of the fun of racing against my previous times.

Answer 6

It depends on the hills and your fitness. Assuming that your fitness is excellent and the hills mild, you would want to put out constant effort at your maximum that you could sustain without tiring out. You would maintain constant cadence and torque by shifting gears up and down as needed.

On the other hand, If the hill is steep and long relative to your fitness level you may have to work harder. In that case you may need to reduce effort or even coast down the hill to recover.