raceboy

I've been wondering this since I've started cycling seriously. At first blush, it seems that the obvious answer is that hill climbs require more energy. But do they really when you figure that over the course of most rides, there is a downhill glide to compensate for every uphill.

Are there any research studies on this?

Thanks!

10 Wheels

Hills and Wind take energy.

gregf83 

Personally, if you go by distance, hills take more energy than riding on the flats. But if you consider time then flats can be just as hard.

Two examples from rides in the past month:

Flatish ride (684m elev) 122km 3072kj avg pwr 228W TSS 285 Ride time: 3:44
Hilly ride (2650m elev) 122km 3455kj avg pwr 192W TSS 318 Ride time: 4:59

TSS is an indication of overall training stress. So for me the hilly ride was more stressful but it was also over an hour longer. Average and normalized power was less for the hilly ride but time was considerably longer.

In the end I don't think there's an obvious answer. I ended up taking longer on the hilly ride partially because it was a new route for me with a few excursions on gravel trails so I wasn't riding as steadily. It's harder to loaf along on a hilly ride but I can make a flat ride as difficult as a hilly ride.

Rollfast

When I saw this I of COURSE thought flats, you are going to walk it. Wrong flats.

DrIsotope

Shorter

Flat
39.2 miles
2.01.46 ride time
853ft elevation
1,815kj total work
258w avg pwr
Training Load 135

Hilly(ish)
31.9 miles
1.55.04 ride time
1,837ft elevation
1,530kj total work
255w avg pwr
Training Load 134

Longer

Flat(ish)
66.6 miles
3.47.12 ride time
2,277ft elevation
2,989kj total work
231w avg pwr
Training Load 213

Hilly(ish)
65.1 miles
3.51.06 ride time
3,894 ft elevation
3,130kj total work
245w avg pwr
Training Load 239

Downright Hilly**
50.1 miles
3.27.12 ride time
5,279ft elevation
2,701kj total work
232w avg pwr
Training Load 200

Armchair analysis

My initial thought would have been, "Oh, hills are obviously harder, I must burn more." But that's good old Perceived Level of Effort rearing it's head. Seems harder, must be harder. It's just slower is all. Just for giggles, according to the Strava Calorie Guesstimator® the 66 mile compared to the 65 burned just 4% less calories.

Hills. Who needs 'em?

**As someone mentioned above, big hills have big descents, and my 50 miler is definitely an example of that. 5,000 of the 5,300 ft came in the first 21 miles. So naturally, the average power drops along with the training load, even though that ride felt the toughest of the three.

Looigi

It's the power output that burns energy. Put out the same power on a flat or a hill, into the wind or even with a tailwind and you'll burn the same energy in the same amount of time.

Most people work harder on hills or into the wind so burn more energy, but if you work equally hard, you'll burn equal amounts of energy.

Works on trainers too.

markjenn

The physics dictate that for equal power output, you're going to go faster on a flat course. Or, to look at it another way, for equal overall time, you're going to have to work harder on a hilly course because you spend much more time climbing than descending which either lowers your average speed or requires more power output for the same average speed.

Taking things to a bit of an extreme easily demonstrates this. Say you're cycling a 15-mile dead flat course where for your normal power output, you would travel at 15 mph. You'd complete the course in 1 hour. Now let's change the course such that there is a steep 3-mile hill on the course that, with the same power output, you could only do 3 mph. You'd spend a whole hour just climbing this hill, so you'd have to complete the other 12-miles instantaneously to do the course in an hour. Obviously this is not possible.

The same thing happens with winds - you never gain as much with a tailwind as you lose with the headwind. Say that you're doing the a 30-mile round trip with a 5-mph headwind in one direction and a 5-mph tailwind in the other. In the headwind direction, your speed would be 10 mph and you'd take 1.5 hours. In the tailwind direction, your speed would be 20 mph and you'd take .75 hours. Total time would be 2.25 hours which is 15 minutes longer than with no wind.

- Mark

Jseis 

Though I've no watt meter, this burns an insane amount of energy. 15 mph winds make it harder.

sprince

Hills, and more so the heavier you are. There is a momentum disadvantage uphill, and any momentum advantage downhill is more than offset by the added wind resistance of higher speeds. Take away wind, rolling resistance and add in a 70/39 chain ring combo and it should almost even out.

CliffordK

In a sense, it is all about watts. Crank out 300W on the level, against wind, with wind, whatever.... or crank out 300W going up hills... and the results will be the same.

I have a lot of troubles keeping up high power on flat land. So, the hills become a big motivator. Yes, downhills can be a bit of a recovery period. But I went on a hilly ride recently, and there wasn't enough time to recover between hills. So, as the day wore on, I just got wore out. I had my gearing so I could do a mile or so at 10%. But hitting 10% after 10%, and a few stretches peaking over 20 or 25% just put me over the top.

According to Strava, my calories burnt was greater during the flatish rides that week, just because I went further/longer. And Strava didn't calculate the flat rides included a large backpack.

Anyway, so burning energy is watts x time.

Hill climbs may give a greater workout only if one pushes out more watts going up them.

DrIsotope

So then,

Flats may give a greater workout only if one pushes out more watts going on them.

Hills have a higher perceived level of effort... as I said earlier. But 300w on the flat or 300w going up a hill, it's the same thing-- just one is generally faster than the other.

I do though enjoy when folks talk of 20-25% grades, because I've never seen one in my life. That's like riding up a typical staircase. Hiking trails seldom maintain 20%. Even 10% is over 500ft per mile, and the steepest roads into my nearby mountains don't get to 10% for more than a a few hundred yards at a time.

But that's all moot anyway. 300w on 20% and 300w on 0% are the same effort.

caloso

This. /thread

CliffordK

Don't forget that is percent and is not degrees.

But, now that you mention it. That hill was wicked steep, and I didn't have low enough gearing to make it up the hill without stopping, although I rode most of it in short bursts, walking would have been faster. Next time I'll have better gearing.

https://www.strava.com/segments/3884813
https://www.strava.com/segments/645083 (same as above, but straight path up the hill, and easier to read the slope).

I have heard that there are a few steep roads around the San Francisco area. Perhaps it is time for a Road Trip.
The Real Top 10 List of Steepest Streets in San Francisco | 7x7

But, even LA isn't without its share of steep hills.
https://www.strava.com/segments/643550
LA Has the Most Ridiculously Steep Streets of Any US City - Curbed LA
The 10 Steepest Streets In America

Yeah, most are short. But, it is still extremely intense. Brynwood is listed at 0.3 miles, so long enough that it can definitely be felt. I'm not sure I'd want to ride down it... I'm not that fearless anymore, but there was a nice loop you could do intervals on if you wish.

unterhausen

There is a hill in the Delaware Water Gap park that always makes me feel like an idiot. That is the hill that made me realize I could either try to eat more, or use lower gears. The way I ride a bike, I would never have that much expended energy on the flats. It really is about power output, but I find it difficult to put out that much power on the flats. That's why a lot of people do intervals on hills, it's just easier to put out more power.

20% seems to be about the steepest that people build roads out in the country where they can pick their route. There are plenty of those in Pennsylvania, not amusing. 2-300 feet at that slope is no joke. There is one road we ride on occasionally that has a 18% grade for 2 miles.

sprince

I have a 25% section of road in my subdivision. It's not all that uncommon.

300w on 20% and 300w on 0% may be the same effort, but that wasn't the question (more specifically 300w in your example is the effort). You will cover a much greater distance in the same amount of time on %0 vs. 20% (half +20% and half -20%).

Rollfast

I think pedaling is better than not, go further.

DrIsotope

They don't exist out west. We have codes for road construction here, and residential, state/county maintained roads do not exceed an average gain of 12% per mile. Highways do not exceed 7%.

That was exactly the question. And the PM doesn't know if you're going up a hill or not.

raceboy

This makes the most sense to me for my original question. I think my body has a certain wattage that it perceives as ideal and calibrates to that roughly. It does seem that if I calculate about 40 calories per mile regardless of the hilliness or flatness of the route that the total number of calories burned comes out pretty close to what Strava says. I know Strava is not the ultimate calculator for these things but it's what I've got.

Seattle Forrest

The steepest paved road in Seattle is 26.2 % according to our DOT. I've done it. Once. Pavement that steep is pretty rare.

DrIsotope

I guess I look at hills the same way Strava does-- for these +20% grades to even get categorized, they would have be in excess of 1000 feet in length, and that just doesn't appear to happen. A 20-25% for 200-300 feet is tough, but it's just a bump. Even at a walking pace, it's less than two minutes to get up it. 6-8% for two hours is really tough.

Still doesn't burn more energy, though.

Seattle Forrest

Our 26.2 % grade is for one block. The surrounding blocks are only 25 %.

CliffordK

I don't ride super-low gearing. So, anything over about 15% packs a pretty good punch, even if it is short. It can be like an all-out sprint.

As far as steep hills. SF & LA apparently have their share, but most of the steep sections are quite short. Not that pushing one to one's limit and beyond even on a short hill doesn't hurt.

The Hill rides I hit in Portland were pretty extraordinary. Most of the climbs were short, but one following another, there never was enough time to catch one's breath before the next hill hit. How did anybody ever find so many 10% plus climbs?

The first day, De Ronde was mainly in old construction, and had the steepest hill, I think, Brynwood which is about 0.3 miles long and receives a Strava Cat 4 rating. I'd put it higher just because of the sheer intensity of the climb even if only 0.3 miles.

The second day, La Doyenne was predominantly in new construction areas. Nothing quite like the Brynwood climb the day before. However, there were a lot of 10+% climbs, and a few that hit over 15%. So, somehow in the last 30 years or so they've been able to build new streets that are quite steep.

A bikepath hit about a 20% slope for a short segment. I still can't believe it was actually intended for bicycles to be riding on it.

Richard Cranium

Your questions are easily misinterpreted, I think I might know what you meant to ask in spite of your phrasing.

The amount of energy you are able to "burn" is a function of the combination of intensities of muscle recruitment during a bout of exercise.

This means, in theory, we all have specific "best pace" or "best resistance" modalities to achieve maximum metabolic expenditures.

Exercise physiology is the study of how humans can choose to invoke differing methods of exercise to maximize metabolic expenditure while keeping focus on efficient use of these systems to perform "measured" work.

In conclusion, what I've written - simply means - each one of us has a specific work out intensity and length to consume our metabolic stores and maximize our human performance. These things change all the time due to rest and other training adaptations.

Successful athletes are the ones who have found the optimal ratio of anaerobic and aerobic system utilization to perform well.

mnsam

Even with an equal amount of up vs down you will spend more time on the uphill portion since you're speed is slower going up so energy consumed will be much greater riding hills. It may take 5 mins to ride up a hill that you can ride down in 1 minute.

DrIsotope

This is conflating perceived level of effort with umm... actual effort. These two examples are the exact same thing:

5 minutes @ 250W up a 6% grade
5 minutes @ 250W on a 0% grade

The difference is purely perception, because the first will get you about 7mph, and the second more than triple that. But the actual energy burn is the same. Math.

Hills seem harder because we tend to go at them harder. But attack a hill while staring at the PM data, and try to keep it spot on a number, like 200W or 250W. Next thing you know, you're at the top. I can burn more energy going downhill, just by maintaining a certain power output. The grade has absolutely nothing to do with it. The PM can't tell if it's uphill, downhill, or flat. It just measures work. And watts are watts.