DArthurBrown

One of my friends here is getting his PhD in exercise science. We had a very similar discussion about this recently. When you run, there is a point in each stride where you are essentially keeping yourself from falling on your face. That short moment, where you are effectively and inevitably hitting the brakes, requires a very hard, sudden, muscle contraction. It's the reason running hurts more than cycling. It's the pounding sensation.

If you're comparing calories per mile, you burn more by running. If you're comparing calories per time, it depends on how fast you are. Suppose you run comfortably at 6 miles an hour--a standard marathon pace. Now suppose you bike comfortably at 18 mph. Assuming the 1/3 rule is reasonably accurate, the calories burned per hour are roughly the same. Now suppose you run 6 mph, but bike 20 mph. You get more by biking. Running 7 mph and biking 21 mph, you are again burning similar calories.

bajadock

D.A.B. , my experience is also the 3x to 4x ratio of running v. cycling caloric burn.

Interesting that the original poster's main exercise is running, but, reason for this post is losing weight.

One dimensional programs don't work for many. I like diverse exercise programs for mental stimulation.

Only reason I would choose bicycling for weight loss is if that was only exercise routine that I liked. It's very inefficient return on time investment compared with so many other choices. But, hey, I think this is a bike forum.

DArthurBrown

But the calories burned per unit time is similar. The one major benefit of cycling over running is that you can go much longer than running, because your knees, hips, ankles and spine aren't getting pounded into submission with every stride. So, if you could burn 500 calories per hour running or cycling, and you could bike for 3 hours or run for 1, cycling's the clear choice. Cycling also allows the scenery to change more rapidly...and in Oregon that's a neat incentive.

Menel

Consider it cross training, it really unwinds the legs sometimes. Both are incredibly enjoyable, I get my rush on the bike from the speed, the magnitude of scenery I pass, etc. Running I get my rush from the huge level of accomplishment from long runs, and from events, setting new PRs etc when I can. E.G. I have a couple of Ultra run events on my calendar if I can without injury better conquer the Marathon distance.

I hop on the bike 2 days per week, run 4 days. I don't maintain a calorie deficit every day (e.g. day before a 16+ mile run), it depends on what day of the week it is. But every cycling day I would like to be a deficit day if I can.

Sometimes I go rock climbing with friends, go to an Ashtanga class, but I can't really quantify those and not gonna try to.

hoody

according to my SRM I burnt 1400 calories (1400kj to be precise) on a two hour ride today in 2 hours of running I could run max 14 miles (approx 1400 Calories) and as no one can run a sub 2 hour marathon let alone 42 miles in 2 hours to make the ration 3 or 4 :1

Inertianinja

i would love to get an official response from Garmin on this issue.

when i do a 60+ mile ride my Edge 705 tells me i'm burning over 4,000 calories. ridiculous. why would they jack the formula up like that?

Menel

My original esimate wasn't quite so extreme.
I was never thinking or even proposing that drastic of a difference 1:3, 1:4 I agree is pretty crazy. 2:3... maybe, I was always thinking more of a 4:5, 5:6 ratio. In my example I used a 5:7 ratio cycling:running, maybe based on numbers you've collected on yourself, that seems more realistic?

The difference for you, I assume your primary sport is cycling?, you're likely more efficient, maybe you enjoy pushing yourself there more, have more goals while cycling, more motivation. So your perceived effort will likely be skewed slightly against running, the impact with it, etc? Thus you may move closer to a 1:1 ratio. Where conversely, mine is likely skewed against cycling, OMG quads burn! LOL!

Make sense? All hypothesis.

WCG

+1. It should also be said that for those of us that gave up running for cycling, the recovery time for cycling allows for a greater opportunity to ride these distances and longer every day with no negative effect on the body.

chadwick

Yesterday was an interesting data point from me on this. I had an hour recovery ride to do... 68 minutes total, with probably 8 minutes of that at stop-lights. I didn't stop pedaling otherwise, but it was very low intensity. Heart-rate based calculations say 608 calories for that ride; my kJ worked from my PowerTap say 485. I'm surprised it was that much even given the intensity.

Meanwhile, a low-intensity 45 minute run on Saturday was 585 calories from heart-rate based data.

I've had bike rides that were much, much more intense than my most intense run (but, I'm a slow runner, for now anyway).

One thing I've found I really like this year is using that WKO+ software since it calculates training stress scores for both running and biking. I now get a much better picture of what a true running intensity is rather than before... since I'm usually thinking 'ow this sucks' whenever I run, it's helpful feedback.

I've come to the conclusion that it's way to easy to go OCD on the calorie/kJ/whatever data and I stopped really thinking about it as much as possible.

merlinextraligh

Alan Lim had some calculations on Saris website. (unfortunately its not there anymore) Their lab testing found efficiency varied between 18-24% (IIRC)

The math worked out that if you use 1KJ = 1.1 dietary calories you'd be accurate +/ 5% for virtually all cyclists.

Gorden Gekko

As an ex runner I would have to say there is a lot more pain in cycling . Running is more abusive to the body but the burning sensation in your quads on a constant heavy climb...now that's pain.

merlinextraligh

One, they don't use HR data for the calculation, which makes it less accurate than it could be. (why they don't take advantage of the HR data would be a good question.)

Two, by its nature and all the asumptions it has to make its going to be inaccurate, so I imagine they program it extremely optimistically to make people happy instead of pessimistic and pissing people off.

aham23

^^^^ the 500 allegedly has a new formula that takes HR into account. later.

gregf83 

They probably took it off because it's not correct. Based on the scientific literature there is no way powertap estimated calories are within +/- 5% of actual. It may be the best estimate available but it's still an estimate that needs some calibration based on personal experience with weight loss/gain or an actual lab test.

gregf83 

One advantage of cycling vs running, if you have sufficient time, is that you can burn a lot of calories from fat that don't need replacing in order to train the next day. With running you're much more likely to deplete your glycogen stores and these will need to be replaced. But if you cycle for 3-4 hrs at a moderate pace it's much easier to maintain a substantial caloric deficit while still being able to train on consecutive days. This assumes your primary interest is in dropping weight vs getting faster.

merlinextraligh

It was based on Lim's results of Lab tests of a number of individuals. and the 18-23% efficiency in creating dietary calories to KJ at the hub is pretty consistent with other published results. Which translates to between 1.05 to 1.15 calories per KJ. Take the midrange and you get the +/- 5%

The original link is busted, but I found it quoted on another website:

From the Cyclops site: https://www.saris.com/CalorieCalculator.aspx

If I do 1000 Kjoules on a ride, can I calculate how many Kcals my body has burned?
One Kcal is equal to 4.186 Kjoules. Based on this conversion, if a rider does 1000 Kjoules on a ride the Kcal equivalent would be 239 Kcals (1000 Kjoules / 4.186). Remember, however, that the energy measured by the Power Tap in Kjoules only represents the mechanical energy delivered to the rear hub by the body, not the total energy expended by the body. If our bodies were 100% efficient then all of the metabolic energy produced by the body would be converted to mechanical work and a 1000 Kjoule ride would cost the body 239 Kcals. Unfortunately, we are not 100% efficient. On average a pedaling cyclist is only about 18 to 24% mechanically efficient. For every 100 Kcals our body burns, only about 18 to 24 Kcals actually goes into moving the bicycle. The other 76 to 82 Kcals gets wasted as heat or is used for the maintenance of other bodily functions. If we were to assume that a person was about 22% efficient, then to do a 1000 Kjoule ride, he would actually have to burn 1086 Kcals (239 / 22% or 0.22). Because 1 Kcal is about 4 Kjoules, and because only 1 Kcal out of every 4 Kcals burned by our body actually goes into moving the bicycle, 1 Kjoule of work performed on the bicycle is about equal to 1 Kcal burned by the body.
In the Applied Exercise Science Laboratory we actually measure mechanically efficiency and calculate personal conversion factors that allow athletes to convert mechanical Kjoules to metabolic Kcals. This conversion ranges from about 1.05 Kcals per Kjoule for the most efficient athletes to about 1.15 for our least efficient athletes. It’s important to note, that a number of factors like training status, temperature, and biomechanics may change a person’s efficiency. When it comes to calculating energy expenditure, however, the potential errors introduced by changes in an athlete’s efficiency are small compared to the potential errors that may occur when heart rate is used to calculate energy expenditure. While there is no perfect way to calculate the total Kcals used during a ride, measuring power output is currently our best estimate in real world conditions.



And while that particular link is no longer active, you can see a number of places on the web where Lim uses that 1.1calorie to KJ factor, but without the explanation of how its derived. And Dr Lim appears to know a fair amount about exercise physiology.

aham23

^^^^ dude is all over this. later.

echotraveler

no no, downhill and accelerating with the strongest 11x52

WCG

+1. And he must have some enormus Kjoules as well.

gregf83 

An 18 to 24% (your previous numbers) range in gross efficiency translates to a variation of +/- 15% if you take the mid point of 20.8%. (20.8/18 = 1.15).

You also need to be clear on whether you are talking about gross efficiency or delta efficiency. If you're using gross efficiency and you go on a 4 hr ride can't just add the number of calories estimated to your BMR (basal metabolic rate). You need to subtract out the 4 hrs of worth of BMR. Most people probably don't bother with this and end up overestimating how many calories they are expending in a day.

waterrockets 

True, and I've used that method in my own diet and successful weight loss. My point is that the precision is higher than the accuracy. If you burn 5% more kj on a ride, you've burned really really close to 5% more calories, but the +/-5% accuracy will still be the same.

+/-5% is fine and still plenty useful, but I just wanted to temper the previous power-meters-accurately-track-calorie-burn statement.

merlinextraligh

One, the 1.05 to 1.15 range is Lim's not mine. I'll take his word for it, given that a number of professional cyclists have paid a lot of money for his expertise.

Two, the point about BMR is a complete tangent, that has nothing to do with how you convert KJ's at the hub to dietary calories. While it's avalid point,its non responsive to the issue of how well a powertap measures calories expended.

Three, whether the "correct" factor for a given individual is 1.05, 1.1, 1.15, or you just assume 1 to 1 for simplicity, a power meter is going to give you the most accurate measurement possible outside a lab, and is certainly more accurate than Garmin, on line calculators or HRM calculations, and is certainly accurate enough for any reasonable use.

nadimk

There are simply no data available to generalize for you how many calories you will burn cycling. The "research" you are looking at is probably fairly close, but there are too many variables to consider. You could try to get a cycling test hooked up to a metabolic cart to measure oxygen consumption, etc., but this is not readily available to most people. There are some data that indicate the "interval" nature of cycling as compared to running enhances fitness a bit, but who knows. The number you know for sure is how many calories you are eating!! What you do is you ride, run, and adjust your food intake to induce weight loss. I think you will do alot for your health to add cycling to your exercise regimen.

merlinextraligh

I think you've got a point that you can overstate the mathematical precision of the power meter calculations, and even the Lim quote I posted admittedly gives some caveots.

The thing I rail against in the calorie threads is people who dismiss the powertap data because of the efficiency calculation, and then kid themselves that they are burning way more calories than they are because they aren't as efficient.

IMHO, 1.1 is mathematically supportable. Just a straight 1 to 1 is simple and conservatively safe.

nadimk

This is spot on in my professional opinion. I strongly urge all cyclists who ride for fitness and to lose weight to get rid of all cycle computers and power meters and heart rate monitors. These devices are complete hype for most of us. The most critical thing to track is how much time you spend riding the bike at a high rate of perceived exertion on a daily basis, how enjoyable your riding is, and how much weight you lose by reducing calories.