Power and Weight

When riding a bike uphill or running you are working to overcome gravity. For the bike I’m sure that’s obvious. Riding up a hill means that gravity is trying to pull you back down. That’s what makes climbing on a bike so challenging. Running probably doesn’t seem as difficult because when running there is only a little bit of vertical movement occurring with each stride. While it’s not great it’s happening about 170 times per minute. That’s a lot of times. If the vertical displacement with each stride is only one inch (many age group runners bounce up and down much more than an inch with each step) that means you are lifting your body’s center of gravity 170 inches – 14 feet (425cm) – every minute. If running for an hour you’ve produced 283 yards (257m) of vertical displacement. That’s an 85-story skyscraper you’ve climbed. Huge!

Now imagine that you are riding your bike up a steep hill or running along a flat road as usual, only this time you’re wearing a backpack filled with 10 pounds (4.5kg) of rocks. It’s obviously far more difficult when wearing the backpack. But why is that? It’s because as the mass of an object (you, your equipment and the backpack with rocks) increases, the pull of gravity also increases. That’s why you have bathroom scales – to measure the pull of gravity on your body. We refer to that as your weight. So increases in weight result in your having to use more energy to lift it while riding uphill or running. Notice that there was no change in your power when you put on the weighted backpack; only a change in weight.

Now imagine the opposite. You’ve got a new bike that weighs 10 pounds less than your old clunker. It’s easier to ride up the hill, isn’t it? Or imagine that you’ve been losing excess body fat and your bathroom scales now say you are 10 pounds lighter. What will happen to your running? You’ll run faster at the same energy rate. Again, no change in power; only a change in weight.

Every extra pound (450g) added to your body and equipment “costs” you about one-and-a-half watts of power on a steep hill climb on your bike and about two seconds per mile when running. A few extra pounds one way or the other directly impacts how fast your race times are.

There’s no doubt that what your body and equipment combined weigh has a lot to do with how well you perform in triathlon. If we can reduce your weight without changing your power you will go faster. Or, conversely, if we can increase your muscular power with weight remaining the same you will also go faster. The best combination is to increase power and reduce weight. Much faster!

Here’s a simple guide for determining what your body weight means to performance. Divide your weight in pounds (kilograms) by your height in inches (centimeters). The typical, high-performance, male triathlete is in the range of 2.1 to 2.3 pounds per inch (0.38-0.41 kg/cm) with high-performance female triathletes generally being 1.9 to 2.1 pounds per inch (0.34-0.38 kg/cm). In road racing the best male climbers are typically 2.0 pounds per inch (0.36 kg/cm) or less. Top female climbers are under 1.8 (0.32 kg/cm). Of course, there are always exceptions such as Lance Armstrong who is about 2.1 pounds per inch (0.38 kg/cm). He overcomes his greater weight by having even greater power.

This doesn’t mean that you can’t excel if above these common ranges. It simply means that you must also have a higher-than-normal power output per pound (kilogram) to overcome the greater weight as Lance does.

Reducing your excess body weight and the weight of your bike and running shoes will potentially pay off with faster race times. But there’s risk associated with such weight reductions. If you lose muscle, especially the muscles that are used for swimming, biking or running, you are likely to be slower. Replacing heavy components on your bike with the lightest (and most expensive) equipment available raises the risk of that component failing during a race. For example, lightweight tires are one of the most effective weight reducing changes you can make since they lower rotating weight. The downside is that they are more likely to have a puncture. A super-lightweight saddle is more likely to break when you hit a pothole. Featherweight handlebars have been known to snap with a powerful rider is climbing out of the saddle. Running in racing flats may increase your risk of injury. Lowering your racing weight provides both reward and risk.

Of course, for riding a bike on a flat road or indoor trainer (regardless if the front wheel is raised or not) and for swimming, mass is not critical. The tug of gravity on your body and equipment is not as great. In fact, a big triathlete riding a bike on a flat course is generally faster than a small triathlete since being big usually means having more power. That’s why if your weight is above the pounds-per-inch ranges suggested above it’s best to select flat race courses when possible.

Comments

[Christopher mumford]

For males, 2.2 pounds/ inch would make a 6'2 male weigh 165 pounds. I do not know any males that fit this profile. Is this realistic? Thanks for the curious food for thought.

[Peter]

Joe, great article! Reminds me that I should lose some more weight.

FYI, small typo in your article. One pound equals 0.45 kg or 450 g not mg

(454 g to be picky)

Love reading your blog.

[FG]

While riding up a hill, is there a component of power that is being used to overcome the effect of gravity? Has there been a study done to measure that?

For example using an analogy from circuit analysis, total power is defined as the sum of the resistive (real) component and the reactive (imaginary) component. Refer to complex numbers.

On a flat road the imaginary component due to gravity would be zero just like in a purely resistive circuit the reactive component would be zero. Whereas riding up a hill the effect of gravity needs to be overcome and the total power (from the reading on a powermeter) will be the sum of real and imaginary component. I believe that the real component is close or just below the rider's FTP and the imaginary component is the one used to overcome the effect of gravity.

In electric circuits if the reactance is very high then the source generating power (alternating generator) has to produce more reactive power which reduces the overall efficiency of the generating system. If reactance is very low then total power is very close to real power.

I wonder if a similar study has been done based on this analogy that is know how much of the watts generated going up a hill are used to overcome gravity.

[Joe Friel]

FG--I've never seen anything on this.

[FG]

Does it make sense to you though?

If you ride up a hill that is say 5 minutes long and your FTP is 250W but you are able to average 320W on the hill that is 28% above the FTP which would put it in VO2Max or Anaerobic zone. How is the additional 70W explained?

[Brick]

Very interesting. I did some calculating on a couple of Elite triathletes considered to be the biggest pros in the sport in Matt Reed and Torbjorn Sindballe. Reed is 6'5", 180 pounds (2.33) and Sindballe is 6'2" 176 (2.37). I'm sure when Peter Reid was racing he'd be right there too.

[Joe Friel]

FG--You would have gone up the hill faster at that power (or any power) if you had less weight to lift.

[Coach Ian]

This is a great one Joe. I did the math, I am 3.2 and quite muscular. I have been using the information in the Paleo Diet For Athletes to lose weight, I have lost about 30lbs, so far. My arms and legs are a lot smaller. But I still climb like a slug, every incline seems to just slow me down. I also lost a lot of power, with the weight. Getting down to under 200lbs (I am 6' 3") seems impossible. I am training for a RAAM Qualifier in September.

Any Suggestions?

Thank you!!

[JoeFriel]

Ian--Hang in there. It takes time to improve climbing. You're doing the right things. Just keep it up.

[Brian]

Ian - I am in the same boat as you. I am 5' 11" 200 lbs - muscular but I do carry extra body fat (although I have lost a bit of it over the past 6 months). My training partners have more traditional triathlon builds - one is 5' 8" 140 lbs, the other 5'10 175 lbs. I struggle to keep up on the hills, although I am finding that the gap is getting smaller between us. What I do find is that on the flat portion of our races and during our taining rides I am far more powerful. I agree with Joe's comment - hang in there - look at the hills as an opportunity to develop your power and hit every one you can find. In a short period of time you will notice an improvement in your climbing speed and that will provide the motivation you need to continue facing the hills head on!

[Coach Ian]

Thank you for the encouragement guys. When the road is flat, I feel so strong, like I could pump out lots of speed. I have 5 and a half months to go, I will keep working at it and let you guys know the results.

I will be in Wales soon, very hilly. I find that when I attack hills, half way up, I burn out, and then go into 27 in my back cassette and climb at 10km/hr. Anyways, enough about that. I will report back in 8 weeks.

[Jeff Joseph]

Some of you don't find the numbers to make sense -- but here's a fair number of pro stats--
http://www.trimaven.com/Pro-Men/
examples:
Andy Potts -- 6'2 175 ratio: 2.36
Chris Lieto -- 6'0 160 ratio: 2.22
Chris McCormack - 5'11" 150 ratio: 2.11
Craig Alexander - 5'9" 150 ratio: 2.17
Eneko Llanos - 5'9" 160 ratio: 2.32

or women--
http://www.trimaven.com/Pro-Women/
Chrissie Wellington- 5'5" 132 ratio: 2.03
Desiree Ficker - 5'7" 125 ratio: 1.87
Michellie Jones - 5'10" 133 ratio: 1.90

[puma speed cat]

This is very detailed and informative article. Thanks for helping me solve my dilemma!

[Ajf 4]

Luckily I read your blog, like your blog, this is the one I've been worried, thank you.

[Rerto Jordans]

I love your blog. I wish more blogs nowadays had valid information like this!