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  1. #1
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    Weight loss equals power loss?

    I've probably munted the maths here, but if a heavy rider loses weight, doesn't that reduce the amount of force they can passively exert on the cranks?

    I was looking at ways of lightening my 29er recently, and there's always comments in every forum thread saying that the most efficient way for a clyde to lighten a bike is for the rider to lose weight, but it is that true?

  2. #2
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    Not likely, force is not hinged upon weight rather the force you can exert, power to weight ratio improves with every pound lost unless your falling below optimum weight. Ideally you will be losing weight and improving power t the same time. Testing with a power meter at regular intervals would probably prove this out.

  3. #3
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    I'd be willing to bet that the average 150lb MTB pro can put out more sustained power than the vast majority of people who post in this sub-forum.

    Think about it. It you can stand up from a sitting position relatively quickly, that's about the same amount of raw strength required to pedal a bike pretty vigorously. It really isn't all that much. But can you do that for an hour or two?

  4. #4
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    Heavier often = more power in the weight room, but my personal experience has been when I'm lighter, I feel like I have more power on my bike. I have no science to back it up, just my personal observations. When I used to powerlift, the heavier I was the stronger I was. On my bike, the lighter I am the more power I feel like I'm getting to the wheels.

  5. #5
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    I guess the equation depends on whether weight loss is matched by muscle gain. But then I don't know how much exertion versus surface area it requires to push a gear, so the ratio might be hugely disproportionate.

  6. #6
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    Quote Originally Posted by HelmutHerr View Post
    I've probably munted the maths here, but if a heavy rider loses weight, doesn't that reduce the amount of force they can passively exert on the cranks?

    I was looking at ways of lightening my 29er recently, and there's always comments in every forum thread saying that the most efficient way for a clyde to lighten a bike is for the rider to lose weight, but it is that true?
    Depending on how one tackles losing weight, there could be a potential loss in energy/power if muscle mass is not worked and suffers loss if a speedy drop in weight occurs in the initial stages. Easily countered if the weight loss program includes some weight lifting to fire up the metabolism and you continue to ride your bike to fire up the muscles involved in the pedal stroke.

    The main thing that one needs to lose is fat. A safe goal is to target losing 1 pound per week while still exercising and training. That is a successful and easily achieved target where one will not suffer power loss.

    In the end, things will balance out and you will be able to produce as much power at a lighter weight than you can at your current rate. The difference being, your body mass will be lighter meaning that the same amount of power you can produce now will help you go faster at a lighter weight since the power to weight ratio will have improved. If you had to carry a 40 pound suitcase up a flight of stairs, imagine climbing the same flight of stairs without the 40 pound suitcase. If your body is carrying an extra 40 pounds on it - imagine what it would be like without that extra 40 pounds?

  7. #7
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    I've lost 30 pounds in the last year. to remind myself where I started, I'll often ride with a 30# backpack. It's murder on the hills and wears me out fast. Without the pack, I have a lot more power.
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  8. #8
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    Number one rule, never weigh yourself. Get a scale that does bodyfat thats what you want to track, who cares how much you weigh. Its th body fat % you want to drop.
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  9. #9
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    Quote Originally Posted by fahza29er View Post
    Number one rule, never weigh yourself. Get a scale that does bodyfat thats what you want to track, who cares how much you weigh. Its th body fat % you want to drop.
    Seems like bad advice not to weigh yourself. Especially if one is trying to figure out the power to weight ratio. You can only produce a certain amount of power for a certain amount of time based on genetics and somewhat improved through training. Combining your known power output with your weight allows you to know what your power/weight ratio is and how you could raise that number by dropping weight.

    Power-to-Weight Ratios: Bicycling Training | Bicycling Magazine

    Find Your Ideal Cycling Body Weight | Bicycling Magazine

  10. #10
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    Trying to lose weight without weighing yourself is like trying to balance your checkbook without checking the balance of your account.

    Also Scales that do bodyfat percentage are extremely inaccurate for cyclists. They estimate your BF% based upon water content of the portion of your body in contact with the electrodes. In this case the legs. Endurance training increases the fat/fluid content of the muscles trained giving a false high reading. A handheld unit will give a much more accurate reading for a cyclist.

    With most MTB races where I live containing 1000+ feet of climbing per lap you just don't see very many 200 lb guys on the podium. 5% BF or 25% BF. If you want to ride uphill faster less weight is key. If It comes from the bike or the body either will work but the body contains 90% off the weight of the system. Try to reduce the weight of the entire system 10% With a 220 lb rider and a 30lb bike that's losing 25 lbs. Some of that weight has to come from the rider.
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  11. #11
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    Quote Originally Posted by HelmutHerr View Post
    I've probably munted the maths here, but if a heavy rider loses weight, doesn't that reduce the amount of force they can passively exert on the cranks?
    True, if you weigh 200# and stand on the pedal, you will be exerting more force on the pedal than a 150# rider. However, you can't generate "passive" force. After you stand on a pedal, you have to lift yourself up to do it again.

    But the goal isn't to exert a lot of force, but to generate a lot of power, and more specifically, generate a lot of power without weighing very much.

    You can do a thought experiment to prove that more weight isn't a good thing. Strap two concrete blocks to your waist, and tada, you weigh an extra 60 or 70# and can stomp on the pedals that much harder. But you won't go faster or further, and will tire faster because you have to lift an additional 70# before each pedal stroke. Your body's raw horsepower or wattage remains the same, but power-to-weight ratio has gone down.

    A roadie friend explained to me that a big powerful rider will do well on level roads where the main factor is cranking out watts to fight wind resistance. But a smaller, less powerful rider will do better on a climb because his power-to-weight ratio will likely be better. In mountain biking, there is little opportunity to really lay into it on long flat runs. We almost always climbing, breaking, accelerating, and/or navigating turns. Power is good for all of these, but weight is bad.

    Back to your original statement that big guys can push the pedals harder -- gearing allows us to spin at an efficient speed so that we don't have to put all that much pressure on the pedals and can sit down and pedal most of the time.

  12. #12
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    There's the saying that XC races are won on the uphills. I ride with other guys who are eight inches shorter than me and weigh 50-60 pounds less (I'm about 210, they are 150lbs). I can keep up on the downhills and smaller climbs, but on the longer or steeper climbs I will typically get dropped everytime. It doesn't necessarily mean they are in better shape, just faster because they are hauling much less weight up the hill.

  13. #13
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    I've lost 30 pounds with a little diet, but a lot of interval strength training. First, I ALWAYS work my legs. Squats, weighted lunges, etc. Quads are biggest muscle, and working them first helps promote weight loss and muscle building. I am exponentially faster on my bike now. Lighter = faster. More leg muscle = faster.

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