General Discussions > Health, Fitness, Nutrition, and Medicine
The Cycling Thread
Alex Simmons:
--- Quote from: khendar on May 03, 2012, 09:37:11 PM ---Alex, you seem to be the expert on power and performance. I'm currently setting myself some fitness goals and was planning on including cycling specific goals such as average cadence, speed, distance and power. Is there some baseline power level (over 9000?) that I should be aiming for ? I've seen numbers for amateur racers such as 3W/kg but at my current weight that equates to almost 400W, which seems pretty optimistic for a fat bastard like me.
Is a sustained output of 400W a reasonable goal ? I'd be measuring on a gym-level cycloergometer, are those numbers pretty reliable ?
--- End quote ---
I take the last question first.
If a local gym cyclometer is accurate, it's likely to simply be by coincidence, rather than by design. I doubt their zero or slope calibration is accurate, nor linear. At the very best, you can hope at least the same machine is consistent each time it's used, however there is no guarantee of that. This is why in our training we use well known and trusted power measurement devices that can be calibration verified.
As for what's a good level of fitness, well that's somewhat linked to what your goals are.
If you want to win a grand tour as a pro bike rider, you'll need to be capable of popping out > 6W/kg for about an hour (what we call Functional Threshold Power - FTP).
As a late 40s guy with a bit of leg missing, I managed an FTP of 4.2W/kg, which is enough for local top level masters age racing.
An FTP of 3W/kg is pretty fit for a non-competitive rider and one can enjoy good riding at that level.
Under 2W/kg and you are untrained and/or probably overweight.
As a guide, an average college age male with average physiology should be able to attain an FTP of ~ 4W/kg provided they train sufficiently and properly over the course of a few years. Due to genetic differences, some will never be able to reach that level, while others will be blessed to have pro-level physiology.
Pithy Power Proverb: "Choose your parents wisely"
In terms of tracking performance, cadence is irrelevant. Just don't pedal stupid fast > 115rpm or slow < 60rpm. 75-100rpm is just fine.
Speed on flatter terrain is influenced by so many things other than your power output that it is not a good guide to progress. As an example, one could race a time trial over 25 miles with same set up, on calm days and produce the same power output but differences in temperature and barometric pressure can result in a time difference of a minute.
There is one exception, and that's speed up a steepish hill climb >7% gradient, as one's power to mass ratio is the dominant factor in determining speed*. So as a poor man's power meter, then timing yourself up a hill climb which might require > 5-minutes is the next best thing to assess your fitness to accurately measuring your power output. I wrote a short article on that for Bike Radar some time back:
http://www.bikeradar.com/fitness/article/training-homebrew-fitness-testing-19175/
So what should you track?
Performance: Power output for set durations (e.g. 5-min, 20-min etc) is best, provided you have the tools to enable that. Otherwise time up a steep hillclimb will be your best marker of progress.
Training: Keep track of duration and intensity as they are the things that matter with respect to inducing desirable physiological changes. Distance is mostly irrelevant, besides distance on an indoor trainer is meaningless.
The principle of sustainable progressive overload is one to apply, gradually increasing the duration and/or intensity of your riding, with an appropriate level of recovery. Knowing the level of increase in workload and timing and amount of recovery is a big part of what I as a coach do to to get the best out of my clients, but as a rough guide for new riders, adding 15-20-minutes per week to your ride volume for a couple of months is plenty. Done properly, one can maintain that for 3-4 months. Dedicated recovery periods would only be rarely required in such circumstances (the old 3 weeks on one week off training methodology is historic bunkum).
The other thing that matters is frequency of training. 4 rides per week is way better than 3 per week, and 5 is better again. It starts to fall away after that, so my riders will typically train 5-6 days/week, with pro riders doing extended periods at times to prep them for the demands of stage racing.
As for goals, then suggest picking process goals (i.e. taking your average ride volume from X to Y hours per week, and riding a minimum # of times per week on average).
* here's a chart I put together showing the relative proportion of energy required to overcome the various resistance forces on a bike on different gradients when riding at a steady state speed (i.e. not accelerating)
GodSlayer:
--- Quote from: Alex Simmons on May 06, 2012, 04:20:12 AM ---* here's a chart I put together showing the relative proportion of energy required to overcome the various resistance forces on a bike on different gradients when riding at a steady state speed (i.e. not accelerating)
--- End quote ---
the whole 'a body at rest...' thing makes me think feel like there should be at least some gravity issue at 0% gradient. isn't gravity contributing to something like rolling resistance? (I don't know what it means -- does a light biker and a heavy biker have the same amount of rolling resistance, since gravity has 0% influence where there's still 13% rolling resistance? what is it you overcome to get going, friction or sumn like that?) (as soon as I had the option to hear no more physics at school I took that opportunity!!)
Alex Simmons:
--- Quote from: GodSlayer on May 06, 2012, 08:24:00 AM ---the whole 'a body at rest...' thing makes me think feel like there should be at least some gravity issue at 0% gradient. isn't gravity contributing to something like rolling resistance? (I don't know what it means -- does a light biker and a heavy biker have the same amount of rolling resistance, since gravity has 0% influence where there's still 13% rolling resistance? what is it you overcome to get going, friction or sumn like that?) (as soon as I had the option to hear no more physics at school I took that opportunity!!)
--- End quote ---
Rolling resistance is directly proportional to velocity, mass and the force of gravity (and a factor accounting for the drop in normal force against the surface if not on flat terrain). We can reasonably assume gravity is a constant.
So two riders traveling at the same speed on exactly the same tyres and tubes, inflated to the same pressure, and on the same road surface, the heavier rider needs to overcome more rolling resistance. But as a proportion of overall energy demand, RR is relatively minor. Having said that, if the Crr of a given tyre is high,e.g. knobbly MTB tyres, and the speeds are low, then the proportion of the energy demand from rolling resistance goes up quite a bit.
The assumptions I used in the above are for a rider on a road bike in a race position, with average road race tyres on a reasonable road. Change the assumptions and the shape of the variation in energy demand over different gradients doesn't change, just the absolute numbers.
On flatter terrain it's all about power to aerodynamic drag, and when ascending hills it's all about power to mass ratio. Power to mass also matters when considering acceleration rate.
Here is the mathematical model and reference to the 1998 paper it was taken from:
WC:
Sweet. Let me just punch in some units for tonight's ride... Oh. Wait. None of the variables are known (including my current mass).
GodSlayer:
--- Quote from: Alex Simmons on May 06, 2012, 07:32:08 PM ---if the Crr of a given tyre is high,e.g. knobbly MTB tyres, and the speeds are low, then the proportion of the energy demand from rolling resistance goes up quite a bit.
--- End quote ---
hardware question:
when MTB tires get worn away to look like road tires, are they just as strong as road tires and now even more suited to road use, or are they in a condition where they should be replaced for safety (with whichever kind the rider prefers)?
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