lets say a rider is 16 stone and rides up a climb
and he then loses some weight but stays the same fitness
how much energy will he expend less on the same climb for each stone lost
and would he then perceive this as a fitness increase

Something something watts per kg…

hth

He can go up at the same power and go more quickly by the ration of reduction of total weight (him plus bike), or go up at the same speed and use less power – by the same ratio.

So if bike weights 2 stone, if he loses 1 stone then the increase is 1/18 (5.5%), the next stone would be 1/17 over that time or 2/18 over original time, etc.

I’ll tell you when I lose some weight.

I don’t see any reason someone wouldn’t identify the correct reason there performance improved.

Having recently gone from 16.5 stone to 13.5 I can say there is a massive improvement in results(probably proportionate to the weight loss+ some). Whilst loosing the weight and frequently being in a calorie deficit my fitness levels (particularly for endurance) where often worse than before and required managing carefully.

However the overall effect was improved results even during weight loss and certainly when stabilised. ..

How are you measuring fitness?

i found when going from 18st to 16st over the period of just one steep climb, i could sprint much faster and even managed to catch the bloke who’d just stolen my lunch.

Well Potential energy is the energy required to achieve a hight gain and is derrived by mass x gravity x height.

So for every stone (or 6.352kg) over 100m of climing 6.352kg x 9.81m/s/s x 100m = 6,231.3 joules of energy less to climb the 100m! or (236 k calories). Actually it will be slightly more than that cause you’ve got to overcome friction, rolling resistance and air resistance.

Isn’t this a very simple rule number 10 question?

‘Fitness’ as a concept is pretty difficult to quantify and much easier to measure by results. If you’re suddenly 20% quicker over the same course because you dropped 20kg then it doesn’t really matter if you can’t measure any discernible increase in ‘fitness’, you’re still quicker.

Echoing Ian’s experience, I’ve dropped 3.5 stone/20kg since January (stabilised my weight at 89kg at the end of July) and the performance increase is huge, at least 20%. I’m now able to climb at almost the same pace as my mate who weighs 73kg and has always been the best climber of our group. The steeper the rise the more his lower weight plays to his advantage (because the greater the effect of gravity Is on inhibiting acceleration think – though I could be wrong on that) but its pretty close nevertheless.