I've complained before about Weight Watchers old programme, mostly with the observation that I was on too few points to have a soft landing when I reached my goal weight.

Well, I've found something else to whinge about: exercise points.

One of the things I really do like about Weight Watchers is that you can earn points by exercising. You get a little slide rule calculator for this much as you do for calculating food points.

Now, the food formula has been reverse engineered and published. Broadly speaking, it's one point for fifty kCals, with some adjustments for fibre and fat content. Fair enough.

The exercise formula doesn't seem to be available, and I think part of the reason is that the exercise calculator is based on perceived effort. This is quite a good measure, especially when you are first starting to exercise because it captures some component of the energy your body is putting into conditioning itself. That's probably pretty valuable, but the problem for me is that it leads me to underestimate my effort after the conditioning is largely done.

So, I have always scored running as being "high" effort - partly because I always push, and partly because the exercise calculator has "running" as one of the example activities. So a five mile run comes in at about 7 points earned.

But cycling? Well... the exercise calculator gives that as an example of a "medium" effort activity. I bumped up my perceived effort a bit to account for the way I push on the bike, but I was still scoring my bike rides to and from work as being halfway between "medium" and "high" effort earning about 8 points for my round trip to work.

Then I checked an exercise calorie counter. That gave me these numbers:

Activity	Time	Energy Used
Running @ 9 min mile pace	45 mins	670 kCal
Cycling @ 16-19 min mile pace	35 mins	570 kCal

Two things immediately struck me:

1. it looks like an exercise point is about 100 kCal once conditioned, and bollocks to this perceived effort nonsense
2. minute for minute, I burn about the same energy cycling as I do running

So this explains why I was so often absolutely hollowed out after biking to and from work, and it means I will be counting my trip to and from work a lot more like two five mile runs than one. It also explains why my cycling never seemed to really help me lose weight, because my body was going into famine mode when I was just not feeding it enough food.

Lesson learned, I think.

Posted by Dunx at March 24, 2009 04:29 PM