I usually prefer to ride trails, even if I’m just getting from A to B. Today, though, conditions would have been too wet for a decent off road ride so I chose to ride the roads. This decision was assisted by my wife Ali, who is convinced that my muddy riding gear is bound to break the washing machine. It’s funny because I always thought that washing machines were designed to wash mud and such like from clothes rather than giving up the ghost at the slightest sniff of the brown stuff.
I chose to ride to the delightfully named Horden Stoops where the road rises to it’s highest point as it crosses a low point on a chain of hills. It would give me plenty of hill climbing being at 1,068 feet compared to my house at 295 feet. There are a few small but seemingly insignificant drops on the generally rising route so in some ways it would be like many of my mountain bike rides from home, being mainly uphill on the way out and mainly downhill on the return. I started out with no more of a plan than simply to ride there and back.
On an early, fairly short rise I found myself wondering what I was doing. Riding the climbs would not be rewarded with a sinuous dirt downhill. I thought my road ride might be rather boring so there was only one answer, to up the pace and make it into worthwhile training. With more effort I started to feel better and was concentrating on pace more than random, non cycling thoughts.
The climb from home to Horden Stoops is 773 feet but the app. Strava reveals to me that there were a further 427 feet of ascent on the ride, so 213.5 feet of extra climbing in each direction I reached the top and took some photos. The Lancashire plain in the distance was bathed in a slightly hazy sunshine and looked a little strange.
When I set off down hill I was surprised that I was riding into a head wind. I hadn’t noticed the help I’d had on the climb. What I’ve always found impossible to do is to feel like I’m putting as much effort in on a road descent as I did on the climb. Do more experienced road riders manage to put those watts in on descents or is some relaxation inevitable? On an early, steeper part, I had the typical mountain bike on the road experience of not having a high enough gear to put any effort through the pedals. This has been compounded over the years by a concentration on lower overall gearing to improve climbing and more recently the switch to single chainrings with an attendant reduction in gear range.
The climb had become enjoyable enough once I’d upped the pace and the downhill added speed to the mix. I was enjoying myself. I tried hard to keep putting the effort in but also started wondering if I could calculate how much effort I was applying. One thing I knew was that I’d gained, through climbing, 231,193 joules of potential energy. This is the energy that you can get back by rolling downhill without pedalling. By comparing my times out and back, mixing in the potential energy, using a few vague assumptions and adding a good pinch of fiddle factor, could I find out how many watts I was using? I won’t go into my methodology to avoid offending anyone with an understanding of physics or mathematics but here goes……….
Time out, 41.5 minutes or 2,490 seconds
Time back 23.25 minutes or 1,395 seconds
By dividing the joules of potential energy by time in seconds I find that I used an average of 93 watts just to climb. Coming back I gained 166 watts due to gravity. Now I’ll assume that my speeds were constant in each direction, which is untrue!
Speed out 8.8mph or 4 m/sec, speed back 15.73 or 7.15 m/sec
I’ll use P for the power in watts I’m trying to discover and X as an unknown to make it work!
Out 4*4 =X(P-93)
Back 7.15*7.15=X(P+166)
Calculating……3.195(P-93)=(P+166)
3.195P-297.135=P+166
2.195P=463.135
P=210.995
I like that. It means I averaged 211 watts during my entire ride, on average. Strava estimates my average power as 170 watts but they probably haven’t realised just how much slower and harder work an MTB is compared to a road bike. They won’t know that I wasted energy by braking on the wet tarmac strewn with autumn leaves. There was also the effect of wind which is not usually beneficial. In short, I prefer my figure! It’s interesting that I got such a big proportion of my power on the way back from gravity.
Whilst I’m not likely to be shopping for Lycra any time soon I had a good ride today. It was more fun than the mathematics I’ve subsequently put myself through.
Mountainbiker 