Is it the bike or is it me?

Factual Questions
1

I put in about an hour a day on my exercise bike (great fun to watch a TV show or a movie and not feel like I’m completely wasting my time) but sometimes it’s more work than other times.

According to the calorie counter, I can average about 15 calories per minute over an hour’s ride (I have no idea if that’s accurate, but I use the counter to maintain a steady pace and make sure I don’t slack off, and 15 per hour usually taxes me to the max).

Just now, though, I found it much harder to maintain that average (I have to average a little above 15 to compensate for the last minute or two when I cool down) and I’m wondering what’s going on:

Is it just that some days, I lack the energy of other days (which I think is most likely) or could it be that the counter is more variable than I would like to think (sometimes, I get over thousand calories in 60 minutes, but more often I have trouble breaking 800.) Since I’m as consistent as I am, I wonder why there’s a variance in the ease with which I can’t or can’t achieve my goal. So: is it simply my own energy levels, or could it be something else? Something mechanical? The weather?

2

Hmmm, I think it’s you. Everybody has off days. And if you’re doing this every single day at what seems like your maximum effort, you might be overtraining a little which would make your performance drop off. You might give yourself a break and take a day off. Or decide to go for longer at a lower pace. Or maybe mix it up, say four easier minutes followed by a minute as hard as you can go.

The temperature of the room you’re exercising in might also be a factor. I find I get my best results when the air temperature is slightly too cool. When it’s hot, my performance drops a lot.

As far as the bike counter accuraccy, I don’t really know how they work. I guess it counts revolutions per minutes and factors in the resistance setting. I guess it’s conceivable that some part of the measuring apparatus could expand slightly with temperature and throw off the reading. But that seems unlikely…

3

Most likely it’s you. Not enough sleep, too much salt in your food yesterday, a change in the weather, time of year, all sorts of variables affect your ability to perform. It’s almost enough to lend credence to that biorhythm nonsense.