Aerobic Threshold

Aerobic threshold AeT is the heart rate at which you start burning fat using oxygen as an exclusive energy source (no lactic acid is produced while burning just oxygen). The lower your AeT, the better, but it's not a crucial number when it comes to performance - AT is much more important. If your AeT rises above your endurance training heartrate, it could become a problem because you would not be burning oxygen exclusively during long easy rides. Tony, who performed my testing, told me that his goal is to have the spread between AeT and AT, expressed as %maxHR be at least 10%, which is what mine is now. My AeT is 70% of HRmax and my AT is 80% of HRmax.

My AeT has risen 11 bpm from 116 bpm to 127 bpm since December 2005. That's usually an indicator that I have cut back on base training. I was confused when I first saw this result because my mileage over the winter and into the spring has been a lot higher than in prior years. From November to February this year I did a long ride (50-130 miles) with the Peach Peloton almost every weekend and rode the trainer 3 to 5 nights a week, so I should have had plenty of base miles, right? The problem is that when riding the Peach Peloton rides, I counted it as winter base training; but considering what my FTP was at the time (probably 220 watts in November and around 245 watts by February) I was doing a lot of that riding in my mid to high tempo range (80-90% of FTP). So even though I was putting in lots of miles, they weren't purely endurance miles that would effectively target my AeT.

I don't think that doing lots of tempo riding in the winter was a big negative, though. It probably did a lot to help me increase my FTP. And if I can start next winter's training rides with a higher FTP of around 260 watts, then riding at the same NP as last year in the winter rides (200 watts) will be 75% of FTP, which will be more a appropriate base mile pace for me and will also make those rides a lot less taxing.