I've had a longstanding goal - a 20 mph (32+ kph) time trial on the bike. To a serious racer, this would be laughably slow (breaking one hour for the 40 km time trial is a common dividing line between the weekender and the race boys), but for me, riding my own little time trials along the riverside trail, it's been an elusive summit, ever just out of reach.

It's a flat trail, with four little turns to break your rhythm and many pedestrians, kids on their bikes with Mom and Dad, but beyond that it allows as much flat-out riding as my legs, lungs and heart can bear. I can get over 18 reliably, and I've pushed up over 19 once, but the magic 20 always escaped me.

Lately, my approach to the challenge has been to ride gently out to the trail's north end, a 45-50 minute warmup, then blast the down-and-back 20 miles, then ride home to warm down. It's a great 40 mile workout, and I figured some day things would click. Saturday they did.

You can see my heart rate profile here. The key is the middle section. The graph pops up about minute 52, at the start of the blast, and I held my speed up, keeping my heart rate in the high 150s for the first half hour. That's high aerobic - unpleasant but sustainable. Once I turned around at the south end of my little track (out-and-back is mandatory, to balance any wind advantage), I started kicking it up, until the last 15 minutes, which you can see is in the red zone - anaerobic.

A couple of factors at play here. I'd ridden three times during the previous week, so my legs weren't flat, but none of the rides were particularly long or hard, so I was well rested. Also, I was experimenting with a carb drink, which seemed to keep my usual two-hour bog at bay. When I finished the time trial, I still felt like I had some spring left in the legs, like I could have continued. And mentally, I felt great, not a stress or worry in the world. My life's good, and that makes everything easier.