I made a cycling date today with a goal of 100km in mind, but as I was leaving home for the rendezvous, I got a message from my cycling buddy: Flat tire! “Too bad,” I wrote back. “We’ll have a great ride next time.”

I was still determined to get in the 100km ride, despite the heat. From the start I felt I didn’t have my legs — probably a combination of the heat, a bit of wind, and the fact I’m a lazy slug and haven’t been on the bike in two weeks.

Despite the feeling in my thighs, and knowing that I was a gear lower in many places than usual, I was surprised to see Mr Garmin reporting that, if anything, I was going a bit faster than usual. I determined to grasp objective reality and soldiered on.

When I stopped to rest, I was sweating like a pig. Given the high today of 34C, that’s a good thing. I drank plenty of water. Took off my shoes to stretch my toes. Checked in with Nana to let her know I hadn’t been run over. I took a nice long break and finished off a half liter of water before setting out again.

Just as I was preparing to depart, another cyclist came along and sat on the bench beside me. “Hot, isn’t it?” I said. He grunted in reply, a bit surprised I’d addressed him in Japanese. I put on my shoes, my shades, my mask and bandana, and finally the helmet. I pushed Ol’ Paint back onto the pavement and mounted up.

And right away, I knew something was wrong. Pain in my right knee, and more than a little of it. It felt like a charlie horse, on the inside of the knee and a bit above the joint. I pushed with the left and tried not to push with the right as I followed through. It was such an odd thing — I hadn’t had a bit of pain before the rest, and I certainly didn’t twist my knee while I was resting.

I continued on, concentrating power in my left leg (which is the stronger one, anyway), and after some way the pain in the right eased up. I was able to put some power on the right, and I felt I could keep on going.

But it would come back. Every time I had to stop for a traffic light, or slow for speed bumps or pedestrians on the path, I’d feel the same charlie horse above the right knee as I tried to accelerate back to my normal speed. Worrisome. I’ve got a torn meniscus in that knee, diagnosed several years ago, and this was something different. But still I knew that I shouldn’t just ignore the pain.

As this was going on, I was stopping to rest every 5km-8km. Much more frequently than usual as I try to make it at least 10km before a break. But I had numbness in my hands and my toes, and I needed to drink — a lot! At these temperatures and in strong sunlight, I’m well aware that the biggest danger is not that of my thighs blowing up.

Finally, I stopped at the 30km mark and ate some rice balls. Nana had whipped up an enormous batch, meant to feed both me and my riding buddy. I found I was ravenous — not a surprise as it was more than 5 hours after breakfast by this point. I sat on a park bench out of the sun and drank water and devoured rice ball after rice ball (nicely kept warm in my black bag by the hot sun).

I took stock of my situation: I had a slight headache, and there was definitely something up with my knee. I was fighting the heat, but I was pretty confident I was OK with that so long as I didn’t over-exert myself. (I’ve done more than 100km at these temperatures before.) But, putting it all together (and not having a riding buddy to disappoint), I decided it was best to turn back. Same routine with the mask and bandana, etc., and then I was on the road.

Surprisingly, I felt fresher and faster the moment I’d decided to return home (although, yes, I went through the same warm-up with the tender knee for the first few kilometers). I’d let Nana know I was on the way back, and the next time I stopped to rest my hands and refill my water bottles, she’d responded, “Already?” (I hadn’t told her about the knee and the headache, because I didn’t want her to worry.)

I was deliberately taking it easy on the way home, and yet Mr Garmin continued to report that I was beating my usual target of 15 minutes/5km (which means 20km/hour). In particular on the lead-up to the bridge over Tamagawa, and continuing halfway across the arch, I was on the smallest chainring. It’s true that I might have had some assistance from the wind at this point: I was just concentrating on making it to the next rest area before the numbness in my fingers and toes dictated a stop.

In the end, I made it home in one piece. I was definitely in a lower gear than usual whenever force on the pedals was required. I took an extra lap around the apartment tower at the end to bring it up to an even 60km, and then brought Ol’ Paint down the ramp to the parking area. I texted Nana that I was home as I gasped for breath and … sweated.

In the end, I maintained better than 15 minutes/5km for every segment except for the climb where I turn off the river path and ascend back up into traffic. My usual pace, overall, despite the knee pain. After I showered up, Nana and I went to the drug store and bought an anti-inflammatory (the same one prescribed by the knee doc).

And meanwhile, my riding buddy was able to get the tire to keep some air. But she’s agreed to have the thing professionally serviced in preparation for the next outing.