Aftermath: Legs extremely wobbly, but no actual pain as yet - will know in the morning for certain. Possible sunburn due to stupidity of not applying any (slightly underestimated outside temperature upon leaving the house), but mostly on my face (after exertion it's hard to tell the difference) the back of my neck, not on the part of my chest where if it burns it stays pink for eight months. Score.
Conclusions: Need to do more shorter bike-trips on a regular basis. Need to remember to apply sunscreen (idiot). Need to be more religious about re-filling water bottle at Ontario Street stopover (I think it's Greys Park - there's a weird little setup with funny benches whose sunshades are giant bike seats.). Need to wear something other than jeans next time. Need to remember sunglasses going both ways.
Also, it seems I've gotten a lot better at orienting myself in East Van. The reason I got lost at the end of Gladstone was because there were three possible directions I could go and I chose the one that went towards home - this was the wrong choice, as it turned out, but technically the right direction.