If you ride a fixed gear or single speed bike, you should go out to your bike cave, wherever that may be, and check your chain tension.
Years of derailleur use has gotten me pretty lax about chain tension. But with no derailleur taking up the slack and accounting for the bit of chain wear over the season, your chain may be slyly preparing to play a game with you. You know that game older kids play with younger ones, where they play tug of war, more and more pulling, fun and excitement till the older one suddenly releases the rope, causing a catastrophic loss of balance and control on the part of the victim. Well, the victim usually comes back for more, but that's a bit of the unexplainable human condition there. Now picture that game in reverse, with pushing. Like, I mean really really pushing hard. And it's an adult male playing the pushing game with a machine, namely his bike. There are a few potential fail points in the pushing system, such as a broken chain/crank/pedal/frame/bars, but I'm not much of a heavyweight so I'm definitely not expecting a breakage of any kind. But when I'm standing and accelerating in my big gear (ok, it's only a 52/21 but it's mashing for me), and a trail bump throws the increasingly loose bottom side of the chain from side to side, enough to miss even one tooth on the beautiful stainless steel track cog, this is a fail point just as potent as any of the others listed.
The rider mashes into thin air, left side of rider's body leading the way earthward as the bars turn the other way, afraid to watch. The dive feels like Superman, arms out, flying free for a glorious 20 hundredths of a second. Leading with the left elbow, Superman augers in and rolls over, in, and around, maybe even under his bike. Asphalt, grass, dirt are inspected from close up. Later, skin inspection. There's also some jacket inspection needed, along with steering alignment, brake levers, bar tape, seat, and vegetation removal.
Speaking of the human condition, I couldn't bear to turn back after 8 minutes of riding, so I grabbed the slightly disheveled bars of my machine with renewed respect and and enjoyed a wonderful, more mechanically attentive ride. I think my muscles were happy to spin out a bit too.
Now, back to your chain. Your bar tape will thank you.
