I now have a riding partner, an old friend who is about 5 years older than me. I'm 63. He has been riding some, but, now with me, he's riding a lot more.
He used to be an avid rider, with many 150+ mile days --- but that was awhile ago. He really likes to ride, but isn't able to keep up with my normal speed.
And, that's OK with me - it's always easier to go slower than it is to go faster - and I don't mind. It's just nice to have someone to ride 30 or 40 miles a day with.
I just slow down about 3-5 MPH, and pedal faster, in lower gears.. I also take it upon myself to do all of the sprinting, to get out of the way of others. I do all of the pulling, if we are going faster - and he apologizes. I tell him to not worry about it, and to let me know when he wants to slow down or stop for awhile. He does!
Almost all of our riding is on MUPs, which is fine with me, as we are really blessed with fine path systems very close by.
My 30, 36, and 42 mile loops take us much longer to complete, than they did , just me alone.
Now, for the strange happenings......
Jim had something to do today, and couldn't ride. Sooooooo, I went out and rode hard, completing my 42 mile loop much faster than normal (read, like much faster than I used to do, when by myself!!!!)
And, my top speed is down several MPH almost everywhere (when alone), even on the good downhills. And, my average speed is up, when by myself.
Another positive out of this, is that I am increasing my cadence, beyond my normal 80 - I frequently find myself between 90 - 100. My feet used to fly off my legs at 100, and my legs left my body at 110.... LOL..I looked down once today, and saw 119.....
I guess you could say that Jim has jarred me out of my "rut," and forced me to do things differently. But, I don't seem able to push as hard in the BIG gears,,,, hence, my lowered top speed.
Now, if I can just get my top speed up ---- maybe I will see 40 MPH.
You may also be falling into a trap I did for a while...Spinning too much and therefore not building muscle. When you are riding with your friend, try a higher gear for some of the time to put some real resistance on your legs...It's the virtual equivalent of climbing hills or riding into the wind.
I don't know if this is relevant but I have several "time trial" routes that I ride by myself. Otherwise I ride with my gf. I'm 63 and she's 55. Anyway, I was sort of just trying to get miles in when I lost a month of riding time to gout and then pneumonia. I got back on the bike and, after a few rides, did my fastest time in years on my 15 mi. TT. Did 16.7 mph. I was amazed due to the layoff. After a couple weeks I had a relapse and lost another week to an upper respiratory infection. Got back on the bike and did a "gentle" 15 mi. TT (same route). 16.5 mph! what?! How is that possible? I've given up trying to figure it all out.