Made my peace...

[marni]

I too am a moderately slow biker. I have been working hard for several years to improve my speed by biking more and pushing myself but the improvement is very slow. Recently I have been doing jogging intervals on the cross ramp or treadmill at the gym. I have finally gotten to the point where I can consistently hit 16 mph for long rides or sometimes even 17 if I have any tail winds. The difference is that I am not wiped out at 16 after 60 -75 miles and I can do more if I have to.

I think the jogging intervals are probably helping, but I now have shin splints so its a mixed blessing. Having lost another 10 pounds and 3 % body fat probably helps as well as well as being in better shape. But all other variables aside, slow twitch muscles cannot transform themselves into fast twitch muscles, although training can improve strength and reaction of fast twitch muscles.

It really doesn't matter as long as you can get on the bike and enjoy yourself however ahd wherever and whenever you ride.
marni