Normally as a general rule - 10%-12% increase of your long ride. It seems like your body gets too much rest during the week without biking before the 20 miler.

Totally spent - meaning you did too much/too fast, especially if you just started cycling. When I started cycling, I did 5 miles, and I was totally spent! My long rides were 5, 7, 10, 14, 14, 20, 22, 25, then 32 for my first charity ride. During the week, I did close to half the amount of the long ride two or three times a week. So...it gave me a great balance, by the time I did the 32 miles, I felt great!

Try to do 10 miles, two - three times a week, then do 15 miles. If you still feel spent by the end of the 15 miles....keep doing 10, 10, 15 until you feel comfortable with the distance and you feel like you have a lot left in you to do more, then you can start increasing the miles.

So yes, it's similar to Running. The days you're not cycling, go for a run. One short run, and one long run. Since you started cycling/running combo, make sure you have one or two days off for active recovery. Allow your body to rest/mentally reset.

YMMV.

I know it seems a little "slow" at first and you won't see much weight loss result, but then eventually it starts to get better and the pounds start to shed. I lost 20 pounds this way (Bike/run).


Again, if you're feeling too spent - take a look at your hydration/nutrition plan....otherwise, you may be pushing yourself too much because you're excited about cycling. :-)