I really wish we had done this. It is tough for even a relatively fit person go straight to the 20 pounder, so, if you are adopting an older baby or toddler (or expecting a particularly large newborn) do yourself a favor and start building up the needed muscles now, lest you, like us, finish each day feeling like you ran a marathon over a mountain range.
Sure, you could do a regular work out at the gym, but this routine is very specifically geared to the types of motions you will soon be performing.
Needed for this excersize routine: A 20-25lb bag of sand (cat litter or dog food would work too)
1. Carry the bag through at least one international airport while pushing a stroller and carrying a purse. (Walk FAST so you don't miss your connection.)
2. Switch the bag back and forth from one hip to another while you listen to various airline personnel try to explain what's wrong with your (flight/ticket/seat request/child's passport).
4. Take turns with your partner bouncing the bag up and down the plane aisles for 10-14 hours. Every four or five hours sit down, rest the bag in the crook of your elbow and remain completely still. As soon as you can't stand it any more and move your arm, resume bouncing.
3. Stand in line with the bag for four hours.
5. At home. Put the bag of sand in the crib. Take it out again. Put it back. Take it out. Rock it around the room a little bit. Repeat for one hour.
6. Load the bag into and out of a car seat/high chair/stroller at least 15 times a day.
7. Pick the bag up off the floor. Put it back down. Up. Down. Up. Down. Walk the bag over to the window to look at the kitty. Dangle keys in front of the bag. Kiss the bag. Position the bag on your hip. Make macaroni and cheese.
8. Attach a string to the bag. Have your partner pull it around on the floor. Crawl around behind it. Do this for about seven hours a day.
Once you've mastered the above excersizes, poke a few holes in the bag. Attempt to keep the sand from spilling out and repeat steps 1 through 10. This will simulate the awkward squirmy wormy positions you will soon assume while holding a child who is not used to being held and is more interested in seeing what the dog is doing than being held by you (but not interested enough to want to actually be put down.)
Note about this routine:
Following this excersize routine with a bag of sand will build your muscles. Following it with a child will make you love them so much it makes you a little dizzy sometimes.