Falcon part if it is sadly growing older. I do think we have to try to exercise muscles to keep them going as long as we can, as Jess said, yoga, Pilates and hand weights. If you can get a good gentle DVD for beginners or similar just a few minutes a day helps.
BUT also, think before you bend and pick up. I used to bring in trainers to show staff how to do 'Manual Handling' (picking things up) . There are ways to do it more safely so you don't injure yourself. Try to avoid bending and lifting together. Knees bent is best (! though you need good thigh muscles!) or get the toddler to stand on your sofa or similar when you lift him or her. If you can't do either of these then lift slowly and carefully, no sudden jerking movements.
Hope this helps.