Building a solid routine of strength, balance, and body awareness exercises will keep your dog strong and reduce the chance of injury. Consider spending 10-20 minutes 3 times a week with each of your dogs performing such exercises as down to stand, stand to sit, roll over in both directions, sit pretty, side stepping, and back up. Balance pads make for a useful tool in building strength.
More info on strength building for your dog, and for you, is coming!