Spending time in the garden is an enjoyable, beneficial way to get in your daily exercise. Digging in the dirt, watering plants, weeding and other gardening activities work your muscles, and you can watch your efforts pay off with beautiful flowers and vegetables along with better health.
If bending and squatting to pull weeds or dig is too much for you, a gardening stool can help make the ground more accessible and help you avoid injuring your back or knees. Choosing the right tools can go a long way, as well. You want tools with a good grip and long handles that help you avoid stooping over when possible. You can also make your garden more accessible by planting in containers, raised beds or on a trellis, so you'll be doing less kneeling on the ground.
Since gardening is generally a warm weather activity, it's very important to drink plenty of water and try to limit your gardening to the cooler times of day: before 10 a.m. or late in the afternoon. You'll also want to dress appropriately, in lightweight clothing, and make sure you wear sunscreen and a hat to protect you from sunburn.