Three weekly sessions of weight-bearing aerobic exercise are enough to give you general good health, including reasonably dense bones. But the benefits to be gained from strength training and stretching should not be overlooked. The simplest approach to working out that encompasses all those is probably to do aerobic exercise three times a week, with weight training after at least two sessions. Stretch after each workout, with at least one intensive, full-body stretch each week. You could put together any number of combinations and arrangements that would also work, so experiment until you find a setup you like and will stick to.The more you get into it, the longer your workouts will last, and you should build up to at least an hour workout each time. If you are so inclined, by all means, do something every day (just remember to alternate the muscle groups you focus on if you are strength-training every day). In moving beyond aerobics three times a week, I recommend filling in with “moving meditations” like yoga, tai chi, and qi gong because they combine many aspects of fitness.Start with shorter and/or less frequent workouts, and build up gradually to your goal. Get whatever support you need to stick with it. Join a group, take a class, recruit a partner, hire a babysitter (or take turns with another parent looking to carve out some time for exercise). Dress comfortably and appropriately. Stick to a regular place and time at first, until you’ve formed a habit. If you usually exercise outdoors, have a ready-made alternate in mind if rain or cold threatens to keep you from your routine. Schedule your workouts as you would any other important appointment. Write specific windows for exercise in your calendar, and at first be very specific: “Monday: 7-8 a.m., aerobics class at the ‘Y’; Wednesday: 6:30-7:15 p.m., meet Joyce at the gym to lift weights; Saturday: 10-11 a.m. biking,” and so on. Get those dates on your calendar before you start setting up anything else. At least until you’re in the groove, work haircuts and brunch dates around your exercise plans. Otherwise, it is too easy to let one workout after another slide, and that does your bones no favors. Once you are used to regular exercise, and realize how much better you feel when you do it (and how sluggish you feel when you don’t), you’ll no longer have to force those priorities. You may not believe me now, but once you find the forms of exercise that appeal to you, you won’t want to go without. Just because you never could stick with jogging when that was all the rage doesn’t mean you aren’t cut out for exercise. You probably aren’t cut out for jogging (and as far as I’m concerned, that’s just as well), but there are many other options you can experiment with until you find the one that really moves you (pun intended).Starting slow, setting moderate and realistic goals, attending to injury prevention, and doing what you can to ensure success will keep your body physically safe as you introduce it to new ways of moving. It will also cement this most beneficial of all habits. Bite off more than you can chew and nothing tastes good, and you’ll never go back for seconds. Let your body be your guide. You should never have any pain while exercising, though sometimes discomfort is a sign you are pushing yourself, which is not necessarily a bad thing. You may get sore or stiff after a workout, but that shouldn’t last for more than a day or two—if it does, scale back, at least for a while, because you’re doing too much too soon. Making this a lifetime habit (just as you are not “dieting” so much as changing the way you eat, permanently) is very important. When you stop exercising, bone density will stop growing and begin to decline immediately (depending on your age). It will grow again when you start again, but you’ll always be further behind than if you had never let it slide in the first place. What it comes right down to is: move it or lose it!*122\228\2*