When my girls were all little, they would frequently ask me how old I was. I thought it was fun to tell them a different (usually ridiculous) age every time. Now, the joke seems to be on me. My youngest daughter loves to tell people that I am much older than I really am. Usually the number is in the hundreds. I always make a point to remind her that she is getting older, too. Since Wendy and I aren't the only ones getting older, I can make a good case that we should all be thinking about our bones when we plan our workouts. It is important both for those who are still young enough to be working toward their peak bone density (which is usually reached in early adulthood) as well as for those of us who have passed that milestone but don't want to develop osteoporosis in our older age-I think this should cover just about everyone.
Because of the way bones are stimulated to grow, training for improved bone density has some very specific guidelines. There is a term called, "minimal essential strain (MES)" that refers to the lowest stimulus necessary to initiate bone growth. Only when we exceed this strain will growth be stimulated. Bone cells are regulated so that the activities done on a regular basis do not exceed the MES. Therefore, it is necessary to continually be progressing in order to regularly exceed the MES for continued bone growth. As soon as bone growth has occurred, the same force that generated the growth will no longer exceed the MES. Bone density improvements follow increased muscle strength. As muscles get stronger and lift heavier weights, the bone increases its mass and strength to provide proper support. How long have you been using the same hand weights every time you do your resistance training? While those 12 pound dumbbells might have been enough to stimulate bone (and muscle) growth when you first started using them, your body has likely adapted to the weight and it now falls below the MES. This is good news! It means you are stronger and ready to move up to heavier weights. Don't get stagnant.
Another important principle in bone growth is that the region of the skeleton receiving the strain (by impact or weight) is the area that will receive the stimulus for bone growth. So, in other words, the area of desired bone growth has to be directly loaded. Running is a good way to load the hips (by impact), but not necessarily the spine. Exercises such as the back squat (squatting with a barbell resting across the back of the shoulders) or a shoulder press are examples of exercises that would load the spine. In general, any exercise that requires movement of more than one joint, is weight-bearing, or involves impact (assuming your health allows it) is recommended. Some examples are running, walking, squats, deadlifts, power clean, and shoulder press.
If you are already exercising on a regular basis, make sure you are progressively increasing the amount lifted, and try to include more multi-joint exercises that directly load the hips and spine. If you are not exercising regularly, There's no better time than the present to start! Your bones will thank you.
