Bone is continuously being modified through bone breakdown (known as bone resorption) or bone formation in response to various stimuli including mechanical loading, nutrition, hormones and nutrient needs. This process allows the body to remove damaged bone as well as repair and preserve bone tissue (Kini and Nandeesh, 2012). If there is a balance between the amount of bone formation and breakdown, bone mass will be maintained; however, as we age, this balance shifts as bone resorption begins to exceed bone formation, resulting in a loss of bone over time (Demontiero, Vidal and Duque, 2012).
Bone mass peaks between the ages of 25 and 30 years and then gradually declines over time, with accelerated losses occurring in women after the onset of menopause (O’Flaherty, 2000). Some contributing factors to the loss of bone over time are increased sedentary activity, low calcium and vitamin D levels, and hormonal changes, especially the loss of estrogen during menopause, which plays a large role in maintaining bone (Demontiero et al., 2012). Greater losses in bone over time can lead to osteoporosis, a disease characterized by low bone mineral density, loss of bone tissue, and increased risk for fractures.
Exercise to Prevent Bone Loss
Exercise can be an effective way to combat these age-related losses in bone, as the mechanical load caused by exercise has been found to improve bone mass and bone mineral density (Turner, 1998). To build strong bones, the following types of training should be incorporated into your clients’ exercise program:
- Resistance Training: Resistance exercises performed with machines, free weights, bands or body weight can have positive effects on bone health. To gain the most benefits from a resistance training program, especially for postmenopausal women who are more susceptible to bone loss, one systematic review article suggests to complete a high load training program three to five days per week at an intensity of 70 to 90% of the client’s one repetition maximum (1RM) for two to three sets of eight to 12 repetitions for a duration of at least one year (Zehnacker and Bemis-Dougherty, 2007). In addition, each exercise must target the specific bone sites that you are looking to improve (Zehnacker and Bemis-Dougherty, 2007; Zhao, Zhao, & Xu, 2015). Because the hip, spine and forearm are most susceptible to fractures due to osteoporosis, weighted exercises that specifically involve action at those joints or regions should be performed. Suggested exercises for improvements in these areas include a weighted squat, leg press, leg extension, hamstring curl, hip extension, back extension, bench press, shoulder press, biceps curl and triceps extension.
- High-impact Training: High-impact exercises that include movements such as jumping, skipping or hopping can be beneficial for preventing bone loss at the hip and spine regions. Greater benefits have been found with exercise programs that incorporate a combination of resistance training with high-impact exercises (Zhao et al., 2015). Impact exercises can include jogging, running, jumping rope and box jumps. Weighted vests can also be incorporated to add additional resistance to these movements. While high-impact training can be useful for building stronger bones, it may not be safe for those who already have osteoporosis and are at risk for bone fractures.
- Low-impact Weight-bearing Training: Low-impact weight-bearing exercises such as walking, using the stair climber or low-impact aerobic fitness classes may be a safer alternative for those who are unable to do high-impact training due to osteoporosis or other conditions. While low-impact training alone may not be sufficient in preventing bone loss, low-impact training programs such as tai chi can reduce the risk for falls and thus prevent fractures. In addition, low-impact training can be combined with resistance exercises for added benefits for bone health.