Bones are responsible for the base structure of your body, so it is important to keep them strong and healthy. They continuously cycle though phases of breakdown and remodeling that usually peak at around age 18 for females, and age 20 for males. Once they hit peak bone density, the cycle slows. More bone is being broken down than formed, causing a gradual decrease in bone mass. Weight training can prevent that decline and even increase bone density to help postpone or prevent osteoporosis.
Science
The National Strength and Conditioning Association defines the minimal essential strain, or MES, as the "threshold stimulus that initiates new bone formation." When you exercise at a load higher than your MES, your bones take the impact and get microscopic deformations. This causes osteoblasts, or cells responsible for bone formation, to initiate bone modeling. They secrete collagen fibers in between cells on surface of bone which calcify, thus increasing strength and diameter of the bone.
Exercises
Increasing bone mass is best done with resistance training and weight-bearing exercises. Do all appropriate resistance training in the standing versus sitting position to continually load the lower body. Bicep curls, shoulder press, triceps extension, horizontal chest press and standing bent over rows are examples of exercises that will load the upper body and spine. Exercises for the lower body and hips include weighted squats, lunges, calf raises, and step-ups on a bench. The National Osteoporosis Foundation also suggests incorporating balance and posture exercises such as yoga and swimming to strengthen your stabilizer muscles around your bones.
Frequency/Intensity
The American Council on Exercise recommends weight training totaling 30 minutes a day, two to three times per week for best results. Give yourself at least 48 hours rest between similar muscle groups to allow for full recovery. Weight training should be moderate to high intensity. If you are mostly sedentary, then a light weight training program may be appropriate to increase bone mass. However if you are a regular to exercise, you may need to add more weight to a resistance program because your MES is higher.
Precautions
If you have low bone mass or are osteoporotic, avoid exercises where you are twisting at the waist, such as seated abdominal twists. Also avoid forward trunk flexion exercises, such as back extensions. These exercises can cause unnecessary stress on the spine leading to fractures. Beware of plyometric and jumping exercises, unless cleared by your doctor.
Consequences
Without a proper weight training regimen, bones lose their mass. They physically decrease in size and strength which leads to greater incidences of falls and fractures during normal activities of daily living. Low bone mass can lead to osteoporosis, so it is important to start exercising. It is never too late to strengthen your bones.
References
- National Institute of Arthritis and Musculoskeletal and Skin Diseases: Exercise and Bone Health
- National Osteoporosis Federation: Exercise for Healthy Bones
- "Advanced Health and Fitness Specialist Manual"; American Council on Exercise; 2009
- "Essentials of Strength Training and Conditioning"; Thomas R. Baechel, Roger W. Earle; 2008
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