It is an established fact that exercise increases bone density. It is also a well known that a large number of people undergo age related decline in bone mass, and this is the leading cause of frailty and fracture in older adults. Women, in particular, are susceptible to osteoporosis following menopause. Therefore, it is necessary to ensure that individuals do not lose their ability to move about in later years due to the loss of bone density.

Calcium and bone density:
It is true that many women take calcium supplements to ward off osteoporosis. However, taking in calcium supplements alone is not enough to maintain bone density. Magnesium and other micronutrients are also required to assimilate calcium. In addition, strength training is necessary to retain assimilated calcium.

Various studies have collected evidence of strength training increasing bone mass and maintaining bone density. For example, one study in Ontario's Manchester University showed that postmenopausal women who underwent strength training for a year increased the bone mass in their spine by approximately nine percent when compared to women who did not participate in weight training and therefore experienced a fall in bone density.

Experts agree that exercise - strength training exercise in particular - is the key to preserving bone density and maintaining bone mass. Strength training exercise increases bone density, improves balance and develops muscle strength, and all of these factors help older adults improve their quality of life drastically.

Types of exercise
Not all exercises are created equal. Even among strength training exercises, certain kinds of exercises affect bone density and improve bone health more than others.

According to a research conducted by the Bone & Joint Injury Prevention & Rehabilitation Center, three characteristics in strength training exercise make it most suitable for building bone density. These are:

- The magnitude of strain in the exercise: Greater magnitude is found in exercises like weightlifting and gymnastics because of the greater force involved.

- The rate of strain in the exercise: This is where the rate of the impact felt is higher, as in plyometrics (exercises centered on fast, powerful movements) and jumping.

- Frequency of strain in the exercise: This is higher in exercises such as running, going up and down stars and weightlifting where the bones are impacted more frequently during the exercise.

All the three factors above play important roles in developing and maintaining bone density. However, which of these three factors is the most important was not determined by the study, although it was mentioned that people may experience an increase in bone density just by performing weight bearing exercises for 12-20 minutes, three times a week.

Exercises that place strain on the bones like weight lifting and strength training are the best exercises to build bone density. Other excellent exercises for building bone density include stair climbing, running and so on.

Impact of age on bone density
According to studies, exercise can increase bone density regardless of age. It has been seen that weight bearing exercises stimulate the formation of bone cells by retaining calcium. This is most important for postmenopausal women who start losing bone mass due to depleting estrogen levels.

Can exercise lower bone density?
A study found that elite level cyclists actually had lower bone density, leading researchers to believe that activities such as cycling and swimming could lead to loss of bone mass. The reason for this could be due to these factors:

- These exercises are non-weight bearing and do not put any strain on the bones
- The body loses enormous amounts of vital nutrients due to copious sweating
- The calorie deficit following hours of intense exercise could lead to loss of bone mass

Therefore, it is not a good idea to concentrate too much on one form of exercise or do it in excess.

Exercise alone cannot ensure maintenance and development of bone mass, but must be combined with excellent nutrition. This becomes more important when people over the age of 30 years since the body does not build bone cells as well as it did before. Therefore, building strong bones before this age is ideal, but the right diet and exercise can help at any age.