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Training with elastic bands increases bone mineral density

With age, the decrease in bone mineral density and the onset of osteoporosis are more pronounced. In women, these risk factors are aggravated with menopause (see our article). Bone mineral density (BMD) is an index of bone health and helps to assess the risk of fractures to some extent. The lower the BMD, the higher the risk of fractures. In addition, the lack of physical activity greatly reduces the mechanical stresses applied to the bones and thus prevents their strengthening. Indeed, Wolff's law stipulates that the bone is formed or resorbed according to the mechanical stresses which it undergoes.

As life expectancy increases, it is essential to age better. The loss of muscle mass, the increase in body fat, and the increased risk of fractures often lead the elderly to a significant loss of autonomy. It therefore seems important to practice regular physical activity throughout life to minimize these problems.

Some specific sites are often more affected than others. The hip, the femoral neck and the lumbar vertebrae are generally the most fractured areas. Could resistance training with elastic resistance on a specific area stimulate bone mineral density locally?

The Study

To answer this question, two researchers from the University of Oregon, United States studied the impact of strength training in premenopausal women in different ways. For this, 35 women participated in the study which lasted 12 months. They were divided into 3 groups:

• "Lower Body" group (n = 19): The training program consisted of performing 9 sets of 10-12 jumps and 9 sets of 10-12 repetitions of lower body exercises (squats, lunges and calf elevations).
• "Lower + Upper Body" group (n = 16): In addition to the lower body program, this group also performed 3 sets of 8-12 repetitions of upper body exercises (Pulling, pushing and exercises for arms).
• Control group (n = 24): The women in this group did not participate in any physical activities.

The two training groups performed 2 sessions per week. For lower body exercises, resistance was provided by a weighted vest and expressed as a percentage of each woman's body mass. Thus, during the year of study, the resistance increased from 0% to 10-13% of the body mass. And for upper body exercises, resistance was provided only by elastic bands. For each exercise, to start, the resistance was chosen to allow the execution of 8 repetitions. When women successfully completed 12 repetitions, the resistance was increased.

Bone mineral density (BMD, in g/cm²) was measured at the start of the study, 6 months later and at the end of the study (ie, after 12 months), at the hip, greater trochanter, femoral neck and lumbar vertebrae (L2-L4).

Results & Analyzes

The main results of this study show that only the group that performed upper body exercises significantly stimulated bone mineral density in the lumbar vertebrae (L2-L4) (Fig. 2). This result demonstrates that it is possible to locally stimulate BMD by specific exercises and that elastic resistance, like gravitational resistance, is appropriate to stimulate the bone mass formation.

The BMD increased gradually over time suggesting that it could continue to grow beyond 12 months of training. In addition, this protocol helped to decrease body fat mass in the two training groups (-0.4% in the "Lower Body" group and -1.5% in the "Lower + Upper Body" group).

Practical Applications

This study shows once again that physical exercise is beneficial for health and that regular practice would increase bone mineral density and reduce the risk of fractures that can occur with age. Moreover, it is sometimes difficult for sedentary people to change their habits, and going to a gym would be more difficult. But elastic bands offer an interesting alternative since they allow enough intensity to stimulate bone mass and a multitude of exercises are possible. Regular practice of 2 weekly sessions involving work on the main muscle groups of the body will increase bone mineral density.

And finally, this study shows that it is possible to locally increase the BMD depending on the exercises chosen. It will thus be possible to strengthen, for example, the hip, by performing 10 jumps, 3 times a week. Obviously, it is important that the professional responsible for the prescription of these exercises adapts according to the public to which it is addressed in terms of performance, intensity, volume and frequency.

References

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