Did you know that after three weeks of working out with weights with a medium-high intensity, the density of our bone tissue starts to increase? And, if you start at an early age, the results stay with you, even when you are older?
The skeletal structure of your body can respond to the application of mechanical loads at a young age, developing mass and force in a short period of time: this process is known as 'modeling.’ The mass and force of our bones usually reach their maximum levels between our second and third decade of life.
As a result, during the process of aging, our skeleton starts to lose its mineral properties, that is, its density, mineral content, structure and strength leading to the risk of osteoporosis and fractures.
Fortunately, while this process is inevitable, it can be slowed down. The role played by physical activity in the promotion of bone 'remodeling' is widely known. Exercising limits and slows down the physiological demineralization that takes place over the years. The speed of this process is determined of course by the dynamic rate of load application and the duration of the training sessions. In general, activities that produce a force of reaction on the ground that exceeds our body weight by one or two times results as being most effective: in other worse, walking and running are more useful than cycling and swimming.
Given the importance of strengthening your bones in order to prevent osteoporosis, the US Physical Activity Guidelines encourage children and young people to include specific exercises in the 60 minutes of recommended daily physical activity, for at least three days a week. (http://www.ncbi.nlm.nih.gov/pubmed/25076937). The activities that are performed in loadless conditions (swimming and cycling, for example) or in static conditions (stretching and balancing exercises) do not stimulate, or only slightly stimulate the process of osteogenesis (the production of new bone material).
The osteogenetic function of aerobic exercise (e.g. walking, running) is only effective if the activity level is intense and, in the case of strength training, only if this is done using heavy weights. It is recommended to vary the direction of the counter-resistant movement during physical activity in order to obtain a multi-planar reinforcement of the bone structure.
To obtain a significant bone remodeling effect, the optimal duration of the training program is for at least four to six months. The benefits of regular physical exercise can be seen starting from two-three sessions a week (http://www.ncbi.nlm.nih.gov/pubmed/25245313).
Some studies intend to determine if the positive impact of the physical activity performed during the age when your skeletal structure is developing will last at an adult age. A very interesting study compared the bone characteristics of the throwing arm and the non-throwing arm of a 94 year old ex major league baseball player who retired 55 years ago. The analyses demonstrated that the throwing arm of the person studied (which was not his dominant arm) had a total bone section and force that was higher than the other arm (the dominant limb in day to day life), regardless of the fact that the muscular indexes are in favor of the dominant arm. (http://www.ncbi.nlm.nih.gov/pubmed/24879028).
Another study measured the bone mineral density (BMD) of 46 male athletes with an average age equal to 22 during their active career, and then examined them again at an average of 39, after retiring. The values relative to bone density did not show differences between the active and inactive period. (http://www.ncbi.nlm.nih.gov/pubmed/22806559).
Therefore we can conclude that physical activity is important at any age, because the quality of the bone tissue at an adult age and at an older age is influenced by the optimization of skeletal growth at an infantile, adolescent and young age. Strength training, in particular, can be considered one of the most important positive stimuli in terms of bone health.
A program of physical activity that is effective for bone health involves 30 minutes of weight training for four or more days a week. To stay motivated, select an activity that you like to do. There are many different ones, which encourage you to get up and start moving. The 30 minutes of exercise can be carried out in a single session or divided into smaller fractions. A great way to get started is to walk for 10 minutes at a fast rate, three times a day.