There are many benefits that exercise brings to our body. Among them, it is key to maintaining the density of our bones. Dancing, running, taking small jumps or doing weights are some of the exercises that keep the skeleton in good condition.
Wolff’s law: the more exercise, the more bone
That our skeleton is capable of adapting to the physical stimuli it receives is something we have known for more than a hundred years. At the end of the 19th century, by observing anatomical dissections of the human skeleton, the anatomist Julius Wolff realized that in those areas of the skeleton that had suffered a greater mechanical load, bone formation had been greater, while in areas where physical stress was low, bone formation was impaired. This principle is called Wolff’s Law.
Years later it was expanded by Harold Frost, who postulated that our skeleton works in a similar way to a thermostat, but adapting to mechanical stimuli rather than temperature. This means that if the mechanical stress exceeds a certain threshold in an area of our skeleton, our bone responds by forming more tissue to generate more rigid bones and thus reduce mechanical stress. On the contrary, if in an area the mechanical stress falls below a certain threshold, there will be bone degradation. This is known as the mechanostat theory.
But how relevant is the density of our bones? Certainly yes. The amount of bone tissue and the microarchitecture it acquires in the skeleton are key to avoiding fragility fractures in the future. With age, and more markedly in women after menopause, we lose bone mass, our bones become less dense. This is what happens in osteoporosis, where the risk of some of our bones breaking is quite high.
One of the questions that has given the experts the most headaches has been understanding how our bone cells feel physical stimuli. Apparently, gravitational forces and muscle contraction subject bone tissue to small deformations, which are felt by bone cells – mainly osteocytes -, amplified in their environment and transformed into a positive biological effect called mechanotransduction.
Exercising in adolescence to age better
In addition to a diet rich in calcium and adequate levels of vitamin D, the health of our skeleton is influenced by the exercise we undergo. The growing years are especially critical for increasing bone mineral density, as this is when our bones are most sensitive to exercise. In fact, the World Health Organization (WHO) strongly defends the benefits of physical activity for bone health in children and adolescents.
Specifically, around puberty between 25 and 30% of bone mass accumulates in our skeleton, which is equivalent to the bone that we will later lose during aging. Optimizing that peak can help maintain good bone health throughout our lives.
It is estimated that a 10% increase in peak bone mass can delay the development of osteoporosis and reduce the chances of suffering a fragility fracture by up to 50%.
What type of exercise is best for building bone? It depends on the age
Moderate to vigorous physical exercise favors a higher bone mineral density. However, not all physical activities have the same bone-forming effect on the young skeleton.
In particular, impact sports that involve running, jumping or gaining weight have greater benefits on the skeleton compared to less impact sports such as cycling or swimming. Although the time and intensity of physical work required to achieve bone benefit is not exactly known, most of the interventions that have achieved a positive effect have required between 3 and 60 minutes a day, several times a week (between 2 and 5 sessions).
In adulthood, however, the effects of exercise on the skeleton appear to be more modest. Most of the studies in which interventions have been carried out speak of a small increase in the formation or a decrease in the loss of bone mass. But this does not stop it being interesting, because at least it is possible to delay the appearance of the risk of osteoporotic fracture.
Again, the type of exercise performed in adulthood is decisive when it comes to having better results. Exercises with weights, which involve an increase in normal activity, which are medium-high impact, several times a week seem to be effective to, at least, prevent bone loss.
In addition, exercising with progressive power and continuously strengthens both bones and muscles, which will reduce the risk of fractures and injuries in older people.
In short, physical exercise allows us to improve our bone quality and reduce the risk of fracture at any age, with different levels of improvement depending on the type of exercise and the intensity with which it is performed.
Arancha R. Gortázar, Associate Professor of Cell Biology. Principal Investigator Bone Physiopathology Group, CEU San Pablo University and Sara Heredero Jiménez, Assistant researcher, CEU San Pablo University
This article was originally published on The Conversation. Read the original.
George Holan is chief editor at Plainsmen Post and has articles published in many notable publications in the last decade.