In the many journals that land on physicians’ desks, there are a few topics that are covered with particular frequency. Osteoporosis is one of them – understandably so, it must be said: it is a very relevant disease in terms of health and economics, and it goes hand in hand with the aging process of the population. And where many people are affected, costs also rise. What do you need to know about this disease in relation to sports?
In a review published in 2015 [1], the incidence of osteoporosis-related fractures in 2010 in Switzerland was estimated at 74,000. The follow-up costs of these new fractures and existing fractures were estimated at 2.05 billion Swiss francs in 2010. The lifetime risk of a 50-year-old Swiss woman to suffer an osteoporotic fracture in the course of her life is about 50% – the fracture risk for men is 20%. Both osteoporosis and fracture incidence increase exponentially with age – and so do costs.
Sport as a cause of osteoporosis
Sports can unfortunately be a cause of osteoporosis, although this phenomenon is so rare compared to other causes that it almost does not affect the previously mentioned figures. Since the 1980s, the concept of the Female Athlete Triad (abbreviated “FAT”, although obesity has nothing to do with it) consisting of eating disorders, amenorrhea or oligomenorrhea, and just osteoporosis (and osteopenia) has been well described. Nevertheless, this serious disease with sometimes fatal consequences is too little known to be detected in time. For the sake of completeness, as incidentally also valid for osteoporosis, it must be clearly underlined that this type of eating disorder does not only occur in female athletes, but more often than expected also in male athletes. This is why today we no longer speak of FAT, but of RED-S (Relative Energy Deficiency in Sport).
Typically, sports with aesthetic characteristics (gymnastics, rhythmic gymnastics or figure skating) or those in which weight plays an important role (ski jumping) are affected. The syndrome is also found in endurance athletes such as long-distance runners or cross-country skiers who, for complex reasons, exhibit eating disorders and develop osteoporosis well before menopause due to an associated low sex steroid hormone concentration. It should be mentioned that because of this pathology, rule changes have also taken place in the disciplines concerned.
Sport as prevention
However, physical activity in moderation (regular and varied) also has a very important preventive role in the context of osteoporosis. If you look at all organs and organ systems that adapt in a positive sense under optimal stress and recovery conditions, you will also discover the bone in this rather long list.
It can be argued that athletic training usually results in bone hypertrophy depending on the size, direction, and point of application of the applied forces. This hypertrophy is once due to the increase in bone density, which in turn depends on a strengthening of the bone bellows scaffold. On the other hand, cortical thickening leads to a widening of the bone. In principle, these functional conversions are possible at any age, but they decrease with the years. Lengthening of the affected skeletal portions as another component of function-dependent hypertrophy tied to the still-functional epiphyseal groove has also been described. However, such changes are only possible before the completion of length growth. Several publications consider hypertrophy acquired during adolescence and earlier adulthood as a stabilizing factor with respect to the future development of osteoporosis and the associated reduction in exercise capacity. Stimulation of the growth plate is basically possible by mechanical means, whereby the tensile, compressive and bending forces that occur have a direct influence on the growth zones of the affected bones.
The sum makes the difference
In addition to these purely mechanical influences, the skeletal system is subject to a variety of hormonal factors that promote bone formation or degradation. Ultimately, the sum of all endocrine and mechanical influences, taking into account the individual genetic disposition, determines the current bone structure and metabolism at each specifically loaded skeletal site. For example, peak bone mass (PBM), although probably largely genetically determined, is influenced by lifestyle. Since the bone mass of children at the lumbar spine (LS) and femur correlates with the activity pattern, great importance must be attached to the role model function of parents with regard to the children’s exercise behavior. Overall, it can be assumed that more active children emerge from adolescence with a 5-10% higher PBM and thus reach the “critical point” for fracture about ten years later than inactive children (provided this advantage is actively maintained into old age). By continuing training into adulthood, increases in bone mineral density of up to 40% have been described in strength sports.
Without movement the bone becomes brittle
At this point, therefore, it may be summarized that weight-bearing physical activities, by which is meant both occupational and everyday activities and health, recreational and competitive sports, are an essential prerequisite for bone health. Without the stimulating effects of the gravitational field or mechanical loading, rapid and pronounced bone mass loss occurs in both the axial and peripheral skeleton.
But what should the training stimuli look like?
Training stimuli should be effective at those skeletal sites where a gain in bone mass is to be achieved, i.e., primarily at the femur, spine, and distal forearm sites most at risk for fracture. In order to achieve bone-effective effects, the training stimuli must be continuously increased. If an exercise program is interrupted, the positive effects achieved on the skeletal system will return to the initial level.
To date, it is unclear whether greater bone anabolic effects can be achieved in humans by increasing the intensity, frequency, or duration of exercise. However, if we transfer the results of animal studies to humans, the loads should be dynamic in nature, performed at the highest possible intensity and frequency, and contain the most versatile exercises possible. It is not the duration, but rather the frequency of these exercises in combination with their intensity that seems to determine the magnitude of the bone anabolic effect.
In training theory, we basically distinguish between the condition factors endurance, strength, speed, coordination and mobility. There are relatively many studies, mostly cross-sectional, that have examined some of these major motor stresses on bone adaptation. In broad strokes, it can be said that strength training performs best. In contrast, pure endurance training is not effective to the same extent. Versatile training with correspondingly high force peaks and versatile force effects on the skeletal system (e.g., jumping, starts and stops, changes in direction during running, rotational movements) also have a not insignificant bone-stimulating effect.
Sport with existing osteoporosis
But what is the effect of exercise on bone in older people who already have (or are at least at high risk of) osteoporosis? The available cross-sectional and longitudinal studies do not always provide coherent results regarding the protective effects of physical exercise on trabecular and cortical bone loss. In general, however, favorable bone-protective effects may also be expected in this situation. In a recently published paper [2], authors convincingly demonstrated that significant improvements in the lumbar spine region and somewhat less significant effects on the femoral neck region and total body could be achieved within the ten-month observation period at an intensity of two to four times per week of complex (mixed) training. Very clear and significant improvements were found for the training groups – in relation to the recorded conditional and coordinative parameters of endurance, isometric maximum strength, mobility, reaction, orientation and balance ability, but also in well-being and pain reduction. The quality of life also increased.
Other sources point to positive effects of strength training at higher stages of life – but working with weights is not always easy to perform (mainly because of weakened muscles).
Reduce risk of falls
An indirect but very important effect of such complex training programs on osteoporosis is the reduced tendency to fall. Fractures, which are the main problem of osteoporosis, are mainly caused by those falls that occur less frequently thanks to improved strength, coordination and balance.
It goes without saying that in the presence of osteoporosis, Medical Training Therapy (MTT) alone is not sufficient. Rather, other therapeutic measures such as antiresorptive or bone-anabolic preparations and, of course, the time-tested calcium and vitamin D3 form the basis of the therapy. Nevertheless, it remains indisputable that a properly practiced sport plays an enormously important role in the prevention and treatment of this so important widespread disease. As with cardiovascular disease and other conditions, the drug “sport” is an effective therapeutic agent. With very few side effects, cheap and easy – what more could you want!
Literature:
- Bally M,Kraenzlin M: Osteoporosis Update 2015. The Informed Physician 2015; 4: 45-49.
- Kemmler W, et al: Benefits of 2 years of intense exercise on bone density, physical fitness, and blood lipids in early postmenopausal osteopenic women: results of the Erlangen Fitness Osteoporosis Prevention Study (EFOPS). Arch Intern Med 2004; 164: 1084-1091.
HAUSARZT PRAXIS 2016; 11(7): 6-8
