Influence of running volume and hormonal status on bone mineral density in male subjects

• Forschungsstelle: BASPO
• Projektnummer: FG03-02

Schlüsselwörter (Deutsch)

bon mineral density
genetic
physical activity
homonal status
osteoporosis

Kurzbeschreibung (Deutsch)

Bone mineral density (BMD) is influenced by several factors such as genetics, gender, physical activity, macronutrient intake and hormonal status. Osteoporosis is characterized by an alteration of the bone structure an a BMD below the normal values of gender-matched healthy young adults. This disease is associated with an increased risk of fractures

Projektziele (Deutsch)

Investigate the putative interaction between exercise and hormonal status in male individuals. This prospective study is performed on;
a) two groups of runners i.e. long distance (>80km/wk) and middle distance (30-50 km/wk)
and
b) on sedentary individuals.
during 2 years, they will perform 3 yearly measurments of BMC, endurance capacity, nutrition an biochemical variables (plasma hormones).

Abstract (Deutsch)

Résumé:

Background: Exercise increases mechanical forces on the skeleton and therefore has a positive effect on bone mineral density (BMD). However, it has been repeatedly reported that female endurance runners with amenorrhoea present a lower BMD which may be explained, in part, by a lower plasma estrogen concentration. A few cross-sectional studies have also reported that male high endurance runners (more than 90 km per week) present lower BMD, especially at the lumbar column site. Here also, the bone loss, possibly due to a reduced sex hormone concentration (testosterone and estrogen), may override the beneficial effect of mechanical forces, however, this issue remains to be thoroughly investigated.

Working hypothesis: Changes in BMD, induced by long distance running mostly depend on: 1) sex hormones (testosterone and estrogen) and 2): local mechanical stimuli. We hypothesis that only long distance runners with low blood sex hormone levels will experience a decrease in BMD over time. Additionally, individuals with high mechanical stimuli will have a higher BMD.

Specific aims: We plan to investigate the relationship between exercise (weekly running distance and local accelerations while running) and: a) bone mineral density and bone scanned area, b) hormonal status and c) interaction between a and b. Moreover, we plan to assess whether the bone response is d) site specific (e.g. femur, rachis, heel) and e) related to other variables (body composition, nutrition etc.)

Protocol and laboratory methods: 100 healthy male subjects (25-45 years of age): 20 control subjects (0-5 km/wk), 40 middle distance runners (30-50 km/wk) and 40 long distance runners (more than 80 km/wk) will be investigated longitudinally during 2 years. They will be asked to keep their usual running and dietary habits. The following measurements will be performed: a) Bone mineral content, bone mineral density and bone scanned area b) Maximal aerobic capacity measurement c) Body composition measurements , d) blood variables e) urinary variables (, f) analysis of the running and walking pattern and g) nutritional assessment. These tests will be performed on 3 occasions; 1, at the start of the study; 2, following one year of monitoring the subjects; 3, following 2 years of monitoring the subjects.

Relevance: The present research protocol will help us to better understand the