The impact of training on bone mass

Author: Frédéric Delavier and Michel Gundill: chapter from the book "Nutritional Supplements for Athletes".
2011-10-20

Just like muscles strengthen when they are developed, bone mass is built around the joints that are subjected to physical activity. For example, a right-handed tennis player should primarily strengthen the bone mass in their right arm. Running is good for strengthening the bones of the legs…

Many types of physical activity have a beneficial effect on the skeleton, enhancing bone mass. This is mainly true for strength sports and bodybuilding. Conversely, endurance sports tend not to strengthen bones, but rather make them more fragile. K. Bennell (1996) provides several reasons explaining this phenomenon:

• Insufficient calcium intake, especially when there is an increased rate of mineral loss from the body (through sweating).
• Too low an energy intake.
• Low fat content in the diet.
• Hormonal changes that are unfavorable for the stable maintenance of bone mass.

However, it is not only important to increase the number of calories entering the body. Two supplements play a significant role in maintaining bone mass: calcium and protein.

For two years, scientists observed basketball players from a university team (R. Klesges, 1996). After each training session, players lost 422 mg of calcium through sweat. Over one sports season, these increased losses led to a 6% depletion of bone mass. Bone mass at the hip level decreased by more than 10%. With a daily extra intake of two grams of calcium, the concentration of this mineral in the body remained stable, and bones were strengthened. The supplement also contributed to muscle mass growth. This effect of calcium can be explained by a decrease in parathyroid hormone production.

In male triathletes, the administration of calcium in liquid form immediately before and during a one-hour endurance workout at 80% of maximum VO2 reduced the breakdown of bone mass that typically occurs during physical exertion and develops after the exercise (J. Guillemant).

T. Ballard (2005) found that increasing protein supplementation from 1.1 grams to 2.2 grams per kilogram of body weight, taken by young men and women over six months while following a program for muscle development and cardiovascular strengthening, was associated with a more noticeable increase in bone mass compared to the group receiving 1.1 grams of protein.