Exercise and bone health

It makes intuitive sense that exercise and bone health are tightly related. Regular exercise can help prevent bone loss and decrease the risk of falls and fractures later in life. Exercise can help with muscle strength and bone strength, improving balance (1).

At the same time that the muscle contraction during exercise leads to muscle grow, it also causes mechanical strain on the bones, leading to bone adaptation (1).

As seen in the article Nutrients for bone health, bone tissue undergoes opposing processes of resorption and formation. Therefore, bone loss occurs when resorption is greater than formation.

Most (about 90%) of our peak bone mass is gained from infancy until about 20 years old (1, 2) and it peaks around age 30 (2). In general, men have greater bone mineral density (BMD) than women (1, 3). Women start losing BMD earlier than men (30s vs 40s). Bone loss can result in osteoporosis particularly in postmenopausal women, leading to increased risk of fractures. This process is likely driven by oxidative stress and the decline in oestrogen that happens during menopause (1).

Exercise and bone health

In a similar way that exercise induce adaptations in our muscles, it also puts our skeleton under forces that lead to bone tissue adaptations. Therefore, exercise can help increase BMD and bone strength (1).

The effects of exercise seem to depend on when it’s undertaken. As we’ll see below, the earlier you start, the better.

Children and adolescents

Children who are physically active have greater bone mineral content than sedentary ones when measured in real time, a few years later and even in adulthood (1, 4). During childhood, weight-bearing exercise may increase bone stregth and around puberty it may increase BMD (1).

Adults

High impact exercise can increase BMD in adults, albeit to a lesser extent than when performed earlier in life. Some evidence indicates that for women this applies only before menopause (1). Some evidence indicates that sedentary women with osteoporosis may benefit from a combination of soy intake and resistance exercise to increase bone strength (4).

Older individuals

High impact exercise can help older men (i.e. 50 years and older) increase BMD and bone mineral content, however it doesn’t seem to help older women (1). There is an exception: female master athletes who participate in power disciplines (see section What kind of exercise? below) have healthier bones than the general population and those who participate in endurance exercise (3).

Athletes

Athletes are a special population because of the large physical demands they undertake. While some types of exercise are associated with better bone health (see section What kind of exercise? below), athletes’ bone health may be negatively impacted by:

Low energy availability: it is recommended that athletes consume a minimum of 45 kcal per kg of lean body mass per day. For example, an athlete with 60 kg of lean body mass should consume 2700 kcal per day at the very least. Athletes in weight category sports who are cutting weight and those who lack the opportunity to eat enough due to training or competition demands can fall short and compromise their bone health (2).
Low carbohydrate availability: it is not clear how or why, but it seems that athletes undergoing prolonged endurance training can benefit from carbohydrate intake to mitigate bone resorption (2).
Low protein intake: as seen in the article Nutrients for bone health, protein is essential for bone health and contrary to old beliefs, a high protein intake does not contribute to calcium loss (2). In addition, a study in adolescent swimmers suggests protein taken post-exercise can stimulate bone turnover process, leading to bone tissue accrual in this population (5).
Low vitamin D: as seen in the article Nutrients for bone health, vitamin D is essential for calcium and phosphorus metabolism. Therefore, athletes who are deficient in vitamin D are at increase risk for fractures (2).
Excessive calcium/sodium losses: athletes who sweat a lot due to prolonged sessions or weight cutting practices may lose enough calcium and/or sodium to potentially disturb bone status. If this is the case, athletes should ensure extra intake before and during exercise (2).

What kind of exercise?

The types of exercise that have been used to demonstrate benefits on bone health include:

Weight-bearing exercise (1) (a.k.a. resistance exercise), such as strength exercise using weights, weightlifting, powerlifting, bodybuilding, etc.
High impact exercise: such as jumping/hopping exercises, step training, some team sports (e.g. rugby, football, volleyball, hockey), combat sports and power athletics (e.g. sprints, jumping disciplines, pole vault) (1, 2, 3, 4)

References

Santos L, Elliott-Sale KJ, Sale C. Exercise and bone health across the lifespan. Biogerontology. 2017 Dec;18(6):931–46.
Sale C, Elliott-Sale KJ. Nutrition and Athlete Bone Health. Sports Med. 2019 Dec;49(Suppl 2):139–51.
Ireland A, Mittag U, Degens H, Felsenberg D, Ferretti JL, Heinonen A, et al. Greater maintenance of bone mineral content in male than female athletes and in sprinting and jumping than endurance athletes: a longitudinal study of bone strength in elite masters athletes. Arch Osteoporos. 2020 Jun;15(1):87.
Willems HME, van den Heuvel EGHM, Schoemaker RJW, Klein-Nulend J, Bakker AD. Diet and Exercise: a Match Made in Bone. Curr Osteoporos Rep. 2017 Dec;15(6):555–63.
Theocharidis A, McKinlay BJ, Vlachopoulos D, Josse AR, Falk B, Klentrou P. Effects of post exercise protein supplementation on markers of bone turnover in adolescent swimmers. J Int Soc Sports Nutr. 2020 Apr;17(1):20.

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Exercise and bone health