Our bones reach maximum bone mineral density by the time we are 30 years old, at which point the bones are at maximum strength and density. The amount of bone mass that we have at this time is largely determined by what we did, 10 years earlier with 90% of all bone growth occurring before we are 20. Peak bone mineral density is influenced by numerous factors including genetics, environment (the amount of vitamin D that you are exposed to), nutrition (consuming a varied diet high in nutrients associated with bone growth), and exercise. Exercise helps build strength in our bones through additional load, physical activity including jumping, running, hopping and rapid change of direction movements working against gravity aid in obtaining a higher peak bone mass.
Traditionally exercise associated with children and teenagers has involved participating in sport of some kind, however as we reach those critical years between 16 and 30 many people move away from sport as other lifestyle factors have a greater influence. It is during this time that individual activities such as walking, jogging and weight training can help you achieve your peak bone mass. So why is peak bone mass so important? Bone mass declines by approximately 0.5% per year from the time we are 30. By having a higher peak bone mass to begin within you can reduce the risk of bone damage later in life, and physical activity can help you stem the rate of bone loss.
What if you sustain a major bone break or crush injury when you are over 30? When children break bones, the traditional treatment is to immobilise the injured area for a period of 4-6 weeks to allow the injury to heal. This is generally successful given that the body is still in a bone building phase, and bridges can be formed between the gaps to allow repair. Once we are over 30 the same principal is generally employed to immobilise the injured site, but sometimes this is not as successful, as the bone is not necessarily in a growth phase. The good news is that the same principles apply with added load promoting bone growth.
Bone growth is promoted in two ways, the first of which is increased muscular activation around the area. Increased muscular activation promotes bone growth with the attachment sites of muscles pulling on certain areas of bone. All of them muscles in our body are anchored to bones at different land marks through tendinous insertion points, with specific targeted exercise theses tendons pull on the bone creating load, and stimulating bone growth. The other way in which bone growth can be stimulated is through additional weight-bearing and load. Through load bearing movements such as walking, and weights training bone growth can be targeted. Load bearing exercise increases blood flow to the area, and the need for the bone to be as strong as possible to support the increased load, simply the bone will adapt to the additional stimuli.
When is it time to ditch the moonboot? Using an injured area through a safe and individually prescribed exercise programme can greatly improve your recovery time from an injury, starting off with muscular activation exercises and building towards weight bearing exercises with additional loads. It is human nature to want to protect an injured site, however this is not always what the body needs to recover and make sure that you reduce the risk of disease such as osteopenia and osteoporosis in later life through maintenance- of bone mineral density.
Ingrid Hand (BSc – ExHealthSc, GraddipSc – ExRehab, MSc – HumMvt)
Exercise Rehabilitation Manager – Accredited Exercise Physiologist (AEP) (ESSAM)
Campbell, B.J (2012). Healthy bones at every age. American Academy of Orthopaedic Surgeons. 1-6.
Sheu, A., & Diamond, T (2016). Bone mineral density: testing for osteoporosis. Australian Prescriber, 39(2), 35-39.