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Training for bone health

Training for bone health

Training for bone health

Training for bone health

These days there are so many different forms of exercise out there for people to choose from. I used to work as a personal trainer years ago and I used to tell people about how good exercise is for you, “cardio is good for your heart health”, “weights will make your bones strong” I used to say. These messages are perpetuated by the health and fitness industry, and for the most part they reign true. But do we know what type of exercise does strengthen bone?? And are all exercises equal?? Well… the answer is yes, we do know, but no not all exercises are equal!

Who would benefit?

There are many different reasons why people would want to strengthen their bones, but when I think about those who would benefit the most, two groups of people come to mind. Firstly, postmenopausal women. It is well known that postmenopausal women are at the highest risk of developing osteoporosis (OP). This is because not only does our bone mineral density (BMD) reduce with age, but also our hormones play a role in bone health. As women go through menopause, their bodies stop producing as much endogenous estrogen. This places them at a higher risk of developing OP, because estrogen has a protective effect on bone, against parathyroid hormone (PTH) induced bone resorption or breakdown. Now if that sounds complicated, in laymen’s terms it just means that when your body produces less estrogen, your bone breaks down more easily.

The second group of people I see as benefitting most from bone strengthening would be runners. In this group of people, we see a plethora of different bone injuries, ranging from bone stress reactions to bone stress fractures. Runners can experience stress fractures in the sacrum, pelvis, femur, tibia and in the feet, such as navicular fractures and 5th metatarsal stress fractures. The obvious reason why runners experience so many bone stress injuries is because of the chronic exposure that occurs with running hundreds, or even thousands of kilometres. But in my experience with endurance athletes, very few of them do resistance training, or any training that is conducive to strengthening bone for that matter. Interestingly, running does NOT strengthen bone in runners. However, by making some small changes to their training, we could greatly increase the strength of their bones and reduce the incidence of bone stress injuries.

What doesn’t work?

Whilst I’m a huge advocate for all different types of exercise, the reality is that not all types of exercise strengthen bone. For example, exercise such as cycling, swimming, water aerobics, yoga, Pilates, walking, and even some weight training does NOT stimulate any significant osteogenesis (bone formation) in bone. Furthermore, running does NOT strengthen your bones if you’re are a runner (however it will for a sedentary person, at least in the short-term).

Now think about this scenario that I see commonly. The older age women, comes in to do the group class once or twice a week that mostly consists of Pilates and maybe a few other general exercises thrown in. They leave happy with themselves for doing their exercises, knowing that they will be fitter, and thinking that their bones will be stronger for having done it. Unfortunately, the reality is that they have not done anything to strengthen their bones.

What does work?

To strengthen your bones, your training MUST include one of the following stimuli:

  1. High ground reaction force (GRF) – think jumping and landing
  2. Maximal strength training (MST) with a high rate of force development (RFD) – think heavy squats with a rapid concentric phase
  3. Asymmetric loading – multi-directional movements, trail running on uneven terrain

So, with that in mind, the type of exercises that WILL increase bone strength are things like:

  • Hopping, zigzag hopping, box jumps, box depth jumps, skipping, skipping with weight vest, heavy resistance training (85-90% 1RM), maximal sprinting etc. Also, trail running can be great for bone strength due to the varying terrain – no step is the same.

The science

Fortunately, there is some great research out there for how we can best design exercise programs to stimulate osteogenesis. And the good news is, it doesn’t have to be complicated. If you’re interested in this type of thing and want the full detailed description, I would direct you towards Turner & Robling (2003) and Hart et al (2017). For a shortened version, here is the nuts and bolts of it.

  • Bone receives stress (external force) which produces strain (structural deformation).
  • Strain magnitude  strain on bone is modulated by muscle contraction and gravitational load. This is THE MOST INFLUENTIAL feature of bone adaptation and osteogenesis. Magnitude MUST be high, this is non-negotiable.
  • Strain rate  must be dynamic and faster is better. Thus, slow and controlled resistance training or isometrics yield MINIMAL adaptations to bone.
  • Strain volume  more volume does NOT equal stronger bones because the mechanosensitivity (sensitivity of bone response to load) of bone undergoes a rapid suppression. Thus, there is a law of diminishing returns.
  • Number of loading cycles  considering the rapid suppression of mechanosensitivity, only 20-40 loading cycles are needed. After 100 loading cycles, bone becomes asymptomatic to the training stimuli. That is, the loading has no effect on bone strength. Hence why running does NOT strengthen bone after the first minute or two.
  • Rest periods  After 4 hours, ~ 90% of mechanosensitivity is restored in bone. Thus, longer training sessions are NOT more effective for strengthening bone. Shorter but more intense sessions are more effective. 2x 30min sessions, 4 hours apart would be more effective that 1x 3-hour session.

In Summary

  • Use LARGE loads applied QUICKLY jumping, MST with high RFD
  • Use plyometrics and asymmetrical loading
  • More is NOT better. Keep loading cycles low – 20-40 jumps or heavy squats
  • Shorter more intense sessions are MORE effective than longer sessions

Now let’s consider this information relating to my two populations that I would consider would benefit most from training for bone strength:

Postmenopausal women

If you’re reading this and this is you, think about how many jumping activities or heavy resistance exercises you have done at 85-90% of your 1 repetition max (1RM)? Do you even know what a 1RM is? Most likely not.

The good news is that minor changes to your training program can yield dramatic results to your bone health. For example, just by doing 100 skips at the start of your session over 3 months would greatly improve your bone strength. Alternatively, adding just 20 heavy squats at the start of your session would have a similar positive result.

Runners

Are you a runner? Did you know that running does NOT strengthen your bones? Runners are of a higher level physically that those with OP, so the demands of the exercises must be greater. For runners, things like box jumps with a weight vest, depth jumps, zigzag hops, or a heavy squat program would greatly reduce the risk of bone stress injuries.

Finishing

I hope this had shed some light on how effective training can be for strengthening bone… but also how ineffective it can be if the right type of training is not used.

Thanks for reading

Trent Shannon

DPT Physiotherapy

 

Turner & Robling (2003) – Designing Exercise Regimes to Increase Bone Strength

Hart et al (2017) – Mechanical basis of bone strength: influence of bone material, bone structure and muscle action

 

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TRENT SHANNON
SYSSM Physiotherapist

Trent is a graduate of the Doctor of Physiotherapy program at Melbourne University, and also holds a Bachelor of Exercise Science from Victoria University. Trent has a personal interest in CrossFit, running and for the last 5 years has competed and raced in road cycling. 

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