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  • Writer's pictureGary Moller

Low bone mineral density and Stress Fractures in Endurance Athletes

Updated: Feb 15

There seem to be more stress fractures happening nowadays

My impression is that stress fractures among endurance athletes are more freequent because more people than ever are seeking our assistance with this injury. I am not alone in having this opinion.

Take a few minutes later to read some of the research here about the incidence of stress fractures in athletes.

Image: Fit Kiwi ably demonstrating the "Lift & Press", the best bone-building exercise there is

What are stress fractures?

A stress fracture is a crack in the bone, caused by repeated stress that exceeds the rate of repair and strengthening which is the normal response to repeated compression, bending and twisting pressures on the bone. Think of a stress fracture as being like what happens to a wire that progressively weakens (metal fatigue), then finally breaks in two, when it is repeatedly bent back and forth.

For a more detailed explanation, please read this article written for stress fracture patients. Its a good article but far too light on the nutrition side of things which is so important for making a quick and full recovery.

Back in the"good old days", stress fractures were seen mostly in athletes doing daily extreme exercise, such as running 100 miles, or more, in a week (100 miles a week was a training target, for a few weeks at a time, during a training phase, for many Lydiard Method trained runners during the 60's and 70's and few suffered stress fractures).

What is rather disturbing nowadays is the majority of stress fracture cases coming to our attention are being suffered by runners and triathletes who may be doing as little as 30 kilometers of running a week. Stress fractures are occasionally seen in swimmers and cyclists. You wouldn't think swimming and cycling can cause stress fractures, but they do, usually affecting the pelvis and lumbar spine.

By the way, the last swimming-related stress fracture I got to see was in a young male swimmer with a lumbar spine stress fracture. The solution was a coaching one and involved cleaning up his tumble turns.

This article tries to answer the question, "Why?" and outline the measures we can all take to ensure we have strong bones.

It is thought that some forms of exercise are no good for increasing bone strength

Moderate exercise, including running, cycling and swimming will help produce and maintain strong bones, perhaps as effectively as regular weight training. However, there is still the widespread view among many health and fitness experts that non weight-bearing exercises, such as swimming and cycling, do not promote bone strength. There is also the contradiction that stress fractures are more common in distance runners, mostly females. If running builds bone, then how come so many runners suffer stress fractures and often have bone scan results that show low bone mineral density? (I'll explain in this article why the answer is more complicated than just too much running).

It is not uncommon for distance runners, cyclists and other endurance athletes, to have low mineral density of bones like the heel, shin, hips, pelvis and spine and for this to have no obvious association between sporting type or nutrition. The only obvious common factor is endurance training and possibly under-eating. Its not that simple. I'll try to explain as best I can what I think is going on and offer solutions. What you will learn is that there is no single "fix", such as a wonder drug, nutrient or exercise, like abdominal exercises or futilely trying to "engage your glutes". The solution is getting a complex mix of factors in balance while eliminating others altogether, or as best as one can.

Image: Fit Kiwi once again demonstrating near perfect technique. Yes, Fit Kiwi can swim!

Why do many experts believe that swimming and cycling do not build strong bones?

The belief that cycling and swimming do not build bone and may actually cause low bone density is misplaced. This belief prevails due to a number of studies of elite cyclists and swimmers that found the paradox of low bone density in these athletes. At the time of these studies it seemed obvious, if you want to study the effects of cycling on bone density, then you might as well study professional cyclists, rather than recreational ones. To their great surprise, it was found that the professional cyclists had low bone density as compared to recreational cyclist and sedentary people.

The hypothesis, to explain this unexpected finding, was that bones need the stress of gravity bearing down upon them during exercise in order to stimulate bone strengthening. This view was supported by studies of bone density in astronauts. "Fair enough", you may think, but there was one major oversight with these studies.

The researchers failed to take account of the widespread legitimate and illegitimate use of steroids, including inhaled asthma medication.

Asthma medication is in widespread use among these athletes, whether they are truly asthmatic or not. These drugs are beneficial for performance and recovery, so many athletes wising to gain the competitive edge, or just trying to keep up with the competition who are abusing steroids, resort to steroids, either illegally, or by getting a questionable medical exemption for their use.

Much of the steroid use by these athletes may never be admitted to, even if the researchers thought to ask, and therefore this is one most important factor that was overlooked by osteoporosis researchers. Long term use of these drugs drains the body and bones of calcium which no amount of beneficial exercise can ever compensate for.

The researchers also failed to consider the consequences of prolonged stress and exhaustion as well as the finer details of diet (more about these later).

Asthma drugs, steroids and the epidemic of osteoporosis and arthritis

The widespread prescribing of steroids, particularly for asthma, is one explanation for why we have a growing epidemic of osteoporosis and arthritis in the general population some 20-30 years after these drugs came into widespread use. In my opinion most of this prescribing of steroids as being excessive and often irresponsible. The majority of asthma cases can be successfully remedied by non-drugs methods, including teaching a person how to breathe in a healthy way.

The tsunami wave of bone diseases that are hitting us today, along with companion diseases such as hypothyroidism, anxiety, depression, "brain fog", adrenal fatigue, gall bladder disease, bowell disease, cardiovascular disease (arteriosclerosis), most autoimmune diseases and chronic fatigue, coincides as the first generation of medicated asthmatics from the '70's and 80's hit middle age. All steroids, including Prednisone and the drugs group of antihistamines, have similar effects of draining the body of calcium. Similar patterns exist with other meds, such as those commonly prescribed for high blood pressure and depression. Please refer here for more about steroids, asthma and osteoporosis.

Chronic stress and bone loss

When a person is stressed, the adrenal glands respond by injecting a squirt of multiple stress hormones, including cortisol, into the circulation. This initiates the "Fight or Flight Response", or "General Adaptation Syndrome" model, as first described by Dr Hans Selye in the 1950's when he conducted experiments on laboratory animals. The dear Dr Selye tortured the animals daily by administering progressively stronger electric shocks, while monitoring their behavioural and physiological responses, all of which were ultimately negative to eventually being deadly!

Please take a few minutes to watch this short lesson that describes Dr Selye's general adaptation syndrome model

Endurance training for many hours, day after day, is frankly too stressful for any creature, including Humans, to handle, stimulating either chronic elevated levels of cortisol, or frequent periods of elevated cortisol followed by long periods of low cortisol, or chronically low levels (the latter two being known as the "Tired Athlete"). This condition is best referred as "adrenal fatigue" a term first described by Dr James Wilson. You can learn more about adrenal fatigue at this excellent website.

The two images below, show a laboratory test that confirms this person has "adrenal fatigue". The readings show normal cortisol levels in the morning. However, as the day progresses, the subject is unable to maintain anything near adequate cortisol levels and is consequently feeling dead tired by mid afternoon. This is the profile one typically sees in burned out athletes who suffer recurrent injuries, who seem to catch every illness, who heal slowly and poorly and who may present with thyroid and other hormone related issues. The lowest testosterone levels I have ever seen in males have been in exhausted triathlete and Iron Man athletes.

Adrenocortex Stress Profile

Cortisol Values

Cortisol (cortisone) is, of course, the original steroid, produced by the cortex of the adrenal glands, is how pharmaceutical versions, such as Prednisone and Fludrocortisone, get their names. Cortisol is necessary for the regulation of inflammation and aiding healing, but it is not healthy at all, if constantly elevated, or wildly fluctuating from high to low. As with any steroid hormone, when in excess, cortisone drains calcium and other minerals from the bones, hence the link between chronic stress and bone loss.

Elevated cortisol, or big daily spikes may explain the low bone density seen in over trained and exhausted athletes.

Of course, there are additional factors, such as, poor body mechanics. It usually turns out there is a poor diet, including the consumption of acidic sports and energy drinks (more about these later), most often empty calories and not much else. As many as 90% of New Zealanders have low vitamin D levels. There may even be the presence of heavy metals such as lead and arsenic which eat away bone and cartilage. With any, or all of these going on, there will be progressive bone loss as the months turn into years.

Image: Fit Kiwi furiously preparing for the Round Taupo Cycle Race

Chronic, exhausting exercise and bone loss

Exercise produces acidic byproducts. This is normal and the body has effective mechanism to maintain near perfect body PH at a slightly alkaline PH 7.4. The principal mechanism for this is the shifting of alkaline calcium between the bones and the soft tissues, including the circulation. So, during any form of intense exercise, when there is the production of acidic byproducts, such as lactic acid, calcium is temporarily shifted from the bones into the circulation. This is fine, so long as it is balanced by long periods during which the process is in the reverse direction and calcium shifts from soft tissues to bone.

This may explain, in part, why we see bone mineral loss in chronic long distance athletes and not in athletes who do their exercise in short bursts of intensity with relatively long periods of rest between workouts.

Vitamin D deficiency in athletes

Its harder to get a vitamin D blood test via your doctor nowadays. I had the benefit of reviewing many and continue to do so. We know that low vitamin D levels contribute to many diseases, including osteoporosis and related conditions such as hypothyroidism.

One assumes that athletes, such as runners and cyclists will have high levels of vitamin D, since they are exercising in the sun most days. This is not true. My experience is that most athletes, including runners and cyclists can have very low levels. How can this be?

Most athletes train at the beginning and ends of the day, times when solar UV is very low. In addition, they cover up to keep warm since these are the colder times of day. If the sun is out, then they will slop on the sunscreen. I also suspect that athletes who train very hard have higher requirements for vitamin D, as is the case for all other nutrients.

Hypothyroidism and bone loss

The thyroid gland and the parathyroid gland strike a delicate balance that regulates the shift of calcium between the bones and the soft tissues, including circulation. If the thyroid is weak and damaged then the parathyroid gland becomes dominant relative to the thyroid. Other than fatigue, weight gain, depression and brain fog, there is also the subtle loss of calcium from the bones and its deposition in soft tissues. This may partly explain why dry and brittle (chalky) hair, skin (dermatitis) and nails and fibromyalgia are very closely associated with thyroid problems.

The medical solution to parathyroid dominance is to remove the parathyroid which is a really stupid measure because it commits the patient to a life-long dependence on hormone therapy that gradually loses effectiveness, while bone loss continues. Surely, the better move is to heal the thyroid and adrenal glands? (the adrenals have a profound effect in the thyroid and vice-versa).

Image: progressive loss of bone, often associated with thyroid issues, leading to the gradual collapse of the spine, particularly affecting the thoracic region

Inflammation and the bone connection

Inflammation is an essential survival mechanism. Without it we get sick and die. Inflammation is our body fighting infection. It musters the healing processes, after infection and trauma. When it is at work in the body, it is not unlike a very busy work site. This frenetic activity explains the heat and swelling.

Learn more about inflammation and healing and also why you are advised to avoid anti-inflammatory drugs by reading this article about inflammation.

Inflammation is regulated by the adrenal glands that squirt out nano-levels of signalling steroidal hormones, principally cortisol. Cortisol is kind of like the Senior Building Site Supervisor. When it does its job right, wonderfully orchestrated processes of healing are undertaken by millions of furiously busy artisans, each assigned with their special roles. If adrenal function is dysfunctional, there is work site chaos of the First Order. This chaos is experienced as chronic and out of control inflammation and poor healing. If cortisol is very low, or fluctuating wildly, the person may also suffer allergies such as, asthma, hives, Lupus and food sensitivities.

Inflammation that is out of control is acid-forming in the body which leads to the shifting of calcium from the bones into the soft tissues to neutralise the acidity. We want calcium and other minerals moving into the bones - not going the other way!

Incidentally, chronic inflammation explains, in part, the development of tiny shards of calcium in the soft tissues, such as seen in inflamed breast tissue (ductile carcinoma), tendons and joints (bone spurs).

As an aside: Is your bra killing you?

Image: Thermogram of upper back showing mild inflammation above bra line

Image: upper back. Chronic inflammation associated with wearing a bra. The bra interferes with lymph flow towards the lymph nodes in the armpits.

Image: Finding breast inflammation without resorting to cancer-causing xrays - Breast Thermogram showing inflammation "hot spots" before and after nutritional therapies.

How inflammation and bone loss appear on the InterClinical Tissue Mineral Analysis (HTMA)

There are patterns that appear on the HTMA that are consistent with inflammation and bone loss. It is essential that we know which pattern a person falls into because the pattern determines if they need more dietary calcium, or less. The following are examples of each pattern.

Please take a few minutes, right now, to read this article "More about the Calcium Lie".

The first image below is the HTMA of an exhausted former champion middle distance runner. The pattern accurately reflects the exhaustion being experienced. Incidentally, the "Fast 4" metabolism is based on Dr Selye's experiments. "Fast 4" was the end stage of exhaustion for his tortured lab animals, the next stage being sudden death.

The low everything, including calcium, means there is insufficient of just about anything for building and sustaining strong bones, or anything else for that matter. Low sodium and potassium are associated with adrenal exhaustion and, therefore, low cortisol and other hormones, including testosterone.

This former athletes needs a long holiday with many months of nutrient-dense food, trace elements, including supplementary calcium and various other actions, including adrenal support. He also needs assistance with ridding his body of mercury and lead.

The next screen shot below is of myself while in the depths of metabolic exhaustion, a time in my life when my heart was playing up and anything other than mild exercise was barely possible. Brain fog was thick as pea soup and I had little to no tolerance for any kind of stress. "Slow 4" is not quite as tortured or dire as "Fast 4" but still of considerable concern. Note the elevated sodium and potassium which is indicative of adrenal exhaustion, similar to what is seen with low sodium and potassium (the adrenals regulate tissue sodium and potassium).

This is the pattern consistent with the shifting of calcium and other nutrients from bones into the soft tissues. It was remarkably consistent with health issues being suffered at the time, including brain fog, constant heart palpitations, high blood pressure, bladder urgency and joint cartilage problems. Not good!

What was needed was adrenal support, along with supplementary magnesium and a nutrient-dense diet; but one that is low in calcium and a very long holiday on a tropical island resort!

The screen shot below is from a few years later. This shows an improvement in the calcium/magnesium/potassium ratios, indicating the shift of calcium from the soft tissues into the bones. Supporting this has been a gain of about 200 grams of estimated bone mass by way of bio-electric impedance analysis (BIA). There is also an improvement in tissue levels of sodium and potassium (an indicator of adrenal health).

This improvement in general health is reflected in rather spectacular gains in cardiovascular performance, strength and endurance, the clearing of brain fog and improvements in health in general. These gains have been such that I have not been defeated by any mountain or cyclocross cyclist in the 60+ age group since turning 60 three years ago and I hold the age group records for every race entered in New Zealand and Australia. Winning margins have been from 20-50%.

Note that metabolic type has improved to a very healthy "Slow 1".

As an aside, the increase in mercury and beryllium may be due to the up-regulation of a once exhausted metabolism that powers the process of eliminating these toxic elements. Hair is an excretory pathway for these toxins, hence the elevation of these elements on the hair test.

How to build strong bones

First points: There are no single solutions and no one size fits all solution. The best solution is multi factor and individually tailored. What is good for your bones is good for your health in general and vice-versa.

Please read this article about the Calcium Lie if you have not already. It explains why building bone is far more complex than just adding more calcium into the diet and why more calcium may actually accelerate bone weakening in as many as 80% of the population.

In no particular order, here are some recommendations that everyone can apply with benefit for their bones:

  1. Take out the guessing about what you need to do nutritionally by completing a hair tissue mineral analysis complete with a consultation (not one of those dodgy "hair follicle" tests that are then explained by a shop assistant please!). Use a reputable lab and a health professional with years of training. For beginners, you need to know if you require more calcium, or less - this is a crucial starting point. We can also work out, from this test, if you need a little vitamin D or not, your adrenal, thyroid and liver health, what other trace nutrients that may need attention, the presence of toxic elements, such as lead, and if there are any chronic, undisclosed infections deep in your body (common). This single test yields a wealth of helpful information.

  2. Set yourself up to monitor bone mineral density using safe and healthy methods. I have had thousands of people undertake thousands of bioelectric impedence analysis measures (BIA for short) that include a reliable and repeatable estimate of bone mass. This measure is obtained by passing a very weak electric current through the body and interpreting the way various tissues, such as muscle, fat, bone and water alter the electric current. I like it because the technology is as cheap and convenient as a set of special bathroom scales and safe. Unless you really must have them, please avoid body scanning systems that use cancer-causing xrays, such as the Dexa Scan. They tell you scarcely more of value than BIA about your bone mineral, other than, perhaps, where your bones may be weakest. Because I have done so many BIA readings, including many repeats on the same subjects, I have a very good idea of what are good and not-so-good readings for people from all walks of life. More importantly, the BIA can be repeated weekly in your home to monitor the slightest of improvements in skeletal health, including muscle development and, therefore, the effectiveness of our interventions. If you are going to purchase a BIA body composition analyser for your home, I want you get a Salter Max Body Analyser Scale 9179. When you have readings from this exact machine, I can help you interpret them and provide you with useful advice and guidance. If you use a different brand or model the readings do vary from the thousands of comparable records I have on hand, making it more difficult to give good advice.

  3. Find healthy alternatives to medications that may have been prescribed for ill health reasons. There are usually healthy alternatives that can replace the meds, or, at the least, reduce the doses. Reducing meds is a sensitive matter and must be done under professional supervision.

  4. Get a better balance between stress, including exercise, rest and relaxation. In most cases, this means reducing the duration of workouts, more rest between and generally making the point of seeking out enjoyment, as opposed to workouts being mindless and stressful grinds!

  5. Have a diet that is not pro-inflammatory. The modern Western diet drives systemic inflammation. We have to get back to eating the way our ancestors used to before we were swamped by heavily processed foods, factory farming, colourings, flavourings, preservatives and untold amounts of sugar. While Paleo eating is a good start, let's champion what is better described as "Traditional Foods" as promoted by the Weston Price Foundation, an organisation that has surprisingly close ties with New Zealand (The Foundation's CEO is married to a retired Southland farmer). If, for example, you are of Samoan heritage, why not have a go at replicating the foods your grandparents consumed prior to the flour, sugar, the tuck shop and the KFC taking over the islands (taro, bread fruit, fish, coconut, banana etc)? If your family roots are from Central Europe, that may mean favouring seasonal fruits and vegetables, fermented foods, organ meat and bone broths. As a rule of thumb, a low inflammation diet means avoiding foods that are heavily processed and which are wrapped in packaging with lots of food code numbering. Avoid sugar and processed grains, heat processed fats and oils such as margarine. Eat meat and eggs from creatures that were not stressed and which have been fed the foods that they are supposed to eat (cows should be eating grass - not grain). New Zealand beef and lamb are good starting points for meat. It means eating lots of fresh, bright and dark coloured fruits, berries and vegetables, as well as bright coloured spices such as turmeric and paprika. The hair tissue mineral analysis helps determine which foods best suit your metabolism.

  6. Reduce or avoid acidic soft drinks, energy drinks and sports drinks (including the ones that your sporting heroes supposedly drink). Phosphoric acid is added to many of these drinks to give a "tang" to their taste. Phosphoric acid must be buffered and the body does this by shifting calcium out of bones into the soft tissues and circulation.

  7. Sports such as running and cycling may not strengthen the upper body, including the important thoracic vertebrae. It is important to do a little supplementary exercise, if running or cycling are your main exercise form. The best and most convenient exercise for overall strength and total body bone strength is the "Lift and Press". Perform several repetitions of this exercise daily, as demonstrated by the very handsome chap in the images below. You need a weight that can be smoothly lifted above your head about a dozen times in a go (I have a set of barbell weights in the living room and do ten lift and press repetitions every morning, then continue on my way to the kitchen for a well-earned feed).

Nutrients you can take to help a stress fracture heal

Important: It is assumed that you are under the care of a medical practitioner, so what is recommended here is intended to be supportive - not a replacement for the medical care, including advice regarding rest, immobilisation and a guided resumption of activity. The following is in addition to the nutrition advice earlier in this article.

This is the water soluble form of calcium which concentrates at the point of injury/healing. It is from this form of calcium, along with many other nutrients, that hard calcium phosphate dibasic and calcium phosphate tribasic are manufactured from by amazing little bone cells call "osteoblasts" to form healthy bone.

Salts that contain 50 or more minerals, of which sodium chloride is the main one. Common forms are Himalayan and Celtic salt.

These substances have unique bone-building properties, as well as many other health benefits.

About 2,000 iu per day of natural vitamin D with a fresh fish oil derived from deep-dwelling, frigid waters fish (vitamin D and tocotrienols are fat soluble, so best taken with fats and oils). Please do not have mega doses of vitamin D, usually prescribed to be taken once a week or once a month. Your body simply does not cope with this sort of periodic nutritional flooding. The best nutrition is "small amounts often".

A fish oil that is derived from fish that inhabit deep, frigid waters contains fatty acids and other substances that reduce inflammation and promotes healing. Among many things, fish oils enhance the utilisation of fat soluble vitamins (A, D, E and K) and the production of hormones. These are all essential for bone healing.

If you were to take just one nutraceutical for bone repair and bone health, this is the one.

Get to the Root Cause of stress fractures

Get a good coach before resuming training

Stress fractures happen because the rate of wear is exceeding the capacity for repair and compensatory strengthening. I am reminded of my sister, Lorraine, who was internationally ranked as a middle and long distance runner for 28 years. She ran in excess of 100 miles a week on occasions. Her shoes of the 1970's and 80's had little in the way of cushioning and support as compared to the modern shoe. Despite this, she never suffered a stress fracture.

Lorraine Moller 4 times Olympian

I attribute Lorraine's stress fracture free career to:

  • Good nutrition along the lines of what is recommended in this article, along with some dietary supplements, specific for individual needs and

  • Good coaching, including attention to nurturing perfect running form and efficiency.

Good coaches are as rare as hen's teeth. A good place to begin your search for a coach is the Lydiard Foundation which has a register of Lydiard Certified Coaches worldwide, including sports other than running (Lorraine is the president of this coaching foundation).

Complete a Comprehensive InterClinical Laboratories Hair Tissue Mineral Analysis

As recommended earlier, this forensic test helps you identify all of the possible nutritional and physiological factors that may be contributing to weak bones and slow healing. It often throws up surprises, such as lead poisoning from the most unusual of sources, such as lead-based hair dye, bathing in an enamel bathtub or eating a duck (heavy metals such as lead damage tissues like bone and cartilage, leading to rapid onset of osteoporosis and arthritis).

Image above: Lead poisoning of a once fit man from eating a duck with lead shot contamination of the flesh.

While it does take 3-4 weeks for the report to come back from the lab, by which time the current stress fracture should be well on the way to healing, the report will help us ensure you do not suffer any recurrences.


As with most health issues, there are no single solutions to preventing stress fractures. Singular solutions will inevitably produce disappointing outcomes over the long term and may ultimately lead to the premature retirement of the athlete from active participation.

Prevention and recovery is best achieved by identifying the root causes, of which there may be many, and then systematically eliminating, or reducing each one.

Further reading

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