iamgeekfit

In the past decade, research has shown in new ways what traditional medicine has suggested for millenia: all the systems in our bodies are connected. More particularly, our bodies, in particular the tissue in our bodies, are responding and adapting and REBUILDING all the time in response to a variety of inputs. It's amazing how quickly our bodies do respond to input change. In the health and fitness domain, we see these changes mainly in terms of body composition: adipose tissue shrinks; muscle fibers and connective tissue enlarge, appearing more taut or larger. The success of 12 week programs shows just how much physical change can happen within a mere 90 days.

Other changes in tissue are more experiental than visual: because of adaptations in our lungs, heart and muscle tissues with exercise, we feel like we have more energy; we may eat more but we're not gaining fat (blessed state). We can work longer or harder without being fatigued or getting out of breath. In some cases, aches and pains seem to diminish or disappear.

One tissue change that we are less aware of but that is perhaps one of the most remarkable is the adaptation of bone. Bone is very much living tissue, constantly responding to our bodies' use - or lack of use - of the 600 or so bones in our skeletal system. Blood vessels run throughout bones constantly taking away bone into the blood stream, and bringing in new nutrients to rebuild bone. Bone itself is made up from collagen, calcium salts, phosphates, magnesium, even protein plays a role in the brilliant, constant reengineering of our gears. The purpose of this post, though, is to consider not so much how bone growth happens from converting collagen tissue in the foetus to fully osified bones in an adult, but recent research around continuous bone adaptation, and the role our actions literally play in bone health.

Most of us have an understanding that healthy bones are "strong" and that not healthy bones are "fragile" - brittle, subject to breaks. And to state even more of the obvious, a broken bone is a problem because of the role of bones in our body: they support the movement of our bodies in space, and let us also move upon the world around us. The bones of our hands, feet, spine, arms are examples of where we see such action. Our bones also protect vulnerable organs, like the ribs around our innards, and the skull around our brain (the spine also serves a protective function, too, acting in part as the pipe through which the spinal cord runs). If a bone is broken or damaged either mobility or protective capacity or both can be compromised. So, having good strong bones, resistant to fracture, for as long in our lives as possible is a Good Idea for enduring health.

While many of us have also been raised hearing how important diet is for such good bone health - encouraging us to eat foods rich in calcium, vitamin D and related - what is less well known outside the fitness community is how critical muscle work is for bone health and strength. Indeed, while 3-10% of bone health is down to nutrition, over 44% of bone building is down to load (use/disuse)(Kirattli 96). We're going to look some of the very recent work in the past decade that has shown what's going on with what's called bone remodelling, and how to use that information to do the best for our bones. HM Frost describes nutrition for bones as fuel for the car: it's needed, but doesn't drive the car. We need action to drive bone health.

This discussion about bone's adaptation to use really begins with what's become known as Wolff's Law (1892):

Every change in the form and function of bone or of their function alone is followed by certain definite changes in their internal architecture, and equally definite alteration in their external conformation, in accordance with mathematical laws.

What this means is that somehow, load or action on a bone effects it. It is only in the past 25 years that this assertion has been shown to operate profoundly, and only in the past ten years a more profound understanding of how that operation works. These efforts to explain Wolf's law are frequently described as Utah paradigm (1992 and on). In this HM Frost proposes the Mechanostat as a refinement of Woolf's law that says the big deal on bone remodelling is the elastic forces exerted on bones. Related work has been showing to what degree Wolff's proposition holds. Much of the following is taken

Bone Modelling - Modelling is a cool concept: in bones it refers to absorption of some bone materials and depositing of new material within the bone matrix. A gerat description of this process is in the Essentials of Strength and Conditioning text book. The big deal is that bone lives. it's ALIVE. and that it responds to need and demand and amazingly RESHAPES to support that demand. This modelling, apparently always makes bones stronger.

Cells know as Basic Multicellular units are involved in this constant dance of reabsorbing and then rebuidling bone (more particularly osteoblasts build up bone; osteoclasts remove it). Hence when astraunats spend time in orbit, their bone mass is less than when they left because the demand on the bone, and BMU's has been less than normal, so bone "building" has been to support efficiency for that system. Wild! This particular kind of bone "loss" is referred to often as "osteopenia" We also need to note that this kind of bone reforming only happens in bone close to marrow (so your skull won't get thinner in space).

Bones and their Incredible Strength

Load Bearing Bones (LBB) like our long bones in the legs and arms (and spine) are largely hollow and light relative to the forces they can support. Their strength apparently comes largely from the architecture within the bones

- the extremely light connections of bone matrix material of the travecular/cancellous bone within the walls/shell of the outer "compact" bone. Indeed, when bones are measured as "thicker" after exercise training, for instance, what apparently is really happening is less that the compact bone is becoming thicker, but that that outer shell is rather being pushed out as more inner architecture is added.

It's the amazing lattice work of collagen fibers, and progressively ossified fibers that contribute significantly to the bones' ability to respond to stresses put upon them. To quote from Wikipedia's page on mechanostat measures: "The fracture load for axial forces of the Tibia for example is about 50 to 60 times the body weight. The fracture load for forces perpendicular to the axial direction is about 10 times lower." Note: that's 50-60 and 5-6 times BODYWEIGHT - not the bone's own weight. That's amazing!

Use It or Lose It
Bones are ready to deform and bend to support loads up to a particular threshold - when that threshold is broached, bone remodeling kicks in - slowly - to help bones adapt to the new loads (Bone rebuilding lags behind muscle building).

Similarly, however, not taxing our bones to at least near their threshold sends bone remodellers in again -but this time in the osteopenia direction; that is, taking bone away and not replacing it with the same amount removed. How exactly this signalling works, alas, is still very much leading edge research, so we don't know *exactly* how to tune our efforts to flip the switches to say "build more bone" - not exactly. Indeed, a review of studies of children and early adolescents to look at various protocols of weight bearing effort to tune optimal bone growth states we still have a lot to learn:

CONCLUSIONS: Although weight-bearing exercise appears to enhance bone mineral accrual in children, particularly during early puberty; it remains unclear as to what constitutes the optimal exercise programme. Many studies to date have a high risk for bias and only a few have a low risk. Major limitations concerned selection procedures, compliance rates and control of variables. More well designed and controlled investigations are needed. Furthermore, the specific exercise intervention that will provide the optimal stimulus for peak bone mineral accretion is unclear. Future quantitative, dose-response studies using larger sample sizes and interventions that vary in GRF and frequency may characterise the most and least effective exercise programmes for bone mineral accrual in this population. In addition, the measurement of bone quality parameters and volumetric BMD would provide a greater insight into the mechanisms implicated in the adaptation of bone to exercise.

Despite some lack of exact specifics, apparently over the past decade alone much has been learned about what goes into enhancing the efforts to grow strong bones. Here's a cool fact that Frost (2001) reports from research in the late 90's: that our muscles create the larges voluntary loads on bones. As Fronst summarizes it:

muscle forces -> bones -> strains -> control of modelling and remodelling (Frost, 402)

OBESITY: It may need to be noted, as Frost's summary also shows, that despite the fact that obese people are heavier and so put extra load on their bones beyond that of healthy weighted people, they also, typically, load their bones (move) a whole lot less than their healthy peers. Thus, bone removal (the astronaut effect, one might say) kicks in, and their bones become even less able to handle their frame.

Use it or Lose it and some gender bits
Apparently we are not particularly mechanically efficient in our joint design, and so it's actually our muscles that put the greatest loads on our bones, and thus it's our own frame's work that causes the main bone adaptations. This muscle to bone connection is one reason, it's been suggested, that researchers have shown that men who usually have stronger muscles than women are going to have stronger, more mass-y bones. This is not to say that women's bones are less healthy than men's, but that relative strength is different because in large part of this muscle-bone interaction. All the more reason for women to get into resistance training, but we'll come onto that. Also important to note is that men and women lose bone mass at about the same rate until, for women, menopause kicks in. On average, post-menopausal women start to have higher bone loss rates than men, but research is showing that exercise has a significant impact on slowing this rate of bone loss, and actually building it.

One very interesting result shows as well that Resistance Training alone in early post-menopausal women in a year long study showed bone mass density improvement and more:

In conclusion, RT alone was as effective as HRT in preventing bone loss at the spine and was more effective than HRT alone in attenuating bone loss at the spine. Moreover, there was no additional benefit in combining HRT with RT for preventing bone loss at the spine in this group of early postmenopausal women.

This is an exciting finding. Once again, we have a result that says healthy lifestyle helps keep one healthy for the long haul, and better in this case than drug therapy alternatives. Further research comparison reviews are here in a 2006 overview.

For older men, some work has been looking at the use of creatine WITH resistance training to reduce bone loss - creatine's effect is not conclusive, but in 12 weeks, the benefit of resistance training clearly is.

Getting a Break.
Just before we start looking for workouts that tax our bones to the breaking point in an effort to make them stronger, we need to note another part of the Utah Paradigm: there IS such a thing as going too far, something called microscopic fatigue damage in bone and bones (MDx). There is an operational threshold after which, fractures can strat to accumulate. This can lead to increased big fractures. So while small strains near threshold have a growth effect, going overboard can have the opposite effect - and by multiple hundreds of times.

Big-ing Up the Bones Training
Again, while apparently exactly what levels of effort turn on bone remodelling - and what triggers more oteopenia (bone loss) - studies have shown some pretty consistent findings in exercise types: sudden axial loading. And while walking is good for the heart and other health effects, it apparently doesn't do much for BMD - in post-menopausal women at least. Another study says that "low volume/high intensity" exercise works a treat for maintaining BMD - for early pm gals "spine, hip and calcaneus [heel], but not at the forearm"..(alas i can't get at the whole article to see what that "exercise" is). Likewise, it seems that, similar to the martial arts effects, we can tune for "site specific" exercise regimens to help enhance bone density at vulnerable sites (should you wish to do that).

As recently as 1994, research showed two exercises that seemed to contribute directly to improving bone mineral density: squash and resistance training. Frost's Utah Paradigm review suggests resistance training and soccer. Martial arts also shows bone density growth but mainly at the point of impact, suggesting again that bone responds to load/impact in a rather compelling way.

But especially thinking about elderly, exactly what the balance is between load and impact is not known. It's to our advantage to figure that out - or prevent the need to do so. A LOT of work is going on to understand this tuning:

One recent intense two year study that looked at yup, post menopasal women considered strength training vs power training. Based on what we know from other research about the kinds of sudden impacts that seem to create the most response, it may come as no surprise that the power training group took home the increased BMD prize.

CONCLUSION: The results show that PT may be superior for maintaining BMD in postmenopausal women. Furthermore, PT was safe as it did not lead to increased injury or pain.

While it's inappropriate to generalize a program from a single study, the results here again seem reinforced by other findings: explosive loading has a greater impact than slower loading. At some point we'll look at examples of explosive lifting but in the interim, may i say "kettlebells" and dynamic movements like the clean and jerk or snatch with same?

If one asks the question, what's better for BMD: lots of reps with lighter loads or fewer reps with more load? We only have the rat world at present to site for a finding, but we might be able to predict the result: fewer reps with heavier load elicited "significant" BMD elevation.

So, even if we may be reluctant to take all this work of a particular population and generalize it for younger adults of both genders, it seems that we can say from those other studies of younger athletes there is a common thread: load, and sudden load at that - has benefit. And while most emphasis has been on actually pumping iron, sports that have sudden stop and start (squash and soccer) have shown excellent effects, too.

So what to do?
So, lift, lift fast, or move, move fast; stop and start; jump occasionally (even perhaps hit something)seem generally to be the broad outlines of a BMD protecting/inducing program. But the biggest council and the best seems to be to start soon, start early, and make resistance work - especially of the fast variety - a lifestyle action BEFORE adult development peeking.

A few additional notes are worth adding:

Notes of Runners - Go Heavy! Lift Stuff
Resistance training has been part of sprinters' regimens since Ben Johnson in the mid 80's. In endurance running, most of the research has shown that strength training has great benefits for endurance work. BUT new research has shown that resistance training may be *crucial* for endurance athletes to improve what has chronically been shown as low bone mineral density - in both male and female runners. So it seems running is not part of the "stop and start" type exercise that generates the impact necessary for BMD generation

General Prescriptions for the sedentary/elderly: we're walking here?

While lighter efforts like t'ai chi and light walking, and even running seem to have problems generating any benefit for BMD, there is apparently evidence that as long as there is "load bearing" - like walking home or up the stairs with groceries - but that this also needs to be complemented with resistance work:

Two types of exercises are important for building and maintaining bone mass and density: Weight-bearing exercises, in which bones and muscles work against gravity and resistance training that use muscular strength to improve muscle mass and strengthen bone. Exercise can also improve gait, balance, coordination, proprioception, reaction time, and muscle strength, even in very old and frail elderly people. Overall, the evidence strongly suggests that regular physical activity, especially started in childhood and adolescence, is a cheap and safe way of both improving bone strength and reducing the risk to fall.

Other research echoes the above combo approach explaining a bit more of the why of this dual approach:

Weight-bearing physical activity may reduce the risk of osteoporosis in women by augmenting bone mineral during the early adult years and reducing the loss of bone following menopause. High-load activities, such as resistance training, appear to provide the best stimulus for enhancing bone mineral; however, repetitive activities, such as walking, may have a positive impact on bone mineral when performed at higher intensities. Irrespective of changes in bone mineral, physical activities that improve muscular strength, endurance, and balance may reduce fracture risk by reducing the risk of falling.

I Haven't Fallen and i Can Get Up: a mobility aside to Bone Health.

It's important to note then, that, for general well being, as noted at the beginning of this article, our systems are alive and linked. The above research highlights the fact that falls in the elderly, for example, are not just about BMD - reduced BMD is why a fall results in a fracture, but why does that fall happen? The related issues are strength and agility and mobility. These attributes are of benefit for us throughout life. They also seem strongly to follow the use it or lose it qualities of our other physiological systems.

One of the biggest motivations for bone research is the Loss of BMD for post-menopausal women - and the devastating effects of bone fractures in "frail" elderly of both genders. One of my favorite studies in this space is one that shows a blend of approaches in reducing risk of falls in elderly women.

CONCLUSIONS: Strength, balance, agility, and jumping training (especially in combination) prevented functional decline in home-dwelling elderly women. In addition, positive effects seen in the structure of the loaded tibia indicated that exercise may also play a role in preventing bone fragility.

ideas like social confidence and movement confidence are shown as part of the protocol. Rather than focusing on just bone strength, researchers looked at effects of confidence to reduce fear of falling. Agility and mobility is part one's ability to control the range of motion of a joint. The role of mobility, from my reading, is not stressed in BMD research work, but this study raises at least for me, through its consideration of agility, the role of maintaining the best range of motion of our joints for as much and as long as possible.

There's a vicious circle, is there not, of the older we get the less mobile we get. I work with adults in their early 20's who cannot touch their toes. How much further away from our toes do our hands get as we age? We know that dynamic mobility work like ZHealth helps keep joints mobile. I'd hypothesize that as as mobility stays up, one can perform better - more pain free, more range of motion, thus better action on bones. So perhaps a corollary to working bones with resistance training throughout life is also to keep mobility of joints active too.

Summing Up

While studies have mainly focussed on post-menopausal women, bone health - in particular bone mineral density - is a concern for both men and women. The best cure for bone loss is prevention rather than treatment, and the best approach for this prevention of inevitable bone loss is to bank it up with extra BMD work in childhood, youth and young adulthood. The best approach to do this loading is with resistive force work: power training, stop and start sports.

Nutrition is critical for bone building, but will not cause bone building anymore than simply eating protein will cause hypertrophy. While we still don't know what the optimal prescriptions are for optimal bone mineral density building, all the studies looking at this effect show that doing nothing is the worst approach; better to do some load bearing activities - but not over doing it, or one may have the opposite than desired effect with fracturing the bones beyond repair.

Because of the critical effect of bone loss post our alas early peeking in life, it's great to know that we can bank up bone for future benefit by using it regularly and vigerously - at least a few times a week. If you're reading this, you're not too young to start the deposit, no matter what gender. Use it or lose it seems to be increasingly a way of describing our entire physiological system, and that is certainly the case with our locomotive, protective, rather magnificent living skeletal system.

This overview is in no way exhaustive, and i'm sure i've missed stuff; it is meant to be indicative of where research is at with respect to BMD, and how much we still need to learn about program development for bone support, but that overall, starting that work of axial loading sooner and longer rather than later is critical.