Strengthen your bones

Trail Running (UK) - - Contents - Words Ruth Jones

What makes bones stronger and more durable? Al­though bone strength is ge­net­i­cally de­ter­mined, there are cer­tainly strate­gies that can im­prove it, par­tic­u­larly when it comes to phys­i­cal ac­tiv­ity and nu­tri­tion.

Paul Hough, an ex­pert in ex­er­cise phys­i­ol­ogy, ex­plains: “Weight-bear­ing ac­tiv­i­ties, such as run­ning, en­cour­age a process called bone re­mod­elling, which in­creases bone min­eral den­sity (BMD) and re­duces the risk of frac­tures. How­ever, not all forms of phys­i­cal ac­tiv­ity im­prove BMD. For ex­am­ple, cy­cling – a non-weight-bear­ing sport – is in­ef­fec­tive in in­creas­ing BMD. In­deed, BMD has been re­ported to be lower in cy­clists com­pared to in­di­vid­u­als who en­gage in weight-bear­ing ac­tiv­i­ties.”

Paul sug­gests that adding strength train­ing to your run­ning pro­gramme is key to in­creas­ing your BMD. “Al­though typ­i­cally as­so­ci­ated with boost­ing mus­cle strength, re­sis­tance train­ing is an ex­cel­lent method of im­prov­ing BMD,” he adds. “That’s why I rec­om­mend strength train­ing for en­durance ath­letes.”

Nu­tri­tion should be an equally high pri­or­ity for any­one se­ri­ous about look­ing after their bone

health, adds Paul. “What we eat strongly influences bone strength, in par­tic­u­lar en­ergy (calo­rie) in­take in re­la­tion to en­ergy ex­pen­di­ture. En­ergy avail­abil­ity (EA) is the amount of en­ergy that is avail­able to the body to fuel nor­mal phys­i­o­log­i­cal func­tions after sub­tract­ing the en­ergy ex­pended through ex­er­cise. In essence, this is how much en­ergy is left for the body after phys­i­cal ac­tiv­ity. EA can be re­duced due to a low-calo­rie in­take, in­creased en­ergy ex­pen­di­ture, or a com­bi­na­tion of both. A chronic low EA (inadequate en­ergy in­take) can re­duce re­pro­duc­tive hor­mones and growth fac­tors, which can lower BMD and in­crease the risk of frac­tures.” And what is in your diet is just as im­por­tant as how many calo­ries you con­sume.

“The com­po­si­tion of a diet greatly influences bone strength,” Paul ex­plains. “The diet should in­clude food and drink rich in cal­cium, as bone min­eral con­tent is largely formed from cal­cium and phos­pho­rus. Other vi­ta­mins and min­er­als are also re­quired for nor­mal bone me­tab­o­lism; for ex­am­ple, vi­ta­min D and K, mag­ne­sium, zinc and flu­o­ride. There­fore, it is es­sen­tial to con­sume foods high in pro­tein and a va­ri­ety of veg­eta­bles, fruits, seeds and nuts.”

Sun­shine should also play a key role in main­tain­ing healthy bones, says Paul: “The body pro­duces vi­ta­min D when the skin is ex­posed to sun. So spend plenty of time out in the sun­shine.”

How run­ning af­fects bones

The con­tin­ual forces on the body’s skele­ton caused by run­ning sig­nif­i­cantly in­creases bone mass, as Paul ex­plains: “Run­ning can im­prove BMD due to the repet­i­tive forces ap­plied to the bones dur­ing run­ning. How­ever, these forces are low com­pared to other sports such as foot­ball and ten­nis. More­over, the load ap­plied to the bones dur­ing run­ning pri­mar­ily oc­curs in a sin­gle plane at a con­stant rate (around 80 to 110 strides per minute in most run­ners). Stud­ies in mice have demon­strated that high-im­pact loads ap­plied in dif­fer­ent di­rec­tions are more ef­fec­tive at in­creas­ing BMD. This may be why team sport ath­letes and ten­nis play­ers have a higher BMD than en­durance ath­letes.” Paul em­pha­sises the im­por­tance of a well­bal­anced diet when run­ning reg­u­larly. He ex­plains: “In some in­di­vid­u­als, run­ning can ac­tu­ally have the op­po­site ef­fect and re­duce BMD. For ex­am­ple, peo­ple at risk of chron­i­cally low EA, such as young fe­males and ul­tra-en­durance ath­letes. There­fore, it is es­sen­tial for these in­di­vid­u­als to fo­cus on con­sum­ing enough calo­ries, vi­ta­mins and min­er­als within their di­ets. It is also sen­si­ble to in­crease mileage grad­u­ally and per­form re­sis­tance train­ing ex­er­cises.” Bone min­eral den­sity and strength peak in the late 20s, but mus­cle and bone mass be­gin to de­cline after our mid-30s, as Paul ex­plains: “In the decade fol­low­ing

‘Low en­ergy in­take can re­duce re­pro­duc­tive hor­mones and growth fac­tors, and in­crease the risk of frac­tures.’

our mid-20s, the re­duc­tion of mus­cle and bone mass leads to a de­crease in strength of both tis­sues. A sub­stan­tial loss of bone can lead to os­teo­poro­sis, a skele­tal dis­ease char­ac­terised by low bone mass and struc­tural weak­en­ing of the bone; this re­duces bone strength and in­creases sus­cep­ti­bil­ity to frac­ture. Con­se­quently, the risk of stress frac­tures in­creases amongst older run­ners, par­tic­u­larly if en­ergy in­take is inadequate and weekly mileage is rapidly in­creased. Diet, re­sis­tance train­ing and sen­si­ble pro­gramme de­sign be­come in­creas­ingly im­por­tant to se­nior run­ners.”

Vi­ta­min-packed nuts and seeds can bol­ster bone health

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