Exercise to Improve BoneMineral DensityJoaquin Calatayud, MSc, NSCA-CPT,1Sebastien Borreani, MSc,1Diego Moya, MSc,1Juan C. Colado, PhD,1and N. Travis Triplett, PhD, CSCS*D21Laboratory of Physical Activity and Health, Department of Physical Education and Sports, University of Valencia,Valencia, Spain; and 2Department of Health, Leisure, and Exercise Science, Appalachian State University, Boone,North CarolinaA B S T R A C TEXERCISE IS AN IMPORTANT ELE-MENT OF THE PREVENTION ANDTREATMENT OF OSTEOPOROSIS(OP). DIFFERENT TYPES OF EXER-CISE HAVE POSITIVE EFFECTS INPATIENTS WITH OP. CERTAINLY,WEIGHT-BEARING EXERCISE ANDRESISTANCE TRAINING ARE THEBEST WAY TO IMPROVE BONEMINERAL DENSITY. THIS REVIEWPROVIDES PRACTICAL GUIDE-LINES FOR EXERCISE AND CON-DITIONING SPECIALISTS.INTRODUCTIONOsteoporosis (OP) is a diseasecharacterized by a reductionof the bone mineral density(BMD) and a structural deteriorationof the bone tissue that results in fragilebones, leading to a high fracture risk(26). After the age of 40, BMD declinesprogressively, 0.5% per year or more(23), especially in women (13). By 50years of age, women from developedcountries have a probability of morethan 40% suffering OP fractures and20% suffering a hip fracture (5). Themortality rate after hip fractures in thispopulation is approximately 20% (9). Inaddition to the hip, the other 2 siteswith more fracture incidence are thespine and the wrist (18,26). OP frac-tures are related to excessive mortality,morbidity, chronic pain, reduction inthe quality of life, long-term attention,social and health care costs (28). Thecosts associated with OP during 2005were estimated to be 19 trillion dollarsin the United States, and these costs areexpected to increase to 25.3 trillion dol-lars by 2025 (26). Most of the eco-nomic costs associated with OP arebecause of the treatment of hip frac-tures and the hospitalization neededafter all types of fractures (9).Bone quality is determined by severalfactors such as the bone geometry,cortical thickness and porosity, tra-becular bone morphology, and theintrinsic properties of the bone tissue(18). A low bone mass detected bydensitometry is one of the mostimportant risk factors (18), althoughmost fractures are because of fallsinﬂuenced by deterioration of thevisual function, muscle strength, andbalance (12). Nevertheless, measure-ments of the BMD contribute to theprediction of the risk of fractures (24)and may be an indicator of other prob-lems such as low back pain, which isassociated with reduced lumbar BMDlevels in males (16).There are several methods to deter-mine BMD; however, dual x-rayabsorptiometry (DXA) is the mostcommon method of assessingthe mineral content of the whole skel-eton, as well as of speciﬁc sites, includ-ing those most vulnerable to fracture(41). DXA is regarded as the “goldstandard” because it is the most highlydeveloped technique and the mostthoroughly validated biologically.The term “bone mineral content”describes the amount of mineral inthe speciﬁc bone site scanned, whereasBMD can be derived by dividing thebone mineral content by the area orvolume measured (41). Peripheralquantitative computed tomographyis another technology that showsimprovements when evaluating bonegeometric properties and verifyingbony mass changes in a preciseway (13).Although signiﬁcant effects can beseen after 4–6 months (13), changesin BMD occur very slowly (1). Nev-ertheless, bone adaptation processbegins in early phases of training(29), and rapid changes in bone resorp-tion and bone formation markers maybe tested (41). For this reason, popu-larity of speciﬁc bone biomarkers isgrowing (30) because of the fact thattheir use is less expensive than theconventional densitometric methods(39), and they are an easy, effective,and a noninvasive way to verify theshort-term effects of exercise in bones(40). The principal markers of boneformation are the procollagen pro-peptides of type I collagen (41),the bone isoenzyme of alkaline phos-phatase (41), osteocalcin (41), andtotal alkaline phosphatase (19,41),whereas the most widely used markersof bone resorption are hydroxyproline,pyridinium cross-links, and their pep-tides (41).K E Y W O R D S :osteoporosis; bone mineral density;weight bearing; resistance trainingCopyright Ó National Strength and Conditioning Association Strength and Conditioning Journal | www.nsca-scj.com 1Copyright ª Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
In general, physical inactivity anddecreasing the load on the skeletonresult in a reduction of the BMD(29,45). Postmenopausal ages arerelated to a low level of physical activity(7), and the consequences are a lowstimulation of the bones, a decrease ofthe muscle mass, as well as a decrease instrength, coordination, and balance(30). Thus, the quality of life is nega-tively impacted by lack of physicalactivity (3,6,7,38). Participation in high-impact sports, especially before puberty,is important to maximize the accumula-tion of bone mass and to obtain a greaterbone mass peak independently of sex(15). Strong scientiﬁc evidence existsto support that performing exercise dur-ing childhood is associated with a bettermaintenance of bone mass in advancedage (20,23). In addition, regular exerciseis associated with a lower risk of suffer-ing bone fragility fractures in older peo-ple of both sexes (15).In recent years, different types of exer-cise have been evaluated to improveBMD despite the fact that not all ofthem have shown the same effects(13). It is necessary to take intoaccount the different factors that inﬂu-ence and lead to bone formation. Thecellular mechanisms responsible forthe adaptation of bone are modelingand remodeling. These mechanismsmodify the external size, contours ofbone, and its internal architecturebecause of bone deposition or removalfrom the surface of bone by osteo-blasts and osteoclasts, respectively(34) through osteocytes, which detectmechanical strain and transduce theapplied strain to the aforementionedcells (34,44). However, as osteogene-sis is inﬂuenced by the stress imposedon bone (10), a minimum effectivestrain to induce bone formation mustbe reached (29). Therefore, if mechan-ical load exceeds this threshold, thenosteoblastic activity is induced andthus bone becomes strong to providean adequate support structure (29) inthe speciﬁc area that experienced themechanical strain (15,22,29). Otherdeterminant factors of the results arethe initial BMD of each subject (lowerBMD baseline is related to greater im-provements after the training pro-gram) (13), external factors such asdiet (6,36), systemic factors such ashormones (6,36), as well as age andgenetics (11,36).Not all exercises are effective forincreasing BMD. The National Osteo-porosis Foundation (NOF) distin-guishes between 2 subgroups ofexercises that do not have an effect onthe bones (27). There are exercises with-out impact, like balance or ﬂexibilityexercises, and there are exercises wherethe body weight is not entirely sup-ported (non–weight-bearing exercises,also nonimpact exercises), such ascycling or swimming (15,27). Othermore effective types of exercise includeweight-bearing exercises and resistancetraining (RT).WEIGHT-BEARING EXERCISESWeight bearing is one of the effectiveforms of exercise that lead to mainte-nance or improvements in BMD(13,15,18,23,27,29,31). Based on theNOF deﬁnition, weight-bearing exer-cises include activities that make onemove against gravity while stayingupright (27). These exercises can behigh impact (i.e., jumping) or lowimpact (i.e., walking).Aerobic exercise, especially walking, isthe most common type of exercisebecause of its ease of accomplishmentand safety (13,31). Evidence suggeststhat walking and running have a fewpositive effects on BMD (15). How-ever, different results are found de-pending on the training variablesused in the protocols. For example,more BMD beneﬁts from walking havebeen shown when more intensity ordistance was performed (31). Also, bet-ter results are achieved when high-impact activities are included (13)because high impact seems to bea highly efﬁcient exercise to promoteBMD except in postmenopausalwomen (15). For example, runningand jumping had a signiﬁcant effecton the BMD in 2 sites: the total hipand femur trochanter (18).RESISTANCE TRAININGRT is the other effective type of exercisethat is able to maintain or to improveBMD (13,15,18,23,27,29,31,43). TheNOF considers RT as those activitieswhere one moves the body, a weight,or some other resistance against grav-ity (27). However, in some RT exer-cises, bones and muscles work againstgravity, whereas feet and legs bear thebody’s weight, and thus, these exer-cises may be considered also asweight-bearing exercises (e.g., squatjumps). On the other hand, thoseexercises with different body positionsthat are not performed while stayingupright (e.g., bench press) may beconsidered RT non–weight-bearingexercises.RT has been proven to be a potentstimulus for the formation and mainte-nance of bone mass (13,43). Positiveeffects have been found especially inthe femur neck, the lumbar spine(13,18), and the distal radius (13).Moreover, RT improves muscularstrength that may decrease risk of fallsin older adults (14,31).It seems that the most effective combi-nation of exercises would be to performhigh-impact activities, such as jumps, inaddition to RT (15). Howe et al. (18)found that combination exercises pro-grams, where different types of exercises(i.e., resistance or endurance training)were included, had a signiﬁcant effecton BMD in 3 sites: the femur neck,the spine, and the femur trochanter.WATER-BASED EXERCISEWater-based exercise has shown toprovide many of the same beneﬁts interms of physical ﬁtness as land-basedtraining programs and thus has gainedconsiderable popularity in recent years(8,25). Among the beneﬁts reported insome studies involving water-based ex-ercises are improvements in strength,the ability to perform daily living activ-ities, ﬂexibility, body composition, andcardiorespiratory ﬁtness (8,33,37).Notwithstanding, few studies on theeffectiveness of water-based exerciseon parameters linked to OP and fallrisk, such as balance and functionalExercise to Improve BMDVOLUME 0 | NUMBER 0 | MONTH 20132Copyright ª Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
status, are available. Load on the bonesin water can be achieved through RTand running or jumping in shallowwater. It is necessary to take into con-sideration that greater immersiondepth results in less impact and viceversa. It has been demonstrated thatwater aerobic exercise is able toimprove calcaneus BMD (4). Addition-ally, Rotstein et al. (32) showed that theexperimental group maintained orimproved bone status in spinal verte-brae L2–L4, whereas control groupbone status declined. The training pro-tocol was composed of a combinationof 20 minutes of aerobic training and20 minutes of RT with different exer-cises and devices.Water-based exercise may be a usefuloption or ﬁrst step for people with OPwho have difﬁculty exercising on landbecause of fear of falls, poor balance,and pain, because it is a safe exercise,and postmenopausal women can takeadvantage of the general beneﬁts ofthis type of exercise, although it mightnot be the best way to improve BMD.WHOLE BODY VIBRATIONTRAININGWhole body vibration (WBV) trainingis a new type of intervention that seemsto be more effective than walking andto be similar to RT to improve BMD ofdifferent body sites in postmenopausalwomen (13). More studies are requiredto support similar effects in men (13).WBV has been shown to have a signif-icant effect on BMD in 2 sites: the totalhip and the femur trochanter (18). Nev-ertheless, additional evaluation of thecorrect exercise positions and the suit-able doses of vibration (time, intensity,frequency, and type) is required (13). Inthe same vein, a recent review (42)emphasizes the lack of scientiﬁc evi-dence about the optimal exercise proto-cols of WBV for patients with OP.In summary, reviews and originalinterventions provide clear evidencethat physical activity is able to increaseBMD (13,15,18,21–23,30), strength(21–23) increase muscle mass (22,23),improve balance, and decrease fall risk(2,14,17,22,23,35); each of these factorslead to reduced bone fractures byitself (22).PRACTICAL APPLICATIONSHigh-impact activities must be per-formed during childhood with the pur-pose of maximizing the accumulationof bone mass and to obtain a greaterbone mass peak that will be main-tained in advanced age.Exercise for patients with OP mustprioritize weight-bearing exercise(especially performing high-impactexercises as early as possible) andRT, because they are the most power-ful exercises to improve BMD. Inaddition, WBV may provide bonemass improvements in the lowerextremities and thus may be addedto the training program. Moreover,patients with high risk of fracture orbeginners can use low-impact andwater-based exercises as a ﬁrst step.All types of effective exercises may beused in the training program in orderto comply with the training variationprinciple and may be used as a speciﬁcpart of the training session (e.g., WBVsuch as a warm-up).Exercise load must focus on the spe-ciﬁc sites with lower BMD and exer-cise. However, because the sites withmore fracture incidences are multiplearound the body (e.g., hip, spine, andthe wrist), practitioners may be bene-ﬁciated in a greater extent by thoseexercises involving multiple joints (e.g., back squat) that may also be per-formed adding a high-impact variation(e.g., jump squat).A suitable progression with a correctexercise technique is needed. All exer-cises must be supervised in the ﬁrsttraining sessions to improve exercisetechnique, program adherence, andsafety. Furthermore, exercise periodi-zation is necessary to prevent injuriesand maintain motivation.To ensure BMD improvements or min-imize bone loss, lifestyle changes such assmoking cessation, moderation in alco-hol consumption, and an adequate dietwith appropriate caloric and calciumintake must be taken into account.Conﬂicts of Interest and Source of Funding:The authors report no conﬂicts of interestand no source of funding.JoaquinCalatayud isa member of theresearch group inSport and Healthin the Depart-ment of PhysicalEducation andSport at theUniversity ofValencia.SebastienBorreani isa member of theresearch group inSport and Healthin the Departmentof Physical Edu-cation and Sportat the Universityof Valencia.Diego Moya isa member of theresearch group inSport and Healthin the Depart-ment of PhysicalEducation andSport at theUniversity ofValencia.Juan C. Coladois a faculty mem-ber and the direc-tor of the researchgroup in Sportand Health in theDepartment ofPhysical Educa-tion and Sport atthe University ofValencia.Strength and Conditioning Journal | www.nsca-scj.com 3Copyright ª Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
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