Re: Bone Density?

August 7, 2006

Previously posted on the ST message board:

Members may find the following to be of some interest:

J Sports Sci. 2004 Jul;22(7):645-50.

Do sporting activities convey benefits to bone mass throughout the

skeleton?

Nevill A, Holder R, A.

It is well known that sport and exercise play an important role in

stimulating site-specific bone mineral density (BMD). However, what

is less well understood is how these benefits dissipate throughout

the body. Hence, the aim of the present study was to compare the BMD

(recorded at nine sites throughout the skeleton) of 106 male athletes

(from nine sports) with that of 15 male non-exercising age-matched

controls.

Given that BMD is known to increase with body mass and peak with age,

multivariate and univariate analyses of covariance were performed to

compare the BMD of the nine sports groups with controls (at all

sites) using body mass and age as covariates. Our results confirmed a

greater adjusted BMD in the arms of the upper-body athletes, the

right arm of racket players and the legs of runners (compared with

controls), supporting the site-specific nature (i.e. specific to the

externally loaded site) of the bone remodelling response (all P

<0.01). However, evidence that bone mass acquisition is not just site-

specific comes from the results of the rugby players, strength

athletes, triathletes and racket players. The rugby players' adjusted

BMD was the greatest of all sports groups and greater than controls

at all nine sites (all P <0.01), with differences ranging from 8%

greater in the left arm to 21% in the lumbar spine. Similarly, the

strength athletes' adjusted BMD was superior to that of controls at

all sites (P < 0.05) except the legs.

The adjusted BMD of the triathletes was significantly greater than

that of the controls in both the arms and the legs as well as the

thoracic and lumbar spine. The racket players not only had

significantly greater right arm BMD compared with the controls but

also a greater BMD of the lumbar spine, the pelvis and legs. In

contrast, the low-strain, low-impact activities of keep-fit, cycling

and rowing failed to benefit BMD compared with the age-matched

controls. These results suggest that sporting activities involving

high impact, physical contact and/or rotational forces or strains are

likely to convey significant benefits not only to the loaded sites,

but also to other unloaded peripheral and axial sites throughout the

skeleton.

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Swim-trained rats have greater bone mass, density, strength, and dynamics. J

Appl Physiol 2001 Oct; 91(4): 1663-8

Hart KJ, Shaw JM, Vajda E, Hegsted M, SC

Weight-bearing exercise is traditionally recommended for improving bone health

in postmenopausal women. Effects of swim exercise were studied as an alternative

to weight-bearing exercise in ovariectomized rats. Rats in a swim group swam for

12 wk, 5 days/wk for 60 min per session. A control group engaged in no

structured exercise. Femurs were analyzed for bone mineral density and for bone

mineral content by dual energy X-ray absorptiometry, biomechanical properties by

three-point bending (Instron), and bone structure and formation by

histomorphometry. Food intake did not differ among groups.

Final body weights were significantly lower in Sw compared with Con.

Swimmers had significantly greater femoral shaft bone mineral density and

content compared with Con. Femurs of the Sw group had greater mechanical

properties compared with Con. Histomorphometric data were significantly better

in the Sw group compared with Con after the 12-wk intervention. In conclusion,

data from this study demonstrate some beneficial effects of swim exercise on

bone structure, turnover, and strength.

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Bone mineral content and body composition in postpubertal cyclist boys.

Rico H, Revilla M, ER, Gomez-Castresana F, Villa LF. Bone 1993

Mar-Apr;14(2): 93-5

The effect of sports activity on bone mass was assessed by dual-energy X-ray

absorptiometry in a group of 22 young cyclists aged 16.2 ± 0.7 years. These

athletes trained for 10 hours a week for over two years. Bone mass values were

compared with those of 27 sedentary youngsters aged 16.9 ± 0.3 years.

There were no differences in total body bone mineral (TBBM) between groups. The

leg bone mineral content (LBMC), body weight, and percentage fat were lower in

the cyclists than in controlsr. No changes were observed when TBBM was

normalized for weight. The changes observed earlier in LBMC disappeared when

normalized for body weight.

These results suggest that cycling does not stimulate bone mass in

youngsters, and that the type, quality, and length of sports activity need to be

defined.

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Skull bone mass deficit in prepubertal highly-trained gymnast girls.

Int J Sports Med 1999 Jul; 20(5): 328-33

Courteix D, Lespessailles E, Obert P, Benhamou CL.

It is known that impact loading sport can increase the bone mineral

density in the stressed sites of the skeleton in athletes. However,

non weight-bearing sites are seldom studied in healthy young girl

athletes.

In order to study the effects of a long term intensive training on the

non-stressed region of the skeleton (skull), we investigated both

highly-trained girl athletes, involved in sports requiring or not

significant impact loading on the skeleton and a girl control group.

Bone mineral content (BMC) and density (BMD) were measured in the

whole body, at lumbar spine, femoral neck, trochanter, Ward's

triangle, radius, head and ribs, in 60 prepubertal girls including 12

swimmers, 32 gymnasts and 16 controls. Measurements were made by DXA.

There were no statistical differences between the groups as regards

age, height, body weight, body mass index, lean tissue mass and

dietary calcium intake. Mean BMD in gymnasts was statistically higher

than in other groups for radius, femoral neck and Ward's triangle

while there was no difference between swimmers and controls.

Head BMC was significantly lower in gymnasts compared to other groups

(241.9 ± 41 g vs. 285.8 ± 34.7 g and 291.1 ± 50.2 g respectively in

swimmers and controls. The same observation was made for head BMD.

When body weight was used as a covariant, the contribution of the

head BMC to the whole body was significantly lower in gymnasts

(24.97%) than in swimmers (27.88%) and controls (27.77%). When

compared between groups, the slopes of the regressions for head/whole

body BMC or BMD were significantly lower in gymnasts than in other

groups.

These data suggest that in prepubertal children the increased bone

density induced by gymnastic training in the stressed sites of the

body could be related to a decreased skull bone mass.

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Power training is more effective than strength training for

maintaining bone mineral density in postmenopausal women.

J Appl Physiol. 2005 Mar 3;

von Stengel S, Kemmler WK, Lauber D, Pintag R, Beeskow C, Weineck J,

Kalender WA, Engelke K.

Physical exercise has a favourable impact on bones, but optimum

training strategies are still under discussion. In this study we

compared the effect of slow and fast resistance exercises on various

osteodensitometric parameters. 53 postmenopausal women were randomly

assigned to a strength (ST) or a power training group (PT). Both

groups carried out a progressive resistance training, a gymnastics

session, and a home training over a period of 12 months. During the

resistance training the ST group used slow and the PT group fast

movements, otherwise there were no training differences.

All subjects were supplemented with Ca/Vit-D. At baseline and after

12 months, BMD was measured at the lumbar spine, proximal femur, and

distal forearm by DXA. We also measured anthropometric data and

maximum static strength. Frequency and grade of pain were assessed by

questionnaire. After 12 months, significant between-group differences

were observed for BMD at the lumbar spine (L1-L4) (p<0.05) and the

total hip (p<0.05). While the PT group maintained BMD at the spine

(+0.7+/-2.1%, n.s.) and the total hip (0.0+/-1.7%, n.s.), the ST

group lost significantly at both sites (spine: -0.9+/-1.9%; p<0.05;

total hip: -1.2+/-1.5%; p<0.01). No significant between-group

differences were observed for anthropometric data, maximum strength,

BMD of the forearm, or frequency/grade of pain. These findings

suggest that power training is more effective than strength training

in reducing bone loss in postmenopausal women.

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