EXERCISE AND QUALITY OF LIFE
Volume 6, Issue 2, December 2014
UDC: 796.012.1:612.751
DIFFERENCES IN PARAMETERS OF BONE MINERAL DENSITY BETWEEN
ELITE ATHLETES AND NON ATHLETES
Anita Šolaja, Milan Šolaja and Borislav Obradović
Faculty of sport and physical education - University of Novi Sad
Correspondence to:
Anita Šolaja
Address: Bulevar cara Lazara 7, 21000 Novi Sad
Telephone: 06505350054
E-mail address: anitasolaja@yahoo.com
Abstract
The aim of this study is to investigate the differences in parameters of bone mineral
density in elite track and field athletes and sedentary male controls, respectively non-athletes.
The research included 15 athletes who are members of the national junior track and field team
of Serbia and 15 non-athlete boys, aged 17 to 19 years. Sahara (Hologic, Inc., MA 02154,
USA) clinical sonometer was used for assessing bone density. The parameters of bone
mineral density were measured, Speed of sound (SOS), Broadband ultrasound attenuation
(BUA), Bone mineral density (BMD) and Width of the heel bone, as well. T-test for two
independent groups confirmed that there is statistically significant difference between elite
track and field athletes and non-athletes in all measured parameters (p < 0.05). The results of
this study confirm the significant effects of practicing track and field events on increasing
bone mineral density and preventing osteoporosis.
Keywords: Bone density, calcaneus, male, track and field, sedentary controls
Introduction
The World Health Organization (WHO) defines osteoporosis as a condition in which
the bone mass decreases by 2.5 standard deviations from those in young and healthy people of
the same sex (WHO, 1994). Disorder of bone remodeling, in which newly formed bone is
being formed then it breaks down old bone previously, is the main cause of osteoporosis.
Osteoporosis is characterized by low bone mass and bone loss leads to fragility and increased
risk of fracture (Drinkwater, 1994). The result of decreased bone strength is increasing the
14
risk of fracture, even due to slight injuries. Osteoporosis occurs in both sexes and can occur at
any age. For both sexes, the risk of osteoporosis increases with age, while the risk of
osteoporotic fracturesis the highest in people over 80 years (Delmas & Fraser, 1999).
Although aging is inevitable, mechanical stresses that occur during exercise, are
proven to alter or delay the reduction of bone mass associated with the aging process (Smith
& Gilligan, 1991). The first study that addressed this hypothesis showed that athletes
subjected to high load activities had 10-20% higher bone mineral density (BMD) compared to
the controls (Nilsson & Westlin, 1971). Today, there is compelling evidence indicating that
physical activity affects the skeleton and the BMC and BMD in an anabolic way (Hind &
Burrows, 2007).
Maximum of bone mass is acquired during the second and the third decade of life.
Active practice of sport in the years in which the peak of bone mass is obtained, can lead to
adaptive changes that improve the architecture of the bones through increased density and
improved geometric properties of bone (Tenforde & Fredericson, 2011).
Research done on athletes shows that they have higher bone mass than non-athletes
and that the bone density increases during the periods of intensive training (Bajić Z, Ponorac,
Rašeta, & Bajić Đ, 2010). Exercise studies have also shown which type of exercise confers
maximal anabolic effects on the skeleton. Skeletal load that includes a dynamic load, a load
with a high magnitude, a high frequency load, a fast load and a load with unusually
distributed strains provide the most pronounced osteogenic stimuli (Lanyon, 1992; Rubin &
Lanyon, 1984; Turner, Woltman & Belongia, 1992). Researches has shown that BMD is the
highest in athletes who participate in high- impact exercise, defined as activities involving
running, jumping and weight lifting (Bennell, Malcolm, Khan, Thomas, Reid, Brukner et al.,
1997; Pettersson, Nordström, Alfredson, Henriksson-Larsén & Lorentzon, 2000; Yung, Lai,
Tung, Tsui, Wong, Hung & Qin, 2005; Andreoli, Monteleone, Van Loan, Promenzio,
Tarantino & De Lorenzo, 2001). These results suggest that the type of sport activity may be
an important factor in achieving a high peak bone mass and reducing osteoporosis risk
(Andreoli et al., 2001).
Furthermore, it is very important for elite athletes to have healthy bones, because low
BMD significantly increases the risk of fractures at minimal traumas (stress fracture) (Kohrt,
Bloomfield, Little, Nelson & Yingling, 2004). These types of injuries are common in certain
populations of athletes and represent between 0.7% and 20% of all sports medicine injuries
seen in medical clinics (Matheson, Clement, McKenzie, Taunton, Lloyd-Smith & MacIntyre,
1987; Chen, Tenforde & Fredericson,
2013; Harrast & Colonn,
2010; McCormick,
Nwachukwu & Provencher, 2012). The current understanding is that maximizing peak bone
mass is key to preventing osteoporosis and osteoporotic fractures
(Heinonen, Sievanen,
Kannus et al., 2000; Courteix, Lespessailles, Peres et al.,1998).
The present study is aimed at assessing the characteristics of the bones of high-
performance, top level competitive athletes, using calcaneal ultrasound. This study
investigates the differences in parameters of bone mineral density in highly trained athletes, in
elite track and field athletes and sedentary male controls.
15
Method
The survey was conducted on a sample of 30 boys, aged 17 to 19 years. Of that
number, 15 boys are members of the national junior track and field team of Serbia, and
another 15 are high school students who are not engaged in sports. The first part of the survey
was conducted in April 2015, at the official training camp for a national track and field
selection in Bar (Montenegro). The second part of research is also conducted in April 2015, at
the Central School of Economics in Niš.
The sample of variables in this study reflected the four variables for assessment of skeletal
status, ie. Bone density:
1) The width of the take-off leg calcaneus (Width, in mm),
2) Sos - Speed of sound: take-off leg calcaneus (SOS, in m/s),
3) Bua - Broadband ultrasound attenuation: take-off leg calcaneus (BUA, in dB/MHz),
4) Bmd - Bone mineral density: take-off leg calcaneus (BMD, in g/cm).
Ultrasound bone densitometry was performed in each subject. The device used was
Sahara (Hologic, Inc., MA 02154, USA) clinical sonometer that uses non-ionizing ultrasound
for assessing bone density. The results obtained by this method are sufficiently correlated to
the other methods and from other body locations (Faulkner, McClung, Coleman, Kingston-
Sandahle, 1994). This device was used because it is easily portable, so each subject could be
scanned quickly, without disturbing their daily routine training/competition. Measurements
were taken while the subjects were seated with the dominant foot resting in the heel bath of
the instrument. Patient examination time was short, with a measurement time (excluding
patient positioning) of less than ten seconds. Quantitative parameters describing the speed and
attenuation of the sound waves in the heel are measured. The device is calibrated daily using a
model (phantom). All scans were performed by the same technician. Following parameters
were measured: SOS, BUA, BMD as well as Width of calcaneal bone of take-off leg of
respondents.
The obtained data were processed in the statistical package SPSS
(20.0). The
Kolmogorov-Smirnov test was used to assess normal distribution of the variables. The
standard tests for normality and homogeneity of variance found that these assumptions were
valid. Differences between two groups were analyzed with T-test for two independent groups,
track and field athletes and non-athletes. Statistical significance was set at p<0.05.
The principal inclusion criteria to this study were age, sex, sport history (minimum
five years of active sports occupation in track and field) and absence of diseases. The survey
did not include the hormonal status of respondents nor trial of the use of supplements in the
diet, rather than that it focused on the differences in the above mentioned parameters of bone
mineral density between the top athletes, ie. track and field athletes and non-athlete male
controls.
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Results
On the base of the values of the statistical parameters of normality of the curve
distribution of data, it was observed that the distribution of the data of all the variables applied
in this study does not deviate significantly from the normal distribution.
For the variable Width of heel bone, value of t-test was 2.32 at a significance level of
0.03, which indicates that there is a statistically significant difference between athletes and
non-athletes. The sign of t-test indicates a direction of determined difference. A negative
value means the difference in favor of another group, ie. non-athletes, who obtained better
result, respectively they had a greater width of the heel bone (calcaneus) in relation to the
track and field athletes. This confirms the value of arithmetic means of groups that is higher in
non-athletes (M=43.87 mm) with a standard deviation of 2.83 mm compared to track and field
athletes (M=41.36; SD=3.11) (Graph 1).
Graph 1. The value of the arithmetic mean width of the heel bone athletes and non-athletes.
43.87
44
43.5
43
42.5
M
41.36
42
41.5
41
40.5
40
Athletes
Non-athletes
The value of the t-test for a variable SOS was
5.46 at significance level of 0 .000
which is less than the selected limit value of 0.05. Based on the values of the results, it can be
concluded that there is a statistically significant difference in the rate of penetration of the
ultrasonic waves (SOS) through the heel bone. As the results are expressed in seconds, the
ultrasonic wave penetrated faster into the heel bone of non-athletes (M=1554.87; SD=19.49)
at a statistically significant level, in comparison to the track and field athletes (M=1602.95;
SD=27.95) (Graph 2).
Graph 2. The value of the arithmetic mean of penetration rate of ultrasonic waves through the
heel bone (SOS) in athletes and non-athletes.
17
1602.95
1610
1600
1590
1580
M
1554.87
1570
1560
1550
1540
1530
Athletes
Non-athletes
For the variable BUA, the values of significance of t-test (t = 3.87) showed that there
is a statistically significant difference
(p= 0.001) in the speed of the ultrasonic wave
attenuation through the heel bone. In the group of track and field athletes, weakening of the
wave through the calcaneus was greater than in the group of sedentary controls, which can
be recognized on the base of the arithmetic mean value of this parameter
(M=98.64;
SD=20.12) compared to the sedentary group (M=75.45; SD=11.58) (Graph 3).
Graph 3. The value of the arithmetic mean in weakening of the ultrasonic wave when passing
through the heel bone (BUA) in athletes and non-athletes.
98.64
100
75.45
80
60
M
40
20
0
Athletes
Non-athletes
According to the results obtained for BDM parameter, it can be concluded that the
group of athletes has increased estimated mineral density of the calcaneus (M=0.72, SD=0.12)
compared to the control group (M= 0.54; SD=0.08) (Graph 4). The differences between these
two groups was at significant level (p=0.000).
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Graph 4. The value of the arithmetic mean of the estimated mineral (eBDM) density of the
calcaneus in athletes and non-athletes.
0.72
0.8
0.54
0.6
M
0.4
0.2
0
Athletes
Non-athletes
Discussion
The main goal of this study is to examine and compare the bone mineral density
parameters of elite track and field athletes and inactive controls. The results of our study are
consistent with the results of numerous studies between athletes and non-athletes (Arasheben,
Barzee & Morley, 2011; Kaštelan, Kraljević, Kardum, Kasović Dušek, Protulipac et al., 2007;
Suominen, 1993; Karlsson, Johnell & Obrant, 1993a; Karlsson, Johnell & Obrant, 1993b;
Nikander, Sievanen, Heinonen & Kannus, 2005; Karlsson, Hasserius & Obrant, 1996) and
support the fact that athletes have greater bone mineral density than sedentary controls. In our
study elite athletes had higher values of all measured parameters of BMD at statistically
significant level (p<0.03) compared with sedentary male controls, except width of the heel
bone. In the existing literature, the authors found neither research that explicitly compares
data width of the calcaneus between athletes and non-athletes, nor research that compares
width of calcaneus with correlation of bone mineral density.
The second measured parameter in our study was the Speed of sound, and it refers to
the division of transmission time of the sound waves by the length of the body part studied
(Kok-Yong & Ima-Nirwana, 2013). Measurements of SOS parameter revealed statistically
significant difference between the group of track and field athletes and sedentary male
controls (Graph 2).
The third measured bone density parameter was BUA - Broadband attenuation of
sound which refers to the slope between attenuation of sound signals and its frequency.
Attenuation occurs because the energy is absorbed by the soft tissue and bone when the sound
waves travel through them (Kok-Yong & Ima-Nirwana, 2013). Weakening of the ultrasonic
signal as it passes through the heel bone is bigger in athletes than non-athletes, in this study
(Graph 3).
The level of significance showed that elite track and field athletes had greater BMD at
statistically significant level comparing to inactive controls (Graph 4). Generally, athletes
19
have higher BMD than age-matched sedentary controls (Suominen, 1993; Karlsson, Johnell &
Obrant, 1993a; Karlsson, Johnell & Obrant, 1993b; Nikander, Sievanen, Heinonen & Kannus,
2005; Karlsson, Hasserius & Obrant,
1996). Several cross-sectional studies have
demonstrated higher BMD among athletes who engage in weight bearing and impact sports
when compared to non-athletes (Davee et al., 1990; Stewart & Hannan, 2000). It is more
effective to provide a higher intensity stimulus than simply to extend the duration of lower
intensity loading activities (Bennell et al., 1997; Marcus, 2001), as it is in practicing track and
field events.
In the 12 month longitudinal cohort study, Benell et al. (1997) came up with results
that track and field athletes also had higher mineral bone density than non-athletes. They were
comparing bone mass and bone turnover in elite and subelite track and field athletes and less
active controls, aged 17-26 years. Baseline results showed that power athletes had higher
regional BMD at lower limb, lumbar spine, and upper limb sites compared with controls (p <
0.05). Endurance athletes had higher BMD than controls in lower limb sites only (p < 0.05).
Besides that, Whittington et al. (2009) concluded that throwers had greater BMD than non-
athletes and most other athletes. Furthermore, the cross-sectional study of Andreoli et al.
(2001) showed that athletes, especially those engaged in high-impact sports, had significantly
higher total BMD than controls. These results suggest that the type of sport activity may be an
important factor in achieving a high peak bone mass and reducing osteoporosis risk (Andreoli
et al., 2001).
Low BMD significantly increases the risk of fractures at minimal traumas (stress
fracture) (Kohrt et al., 2004). In a meta-analysis, Moayyeri et al. (2012) confirmed that SOS,
BUA, SI (stiffness index) and QUI (quantitative ultrasound index) significantly predicted
fractures after reviewing 21 independent studies. Bone stress injuries result from chronic
repetitive training and can range from a stress reaction to a cortical fracture (Matheson et al.,
1987). Stress fractures occur in several different bones. The distribution of stress fractures
differs according to activity. The tibia is reported to be the most frequently injured bone in
runners (Hulkko & Orava, 1987; Ha, Hahn, Chung, Yang & Yi, 1991), followed by the fibula,
metatarsal and pelvis (Matheson et al., 1987). Fifteen percent of all stress fractures occur in
runners (Matheson et al., 1987) accounting for 70% of all of their injuries (Orava, 1980). This
study results can be helpful in the prediction of fractures for both coaches and athletes
because this type of injuries are common in athletes (Knobloch, Schreibmueller, Jagodzinski,
Zeichen, Krettek, 2007; Brukner, Bradshaw, Kahn, White, Crossley, 1996; Øyen, Klungland,
Torstveit, Sundgot-Borgen, 2009).
This study supports previous researches, indicating a positive effect of high-impact
sports, as well as track and field, as one of that type of sport, on BMD in elite athletes.
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