Effects of High-Intensity Resistance Training on Bone Mineral Density in Young Male Powerlifters

Abstract

The effects of high-intensity resistance training on bone mineral density (BMD) and its relationship to strength were investigated. Lumbar spine (L2-L4), proximal femur, and whole body BMD were measured in 10 male powerlifters and 11 controls using dual-energy X-ray absorptiometry (DXA). There were significant differences in lumbar spine and whole body BMD between powerlifters and controls, but not in proximal femur BMD. A significant correlation was found between lumbar spine BMD and powerlifting performance. These results suggest that high-intensity resistance training is effective in increasing the lumbar spine and whole body BMD.

Full text

Effects of High-Intensity Resistance Training on Bone Mineral Density
in Young Male Powerlifters
S. Tsuzuku,
1
Y. Ikegami,
2
K. Yabe
2
1
Department of Epidemiology, National Institute for Longevity Sciences, 36-3 Gengo, Morioka-cho, Obu-city, Aichi pref,474-8522 Japan
2
Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
Received: 27 February 1997 / Accepted: 23 March 1998
Abstract. The effects of high-intensity resistance training
on bone mineral density (BMD) and its relationship to
strength were investigated. Lumbar spine (L2-L4), proximal
femur, and whole body BMD were measured in 10 male
powerlifters and 11 controls using dual-energy X-ray ab-
sorptiometry (DXA). There were significant differences in
lumbar spine and whole body BMD between powerlifters
and controls, but not in proximal femur BMD. A significant
correlation was found between lumbar spine BMD and
powerlifting performance. These results suggest that high-
intensity resistance training is effective in increasing the
lumbar spine and whole body BMD.
Key words: Bone mineral density — Dual-energy X-ray
absorptiometry — Resistance training — Young male.
One of the most serious public health problems is osteopo-
rosis, characterized by a reduction in the amount of bone
mass. Elderly individuals who have had hip fractures show
lower bone mineral density (BMD) than those of similar age
who have not had fractures [1, 2]. Therefore, maximizing
peak bone mass during youth and maintaining BMD
throughout the aging process is considered to be important
in preventing osteoporosis later in life [3, 4]. Some studies
have found that higher peak forces of mechanical loading
have a greater influence on bone formation than the number
of cycles loaded [5–7]. The effects of weight-bearing exer-
cises such as running, volleyball, gymnastic, and squash
have also been reported for increasing peak bone mass and
BMD [7–12].
Conroy et al. [13] reported higher lumbar spine and
proximal femur BMD in junior male weightlifters (mean
age, 17.7 years) than in age-matched controls. Moreover,
lumbar spine and femoral neck BMD in the junior weight-
lifters were found to be significantly greater than in adult
men aged 20–39 years, based on reference data. Significant
relationships were also found between BMD at all sites and
maximum lifting ability. Other studies have shown that
powerlifters and weightlifters have higher BMD than ath-
letes in other sports and in sedentary individuals [14–17].
Granhed et al. [16] found that bone mineral content of
the lumbar vertebra in powerlifters was significantly higher
than in controls and was correlated (r ⳱0.815) with the
amount of weight lifted annually. They also estimated that
the load on the third lumbar vertebra during a deadlift was
18.8–36.4 kN. These findings suggest that the strain mag-
nitude, the site specificity, and the distribution of strain
throughout the bone structure are important factors in the
adaptive response of the bone [18].
There has not been much research conducted since Gra-
nhed’s biomechanical analysis. Although most studies have
shown greater bone mass in weightlifters, one study actually
found a decrease in bone density with training [19]. The
purpose of this study was to examine the effects of high-
intensity resistance training on BMD in young male pow-
erlifters and its relationship to strength.
Materials and Methods
Subjects
Ten collegiate, male powerlifters (mean age 20.7 ± 1.7 years) and
11 collegiate male controls (mean age 18.4 ± 0.7 years) partici-
pated in this study. Table 1 lists the descriptive characteristics of
the subjects. The powerlifters had participated in a continuous
exercise program for an average of 8 hours/week for at least 12
months prior to the study, and their average years of training
experience was 2.5 ± 1.7. In the daily training program, the train-
ing loads were 80–90% of the one repetition maximum for five
sets of four to eight repetitions. Because powerlifters aim at in-
creasing muscular strength rather than muscle hypertrophy, they
usually use larger weights with fewer repetitions than bodybuild-
ers. The maximum weight lifted for each lifter is shown in Table
2. In contrast, the physical activity of the control group did not
exceed 2 hours/week during the previous 12 months and they had
not been engaged in any resistance training. After being informed
of the purpose and the risks associated with the study, consent was
given by all subjects. No subject in either group had a history of
metabolic bone disease or was taking medication known to affect
mineral metabolism. None of the subjects reported any past or
current use of either anabolic steroids or growth hormones. In all
subjects, circumferences of the chest, upper arm, forearm, thigh,
and calf were measured using standard anthropometric measure-
ment methods. Body mass index (BMI, kg/m
2
) was calculated
from the measured body height and weight. The percentage of
body fat was determined from the sum of the measurements taken
from two skinfolds in the triceps and the subscapular regions. Lean
body mass was calculated from the body weight and the percent-
age of body fat.
Bone Mineral Measurements
The BMD of the lumbar spine (L2-L4), proximal femur (femoral
neck, trochanter region, and Ward’s triangle) and whole body were
Correspondence to: S. Tsuzuku
Calcif Tissue Int (1998) 63:283–286
© 1998 Springer-Verlag New York Inc.

measured by dual-energy X-ray absorptiometry (DXA, HITACHI
BMD - 1X). Measurements for the BMD of the head, arms, legs,
trunk, ribs, pelvis, and spine were obtained by a whole body scan.
All scanning and analyses were done by the same operator to
assure consistency. The day-to-day precision (coefficient of varia-
tion; CV) of the BMD measurement was 0.7%.
Statistical Analysis
All the statistical analyses were made with a Statview 4.5 (Abacus
Concepts, Inc., Berkeley, CA, USA) on a Macintosh computer.
Statistical significance of differences between the two groups was
determined by using the Student’s t-test. To assess the relationship
between the powerlifting records of squat/bench press/deadlift and
BMD, Pearson’s correlation coefficients were used. All compari-
sons were considered statistically significant at P< 0.05.
Results
There were significant differences between the powerlifters
and the controls in both age and lean body mass. The pow-
erlifters also showed significantly larger circumferences in
the upper body measurements than the controls, but no sig-
nificant differences were observed in the lower extremities
(Table 1). Analyzed by Student’s t-test (Fig. 1), the BMD of
the whole body, lumbar spine, arm, leg, and pelvis was
significantly higher in the powerlifters than in the controls.
However, no significant difference (P< 0.05) was found for
the proximal femur BMD. Figure 2 shows the correlations
between BMD and deadlift (DL) records in powerlifters. A
high correlation (r ⳱0.79) between the lumbar spine BMD
and the DL records was observed, but no significant corre-
lation was observed between the femoral neck BMD and the
DL records. Table 3 summarizes the correlation between
BMD and powerlifting performance. The lumbar spine
BMD was significantly correlated with squat (Sq), DL, Sq +
DL, and total records in powerlifters.
Discussion
In this study, we investigated the effects of high-intensity
resistance training on BMD in young male powerlifters. In
powerlifting competition, the records for each lifter are cal-
culated as the sum of Sq, bench press (BP), and DL records.
Powerlifting routines also include both upper (BP) and
lower body exercises (Sq, DL) that involve slow-speed/
high-load muscle contractions. In the present study, because
of their initial ability to lift greater amounts of weight, pow-
erlifters were enrolled to evaluate the effects of high-
intensity resistance training on bone. Many studies have
been conducted to investigate the relationship between
BMD and the intensity of strain in training exercise, site
specificity involved in the exercise, and the strain distribu-
tion in the bone structure [18, 20, 21]. Though most cross-
sectional studies comparing weightlifters to controls have
shown greater BMD, intervention studies have shown in-
consistent results. For example, Rockwell et al. [19] found
contrary results in premenopausal women. Therefore, the
most effective exercise program for significant bone forma-
tion is still not clear.
The results from the present study showed that the pow-
erlifters’ BMD in the lumbar spine was significantly higher
than the controls’. There was a significant positive correla-
tion between the BMD of the lumbar spine and the Sq, DL,
Sq + DL, and total records in powerlifters. These results
suggest that a larger strain may be generated in the lumbar
region during Sq or DL. Although the position of the
weights is different in these two exercises, the force from
the barbell weight in both lifts is applied to the shoulder. To
keep the inclination of the trunk segment constant, a force
necessitating backward rotation of the trunk segment should
be applied. This force must be supplied by muscle contrac-
tion of the erector spinal muscle group, and the contraction
may cause a larger compressive stress in the lumbar region
during Sq and DL.
In contrast to the Sq and DL, there was no significant
positive correlation between the lumbar spine BMD and the
BP records. Taking into account that the BP is an exercise
for the upper body, not for the lumbar muscle area, results
indicate that when bone is mechanically loaded, a response
will occur in that specific bone. The combination of high
magnitude compressive stress and site specificity play a
vital role in increasing the BMD. With the exception of
Rockwell et al.’s study [19], some authors reported an in-
crease of BMD in both the lumbar spine and femoral neck
[13, 22], and others indicated increases only in the lumbar
spine [23–25]. Kerr et al. [12] examined the effect of exer-
cise on bone mass in postmenopausal women and observed
significant increases in BMD of the greater trochanter re-
gion where various muscle groups were attached but not in
BMD of the femoral neck where no muscles were attached.
They speculated the reason to be because muscle pull is
Table 1. Anthropometric data for powerlifters and controls (mean
±SD)
Powerlifters
(n ⳱10) Controls
(n ⳱11)
Height (cm) 167.5 ± 6.0 168.5 ± 4.8 —
Body weight (kg) 70.6 ± 10.8 64.5 ± 9.4 —
Age (y) 20.7 ± 1.3 18.4 ± 0.7
b
—
BMI (kg/m
2
) 25.0 ± 2.5 22.6 ± 2.8 —
%Fat (%) 17.7 ± 5.7 19.2 ± 5.9 —
LBM (kg) 57.6 ± 6.2 51.7 ± 5.3
a
—
Chest (cm) 94.7 ± 7.7 85.8 ± 5.8
b
—
Upper arm (cm) 30.9 ± 2.7 27.8 ± 2.2
b
—
Forearm (cm) 27.5 ± 1.7 25.1 ± 1.5
b
—
Thigh (cm) 55.4 ± 6.9 51.7 ± 4.9 —
Calf (cm) 39.8 ± 5.4 36.9 ± 2.6 —
BMI: body mass index, LBM: lean body mass
a
P < 0.05;
b
P< 0.01
Table 2. The age, height, body weight, and the best record for
each lifter
Powerlifter Ht
(cm) BW
(kg) Age
(y) Sq
(kg) BP
(kg) DL
(kg) Total
(kg)
1 158 51 20 115.0 72.5 145.0 332.5
2 173 78 20 150.0 75.0 165.0 390.0
3 159 57 20 135.0 75.0 180.0 390.0
4 168 80 24 150.0 100.0 150.0 400.0
5 167 67 20 150.0 95.0 180.0 425.0
6 176 83 21 175.0 90.0 195.0 460.0
7 169 80 21 165.0 120.0 175.0 460.0
8 175 76 21 185.0 110.0 205.0 500.0
9 165 65 21 210.0 110.0 200.0 520.0
10 166 69 19 185.0 117.5 235.0
a
537.5
Ht: height, BW: body weight, Sq: squat, BP: bench press, DL:
deadlift
a
Japan junior record
S. Tsuzuku et al.: BMD in Powerlifters284

mediated through the force of the muscle contraction at the
site of attachment of tendon to bone; thus, the bone may
respond locally to reallocate the forces generated from the
muscle at the site of loading [12]. Although, the Sq, and DL
exercises require contraction of various muscle groups that
are attached to the trochanter region, we found no signifi-
cant relationship between the powerlifting performance and
the proximal femur BMD in this study. Moreover, there was
no significant difference in the proximal femur BMD be-
tween the powerlifters and the controls. Several explana-
tions for why the BMD of proximal femur did not signifi-
cantly differ between powerlifters and controls are possible.
First, because of the angular shape of the proximal femur,
the stress is not of a compressive type, but rather of a
bending type stress, which may not be an effective stimuli
for bone formation. Second, the proximal femur is always
loaded in daily life by walking, standing, and other postures
in which the threshold becomes significantly higher, and
does not always give a noticeable response, as does the
lumbar spine. And third, the lumbar spine is composed of as
much as 80% trabecular bone, whereas the proximal femur
is only 50%. The metabolic rate of trabecular bone is eight
times higher than that of cortical bone. Therefore, different
metabolic rates and bone compositions with site-specific
differences in the skeleton may cause variable osteogenic
thresholds for loading stimuli. Furthermore, the duration of
the high-intensity resistance training of powerlifters in the
present study (2.5 years) may not be enough to increase the
BMD of the proximal femur.
In summary, in studies comparing several activities (run-
ning, gymnastics, volleyball, swimming weightlifting etc.)
it was found that high-intensity loading is effective in in-
creasing BMD [7, 9, 11]. Although this study supports this
suggestion, our results were not derived from comparisons
of other sports study results, but only from direct biome-
chanical analysis of a high-intensity resistance training.
Granhed et al. [16] have shown a positive correlation be-
tween the L3 bone mineral content and the amount of
weight lifted annually. They only analyzed and examined
DL exercise, not Sq exercise. In our study the effects of the
Sq exercise were also examined, and the results suggest the
importance of compressive stress generated in Sq as well as
DL for increasing lumbar BMD. In conclusion, exercise or
training with high-intensity loads to generate compressive
stress on bone may be effective in increasing site-specific
BMD in the skeleton.
Acknowledgments. A part of this study was financially supported
by the Ministry of Education, Science, Sports and Culture, Grant
No. 07458016. We are grateful to Drs. Minoru Yoneda and Mas-
ayuki Suzuki for their support.
Fig. 1. Bone mineral density in powerlifters
(n ⳱10) and controls (n ⳱11). FN, femoral
neck; Troch, trochanter region; Ward’s,
Ward’s triangle.
Fig. 2. Correlations between BMD and DL records.
Table 3. Correlations between BMD and powerlifting perfor-
mance
Lumbar
spine Femoral
neck Trochanter
region Ward’s
triangle
Squat 0.74
a
−0.01 0.07 −0.37
Bench press 0.47 0.02 0.24 −0.07
Deadlift 0.79
b
−0.01 0.02 −0.36
Total 0.77
b
0.00 0.11 −0.33
Squat + Deadlift 0.81
b
−0.01 0.05 −0.39
a
P< 0.05;
b
P< 0.01
S. Tsuzuku et al.: BMD in Powerlifters 285

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