J Appl Physiol 100: 839 – 843, 2006.
First published November 3, 2005; doi:10.1152/japplphysiol.00666.2005.
Effect of low-repetition jump training on bone mineral density
in young women
Takeru Kato,1 Toru Terashima,2 Takenori Yamashita,3
Yasuhiko Hatanaka,4 Akiko Honda,5 and Yoshihisa Umemura5
Departments of 1Clinical Nutrition, 3Clinical Radiation, and 4Physical Therapy, Faculty of Health Science, and 2Health
Administration Center, Suzuka University of Medical Science, Kishioka, Suzuka; and 5Laboratory for Exercise Physiology
and Biomechanics, School of Health and Sport Sciences, Chukyo University, Kaizu-cho, Toyota, Japan
Submitted 4 June 2005; accepted in final form 1 November 2005
jump exercise; peak bone mass; high-impact training
randomized control group (6). Bassey and Ramsdale (1) found
a significant increase in femoral BMD after 6 mo of 50 jumps
daily among premenopausal young women (29.8 –32.0 yr).
These exercise programs, however, required a relatively large
number of jumps in the range of 300 –350 jumps/wk. Johannsen and coworkers (11) have found greater increases in
total and leg bone mineral content (BMC) by relatively fewer
jumps from a 45-cm-high box, 25 jumps/day, 5 times/wk, total
of 125 jumps/wk in a randomized, controlled trial conducted
with children (3–18 yr). Also, Snow et al. (24) reported, after
5 yr of resistance training with weighted vest and an average
51.7 jumps/day, 3 times/wk, for a total of 155 jumps/wk from
a 20.3-cm-high step, improved femoral neck BMD compared
with a control group in postmenopausal woman (64.1– 69.9 yr).
Evidence from more invasive interventions in animals suggested that a quite brief exposure to strain is enough (9, 10, 15,
26 –28). Rubin and Lanyon (23) presented results showing that a
passive stimulus of 36 and 1,800 cycles/day was equally effective
in turkeys. A smaller number of strains, as few as 5 jumps/day
(26), imposed by active stimuli as jumps, improved the strength of
regional bones in immature rats, although the training required
only a short time. The hypothesis of the present study was that
low-repetition high-impact jump training, 10 jumps/day and 3
times/wk, would be effective for improving BMD in ordinary
young women reaching the age of peak bone mass.
MATERIALS AND METHODS
an important role in maximizing
bone mass during childhood and may have long-lasting benefits on bone health. Because peak bone mass is thought to be
attained by the end of the third decade, the early adult years
may be the final opportunity for its augmentation (13). Skeletal
unloading, such as long bed rest, immobilization, and microgravity environment, lead to bone loss, whereas the positive
effects of physical exercise on bone mass is generally acknowledged. It has been shown that dynamic loading is more effective for increasing bone mineral density (BMD) than static
loading (15). Furthermore, the strain rate is more important
than the number of loading trials (22).
Prepubescent children (7.5– 8.2 yr) who have not yet
reached their peak bone mass have shown significant development in lumbar spine bone mass by 100 two-footed drop
landings off of a 61-cm-high box 3 times/wk compared with a
Subjects and groups. One hundred twenty-eight female college
students with experience in weighted food records were asked to take
part in this study, and 48 students volunteered to participate. The
subjects completed the questionnaire containing information about
menstrual cycle, pregnancy, past and current physical activity, smoking habit, as well as background information, including history of
bone diseases, medication use, and bone fracture. The entry criteria
for subjects were eumenorrheic, nonpregnant, no oral medication,
nonsmoker, no regular high-impact training, with no medical or
surgical problems likely to affect bone metabolism or providing
contraindications to exercise. Six subjects were excluded because they
had regularly engaged in high-impact sports such as volleyball,
basketball, and tennis in the last 5 yr.
Forty-two subjects were randomly divided into two groups, jump
training or a control group. In compliance with the university’s
Institutional Review Board policy, the purpose and all experimental
procedures were explained, and written, informed consent was then
obtained from each subject. The study was approved by the local
Address for reprint requests and other correspondence: T. Kato, Faculty of
Health Science, Suzuka Univ. of Medical Science, Kishioka, 1001-1, Suzuka
510-0293, Japan (e-mail: [email protected]).
The costs of publication of this article were defrayed in part by the payment
of page charges. The article must therefore be hereby marked “advertisement”
in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
PHYSICAL ACTIVITY MAY PLAY
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Kato, Takeru, Toru Terashima, Takenori Yamashita, Yasuhiko Hatanaka, Akiko Honda, and Yoshihisa Umemura. Effect of
low-repetition jump training on bone mineral density in young
women. J Appl Physiol 100: 839 – 843, 2006. First published November 3, 2005; doi:10.1152/japplphysiol.00666.2005.—The hypothesis
of the present study was that low-repetition and high-impact training
of 10 maximum vertical jumps/day, 3 times/wk would be effective for
improving bone mineral density (BMD) in ordinary young women.
Thirty-six female college students, with mean age, height, and weight
of 20.7 ⫾ 0.7 yr, 158.9 ⫾ 4.6 cm, and 50.4 ⫾ 5.5 kg, respectively,
were randomly divided into two groups: jump training and a control
group. After the 6 mo of maximum vertical jumping exercise intervention, BMD in the femoral neck region significantly increased in the
jump group from the baseline (0.984 ⫾ 0.081 vs. 1.010 ⫾ 0.080
mg/cm2; P ⬍ 0.01), although there was no significant change in the
control group (0.985 ⫾ 0.0143 vs. 0.974 ⫾ 0.134 mg/cm2). And also
lumbar spine (L2– 4) BMD significantly increased in the jump training
group from the baseline (0.991 ⫾ 0.115 vs. 1.015 ⫾ 0.113 mg/cm2;
P ⬍ 0.01), whereas no significant change was observed in the control
group (1.007 ⫾ 0.113 vs. 1.013 ⫾ 0.110 mg/cm2). No significant
interactions were observed at other measurement sites, Ward’s triangle, greater trochanter, and total hip BMD. Calcium intakes and
accelometry-determined physical daily activity showed no significant
difference between the two groups. From the results of the present
study, low-repetition and high-impact jumps enhanced BMD at the
specific bone sites in young women who had almost reached the age
of peak bone mass.
840
JUMP TRAINING IN YOUNG WOMEN
movement style on 3 alternated days/wk. The maximum jumps were
performed barefoot at home on a relatively hard floor. The interval of
each jump was ⬃8 –12 s, so the exercise required less than 2 min.
Home record cards were supplied and collected each month.
Maximum vertical jump and ground reaction force. Maximum
vertical jump height was measured by a jump height measuring device
(Takei Scientific Instruments, Jump-MD) in both the pre- and postexercise program. At both visits for measuring jump height, subjects jumped
vertically at least twice with maximum voluntary effort, and the best
performance was recorded. The subjects stood at the center of the circular
thin rubber mat (38 cm in diameter). The jumper attached the heightmeasuring device to her waist. The jump height measuring device and the
circular mat were attached by a rope so that the traveling distance from
the standing position to the maximum height reached at waist level could
be measured. When the jumpers could not land stably within the circular
rubber mat, the jumpers had to perform another trial.
Peak ground reaction force (GRF) was measured by using the
AMTI force platform (Advanced Mechanical Technology, OR6-6,
46.4 ⫻ 50.8 cm) in a randomly selected subsample of volunteers (n ⫽
12) in a jump group at posttesting. They were asked to jump vertically
with maximum effort, using countermovement style as they did
regularly during the jump exercise intervention period, and jumping
trials were conducted at least three times for each subject. The force
platform was used to record GRF with a 1,080-Hz sampling rate.
Values for the peak force on the vertical axis were then obtained from
the recordings at takeoff and landing.
Accelerometry-determined measures of physical activity. The subjects were asked to attach the accelerometer motion sensor (Suzuken,
Lifecorder EX) at waist height for a whole week except while sleeping
or bathing. The physical activity measurements were done during
September to October, about halfway through the whole intervention
period. Movement count values, shown as steps, were stored every 2
min. The stored data on the accelerometer motion sensor were
downloaded by personal computer using a USB cable for analysis.
Statistics. Two-way ANOVA [2 times (initial and final) ⫻ 2 groups
(jump and control)] with repeated measures was used to determine
differences between and within the jump and control groups for dependent variables. When ANOVA revealed significant interaction (time ⫻
group), paired t-tests were performed to determine differences between
initial and final values in each group. Initial mean physiological characteristic values and daily activity shown as steps were compared using
unpaired Student’s t-test. Statistical analysis was achieved through computer programs available in the Statistical Package for the Social Sciences, version 12.0J (SPSS). The statistically significant level was set at
0.05, and comparisons were two tailed.
RESULTS
Descriptive statistics indicated that the initial height, age,
and movement count were not significantly different between
the jump and control groups (Table 1). In the jump group,
compliance (82%) at jump training was averaged 2.5 times/wk.
Table 1. Physiological characteristics of the subjects, calcium intake, jump height, movement count, and DPD
Jump (n ⫽ 18)
Initial
Age, yr
Height, cm
Weight,* kg
Calcium, mg
Vertical jump,* cm
Movement count, steps/day
DPD, nmol/mmol creatinine
20.5⫾0.6
159.1⫾3.8
51.1⫾5.2
760.6⫾146.6
38.1⫾5.5
Control (n ⫽ 18)
Final
Initial
Final
50.2⫾4.9
719.6⫾209.6
41.5⫾7.3
20.9⫾0.8
158.8⫾5.4
49.6⫾5.8
654.6⫾163.8
39.6⫾6.2
49.0⫾6.2
659.9⫾151.8
40.8⫾7.4
5.4⫾1.8
5.4⫾1.5
6,746.4⫾2,034.2
5.8⫾1.5
(n ⫽ 10)
6,881.7⫾1,546.6
Values are means ⫾ SD. DPD, deoxypyridine. *Significant difference within groups (P ⬍ 0.05).
J Appl Physiol • VOL
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health research review board. The subjects were permitted to withdraw at any time for any reason. Bone measurements were conducted
at initial baseline and final completion of the 6-mo exercise program.
Because the training consisted of only 30 jumps/wk, the subjects in
jump groups were carefully instructed to jump regularly and with the
maximum voluntary effort, unless otherwise excluded from the jumping group. Three jumpers were then excluded from the exercise group
because they had not done enough jump training (9, 19, and 22 days
in 6 mo). In the control group, two subjects did not take the calcium
supplements regularly (0 and 65 days in 6 mo), although their calcium
intakes were well below the sufficient level, and one subject lost
interest in this study. Thirty-six healthy female college students
completed the study and were analyzed as subjects in this experiment.
Their mean age, height, and weight were 20.7 ⫾ 0.7 yr, 158.9 ⫾ 4.6
cm and 50.4 ⫾ 5.5 kg, respectively.
BMD and deoxypyridinoline measurements. Bone mineral density
(g/cm2) was assessed, using dual-energy X-ray absorptiometry
(ALOKA, DCS-3000), in the lumbar spine (L2– 4, anterior-posterior
view) and the right proximal femur. The femoral neck, Ward’s
triangle, and greater trochanter of the proximal femur were selected
for analysis according to the manufacturer’s software. The same
radiographer made the initial and final dual-energy X-ray absorptiometry measurements, and the groups (jumping or control) were
blinded. The coefficient of variation of the BMD measurement had an
in-house precision error of 1.0% based on the adult scans. We did not
estimate the coefficient of variation of the BMD measurement because
of the increased X-ray exposure to the young subjects (20 –23 yr). The
dual-energy X-ray absorptiometry machine was calibrated daily by
using a phantom calibration procedure, and there was no significant
drift during the study.
Deoxypyridinoline (DPD) is primarily located in bone collagen, and
urinary DPD has been used as one of the standard bone resorption
markers. Urine samples were collected between 9:30 and 11:30 AM on
both initial and final BMD measurement days and were frozen at ⫺60°
until assayed in a subsample of 20 volunteers (10 jumpers and 10
controls) who were able to attend the urine sample collection. The DPD
was measured with ELISA (SRL), and the subject groups were blinded
for the analysis. Urine DPD values were corrected for changes in urine
concentration by expressing them per millimole of creatinine.
Dietary calcium and supplementation. Subjects completed 3-day
weighted food records at baseline for providing a calcium supplementation to adjust the daily requirements, and also just before the
completion of the exercise intervention period. These records were
completed over 3 days: 2 weekdays and 1 weekend day. The diets
were analyzed by software (Eiyokun Ver. 3.0, Kenpakusha) that is
based on a standard food database. Calcium carbonate supplements
were given to 34 subjects (17 jumpers and 17 controls) as 300-mg
tablets and taken with meals to bring intakes over 650 mg/day of
elemental calcium, which exceeds the requirements for the recommended calcium allowances in Japanese adult women of this age (13).
Exercise program. The jump exercise group performed two-legged
maximum vertical jumps 10 times using an arm swing in counter-
841
JUMP TRAINING IN YOUNG WOMEN
Table 2. Initial and final measures of BMD
Jump (n ⫽ 18)
Lumbar spine*†
Total proximal femur
Femoral neck†
Ward’s triangle
Greater trochanter
Control (n ⫽ 18)
Initial
Final
Initial
Final
0.991⫾0.115‡
0.982⫾0.072
0.984⫾0.081‡
0.912⫾0.100
0.782⫾0.076
1.015⫾0.113‡
0.991⫾0.074
1.010⫾0.080‡
0.932⫾0.087
0.784⫾0.082
1.007⫾0.113
0.983⫾0.157
0.985⫾0.143
0.916⫾0.184
0.790⫾0.143
1.013⫾0.110
0.974⫾0.149
0.974⫾0.134
0.912⫾0.169
0.780⫾0.140
Values are means ⫾ SD in g/cm. BMD, bone mineral/density. *Significant difference within groups (P ⬍ 0.05). †Significant interaction (P ⬍ 0.05).
‡Significant difference between initial and final values (P ⬍ 0.01).
stimulus would appear similar even with fewer repetitions. The
loading interval may be another important factor associated
with mechanosensor sensitivity (20). A high strain rate may
enhance the mechanosensor’s less sensitive period and require
a longer recovery period (27). The interval of mechanical
loading in jogging or running may not be long enough to
recover its sensitivity, so the effectiveness of low-repetition,
maximum vertical jumps may have the same levels as training
with numerous loading repetitions.
High-impact jump training is reportedly effective for increasing bone mass and breaking force in animals (9, 10,
25–27) and also for increasing BMD in the human lumbar
spine (2, 6, 7) and femoral neck regions (1, 2, 6, 7). In human
jump training studies, 125–350 jumps/wk were reported to be
required as an effective stimulus for bone formation (1, 2, 6,
11, 24). In the present study, only 10 jumps/day, 30 jumps/wk
with maximum effort were demonstrated to be an effective
bone stimulus. Our results are consistent with those of Beverly
et al.’s (4) study. They reported that a relatively brief but
strenuous physical stress exercise resulted in increased BMC in
the stressed forearms. Squeezing a tennis ball with maximum
voluntary effort three times consecutively, morning and
evening, which took less than 30 s each day for 6 wk, produced
a 3.4% increase in BMC in the stressed forearms. It should be
noted that, in these studies, the levels of strain likely exceeded
those generated during typical human physical activities.
In human high-impact jump exercise studies, a 3.0 (young
adult) (2) to 8.8 (prepubertal) (6) times BW in GRF at landing
DISCUSSION
The most important observation made in the present study
was that jump training of 10 jumps/day, 30 jumps/wk significantly increased BMD at the femoral neck (P ⬍ 0.05), whereas
BMD in the control group remained unchanged after 6 mo of
exercise intervention. Other investigators have shown that
loading with many repetitions at one time had a relatively small
additional effect on bones compared with loading of only
10 – 40 repetitions (23, 26). After many repetitions of mechanical loading on bones, the mechanosensor might show decreased sensitivity (19, 20). Thus its effectiveness as a bone
J Appl Physiol • VOL
Fig. 1. Percentage change in bone mineral density (BMD) among 18 jumpers
and 18 controls who completed the 6-mo study. Bars show SE. ‡Significant
increase from the initial value (P ⬍ 0.01).
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After the 6 mo of exercise intervention, body weight (BW) was
significantly decreased within groups (P ⬍ 0.05) (Table 1).
The maximum vertical jump height was significantly improved
within groups (P ⬍ 0.05) (Table 1). The average vertical jump
height with the same measuring method in the similar age
group among Japanese women was 41.0 – 41.8 cm (17). Calcium intake and urinary DPD showed no significant differences
between and within groups (Table 1).
A two-way ANOVA with repeated measures revealed significant interactions (time ⫻ group) in BMD at the femoral
neck regions (P ⬍ 0.05) and at the lumbar spine (P ⬍ 0.05).
From the results of paired t-test, the jump group showed
significantly increased BMD at the femoral neck (P ⬍ 0.01)
and lumbar spine (P ⬍ 0.01), whereas the control group BMD
did not change significantly. No significant interactions or
main effects were observed at other measurement sites in either
jump or control groups: Ward’s triangle, greater trochanter,
and total proximal femur BMD. Mean percentage changes over
6 mo in BMD at the femoral neck and lumbar spine significantly increased in the jump group (P ⬍ 0.01)(Fig. 1).
BMC in lumbar spine in the jump group was initially
40.88 ⫾ 6.12 mg and finally 42.25 ⫾ 6.33 mg, whereas in the
control group BMC was initially 41.64 ⫾ 8.83 mg and finally
41.97 ⫾ 8.62 mg. Also, bone area (BA) in the jump group was
initially 41.18 ⫾ 2.67 cm2 and finally 41.54 ⫾ 2.95 cm2,
whereas in the control group BA was initially 41.00 ⫾ 4.45
cm2 and finally 41.14 ⫾ 4.50 cm2. A two-way ANOVA with
repeated measures revealed significant interactions (time ⫻
group) in BMC at the lumbar spine (P ⬍ 0.01). BA in the
lumbar spine was significantly increased within groups (P ⬍
0.05), but there was no significant difference between groups.
From the result of paired t-test, the jump group showed
significantly increased BMC at the lumbar spine (P ⬍ 0.01),
whereas the control group BMC did not change significantly.
Peak GRFs at takeoff and landing phases were 2.35 ⫾ 0.25
and 4.76 ⫾ 0.86 times BW, respectively.
842
JUMP TRAINING IN YOUNG WOMEN
J Appl Physiol • VOL
failure (64 –165%) in rats (21). Bone strength can be enhanced
substantially from small changes in BMD or BMC if the bone
is added to the mechanically appropriate sites. New bone
formation caused by mechanical loading was reported to be
strategically localized to the biomechanically relevant sites
(21). In humans, young adult jumpers (long-jump, high-jump,
triple-jump, and pole-vault athletes) showed a greater tibial
moment of inertia and strength strain index determined by
peripheral quantitative computed tomography than swimmers
and controls (16). In the present study, although the improvement of BMD was modest, low-repetition but high-impact
maximum vertical jumps would lead the effective bone formation to optimize the relevant bone sites.
There are, however, some limitations of the present study.
First, although an important issue, our study did not measure
strain in the proximal femur during the maximum vertical
jump. Bassey et al. (3) measured the compressive axial forces
in an instrumented massive femoral implant and observed that
the implant force at the hip was 2.60 –2.90 times the GRF
during takeoff and 1.37–1.47 times the GRF during landing in
relatively slow-tempo jumps. Theoretically, this result indicates that the compressive forces at the hip during takeoff and
landing in the maximum vertical jumps were comparable in the
present study.
Second, to clarify bone metabolism, DPD was measured as
the bone resorption marker in urinalysis, although we could not
measure bone formation markers such as osteocalcin, which
can only be analyzed through blood samples. However, the
increased BMD was not associated with increased remodeling,
because none of the DPD levels were changed in both jump
and control groups in the pre- and postexercise intervention
period. Raab-Cullen et al. (18) showed that external load works
by stimulation formation independent of resorption. They reported that the loading created a greater formation surface of
externally loaded legs than in nonloaded legs in rats.
In conclusion, the results of the present study indicate that
10 maximum vertical jumps/day, 3 days/wk enhanced BMD at
the femoral neck in young women who had almost reached the
age of peak bone mass. For practical applications, low-repetition high-impact jumps are suggested to be one of the ideal
training methods for enhancing and maintaining peak bone
mass in young adult women.
ACKNOWLEDGMENTS
We thank Kankichi Yokoyama and Junko Tabei for generous assistance and
Masaaki Taniguchi, Tomoaki Turuta, and Akie Fujii for help especially with
volunteer recruitment.
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