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Low bone mineral density in highly trained male master cyclists

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The purpose of this study was to determine total and regional bone mineral density (BMD) in highly competitive young adult and master male cyclists. Three groups of men were studied: older cyclists (51.2+/-5.3 years, n=27); young adult cyclists (31.7+/-3.5 years, n=16); and 24 non-athletes matched by age (+/-2 years) and body weight (+/-2 kg) to the master cyclists. All of the master cyclists had been training and racing for a minimum of 10 years (mean 20.2+/-8.4 years) and engaging in little to no weight-bearing exercise. The younger cyclists also engaged in little weight-bearing exercise and had been training and racing for 10.9+/-3.2 years. Age-matched controls were normally active. The History of Leisure Activity Questionnaire was used to determine the influence on BMD of self-reported total and weight-bearing exercise during three periods of life: 12-18 years, 19-34 years, and 35-49 years. BMD (measured by DXA) of the spine (L2-L4) and total hip was significantly (P<0.033) lower in the master cyclists compared to both age-matched controls and young adult cyclists. Total body BMD was lower in the master cyclists compared to the young-adults (P<0.033). Furthermore, four (15%) of the master cyclists, but none of the men in the other groups, had T-scores (spine and/or hip) lower than -2.5. Weight-bearing exercise performed during teen and young adult years did not appear to influence BMD, as there were no differences at any site between those within the upper and lower 50th percentiles for weight-bearing exercise during the 12-18, 19-34, or 35-49 year time periods. These data indicate that master cyclists with a long history of training exclusively in cycling have low BMD compared to their age-matched peers. Although highly trained and physically fit, these athletes may be at high risk for developing osteoporosis with advancing age.
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ORIGINAL ARTICLE
Low bone mineral density in highly trained male master cyclists
Jeanne F. Nichols Æ Jacob E. Palmer Æ Susan S. Levy
Received: 3 September 2002 / Accepted: 25 April 2003 / Published online: 11 July 2003
International Osteoporosis Foundation and National Osteoporosis Foundation 2003
Abstract The purpose of this study was to determine
total and regional bone mineral density (BMD) in
highly competitive young adult and master male cy-
clists. Three groups of men were studied: older cyclists
(51.2±5.3 years, n=27); young adult cyclists (31.7±3.5
years, n=16); and 24 non-athletes match ed by age
(±2 years) and body weight (±2 kg) to the master
cyclists. All of the master cyclists had been training and
racing for a minimum of 10 years (mean 20.2±8.4
years) and engaging in little to no weight-bearing
exercise. The younger cyclists also engaged in little
weight-bearing exercise and had been training and
racing for 10.9±3.2 years. Age-matched controls were
normally active. The History of Leisure Activity
Questionnaire was used to determine the influence on
BMD of self-reported total and weight-bearing exercise
during three periods of life: 12–18 years, 19–34 years,
and 35–49 years. BMD (measured by DXA) of the
spine (L2–L4) and total hip was significantly (P<0.033)
lower in the master cyclists compared to both age-
matched controls and young adult cyclists. Total body
BMD was lower in the master cyclists compared to the
young-adults (P<0.033). Furthermore, four (15%) of
the master cyclists, but none of the men in the other
groups, had T-scores (spine and/or hip) lower than –2.5.
Weight-bearing exercise performed during teen and
young adult years did not appear to influence BMD, as
there were no differences at any site between those
within the upper and lower 50th percentiles for weight-
bearing exercise during the 12–18, 19–34, or 35–49 year
time periods. These data indicate that master cyclists
with a long history of training exclusively in cycling
have low BMD compared to their age-matched peers.
Although highly trained and physically fit, these ath-
letes may be at high risk for developing osteoporosis
with advancing age.
Keywords Bicycling Æ Bone mass Æ Bone density Æ
DXA Æ Exercis e Æ Master athletes
Introduction
Osteoporosis has become a serious health problem in
many countries, and although more prevalent in women,
the incidence is rising in men [1]. Attainment of high
peak bone mass in young adulthood is a determinant of
bone mass later in life. In addition to genetic, hormonal
and nutritional influences, exercise positively affects
bone mass accretion during adolescence and is beneficial
in preserving bone mass throughout adult years [2,3,4].
Animal studies on the mechanisms by which bone
adapts to mechanical strain provide the basis for
understanding why various modes of exercise have dif-
ferential effects on bone [5]. That is, activities that pro-
duce high strain magnitudes and high strain rates
distributed unevenly across the bon e provide the greatest
osteogenic stimulus [6]. Furthermore, the degree of
mechanical strain applied to bone in weight-bearing
activities increases proportionally with increased ground
reaction forces [7]. Evidence from cross-sectional studies
of athletes from a variety of sports, including gymnas-
tics, volleyball, karate and running, supports the notion
that bone undergoes a positive adaptive response to high
impact activities [8,9,10]. Intervention studies, most of
which are reported for women, have shown increases in
bone mass induced by high strain activities such as
jumping and running in children [11] as well as older
adults [2]. In stark contrast, weightless environments
experienced by astronauts or individuals participating in
bed-rest studies cause rapid and marked bone loss
[12,13]. Similarly, non-weight-bearing activ ities such as
swimming and cycling afford few, if any, benefits to bone
health in young adults [14,15].
Much less is known regarding the long-term effects of
participation in various sports, although it is probable
that participation in weight-bearing activities throughout
Osteoporos Int (2003) 14: 644–649
DOI 10.1007/s00198-003-1418-z
J.F. Nichols (&) Æ J.E. Palmer Æ S.S. Levy
Department of Exercise & Nutritional Sciences,
San Diego State University,
San Diego, CA 92182-7251, USA
one’s lifetime reduces the risk of osteoporosis. Of con-
cern, however, is whether there are possible detrimental
effects to bone health from participating solely in non-
weight-bearing activities. Studies of master athletes from
various sports provide data that may help distinguish the
effects on BMD of age per se from those associated with a
decrease in exercise participation with advancing age.
Furthermore, knowledge of the apparent effects of life-
long participation in a particular activity can help
determine the benefits and/or risks of such participation.
Such studies may also guide health promotion practi-
tioners, coach es and exercise instructors in making
appropriate recommendations regarding the types of
physical activity that are most beneficial to bone health.
Our interest in the bone health of older athletes,
along with very limited published data for older male
athletes in general, and particularly for men participat-
ing in non-impact sports, prompted us to examine BMD
in master male cyclists. Therefore, the primary purpose
of this study was to determine and compare total body
and regional BMD in young adult and master cyclists
and in normally active men matched by age and body
weight to the older cyclists. We postulated that there
would be no differences in BMD of master cyclists
compared to age-matched non-athletes. A secondary
purpose was to determine the influence on BMD of
exercise participation during various stages of life. We
studied tw o groups of highly trained, competitive male
cyclists, aged 40–60, and 25–35 years, who had partici-
pated exclusively in the sport of cycling for a minimum
of 10 and 5 years, respectively.
Materials and methods
Subjects
Potential participants were recruited via announcements in news-
letters and on web pages of masters racing clubs in southern Cal-
ifornia. Twenty-seven male master cyclists, 16 young adult male
cyclists and 24 non-athletic male controls volunteered to serve as
subjects. All subjects completed a health history questionnaire to
screen for conditions and medications known to affect bone health.
Individuals were excluded from the study if they were taking, or
had ever taken medications or had any condition known to affect
bone mass and/or bone metabolism, including: inhaled steroids,
anticonvulsants, calcitonin, alendronate, thyroid hormone, corti-
costeroids, cyclosporine, and anabolic steroids; thyroid or para-
thyroid disease; adrenal gland problems. Additionally, cyclists who
participated in regular (2 or more days per week for more than 3
months per year), weight lifting, body-building, and/or any impact
exercise were not eligible to participate. These exercise exclusion
criteria had to be met for at least the past 10 years for master
cyclists, and 5 years for the young adult cyclists. Other exclusion
criteria included past or present smoking (more than 3 years) and
heavy (>2 drinks per day) alcohol use.
Inclusion criteria for the master cyclists included: age 40–60
years; year-round training consistently at least 150 miles per week
or a minimum of 10 h per week for a minimum of 10 years; com-
peting in USCF (United States Cycling Federation) races for a
minimum of 10 years. Young adult cyclists between 25 and 35 years
of age were recruited to compare age differences within this pop-
ulation of athletes. Inclusion criteria for the young adult cyclists
included training and racing profiles similar to those of the masters,
with the exception of a minimum of 5 years in competition. Non-
athletic, but otherwise healthy men were recruited to serve as a
comparison group to the master athletes. These control subjects
were non-smokers who met the same inclusion criteria specific to
medication use. They were excluded from the study if they engaged
in regular (2 or more days per week) weight training and/or com-
petition in any sport; however, recreational exercisers were not
excluded from participating. The non-athletes were matched to the
master cyclists by age (±2 years) and body weight (±2 kg).
The study was approved by the University’s Institutional
Review Board, and all subjects gave written, informed consent to
participate.
Bone density measurements
Bone mineral density (BMD, g/cm
2
) of the lumbar spine (L2–L4),
proximal femur, and total body was assessed by dual energy X-ray
absorptiometry (DXA) using a Lunar DPX-NT densitometer (GE/
Lunar Corp, Software Version 4.0). Soft tissue mass was also ob-
tained from the total body scan to determine body composition. All
scans were conducted by the same technologist. Quality assurance
(QA) tests were performed each morning of use, using a standard
with tissue-equivalent material with three bone-simulating cham-
bers of known bone mineral content. In vivo BMD precision in our
laboratory is 0.6–1.2% for the spine, 0.6–1.7% for total hip, and
0.6–0.8% for total body.
Lifetime physical activity
The Historical Leisure Activity Questionnaire [16] was used to
assess participation in total and weight-bearing physical activity
during three different stages of life (age 12–18, 19–34, and 35–49
years) in the master cyclists and non-athletes only. This question-
naire has moderate to good reliability when self-administered [17].
To maximize subjects’ ability to accurately and reliably recall
exercise participation, a trained interviewer used a standardized
script to cue subjects in recalling participation in activities for each
life stage. Subjects were asked to recall the number of months per
year and hours per week in structured and unstructured sports and
activities during these three periods of life. The subjects first re-
corded from a checklist any organized sport, e.g. school or com-
munity teams, in which they participated, then asked to recall and
check any unstructured activities they did at least 1 day per week.
For analysis, activities were categorized as weight-bearing,
e.g. running, tennis, basketball, baseball, or non-weight-bearing.
The non-weight-bearing activities most frequently reported were
swimming, fishing and cycling. Data are reported for weight-
bearing and total physical activity per time period.
Training regimen (athletes)
The cyclists recorded their training regimen for a typical week
during the competitive season. Since, by design, athletes were ex-
cluded if they participated in weight-bearing activities 2 or more
days per week, they were asked only to record their cycle training
regimens. Most of the athletes kept training diaries and referred to
them for these data. They recorded the number of days per week
and hours per day spent riding.
Current exercise
The non-athletes were asked to report for a typical week all rec-
reational exercise they performed 2 or more days per week at
moderate or vigorous intensity for at least 20 min at a time (cyclists
were excluded if they engaged in other sports 2 or more days per
week). They recorded the number of days per week and minutes per
session for each activity. Separate questions were asked of all
subjects for current participation in weight lifting/strength training
645
for both the upper and lower body musculature. Participants re-
corded the number of months per year and days per week they
typically lifted weights. The cyclists who engaged in weight training
up to 3 months per year (excluded from study if >3 months per
year) were asked whether this was typical of their annual training
program. In addition, all subjects were asked to report (yes/no) if
their jobs required heavy physical labor.
Statistical analysis
Data were analyzed using the Statistical Package for the Social
Sciences (SPSS) software (Chicago, Ill., USA, version 10.0). Sep-
arate one-way ANOVAs were used to compare the three study
groups for bone mineral density at the lumbar spine, hip and total
body, as well as all physical characteristics. Post hoc Tukey’s HSD
tests were used to determine the source of any significant effects.
Bivariate correlations were performed on variables of interest.
Separate 2 (master cyclists/non-athletes)·2 (high/low) ANOVAs
were conducted to examine the effect of cycling status and weight-
bearing and total exercise history on BMD. High and low cate-
gories were designated as the upper and lower 50% of weight-
bearing alone and total exercise hours for three different stages of
life: teen (12–18 years); young adult (19–34 years); adult (35–49
years). The initial alpha level was set to 0.10, as the study was
considered exploratory in this population and minimal risk was
involved in participation, and to increase the power to detect what
might be small effect sizes due to the limitations on sample size
caused by inclusion criteria. Alpha was then adjusted using the
Bonferroni method for the multiple comparisons of BMD by
anatomical site (three sites) and for the three life stages. Thus, the
adjusted level of significance was P<0.033.
Results
Among the cyclists were regional, national and inter-
national competitors, several of whom were age-group
national (n=5) and world champions (n=1). The
physical characteristics and training history of the sub-
jects are shown in Table 1. By design, there were no
differences between the master cyclists and non-athletes
in age or body weight; there were also no differences in
body weight between young and older cyclists. Per-
centage of body fat was lower, while lean tissue mass
was greater in both groups of cyclists compared to non-
athletes (P<0.033). The master cyclists reported
12.1±3.9 h (mean±SD) of training per week, which
was significantly lower than that reported by the youn-
ger cyclists. Other than weight lifting in the off-season (3
months), none of the master cyclists participated in any
sport other than cycling. The non-athletes reported a
mean of 4.5±1.4 days/week and 4.5±2.6 h/week of
regular recreational exercise, in addition to weight/
resistance exercises. The types of exercise reported most
frequently by the non-athletes, in order of most to least
frequent, were jogging/running, hiking, cycling, swim-
ming and tennis. By design, none of the non-athletes was
involved in training for competition. Eleven non-ath-
letes, 11 master cyclists and nine young cyclists reported
engaging in weight training. The non-athletes ranged
from 2 to 12 months per year (mean 9.8 months), while
both groups of cyclists trained two to 3 months per year.
In addition, one non-athlete and four cyclists (three
young; one master) reported doing heavy physical labor
in their jobs (con struction and landscape work).
Group mean (±SD) BMD values for the lumbar spine
(L2–L4), total hip, femoral neck, trochanter, and total
body are reported in Table 2. One-way ANOVAs with
Tukey post-hoc tests indicated that the master cyclists
had significantly lower BMD at L2–L4 and total hip
compared to both the non-athletes (L2–L4, P=0.032;
hip, P=0.026) and younger cyclists (L2–L4, P=0.032;
hip, P=0.005). The trochanteric region of the hip showed
a strong trend (P=0.06) toward lower BMD in the master
athletes compared to non-athletes. The master cyclists
also had lowe r trochanteric, femoral neck, and total body
BMD (P<0.033) than the young adult cyclists. Both total
and regional BMD were similar in the non-athletes and
young adult cyclists. The T-scores of the younger cyclists
indicated that their total body BMD wa s 3% higher,
while BMD of the spine was approximately 3% lower
than that of the age-matched reference population
(Lunar/GE data base). Total hip BMD of the younger
cyclists was similar to the reference values for men.
Chi-square analysis comparing the percentage of
master cyclists and non-athletes classified at risk (i.e.
osteopenia/osteoporosis: T-scores of –1 SD or below the
young peak reference value at each of the three mea-
surement sites) revealed a significantly greater incidence
of osteopenia/osteoporosis at both the spine (P<0.025)
and hip (P<0.02) in the master cyclists (Fig. 1). Two-
thirds of the master cyclists met the criteria for oste-
openia/osteoporosis at the spine, while 63% met the
criteria at the hip. An examination of T-scores further
indicated that four of the master cyclists were classified
as osteoporotic. Among the non-athletes, 42% and 33%
were classified as osteopenic at the spine and hip,
respectively, while non e was osteoporotic. Although the
percentages for total body BMD were not significantly
Table 1 Physical characteristics
and training history of subjects.
Values are group mean±SD
*P<0.033 compared to non-
athletes;
++
P<0.033 com-
pared to young adult cyclists.
ANOVAs with Tukey post-hoc
tests were used to compare the
three groups
a
Body composition determined
by DXA
Young adult cyclists (n=16) Master cyclists (n=27) Non-athletes (n=24)
Age (years) 31.7±3.5 51.82±5.1 51.6±4.7
Height (cm) 176.7±6.4 178.4±5.2 175.7±6.5
Weight (kg) 73.1±9.2 71.9±6.4 73.8±8.8
Body fat (%)
a
15.3±5.9* 13.9±4.1* 22.2±5.4
Lean tissue mass (kg)
a
58.7±5.2* 59.9±5.4* 54.4±5.9
Years of cycling 10.9±3.2 20.2±8.4
++
N/A
Training regimen (cyclists); recreational exercise (non-athletes)
Days per week 5.5±0.8 4.7±1.3 4.5±1.4
Hours per week 15.8±3.8 12.1±3.9
++
4.5±2.6
646
different between the master cyclists and non-athletes,
41% of the cyclists were classified as osteopenic/osteo-
porotic, while 21% of the non-athletes met the criteria
for osteopenia. Results from the History of Leisure
Activity questionnaire are presented in Table 3. Differ-
ences in self-reported hours of weight-bearing and total
exercise between master cyclists and non-athletes were
not significant for the 12–18 or 19–34 year time periods.
From age 35–49, when they were devoting more ti me to
cycling, the master cyclists engaged in nearly twice as
much total exercise as the non-athletes (P<0.001).
Table 4 shows the mean±SD BMD of the master
cyclists and non-athletes grouped by the upper and
lower 50th percentiles for weight-bearing exercise during
each of the three life stages. When divided into these
‘‘high’’ and ‘‘low’’ categories for weight-bearing exercise,
separate 2·2 ANOVAs yielded no significant interac-
tions between cycling status and weight-bearing exercise
at any stage of life at each BMD measurement site
(P>0.033).
Discussion
Compared to the non-athletes in this study, as well as to
the reference group of age-matched men (GE/Lunar
Fig. 1 Percentage of participants within each group classified as
osteopenic/osteoporotic. *P=0.023 (spine); P=0.01 (hip) com-
pared to non-athletes
Table 3 Group mean±SD of hours per week of historical physical activity of master cyclists and non-athletes. Data are reported for the
three life stages indicated in the History of Leisure Activities Questionnaire
Age 12–18 Age 19–34 Age 35–49
Weight-bearing
exercise (h/week)
Total exercise
(h/week)
Weight-bearing
exercise (h/week)
Total exercise
(h/week)
Weight-bearing
exercise (h/week)
Total exercise
(h/week)
Master cyclists 3.9±4.6 6.4±6.4 3.2±3.9 7.0±7.4 3.3±4.9 14.1±7.8*
Non-athletes 4.9±4.2 6.6±5.9 4.4±2.6 5.7±3.8 5.3±3.9 7.5±4.5
*P<0.001 compared to non-athletes
Table 2 Bone mineral density (g/cm
2
) of subjects. Values are group mean±SD. ANOVAs with Tukey post-hoc tests were used to compare
the three groups
Young adult cyclists (n=16) Master cyclists (n=27) Non-athletes (n=24)
Lumbar spine (L2–L4) 1.20±0.13 1.07±0.15* 1.19±0.19
Total hip 1.10±0.16 0.93±0.11* 1.05±0.18
Femoral neck 1.05±0.18 0.91±0.18
++
0.99±0.16
Trochanter 0.91±0.15 0.79±0.11
++
0.89±0.18
Total body 1.26±0.10 1.16±0.09
++
1.22±0.11
*Master cyclists significantly lower than non-athletes and young adult cyclists (P<0.033)
++
Master cyclists significantly lower than young adult cyclists (P<0.033)
Table 4 BMD of master cyclists and non-athletes grouped by upper and lower 50th percentiles for weight-bearing exercise. Values are
group mean±SD expressed in g/cm
2
Age 12–18 Age 19–34 Age 35–49
High
a
Low
a
High
a
Low
a
High
a
Low
a
Lumbar spine Master cyclists 1.05±0.15 1.08±0.17 1.02±0.14 1.12±0.17 1.07±0.19 1.07±0.13
Non-athletes 1.18±0.22 1.17±0.18 1.12±0.18 1.22±0.20 1.12±0.19 1.22±0.20
Total hip Master cyclists 0.93±0.11 0.96±0.12 0.93±0.12 0.96±0.12 0.95±0.12 0.94±0.12
Non-athletes 1.07±0.22 1.01±0.17 1.02±0.21 1.06±0.18 0.98±0.20 1.10±0.17
Total body Master cyclists 1.17±0.09 1.18±0.09 1.16±0.09 1.19±0.09 1.17±0.09 1.17±0.09
Non-athletes 1.21±0.14 1.23±0.08 1.20±0.12 1.24±0.10 1.19±0.12 1.25±0.09
a
High and Low refer to upper and lower 50th percentiles, respectively, for weight-bearing activity
647
data base), the bone mass of the master cyclists was
approximately 10% lower at both the proximal femur
and the lumbar spi ne. The group mean T-scores of the
non-athletes indicated that since achieving peak bone
mass their BMD had declined, in theory, by approxi-
mately 4% at the hip and spine, with no decrease in the
total body. Z-Scores of the non-athletes indicated that
their spine, hip and total body BMD was 99%, 103%
and 102%, respectively, of that of their peers matched
for age, weight, height and ethnicity. Thus, as a group
the non-athletes appear to be fairly representative of the
population. However, according to self-reported physi-
cal activity, the non-athletes are more active than the
literature suggests is typical for their age, and none re-
ported a sedentary lifestyle. Although they were not
currently competitive athletes, many had participated in
organized sports during high school and beyond. Still,
ten of the non-athletes had BMD T-scores between )1
and )2.0 SD at the spine and/or hip. This is puzzling,
but may be associated with their low body weight. Body
weight was moderately related to BMD (r=0.37 for
spine and hip; r=0.50 for total body); however, there
were no group differences in body weight. Thus, al-
though body weight likely contributes to the low BMD
of some of the non-athletes, it does not explain the
group differences between them and the cyclists.
Peak muscular force is the primary external stimulus
for postnatal bone mass accreti on [18]. The pull of
muscle at its attachment site momentarily bends the
bone; the resultant strain is the stimulus for new bone.
Sports involving large ground reaction force loading, as
in jumping and landing [9], or large dynamic muscle/
joint reaction forces, such as those associated with lifting
heavy weights [10], produce the greatest osteo genic
stimulus. As shown from animal studies, high magni-
tude, high rate, and irregular distribution of strain ap-
pear to play the largest role in the stimulus of new bon e
production [5]. Unlike sports such as volleyball or ten-
nis/squash, in which bone undergoes uneven distribution
of high magnitude strain at high frequency [9,19], the
relatively fixed body position while riding a bicycle in-
duces a repetitive muscular strain pattern of relatively
low magnitude and regular or even distribution. Thus, it
is possible that cycling provides a rather poor osteogenic
stimulus due to both the biomechanics of the sport as
well as its lack of impact.
To our knowledge, this is the first report of bone
mass in master cyclists, all of whom had been training
and racing for an average of 20 years and had engaged in
little to no weight-bearing activity. When compared to
healthy men matched for age and body weight, the older
cyclists in the present study had lowe r BMD at both the
hip and spine. Oth er factors known to affect BMD ,
including smoking, alcohol consumption and certain
medications and medical conditions were controlled by
initial screening. Thus, the group differences in BMD are
more likely due to differences in exercise patterns during
their adult years. Previous studies of adult athletes have
shown that other non-impact sports, even if performed
vigorously, do not provide an osteogenic stimulus
[10,14]. However, total and regional bone mass of
competitive mountain cyclists, due perhaps to the im-
pact of riding on rough terrain, was recently reported to
be significantly higher than that of young adult road
cyclists [20].
We used the History of Leisure Activities question-
naire [16] to gain a better understanding of the influence
on BMD of physical activity during different periods in
life. With these data, we investigated the intera ction
between current BMD and self-reported total and
weight-bearing activity during different periods of life,
specifically, age 12–18, 19–34, and 35–49 years. Previous
research has shown that exercise during youth is asso-
ciated wi th higher adult bone mass [4]. However, among
the master cyclists and non-athletes, there were no sig-
nificant within group differences in BMD in those within
the upper versus lower 50th percentiles for weight-
bearing exercise at each stage of life. Moreover, there
were no significant interaction effects between groups
and weight-bearing activity at any stage of life for an y
skeletal site. Thus, impact exercise during youth and
earlier adult years was not reflective of greater BMD in
this small sample of middle-aged athletic men. We
speculate whether BM D may be declining at a faster rate
during their older adult years. It is possible that the
observed difference in bone mass between these two
groups matched for age and body weight is due to the
very little time spent in weight-bearing activity since age
35. Longitudinal data are needed to determine the rate
of bone loss in this athletic population.
It is possible that the cumulative effect of the large
percentage of waking hours spent by the master cyclists
in activities in which their body weight was supported
had an effect on the remodeling of bone. These athletes
had been cycle training consistently for approximately
20 years, with very little time reported for weight-bear-
ing activity, especially during middle age. The cumula-
tive effect of their lifestyle may be compared to shorter
periods of skeletal un-weighting, such as that shown in
bed rest studies [13]. Some of the master athletes re-
ported up to 30 h per week on their bikes.
Anecdotally, cyclists are known to avoid unnecessary
weight-bearing activity during heavy training periods.
Thus, although not directly assessed, it is likely that the
master cyclists spend little time on their feet. Wit h such a
large training volume, much additional waking time
must be spent resting and recovering. An old saying
from the Tour de France is often quoted by coaches and
practiced by many highly competitive cyclists: ‘‘If you
are not riding, you should be resting, if you do not have
to stand, you should sit, if you do not have to sit, you
should lie down.’’
Using the World Health Organization’s criteria for
osteoporosis in women (T-score at or below –2.5 SD
below peak young-adult BMD) and osteopenia (T-score
between –1 and –2.5), 67% of the master cyclists would
be classified as either osteopenic (52%) or osteoporotic
(15%) at either or both the spine and hip. Ten non-
648
athletes (42%) would be classified as osteopenic, while
none was osteoporotic. In addition, four (25%) young
adult cyclists would be classified as osteopenic in the
lumbar spine. This latter finding is alarming, especially
in light of the fact that at least one other study reported
low spinal BMD in cyclists of similar age, body weight,
and training regimen [14].
Although cross-sectional in design and therefore not
able to establish a causal rela tionship, the present study
provides evidence that long-term participation solely in
cycling, with little to no participation in impact or resis-
tance activities may be detrimental to bone health in later
years. Given the findings in this study, coupled with the
high risk of fractures due to crashes associated with
competitive cycling, we recommend that: (1) these
athletes be screened periodically to determine their
BMD; (2) supplement their cycling with resistance or
impact exercise; (3) consume a balanced diet with
adequate intake of calcium and vitamin D. Those at high
risk for fractures, as recognized by low T-scores, should
discuss possible pharmacological treatment with their
physicians.
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... Similar to female athletes, 86,87 impaired bone health and a higher risk of BSI have been reported among male athletes engaged in sports emphasizing leanness. 88,89 Low bone mineral density (BMD) has been reported in distance runners [90][91][92][93][94] and in athletes engaged in sports associated with low-impact loading patterns, such as cyclists, [95][96][97][98] jockeys, 99-101 and swimmers. 102,103 This correlates well with sports demonstrating higher rates of energy deficiency/low EA among male athletes. ...
... and previous stress fracture. 91 Of note, evidence available for poor bone health in male athletes is largely limited to cross-sectional studies, [90][91][92]96,[98][99][100][101][104][105][106][107][108][109] case series, 110 and a few prospective observational studies. 88,94,95,97,111,112 Evidence Level B. Numerous prospective observational studies, cross-sectional studies, and case series have provided evidence for impaired bone health and higher risk of BSI among male athletes engaged in sports emphasizing leanness. ...
... A large proportion of lean-sport athletes meet criteria for low BMD. [90][91][92][93]95,96,98,99,101,106,107 For example, 20 to 30 years old elite long-distance runners have lower spine and hip BMD compared with soccer players and lower spine BMD compared with nonathlete controls. 90 Similarly, male adolescent endurance runners have lower spine BMD Z-scores compared with athletes participating in ball or power sports. ...
Article
Full-text available
The Male Athlete Triad is a syndrome of 3 interrelated conditions most common in adolescent and young adult male endurance and weight-class athletes and includes the clinically relevant outcomes of (1) energy deficiency/low energy availability (EA) with or without disordered eating/eating disorders, (2) functional hypothalamic hypogonadism, and (3) osteoporosis or low bone mineral density with or without bone stress injury (BSI). The causal role of low EA in the modulation of reproductive function and skeletal health in the male athlete reinforces the notion that skeletal health and reproductive outcomes are the primary clinical concerns. At present, the specific intermediate subclinical outcomes are less clearly defined in male athletes than those in female athletes and are represented as subtle alterations in the hypothalamic-pituitary-gonadal axis and increased risk for BSI. The degree of energy deficiency/low EA associated with such alterations remains unclear. However, available data suggest a more severe energy deficiency/low EA state is needed to affect reproductive and skeletal health in the Male Athlete Triad than in the Female Athlete Triad. Additional research is needed to further clarify and quantify this association. The Female and Male Athlete Triad Coalition Consensus Statements include evidence statements developed after a roundtable of experts held in conjunction with the American College of Sports Medicine 64th Annual Meeting in Denver, Colorado, in 2017 and are in 2 parts-Part I: Definition and Scientific Basis and Part 2: The Male Athlete Triad: Diagnosis, Treatment, and Return-to-Play. In this first article, we discuss the scientific evidence to support the Male Athlete Triad model.
... Cycling is a sport where some low carbohydrate and energy dietary strategies are used [20] which, combined with the high volumes and intensity in training and competition and influenced by non-impact physical activity [21], can promote bone resorption mechanisms that exceed those of synthesis. Due to these factors that influence cycling, we believe that research should be carried out into whether any bone pathology (osteopenia or osteoporosis) really exists in different cohorts of cyclists (PRO and AMA). ...
... We found that all our PRO cyclists were below this value (0.911 ± 0.061 g/cm 2 , − 2.1 to − 21.3% with respect to normal values), and in AMA, there were 7 out of the 15 cyclists below the normal value for BMD (1.052 ± 0.079 g/cm 2 , − 9.1 to +15.2% with respect to normal values). These inferior values concur with the low BMD values observed in elite and master cyclists (highly trained males) [21,30] and are most likely explained by the nature of cycling which elicits low impact forces on the bone. Many authors have studied the relationship between cycling and bone health and have found lower BMD of the lumbar spine in PRO compared to a control group [31], as well as lower BMD of the femoral neck and lumbar spine compared to healthy males [30]. ...
Article
Currently, there are no studies that compares bone condition markers between professional (PRO) and amateur (AMA) cyclists. Amateur cyclists are the ones who practice this sport the most. Therefore, there is an interest in behaving if there is a negative effect at the bone level could be similar than previously described in professional cyclists. The aim of this study was to identify the differences in bone level between professional and amateur road cyclists, and to see if the differences found are related to differences in performance. A parallel trial was carried out with 15 AMA and 10 PRO cyclists. All cyclists performed 2 visits: 1) in a fasted state, body composition with measured by densitometry (DEXA) was analyzed and 2) physiological variables were measured using an incremental test until exhaustion. Significantly lower values were found in bone mineral density, bone mineral content and fat free mass in PRO compared to AMA (p<0.05). In addition, significantly higher power produced in ventilatory thresholds 1 and 2 (VT1 and VT2) and VO2MAX were found in PRO compared to AMA (p<0.05). PRO cyclists present lower values in bone health and muscle mass markers but better results in performance compared to AMA.
... PTH is thought to increase during high-intensity exercise (reviewed in [100]). Although exercise is thought to be beneficial for BMD, some groups of professional athletes have had significant reductions in BMD [101,102]. It has been suggested that intense exercise leads to a decrease in calcium levels, resulting in an increase in PTH. ...
Article
Full-text available
Abstract: Calciotropic hormones, parathyroid hormone (PTH) and calcitonin are involved in the regulation of bone mineral metabolism and maintenance of calcium and phosphate homeostasis in the body. Therefore, an understanding of environmental and genetic factors influencing PTH and calcitonin levels is crucial. Genetic factors are estimated to account for 60% of variations in PTH levels, while the genetic background of interindividual calcitonin variations has not yet been studied. In this review, we analyzed the literature discussing the influence of environmental factors (lifestyle factors and pollutants) on PTH and calcitonin levels. Among lifestyle factors, smoking, body mass index (BMI), diet, alcohol, and exercise were analyzed; among pollutants, heavy metals and chemicals were analyzed. Lifestyle factors that showed the clearest association with PTH levels were smoking, BMI, exercise, and micronutrients taken from the diet (vitamin D and calcium). Smoking, vitamin D, and calcium intake led to a decrease in PTH levels, while higher BMI and exercise led to an increase in PTH levels. In terms of pollutants, exposure to cadmium led to a decrease in PTH levels, while exposure to lead increased PTH levels. Several studies have investigated the effect of chemicals on PTH levels in humans. Compared to PTH studies, a smaller number of studies analyzed the influence of environmental factors on calcitonin levels, which gives great variability in results. Only a few studies have analyzed the influence of pollutants on calcitonin levels in humans. The lifestyle factor with the clearest relationship with calcitonin was smoking (smokers had increased calcitonin levels). Given the importance of PTH and calcitonin in maintaining calcium and phosphate homeostasis and bone mineral metabolism, additional studies on the influence of environmental factors that could affect PTH and calcitonin levels are crucial.
... Bones are responsive to exercise [108], which is primarily thought to be through mechanical effects. Rapid running and jumping elicits larger strains and strain rates than static exercises [109], and power athletes have stronger leg bones than endurance athletes [110][111][112]. The largest effects have been observed for the humerus, the structure of which can be twice as strong in tennis and baseball players in the active as compared in the passive arm [113,114]. ...
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Regular physical exercise and a healthy diet are major determinants of a healthy lifespan. Although aging is associated with declining endurance performance and muscle function, these components can favorably be modified by regular physical activity and especially by exercise training at all ages in both sexes. In addition, age-related changes in body composition and metabolism, which affect even highly trained masters athletes, can in part be compensated for by higher exercise metabolic efficiency in active individuals. Accordingly, masters athletes are often considered as a role model for healthy aging and their physical capacities are an impressive example of what is possible in aging individuals. In the present review, we first discuss physiological changes, performance and trainability of older athletes with a focus on sex differences. Second, we describe the most important hormonal alterations occurring during aging pertaining regulation of appetite, glucose homeostasis and energy expenditure and the modulatory role of exercise training. The third part highlights nutritional aspects that may support health and physical performance for older athletes. Key nutrition-related concerns include the need for adequate energy and protein intake for preventing low bone and muscle mass and a higher demand for specific nutrients (e.g., vitamin D and probiotics) that may reduce the infection burden in masters athletes. Fourth, we present important research findings on the association between exercise, nutrition and the microbiota, which represents a rapidly developing field in sports nutrition.
... higher BMD(Rector et al., 2008;Fehling et al., 1995;Nichols et al., 2003;Stewart and Hannan, 2000;Sabo et al., 1996;Warner et al., 2002;Heinonen et al., 1993).Athletes who participated in sports that apply high impact loads on the skeleton such as gymnastics, volleyball and soccer have a higher BMD and stronger skeleton compared to controls(Orwoll et al., 2009). MoreoverCreighton et al. (2001) found that athletes who participated in sports that apply the highest impact loads on the skeleton (such as basketball and volleyball) have the highest BMD and the highest markers of bone formation compared to athletes who participated in sports that apply moderate impact load on the skeleton (such as soccer and track) and to athletes that participated in non-bearing activities (such as swimming) and sedentary controls. ...
Thesis
The aim of this PhD thesis were to explore the relationships between several physical performance variables and bone parameters in a group of middle-aged men, to compare composite indices of femoral neck strength in inactive middle-aged men and ages-matched former football players and to explore the effects of a 1-year recreational football protocol on bone mineral density and physical performance parameters in a group of healthy inactive 50-year-old men. Three main studies have been conducted. The first study has shown that VO₂ max (L/min), lean mass and maximum power of the lower limbs are the strongest determinants of bone variables in middle-aged men. The second study has shown that former footbal practice is associated with higher composite indices of femoral neck strength in middle-aged men. The third study has demonstrated that WB BMC, FN BMD, CSMI, CSI, BSI and ISI increased in both experimental groups (RF30 and RF60) but not in the control group. The percentages of variations in bone health parameters and in physical performance variables were not significantly different in both experimental groups. Recreational football is an effective method to improve bone health in middle-aged men.
Thesis
Full-text available
Le but principal de cette thèse était d’explorer les relations entre les performances obtenues aux tests physiques anaérobies et la densité minérale osseuse chez l’adulte jeune. Pour ce faire, 3 études préliminaires et deux études principales ont été menées. La première étude préliminaire a démontré que la consommation maximale d’oxygène (L/min) est un déterminant important de la DMO chez les jeunes adultes. La deuxième étude préliminaire a démontré que le fait d’être actif (pratiquer plus de 150 minutes d’activité physique par semaine) est associé à une augmentation des valeurs de CSI, de BSI et d’ISI chez les jeunes hommes en surpoids. La troisième étude préliminaire a démontré chez des jeunes hommes en surpoids et obèses que le niveau d’activité physique est un déterminant positif des indices de résistance osseuse du col fémoral (CSI, BSI et ISI) ; les corrélations positives entre le niveau d’activité physique et les indices de résistance osseuse du col fémoral (CSI, BSI et ISI) ont persisté après ajustement pour le poids. La première étude principale a démontré que la puissance maximale des membres évaluée par le test de détente verticale est corrélée positivement à la DMO et aux indices géométriques de résistance osseuse de la hanche chez les jeunes adultes. La deuxième étude principale a démontré que la puissance maximale évaluée par le test de charge-vitesse sur bicyclette ergométrique est corrélée positivement à la DMO chez les hommes mais pas chez les femmes. La performance au 20 mètres sprint était corrélée à la DMO du col fémoral chez les hommes. En conclusion de cette thèse, il apparait que les performances obtenues aux tests physiques évaluant la puissance musculaire sont corrélables à la DMO chez l’adulte jeune.
Article
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The Male Athlete Triad is a medical syndrome most common in adolescent and young adult male athletes in sports that emphasize a lean physique, especially endurance and weight-class athletes. The 3 interrelated conditions of the Male Athlete Triad occur on spectrums of energy deficiency/low energy availability (EA), suppression of the hypothalamic-pituitary-gonadal axis, and impaired bone health, ranging from optimal health to clinically relevant outcomes of energy deficiency/low EA with or without disordered eating or eating disorder, functional hypogonadotropic hypogonadism, and osteoporosis or low bone mineral density with or without bone stress injury (BSI). Because of the importance of bone mass acquisition and health concerns in adolescence, screening is recommended during this time period in the at-risk male athlete. Diagnosis of the Male Athlete Triad is best accomplished by a multidisciplinary medical team. Clearance and return-to-play guidelines are recommended to optimize prevention and treatment. Evidence-based risk assessment protocols for the male athlete at risk for the Male Athlete Triad have been shown to be predictive for BSI and impaired bone health and should be encouraged. Improving energetic status through optimal fueling is the mainstay of treatment. A Roundtable on the Male Athlete Triad was convened by the Female and Male Athlete Triad Coalition in conjunction with the 64th Annual Meeting of the American College of Sports Medicine in Denver, Colorado, in May of 2017. In this second article, the latest clinical research to support current models of screening, diagnosis, and management for at-risk male athlete is reviewed with evidence-based recommendations.
Article
Relative energy deficiency in sport (RED-S) is a constellation of clinical findings related to low energy availability. Manifestations are variable but may include endocrine and reproductive dysfunction, impaired bone and muscle health, psychological complaints, and performance issues, among many others. Unlike the previously common terminology, the female athlete triad, RED-S encompasses a broader range of signs and symptoms and includes descriptions for the male athlete. Since first being described in 2014 by the International Olympic Committee, an abundance of research has sought to define, prevent, and treat the underlying condition of RED-S. Although medicine, and society in general, has tried to expose the hazardous training and lifestyle behaviors that can underpin RED-S, further research and education is required on the part of the clinician and athlete to reshape the culture and prevent the deleterious consequences of low energy availability.
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The in vivo remodeling behavior within a bone protected from natural loading was modified over an 8-week period by daily application of 100 consecutive 1 Hz load cycles engendering strains within the bone tissue of physiological rate and magnitude. This load regime resulted in a graded dose:response relationship between the peak strain magnitude and change in the mass of bone tissue present. Peak longitudinal strains below 0.001 were associated with bone loss which was achieved by increased remodeling activity, endosteal resorption, and increased intra-cortical porosis. Peak strains above 0.001 were associated with little change in intra-cortical remodeling activity but substantial periosteal and endosteal new bone formation.
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Recent epidemiologic evidence suggests that lifetime physical activity is an important factor in the development of many chronic diseases. The authors assessed the reproducibility of a self-administered physical activity questionnaire designed to assess the duration, frequency, and intensity of lifetime household and recreational activities. The study was conducted among 134 female college alumnae from two colleges in western Massachusetts who were aged 39-65 years in 1998. A modified version of the Historical Leisure Activity Questionnaire was used to assess physical activity over four prior age periods (menarche to 21 years and 22-34, 35-50, and 51-65 years). The questionnaire was administered to participants by mail twice 1 year apart. The intraclass correlation coefficients used to measure reproducibility were 0.82 for total lifetime physical activity, 0.80 for lifetime moderate-intensity activities, 0.86 for lifetime vigorous-intensity activities, 0.87 for lifetime recreational activities, and 0.78 for lifetime household activities. Correlations were 0.73 for total activity during the earliest prior age period (menarche to 21 years), 0.70 for ages 22-34 years, 0.78 for ages 35-50 years, and 0.83 for ages 51-65 years. These data indicate that this physical activity questionnaire is reproducible and provides a useful measure of average lifetime activity.
Article
The purpose of this work was to determine the rate and extent of bone loss and recovery from long-term disuse and in particular from disuse after exposure to weightlessness. For this purpose, bed rest is used to simulate the reduced stress and strain on the skeleton. This study reports on the bone loss and recovery after 17 weeks of continuous bed rest and 6 months of reambulation in six normal male volunteers. Bone regions measured were the lumbar spine, hip, tibia, forearm, calcaneus, total body, and segmental regions from the total-body scan. The total body, lumbar spine, femoral neck, trochanter, tibia, and calcaneus demonstrated significant loss, p less than 0.05. Expressed as the percentage change from baseline, these were 1.4, 3.9, 3.6, 4.6, 2.2, and 10.4, respectively. Although several areas showed positive slopes during reambulation, only the calcaneus was significant (p less than 0.05), with nearly 100% recovery. Segmental analysis of the total-body scans showed significant loss (p less than 0.05) in the lumbar spine, total spine, pelvis, trunk, and legs. During reambulation, the majority of the regions demonstrated positive slopes, although only the pelvis and trunk were significant (p less than 0.05). Potential redistribution of bone mineral was observed: during bed rest the bone mineral increased in the skull of all subjects. The change in total BMD and calcium from calcium balance were significantly (p less than 0.05) correlated, R = 0.88.
Article
To assess the effect of weight-bearing exercise training and subsequent detraining on lumbar bone mineral content in postmenopausal women. Non-randomized, controlled, short-term (9 months) trial and long-term (22 months) exercise training and detraining (13 months). Section of applied physiology at a university school of medicine. Thirty-five healthy, sedentary postmenopausal women, 55 to 70 years old. All women completed the study. There was 90% compliance with exercise training. All women were given calcium, 1500 mg daily. The exercise group did weight-bearing exercise (walking, jogging, stair climbing) at 70% to 90% of maximal oxygen uptake capacity for 50 to 60 min, 3 times weekly. Bone mineral content increased 5.2% (95% confidence interval [CI], 2.0% to 8.4%; P = 0.0037) above baseline after short-term training whereas there was no change (-1.4%) in the control group. After 22 months of exercise, bone mineral content was 6.1% (95% CI, 3.9% to 8.3% above baseline; P = 0.0001) in the long-term training group. After 13 months of decreased activity, bone mass was 1.1% above baseline in the detraining group. Weight-bearing exercise led to significant increases above baseline in bone mineral content which were maintained with continued training in older, postmenopausal women. With reduced weight-bearing exercise, bone mass reverted to baseline levels. Further studies are needed to determine the threshold exercise prescription that will produce significant increases in bone mass.
Article
The aim of the present research was to determine the association between historical physical activity and baseline bone measurements in a group of 223 postmenopausal women participating in a clinical trial in Pittsburgh, Pennsylvania, from 1981 to 1986 by evaluating the effect of moderate physical activity on bone loss. Historical physical activity was assessed by a survey which divided the life span into four time periods (14-21, 22-34, 35-50, and 50+ years) and inquired about participation in leisure time physical activities for each period. From the responses, kilocalories of energy expenditure were calculated. Cortical bone density and area were measured in the radius with a computerized tomography scanner. The historical physical activity survey was administered a second time two to three months after the initial test to a 10% random sample of the women in order to determine the test-retest reliability of the instrument. Since the measurements of historical physical activity proved to be reliable, estimates of kilocalories determined for the entire population of women were correlated with bone area and density. A significant relation was found to exist between historical physical activity and dimensions of adult bone, particularly bone area. This association remained significant after adjustment for potential confounding variables and seemed to be strongest in the earlier age periods. To the authors' knowledge, this is the first report of a significant association between historical physical activity and bone.
Article
The effects of jump training on bone hypertrophy were investigated in 3, 6, 12, 20 and 27 month-old female Fischer 344 rats. The rats of all age groups were divided into jump training (height: 40 cm, 100 times/day, 5 days/wk for 8 wk), run training (speed: 30 ml/min, 1 h/day, 5 days/wk for 8 wk) or sedentary group. Fat-free dry weights (FFW) of the femur and the tibia were significantly greater in the jump-trained rats than in the run-trained rats, and were significantly greater in the run-trained rats than in the sedentary rats. Jump training significantly increased FFW of the femur and the tibia not only in young rats but also in old rats, while run training did not increase FFW significantly in old rats. In young rats, both jump training and run training significantly increased the length of the femur and the tibia and the diameter of the femur. The diameter of the tibia was greater in the jump-trained rats than in the sedentary and the run-trained rats in all age groups. The results of the present study indicate that jump training was a more effective training mode than run training for bone hypertrophy and that the effects were not limited by age.
Article
To examine the role of skeletal loading patterns on bone mineral density (BMD), we compared eumenorrheic athletes who chronically trained by opposite forms of skeletal loading, intensive weight-bearing activity (gymnastics, n = 13), and nonweightbearing activity (swimming, n = 26) and 19 nonathletic controls. BMD (g/cm2) of the lumbar spine, femoral neck, trochanter, and whole body was assessed by dual energy X-ray absorptiometry (DXA). Subregion analysis of the whole body scan permitted BMD evaluation of diverse regions. Swimmers were taller (p = 0.0001), heavier (p < 0.005), and had a greater bone-free lean mass (p < 0.001) than gymnasts and nonathletic controls. When adjusted for body surface area, there was no difference in lean mass between swimmers and gymnasts, and both were higher than controls (p < 0.01). Gymnasts had a lower (p < 0.005) fat mass than swimmers and controls. There were no group differences for spine or whole body BMD, but gymnasts had higher spine BMD corrected for body mass than either swimmers or controls. Gymnasts (1.117 +/- 0.110) had higher femoral neck BMD than controls (0.974 +/- 0.105), who were higher than swimmers (0.875 +/- 0.105) (p = 0.0001). This result still applied when BMD was normalized for body weight and bone size. Trochanter BMD of gymnasts (0.898 +/- 0.130) was also higher than controls (0.784 +/- 0.097) and swimmers (0.748 +/- 0.085) (p = 0.0002), and remained higher when corrected for body mass.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
In a 15 year longitudinal study (Amsterdam Growth and Health Study) is evaluated the effect of daily calcium intake (CAI) during adolescence and young adulthood on the development of peak bone mass at age 27 when the influence of weight-bearing activity (WBA) and body weight was accounted for. A group of 84 males and 98 females were measured longitudinally from age 13 until age 28. Measurements were taken six times of anthropometric characteristics. Lifestyle was also evaluated six times by cross-check interviews of CAI and WBA. Bone mineral density (BMD) of the lumbar spine was determined at age 27 by dual x-ray absorption. Three periods were considered, that is, the adolescent period, the period 13-21 years, and the total period (13-27 years). In multiple linear regression analyses, only WBA and body weight were significant positive contributors to the final model of lumbar BMD at age 27. In all three periods WBA was the best predictor in males and body weight in females. ANOVA was performed on BMD and the highest and lowest quartiles of calcium intake with the significant predictor variables of the linear regression model as covariates. Again calcium intake appeared not a significant predictor of BMD in the three periods in both sexes. Regular weight-bearing exercise and at least a normal age-related body weight in adolescence and young adulthood are of key importance in reaching the highest lumbar peak bone mass at the age of 27 years.
Article
To determine the effects of strength training (ST) on bone mineral density (BMD) and bone remodeling, 18 previously inactive untrained males [mean age 59 +/- 2 (SE) yr] were studied before and after 16 wk of either ST (n = 11) or no exercise (inactive controls; n = 7). Total, spinal (L2-L4), and femoral neck BMD were measured in nine training and seven control subjects before and after the experimental period. Serum concentrations of osteocalcin, skeletal alkaline phosphatase isoenzyme, and tartrate-resistant acid phosphatase were measured before, during, and after the experimental program in all subjects. Training increased muscular strength by an average of 45 +/- 3% (P < 0.001) on a three-repetition maximum test and by 32 +/- 4% (P < 0.001) on an isokinetic test of the knee extensors performed at 60 degrees/s. BMD increased in the femoral neck by 3.8 +/- 1.0% (0.900 +/- 0.05 vs. 0.933 +/- 0.05 g/cm2, P < 0.05) and in the lumbar spine by 2.0 +/- 0.9% (1.180 +/- 0.06 vs. 1.203 +/- 0.06 g/cm2, P < 0.05). However, changes in lumbar spine BMD were not significantly different from those in the control group. There was no significant change in total body BMD. Osteocalcin increased by 19 +/- 6% after 12 wk of training (P < 0.05) and remained significantly elevated after 16 wk of training (P < 0.05). There was a 26 +/- 11% increase in skeletal alkaline phosphatase isoenzyme levels (P < 0.05) after 16 wk of training.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
To address the hypothesis that osteogenic effect of physical loading increases with increasing strain rates and peak forces, we examined 59 competitive Finnish female athletes (representing three sports with different skeletal loading characteristics), physically active referents (they reported an average of five various types of exercise sessions per week), and sedentary referents (two sessions per week) using dual energy X-ray absorptiometry. The measured anatomic sites were at the lumbar spine, femoral neck, distal femur, patella, proximal tibia, calcaneus, and distal radius. The athlete group consisted of aerobic dancers (N = 27), squash players (N = 18), and speed skaters (N = 14). The squash players had the highest values for weight-adjusted bone mineral density (BMD) at the lumbar spine (13.8% p < 0.001 as compared with the sedentary reference group), femoral neck (16.8%, p < 0.001), proximal tibia (12.6%, p < 0.001) and calcaneus (18.5%, p < 0.001). Aerobic dancers and speed skaters also had significantly higher BMD values at the loaded sites than the sedentary reference group, the difference ranging from 5.3% to 13.5%. The physically active referents' BMD values did not differ from those of the sedentary referents at any site. The results support the concept that training, including high strain rates in versatile movements and high peak forces, is more effective in bone formation than training with a large number of low-force repetitions.