Olmedillas et al. BMC Medicine 2012, 10:168
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RESEARCH ARTICLE

Open Access

Cycling and bone health: a systematic review
Hugo Olmedillas1,2†, Alejandro González-Agüero1,2*†, Luis A Moreno1,3, José A Casajus1,2 andGermán Vicente-Rodríguez1,2
See related commentary http://www.biomedcentral.com/1741-7015/10/169.

Abstract
Background: Cycling is considered to be a highly beneficial sport for significantly enhancing cardiovascular fitness
in individuals, yet studies show little or no corresponding improvements in bone mass.
Methods: A scientific literature search on studies discussing bone mass and bone metabolism in cyclists was
performed to collect all relevant published material up to April 2012. Descriptive, cross-sectional, longitudinal andinterventional studies were all reviewed. Inclusion criteria were met by 31 studies.
Results: Heterogeneous studies in terms of gender, age, data source, group of comparison, cycling level ormodality practiced among others factors showed minor but important differences in results. Despite some
controversial results, it has been observed that adult road cyclists participating in regular training have low bonemineral density in key regions (for example, lumbar spine). Conversely, other types of cycling (such as mountainbiking), or combination with other sports could reduce this unsafe effect. These results cannot yet be explained bydifferences in dietary patterns or endocrine factors.
Conclusions: From our comprehensive survey of the current available literature it can be concluded that roadcycling does not appear to confer any significant osteogenic benefit. The cause of this may be related to spending
long hours in a weight-supported position on the bike in combination with the necessary enforced recovery timethat involves a large amount of time sitting or lying supine, especially at the competitive level.
Keywords: cyclists, osteopenia, osteoporosis, sport, training

Background
Participation in cycling has been shown to confer several
health benefits in terms of improvements in cardiovascular
fitness, reductions in mortality, and reduced cardiovascularrisk factors as well as a reduced risk of cancer [1]. From apublic health point of view, cycling is a widely practiced
non-weight-bearing sport around the world, especially inEurope [2] and the bicycle is also used as a vehicle by millions of people in many different countries, accounting for
an important part of their daily physical activity. However,as a non-weight-bearing activity, cycling practice is frequently associated with lower levels of bone mass [3]; in
fact, two-thirds of the professional and master adult roadcyclists could be classified as osteopenic [4].
* Correspondence: alexgonz@unizar.es† Contributed equally
1
GENUD ‘Growth, Exercise, NUtrition and Development’ Research Group,
Universidad de Zaragoza, Zaragoza, Spain
Full list of author information is available at the end of the article

Osteoporosis generally affects older populations and ischaracterized by ‘low bone density and microarchitectural
deterioration of bone tissue with a consequent increase inbone fragility and susceptibility to fracture’ [5]. Low levelsof bone mineral density (BMD) during earlier stages of life
may contribute to the development of osteoporosis lateron in life [6].
Many aspects of bones account for bone strength andresistance against fracture: bone mineral content (BMC),
BMD, bone size, structure and microarchitecture, among
others [7]. Genetic predisposition, dietary patterns, endocrine and environmental factors also play determiningroles in bone health and maintenance throughout life[8,9]. Among the many environmental factors, physicalactivity and participation in sport promote health benefits
in bone mass across all ages among different populations[10-14].
With regard to endocrine factors, the net product of boneformation and bone resorption, namely bone turnover, may© 2012 Olmedillas et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, andreproduction in any medium, provided the original work is properly cited.

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be estimated by biomarkers involved with bone metabolism
such as bone alkaline phosphatase (BAP), osteocalcin (OC)or C-terminal collagen crosslinks (CTX), which are among
the most commonly studied in sport sciences [15].
This review aims to summarize the current available
literature concerning bone mass and bone metabolism
in cyclists, to observe whether the findings of the collective research are commensurate with the general ideathat cycling has a deleterious effect on bone mass.

Table 1 summarizes all the studies concerning bonemass and cycling participation included in this review.
Different age stages (adolescents, adults, older adults), genders, competitive levels, years of practice and groups ofcomparison (that is, sedentary controls, runners, and soon) were included in this review, making the comparison
between studies rather difficult; however, efforts have been
made to summarize and clarify the current knowledge on
this topic despite discrepancies in these variables.

Methods

Strength of evidence

Search strategy

The guidelines of Hadorn et al. [18] were used to rate thequality of evidence of every study and the qualifications
were also stated in Table 1. This method includes threelevels of quality, as outlined below.
Level A: well conducted randomized control trials (RCT)with 100 participants or more (including multicenter andmeta-analyses); well conducted RCT with fewer than 100
participants (one or more institutions and meta-analysis;
well conducted study).
Level B: well conducted case-control study, poorly controlled or uncontrolled (including RCT with one or more
major or three or more minor methodological flaws),
observations studies with high potential for bias (case series with comparison to historical controls), case series orcase reports, conflicting evidence with more support.

Journal articles were identified from MedLine (1965 toApril 2012), EMBASE, Web of Science and SportDiscus.
The search strategy used to identify the articles was:‘((bone) or (bmc) or (bmd) or (osteoporosis)) AND((cyclist) or (cyclists) or (cycling sport) or (triathlon) or(triathletes))’ to identify the articles on the topic of thisreview. Additional articles were added after reviewing thereferences of the previous researches. This produced atotal of 214 citations. MOOSE [16] and PRISMA [17]guidelines for the reporting of systematic reviews were
followed for observational and interventional studies
respectively.
Inclusion criteria

The inclusion criteria for this review were: (a) bone massor bone metabolism markers, and not fractures or any
other topic, had to be the main subject of each study; (b)the studies had to include cyclists or triathletes and not
only athletes or sportspeople; (c) the type of studies to be
included had to be original research manuscripts (crosssectional, interventional, follow-up or retrospective studies); reviews or published abstracts were not included; (d)only papers written entirely in English were included inthis review.
Exclusion criteria

The inclusion criteria were applied to the 215 citations by
2 authors independently; if disagreement occurred, allauthors reviewed the data until consensus was achieved.
Of the total of 215 citations, 31 references fulfilled theinclusion criteria (Figure 1). A total of 184 citations were
excluded for the following reasons: 145 did not include
bone mass or bone metabolism markers as their main
topic, 17 were not original articles and 22 were not written
in English.
Data extraction

Each study was independently evaluated. General information about the article title and type of the study,
author(s), characteristics of the participants (age, sex, andexercise), comparison group(s) (if available), data source
and results were also extracted.

Level C: expert opinion

Additional file 1 evaluates the quality and strength ofevidence of each study, providing a final score based on
several objective questions.

Results and discussion
Cycling and bone mass
BMC and BMD

The vast majority of the reviewed studies used dual energy
X-ray absorptiometry (DXA) devices for their investigations; in fact only 2 out of 31 studies did not include any
DXA measurement in their results.
Heinonen et al., in 1993, first described and comparedbone mass of young adult female cyclists with other different sportswomen and controls. They found that cyclists
had lower BMD at all body sites than weightlifters, but nodifferences were observed with other sports or with controls [19]. Subsequent studies reinforced the finding thatno differences in BMC or BMD were observed between
cyclists and controls, in both males and females, either inadolescents [20,21] or adults [22-26], or compared withother competitive sportspeople [27]. Furthermore, Warner
et al. found that adult cross-country cyclists had higher
BMD than road cyclists and controls [28].
Despite the above-mentioned studies, the available literature largely describes lower levels of BMD and BMC
for different bodily regions in cyclist participants almost
at all ages and in both genders. The lumbar spine hasOlmedillas et al. BMC Medicine 2012, 10:168
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Figure 1 Flow chart diagram of the study selection process.

probably been the most studied region in this regard,with fairly conclusive results that lower BMD can beobserved in cyclists compared with controls [29-35],
practitioners of other sports [19,35-37] or reference
values [4,38,39]. Moreover, the pelvic and hip regions,as key areas for osteoporotic fractures, and the wholebody have been studied with concerning results. Lower
values of pelvis, hip and femoral neck BMD in male
cyclists were found compared with controls at all ages
[29,32,34,40], with higher differences in the older cyclists.
Longitudinal studies may help to understand whether
the observed low bone mass is acquired during a period oftime and then maintained, or whether in fact, cycling
training has a harmful effect on this tissue. In this regard,
Beshgetoor et al. showed that 18 months of training incompetitive female cyclist resulted in maintenance of thefemur BMD, but a declination in lumbar spine BMD [41].
More recently, Nichols et al. showed that not only weremore master cyclists classified as osteoporotic comparedto age-matched and weight-matched non-athletes, but also
the percentage of osteoporotic cyclists increased significantly over a 7-year period [42]. Also, Barry et al. studied
two groups of adult cyclists supplementing them with highand low calcium intakes; they observed that the declination in hip BMD was the same in both groups [43].
Most of the studies reviewed showed that cycling does
not appear to have a beneficial effect on BMD, especiallyat the lumbar spine, with some cases showing detrimental
effects compared to other osteogenic sports. Very few studies have been conducted on child or adolescent cyclists,
but the available manuscripts allow us to hypothesize thatthe differences in BMD become greater with age. Also,

longitudinal studies point to this by showing declinations
even with calcium supplementation.
Bone geometry and structure

The DXA device creates a two-dimensional image of thebone that does not provide information about volumetric
BMD (vBMD) and does not differentiate cortical andtrabecular bone. Osteoporosis is highly related to BMD;
however, strength indexes and, therefore, the risk of fracture have a close relationship with structural aspects ofbones such as cortical thickness and bone cross-sectionalarea, among others [44]. Peripheral quantitative computed
tomography (pQCT) and magnetic resonance imaging(MRI) are alternative bone densitometry techniques thatallow separate evaluation of those bone regions. These
techniques are also able to assess actual vBMD at peripheral sites as well as estimating geometric properties ofbone that are related to bone strength, going beyond thescope of current DXA determinations.
Two studies of this nature performed on cyclists wereidentified. Using MRI, Duncan et al. found that female
adolescent cyclists had lower bone cross-sectional area,
moment of inertia and mid-femur vBMD than their runner counterparts, while no differences were observed with
controls [45]. Wilks et al. compared pQCT values of maledistance-trained and sprint-trained master cyclists (aged
30 to 82 years) with age-matched sedentary controls, finding that distance-trained athletes presented higher values
at the tibial sites, and sprinters at both tibial and radialsites, than controls [46].
Due to the abundance of factors contributing to bonestrength, it seems that, regardless of the lower values of
BMD observed in studies with DXA, cycling does notStudyParticipants

ExerciseStudy design

Data source Resultsa

Strength ofevidence

2-h exercise bout at 60% to
75% VT

Hormones,
calcium

Parathyroid was increased after 2 h of cycling.

B:observational

4.9 ± 2.4

Two groups: HIGH and LOW
calcium supplementation
over 1-year season

DXA

Both groups decreased BMD over 1 year in total hip andsubregions, without differences for HIGH or LOW calcium.

A: RCT

Years ofcyclingtraining

NumberSex Age

Barry et al.
(2007) [47]CYC (20)

M

22
to
45

Competitive
level

Barry et al.
(2008) [43]CYC (14)

M

27
to
44

>450 h/year

Barry et al.
(2011) [39]CYC and TRI (20)M

37 ± 7.6

6.0 ± 6.5

Different calcium
DXA,
supplementation groups over hormones
three 35-km trials

Beshgetoor CYC (12); RUN (9);et al. (2000) CON (9)
[41]

F

49.6
±
7.9

-

-

18 months follow-up

DXA, calcium Femur BMD maintained in CYC and RUN, decline CON. LS
intakeBMD maintained RUN, decline CYC and CON. No
relationship between BMD and calcium intake.

B: casecontrol

Brown et al. CYC (32)(2000) [49]

M/
F

16
to
62

Competitive
cycling>2

Two groups: HIGH FAT and
HIGH CARBOHYDRATE intake;12-week intervention

DXA

No differences in fat or lean accumulation between
groups. BMD increased in HIGH FAT group.

A: RCT

Campion et CYC (30)
CON (30)al. (2010)
[34]

M

29 ±
3.4
28 ±
4.5
16
to
17

22 to 25 h/
week<1 h/week-

Cross-sectional

DXA

CYC lower WB, LS, pelvis, femoral neck, upper and lower
limbs than CON

B: casecontrol≥8 h/week≥8 h/week≥8 h/week≥8 h/week<2 h/week

3.1 ± 1.8

Cross-sectional

DXA

CYC lower legs BMD than RUN. No differences with CON.

B: casecontrol

3.1 ± 1.8

Cross-sectional

MRI, DXACYC lower cortical CSA, moment of inertia and mid-femur
BMD than RUN. No differences with CON.

B: casecontrol-

Cross-sectional

DXA

CYC lower WB, LS and pelvic BMD than CAN. No
differences with CON.
CYC lower LS BMD Z-scores. Bone turnover markers werein a normal range.

B: casecontrol
B: case series

CYC (15)
RUN (15)
SWI (15)
TRI (15)
CON (15)CYC (10)
RUN (10)
SWI (10)
TRI (10)
CON (10)CYC (14); CAN (18);
CON (28)
CYC (29)

F

Heinonen
CYC (22); ORI (30);
et al. (1993) SKI (28); CYC (29);
WL (18); CON (25)[19]

Duncan etal. (2002)[21]

Duncan etal. (2002)[45]

Fiore et al.
(1996) [36]Guillaume
et al. (2012)[38]

CYC (16)
RUN (37)
TRI (22)TEAM (62)
POW (45)
BAL (13)
STU (126)
CON (61)

F

16
to
17

M

-

≥8 h/week≥8 h/week≥8 h/week≥8 h/week<2 h/week
-

M

26.5
±
5.3

25,000 to
30,000 km/
year

4.5 ± 4

Descriptive

DXA, bonemarkers

F

18
to
32

-

-

Cross-sectional

DXA, calcium CYC lower BMD at all sites than WL. No differences withintakeCON. No relationship between BMD and calcium intake.

B: casecontrol

M/
F

17
to
30

15 h/week
12.5 h/week
15 h/week
10 h/week
10 h/week
27 h/week
7.5 h/week->4

Cross-sectional

DXA

B: casecontrol

CYC low values of LS and femur BMD than the othergroupsPage 4 of 10

Hinrichs etal. (2010)[35]

30% of participants had LS BMD T-score over -1.0. Calcium A: RCT
supplementation attenuates disruption of parathyroid
hormone.

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Table 1 Studies concerning bone mass, bone metabolism and cycling participationMaïmoun et CYC (11)SWI (13)al. (2003)[25]
TRI (14)
CON (10)

M

18
to
39

10.6 h/week
10.7 h/week
15.2 h/week<2 h/week-

Cross-sectional

DXA,
hormones

CYC and TRI induce androgen deficiency compared toCON, without alteration in BMDMaïmoun et CYC (11)al. (2004)
SWI (13)[24]
TRI (14)
CON (10)

M

18
to
39

10.6 h/week
10.7 h/week
15.2 h/week<2 h/week

9.3 ± 6.8

Cross-sectional

DXA, bonemarkers,
calcium
intakeCYC lower BAP than all groups. No differences in BMD. No B: caserelationship between BMD and calcium intake.
control

Medelli etal. (2009)[29]

CYC (73)
CON (30)

M

25.8
±
4.3
28.3
±
4.5

≥3 to 6 h/day<1 h/week-

Cross-sectional

DXA, calcium CYC had higher calcium intake and lower LS and femoral
intakeneck BMD than CON.

B: casecontrol

Medelli etal. (2009)[4]

CYC (23)

M

28.5
±
3.9

≥3 to 6 h/day-

Descriptive

DXA

Two-thirds of participants had lower values of LS BMD

B: case series

Morel et al.
(2001) [27]CYC (47); othersports (657)M

30

7 h/week-

Cross-sectional. Sportsmen
classed as amateur when 11
to 18 years old.

DXA

No differences between different sports

B: casecontrol,
retrospective

Nevill et al.
(2004) [23]CYC (16)
CON (15)
Others (90)

M

28.6
±6
24.9
±
5.4
-

>4 h/week->3

Cross-sectional

DXA

CYC had no differences in BMD compared to CON, as
other sports do

B: casecontrol

Nichols etal. (2003)[32]

Young CYC (16)Master CYC (27)
CON (24)M≥10 h/week≥10 h/week<2 days/week

10.9 ± 3.2 Cross-sectional
20.2 ± 8.4-

DXA

Master CYC lower WB BMD than young CYC. Master CYC
lower LS and hip BMD than young CYC and CON.

B: casecontrol

Nichols etal. (2010)[42]

CYC (19)
CON (18)

M

31.7
±
3.5
51.2
±
5.3
51.2
±2
50.7
±4
50.7
±
4.1

11.1 h/week
4.5 h/week

27.5 ± 6.8 Longitudinal, 7-year follow-up DXA

Higher percentage of CYC osteopenic/osteoporotic thanCON. Greater increment in this percentage in CYC.

B: casecontrol

Nikander etal. (2005)[26]

CYC (29)
SWI (27)
VOL (21)
HUR (24)
SQU (20)
SOC (19)
SKA (15)
AER (27)
WL (19)
ORI (29)
CRO (25)
CON (30)F

10.2 ± 6.8
13.5 ± 4.5
9.9 ± 2.5
9.1 ± 2.4
6.0 ± 3.1
8.6 ± 5.5
6.4 ± 3.6
6.6 ± 3.7
8.3 ± 2.6
8.6 ± 1.4
10.9 ± 1.2
2.9 ± 2.0

5.9 ± 3.1 Cross-sectional
10.6 ± 4.3
8.6 ± 3.3
10.4 ± 3.0
6.4 ± 4.7
10.7 ± 3.8
9.4 ± 7.2
8.3 ± 2.7
3.3 ± 1.3
13.0 ± 3.1
10.7 ± 3.5
-

20
to
30

B: casecontrol

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Table 1 Studies concerning bone mass, bone metabolism and cycling participation (Continued)

DXA, calcium CYC and SWI no differences with CON in BMD and CSA, as B: caseintake
the rest of the sports. No differences in calcium intake.
control

Page 5 of 10

Olmedillas CYC (21)et al. (2011) CON (23)
[40]

M

15
to
21

10 h/week
4 h/week

2 to 7

Cross-sectional

DXA

CYC lower BMC at WB, pelvis, FN and legs, and lower BMD B: caseat pelvis, hip and legs. Greater differences in CYC over 17 control
years compared to CON.

Penteado et CYC (31)
CON (28)al. (2001)
[22]

M

24
26

21 h/week0

5.2 ± 3.3

Cross-sectional

DXA

No differences with CON.

B: casecontrol

Rector et al. CYC (27)(2008) [37] RUN (16)

M

20
to
39

≥6 h/week≥6 h/week>2

Cross-sectional

DXA, bonemarkers

CYC lower WB and LS BMD, and 7 times more likely tohave osteopenia than RUN. No differences in boneturnover markers.

B: casecontrol

Rico et al.
(1993) [20]CYC (22)
CON (27)M

16≥10 h/week->2

Cross-sectional

DXA, calcium CYC lower legs BMC than CON, without adjustment. No
intakedifferences when adjusting by weight. No relationshipbetween BMD and calcium intake.

B: casecontrol

Rico et al.
(1993) [50]CYC (22)
CON (27)M

16≥10 h/week->2

Cross-sectional

DXA

CYC lower WB BMC and BMD than CON

B: casecontrol

Sabo et al.
(1996) [30]CYC (6)
WL (28)BOX (6)
CON (21)

M

21
to
24

3,000 to10,000 km inprecompetition-

Cross-sectional

DXA

CYC lower LS BMD than CON

B: casecontrol

CYC (14)
RUN (12)RUN+CYC (13)CON (23)
Smathers et CYC (32)al. (2009)
CON (30)
[33]

M

18
to
43

>2

Cross-sectional

DXA

CYC lower LS BMD than CON. RUN higher WB BMD thanCON. RUN+CYC higher WB BMD than CON.

B: casecontrol

M

20
to
45

8.7 h/week
10.7 h/week
9.4 h/week
0 h/week≥1 year3 days/week

9.4 ± 1.1

Cross-sectional

DXA, calcium CYC higher calcium intake. No differences for testosterone. B: caseintake,
CYC lower LS BMD than CON.
control
hormones

Warner etal. (2002)
[28]

M

20
to
40

≥10 h/week≥10 h/week<2 h/week

5.9 ± 2.8
9.9 ± 4.4-

Cross-sectional

DXA,
hormones

Cross-country CYC higher BMD at all sites that road CYC
and CON. No differences in testosterone levels.

B: casecontrol

M/
F

30
<2 h/week
to
82
50 ±
13

26 ± 1529 ± 16
Start age

Cross-sectional

pQCT

Sprint CYC higher index of strength in tibia and radiusthan CON. Distance CYC higher tibial BMC than CON.

B: casecontrol

Stewart etal. (2000)[31]

Wilks et al.
(2009) [46]

Cross-country CYC(16)Road CYC (14)CON (15)
Sprint CYC (52)Distance CYC (19)
CON (32)

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Table 1 Studies concerning bone mass, bone metabolism and cycling participation (Continued)aUnless stated, the results indicate significant differences between two or more groups.
AER = step aerobicists; BAP = bone alkaline phosphatase; BMC = bone mineral content; BMD = bone mineral density; BOX = boxers; CAN = canoeists; CIC = cyclists; CON = controls; CRO = cross-country skiers; CTX =C-terminal collagen crosslinks; DXA = dual energy X-ray absorptiometry; HUR = hurdlers; LS = lumbar spine; MRI = magnetic resonance imaging; OC = osteocalcin; ORI = orienteers; pQCT = peripheral quantitative
computed tomography; RCT = randomized control trial; RUN = runners; SKA = speed skaters; SKI = skiers; SQU = squash players; SWI = swimmers; TRI = triathletes; VOL = volleyball players; WB = whole body; WL =weightlifters.

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negatively affect the geometry and/or structure of thebones measured with pQCT. What appears to be clear isthat more in-depth studies are required in order to corroborate these findings, and to evaluate possible changes
over different periods of time and life stages in thesevariables.
Endocrine factors related with bone mass
Bone turnover markers

Bone turnover markers related to bone formation, suchas BAP or OC and also CTX related to bone resorption,
have been barely investigated in cyclist populations.
Rector et al. showed no differences between adultcyclists and runners in bone metabolism markers [37], andGuillaume et al. reinforced that by showing these markers
in normal ranges in a group of young cyclists [38]. However, Maïmoun et al. [24] studied three groups of adultathletes (cyclists, triathletes and swimmers), compared tocontrols, and showed lower BAP in cyclists compared toany other group. No differences were found for OC or
CTX among the three groups of athletes.
Hormonal profile

Smathers et al. and Warner et al. showed no differencesin testosterone levels between adult male cyclists andcontrols [28,33]; however, Maïmoun et al. showed lower
testosterone levels in adult male cyclists and triathletescompared with controls [25]. Two different interventional studies focused on the effects of cycling on parathyroid hormone concluded that it increased after 2 h ofcycling [47], and that calcium supplementation attenuated its disruption [39].
Inconclusive results can be obtained from the few heterogeneous studies available on neuroendocrine factors
affecting bone mass in cyclists; nevertheless, it may be stated that the hormonal status seems to be within normal
ranges in this specific population and that the formationof bone appears to be somewhat reduced in a group of
adult cyclists with a long history of training (over 9 years
on average). For that reason, as bone metabolism does notseem to be the main factor regarding the general low
mineral accumulation in cyclists’ bones, other mechanicalfactors such as the lack of osteogenic impacts might also
have an influence.

Page 7 of 10

cyclists independently of their high or low calcium intake
over a 1-year season [43], and that acute calcium supplementation decreased the parathyroid hormone disruption
after cycling [39]. Werner et al. did not find differences incalcium or vitamin D intake between road and mountaincyclists and controls [28]. Brown et al. showed that a fatrich diet yielded higher increments in BMD in cyclists
than other carbohydrate-rich diets without variation in fat
or lean masses over a period of 12 weeks [49].
Studies appear to indicate that there are no observableeffects in consuming higher amounts of calcium toreduce the supposed detrimental effect of cycling onbone mass. Furthermore, from these data it is difficult
to define whether or not cyclists do in fact require any
additional calcium supplements. Further studies arenecessary in order to confirm previous results and to
elucidate whether diet may be a more important factor
for cyclists during years of growth in comparison to athletes in other disciplines.
Age

As previously stated, adult cyclists showed lower BMD atseveral sites of the body (mainly then lumbar spine) compared to controls or practitioners of other sports; however, few of the included studies incorporated
adolescents within their samples. These studies showedsimilar results in that, under the age of 18, the differencesin BMD between cyclists and controls were not observable [40,45,50], as observed in adolescent runners [21]. In
addition, Maïmoun et al. [24] stated that age, among
other factors, could influence BMD in people that practice sports including cycling. Though using a different
measurement technique (that is, pQCT) Wilks et al. [46]suggested that cycling activity could prevent bonestrength losses in older people.
The positive effect that general sport practice has onbone is well known [10], and that maximizing bonemineral mass during growth may help to prevent fracturesduring adolescence and at an older age [51]. We haveobserved that cycling during the early years of life does
not negatively affect the bones, yet it does not exert asmuch of a positive influence as other sports clearly do.
Consequently, the age factor for cycling must be taken
into account.
Gender

Factors affecting bone mass
Diet and calcium intake

Some authors found that cyclists take in a higher amountof calcium than controls [29,33], but as it is believed thatcyclists have a higher energy intake than controls due tohigher energy expenditure [48], total energy intake is a factor that must be taken into account. However, no associations were found between calcium intake and BMD for
adults and young adult cyclists [19,20,24,41]. In addition,
Barry et al. found that BMD was decreased in a group of

It is widely known that women have lower bone mass
than men throughout life and that are at higher risk of
suffering from osteoporosis; therefore it is important toascertain whether gender has any influential effect on
the accumulation of bone mass in cyclists.
The studies included in this review incorporating only
women within their samples showed similar results inbone mass to studies on men or both genders when
they are compared with other sportswomen or controls[19,21,41,45].

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Therefore, because females are more likely to become
osteoporotic, pre-participation examinations (that is,
DXA scans) should be conducted in adult female cyclists
training at a high level.
Training level and type of cycling practice

Few studies have been performed in low-level cyclist
populations; Morel et al. studied amateur sportsmen
without finding differences in bone mass between cycling
and other sports [27]. In general, studies included in thisreview had samples of adult cyclists with a high level oftraining; however, some of them were performed in amateur or adolescent cyclists, showing that in fact the levelof practice and/or the years of training might increase
the risk of low bone mass.
The two studies by Duncan et al. showed no differencesin BMD between cyclists and controls, but it is worth noting
the sample of adolescents that they used [21,45]. The study
by Wilks et al., which is discussed below, showed greaterbone strength surrogates in cyclists compared to controls ina sample of adults and older adults with a high level ofcycling practice during their adolescence and adulthood.
Cycling is a widespread activity that involves different
disciplines (that is, mountain biking, road cyclists, BMX,
and so on) and, in combination with swimming and/or
running, forms part of triathlon or duathlon events.
What has been observed regarding combination of
cycling with running is that this practice counteracts theeffect that cycling has on bone mass by an increased total
body BMD compared with controls not observed in thecycling alone group [31]. In triathletes Maïmoun et al.
demonstrated a similar behavior to cyclists in terms of testosterone deficiency without differences in BMD [25].
Concerning different types of cycling, as expected, Wilkset al. demonstrated that sprint-trained cyclists had stronger bones than those training for longer distances [46],and Warner et al. showed that cross-country cycling practitioners acquire higher BMD than road cyclists [28].
From a review of the current available literaturedescribed herein it can be concluded that road cycling at acompetitive level might be more detrimental for bonehealth than other forms of cycling such as mountain biking in a recreational way. However, it should be mentionedthat an upper threshold of training level may exist which
protects bones from fractures, perhaps by improving theirgeometry and/or structure. Moreover, and especiallywhere elite cyclists are concerned, it is also possible that
resistance training also provides significant positive influences on bone mass. It is noteworthy that duathlon andtriathlon do not have the same harmful effect that cyclingalone seems to have on bone mass.

Limitations
Different sources of bias inherent to systematic
reviews should be addressed. First, we excluded non-Page 8 of 10

English publications; thus a possible language bias isinherent.
Second, the studies included in our systematic review
were too heterogeneous to perform a meta-analysis. The
lack of this type of analysis makes difficult to reachstrong conclusions. However, Table 1 contains quantitative information on each individual study.
Third, we classified articles into categories based on
their assessment method, and afterwards we discussed
some factors affecting bone mass. We believe that theresults are more easily read and understood with thiscategorization. Although we systematically assessed articles before assigning them into categories, categorization
is not a closed issue.

Conclusions
To date, a considerable number of studies have reported
on the possible harmful effect of cycling on bone health;however there are still some pending issues that need tobe addressed. In general, cycling participation seems tohave a neutral effect on bone health in terms of low
BMD at several sites of the body; however, some factors
need to be taken into account regarding this assumption.
Road endurance cycling at a professional level could be
more detrimental to bone mass than performing thisactivity recreationally, or worse than performing otherdisciplines such as cross-country cycling or combinationsof cycling with running [28]. In addition, there is someevidence that the practice of this sport during adolescence and adulthood could help to maintain a betterbone geometry and strength later in life [46]. Few studies
described bone mass in young cyclist populations, however, it can be hypothesized that the differences in BMD
between cyclists and controls or other sport practitioners
become greater from 17 years of age onwards [40]. It is
important to note that, contrary to other sports, there
have been no reports of any positive effects of cycling onbone mass during adolescence.
Factors affecting bone mass such as calcium intake
and hormonal profile were found to be within the regular range in cyclists [28,29,33]; allowing us to believethat the lack of impact might be one of the main reasons for the low bone mass acquisition in this population. It is also thought that professional cyclists spend
several hours daily resting after training time, andsedentary time has been associated with low bone mass[52]; this factor should be taken into account as it may
also partially explain the low BMD observed in theseathletes.
In general it can be concluded that individuals whopractice non-weight-bearing sports such as cycling are
more likely to develop osteopenia or osteoporosis [53];and the high incidence of falls while cycling makes thisfact even more relevant for this population [42,54].

Olmedillas et al. BMC Medicine 2012, 10:168
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In conclusion, road cycling at a competitive level is lesseffective at improving bone mass when compared withweight-bearing sports. Based on the available evidence, in
general, cycling as a sole form of exercise is not recommended for people who are at risk of developing osteoporosis, unless it is complemented with some kind of
osteogenic training.
Practical recommendations and future research

The likelihood of a cyclist to develop osteopenia or osteoporosis at clinical sites due to low levels of BMD must be
taken into account by health organizations, federations,trainers and athletes. In accordance with Maïmoun et al.
there may exist a threshold, since BMD measurements are
inadequate to detect slight and acute changes in bonemetabolism [55], and therefore further research on bonemetabolism, bone strength and structure in cyclists at different ages, based on previous studies [46], could help tobetter understand the actual bone weakness in cyclists.
Also, longitudinal studies aimed at identifying whether the
key periods of bone mass acquisition are affected bycycling are needed.
Secondly, Beatty et al. [56] and Nichols et al. [42] proposed to incorporate impact activities in training programsfor cyclists, as it has been demonstrated that plyometricjumps increase bone mass in different populations [14,57].
Generally, amateur cyclists are unwilling to include resistance and/or plyometric exercise in their routine throughout the season despite there being no scientific evidence ofperformance impairment. Therefore, studies on the effects
of different training implementations will define whether
these interventions are enough to counteract the effect of
cycling.

Additional material
Additional file 1: Quality assessment tool of the included studies.
Additional file 1 provides measurement regarding the quality andstrength of the evidence of each study included in the review.

Acknowledgements
This review was funded by Ministerio de Ciencia e Innovacion, Instituto de
Salud Carlos III (DPS2008-06999) and Presidencia del Gobierno de España,
Consejo Superior de Deportes (21/UPB20/10). Special thanks are given to
Scott G Mitchell from the Institute of Nanoscience of Aragon (INA) for his
work in reviewing the English style and grammar.
Author details
GENUD ‘Growth, Exercise, NUtrition and Development’ Research Group,
Universidad de Zaragoza, Zaragoza, Spain. 2Faculty of Health and Sport
Sciences (FCSD), Department of Physiatry and Nursing, Universidad deZaragoza, Huesca, Spain. 3School of Health Science (EUCS), Universidad deZaragoza, Zaragoza, Spain.
1

Authors’ contributions
All authors made substantive intellectual contributions to the final
manuscript, and read and approved it.

Page 9 of 10

Competing interests
The authors declare that they have no competing interests.
Received: 7 May 2012 Accepted: 20 December 2012
Published: 20 December 2012
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Cite this article as: Olmedillas et al.: Cycling and bone health: asystematic review. BMC Medicine 2012 10:168.

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