Bone health in professional cycling

Bone health is a critical factor for athletes as bones provide the levers for
muscles to move the joints, and strong bones decrease the risk of fractures
during falling. Weight-bearing physical activity substantially impacts bone
mineral density (BMD), while non-weight-bearing activities, such as cycling, do
not contribute to bone health. Indeed, earlier research has shown that cyclist
have lower BMD than their active counterparts. However, limited data in
professional cycling is available. Furthermore, there is no data available on
the progression of low BMD during the active career of professional cyclists.
In line, it is unknown whether the low BMD recovers after the active career of
professional cyclists. Such data is warranted to assess potential health risks
in this population, and to determine the necessity for interventions to prevent
and counteract the loss of bone mass. In addition, high-resolution peripheral
quantitative computed tomography (HR-pQCT), a relatively new imaging modality
that allows detailed in vivo assessment of the cortical and trabecular
compartments of peripheral bone, can be used to further the understanding of
the bone mechanical properties (bone micro-architecture and bone strength) of
elite cyclists.

To examine the time course of changes BMD, bone strength and bone
micro-architecture in professional cycling.

Observational study design.

Bone health will be assessed once by DXA for the present and retired cyclists
and twice yearly for 4 years for the talented cyclists. The measurement is
painless, non-invasive and involves only low radiation exposure. The DXA
scanning includes imaging of the whole body for the determination of fat mass
and fat free mass (radiation dose ~0.003 - 0.008 mSv). In addition, images of
the lumbar spine (radiation dose ~0.005 - 0.014 mSv) and hip (radiation dose
~0.002 - 0.004 mSv) will be made for the assessment of bone density. The
cumulative effective radiation dose will be ~0.010 - 0.026 mSv. In comparison,
the daily radiation dose from natural sources in the Netherlands (cosmos, food,
soil) is ~0.003, and the radiation dose from a one-way intercontinental flight
is ~0.050 mSv. Thus, the radiation involved in this study is marginally higher
than the daily radiation dose from natural sources, but substantially lower
than an intercontinental flight.
The risks of participation in the HR-pQCT is limited to a relatively low
exposure of radiation. Each HR-pQCT scan has an effective radiation dose of
~0.005 mSv, which brings the total radiation dose of study participation (i.e.
HR-pQCT) to ~0.02 mSv (i.e. two radius and two tibia scans). In case motion
artefacts necessitate a repeated HR-pQCT scan, a participant is exposed to a
maximum radiation dose of ~0.04 mSv when all four scans have to be repeated.
The cumulative effective radiation dose for a participant that undergoes both
DXA and HR-pQCT will be minimal 0.03 and maximal 0.066 mSv per year.

Venous blood will be collected. For this procedure, a small needle will be
inserted into the antecubital vein and blood (35 mL) will be collected through
a closed system attached to the needle. The discomfort of this procedure is
transient and is comparable to having an injection by a needle, or donating
blood.

The time invested by participants is approximately 60-90 minutes per visit, and
30 minutes per visit for the HR-pQCT, excluding traveling time.

Taken together, the total burden en health risk by participating in this study
are considered low.