Adaptation of the lumbar spine to different positions in bicycle racing.
METHODS
A radiologic and electromyographic study was done of the adaptation of the lumbar spine to high-performance cycling.


OBJECTIVE
To evaluate changes in the lumbar spine produced by different cycling positions on different types of bicycles used during competition.


METHODS
Three professional cyclists were observed to evaluate changes in the lumbar spine. Radiographs were obtained of the different positions adopted by the cyclists during competition, and changes in the angles of the lumbar spine were measured. An electromyographic study was done of the abdominal, lumbar, and thoracic paravertebral muscles.


RESULTS
The cyclists' positions involved a change from discal lordosis to kyphosis. To obtain a more aerodynamic position, the cyclists flexed the hip and made the pelvis horizontal without changing disc angles. The contraction of paravertebral lumbar muscles was proportional to pedalling intensity and decreased in more aerodynamic positions. The tone of the paravertebral thoracic muscles depended on the extent of cervical hyperextension. Abdominal muscles remained relaxed in all bicycle positions and with all pedalling intensities.


CONCLUSIONS
The changes observed could modify the normal biomechanics of the lumbar spine, but the overall mechanical load on the spine is reduced by shifting weight onto the upper limbs. The imbalance that occurs between the activity of flexor and extensor muscles could cause lumbar pain in persons without proper physical preparation.
Usabiaga
J
J
Traumatology Department, Nuestra Señora de Aránzazu Hospital, San Sebastián, Spain.
Crespo
R
R
Iza
I
I
Aramendi
J
J
Terrados
N
N
Poza
J J
JJ
D000222:Adaptation, Physiological / Q000502:physiology; D001642:Bicycling / Q000502:physiology*; D004576:Electromyography; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D011187:Posture / Q000502:physiology*; D011859:Radiography; D016474:Weight-Bearing / Q000502:physiology