Cervical spine positions and load moments during bicycling with different handlebar positions.

The aim of this study was to analyse the influence of handlebar height, during cycling, on the cervical and thoracic spine postures and on the load moment about the bilateral axis of C7-T1 induced by the weight of the head-and-neck. Data were collected from eight male subjects (24-34 years) using those parts of the ENOCH system that consist of a minicomputer and an opto-electronic device (Selspot) for collecting kinematic data. Light-emitting diode markers were attached to a set-square on a helmet, and to the skin. The subject cycled on a bicycle ergometer using three different handlebar positions. A Selspot camera observed all the markers during 50 samples at 315 Hz. The relative angles for the upper -and lower-cervical spine and the vertical inclination of the upper thoracic spine were included in the analysis. The lever arm of the head-and-neck was also calculated. The results show that the forward inclination of the trunk required when lower handlebars were used did not affect lumbar lordosis or thoracic kyphosis, but gave increased extension of the upper-cervical spine. The use of racing handlebars induced a flexing load moment about the bilateral motion axis of the lower-cervical-upper-thoracic motion segment (C7-T1) three times that in a vertical sitting position. Thus, high handlebars are to be recommended, particularly if the cyclist normally experiences discomfort during extension of the cervical spine. High handlebars reduce the load on the lower cervical spine and decrease the risk of maintained cervical spine extended positions.