KINEMATIC ANALYSIS OF CYCLING DURING PREGNANCY

Abstract

How much? What kind? Should I? These are questions often asked by pregnant women concerning their exercise and sport activities during pregnancy, but there is, to date, very little research in the area of biomechanics and pregnant women in sport. According to Dr. Lynne Pyrie (1987), cycling is a sport made for pregnant women. Cycling was found to strengthen the pelvic floor muscles used to propel the baby through the birth canal. However, Freyder (1989) described how with the progression of pregnancy, the center of gravity was shifted back over the pelvis to prevent falling forward causing a new, unstable posture. It is also mentioned in the literature the effects of the hormones progesterone and relaxin which cause softening of the ligaments and thus less joint stability. The purpose of this study was to compare the biomechanical changes that occurred during and following pregnancy in the sport of cycling. The subject in this study was an avid cyclist and was familiar with and trained on bicycle rollers. While cycling on a set of bicycle rollers, the subject was videotaped (60 fps) in the frontal and sagittal planes three times from two to seven months in gestation and two times during the three months after childbirth. Each performance was then digitized and analyzed using the PEAK Performance 2- dimensional movement analysis system interfaced with a Panasonic AG-7350 recorder, Sony PVM-1341 monitor, and Zenith 486 microcomputer. The horizontal and vertical linear displacements of the center of gravity and angular displacements of the right and left hips were compared. It was found that as pregnancy progressed: (a) horizontal and vertical displacements of the center of gravity increased as well as variability, (b) angular displacements of the hips increased, and (c) additional external stabilization of the performer was required. It was concluded that as pregnancy progressed, stability on the bicycle decreased gradually to the point that during the last trimester additional support was required. This research adds to the literature which supports pregnant women continuing their exercise programs that are non-weight bearing during the first two-thirds of their pregnancy but also supports the literature that cautions about the increased risk of injury due to greater instability during the latter stages.