Downhill Conditions Research Articles

Kinetic Characteristics of Distance Running on Downhill Slope

The purpose of this study was to investigate kinetic characteristics such as ground reaction forces (GRFs) and joint torques of the lower limb joints in downhill running for distance runners on overground. Six male distance runners were asked to run at three running speeds (3.3, 4.2, and 5.0 m/s) on the slopes of different grades (0, -3.2, -6.4, and -9.1 %) in which two force platforms were mounted. A two dimensional link model was used to calculate joint torques and joint powers of the lower limb joints. In spite that the downward velocity of the CG at the foot contact increased consistently as the grade increased, the impact peak of vertical GRF and the peak loading rate defined as maximum rate of change of the vertical GRF did not increase consistently as the grade increased. The runners on steep downhill conditions would be able to avoid excessive impact load by contacting with the ground in more extended hip position and increasing knee flexion velocity after the foot contact. The negative power of the knee after the foot contact was larger for -9.1 % downhill than the level condition, which revealed the eccentric load on the knee extensors increased in the steep downhill condition. The hip extensors exerted negative power with hip flexion just after the foot contact in -6.4 and -9.1 % downhill conditions so that the runners could absorb the impact force and mechanical energy.

Analysis of Gap Patterns in Longitudinal Rumble Strips to Accommodate Bicycle Travel

Rumble strips can offer significant reductions in run-off-road crashes on rural highways. Newer ground-in rumble strip designs can be installed on a wider variety of shoulders, but these new designs have a much greater negative effect on bicycle traffic than did previous designs. The feasibility of placing gaps in a rumble strip pattern to permit bicycle traffic to cross the rumble strip area without striking the rumble strip pattern itself was investigated. A recommended minimum length for these gaps to accommodate bicyclists of varying abilities at speeds representative of downhill conditions was also determined. On the basis of experimental information collected, the researchers recommend that rumble strips on noncontrolled-access highways include periodic gaps of 3.7 m (12 ft) in length, and that these gaps be placed at periodic intervals at a recommended spacing of 12.2 m (40 ft) or 18.3 m (60 ft).