Redistribution of intra- and inter-limb support moments during downhill walking on different slopes

Downhill walking presents a greater risk of falling as a result of slipping or loss of balance in comparison with level walking. The current study aimed to investigate the effects of inclination angles on the intra-limb (inter-joint) and inter-limb sharing of the body support during downhill walking for a better understanding of the associated control strategy. Fifteen young male adults (age: 32.6±5.2 years, height: 168.9±5.5cm, mass: 68.4±8.7kg) performed level and downhill walking while their kinematic and kinetic data were measured for calculating joint moments and total support moments of the lower limbs using inverse dynamics analysis. The peak total support moments of both the leading and trailing limbs increased with increasing inclination angles (p<0.05) with different sharing patterns among individual joints. Being the major contributor to the peak total support moment during early single-limb support, the contribution of the knee remained unaltered (p>0.05), but the contributions of the hip increased with reduced contributions from the ankle (p<0.05). For the increased peak total support moment during late single-limb support, the intra-limb sharing changed from a major ankle contribution to a major knee contribution strategy. The hip contribution was also increased (p<0.05) but the hip flexor moment remained unaltered (p>0.05). During double-limb support, the main contributor to the whole body support changed from the trailing limb to the leading limb with increasing inclination angles (p<0.05).