The Characteristics Of Energy Consumption And Muscular Contraction Pattern Of Lower Limbs During Loaded And Slope Walking

Purpose:To explore the human energy consumption,the main muscular contraction pattern and fatigue of lower limbs during loaded walking of different speeds and slopes.Methods:11 subjects of Beijing sports university students were selected from physical fitness test,was tested on 0°,5° and 10° slopes at the speed of 4.6 km/h and 5.6 km/h under loading 25 kg.The energy consumption indexes and the EMG indexes of different gaits in the first,third,fifth and seventh minutes were recorded during the experiment.Two-Factor Analysis of Variance and simple effect comparison,one-way anova,curve estimation and multi linear stepwise regression were used to process the data.Results:(1)The greater the speed,the higher the slope,the greater the impact on cardiopulmonary function,such as VO2,HR,RQ and MET.Velocity increase 1 km/h,the energy consumption increases 20.92%,20.49%and 4.22%(under the 0°,5°and10°slope).Every 1 increase of slope,the energy consumption increased by 10.31%at 4.6 km/h and 7.50%at 4.6 km/h.(2)In the process of load-carriage walking,speed has little influence on the driving mode,while slope has relatively large influence on the driving mode.The force generation mode under low and medium slope condition is that:tibia anterior muscle>gastrocnemius>rectus femoris>hamstring.The force generation mode under heavy slope condition is that:gastrocnemius>rectus femoris>tibia anterior muscle>hamstring.(3)In load-carriage walking,tibia anterior muscle is more prone to fatigue(k=-2.33→k=-3.30)with the increase of speed load and time load at 0°slope,and rectus femoris is more prone to fatigue(k=-1.69→k=-1.77)with the increase of speed load and time load at 5° slope.Fatigue prone position will change under different slope conditions.The fatigue of tibialis anterior muscle was more pronounced(k=-2.33)with time in the condition of 0°slope.When the slope increases to 5° slope,the fatigue trend of tibialis anterior muscle is relatively weakened(k=-1.80)with the increase of time load.The fatigue trend of rectus femoris increased significantly(k=-1.69),and the fatigue trend of rectus femoris reached the maximum and the most obvious(k=-4.01)at 10° slope.Conclusions:(1)In load carriage walking,the human energy consumption was discrepant at different speeds and slopes.The quantitative effect of complex terrain on oxygen(Y1)and energy(Y2 and Y3)consumption can be predicted by velocity and slope data:Y1=[-119.56-2.12*slope+0.08*slope ^2+0.36*velocity^2-42.77*height ^2+heart rate*(0.69+0.01*slope+0.017*velocity-0.25*height)+height*(128.16-1.4*slope-2.06*velocity)+velocity*(3.23+0.18*slope)]*time;Y2=(-57.4*weight+13.65*slope*weight+29.23*velocity*weight +252.88*height*weight-5.43*weight ^2)*time/1000;Y3=(209.65*weight+8.93*slope*weight+20.83*velocity*weight+0.88*heart rate*weight-4.2*weight ^2)*time/1000.(2)The speed has little effect on force generation mode under loading condition(tibia anterior muscle>gastrocnemius>rectus femoris>hamstring).Tibia anterior muscle and gastrocnemius are the main force generating muscle group at 0° and 5°slope.The main muscle groups are gastrocnemius and rectus femoris at 5°and 10° slope.(3)Tibia anterior muscle was prone to fatigue at 0°and 5°slope under loading condition.Rectus femoris muscle was more prone to fatigue at 5°and 10°slope(4.6 km/h).