The Joint Kinematics,kinetics And Efficiency During Cycling Of The Aged People

Objective: Nowadays,riding a bicycle has becoming a common and popular physical activity,increasing numbers of older adults use bicycle for both recreational and transportation purposes.It is well known that aging is associated with a decline in skeletal muscle strength and power.These age related impairments may alter the pedaling kinematics and kinetics pattern of the old people.Although cycling has been extensively studied in the last century,the biomechanical considerations for older cyclists was scarce.Therefore,the overall goals of this study were to examine the pedaling kinematics and kinetics,the power output,and the cycling gross efficiency of the old people.The specific aims of this study were to(1)investigate age-related differences in joint action powers and relative joint power contributions to overall cycling power;(2)investigate age-related differences in knee joint load during the cycling;(3)investigate age-related differences in cycling gross efficiency during the cycling.Methods: Forty-eight volunteers who used bicycle more than 30 min per day were recruited and participated the study.Based on their age,participants were divided into young group and older group,each of the 24 person.Each participant performed eight 3 minutes trials which include two workloads of 60 and 100 Watts(W),and four cadence conditions of FC(Free choice cadence,FC),40,60 and 90 RPM in a random order.Data were collected on at least 10 consecutive pedaling cycles from top dead center(0?)to top dead center(360?),which begin during the last 30 seconds of each trial.A customized instrumented bike pedal was used to collected the pedal reaction force.A ten-camera motion analysis system(Vicon Motion Analysis Inc.,UK)was used to acquire three-dimensional kinematics during the cycling test.The K4 b 2(Cosmed,Italy)was used to collected the gas exchange values.All the data were synchronously collected.Results:(1)The relative hip joint power at 40 rpm,FC,60 rpm were significantly higher than at 90 rpm with 60 W power output(P < 0.01),while the knee was inversed.There were no significant differences in the relative hip and knee joint power between the cadences with 100 W power output(P > 0.05).The relative ankle joint power of the both groups increased with the pedaling cadences(P < 0.01).(2)The maximal knee abduction,adduction,internal and external rotation moment were no significant differences between the young and old group(P > 0.05).The maximal knee adduction and internal rotation moment were signifcantly increased with power output(P < 0.01).The maximal knee adduction moment at 90 rpm was signifcantly higher than at 40 rpm,FC,60 rpm with 60 W power output.The maximal knee adduction moment at 40 rpm was signifcantly higher than at FC,60 rpm,90rpm with 90 W power output.The maximal knee internal rotation moment at FC,60 rpm was signifcantly lower than at 40rpm(P < 0.01)and signifcantly higher than at 90rpm(P < 0.01).(3)Gross efficiency(GE)was lower in old group than that in young group at all cadences and at both levels of power output(P < 0.01).With the increase in power output,GE increased in both groups and at all pedaling rates.GE at FC,40 and 60 rpm in both group were greater than 90rpm(P < 0.01).Conclusion:(1)Both the old and young people showed higher reliance on knee joint and lower reliance on hip and ankle joint when cycling at a fast candence with lower power output.The relative joint power of the hip and knee joint didn't change with the pedaling cadences,while the ankle joint increased with the cadences.(2)There were no age-related differences in knee joint load during the cycling.When cycling at a fast candence with lower power output or at a slow candence with higher power output,the maximal knee adduction moment were signifcantly higher than at FC and custom candence.(3)GE was lower in older people than that in young people at all cadences considered and at both levels of power output,aging has a disadvantageous effect on GE.Both the old and young people's GE increased with power output,and peak efficiency was reached at at a lower pedaling cadences,it seems more disadvantageous for them to use high cadences.