cycle ergometer exercise is very consistent since it comprises constant movement in a 
 sitting position , which reduces the load on joints1 and has a low risk of falls ; the load and pedaling types are readily 
 controllable . therefore , the cycle ergometer is appropriate for elderly persons , who tend to 
 have reduced exercise ability compared with the young . age - related weakening of the 
 lower - limb muscles causes physical deterioration and postural and movement instability . therefore , it is necessary for the elderly to perform suitable lower limb 
 muscle - strengthening exercises , which can improve the quality of life2 . cycle ergometer exercise activates mainly the hamstring , 
 vastus lateralis , tibialis anterior , and gastrocnemius muscles due to movement of the hip , 
 knee , and ankle joints . cycle exercise has been reported to increase endurance , heart function , and balance and gait 
 function , as well as muscle and physical strength3 . cycle ergometer exercise is similar to walking since it involves 
 repetitive flexion and extension by alternating contraction of antagonistic muscles4 . therefore , cycle ergometer exercise is 
 suitable for enhancing muscle strength in the elderly . improper pedaling postures 
 affect joint movement ; thus , excessive contraction and relaxation of muscles due to 
 immoderate joint movement can lead to injury . the likelihood of injury due to improper 
 pedaling posture is increased in the elderly because of low bone density and muscle 
 weakness . therefore , proper pedaling posture is more important for the elderly than the 
 young . many studies have been conducted on the pedaling characteristics in the young and the 
 elderly . published studies have addressed the difference in cadence efficiency between the 
 young and the elderly using power and oxygen consumption7 , and the leg muscle activities in the elderly performing cycle 
 ergometer exercise2 . for the determination of proper pedaling posture , the index of effectiveness ( ie ) is a suitable variable for 
 studying pedal force4 . the direction and magnitude of pedal force depends 
 on the movement of the joint and the activation of muscles , and it is necessary to 
 investigate the pedaling characteristics of the elderly due to age - associated changes5 . to investigate pedaling characteristics , 
 kinematic and pedal force analysis thus , the purpose of this study was to compare 
 the joint angle , range of motion ( rom ) , and pedaling effectiveness in the young and the 
 elderly using ie under identical cycling conditions . the study involved 8 young male adults ( age : 26.3  0.7  years , height : 174.6  5.3  cm , 
 weight : 70.5  11.2  cm ) and 8 elderly male adults ( age : 76.4  5.1  years , height : 163.3  
 4.6  cm , weight : 63.8  5.0  cm ) with no history of musculoskeletal disease and who could 
 pedal normally . the protocol for this study was approved by the ethics committee of konkuk 
 university . experimental procedures were explained to the subjects , and written consents 
 were obtained . a 3-dimensional ( 3d ) motion analysis system with 6 infrared cameras ( motion analysis corp . , usa ) and a 3-axis pedal force plate ( dacell corp , korea ) ( hysteresis :  0.5% , nonlinearity : 
  0.5% ) were used to acquire kinematic and pedal reaction force data at the frequencies of 
 120  hz and 1,200  hz , respectively . twenty - three reflective markers were attached as a 
 plug - in set , and pedaling was conducted over 3  min at 40  rpm . the saddle height was set to a 
 155 knee flexion angle ( identical to the 25 knee angle method that is generally accepted 
 for saddle height with proper posture8 ) 
 with the pedal crank at the 6 oclock position . i - magic trainer ( tacx , netherlands ) and srm 
 power meter ( srm , germany ) were used to maintain constant conditions . knee and ankle ranges 
 of motion ( roms ) and angles of the lower joints were calculated using motion data . ie has 
 been used as a measure of effective pedaling4 , and is defined as the ratio of the force perpendicular to the crank 
 ( effective force , ef ) and the total force applied to the pedal ( resultant force , rf ) over a 
 complete crank revolution6 , 7 ( fig . definition of joint angle and pedal force during pedaling , when the pedal is located at the top of the crank ( 0 ) , the position is 
 called the top dead center , and when at the bottom of the crank ( 180 ) , the bottom dead 
 center . the pedaling phase can be divided into the power phase for propulsion ( 30150 ) and 
 the recovery phase for restoration ( 210330 ) . in this study , pedaling was divided into the 
 following 4 phases : phase 1 ( 33030 ) , phase 2 ( 30150 , power phase ) , phase 3 ( 150210 ) , 
 and phase 4 ( 210330 , recovery phase ) , as shown in fig . 2.average force pattern in the young and elderly during pedaling . in general , phase 2 is a propulsive phase and phase 4 is a recovery phase9 . data were statistically analyzed using spss 
 ( ibm co. , usa ) version 22 , and a p - value less than 0.05 was considered to indicate 
 significance for all cases . kinematic results showed that knee rom , ankle rom , maximum knee extension , and maximum 
 ankle dorsiflexion in the elderly were significantly decreased compared with those in the 
 young ( table 1table 1.significant differences in kinematic variables between the young and elderly 
 ( mean  sd)kinematicsknee romknee flexion maxknee extension maxankle romdorsiflexion maxplantar flexion max20s mean71.43  3.17 * 86.25  5.31157.68  5.39 * 30.04  7.90 * 20.45  4.92*9.59  8.3870s mean65.22  6.54 * 80.78  7.80146.01  9.81 * 20.33  6.62 * 17.37  8.71*3.20  9.53t - test , * p<0.05 , unit : degree ) . however , there were no significant differences in maximum knee flexion and 
 maximum ankle plantar flexion . t - test , * p<0.05 , unit : degree there were significant differences in ie for the total phase , phase 1 , and phase 4 between 
 the elderly and the young , but no significant differences for phase 2 and phase 3 , as shown 
 in table 2table 2.significant differences in ie variables between the young and elderly ( mean  
 sd)ietotal phasephase1phase2phase3phase420s mean0.34  0.05 * 0.30  0.14 * 0.82  0.030.11  0.100.68  0.06 * 70s mean0.25  0.04 * 0.07  0.13 * 0.79  0.030.08  0.130.78  0.05*t - test , * p<0.05 , unit : dimensionless ratio of effective force to resultant 
 force . the ie of the young was greater than that of the elderly , except in phase 
 3 . t - test , * p<0.05 , unit : dimensionless ratio of effective force to resultant 
 force however , 
 improper pedaling postures can increase the likelihood of injury . to investigate pedaling 
 characteristics , kinematic and pedal force analysis thus , to evaluate the proper 
 pedaling posture for the elderly , this study compared the pedaling efficiency in the elderly 
 with that in the young using ie and kinematic results . the kinematic results showed that the knee rom in the elderly was less than that of young 
 adults ( table 2 ) , because the maximum knee 
 extension in the elderly was less than that of the young . therefore , the elderly could not 
 extend the knee sufficiently during phase 3 , which affects the flexion of the ankle joint . however , there was no significant difference in ie in phase 3 and maximum plantar flexion of 
 the ankle between the 2 groups . the maximum knee flexion during phase 1 was not significantly 
 different between the 2 groups ; however , the maximum dorsiflexion in the young adults was 
 greater than that in the elderly . it is believed that ankle movement had an effect on ie 
 during phase 1 . therefore , ankle joint movement has an effect on the ie ; i.e. , the pedaling 
 effectiveness , rather than knee joint movement . the ankle joint rom in the young was greater 
 than that in the elderly because of activation of the tibialis anterior ( ta ) muscle . ankle 
 joint movement is generally controlled by the agonistic and antagonistic function of the ta 
 muscle and gastrocnemius medialis muscle3 , 10 . the ta muscle is activated at the start of the swing phase and during toe clearance , 
 and ankle joint rom in the elderly is generally reduced during gait3 . this is due to the weakness of the ankle plantar and 
 dorsiflexor muscles in the elderly . aging has a profound effect in terms of decreases in the 
 distribution and properties of muscle fibers , and therefore on pedal force1 . the ankle flexion results in the elderly 
 indicated that ankle movement is less free than that in the young . pedaling is generally carried out by applying a downward force during the propulsive phase 
 ( phase 2 ) and an upward force during the recovery phase ( phase 4 ) . 2 ) during 
 the propulsive phase ( phase 2 ) and relatively efficient pedaling , although the difference 
 was not significant . moreover , the resistive force in the young was greater than that in the 
 elderly . the effective force was negative during phase 3 and phase 4 , which involve 
 application of a resistive force to the pedal5 . the fact that the young pedaled more effectively indicated that the 
 elderly have weak muscles and poorer kinematic movement than the young do . falling is a 
 major cause of morbidity in the elderly , and can result from an abnormal gait . to prevent 
 falls , it is important to increase joint flexibility and muscle activation3 . pedaling can enhance the joint flexibility 
 and muscle strength in the lower extremities . there was a significant difference in joint 
 movements between the 2 groups , particularly in the resistive force of ankle movement . to 
 overcome the resistive force and pull the pedal upward effectively , the use of a cleat or 
 toe clip pedal is recommended , to enhance the power of the pulling muscle . this study compared the pedaling efficiency in the young with that in the elderly using the 
 ie concept . the young pedaled more effectively at all phases than the elderly , except in 
 phases 2 and 3 . to propose an 
 efficient pedaling method for the elderly , a further comparative study using 
 electromyography is underway .