sports injuries in cyclists are frequently caused by an abnormal cycling position in which 
 a repetitive motion occurs with a relatively fixed knee position and insufficient muscular 
 endurance in the lower limbs1 .
an incorrectly set saddle height can cause 
 a considerable strain on the knees and lead to knee overuse injury3 .
the knee joint provides power to pedal and drive a bike 
 during cycling ; however , knee overuse is a common sports injury4 .
therefore , the height of the cyclist s saddle is critical 
 to preventing sports injury .
the height of the cyclist s saddle is also critical for optimizing performance and reducing 
 the risk of knee overuse injury during cycling5 .
one study indicated that effective prevention of knee injury 
 entails setting the bottom dead point of the pedal at a position6 , that allows the knee to be flexed between 25 and 35. 
 another study recommended that the saddle height permit 2535 knee flexion and determined 
 that a knee angle closer to 25 than 35 facilitated sports performance and injury 
 prevention7 . during cycling , the bike must fit a cyclist as possible , which could have optimal sports 
 performance8 . whether professional or 
 amateur , cyclists seek techniques for improving their cycling performance .
the optimal 
 pedaling rhythm is one that maintains the minimum pedaling force requirements to provide 
 bike power .
this allows cyclists to use slow - twitch fibers for primary muscle power , and 
 this allows anaerobic capability to be reserved to delay exercise fatigue9 . because cycling exercise is a prolonged 
 physical activity , a stable cycling speed is essential to maintaining the fitness of the 
 cyclist , who must compensate for exercise fatigue through riding posture and chaotic 
 pedaling rhythms , thereby affecting individual or team performance10 .
adequate fitness and muscular endurance are critical to 
 fundamental athletic performance11 , 12 , with external factors such as bicycle 
 architecture also affecting performance13 .
previous studies have frequently explored seat height and 
 demonstrated that inappropriate seat height could affect cycling performance14 , 15 .
therefore , our study compared the variance in cadence frequency after exercise 
 fatigue between saddle heights with 25 and 35 knee flexion .
the results may elucidate the 
 positive effect of a suitable saddle height for cyclists . the variance in cadence frequency 

was hypothesized to be less for a saddle height with 25 knee flexion than that for one with 
 35 knee flexion .
this study adopted a crossover design to assess the difference in cadence frequency between 
 the two saddle heights among healthy college students aged older than 20  years .
all 
 participants provided informed consent before the study , and the procedure was approved by 
 the research ethics committee of a hospital .
the exclusion criteria were a history of lower limb injury , an 
 anterior or lateral cruciate ligament tear , a meniscus lesion or ankle ligament tear , or 
 cardiovascular disease .
the variable in this study was saddle height , which was set at two different heights by 
 setting the pedal at the bottom dead point with 35 or 25 knee flexion , respectively ( fig .
the participants were randomly assigned to test each saddle height ( i.e. , with 25 
 or 35 knee flexion ) for 2 days , with a 2-day rest between testing of the two cycling 
 protocols to avoid muscle fatigue . a cadence bike sensor ( edge 510 , garmin , olathe , ks , usa ) 
 with a heart rate sensor was used , and a 10-grade rating of perceived exertion ( rpe ) was 
 adopted for assessing exercise fatigue . the heart rate reaching 90% of its predicted maximum 
 and the rpe reaching a grade of 7 were used for judgment of exercise fatigue16 .
saddle height setting (  
 is 35 or 25 knee flexion ) the participants were asked to pedal to fatigue in the cycling exercise , and the cadence 
 frequency was recorded from the start of a 5-minute warm - up period until 5 minutes after 
 inducing exercise fatigue . before the exercise began ,
the protocol was explained to the 
 participants in detail , alerting them to precautions and informing them of the assessment 
 project .
each participant was allowed to ride a stationary bike and set the saddle height 
 before adjusting the amount of resistance ( 7 grades ) requesting that the participant 
 maintain a cadence frequency of 85  rpm , which is a common training model for cyclists .
after 
 the resistance and saddle height were properly adjusted , recording of the cadence frequency 
 was started for the 5-minute warm - up .
after exercise fatigue was induced , recoding of the 
 cadence frequency was continued for 5 minutes of exercise fatigue .
the relative variance of the cadence frequency was 
 calculated as the current cadence frequency  the set cadence frequency ( 85  rpm ) .
this 
 equation denotes the pedaling efficiency , which was calculated at the end of the 5-minute 
 warm - up period and 5 minutes after inducing exercise fatigue .
the data obtained were analyzed using the spss version 15 software ( spss , inc .
descriptive statistics ( i.e. , mean and standard deviation ) of the participants 
 demographic data were calculated .
the wilcoxon test was used , and the  value was set at 
 0.05 . comparing the absolute values of cadence frequency under the two conditions with the 
 two saddle heights
ten healthy college students ( age = 22.5  0.9 , weight = 61.3  5.1  kg , and height = 169.3 
  5.1  cm ) were recruited and randomly performed the cycling protocols , which entailed 
 cycling with a saddle height set to allow 25 or 35 knee flexion .
the relative variance in 
 cadence frequency denoted the difference between the actual and set cadence frequencies .
comparison of the variance in cadence frequency for saddle 
 heights with 25 or 35 knee flexion revealed no significant difference after the 5-minute 
 warm - up ( table 1table 1.absolute values of relative variance of cadence frequencysaddle height with 25knee flexion ( n = 10)saddle height with 35 knee flexion ( n = 10)5-min warm - up2.62  1.252.53  1.765 minutes after inducing exercise fatigue2.32  1.834.21  2.65**p < 0.05 , saddle heights with 25 vs. 35 knee flexion .  
p < 0.05 , 5-min warm - up vs. 5-min exercise fatigue ) . a significant difference was found using the saddle height with 35 knee 
 flexion after the 5-minute warm - up and 5 minutes after inducing exercise fatigue ( p = 
 0.001 ) . comparing the mean and standard deviation of the cadence frequency after the 
 5-minute warm - up and 5 minutes after inducing exercise fatigue revealed a significant 
 difference between the saddle heights with 25 and 35 knee flexion ( p = 0.001 ) . * p < 0.05 , saddle heights with 25 vs. 35 knee flexion .  
a saddle height with 35 knee flexion means that the cyclist is seated at a lower saddle 
 height , with the knees remaining flexed during peddling .
a saddle height with 25 knee 
 flexion means that the cyclist is seated at a higher saddle height , with the knees extending 
 during peddling .
a cyclist seated at a saddle height with 35 knee flexion maintains a long 
 quadriceps muscle length .
according to the muscular length - tension ratio , when the length of 
 the muscle surpasses its primary length , passive elastic tension in the muscle initiates 
 factors that cause a greater contraction force17 , 
 18 .
our results indicated that the saddle 
 height with 35 knee flexion had a relatively high variance in cadence frequency , meaning an 
 increase in chaotic pedaling rhythms . when the knee is almost fully extended , cycling is 
 perceived to be easier and is more effective , indicating that a high saddle height results 
 in reduced muscular work19 .
found that anaerobic power in a graded exercise protocol was significantly lower for a 
 saddle height with 25 knee flexion than for one with 35 knee flexion7 . in the current study
, the current findings supported to the 
 idea that a saddle height with 35 knee flexion would increase power consumption , resulting 
 in an increased relative variance in cadence frequency 5 minutes after inducing exercise 
 fatigue .
however , the saddle height with 25 knee flexion exhibited a significantly lower 
 relative variance in cadence frequency than the saddle height with 35 knee flexion . 

therefore , cycling with a low saddle height could reduce chaotic pedaling rhythms during 
 exercise fatigue , thus benefiting cycling performance .
an incorrect saddle height can exert considerable strain on the knee joint , resulting in an 
 increase of overuse injuries20 .
although 
 the current study did not explore the effects of different saddle heights on injury 
 prevention , an experimental study established that a saddle height with 2535 knee flexion 
 is ideal for injury prevention21 . 

however , some studies have recommended a saddle height with 25 knee flexion for injury 
 prevention6 , 20 .
an overly low saddle height can cause anterior knee pain from 
 increased compression of the knee joint as the cyclist pushes through the top of the pedal 
 stroke7 .
holmes et al . thought that low 
 saddle heights had a high risk of knee overcompression when cycling , which could also result 
 in overuse injuries involving cyclists knee joints22 .
found that increasing saddle height could result in 
 large increases in the index of cyclists effectiveness23 .
the results of the current study reveal that a saddle height with 
 25 knee flexion had a lower relative variance in cadence frequency , and it was presumed 
 that high saddle heights could reduce chaotic pedaling rhythms during exercise fatigue . 

although this study did not investigate the relationship between saddle height and knee 
 injury , most evidence - based studies have supported using saddle heights with 25 knee 
 flexion for beneficial effects in both performance and injury prevention . after inducing exercise fatigue ,
the relative variance in cadence frequency for saddle 
 heights with 35 knee flexion was higher than that for saddle heights with 25 knee flexion . 

. the limitations of 
 our study were the small sample size and the short cycling duration , which was selected 
 because it is difficult to observe exercise fatigue during long - distance cycling .
 [ purpose ] bicycle saddle height is a critical factor for cycling performance and injury 
 prevention . 
 the present study compared the variance in cadence frequency after exercise 
 fatigue between saddle heights with 25 and 35 knee flexion . 
 [ methods ] two saddle 
 heights , which were determined by setting the pedal at the bottom dead point with 35 and 
 25 knee flexion , were used for testing . 
 the relative variances of the cadence frequency 
 were calculated at the end of a 5-minute warm - up period and 5 minutes after inducing 
 exercise fatigue . 
 comparison of the absolute values of the cadence frequency under the two 
 saddle heights revealed a difference in pedaling efficiency . 
 [ results ] five minutes after 
 inducing exercise fatigue , the relative variances of the cadence frequency for the saddle 
 height with 35 knee flexion was higher than that for the saddle height with 25 knee 
 flexion . [ conclusion ] the current finding demonstrated that a saddle height with 25 knee 
 flexion is more appropriate for cyclists than a saddle height with 35 knee flexion . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION