the rating of perceived exertion ( rpe ) refers to the degree of perception involving a 
 combination of local sensations comprising the circulatory and respiratory systems , 
 metabolic system , skeletal muscles , and the peripheral nervous system1 .
rpe is significantly related to oxygen uptake measurement 
 and the amount of exertion2 , and so it is 
 used to assess and regulate the intensity of physical activity3 .
rpe is an area of active interest for psychologists and physiologists concerning physical 
 activity and sports5 .
information about 
 how individuals perceive their performance may be more important than knowing their actual 
 performance .
subjective perceptual ratings of effort expenditure can be employed as 
 effective predictors of maximal performance .
physiological , physical , and psychological responses and perceptive changes caused by rpe 
 have been studied6 .
rpe is related to the 
 muscle soreness and stiffness after a marathon7 and is increased during shorter , rather than longer , rest 
 intervals8 .
the data support the view 
 that rpe is an indicator for muscle recovery when resistance training is done .
additionally , 
 the order of exercise does not affect the total vo2 , but does affect rpe9 .
results from examination of physical strain 
 associated with high intensity exercise indicate the value of rpe in measuring an 
 individual s maximum number of repetitions and actual relative volume . furthermore , 
 perceived respiratory exertion was shown to not be related to respiratory power output in a 
 previous study but rather to be related to the perceived exertion of the legs , which is 
 related to muscle metabolic conditions10 .
tonic and phasic muscles are usually classified according to the phylogenetic development 
 criteria of janda11 .
these muscles are activated in flexor synergies and 
 involved in repetitive or rhythmic activity12 .
this study was undertaken to investigate the results of isotonic resistance exercise based 
 on the janda classification and theoretical background .
many prior studies have focused on 
 the relationship between rpe and muscle activity , rpe and number of repetitions , and rpe and 
 energy consumption .
however , little is known about the effects of multiple repetitions on 
 muscle activity and rpe during resistance training .
this study investigated the effects of the activity of phasic and tonic muscles and the 
 number of repetitions on rpe during isotonic resistance exercise in young korean adults .
the subjects of this study consisted of 20 males and 20 females with average ages of 
 21.27  1.75  years and 21.09 1.97  years , respectively .
their average heights were 176.84 
  4.80  cm and 164.36  6.17  cm , respectively , and their average weights were 71.57  
 13.34  kg and 59.91  9.17  kg , respectively .
ml / kg / min and 34.15  4.05  ml / kg / min , respectively .
the participants were 
 university students in whom a physician examination had not detected any problems in the 
 upper and lower limbs and muscular skeletal system .
none of the participants were engaging 
 in a regular muscle strengthening routine , and none had any contractures in the upper and 
 lower limbs or spinal column that limited any movements necessary for the current study . 

all participants were instructed about the potential risks and experimental design and 
 provided informed consent for participation , with the knowledge that they could withdraw 
 at any time .
tonic muscles included the 
 iliopsoas , hamstring , gastrocnemius , and pectoralis major muscle .
phasic muscles included 
 the gluteus maximus , quadriceps , tibialis anterior , and rhomboid muscles .
each participant 
 had their maximal dynamic strength ( 1rm ) measured and completed practice trials to become 
 familiar with the isotonic resistance exercise .
the 1rm was measured using the commander 
 powertrack ii ( jtech medical , midvale , ut , usa ) , with the weight increased until the 
 participant could not lift the equipment13 .
each participant was observed by an examiner while exercising , 
 and the intensity of the exercise was set to 70% of their 1rm .
table 1table 1.exercise equipment and electrode attachment area depending on muscle 
 typemuscle typemuscleexercise methodelectrode placementstonic musclepectoralis majorchest presson the chest wall at an oblique angle toward the clavicle , 
 approximately 2 cm below the clavicle , just medial to the axillary fold.hamstringseated leg curlstwo electrodes 3 to 4 cm apart placed parallel to the muscle in 
 the center of the back of the thigh , approximately half the distance from the 
 gluteal fold to the back of the leg.iliopsoasleg raise machinelocate the femoral pulse .
go lateral to this , yet medial to the 
 quadriceps femoris and inferior to the inguinal ligament .
two active electrodes , 
 2 cm apart , are placed parallel to the muscle fibers.gastrocnemiusdonkey calf raisesactive electrodes are placed 2 cm apart , running parallel to the 
 muscle fibers , just distal to the knee and 2 cm medial or lateral to 
 midline.phasic musclelower trapeziuslat pulldown machineplace the electrodes on an oblique angle , approximately 5 cm down 
 from the scapular spine .
the two active electrodes ( 2 cm apart ) are placed next 
 to the medial edge of the scapula at a 55-degree oblique angle.quadriceps ( rectus femoris)seated leg press machineplace the electrodes on the center of the anterior surface of the 
 thigh , approximately half the distance between the knee and the iliac spine .
the 
 two active electrodes are placed 2 cm apart , parallel to the muscle fibers.upper gluteus maximussmith machinetwo active electrodes ( 3 cm apart ) are placed half the distance 
 between the trochanter ( hip ) and the sacral vertebrae in the middle of the 
 muscle on an oblique angle at the level of the trochanter or slightly 
 above.tibialis anteriorpower leg presstwo active electrodes , 2 cm apart , are placed parallel to and 
 just lateral to the medial shaft of the tibia ( shin ) , at approximately 
 one - quarter to one - third the distance between the knee and the ankle .
scottsdale , az , usa ) following the jeffrey guide14 for surface electromyography ( emg ) .
the electrodes were attached 
 after the removal of hair and cleansing of the skin with alcohol .
bipolar ag - agcl surface 
 electrodes ( 10  mm in diameter ) with their included conductivity gel ( noraxon ) were 
 attached following the muscle fiber direction and connected to an emg bipolar amplifier . 

the resulting raw data were processed by full - wave 
 rectification , smoothed using a root mean square ( rms ) algorithm and a window of 100  ms , 
 and then passed through a band - pass filter of 10350hz .
subjects rated their perceived level of muscle activity using the borg scale15 , with fairly light , hard , and very hard 
 scored as 11 , 15 , and 19 , respectively , and a supervisor recoded the number of repetitions 
 at each level .
data were analyzed using the 
 ibm spss statistics version 20.0 statistical software ( ibm corp .
, armonk , ny , usa ) . 
 multiple regression was used to examine the effects of muscle activity and number of 
 repetitions on rpe .
the subjects of this study consisted of 20 males and 20 females with average ages of 
 21.27  1.75  years and 21.09 1.97  years , respectively .
their average heights were 176.84 
  4.80  cm and 164.36  6.17  cm , respectively , and their average weights were 71.57  
 13.34  kg and 59.91  9.17  kg , respectively .
ml / kg / min and 34.15  4.05  ml / kg / min , respectively .
the participants were 
 university students in whom a physician examination had not detected any problems in the 
 upper and lower limbs and muscular skeletal system .
none of the participants were engaging 
 in a regular muscle strengthening routine , and none had any contractures in the upper and 
 lower limbs or spinal column that limited any movements necessary for the current study . 

all participants were instructed about the potential risks and experimental design and 
 provided informed consent for participation , with the knowledge that they could withdraw 
 at any time .
tonic muscles included the 
 iliopsoas , hamstring , gastrocnemius , and pectoralis major muscle .
phasic muscles included 
 the gluteus maximus , quadriceps , tibialis anterior , and rhomboid muscles .
each participant 
 had their maximal dynamic strength ( 1rm ) measured and completed practice trials to become 
 familiar with the isotonic resistance exercise .
the 1rm was measured using the commander 
 powertrack ii ( jtech medical , midvale , ut , usa ) , with the weight increased until the 
 participant could not lift the equipment13 .
each participant was observed by an examiner while exercising , 
 and the intensity of the exercise was set to 70% of their 1rm .
table 1table 1.exercise equipment and electrode attachment area depending on muscle 
 typemuscle typemuscleexercise methodelectrode placementstonic musclepectoralis majorchest presson the chest wall at an oblique angle toward the clavicle , 
 approximately 2 cm below the clavicle , just medial to the axillary fold.hamstringseated leg curlstwo electrodes 3 to 4 cm apart placed parallel to the muscle in 
 the center of the back of the thigh , approximately half the distance from the 
 gluteal fold to the back of the leg.iliopsoasleg raise machinelocate the femoral pulse .
go lateral to this , yet medial to the 
 quadriceps femoris and inferior to the inguinal ligament .
two active electrodes , 
 2 cm apart , are placed parallel to the muscle fibers.gastrocnemiusdonkey calf raisesactive electrodes are placed 2 cm apart , running parallel to the 
 muscle fibers , just distal to the knee and 2 cm medial or lateral to 
 midline.phasic musclelower trapeziuslat pulldown machineplace the electrodes on an oblique angle , approximately 5 cm down 
 from the scapular spine .
the two active electrodes ( 2 cm apart ) are placed next 
 to the medial edge of the scapula at a 55-degree oblique angle.quadriceps ( rectus femoris)seated leg press machineplace the electrodes on the center of the anterior surface of the 
 thigh , approximately half the distance between the knee and the iliac spine .
the 
 two active electrodes are placed 2 cm apart , parallel to the muscle fibers.upper gluteus maximussmith machinetwo active electrodes ( 3 cm apart ) are placed half the distance 
 between the trochanter ( hip ) and the sacral vertebrae in the middle of the 
 muscle on an oblique angle at the level of the trochanter or slightly 
 above.tibialis anteriorpower leg presstwo active electrodes , 2 cm apart , are placed parallel to and 
 just lateral to the medial shaft of the tibia ( shin ) , at approximately 
 one - quarter to one - third the distance between the knee and the ankle .
scottsdale , az , usa ) following the jeffrey guide14 for surface electromyography ( emg ) .
the electrodes were attached 
 after the removal of hair and cleansing of the skin with alcohol .
bipolar ag - agcl surface 
 electrodes ( 10  mm in diameter ) with their included conductivity gel ( noraxon ) were 
 attached following the muscle fiber direction and connected to an emg bipolar amplifier . 

the resulting raw data were processed by full - wave 
 rectification , smoothed using a root mean square ( rms ) algorithm and a window of 100  ms , 
 and then passed through a band - pass filter of 10350hz .
subjects rated their perceived level of muscle activity using the borg scale15 , with fairly light , hard , and very hard 
 scored as 11 , 15 , and 19 , respectively , and a supervisor recoded the number of repetitions 
 at each level .
data were analyzed using the 
 ibm spss statistics version 20.0 statistical software ( ibm corp .
, armonk , ny , usa ) . 
 multiple regression was used to examine the effects of muscle activity and number of 
 repetitions on rpe .
the average ages , heights , weights , and vo2max values of the two groups were 
 comparable .
the results were expressed as whole muscle , tonic muscle , and phasic muscle . for males and females ,
as the number of tonic and phasic muscle repetitions increased , rpe 
 increased , but muscle activity did not show a significant effect except for phasic muscle in 
 woman .
the number of repetitions had a greater effect on rpe than muscle activity ( =0.616 
 and =0.171 , respectively ) in phasic muscle in females ( table 2table 2.multiple regression analysis of factors related to rating of perceived exertion 
 ( rpe ) in total tonic muscle and total phasic muscleindependent variablesbsetotal tonic muslcemnumber of repetitions*0.0340.003electromyography0.0000.006fnumber of repetitions*0.0480.004electromyography0.0000.009total phasic musclemnumber of repetitions*0.0250.002electromyography0.0100.005fnumber of repetitions*0.0260.003electromyography*0.0150.007*p < 0.05 .
m : male ; f : female concerning the iliopsoas muscle of the tonic muscle group , rpe increased in males and 
 females as the number of repetitions increased , but it did not increase as the muscle 
 activity increased . concerning the hamstring of the tonic muscle group , as muscle activity 
 and the number of repetitions increased in men , rpe increased .
the number of repetitions 
 displayed a greater effect than muscle activity ( =0.889 and =0.234 , respectively ; 
 p<0.05 ) . in females , rpe increased as the number of repetitions increased ( p<0.05 ) , 
 but muscle activity did not show a significant effect .
concerning the gastrocnemius muscle , 
 increased muscle activity and number of repetitions increased rpe in males and females . 

however , the number of repetitions ( =0.788 and =0.861 , respectively ) showed a greater 
 influence than muscle activity ( =0.252 and =0.175 , respectively ) ( p<0.05 ) . concerning 
 the pectoralis major muscle ,
an increase in rpe with an increased number of repetitions was 
 evident in men and women ( p<0.05 ) , but muscle activity did not show a significant 
 difference . for the whole tonic muscle group , muscle activity and the number of repetitions 
 had significant effects on rpe but only in the hamstring muscle in men and gastrocnemius 
 muscle in males and females ( table 3table 3.multiple regression analysis of factors related to rating of perceived exertion 
 ( rpe ) in tonic muscleindependent variablesbsetonicmuscleiliopsoasmnumber of repetitions*0.0300.004electromyography0.0050.025fnumber of repetitions*0.0410.006electromyography0.0610.042hamstringmnumber of repetitions*0.0540.006electromyography*0.0360.014fnumber of repetitions*0.0790.010electromyography0.0370.021gastrocnemiusmnumber of repetitions*0.0490.005electromyography*0.0450.015fnumber of repetitions*0.0850.008electromyography*0.0600.029pectoralis major mnumber of repetitions*0.0350.004electromyography0.0010.015fnumber of repetitions*0.0460.008electromyography0.0170.019*p < 0.05 .
m : male ; f : female in the phasic muscle group , the gluteus maximus muscle showed an increased rpe as the 
 number of repetitions increased in males and females ( p<0.05 ) , but muscle activity did 
 not show any significance .
the rhomboid muscle in men displayed an increased rpe with increased 
 muscle activity and number of repetitions , with repetition showing a greater influence 
 ( =0.550 ) than muscle activity ( =0.418 ) . in women
, rhomboid muscle activity did not show 
 any significance ( table 4table 4.multiple regression analysis of factors related to rating of perceived exertion 
 ( rpe ) in phasic muscleindependent variablesbsephasicmusclegluteus maximus mnumber of repetitions*0.0440.004electromyography0.0070.007fnumber of repetitions*0.0380.004electromyography0.0110.017quadriceps mnumber of repetitions*0.0560.008electromyography0.0070.017fnumber of repetitions*0.1050.010electromyography0.0340.024tibialis anterior mnumber of repetitions*0.0210.004electromyography0.0160.020fnumber of repetitions*0.0330.004electromyography0.0140.027rhomboid mnumber of repetitions*0.0240.005electromyography*0.0410.012fnumber of repetitions*0.0800.014electromyography0.0030.015*p < 0.05 .
this study investigated the effects of the muscle activity and number of exercise 
 repetitions of the tonic and phasic muscles on the rpe . in the overall comparison between the tonic and phasic muscles , only phasic muscles in 
 females displayed an increased rpe when muscle activity increased .
increased number of 
 repetitions in all muscles of males and females was associated with an increased rpe . in the 
 phasic muscles of females in particular ,
the number of repetitions and muscle activity 
 significantly influenced rpe . in resistance training ,
rpe increases as heart rate 
 increases16 . also , as intensity 
 increases , rpe and muscle activity increase17 .
therefore , it is safe to conclude that as the intensity and heart 
 rate increase , rpe increases .
emg activity can mediate rpe18 , indicating that rpe could be used to regulate the intensity of 
 exercise19 . among the tonic muscle group , the hamstring muscle in men and gastrocnemius muscle in males 
 and females were associated with an increased rpe and increased muscle activity .
rpe was 
 affected by the number of repetitions more than by muscle activity . in the phasic muscle group ,
these results show that when the number of repetitions increases , rpe increases 
 proportionally , which is similar to the results of a previous study20 .
the results were also similar to those of study in which 
 rpe significantly increased as repetitive muscular contractions were performed21 .
males had higher muscular activity than 
 females in every aspect and this is consistent with a prior study21 . however , another study reported a significantly higher 
 rpe in females than in men as the number of repetitions increased22 .
the collective data indicate that rpe can be used 
 effectively to monitor and prescribe resistance exercise23 , 24 and is an effective 
 technique to control the intensity of resistance exercise18 , 25 . to conclude , tonic muscles and phasic muscles have a different effect on rpe through muscle 
 activity and number of repetitions .
. the present 
 study could not compare the characteristics of all the muscles in the phasic and tonic 
 muscle groups . finally ,
because the experimental group only consisted of males and females in their 20s , 
 the results can not be generalized to all ages .
the present results along with those of 
 studies assessing resistance exercise for the elderly26 , aerobic exercise27 , aquatic exercise28 , treadmill walking29 , and muscular exhaustion recovery30 are expanding the knowledge of the relationships of muscle groups 
 with rpe .
 [ purpose ] the aim of this study was to examine the effects of muscle activity and the 
 number of resistance exercise repetitions on perceived exertion in tonic and phasic 
 muscles in young korean adults . [ subjects ] janda s classification system was used to 
 divide 40 korean males and females in their 20s into a tonic muscle group ( 10 males , 10 
 females ) and phasic muscle group ( 10 males , 10 females ) . [ methods ] 
 each participant 
 performed resistance exercise at 70% of maximum exertion for a single repetition . 
 muscle 
 activity and number of repetitions were measured according to the borg rating of perceived 
 exertion scale , with fairly light , hard , and very hard rated as 11 , 15 , and 19 , 
 respectively . 
 multiple regression analysis was performed . 
 [ results ] as the number of tonic 
 and phasic muscle repetitions for males and females and female phasic muscle activity 
 increased , the perceived exertion increased . 
 perceived exertion increased as the number of 
 tonic muscle repetitions and activity of gastrocnemius muscles in males and females and 
 the hamstring in males increased . increased activity of phasic muscles in males and 
 females and rhomboid muscle activity in males 
 was associated with significantly increased 
 perceived exertion . 
 [ conclusion ] muscle activity and number of repetitions affect 
 perceived exertion . 
 the perception of exertion differs by muscle type and can differ by 
 gender . 
 the influence of the number of repetitions exceeds that of muscle activity . 
INTRODUCTION
SUBJECTS AND METHODS
Subjects
RESULTS
DISCUSSION