in the leg , the triceps surae muscle group comprises the soleus muscle and the medial and 
 lateral heads of the gastrocnemius .
the lateral head of the gastrocnemius ( gl ) originates 
 from the lateral epicondyle of the femur , and the medial head of the gastrocnemius ( gm ) 
 originates from the medial epicondyle of the femur .
the soleus muscle originates from the 
 posterior aspect of the femoral head , the proximal quarter of the shaft of the fibula a , the 
 tibia s soleal line , and the middle third of its medial border , and the fibrous arch between 
 the tibia and fibula .
these muscles insert on a common tendon known as the achilles 
 tendon1 , which is the largest and 
 strongest human tendon .
neptune et al . , have demonstrated that the soleus primarily 
 generates forward angular momentum , while the gastrocnemius generates backward angular 
 momentum2 .
the difference between the 
 soleus and the gastrocnemius is in their roles in the generation of horizontal and vertical 
 ground reaction forces2 .
the triceps surae 
 therefore plays two roles : first , it contributes to greater plantar flexion torque and 
 stabilizes the ankle ; and second , it allows the rolling forward of the total mass of the 
 foot , lower leg , and body during the stance phase of the gait .
the stance phase has been 
 divided into five phases : the initial contact , loading response , mid stance , terminal 
 stance , and pre - swing3 . from the mid 
 stance to the terminal stance , the largest ankle plantar flexion moment is required to raise 
 the center of the body mass , and the ankle rocker and the forefoot rocker function as 
 forward progression mechanisms during walking .
the standing heel raise , called the  calf raise  
 ( cr ) , is a commonly prescribed exercise for improving the strength and power of the ankle 
 plantar flexors3 .
training to strengthen the muscles of the triceps surae is therefore clinically important . 
 according to perry ,
the ability to perform at least 30 calf raises by in single leg is 
 required to make the muscles strong enough for normal walking4 .
recently , motor learning theory was applied to gait practice in a clinical setting . 

continuous skills were retained nearly perfectly over long intervals . however , discrete 
 skills showed marked performance losses during the same retention intervals4 .
there is extensive evidence in support of 
 body weight - supported treadmill training for gait practice after impairments such as stroke , 
 femoral proximal fracture , and osteoarthritis .
however , in almost all clinical cases , some 
 discrete skill practices , aimed at improving gait ability , are performed in expectation of 
 the transfer of learning before continuous skill practices , such as body weight - supported 
 treadmill training .
transfer of learning is usually defined as the gain ( or loss ) in the 
 capability of performance in one task as a result of practice or experience of some other 
 task . in the transfer of learning
, the degree of the transfer depends on the similarity 
 between the two tasks , and the transfer depends on the number of  identical elements  that 
 exist in common between two tasks5 . 
 however , there was no evidence of the most effective elements for transfer of learning are 
 not known .
ultrasonography is widely used by the physical therapists in both clinical setting and 
 laboratory settings , and many of studies have used to be investigated muscle morphology such 
 as the muscle thickness , width , and area in static condition6,7,8 .
the dynamics of the triceps surae are known to exhibit isometric 
 contractions during motions such as walking , jumping , and running9 , 10 .
fukunaga et al . , 
 reported that in the late stance phase of walking , the triceps surae muscles perform 
 isometric contractions9 .
kawakami et al . , 
 reported that the gastrocnemius performs the isometric contraction during dorsiflexion of 
 the ankle , and a large proportion of the power originates from elastic energy when the 
 tendon is extended10 .
the tendon of the muscle 
 stretches during the major part of the stance phase and recoils in push - off .
the 
 strength of the triceps surae is important for human bipedal locomotion because it is needed 
 to raise the center of body mass through plantar flexion of the ankle .
strength training of 
 the triceps surae to improve motion capability is necessary to maintain the muscle group s 
 isometric contraction during dorsal flexion of the ankle .
the purpose of this study was 
 to find a strength training protocol which maintained isometric contraction of the triceps 
 surae during dorsal flexion of the ankle .
the left feet of 22 healthy normal volunteers ( mean age 22.9  5.1  years ) who did not have 
 orthopedic injuries or lower limb pain , and who provided their informed consent , 
 participated in this study .
all the subjects performed four sets of five repetitions of cr 
 exercise with alterations in the two conditions : rhythm and starting position .
the rhythm of 
 the calf - raise was either 60 or 90 beats per minute ( bpm ) , and was controlled by a digital 
 metronome .
the starting position was either normal standing or standing with the forefoot on 
 a 6  cm pedestal with dorsal flexion of the ankle .
therefore , the four sets were performed at 
 ( 1 ) 60 bpm without a pedestal , ( 2 ) 60 bpm with a pedestal , ( 3 ) 90 bpm without a pedestal , 
 and ( 4 ) 90 bpm with a pedestal .
this 
 study was approved by the ethics committee of morinomiya university ( 2014 - 078 ) .
reflective markers ten millimeters in diameter were mounted over the lateral side of the 
 knee , the lateral malleolus , and the fifth metatarsal head .
the recordings were translated from .avi file 
 format to .jpeg using the free software program , aviutl .
the ankle angle , which was the 
 right angle made by the three markers , was measured using the free image processing software 
 program , image - j ( national institutes of health , washington , dc , usa ) .
the gl muscle 
 fascicle lengths during the crs were recorded using b - mode real - time ultrasonography ( my lab 
 25 , esaote corporation ) , which was synchronized with the digital video camera . 

ultrasonography and digital video camera were both recorded with 30  hz . a linear ultrasound 
 probe
( 12  mhz ) was fixed using fixation devices at both the thickest part of the lower leg 
 and the center of the gl muscle , and the longitudinal axis of the gl muscle was recorded . 

the pennation angle ( the right angle between the fascicle and deep aponeurosis of the gl 
 muscle ) and the thickness of the gl muscle ( the distance from the superficial fascia to the 
 deep aponeurosis ) were measured using image - j . a single examiner blinded to the condition of 
 the cr exercises measured the fascicle length .
this method has high reliability ( intraclass 
 correlation [ icc ] = 0.91 ) , as confirmed in a pilot study .
the fascicle length was calculated 
 using the equation : fascicle length ( l)=acos , 
  : pennation angle  the cr exercise was divided into two or three phases using the kinematics of the ankle .
the 
 first phase was defined as the elevation from the starting position to the peak plantar 
 flexion angle .
the second phase was defined as the down phase from the peak plantar flexion 
 angle to the neutral zero position , and the third phase was defined as the 
 hyper - dorsiflexion phase from the neutral zero position to the maximum dorsi - flexion 
 position .
the excursion of the ankle , peak dorsiflexion angle , plantar flexion angle , and angular 
 velocity during each cr were calculated .
after five repetitions , measurements of each of the 
 three parameters were averaged and the four conditions were compared using one - way anova 
 with bonferroni s correction . moreover ,
the change in of the fascicle length during each cr 
 was calculated . the average change in fascicle length over the five repetitions in each 
 phase
was compared . if the phase which was less of fascicle length changing were shown , 
 using two - way anova with bonferroni s correction .
both the excursion and angular velocity of the ankle showed no significant differences 
 among the four conditions .
the peak ankle dorsiflexion was significantly different between 
 eccentric cr and normal cr ( table 1table 1.the ankle kinematics difference among cr conditionswith pedestalwithout pedestal60 bpm90 bpm60 bpm90 bpmangle excursion ( degrees)42.910.6 * 38.311.535.58.3 * 37.68.5angular velosity ( degrees / sec.)105.023.1 * 125.635.2 * 102.935.4123.030.4maximum dorsi - flex angle ( degrees)19.210.0 * 14.911.8 * 1.12.8 * 0.12.5 * ) .
the change in the fascicle length during the hyper - dorsiflexion phase was 
 significantly smaller than in the other two phases ( fig . 

1.graph of the changing fascicle length during 60 bpm calf raises with a pedestalsolid line ; fascicle length . dashed line ; angle of the ankle .
the fascicle length 
 showed a little change , even the angle of the ankle showed significant changes 
 ( * ) . ) , and the change in the fascicle length was not significantly different between the 
 60 bpm and 90 bpm ( table 2table 2.changing fascicle length difference among three phasesphase 1phase 2phase 360 bpm26.611.520.98.74.03.6 * 90 bpm29.712.718.68.78.13.9 ) .
graph of the changing fascicle length during 60 bpm calf raises with a pedestal solid line ; fascicle length . dashed line ; angle of the ankle .
the fascicle length 
 showed a little change , even the angle of the ankle showed significant changes 
 ( * ) .
viscosity is 
 known to be in proportional to the velocity of materials , and elasticity is known to be in 
 proportional to the magnitude of displacement .
therefore , it was our hypothesis that at the time of 
 isometric contraction , when the fascicle length was increased , the viscosity and elasticity 
 of the skeletal muscles would also be increased . in this study ,
changes in the frequencies of 
 the cr exercises led to changes in the angular velocity , and the change in the starting 
 position led to change in the excursions of the ankle .
the results of the angular velocity 
 and the excursion were significantly different between the starting conditions with and 
 without the pedestal at both frequencies of exercise repetition . moreover , the peak 
 dorsiflexion angle was significantly different between the two pedestal conditions .
crs at the 90 bpm 
 repetitions showed higher muscle viscosity than at 60 bpm conditions .
the cr with pedestal 
 conditions additionally had a as hyper dorsi - flexion phase . during the hyper dorsi - flexion 
 phase ,
this indicates 
 that the typical contraction of the gl during the hyper dorsi - flexion phase was very similar 
 to that of an isometric contraction , while the typical contraction during the elevation 
 phase and drop phase were concentric and eccentric , respectively .
kawakami , et al . , 
 described that the gastrocnemius in plantar - flexion as movement with counter - movement on a 
 sliding board which worked almost isometrically , and that this work was performed through 
 exercise performance by relying on the tendon to storing and releasing elastic energy10 .
, showed that as the 
 intensity of the rebound action at the ankle increased in a drop jump , the tendinosus 
 tissues were further stretched and provided greater speed when shortened , thereby enhancing 
 muscle and tendon unit positive power11 . 

moreover , kawakami reported that subjects learned to effectively use this muscle - tendon 
 interaction for greater work generation by modulating the activation strategy of muscle 
 fibers through practice12 .
therefore , it 
 is our conclusion that the exercise that showed similar with isometric contractions with 
 dorsi - flexion of the ankle should be performed by elderly people and athletes .
eccentric cr exercise is known to improve the strength of the calf muscle and has an 
 evidence base as a conservative treatment for medial tibial stress syndrome13 .
it is possible that eccentric cr exercises have progressed to 
 motor learning of isometric contraction during the counter movement , and improved the 
 release of elastic energy from the achilles tendon during running , jumping , and other 
 athletic activities .
it is possible that typical muscle contraction is not the same throughout the muscles . 

thus , while the midpoints of the muscle belly may showed isometric contraction , the proximal 
 sites of the muscle belly might not always show isometric contraction .
therefore , it was the revelation to 
 observe that the performance of eccentric cr exercise can elicit isometric contractions 
 during the hyper dorsi - flexion phase is important . in future studies , the effect of 
 eccentric cf exercises on athletic performance during activities such as running and jumping 
 should be investigated .
 [ purpose ] the purpose of this study was to find a strength training protocol which 
 maintains isometric contraction of the triceps surae during dorsal flexion of the ankle . 
 [ subjects ] the left feet of 22 young normal volunteers who did not have orthopedic 
 injuries or lower limb pain participated in this study . 
 [ methods ] all subjects performed 
 four sets of five repetitions of four sets calf - raise ( cr ) exercise at were ( 1 ) 60 bpm 
 without a pedestal , ( 2 ) 60 bpm with a pedestal , ( 3 ) 90 bpm without a pedestal , and ( 4 ) 90 
 bpm with a pedestal . 
 the fascicle length of the lateral head of the gastrocnemius and 
 ankle angle were measured using ultrasonography and a video camera . 
 the cr exercise was 
 divided into two or three phases using the kinematics of the ankle . 
 the average change in 
 fascicle length over the five repetitions of each phase were compared . 
 [ results ] the 
 change of the fascicle length during the hyper - dorsiflexion phase was significantly 
 smaller than during the other two phases . [ conclusion ] it is possible that eccentric cr 
 exercises have progressed to motor learning of the isometric contraction during counter 
 movement , and improved the release of elastic energy of the achilles tendon during 
 running , jumping , and other athletic activities . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION