You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
toe gripping is defined as a complex motion that involves several muscles , similar to hand 
 gripping .
the muscles involved in the foot include the flexor pollicis brevis , flexor 
 pollicis longus , lumbrical , flexor brevis , and flexor longus1 .
the position in which toe grip strength is measured has been 
 standardized ; the subject is required to sit with the trunk in the vertical position , the 
 hip and knee joints at 90 , and the ankle joint in a neutral position1,2,3,4,5 . however , there are few reports6,7,8 on positions for measuring toe grip strength , and the positions used 
 during these measurements have not been sufficiently investigated .
souma et al.6 reported that the ankle 
 angles in a neutral position and in dorsal flexion were better than plantar flexion in terms 
 of producing the maximum toe grip strength .
nakae et al.7 reported similar levels of muscle strength exerted in the currently 
 used measurement positions , namely sitting with the hips and knees flexed to 90 and the 
 standing position .
studied toe grip strength under the following 3 conditions 
 in order to determine their reproducibility : 90 hip and knee flexion while sitting , 90 hip 
 flexion and knee extension while sitting , and a standing position .
they reported that 90 
 hip and knee flexion while sitting could be exerted and allowed for measurement 
 reproducibility .
however , these reports suggest that the current 90 hip and knee flexion 
 while sitting position is the most suitable limb position for measuring toe grip strength in 
 terms of reproducibility and the ability to exhibit maximum strength8 .
ankle angle is defined as the angle formed between the long axis of the foot and the line 
 of progression9 , with hip and knee 
 rotation and ankle abduction / adduction presumably acting as determining factors . in young 
 adults , the normal ankle angle during walking ranges from 2.6 to 17.410,11,12 .
the muscles involved in the exertion of toe grip strength 
 have been shown to operate from the mid stance to the forward swing phase of the gait 
 cycle13 , contributing to forward 
 propulsion and stance stability , among others .
thus , the amount of toe grip strength exerted 
 on a horizontal surface can be affected by the ankle angle .
nevertheless , nakae et al.7 did not consider the effects of ankle angle 
 in the horizontal plane when comparing between sitting and standing toe grip strength . 

therefore , evidence on the ankle angle while sitting and standing , which focuses on the foot 
 being on a horizontal surface , is needed .
the purposes of this study were to investigate whether toe grip strength and muscle 
 activities are affected by the ankle angle in the horizontal plane in the sitting upright 
 and standing positions .
their age , height , 
 and body weight ( mean  standard deviation ) were 20.8  0.7  years , 159.3  5.8  cm , and 50.9 
  6.2  kg , respectively .
the present study was approved by the ethics committee for human 
 research of tohoku fukushi university ( rs160102 ) , and the subjects provided informed consent 
 to participate .
we synchronously recorded the toe gripping strength of the dominant foot and the emg 
 activity of the ipsilateral lower leg to assess the muscle activities of the rectus femoris , 
 biceps femoris , anterior tibialis , and medial head of the gastrocnemius .
the sitting upright and standing positions were used in the measurement of toe grip 
 strength . for the sitting upright position ,
the subjects were instructed to sit with the 
 trunk vertical and the hip and knee joints at 90. for the standing position , the feet were 
 placed shoulder - width apart , and the ankle was in a neutral position with regard to 
 dorsiflexion and plantar flexion with the arms hanging down at the sides of the trunk . to 
 compensate for the height of the toe grip dynamometer , the height of the leg not being 
 measured was adjusted using a supplemental platform . in each position ,
toe grip strength was 
 assessed in 3 different ankle joint positions between the long axis of the foot and the line 
 of progression in the horizontal plane , namely 10 of internal rotation , 0 , and 10 of 
 external rotation .
after a 
 sufficient number of training trials and adequate rest , the toe gripping strength was 
 measured twice .
the right toe 
 was dominant ; the dominant toe was defined as the toe used to kick a ball . to measure the maximum voluntary contraction ( mvc ) activities of the tibialis anterior and 
 medial head of the gastrocnemius muscle , each subject
was instructed to sit in a chair with 
 the ankle joint in a neutral position and to exert the maximal forces of plantar flexion and 
 dorsiflexion in isometric contraction to resist the forces applied by the examiner in the 
 directions of dorsiflexion and plantar flexion . to measure the mvc activity of the rectus 
 femoris and biceps femoris muscles ,
each subject was instructed to sit in a chair with the 
 hip and knee joints at 90 and to exert the maximal isometric forces of knee extension and 
 flexion in isometric contraction to resist the forces applied by the examiner in the 
 directions of flexion and extension .
muscular activity was measured using a surface emg apparatus ( telemyo g2 , noraxon usa inc . , 

scottsdale , az , usa ) . after confirming adequate skin preparation ( skin resistance of < 5 
 k ) , electrodes ( blue sensor , ambu inc . ,
ballerup , denmark ) were attached to the tibialis 
 anterior , medial head of the gastrocnemius , rectus femoris , and biceps femoris muscles , as 
 described by peroto14 .
the emg signals were collected and transferred to a personal computer using analysis 
 software ( myoresearch xp , noraxon usa inc . ,
scottsdale , az , usa).the bandwidth was 
 10500  hz . the emg signal segment selected and integrated ( iemg ) for analysis was the middle 
 1  s of the entire 3-s duration of continuous maximal toe grip strength exertion .
the muscular activity used for 
 analysis was based on the data for the maximum toe grip strength .
chicago , il , usa ) was used for 
 statistical analysis . the comparison between grip strength and muscle activities during the 
 toe gripping action for position and measurement conditions was performed by using the 
 two - way repeated - measures analysis of variance ( anova ) .
table 1table 1.comparison of each positions and each measurement conditionssitting upright positionstanding positionmain effectinternal rotationneutral positionexternal rotationinternal rotationneutral positionexternal rotationpositionmeasurement conditionstoe gripping strength ( kg)20.03.320.22.621.13.720.23.620.53.220.33.5rectus femoris muscle ( % iemg ) 3.12.0 3.12.0 3.01.610.38.011.39.410.78.6**long head of the biceps femoris muscle ( % iemg)21.612.823.116.123.017.115.58.016.97.217.09.8tibialis anterior muscle ( % iemg)23.116.023.116.123.916.427.218.032.924.730.019.7medial head of the gastrocnemius muscle ( % iemg)54.323.959.720.661.423.131.711.333.810.433.910.7**mean  standard deviation ( sd ) .
* p < 0.05 shows the average and standard deviations of the measured values in the 16 
 subjects . the results of the two - way anova showed significant differences .
a significant 
 main effect was observed in the measurement conditions for the percent integrated 
 electromyography ( % iemg ) of the rectus femoris muscle ( f(2,13 ) = 13.1 , p < 
 0.05 ) and the long head of the biceps femoris ( f(2,13 ) = 28.4 , p < 0.05 ) . 

multiple comparisons revealed that the % iemg of the rectus femoris muscle was significantly 
 higher in the standing position than in the sitting upright position and that the % iemg of 
 the medial head of the gastrocnemius was significantly lower in the standing position than 
 in the sitting upright position ( p < 0.05 ; table 
 1 ) .
* p < 0.05 the results of the two - way anova did not show any significant difference .
a significant 
 main effect was not observed in toe grip strength , % iemg of biceps femoris , and anterior 
 tibialis muscles .
the present study investigated whether toe grip strength and muscle activities are affected 
 by the ankle angle in the horizontal plane in the sitting upright and standing positions . in 
 our analysis ,
these findings suggest that exerted toe grip strength is only slightly affected 
 by the ankle angle in the horizontal plane in the sitting upright and standing positions . 

the present study showed that toe grip strength was not affected by the positions and 
 measurement conditions .
previous studies also demonstrated a similar level of muscle 
 strength exerted in both measurement positions , namely sitting with the hips and knees 
 flexed to 90 and the ankle at its neutral position , and the standing position .
furthermore , the present study demonstrated the new finding that 
 toe grip strength is not affected by changes in ankle angle .
joint movement is limited by , 
 for example , ligaments and joint capsule soft tissues , but this limitation presumably begins 
 after muscles and other soft tissues have been extended .
the subjects in this study were 
 healthy women who demonstrated greater flexibility and range of motion in their joints than 
 the men in previous studies15 , 16 .
the fixed ankle angle positions of 10 of internal 
 rotation , 0 , and 10 of external rotation may not be determining factors of toe grip 
 strength in the present study because of the subjects extraordinary joint flexibility , 
 which allowed them to exert general movement through knee and hip rotation and ankle 
 abduction / adduction .
the muscles with which toe grip strength is exerted ( flexor hallucis 
 brevis , flexor hallucis longus , flexor digitorum brevis , flexor digitorum longus , and 
 lumbricals ) originate in the legs and upper feet and insert into the toes . therefore , as hip 
 and knee joint rotation presumably has a large effect on ankle abduction / adduction , future 
 studies must keep hip and knee joint rotation fixed .
the present study showed that the % iemg of the rectus femoris muscle was significantly 
 higher in the standing position than in the sitting upright position and that the % iemg of 
 the medial head of the gastrocnemius was significantly lower in the standing position than 
 in the sitting upright position .
previous studies also demonstrated that the % iemg of the 
 medial head of the gastrocnemius was significantly lower in the standing position than in 
 the sitting upright position7 .
in addition , the present study revealed was as 
 new knowledge that the % iemg of the rectus femoris muscle was significantly higher in the 
 standing position than in the sitting upright position .
the activities of the quadriceps 
 muscle increase more easily in the standing position than in the sitting upright position 
 because this muscle is an antigravity muscle , the activities of which are controlled in the 
 standing position .
in addition , we inferred the following observations : when measuring toe grip strength in 
 the standing position , the center of gravity can shift posteriorly as toe grip strength is 
 exerted , requiring the subject to bend the forefoot ( including the toes ) . both the ankle and 
 hip joints are used to compensate for this posterior center of gravity , which results in 
 knee joint extension .
the joints should be stabilized when exerting muscular force ; 
 therefore , we feel that by fixing the knee joint in the direction of extension , great toe 
 gripping power can be exerted .
thus , it appears that the quadriceps activity increases to 
 fix the knee in an extended position , that is , to stabilize the knee .
the present results show that the current measurement positions , namely sitting with the 
 trunk vertical and the hip and knee joints at 90 angles and the ankle joint at neutral 
 position , was optimal for measurement because it has the added advantage of facilitating 
 measurement in subjects who are unable to maintain a stable standing posture or have 
 difficulty in standing.our study has some limitations .
first , we were unable to avoid 
 various common problems that negatively affect surface emg , such as resistance of the skin , 
 artifacts , and the effects of proximal muscles .
second , only healthy young women 
 participated ; thus , it is difficult to extrapolate our findings to the general population .
[ purpose ] the aim of this study was to investigate whether toe grip strength and muscle 
 activities are affected by the ankle angle in the horizontal plane in the sitting upright 
 and standing positions . [ subjects ] the subjects were 16 healthy young women . [ methods ] we 
 measured toe grip strength and the maximum voluntary contraction activities of the rectus 
 femoris , biceps femoris , anterior tibialis , and medial head of the gastrocnemius . in 
 addition , we calculated the percent integrated electromyography during foot gripping in 3 
 different ankle joint positions between the long axis of the foot and the line of 
 progression on the horizontal plane , namely 10 of internal rotation , 0 , and 10 of 
 external rotation . 
 [ results ] two - way analysis of variance revealed significant 
 differences . 
 a significant main effect was observed in the measurement conditions for the 
 percent integrated electromyography of the rectus femoris muscle and long head of the 
 biceps femoris . 
 however , two - way analysis of variance did not reveal any significant 
 difference , and a significant main effect was not observed in toe grip strength . 
 
 [ conclusion ] these findings suggest that exerted toe grip strength is only slightly 
 affected by the ankle angle in the horizontal plane in the sitting upright and standing 
 positions . 
 therefore , the current measurement positions were shown to be optimal for 
 measurement .