in physical therapy for patients of cerebrovascular , cardiovascular , respiratory or 
 musculoskeletal diseases , assessments of muscle strength and the movement of joints are 
 essential for treatment planning and also for lifestyle guidance . in order to evaluate 
 patient performance , the range of motion test ( rom - t ) is used to assess movement impairment 
 of the joints1 , and the manual muscle test 
 ( mmt ) is used to assess muscle impairment2 . both of these test methods are fundamental skills required of every 
 physical therapist , which they have to master in training schools . the mmt is a manual 
 maneuver to evaluate the strength of the prime mover muscles for a given motion of a joint . the procedures employed in the mmt were determined mainly based on our present knowledge of 
 kinesiology and electromyography ( emg ) . not only in diagnostic tests , the mmt has also been 
 used for muscle training and maintaining muscle strength2 . the muscles involved in finger function are one of the most important tasks for humans , 
 since the function of the hands is strongly related with the quality of life . the mmt of the 
 forearm muscles are also based on emg . however , it is quite difficult to employ emg for 
 muscles located deeply beneath the skin . it is also difficult to discriminate the actual 
 source of the emg detected by surface electrodes3,4,5,6 . recently , magnetic 
 resonance imaging ( mri ) has been used to monitor muscle activities by using the 
 t1 , t2 , and water content values of skeletal muscles that increased 
 after muscle exercise7,8,9 . intensive studies have been 
 conducted on the determination of agonist muscles using the increase in t2 
 values10 , 11 , and takamori detected increases in the t2 weighted mr 
 ( t2w - mr ) image intensity of the extensor digiti minimi muscle after extension 
 exercise of the mp joint of the digitus imnimus12 . in this study , among the mmt for the forearm muscles , we selected 3 mmt for the primary 
 mover muscles confirmed by the emg . in order to confirm the reliability of the mr images , 1 ) 
 the increase in the t2w - mr image intensity was detected after the mmt of the 
 supinator muscle or the pronator teres muscle13 , 
 14 , and 2 ) we also aimed to detect the 
 mmt of a smaller muscle of the forearm , the extensor indicis muscle15 . three healthy male volunteers participated in this study . the age , height , and weight of 
 the subjects averaged 36.4  12.3  years , 172.3  6.9  cm , and 72.3  17.0  kg ( means  sd ) , 
 respectively . the left forearms of the subjects were studied , and the mmt was applied by 
 physical therapists with more than 10  years of experience . the procedures , purpose , and risks associated with the study were explained to 
 all of the subjects , and written consent was obtained prior to the commencement of the 
 study . the study was approved by the human research review board at the dokkyo medical 
 university school of medicine ( no . mr images of each forearm were obtained with a 0.2 t compact mri system ( mrtechnology , 
 tsukuba , japan ) equipped with an oval h solenoidal radiofrequency probe12 . the transverse t2w - mr images 
 were measured using multi - slice spin - echo mr image sequences with a 200  200  mm 
 field - of - view , a 128  128 data matrix , a 39  ms echo - time with a 2,000  ms repetition time , 
 11 slices with an interval 10  mm , a 9.5  mm slice thickness , 1 accumulation and a total image 
 acquisition time of 4  min 16 s. each left forearm was fixed by a shell - type holder of the 
 forearm12 , and a t2w - mr 
 image in the resting condition was measured at first . then , manipulative isometric 
 contraction exercise ( 5 sec duration ) was applied to the supinator muscle , the pronator 
 teres muscle or the extensor indicis muscle using borg s rating of perceived exertion ( rpe ) 
 scale of 151716 . immediately after the 
 exercise , the arm position was restored to the original position , and another 
 t2w - mr image was measured . the increase in the t2w - mr image intensity 
 of muscle was evaluated by 3 physical therapists ( m.t . , s.a . and k.y . ) with 45 years of 
 experiences with 0.2 t mri . the epimysium of the muscle was traced by hand , and used for the 
 same trace for the t2w - mr image of the resting muscle . the image intensity of a 
 circular region of interest ( roi ) with 25 pixels was measured by imagej software 1.46r ( nih , 
 bethesda , usa ) . in each slice , 3 rois were set in the muscle without overlapping each other , 
 and the average image intensity ( cm ) was obtained . in the same slice , an roi was 
 set in the background and sd ( sdair ) was obtained . the image intensity of the 
 muscle was represented by the signal - to - noise ratio ( snr ) : i = cm / 
 sdair17 . an image intensity 
 outside of the 99.9% of confidence interval ( ir  3.3 ) was considered as a 
 significant increase ( cl=99.9% ) , and an image intensity within 99.9% of the 
 confidence interval was considered not significant ( n.s . ) , where ir was the snr 
 for resting muscle . t2w - mr images of the supinator muscle ( a ) , the pronator teres 
 muscle ( b ) and the extensor indicis muscle ( c ) of the subject # 1 . ( i ) 
 t2w - mr images before the exercise , ( ii ) t2w - mr images after the 
 exercise , ( iii ) the trace around muscle ( * ) . represents a typical result of the mmt of the supinator muscle sliced at one - third of 
 the length of the ulna from the olecranon . the subjects were sitting , arm at the side , with the elbow flexed to 
 90 , and the forearm in full pronation to neutral . then , the examiner supported the elbow , 
 and applied resistance with the heel of the hand over the dorsal ( extensor ) surface at the 
 wrist ( fig . the 
 subjects # 1 , # 2 and # 3 did the exercise 82 , 40 and 40 times until they reached borg s rpe 
 scale of 1517 , respectively . the image intensity of the t2w - mr image increased 
 more than 1.7 times compared with the resting muscle , showing a significant increase 
 ( cl=99.9% ) ( table 
 1atable 1.t2w - mr image intensity before and after exercisesubject#1#2#3a ) supinator musclebefore exercise19.813.516.8after exercise33.530.343.5b)pronator teres musclebefore exercise14.416.725.4after exercise30.930.646.3c)extensor indicis musclebefore exercise15.514.920after exercise29.230.236.6image intensity was represented by the signal - to - noise ratio . no significant changes were shown in the image intensities for the rest of 
 the muscles . transverse t2w - mr images of the supinator muscle ( a ) , the pronator teres 
 muscle ( b ) and the extensor indicis muscle ( c ) of the subject # 1 . ( i ) 
 t2w - mr images before the exercise , ( ii ) t2w - mr images after the 
 exercise , ( iii ) the trace around muscle ( * ) . figure 1b represents a typical result of the mmt 
 of the pronator teres muscle sliced at one - third of the length of the ulna from the 
 olecranon . the function of the pronator teres muscle is to pronate the forearm with the 
 pronator quadratus muscle . the subjects were siting , arm at the side with the elbow flexed 
 to 90 and the forearm in supination . then , the examiner supported the elbow , apply 
 resistance with hypothenar eminence over radius on the volar ( flexor ) surface of the forearm 
 at the wrist ( fig . the 
 subjects # 1 , # 2 and # 3 did the exercise 45 , 40 and 50 times until they reached borg s rpe 
 scale of 1517 , respectively . image intensity of the t2w - mr image increased more 
 than 1.8 times compared with the resting muscle , and represented significant increase 
 ( cl=99.9% ) ( table 1b ) . no 
 significant changes were shown in the image intensity of the rest of the muscles . figure 1c represents a typical result of the mmt 
 of the extensor indicis muscle sliced at two - third of the length of the ulna from the 
 olecranon . the extensor indicis muscle is a deep - layer , narrow skeletal muscle and its 
 function is the extension of the index finger . the subjects were sitting with the forearm in 
 pronation , the wrist in neutral . and the mp and ip joints in a relaxed flexion posture . then , the examiner stabilized the wrist in neutral , and placed the index finger of the 
 resistance hand cross the dorsum of all proximal phalanges just distal to the mp joints , and 
 applied resistance in the direction of the flexion ( fig . the subjects # 1 , # 2 and # 3 did the 
 exercise 40 , 40 and 40 times until they reached borg s rpe scale of 1517 , respectively . the 
 image intensity of the t2w - mr image increased more than 1.8 times compared with 
 the resting muscle , showing a significant increase ( cl=99.9% ) ( table 1c ) . no significant changes were shown in the 
 image intensity of the rest of the muscles . in this study , the t2w - mr image intensity of the supinator muscle , the pronator 
 teres muscle and the extensor indicis muscle increased ( cl=99.9% ) with the 
 mmt for these muscles with borg s rep scale of 1517 . we did not 
 detect any increases in the image intensity of the rest of the muscles . since the first report by lovett in 191518 , the mmt has been applied to evaluate the musculoskeletal and 
 nervous systems , and the reliability and validity of the mmt is well established19 . the mmt depends on manual procedures for 
 joint motion , such as flexion of the mp joint . although the prime movers of a movement can 
 be identified , secondary or accessory movers may be equally important , but definitive 
 studies remain incomplete2 . compared with 
 emg , mri can image all of the muscles in a single fov in the arm . moreover , we can observe 
 11 slices simultaneously along the longitudinal axis of the forearm using a multi - slice 
 spin - echo mr sequence . thus , mri can detect secondary or accessory movers located even 
 distant from the primary movers in the same fov . therefore , even with a low number of 
 subjects , the 3 in this study , we can conclude that muscle activity was not detected in 
 other than the primary mover muscles of the 3 mmt used in this study . it can be considered 
 that the strength of the manual resistance of the mmt is important . in a previous 
 report12 , the mmt for the extensor 
 digiti minimi muscle was applied until the subjects were unable to continue the extension of 
 the digitus minimus . as a result , we detected other muscle activity in the extensor carpi 
 ulnaris muscle that acts to extend and adduct at the carpus , in addition to the extension of 
 the digitus minimus . therefore , in this study , we adjusted the strength of the exercise to 
 borg s rpe scale of 1517 , as that might be suitable for the mmt of the extensor indicis 
 muscle . the results of this study suggest that mr imaging could be useful in training 
 physical therapists in using the mmt , because muscle activity can be visualized by mr 
 images . we plan to study using the mmt for these muscles , such as 
 the flexor carpi radialis muscle and the flexor carpi ulnaris muscle . in these muscles , we 
 can expect activity due to not only the primary mover muscles , but also accessory muscles . it can be considered that mri technique will be useful to analyze mmt results , since we need 
 not predict specific candidate muscles . thus , mri techniques should be useful to increase 
 the reliability of the mmt .
[ purpose ] in order to detect muscle activity with manual muscle testing , 
 t2-weighted magnetic resonance ( t2w - mr ) images were detected by a 
 0.2 t compact mri system . 
 [ subjects and methods ] the subjects were 3 adult males . 
 transverse t2-weighted multi - slice spin - echo images of the left forearm were 
 measured by a 39  ms echo - time with a 2,000  ms repetition time , a 9.5  mm slice thickness , 1 
 accumulation and a total image acquisition time of 4  min 16 s. first , t2w - mr 
 images in the resting condition were measured . 
 then , manipulative isometric contraction 
 exercise ( 5 sec duration ) to the supinator muscle , the pronator teres muscle or the 
 extensor indicis muscle was performed using borg s rating of perceived exertion ( rpe ) 
 scale of 1517 . 
 the t2w - mr images were measured immediately after the exercise . 
 [ results ] t2w - mr image intensities increased significantly in the supinator 
 muscle , the pronator teres muscle and the extensor indicis muscle after the exercise . 
 however , the image intensities in the rest of the muscle did not change . 
 [ conclusion ] 
 using t2w - mr images , we could detect muscle activity in a deep muscle , the 
 supinator muscle , and a small muscle , the extensor indicis muscle . 
 these results also 
 support the reliability of the manual muscle testing method .