the level of intramyocellular lipids ( imcl ) , which consists mainly of triglyceride , has been the focus of research in recent years as a physiological marker of skeletal muscle function . in sedentary individuals , in contrast , in lean healthy subjects , imcl levels correlate with maximal oxygen uptake . accordingly , imcl levels do not seem to correlate with a particular factor , but rather reflect various factors . however , at least under certain conditions , the level of imcl can be potentially used as a physiological marker in a clinical setting and also as a research tool in the fields of diabetes , obesity and exercise physiology . however , in a clinical setting , all of the mr systems do not always contain measurement instruments for hmrs . for a wide clinical application of imcl , it is important to develop alternative methods to measure these levels . the muscular system consists of various types of muscles that contain different proportions of muscle fiber types . type  i fibers are oxidative slowtwitch fibers containing high imcl and many mitochondria . in contrast , type  ii fibers are glycolytic fasttwitch fibers containing low imcl and have low aerobic capacity . the soleus muscle ( sol ) is a typical muscle containing a high proportion of type  i muscle fibers , whereas the tibialis anterior muscle ( ta ) is a muscle with a relatively high proportion of type  ii fibers . recent studies showed a longer t2 relaxation time for type  i fibers compared with type  ii fibers in animal models and humans . thus , in the present study , we investigated the association between imcl and t2 relaxation time in healthy subjects . the nonobese healthy male subjects were recruited by a bulletin board in juntendo university from 2006 to 2007 and 15 subjects were included . they were in good health as determined by medical history , a physical examination and standard blood chemistry analyses . all subjects gave written informed consent to the study , which was approved by the ethics committee of juntendo university study protocol . each subject was instructed to eat a weight maintained normalfat diet ( 25% fat , 55% carbohydrate , 20% protein ) from 3  days before measurement . then , blood samples were taken after overnight fasting . the imcl levels and t1 , t2 relaxation times were measured by hmrs and mri , respectively ( visart1.5tex v4.40 ; toshiba , tokyo , japan ) . resonance of hmrs was quantified by reference to the methylene signal intensity ( sfat ) , with peaks being observed at approximately 1.25  p.p.m . imcl was quantified by the sfat and using a creatine signal at 3.0  p.p.m . then , peripheral insulin sensitivity was evaluated by a euglycemic hyperinsulinemic clamp ( target plasma glucose level of 95  mg / dl and insulin infusion rate of 100  mu / m / min ) . differences of magnetic resonance data between the sol and ta were compared by the wilcoxon signedrank test . spearman s rank correlation coefficient was used to evaluate the correlations of t1 and t2 with imcl of the ta and sol . the nonobese healthy male subjects were recruited by a bulletin board in juntendo university from 2006 to 2007 and 15 subjects were included . they were in good health as determined by medical history , a physical examination and standard blood chemistry analyses . all subjects gave written informed consent to the study , which was approved by the ethics committee of juntendo university study protocol . each subject was instructed to eat a weight maintained normalfat diet ( 25% fat , 55% carbohydrate , 20% protein ) from 3  days before measurement . then , blood samples were taken after overnight fasting . the imcl levels and t1 , t2 relaxation times were measured by hmrs and mri , respectively ( visart1.5tex v4.40 ; toshiba , tokyo , japan ) . resonance of hmrs was quantified by reference to the methylene signal intensity ( sfat ) , with peaks being observed at approximately 1.25  p.p.m . imcl was quantified by the sfat and using a creatine signal at 3.0  p.p.m . then , peripheral insulin sensitivity was evaluated by a euglycemic hyperinsulinemic clamp ( target plasma glucose level of 95  mg / dl and insulin infusion rate of 100  mu / m / min ) . all data are expressed as mean    sd . differences of magnetic resonance data between the sol and ta were compared by the wilcoxon signedrank test . spearman s rank correlation coefficient was used to evaluate the correlations of t1 and t2 with imcl of the ta and sol . all data were within the normal ranges . as reported previously , imcl of the sol was approximately threefold higher than that of the ta ( table  2 ) . in contrast , similar to the amount of imcl , t2 relaxation time of the sol was longer than that of the ta ( table  2 ) . imcl , intramyocellular lipids ; sol , soleus muscle ; ta , tibialis anterior muscle . next , we investigated the correlation of t1 and t2 with imcl of the ta and sol . in contrast , t2 correlated significantly with imcl of the sol ( r  =  0.65 , p  <  0.05 ; figure  1 ) , but not with that of the ta . the imcl of the sol significantly correlated with gir ( r  =  0.58 , p  <  0.05 ) , whereas t2 in the sol did not . the relationship between intramyocellular lipids ( imcl ) level and t2 relaxation time of the soleus ( sol ) muscle ( n  =  15 ) . imcl was quantified by the methylene signal intensity ( sfat ) with creatine signal ( cre ) as the reference , and was expressed as a ratio relative to cre ( sfat / cre ) . in the present study , we investigated the association between t1 and t2 relaxation times , determined by mri , and imcl measured by hmrs in the sol and ta muscles . we found that imcl of the sol was significantly higher than that of the ta . similarly , t2 relaxation time of the sol was longer than that of the ta . t2 relaxation time correlated significantly with imcl in the sol , but not in the ta . the result suggests the possibility that t2 relaxation time might be used to estimate imcl in the sol in a clinical setting . we observed that t2 relaxation time of the sol was significantly longer than that of the ta . this result is similar to a previous study showing that t2 relaxation time of the sol is significantly higher than that of the gastrocnemius muscle . it has been shown that longer t2 relaxation time was positively associated with the proportion of type  i muscle fiber . in addition , other studies showed a longer t2 relaxation time for type  i fibers compared with type  ii fibers in animal models and humans . the sol contains a high proportion of type  i muscle fibers , whereas the ta and gastrocnemius are muscles with a relatively large fraction of type  ii fibers . thus , it is speculated that the differences of t2 relaxation time in each muscle might be partly explained by differences of muscle fiber composition . we found the positive correlation between t2 relaxation time and imcl in the sol , but not in the ta . the reason why imcl correlated to t2 relaxation time only in the sol is not clear at present . however , at least in the sol , this finding might be also related to muscle fiber composition , because type  i fibers contain higher imcl compared with type ii fibers . because of the technical difficulties in assessing the fiber type of the sol by muscle biopsy , it is difficult to clarify the relationship between imcl , fiber type and t2 relaxation time in the present study . nevertheless , it is reasonable that the relationship between t2 relaxation time and imcl is observed only in a certain type of muscle . one limitation of the present study is that we included only nonobese healthy male subjects . thus , it is still unclear whether the findings in the present study can be applied to the general population , including female , obesity or diabetic subjects . obviously , further study is required to generalize the result of the present study . in summary , the results of the present study suggested the possibility that t2 relaxation time might be used to estimate imcl in the sol in a clinical setting .