Use of muscle functional magnetic resonance imaging with older individuals

Muscle functional magnetic resonance imaging (mfMRI) has been widely used t o study muscle recruitment in exercise in young healthy subjects, but has n ot been validated or used with older subjects. This study validates and dem onstrates the use of mfMRI in older subjects. Subjects consisted of apparen tly healthy sedentary younger (n = 7) and older (n = 6) women. Proton trans verse relaxation (T2)-weighted MRI scans were obtained of the quadriceps fe moris at rest and immediately following three bouts of knee extension exerc ise (50%, 75%, and 100% of untrained 5 x 10 repetition maximum [RM]). Older subjects performed knee extension training for 12 weeks and repeated the M RI scan protocol using the same absolute loads. Training induced a 13% incr ease in 1 RM and a 25% increase in 5 x 10 RM. Older subjects had higher res ting T2 values compared with younger subjects; however, the T2 response to exercise (slope) was similar among groups (young = 0.063 +/- 0.003, older u ntrained = 0.055 +/- 0.011, older trained = 0.053 +/- 0.008; p > .05). In a ll cases, T2 increased Linearly with load. Trained older subjects showed a lower T2 response when lifting the same absolute load compared with before training, which is consistent with results previously obtained from young s ubjects. In the older population, mfMRI is appropriate for use and offers b enefits over other technologies.