Resistance training reduces susceptibility to eccentric exercise-induced muscle dysfunction in older women.

This study evaluated the effect of age on susceptibility to muscular weakness and damage caused by eccentric (ECC) exercise and determined whether this susceptibility was altered by resistance training. Young and older women performed concentric (CON) and ECC one repetition maximum (1 RM) strength tests of the quadriceps femoris. Older women also performed knee extension training for 12 weeks. An unaccustomed bout of ECC knee extension exercise was performed before and after training, and CON and ECC 1 RM were reassessed for 11 days after the ECC bout. Magnetic resonance imaging was used to evaluate changes in muscle water content associated with muscle damage. Before training, older subjects showed a larger decline in CON (p =.008) and ECC (p =.03) strength induced by the unaccustomed ECC bout, compared with the young subjects. One day following the ECC bout, the older women showed a 24% reduction in CON and a 27% reduction in ECC 1 RM, compared with only 6% (CON) and 10% (ECC) in the younger women. A magnetic resonance imaging evaluation indicated that edema or damage was significantly greater in the older untrained women than it was in young women (p <.05), but the resistance-trained older women showed no greater muscle injury than the young women (p >.05). Resistance-trained older women showed no greater decline than sedentary young women in either CON (p >.05) or ECC (p >.05) strength. In conclusion, sedentary older women are more susceptible to ECC-induced muscle dysfunction, but resistance training reduces this susceptibility.

Use of muscle functional magnetic resonance imaging with older individuals.

Muscle functional magnetic resonance imaging (mfMRI) has been widely used to study muscle recruitment in exercise in young healthy subjects, but has not been validated or used with older subjects. This study validates and demonstrates the use of mfMRI in older subjects. Subjects consisted of apparently healthy sedentary younger (n = 7) and older (n = 6) women. Proton transverse relaxation (T2)-weighted MRI scans were obtained of the quadriceps femoris at rest and immediately following three bouts of knee extension exercise (50%, 75%, and 100% of untrained 5 x 10 repetition maximum [RM]). Older subjects performed knee extension training for 12 weeks and repeated the MRI scan protocol using the same absolute loads. Training induced a 13% increase in 1 RM and a 25% increase in 5 x 10 RM. Older subjects had higher resting T2 values compared with younger subjects; however, the T2 response to exercise (slope) was similar among groups (young = 0.063+/-0.003, older untrained = 0.055+/-0.011, older trained = 0.053+/-0.008; p > .05). In all 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 subjects. In the older population, mfMRI is appropriate for use and offers benefits over other technologies.

Computed tomography of calcaneal fractures: anatomy, pathology, dosimetry, and clinical relevance.

Eighteen CT examinations were performed in 10 patients for the evaluation of acute intraarticular fractures and their follow-up. Fractures comparable to those in the patients were created in cadavers. The normal anatomy and the traumatically altered anatomy of the calcaneus in the axial, coronal, and sagittal planes are demonstrated by CT and corresponding anatomic sections. Scanning was performed in the axial plane, with subsequent reconstruction in the coronal and sagittal planes. The axial scans show disruption of the inferior part of the posterior facet, calcaneocuboid joint involvement, and widening of the calcaneus. The coronal scans show disruption of the superior part of the posterior facet, sustentaculum tali depression (involvement of middle and anterior facets), peroneal and flexor hallucis longus tendon impingement, and widening and height loss of the calcaneus. The sagittal scans show disruption of the posterior facet, calcaneocuboid joint involvement, and height loss of the calcaneus and allow the evaluation of Boehler's and Gissane's angles. All three planes show the position of major fracture fragments. Radiation dose to the foot was measured to be 0.1 rad (0.001 Gy) for plain film radiography (five exposures), 18 rad (0.18 Gy) for conventional tomography (20 cuts), and 2.6 rad (0.026 Gy) for axial CT examination.