US elastography is feasible to measure muscle hardness and to produce a two-dimensional hardness map of the muscle.

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We examined the effect of differences in exercise intensity on the time constant (tc) of phosphocreatine (PCr) resynthesis after exercise and the relationships between tc and maximal oxygen uptake (VO2max) in endurance-trained runners (n = 5) and untrained controls (n = 7) (average VO2max = 66.2 and 52.0 ml.min-1.kg-1, respectively). To measure the metabolism of the quadriceps muscle using phosphorus nuclear magnetic resonance spectroscopy, we developed a device which allowed knee extension exercise inside a magnet. All the subjects performed four types of exercise: light, moderate, severe and exhausting. The end-exercise PCr: [PCr+inorganic phosphate (P(i))] ratio decreased significantly with the increase in the exercise intensity (P < 0.01). Although there was little difference in the end-exercise pH, adenosine diphosphate concentration ([ADP]) and the lowest intracellular pH during recovery between light and moderate exercise, significant changes were found at the two higher intensities (P < 0.01). These changes for runners were smaller than those for the controls (P < 0.05). The tc remained constant after light and moderate exercise and then lengthened in proportion to the increase in intensity (P < 0.05). The runners had a lower tc at the same PCr and pH than the controls, particularly at the higher intensity (P < 0.05). There was a significant correlation between tc and [ADP] in light exercise and between tc and both end-exercise PCr and pH in severe and exhausting exercise (P < 0.05). The threshold of changes in pH and tc was a PCr: (PCr+P(i)) ratio of 0.5. There was a significant negative correlation between the VO2max and tc after all levels of exercise (P < 0.05). However, in the controls a significant correlation was found in only light and moderate exercise (P < 0.05). These findings suggest the validity of the use of tc at an end-exercise PCr: (PCr+P(i)) ratio of more than 0.5 as a stable index of muscle oxidative capacity and the correlation between local and general aerobic capacity. Moreover, endurance-trained runners are characterized by the faster PCr resynthesis at the same PCr and intracellular pH.

The findings of this study suggest that cooling causes an increase in intracellular pH and prevents the delayed muscle edema.

The purpose of this study was to investigate the separate effects of cooling during the acute (within 60 min post-exercise) or subacute (24-168 h post-exercise) phase on skeletal muscle after exercise. Twenty-eight male subjects [mean (SD) 23.8 (1.8) years] were randomly assigned to the control (COTG, n=10), cold-water immersion (CWIG, n=9), and double-cold-water immersion groups (DCWIG, n=9). The cold-water immersion (15 min) was administered to the subjects' legs after calf-raise exercise (CWIG: after recording initial post-exercise measures, DCWIG: after recording initial and 24 h post-exercise measures). Magnetic resonance T2-weighted images were obtained to calculate the T2 relaxation time (T2) of the triceps surae muscle before, immediately after, and at the following times post-exercise: 20, 40, and 60 min, and 24, 48, 96 and 168 h. In addition, the ankle joint range of motion, serum creatine kinase and lactate dehydrogenase, and muscle soreness level were investigated before and after exercise. In all groups, significant T2 elevations in the gastrocnemius muscle appeared from immediately after to 60 min after exercise (P<0.05). Thereafter, COTG showed significantly re-elevated T2 levels in the gastrocnemius at 96-168 h post-exercise (P<0.05), while CWIG and DCWIG showed significantly smaller T2 values than the COTG at 96 h post-exercise (P<0.05). In addition, COTG showed larger increases in serum enzymes at 96 h post-exercise (not significant) and significantly greater muscle soreness levels at 48 h post-exercise (P<0.05) than the cooling groups. The results of this study may suggest that cooling has no dramatic effect, but some minor effects on reducing exercise-induced muscle edema in the subacute phase and relieving the extent of the damaged muscle cells.

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No abstract

This study evaluated intramuscular movement of hamstrings muscle after reconstruction of the ACL with a hamstrings tendon graft. The movement of the muscles during knee flexion was measured using a novel MRI technique called the "tagging snapshot" technique, which labels multiple tagging bands within the musculature. Eleven patients who underwent ACL reconstruction using autogenous semitendinosus and gracilis tendons were studied. The difference in the maximum active knee flexion angle between the ACL-reconstructed and the intact knee was calculated as knee flexion lag. Knee flexion strength was measured in 8 of the 11 patients. The semitendinosus muscle of the ACL-reconstructed knee exhibited three different morphological patterns; group I, similar shape to the intact knee with distal tendonlike structures; group II, smaller proximally than the intact knee with distal tendonlike structures; and group III, considerably smaller proximally than the intact knee without distal tendonlike structures. Each group was associated with a different knee flexion lag and different knee flexion strength. Our results indicated that the effect of hamstrings tendon harvest on knee function is not uniform.