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To evaluate the effects of cooling between exercise sessions on intramuscular water movement and muscle performance, the lower extremities of nine untrained men were assigned to either a cooling protocol (20-min water immersion, 15 °C) or a noncooling protocol. Each subject performed two exercise sessions involving maximal concentric knee extension and flexion (three repetitions, 60°/s; followed by 50 repetitions, 180°/s). The peak torque at 60°/s and total work, mean power, and decrease rate of torque value at 180°/s were evaluated. Axial magnetic resonance diffusion-weighted images of the mid-thigh were obtained before and after each exercise session. Apparent diffusion coefficient (ADC) values for the quadriceps and hamstrings were calculated for evaluating intramuscular water movement. Both groups exhibited significantly increased ADC values for the quadriceps and hamstrings after each exercise session. These ADC values returned to the pre-exercise level after water immersion. No significant difference was observed in muscle performance from first exercise session to the next in either group, except for increased total work and mean power in knee flexion in the cooled group. Cooling intervention between exercise sessions decreased exercise-induced elevation of intramuscular water movement and had some beneficial effects on muscle endurance of knee flexors, but not knee extensors., (© 2012 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Muscle hardening, including delayed onset muscle soreness, can be found after vigorous exercise. Some techniques for measuring muscle hardness have been proposed. Freehand ultrasound (US) elastography has been developed and applied to breast imaging., Purpose: To evaluate the feasibility of US elastography for investigating changes in muscle hardness after eccentric exercise of the elbow flexor muscles., Material and Methods: Six healthy male volunteers performed eccentric contractions of the elbow flexor muscles of their non-dominant arms. US elastography was performed by using 14-6 MHz linear array transducer combined with a stabilizer and a gel pack of reference agent. Color-coded elasticity images and the relative strain ratio of the biceps brachii muscle to the reference were obtained. To verify the US elastography measurements, a commercially available durometer was also employed. Both measurements were performed before, immediately after, and 1-4 days after exercise. The mean scores of strain ratios of the US elastography and durometer measurements were examined using repeated-measures ANOVA., Results: US elastography demonstrated significant muscle hardening and recovery after exercise (P<0.01). Muscle hardness increased up immediately after the exercise and continued to increase, peaking on day 2 post-exercise, and then decreased until day 4. The durometer indicated similar changes to US elastography. The control arms did not demonstrate any significant change., Conclusion: US elastography is feasible to measure muscle hardness and to produce a two-dimensional hardness map of the muscle.

Aim: To evaluate the effect of local cooling on the diffusion of water molecules and perfusion within muscle at different cooling temperatures., Materials and Methods: Magnetic resonance diffusion-weighted (DW) images of the leg (seven males) were obtained before and after 30 min cooling (0, 10, and 20°C), and after a 30 min recovery period. Two types of apparent diffusion coefficient (ADC; ADC1, reflecting both water diffusion and perfusion within muscle, and ADC2, approximating the true water diffusion coefficient) of the ankle dorsiflexors were calculated from DW images. T2-weighted images were also obtained to calculate T2 values of the ankle dorsiflexors. The skin temperature was measured before, during, and after cooling., Results: Both ADC values significantly decreased after cooling under all cooling conditions; the rate of decrease depended on the cooling temperature used (ADC1: -36% at 0°C, -27.8% at 10°C, and -22.6% at 20°C; ADC2: -26% at 0°C, -21.1% at 10°C, and -14.6% at 20°C). These significant decreases were maintained during the recovery period. Conversely, the T2 value showed no significant changes. Under all cooling conditions, skin temperature significantly decreased during cooling; the rate of decrease depended on the cooling temperature used (-74.8% at 0°C, -51.1% at 10°C, and -26.8% at 20°C). Decreased skin temperatures were not restored to pre-cooling values during the recovery period under any cooling conditions., Conclusion: Local cooling decreased the water diffusion and perfusion within muscle with decreased skin temperature; the rates of decrease depended on the cooling temperature used. These decreases were maintained for 30 min after cooling., (Copyright © 2010 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)

Purpose: we used magnetic resonance (MR) imaging and ultrasonography in combination with a dynamometer to assess physiological and functional aspects of the skeletal muscles after strenuous exercise that included eccentric contraction., Methods: seven male subjects (mean age, 21.7 years) performed ankle plantar flexion that included eccentric contraction and underwent diffusion-weighted MR imaging for calculation of the apparent diffusion coefficient (ADC) of the triceps surae muscles. We used ultrasonography combined with a dynamometer to measure the displacement of the myotendinous junction (MTJ) of the medial gastrocnemius and maximal isometric force during ankle plantar flexion. We also assessed the level of muscle soreness of the calf using a visual analogue scale. We measured these parameters before exercise and one, 2, 3, 5, and 8 days after exercise and examined significant changes from the pre-exercise value using repeated-measures analysis of variance with Dunnett's test for each measurement parameter., Results: one day after exercise, we observed increased muscle soreness (P<0.001) and decreased MTJ displacement (P<0.05); isometric force generation tended to decrease, but the change was not significant. Muscle soreness peaked 2 days after exercise (P<0.001) and remained significantly increased until 5 days after exercise (P<0.005). The medial gastrocnemius exhibited increased ADC value 3 days after exercise (P<0.005), but the lateral gastrocnemius and the soleus showed no significant changes throughout this study., Conclusion: our findings suggest that muscle damage induced by eccentric contraction manifests as muscle soreness and dysfunction early after exercise and later increases water diffusion within damaged muscle.