Acute Physiological Response of Lumbar Intervertebral Discs to High-load Deadlift Exercise.

PURPOSE: We aimed to evaluate the acute physiological effects of high-load deadlift exercise on the lumbar intervertebral discs using MR diffusion-weighted imaging (DWI). METHODS: Fifteen volunteers (11 men and 4 women; 23.2 ± 3.3 years) without lumbar intervertebral disc degeneration performed deadlift exercise (70% of 1 repetition maximum, 6 repetitions, 5 sets, 90 s rest between sets) using a Smith machine. Sagittal MR diffusion-weighted images of the lumbar intervertebral discs were obtained using a 1.5-Tesla MR system with a spine coil before and immediately after the exercise. We calculated apparent diffusion coefficient (ADC; an index of water movement) of the nucleus pulposus from diffusion weighted images at all lumbar intervertebral discs (L1/2 through L5/S1). RESULTS: All lumbar intervertebral discs showed significantly decreased ADC values immediately after deadlift exercise (L1/2, -2.8%; L2/3, -2.1%; L3/4, -2.8%; L4/5, -4.9%; L5/S1, -6.2%; P < 0.01). In addition, the rate of ADC decrease of the L5/S1 disc was significantly greater than those of the L1/2 (P = 0.017), L2/3 (P < 0.01), and L3/4 (P = 0.02) discs. CONCLUSION: The movement of water molecules within the lumbar intervertebral discs is suppressed by high-load deadlift exercise, which would be attributed to mechanical stress on the lumbar intervertebral discs during deadlift exercise. In particular, the L5/S1 disc is subjected to greater mechanical stress than the other lumbar intervertebral discs.

Acute effects of varying squat depths on lumbar intervertebral disks during high-load barbell back squat exercise.

We aimed to evaluate the acute physiological effects of high-load barbell back squat exercise on each lumbar intervertebral disk with varying squat depths. Thirteen subjects (age, 23.3 ± 3.5 years) performed parallel and half-squat exercises (80% of one repetition maximum, eight repetitions, five sets) using a Smith machine. Sagittal magnetic resonance diffusion-weighted and spin-echo images of lumbar intervertebral disks were obtained by using a 1.5-Tesla MR system before and after each squat exercise; apparent diffusion coefficient (ADC; an index of water movement) and T2 relaxation time (an index of water content level) of the nucleus pulposus were calculated at all lumbar intervertebral disks. Additionally, we measured the angles of lumbar lordosis and anterior pelvic tilt at the bottom position of each squat using a three-dimensional motion-capture system. The nucleus pulposus of L4/5 (-5.0%, P < .01) and L5/S1 (-6.6%, P < .01) intervertebral disks showed decreased ADC values after parallel squat exercise. Moreover, post-exercise ADC value in parallel squat exercise was lower than that in half-squat exercise at L5/S1 intervertebral disk (P < .05). In contrast, the nucleus pulposus of all lumbar intervertebral disks had no significant T2 change before and after both squat exercises. The angles of lumbar lordosis (P < .01) and anterior pelvic tilt (P < .01) were smaller in parallel squat than in half-squat. Lower lumbar intervertebral disks are subject to greater mechanical stress during high-load parallel back squat exercise, which may result from smaller lumbar lordosis and anterior pelvic tilt angles at the bottom position during parallel squat.

Relationship between stride length and maximal ball velocity in collegiate baseball pitchers.

[Purpose] To evaluate the relationship between stride length during a pitch and maximal ball velocity and define the determinants of stride length in collegiate baseball pitchers. [Participants and Methods] Eighteen collegiate baseball pitchers participated in this study. Using a standard tape measure, the distance between each participant's legs was measured after maximal abduction of both hip joints in a standing position. The pitchers threw fastballs on an indoor pitching mound at an official pitching distance. The throwing motion was recorded with four high-speed video cameras (240 Hz), while the ball velocity was measured using a radar gun. The stride length at foot contact was calculated at the maximal ball velocity using a three-dimensional motion analysis system. [Results] The maximal ball velocity (mean 129.8 km/h) had a significant positive correlation with the absolute stride length during a pitch (r=0.55), but no correlation with the relative stride length (% body height, % lower extremity length, and % maximal open legs' width). Stride length during a pitch did not significantly correlate with the pitcher's body height, lower extremity length, and maximal open legs' width. [Conclusion] A longer stride length contributes to a higher ball velocity in collegiate baseball pitchers.

Muscle Recruitment Pattern of the Hamstring Muscles in Hip Extension and Knee Flexion Exercises.

We aimed to compare dynamic exercise performance between hip extension exercises with different knee angles and between knee flexion exercises with different hip angles, and to investigate the recruitment pattern of the hamstrings in each exercise. Seven men performed 4 isokinetic exercises (3 maximal concentric contractions at 30°/s (peak torque) and 30 maximal concentric contractions at 180°/s (total work)): hip extension with the knee fully extended (HEke) and with the knee flexed at 90° (HEkf) and knee flexion with the hip fully extended (KFhe) and with the hip flexed at 90° (KFhf). The recruitment pattern of the hamstrings was evaluated in each exercise using magnetic resonance imaging (T2 calculation). The HEke condition showed significantly greater peak torque than the HEkf condition (p < 0.05). The KFhf condition had significantly greater peak torque and total work values than the KFhe condition (p < 0.05). Although the biceps femoris long head, semitendinosus, and semimembranosus had significantly increased post-exercise T2 values in the HEke (p < 0.05), KFhe, and KFhf conditions (p < 0.01), the T2 increase values were significantly greater under the KFhf than the HEke condition (p < 0.05). The semitendinosus showed a significantly greater T2 increase value than other muscles under both KFhe and KFhf conditions (p < 0.05). Performance of hip extension and knee flexion exercises increases when the hamstring muscles are in a lengthened condition. The hamstring muscles (particularly the semitendinosus) are more involved in knee flexion than in hip extension.

Functional Hip Characteristics and Their Relationship With Ball Velocity in College Baseball Pitchers.

CONTEXT: Compared to shoulder and elbow functions, the hip functional characteristics of baseball pitchers have not been fully investigated. Therefore, little is known about the relationship between hip function and pitching performance. OBJECTIVE: The purpose of this study was to evaluate the characteristics of hip flexibility and strength, focusing on their influences on the ball velocity in baseball pitchers. DESIGN: Descriptive laboratory study. SETTING: Laboratory and university baseball facility. PARTICIPANTS: Twenty-three college baseball pitchers. INTERVENTIONS: Passive hip range of motion (ROM) and isometric hip muscle strength were bilaterally measured. The pitchers threw 20 fastballs at an official pitching distance. MAIN OUTCOME MEASURES: Bilateral hip ROM and strength in flexion, extension, abduction, adduction, and external and internal rotation; the maximal ball velocity. RESULTS: The pivot side showed smaller hip external rotation ROM (P < .01), larger hip internal rotation ROM (P = .03), and greater hip adduction strength (P = .03) than the stride side. The hip extension ROM on the stride side had a negative correlation with the maximal ball velocity (r = -.58, P < .01). The maximal ball velocity (135.3 [4.1] km/h) positively correlated with the hip extension (r = .59, P < .01), flexion (r = .57, P < .01), abduction (r = .55, P < .01), and adduction (r = .55, P < .01) strength on the pivot leg, and the hip flexion (r = .53, P = .01), abduction (r = .67, P < .01), and adduction (r = .46, P = .03) strength on the stride leg. CONCLUSIONS: These findings suggest that baseball pitchers do not have marked side-to-side differences in hip flexibility and strength, and that an important fitness factor for increasing ball velocity is not the hip flexibility but the hip muscle strength of both legs.

Changes in lower extremity function and pitching performance with increasing numbers of pitches in baseball pitchers.

Compared to upper extremity function, the changes in lower extremity function with increasing numbers of pitches have not fully been investigated in baseball pitchers. In addition, little is known about the correlation between lower extremity function and pitching performance. The purpose of this study was to evaluate the effect of fatigue on lower extremity function and pitching performance in a simulated baseball game. Eighteen collegiate baseball pitchers threw 117 pitches in 9 innings (13 pitches per inning) with 5-min rest between innings at an official pitching distance in a simulated game. Isometric hip muscle strength (abduction and adduction) and squat jump performance (height, mean/peak power, and mean/peak velocity) were measured before and after the game. The mean ball velocity and pitching accuracy were assessed per inning. Ball velocity significantly decreased in the 7th (P=0.026) and 9th (P=0.001) innings compared to the 1st inning, but pitching accuracy did not change significantly. Hip abduction (P=0.009) and adduction (P=0.001) strength significantly decreased after the game, but squat jump performance did not significantly change before and after the game. A significant correlation between decreased ball velocity in the 9th inning and decreased hip adduction strength was found (P=0.011, r=0.583). Our findings suggest that hip abduction and adduction strength are susceptible to fatigue owing to repetitive throwing motions and that hip adduction strength, especially, is an important physical fitness factor for maintaining ball velocity during a game in baseball pitchers.

Side-to-side difference in dynamic unilateral balance ability and pitching performance in Japanese collegiate baseball pitchers.

[Purpose] To evaluate the side-to-side difference in dynamic unilateral balance ability and to determine the correlation of the balance ability with pitching performance in collegiate baseball pitchers. [Subjects and Methods] Twenty-five Japanese collegiate baseball pitchers participated in this study. Dynamic balance ability during a unilateral stance was bilaterally evaluated using the star excursion balance test (SEBT). The pitchers threw 20 fastballs at an official pitching distance; the maximal ball velocity and pitching accuracy (the number of strike/20 pitches × 100) were assessed. Side-to-side difference in scores of SEBT was assessed using a paired t-test. Correlations between SEBT scores and pitching performance were evaluated for both legs using a Pearson's correlation analysis. [Results] The pivot side showed significantly higher score of the SEBT in the anteromedial direction than the stride side. On the other hand, the SEBT scores in the pivot and stride legs did not have significant correlations with maximal ball velocity and pitching accuracy. [Conclusion] These findings suggest that marked side-to-side difference does not exist in the dynamic unilateral balance ability of collegiate baseball pitchers and that the dynamic unilateral balance ability of each leg is not directly related to maximal ball velocity and pitching accuracy.

Effects of low-load resistance exercise with blood flow restriction on intramuscular hemodynamics, oxygenation level and water content.

BACKGROUND: Muscle metabolism during and after low-load blood flow restriction (BFR) exercise should be further investigated to clarify the mechanism by which the exercise leads to muscle hypertrophy, and increases strength and endurance. We aimed to investigate the effects of low-load resistance exercise with BFR on intramuscular hemodynamics, oxygenation level, and water content. METHODS: Seven men performed ankle plantar flexion exercise (120 repetitions, 30% one repetition maximum) using a custom-made device with and without BFR inside a magnetic resonance scanner. Changes in the total hemoglobin/myoglobin concentration and Tissue Oxygenation Index (TOI) within the medial gastrocnemius were evaluated before, during, and after exercise using near-infrared spectroscopy. Intramuscular water content was evaluated before and after exercise by calculating an apparent diffusion coefficient (ADC) using magnetic resonance diffusion-weighted imaging. RESULTS: The TOI significantly decreased during BFR and non-restricted exercises, and significantly increased after BFR exercise; compared to the non-restricted condition, the BFR condition showed significantly greater changes in the TOI during and after exercise. The total hemoglobin/myoglobin concentration significantly increased during and after exercise in both exercise conditions; the BFR condition temporarily showed significantly greater values during and after exercise. Although the ADC values significantly elevated after BFR and non-restricted exercises, the elevation was significantly greater in the BFR condition. CONCLUSIONS: Compared to non-restricted exercise, low-load BFR exercise exposes an exercising muscle to greater hypoxic and hyperemic environments. Moreover, BFR exercise not only elevates muscle oxygenation level, but also results in greater muscle swelling and reactive hyperemia than those observed after non-restricted exercise.

Effects of low-load resistance exercise with blood flow restriction on high-energy phosphate metabolism and oxygenation level in skeletal muscle.

We aimed to evaluate the effects of low-load resistance exercise with blood flow restriction (BFR) on high-energy phosphate metabolism, intracellular pH, and oxygenation level in the skeletal muscle. Seven males performed low-load ankle plantar flexion exercise (120 repetitions, 30% of one-repetition maximum) with and without BFR (130% of systolic blood pressure) inside a magnetic resonance device. Inorganic phosphate (Pi)-to-phosphocreatine (PCr) ratio, intracellular pH, and tissue oxygenation index (TOI) in the medial gastrocnemius were determined using 31P-magnetic resonance spectroscopy and near-infrared spectroscopy before and during exercise. The Pi-to-PCr ratio significantly increased during exercise in both conditions, with the BFR-condition values significantly exceeding the control-condition values. The BFR and control conditions showed significantly decreased intracellular pH during exercise, with the BFR-condition values being significantly lower than the control-condition values. The TOI significantly decreased during both exercises, but the decreases in the BFR condition were significantly greater than those observed in the control condition. Low-load BFR exercise places greater metabolic stress (greater PCr depletion, lower intracellular pH, and lower oxygenation level) on an exercising muscle than low-load non-restricted exercise.

Intramuscular water movement during and after isometric muscle contraction: evaluation at different exercise intensities.

We aimed at evaluating the effect of isometric muscle contraction on intramuscular water movement at different exercise intensities. Seven men performed 1-min isometric ankle dorsiflexion (20% and 50% maximal voluntary contractions [MVCs]) with a non-magnetic custom-made dynamometer, inside a magnetic resonance (MR) device. Axial diffusion-weighted images were obtained before, during and at 1-20 min (1-min interval) after the exercise to calculate the apparent diffusion coefficient (ADC) of the tibialis anterior. Under the same exercise condition, the concentration change of total haemoglobin (Hb) and myoglobin (Mb) (total Hb/Mb) within the tibialis anterior was assessed by performing near-infrared spectroscopy before, during and after the exercise outside the MR device. The 20% MVC exercise significantly increased the ADC only at 1 min postexercise (P<0·01), whereas the ADC significantly increased during and at 2-20 min after the 50% MVC exercise (P<0·01). The 20% MVC exercise decreased the total Hb/Mb during exercise (P<0·01), but the value significantly increased at 1 min postexercise (P<0·01). The total Hb/Mb significantly decreased during the 50% MVC exercise, but significantly increased at 1-5 min postexercise (P<0·01). One-minute moderate-intensity isometric exercise activates intramuscular water movement during and after the exercise. This activation was found even after a low-intensity exercise, but the effect was small and did not last long. The effect of intramuscular hyperaemia on the postexercise ADC elevation may be limited to the very early period after low- to moderate-intensity exercises.

Effect of exercise-induced muscle damage on muscle hardness evaluated by ultrasound real-time tissue elastography.

PURPOSE: To assess the effect of exercise-induced muscle damage on muscle hardness and evaluate the relationship between muscle hardness and muscle damage indicators. METHODS: Seven men (mean 25.3 years; 172.7 cm; 66.8 kg) performed the single-leg ankle plantar flexion exercise involving both concentric and eccentric contractions (10 sets of 40 repetitions). The hardness of the medial gastrocnemius (MG) was evaluated using ultrasound real-time tissue elastography before, from day 1 to 4, and day 7 after exercise. The strain ratio between the MG and a reference material was calculated. Simultaneously, we evaluated the magnetic resonance T2 value (an index of edema) of the triceps surae, the ankle dorsiflexion range of motion (ROM), and calf muscle soreness. Serum creatine kinase activity was assessed before, 2 and 4 h, and from day 1 to 4 after exercise. RESULTS: The MG showed lower strain ratio, indicating increased muscle hardness, on day 4 post-exercise (P < 0.01) and higher T2 values on days 1-7 post-exercise (P < 0.01) relative to each pre-exercise value. The ankle dorsiflexion ROM was lower on days 2-4 post-exercise (P < 0.01). The serum creatine kinase markedly increased on days 3 and 4 post-exercise (not significant). The degree of muscle soreness among the post-exercise time points was similar. The decreased strain ratio did not correlate with the increased T2, the decreased joint ROM or muscle soreness. CONCLUSION: Muscle hardness increased after strenuous resistance exercise, but the change was not related with muscle edema, decreased joint ROM, or muscle soreness resulting from muscle damage.

Noninvasive Evaluation of Trunk Muscle Recruitment after Trunk Exercises using Diffusion-weighted MR Imaging.

PURPOSE: We evaluated trunk muscle recruitment in abdominal and back exercises with magnetic resonance (MR) diffusion-weighted imaging. METHODS: Twelve men performed bent-knee sit-up, crunch, trunk lateral flexion, and trunk extension exercises. We obtained axial diffusion-weighted images of the trunk before and after each exercise using a 1.5-tesla MR system, calculated apparent diffusion coefficient (ADC) values from the right and left rectus abdominis, lateral abdominal, psoas major, quadratus lumborum, and intrinsic back muscles to evaluate the activity of these muscles during each exercise, and compared ADC values before and after exercise using a paired t-test. RESULTS: The ADCs of the rectus abdominis (right, +19.1%; left, +11.7%), lateral abdominal (right, +15.5%; left, +14.1%), and psoas major (right, +14.8%; left, +15.9%) muscles on both sides increased after the bent-knee sit-up (P < 0.01). The ADCs of the rectus abdominis (right, +16.8%; left, +10.2%) and lateral abdominal (right, +8.4%; left, +7.0%) muscles on both sides increased after the crunch exercise (P < 0.01). Trunk lateral flexion resulted in increased ADC on only the right side of all of the muscles (rectus abdominis, +12.3%; lateral abdominal muscles, +20.3%; quadratus lumborum, +17.1%; intrinsic back muscles, +12.0%; psoas major, +15.4%) (P < 0.01). The ADCs of the lateral abdominal (right, +5.2%; left, +5.6%), quadratus lumborum (right, +6.0%; left, +3.0%), and intrinsic back (right, +13.2%; left, +14.6%) muscles on both sides were elevated after trunk extension (right lateral abdominal muscles and left quadratus lumborum, P < 0.05; other muscles, P < 0.01). CONCLUSION: Diffusion-weighted imaging reveals the recruitment patterns of superficial and deep trunk muscles in abdominal and back exercises through exercise-induced activation in intramuscular water movement.

Comparison of the morphology of the rotator cuff muscles across age groups.

We aimed at investigating the morphological difference of the rotator cuff (RC) muscles among age groups from elementary school students to college students. The subjects included 10 college (22.6 ± 1.8 years), 10 high school (16.8 ± 0.6 years), 10 junior high school (13.9 ± 0.6 years), and 10 elementary school (10.4 ± 0.5 years) students. Consecutive oblique sagittal magnetic resonance T1 -weighted images of the dominant shoulder were acquired for each participant. Muscle length, maximal anatomical cross-sectional area (ACSA), the position of the maximal ACSA at full muscle length, muscle volume, and the individual-to-total RC muscle volume ratio for the supraspinatus, external rotators (infraspinatus and teres minor), and subscapularis were evaluated. The muscle length, maximal ACSA, and muscle volume in the RC muscles significantly increased with increasing age (P < 0.01), but there was no significant difference between college and high school students except in regard to the volume of the external rotators. There was no difference in the position of the maximal ACSA or the individual-to-total RC muscle volume ratio among the groups. The findings of this study show that the size of each RC muscle increases with increasing age, but the position of maximal ACSA and the proportion of each muscle to the total RC muscle volume are similar among age groups from elementary school students to college students.

Alterations in intramuscular water movement associated with mechanical changes in human skeletal muscle fibers: an evaluation using magnetic resonance diffusion-weighted imaging and B-mode ultrasonography.

BACKGROUND: Intramuscular water movement is expected to be affected by the mechanical changes of the muscle fibers. However, the effect of changes in fiber length (FL) and pennation angle (PA) on the water movement has not been sufficiently investigated in human skeletal muscles. PURPOSE: To determine the relationship between intramuscular water movement and the mechanical changes in human muscle fibers. MATERIAL AND METHODS: Axial magnetic resonance diffusion-weighted images of the right leg (eight men) were taken using a 1.5-Tesla device with the ankle joint maximally dorsiflexed and maximally plantar flexed. The apparent diffusion coefficient (ADC) values of both the dorsiflexors (the superficial and deep parts of the tibialis anterior) and the plantar flexors (medial gastrocnemius and soleus) were calculated along three orthogonal axes (S-I: superior-to-inferior, A-P: anterior-to-posterior, and R-L: right-to-left). FL and PA of both muscle groups were also calculated from longitudinal B-mode ultrasound images with the ankle joint maximally dorsiflexed and plantar flexed. RESULTS: There was a significant increase in the ADC in superficial (P < 0.05) and deep (P < 0.05) parts of the dorsiflexors in the S-I direction when the ankle was plantar flexed and in the A-P and R-L directions when the ankle was dorsiflexed (P < 0.05). The plantar flexors showed significantly elevated ADC in the S-I direction when the ankle was dorsiflexed (P < 0.05), and in the A-P and R-L directions when the ankle was plantar flexed (P < 0.05). The dorsiflexors also showed significantly increased PA and decreased FL values when the ankle was dorsiflexed (P < 0.05). The plantar flexors displayed similar morphological changes when the ankle was plantar flexed (P < 0.05). CONCLUSION: Water diffusion is affected by structural changes in the long axis of the muscle fibers, namely the changes in PA and FL.

Strenuous resistance exercise effects on magnetic resonance diffusion parameters and muscle-tendon function in human skeletal muscle.

PURPOSE: To assess the effects of strenuous exercise on magnetic resonance diffusion parameters and muscle-tendon complex function in skeletal muscle. MATERIALS AND METHODS: Six men performed ankle plantar flexion exercises with eccentric contraction. The fractional anisotropy (FA), λ(1) , λ(2) , λ(3) , mean diffusivity (MD), and T(2) values in the triceps surae muscles were measured by magnetic resonance diffusion tensor and spin-echo imaging. Passive torque of plantar flexors, maximal voluntary isometric plantar flexion torques (MVIP), and Achilles tendon stiffness during MVIP were measured by combined ultrasonography and dynamometry. Plasma creatine kinase and muscle soreness were also assessed. These parameters were measured before and 1-8 days postexercise. RESULTS: The medial gastrocnemius exhibited significantly decreased FA 2-5 days after, increased λ(2) 3 days after, and increased λ(3) 2 and 3 days after exercise. This muscle also showed significantly increased MD and T(2) values 3 days postexercise. MVIP significantly decreased 2 and 3 days postexercise, while passive torque significantly increased 2 days postexercise. Creatine kinase and muscle soreness increased 3-5 days and 1-5 days postexercise, respectively. CONCLUSION: Exercise-induced muscle damage manifested as significant changes in muscle diffusion parameters with muscle-tendon complex dysfunction and delayed-onset muscle soreness.

Muscle hardness measurement by using ultrasound elastography: a feasibility study.

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.

Effects of strenuous exercise with eccentric muscle contraction: physiological and functional aspects of human skeletal muscle.

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.

Effects of different cooling treatments on water diffusion, microcirculation, and water content within exercised muscles: evaluation by magnetic resonance T2-weighted and diffusion-weighted imaging.

In this study, we determined the effects of different cooling treatments on exercised muscles. Seven adults underwent four post-exercise treatments (20-min ice-bag application, 60-min gel-pack application at 10 degrees C and 17 degrees C, and non-cooling treatment) with at least 1 week between treatments. Magnetic resonance diffusion- and T2-weighted images were obtained to calculate the apparent diffusion coefficients (apparent diffusion coefficient 1, which reflects intramuscular water diffusion and microcirculation, and apparent diffusion coefficient 2, which is approximately equal to the true diffusion coefficient that excludes as much of the effect of intramuscular microcirculation as possible) and the T2 values (intramuscular water content level) of the ankle dorsiflexors, respectively, before and after ankle dorsiflexion exercise and after post-exercise treatment. The T2 values increased significantly after exercise and returned to pre-exercise values after each treatment; no significant differences were observed among the four post-exercise treatments. Both apparent diffusion coefficients also increased significantly after exercise and decreased significantly after the three cooling treatments; no significant difference was detected among the three cooling treatments. Local cooling suppresses both water diffusion and microcirculation within exercised muscles. Moreover, although the treatment time was longer, adequate cooling effects could be achieved using the gel-pack applications at relatively mild cooling temperatures.

Appropriate slice location to assess maximal cross-sectional area of individual rotator cuff muscles in normal adults and athletes.

PURPOSE: We investigated appropriate slice locations for magnetic resonance (MR) imaging evaluation of the maximal cross-sectional area (CSA) of individual rotator cuff (RC) muscles in normal adults and athletes. METHODS: We used a 1.5-tesla MR system with body-array and spine coils to obtain oblique sagittal T(1)-weighted shoulder images of 29 normal adults (16 men, 13 women); 6 national-level competitive swimmers (4 men, 2 women); 10 collegiate-level female badminton players; and 7 collegiate-level male rowers. We calculated the supraspinatus, infraspinatus, teres minor, and subscapularis CSAs at the 0-1 locations on the scapula (dividing scapula width into 11 locations), 0 representing the medial border of the scapula and 1, the glenoid fossa surface. We evaluated the differences in CSAs at relative locations on the scapula for each muscle in normal adults, swimmers, badminton players, and rowers using a one-way analysis of variance followed by the Tukey test (P<0.05). RESULTS: The supraspinatus CSAs were maximal at 0.7 for all groups. The infraspinatus CSAs were maximal at 0.5 for normal men and women and badminton players, 0.4- and 0.5 locations for swimmers, and 0.4 for rowers. The teres minor CSAs were maximal at 0.9 for all groups except the swimmers (1 location). The subscapularis CSAs were maximal at 0.7 in men, swimmers, and badminton players and 0.6 in women and rowers. CONCLUSION: The appropriate slice locations for evaluating maximal CSAs are slightly lateral to the center of the scapula for the supraspinatus and subscapularis, at approximately the center of the scapula for the infraspinatus, and near the glenoid fossa for the teres minor. These slice locations should be clinically useful for morphological and/or function-related assessments of shoulder RC muscles.