Osamu Yanagisawa

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.

Evaluation of human muscle hardness after dynamic exercise with ultrasound real-time tissue elastography: a feasibility study.

AIM To assess the feasibility of ultrasound real-time tissue elastography (RTE) for measuring exercise-induced changes in muscle hardness and to compare the findings of RTE with those of a tissue hardness meter for semi-quantitative assessment of the hardness of exercised muscles. MATERIALS AND METHODS Nine male participants performed an arm-curl exercise. RTE measurements were performed by manually applying repetitive compression with the transducer on the scan position before exercise, immediately after exercise, and at 30 min after exercise; strain ratios between muscle and a reference material (hydrogel) were calculated (muscle strain/material strain). A tissue hardness meter was also used to evaluate muscle hardness. The intraclass correlation coefficients (ICCs) for the three repeated measurements at each measurement time were calculated to evaluate the intra-observer reproducibility of each technique. RESULTS Immediately after exercise, the strain ratio and the value obtained using the tissue hardness meter significantly decreased (from 1.65 to 1.35) and increased (from 51.8 to 54.3), respectively. Both parameters returned to their pre-exercise value 30 min after exercise. The ICCs of the RTE (and the ICCs of the muscle hardness meter) were 0.971 (0.816) before exercise, 0.939 (0.776) immediately after exercise, and 0.959 (0.882) at 30 min after exercise. CONCLUSION Similar to the muscle hardness meter, RTE revealed the exercise-induced changes of muscle hardness semi-quantitatively. The intra-observer reproducibility of RTE was very high at each measurement time. These findings suggest that RTE is a clinically useful technique for assessing hardness of specific exercised muscles.

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

To assess the effects of strenuous exercise on magnetic resonance diffusion parameters and muscle–tendon complex function in skeletal 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

Abstract 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°C and 17°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.

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. Clin. Anat. 27:365–369, 2014.

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.

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.

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.

Functional Differences Among Hamstring Muscles in Hip Extension and Knee Flexion Exercises

The hamstring muscles consist of the long (BF-L) and short (BF-S) heads of the biceps femoris, semitendinosus (ST), and semimembranosus (SM). The BF-L, ST, and SM act on both hip extension and knee flexion as biarticular muscle, whereas the BF-S flexes the knee as a uniarticular muscle. The hamstrings are occasionally treated as a muscle group (hip extensors or knee flexors), but previous studies have reported morphological and functional differences among the hamstrings. The hamstrings show individual characteristics in architectural parameters (e.g. fiber length, pennation angle, and physiological cross-sectional area). These architectural differences are likely closely associated with differences in the force-generation capacity of each hamstring muscle. In addition, each muscle’s function is affected by the angle of the hip and/or knee joints. The morphology and function of one hamstring muscle cannot be considered representative of the whole muscle group and vice versa. Thus, treating the hamstrings as a single muscle unit by assuming a uniform inter-muscular architecture can result in an inaccurate account of hamstring muscle function.