Biceps brachii muscle hardness assessed by a push-in meter in comparison to ultrasound strain elastography

© 2020, The Author(s). This study investigated the relationship between push-in meter (PM) and ultrasound strain elastography (USE) for biceps brachii (BB) muscle hardness. BB hardness of 21 young men was assessed by PM and USE during rest and isometric contractions of six different intensities (15, 30, 45, 60, 75, 90% of maximal voluntary contraction: MVC) at 30°, 60° and 90° elbow flexion. Muscle hardness (E) was calculated from the force–displacement relationship in PM, and strain ratio (SR) between an acoustic coupler (elastic modulus: 22.6 kPa) and different regions of interest (ROIs) in BB was calculated and converted to Young’s modulus (YM) in USE. In resting muscle, E was 26.1 ± 6.4 kPa, and SR and YM for the whole BB was 0.88 ± 0.4 and 30.8 ± 12.8 kPa, respectively. A significant (p \u3c 0.01) correlation was evident between E and logarithmical transformed SR (LTSR) for the ROI of whole BB (r = − 0.626), and E and converted YM (r = 0.615). E increased approximately ninefold from resting to 90% MVC, and E and LTSR (r = − 0.732 to − 0.880), and E and converted YM for the SR above 0.1 were correlated (r = 0.599–0.768, p \u3c 0.01). These results suggest that muscle hardness values obtained by PM and USE are comparable

Changes in biceps brachii muscle hardness assessed by a push-in meter and strain elastography after eccentric versus concentric contractions

Changes in biceps brachii muscle hardness assessed by a push-in meter (PM) and strain elastography (SE) were compared between eccentric (ECC) and concentric contractions (CON) of the elbow flexors to test the hypothesis that muscle hardness would increase greater after ECC. Ten men performed 5 sets of 10 ECC with their non-dominant arms and 5 sets of 10 CON with their dominant arms using a dumbbell corresponding to 50% of maximum voluntary isometric contraction (MVIC) force at 90º elbow flexion. Before and 1–4 days after the exercise, MVIC force, elbow joint angles, upper-arm circumference, and muscle soreness as muscle damage makers, and biceps brachii muscle hardness at maximally extended elbow joint by PM and SE were measured. Changes in these measures over time were compared between ECC and CON. All muscle damage markers showed greater changes after ECC than CON (p \u3c 0.001). Muscle hardness assessed by PM and SE increased (p \u3c 0.05) and peaked at 4 days post-ECC with 154.4 ± 90.0% (PM) and 156.2 ± 64.2% (SE) increases from the baseline, but did not change significantly after CON. The changes in muscle hardness post-ECC were correlated between PM and SE (r = 0.752, p \u3c 0.001). A correlation (p \u3c 0.001) between the normalized changes in resting elbow joint angle and changes in muscle hardness assessed by PM (r = − 0.772) or SE (r = − 0.745) was also found. These results supported the hypothesis and suggest that the increases in muscle hardness after ECC were associated with muscle damage (increased muscle stiffness), and PM and SE detected muscle hardness changes similarly

モクヒョウ ノ アル シュンカンテキナ チカラ ハッキ ノ シュウシュクジカン ト キンホウデンジカン ニ ツイテ

1) Subjects were healthy 16 adult men in this experiment. The relationship between amplitude and contraction time, and the relationship between force amplitude and EMG dwell time during ballistic force exertion by thumb adduction ware examined. The target force levels were defined at three levels, which were 10%, 30% and 50% of MVC. 2) Mean values of MVC derived from all subjects before taining weren\u27t larger than those after training. 3)The contraction time and EMG dwell time increased with force increment. These two relationships, force-contiraction time and force-EMG dwell time expressed as linear equations (regression equatio). Contraction time and EMG dwell time decreased remarkably after training under conditions of 30% and 50% of MVC. Therefore, Slopes of linear equations decreased, but y-intercepts remained the same 4) It is suggested that at a given ballistic force amplitude, the duration of neuronal output can be shortened by training. However, a certain essential unit time might be necessary to neuronal progrms of ballistic contraction, because the y-intercept of the regression equation did not changeafter training

レンゾク シタ サユウ ノ シュンカンテキ ナ チカラ ハッキ ノ トクセイ

1. 8 healthy adult subjects were asked to make two (right hand and left hand) separate force exertions as rapidly as possible one after the other and then simultaneous force exertion. 2. The following values of correlation coefficient during sequential force exertions and simultaneou force exertions were investigated. 1) peak force (right)-peak force (left) 2) time to peak force (right)-time to peak force (left) 3) EMG dwell time (right)-EMG dwell time (left) 3. The values of correlation coefficient with respect to peak forces, time to peak forces and EMG dwell time during simultaneous force exertions were higher than those of sequential force exertions. 4. We conjectured that motor programme when right hand and left hand forces were exerted simultaneously differ from those of sequential force exertions