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The present study aimed to clarify the effect of the foot strike pattern on muscle–tendon behavior and kinetics of the gastrocnemius medialis during treadmill running. Seven male participants ran with 2 different foot strike patterns (forefoot strike [FFS] and rearfoot strike [RFS]), with a step frequency of 2.50 Hz and at a speed of 2.38 m/s for 45 seconds on a treadmill with an instrumented force platform. The fascicle behavior of gastrocnemius medialis was captured using a B-mode ultrasound system with a sampling rate of 75 Hz, and the mechanical work done and power exerted by the fascicle and tendon were calculated. At the initial contact, the fascicle length was significantly shorter in the FFS than in the RFS (P = .001). However, the fascicular velocity did not differ between strike patterns. Higher tendon stretch and recoil were observed in the FFS (P P = .017, respectively) compared with the RFS. The fascicle in the positive phase performed the same mechanical work in both the FFS and RFS; however, the fascicle in the negative phase performed significantly greater work in the FFS than in the RFS (P = .001). RFS may be advantageous for requiring less muscular work and elastic energy in the series elastic element compared with the FFS.

This study aimed to elucidate whether the peak (maximum) ground reaction force (GRF) can be used as an indicator of better sprint acceleration performance. Eighteen male sprinters performed 60-m maximal effort sprints, during which GRF for a 50-m distance was collected using a long force platform system. Then, step-to-step relationships of running acceleration with mean and peak GRFs were examined. In the anteroposterior direction, while the mean propulsive force was correlated with acceleration during the initial acceleration phase (to the 5th step) (

Purpose: We aimed to elucidate age-related differences in spatiotemporal and ground reaction force variables during sprinting in boys over a broad range of chronological ages. Methods: Ground reaction force signals during 50-m sprinting were recorded in 99 boys aged 6.5–15.4 years. Step-to-step spatiotemporal variables and mean forces were then calculated. Results: There was a slower rate of development in sprinting performance in the age span from 8.8 to 12.1 years compared with younger and older boys. During that age span, mean propulsive force was almost constant, and step frequency for older boys was lower regardless of sprinting phase. During the ages younger than 8.8 years and older than 12.1 years, sprint performance rapidly increased with increasing mean propulsive forces during the middle acceleration and maximal speed phases and during the initial acceleration phase. Conclusion: There was a stage of temporal slower development of sprinting ability from age 8.8 to 12.1 years, being characterized by unchanged propulsive force and decreased step frequency. Moreover, increasing propulsive forces during the middle acceleration and maximal speed phases and during the initial acceleration phase are probably responsible for the rapid development of sprinting ability before and after the period of temporal slower development of sprinting ability.

We aimed to investigate the step-to-step spatiotemporal variables and ground reaction forces during the acceleration phase for characterising intra-individual fastest sprinting within a single session. Step-to-step spatiotemporal variables and ground reaction forces produced by 15 male athletes were measured over a 50-m distance during repeated (three to five) 60-m sprints using a long force platform system. Differences in measured variables between the fastest and slowest trials were examined at each step until the 22nd step using a magnitude-based inferences approach. There were possibly-most likely higher running speed and step frequency (2nd to 22nd steps) and shorter support time (all steps) in the fastest trial than in the slowest trial. Moreover, for the fastest trial there were likely-very likely greater mean propulsive force during the initial four steps and possibly-very likely larger mean net anterior-posterior force until the 17th step. The current results demonstrate that better sprinting performance within a single session is probably achieved by 1) a high step frequency (except the initial step) with short support time at all steps, 2) exerting a greater mean propulsive force during initial acceleration, and 3) producing a greater mean net anterior-posterior force during initial and middle acceleration.

This study aimed to describe changes in step width (SW) during accelerated sprinting, and to clarify the relationship of SW with sprinting performance and ground reaction forces. 17 male athletes performed maximal-effort 60 m sprints. The SW and other spatiotemporal variables, as well as ground reaction impulses, over a 52 m distance were calculated. Average values for each 4 steps during acceleration were calculated to examine relationships among variables in different sections. The SW rapidly decreased up to the 13th step and slightly afterward during accelerated sprinting, showing a bilinear phase profile. The ratio of SW to the stature was significantly correlated with running speed based on average values over the 52 m distance and in the 9th–12th step section during accelerated sprinting. The SW ratio positively correlated with medial, lateral and mediolateral impulses in all step sections, except for medial impulse in the 17th–20th step section. These results indicate the importance of wider SW for better sprinting performance, especially in the 9th–12th step section. Moreover, the wider SW was associated with larger medial impulse and smaller lateral impulse, suggesting that a wide SW contributes to the production of greater mediolateral body velocity during accelerated sprinting.

Knee extension strength (KES) improves following body mass-based lower body exercise training; however, it is unknown whether this type of exercise increases handgrip strength (HGS) as a result of a cross-education effect in older individuals. Our aim was to investigate the effect of a body mass-based exercise intervention on HGS and KES in older adults. At baseline, 166 subjects started a 12-week intervention program, and 160 (108 women and 52 men) subjects completed the study. A self-selected group of 37 older adults (21 women and 16 men) served as a control group. HGS, KES, and ultrasound-derived anterior thigh muscle thickness (anterior thigh MT) were measured at baseline and post-testing, and relative strength of the knee extensor (KES/anterior thigh MT) was calculated. A linear regression model controlling for baseline values of body–mass index, % body fat, fat-free mass, HGS, chair stand time, anterior thigh MT, and KES/body mass ratio found a significant difference between control and training groups for KES post-testing values (p = 0.001) and anterior thigh MT post-testing values (p = 0.012), but not for HGS post-testing values (p = 0.287). Our results suggest that increases in lower body strength and muscle size following a 12-week lower body mass-based exercise intervention fail to translate into improvements in HGS.

Abrupt changes in kinematics during sprint acceleration called transitions have previously been observed. This study aimed to examine whether ground reaction force (GRF) variables during sprint acceleration also show specific features of the transitions. Twenty-one male sprinters performed 60-m sprints, during which GRF data were recorded. Step-to-step spatiotemporal and GRF variables were approximated using an exponential function and three straight lines. Moreover, statistical parametric mapping (SPM) was used to test changes in GRF curves across the transitions. For running speed, the exponential approximation resulted in smaller root-mean-square (RMS) of residuals. For the other variables, however, RMS of residuals was smaller when the three lines approximation was adopted. Breakpoints around the 5th and 15th steps were detected using effective vertical impulse during the braking phase with the three lines approximation. Across the breakpoints, SPM showed significant differences in the antero-posterior GRF curves at the next step after the first breakpoint and at the second breakpoint. Moreover, the second braking phase of the antero-posterior GRF appeared at the next step after the first breakpoint, and the corresponding first propulsive phase disappeared at the second breakpoint. Consequently, changes in GRF variables during sprint acceleration are likely accompanied by specific alterations. The breakpoints around the 5th and 15th steps found in an effective vertical impulse during the braking phase can be a criterion indicating transitions in GRF variables during sprint acceleration. The transitions are characterized by an appearance and disappearance of the second braking and first propulsive phases, respectively, of the antero-posterior GRF.

We aimed to elucidate spatiotemporal and kinetic determinants of sprint acceleration performance in soccer players. Thirty-seven male soccer players performed 60-m sprints. The spatiotemporal variables and ground reaction impulses were calculated over a 50-m distance. When controlling the influence of stature and body mass, change in running speed was correlated with the step length at the 1st&ndash, 4th step section (r = 0.695), step frequency from the 9th to 20th step sections (r = 0.428 to 0.484), braking impulse during the 17th&ndash, 20th step section (r = 0.328), propulsive impulse from the 1st to 8th step sections (r = 0.738 and 0.379), net anteroposterior impulse for all step sections (r = 0.384 to 0.678), and vertical impulse from the 9th&ndash, 12th step section and thereafter (r = &minus, 0.355 to &minus, 0.428). These results confirmed that an effective acceleration is probably accomplished by a greater step length originated in greater propulsive impulse during the initial acceleration phase (to the 8th step), a higher step frequency through smaller vertical impulse and smaller braking impulse during the middle and later acceleration phases (from the 9th step), as well as greater net anteroposterior impulse during the entire acceleration phase.

This study aimed to clarify the influence of vertical impulse on the magnitude of step length (SL) and frequency (SF) and their ratio during the entire acceleration phase of maximal sprinting. Thirty-nine male soccer players performed 60-m sprints, during which step-to-step ground reaction forces were recorded over a 50-m distance. The mean values of spatiotemporal variables and vertical and anteroposterior impulses for each set of four steps during the acceleration phase until the 28th step were computed to examine relationships among variables in seven sections. When controlling for the influence of running speed, stature and corresponding duration of braking or propulsion, vertical impulses during the propulsive phase at the 1st–4th step section and those during the braking phases in the sections from the 5th–8th to the 25th–28th step were positively correlated with SL and SL/SF ratio and negatively correlated with SF, whereas the anteroposterior impulses were not correlated with SL or SF. In conclusion, the current results demonstrate that vertical impulse during the propulsive phase in the initial acceleration stage and that during the braking phase in the middle and later acceleration stages are the most likely determinants of the combination of SL and SF during sprinting.

Although the moment arm of the triceps brachii muscle has been shown to be associated with the muscle’s anatomical crosssectional area, whether training-induced muscle hypertrophy alters the moment arm of the muscle remains unexplored. Therefore, the current study aimed to examine this. Eleven men underwent a 12-week resistance training program for the triceps brachii muscle. The maximum muscle anatomical cross-sectional area (ACSAmax), the moment arm of the triceps brachii muscle, and the anterior-posterior dimension of the olecranon were measured using a magnetic resonance imaging system before and after intervention. The ACSAmax (33.6 ± 11.9%, P < .001) and moment arm (5.5 ± 4.0%, P = .001) significantly increased after training, whereas the anterior-posterior dimension of the olecranon did not change (P > .05). The change in moment arm was smaller than that expected from the relationship between the ACSAmax and the moment arm before the intervention. The present results indicate that training-induced triceps brachii muscle hypertrophy could increase the muscle moment arm, but its impact can be small or negligible.

Background This study investigated the influence of shoe sole bending stiffness on sprint performance, in relation to anthropometric and strength-power capability characteristics of sprinters. Methods Seventeen male athletes performed three maximal effort 60-m sprints using spiked-shoes with different bending stiffness sole. Sprint times during 60-m sprint, anthropometry and strength-power capabilities represented by maximum toe-flexor test and rebound continuous ankle jump (AJ) of athletes were measured. Results The sprint times did not differ when shoe sole bending stiffness was altered by carbon fiber plates (CFPs) of 13.4 and 37.1 N/mm. The optimal bending stiffness for the fastest sprint was not associated with any anthropometric and strength-power variables. As results of stepwise-multiple-regression analyses, however, the left maximum toe-flexor strength (TFS) and contact time and jump height of rebound continuous AJ for a 0-30-m section with CFP of 13.4 N/mm, body mass for a 0-30-m section with CFP of 37.1 N/mm, and the left maximum TFS for a 30-60-m section with CFP of 37.1 N/mm were selected as predictors of changes in sprint times with stiffer sole shoes. Conclusions These results indicate that, although sole bending stiffness of spiked-shoe may not affect the sprinting performance on average, changes in sprint time by the use of stiffer sole spiked-shoe for individuals will be predicted by toe-flexor strength, rebound continuous AJ performance, and body mass. The findings obtained here can be useful information for sprinters and coaches to choose the spiked shoe with an appropriate bending stiffness of sole for individuals.

We aimed to clarify the mechanical determinants of sprinting performance during acceleration and maximal speed phases of a single sprint, using ground reaction forces (GRFs). While 18 male athletes performed a 60-m sprint, GRF was measured at every step over a 50-m distance from the start. Variables during the entire acceleration phase were approximated with a fourth-order polynomial. Subsequently, accelerations at 55%, 65%, 75%, 85%, and 95% of maximal speed, and running speed during the maximal speed phase were determined as sprinting performance variables. Ground reaction impulses and mean GRFs during the acceleration and maximal speed phases were selected as independent variables. Stepwise multiple regression analysis selected propulsive and braking impulses as contributors to acceleration at 55%-95% (β 0.72) and 75%-95% (β 0.18), respectively, of maximal speed. Moreover, mean vertical force was a contributor to maximal running speed (β = 0.48). The current results demonstrate that exerting a large propulsive force during the entire acceleration phase, suppressing braking force when approaching maximal speed, and producing a large vertical force during the maximal speed phase are essential for achieving greater acceleration and maintaining higher maximal speed, respectively.

The purpose of the present study was to clarify the combined effects of stretching and resistance training on the active and passive dorsiflexion range of motion of ankle joint. Sixteen young adult men were randomly assigned to a training (n=8) or a control (n=8) group. The training group trained one leg for the combined program of static calf stretching and dorsiflexors resistance training program (STR+TR) and the other leg for static stretching program only (STR). The training group executed stretching of both legs every day and resistance training every other day for six weeks. After the training program, in STR+TR side, both active and passive dorsiflexion range of motions significantly (P<0.05) increased and also isometric maximal voluntary dorsiflexion torque increased, while in STR side, only passive dorsiflexion range of motion increased. In passive dorsiflexion range of motion, increased dorsiflexion ROM was accompanied by increased tendon elongation not muscle elongation. In conclusion, the combined program of stretching for calf muscles and resistance training for dorsiflexors increases active as well as passive dorsiflexion range of motion, while static calf stretching program is effective only for the increase in passive dorsiflexion range of motion.

The purpose of this study was to examine the age-related site-specific muscle loss of the upper and lower extremities and trunk in men and women. Japanese nonobese adults aged 20–79 (n = 1559, 52 % women) had muscle thickness (MTH) measured by ultrasound at nine sites on the anterior and posterior aspects of the body. An MTH ratio located in the anterior and posterior aspects of the upper arm, upper leg, lower leg, and trunk was calculated. Site-specific muscle loss was defined as a ratio of MTH > 2 standard deviations below the mean for young adults in each segment. Age was inversely correlated (p

The purpose of this study was to examine the relationship between muscle architecture of the triceps brachii (TB) and joint performance during concentric elbow extensions. Twenty-two men performed maximal isometric and concentric elbow extensions against various loads. Joint torque and angular velocity during concentric contractions were measured, and joint power was calculated. Muscle length, cross-sectional areas, and volume of TB were measured from magnetic resonance images. Pennation angle (PA) of TB at rest was determined by ultrasonography. The PA was significantly correlated with the maximal isometric torque (r = .471), but not to the torque normalized by muscle volume (r = .312). A significant correlation was found between PA and the angular velocity at 0 kg load (r = .563), even when the angular velocity was normalized by the muscle length (r = .536). The PA was significantly correlated with the maximal joint power (r = .519), but not with the power normalized by muscle volume (r = .393). These results suggest that PA has a positive influence on the muscle shortening velocity during an unloaded movement, but does not have a significant influence on the maximum power generation in untrained men.

The present study aimed to examine the effect of short-term training utilizing voluntary co-contraction with maximal efforts. 23 healthy young men (training group: TG, n = 13; control group: CG, n = 10) participated in this study. TG conducted a 4-week training program (3 days/week), which consisted of 4 s simultaneous maximal voluntary contractions of elbow flexors and extensors at 90° of the elbow joint, followed by 4 s muscle relaxation (10 repetitions/set, 5 sets/day). Before and after the intervention, maximal voluntary isometric and isokinetic torques and the muscle thicknesses of the elbow flexors and extensors were determined. The electromyograms (EMGs) of the 2 muscle groups during isometric maximal voluntary contraction (MVC) were also recorded. After the intervention, CG did not show any significant changes in all measured variables. In TG, significant increases were found in the agonist EMG activities during MVC, and maximal isometric and isokinetic torques of the elbow flexors and extensors, without significant changes in the muscle thicknesses and involuntary coactivation levels during MVC. The current results indicate that the training mode with maximal voluntary co-contraction is effective for improving the force-generating capabilities of the exercising muscles, without any increases in the level of involuntary coactivation during MVC.

This study examined the validity of segmental bioelectrical impedance (BI) analysis for predicting the fat-free masses (FFMs) of whole-body and body segments in children including overweight individuals. The FFM and impedance (Z) values of arms, trunk, legs, and whole body were determined using a dual-energy X-ray absorptiometry and segmental BI analyses, respectively, in 149 boys and girls aged 6 to 12 years, who were divided into model-development (n = 74), cross-validation (n = 35), and overweight (n = 40) groups. Simple regression analysis was applied to (length)2/Z (BI index) for each of the whole-body and 3 segments to develop the prediction equations of the measured FFM of the related body part. In the model-development group, the BI index of each of the 3 segments and whole body was significantly correlated to the measured FFM (R2 = 0.867–0.932, standard error of estimation = 0.18–1.44 kg (5.9%–8.7%)). There was no significant difference between the measured and predicted FFM values without systematic error. The application of each equation derived in the model-development group to the cross-validation and overweight groups did not produce significant differences between the measured and predicted FFM values and systematic errors, with an exception that the arm FFM in the overweight group was overestimated. Segmental bioelectrical impedance analysis is useful for predicting the FFM of each of whole-body and body segments in children including overweight individuals, although the application for estimating arm FFM in overweight individuals requires a certain modification.

We developed a force measurement system in a soil-filled mound for measuring ground reaction forces (GRFs) acting on baseball pitchers and examined the reliability and validity of kinetic and kinematic parameters determined from the GRFs. Three soil-filled trays of dimensions that satisfied the official baseball rules were fixed onto 3 force platforms. Eight collegiate pitchers wearing baseball shoes with metal cleats were asked to throw 5 fastballs with maximum effort from the mound toward a catcher. The reliability of each parameter was determined for each subject as the coefficient of variation across the 5 pitches. The validity of the measurements was tested by comparing the outcomes either with the true values or the corresponding values computed from a motion capture system. The coefficients of variation in the repeated measurements of the peak forces ranged from 0.00 to 0.17, and were smaller for the pivot foot than the stride foot. The mean absolute errors in the impulses determined over the entire duration of pitching motion were 5.3 N˙s, 1.9 N˙s, and 8.2 N˙s for the X-, Y-, and Z-directions, respectively. These results suggest that the present method is reliable and valid for determining selected kinetic and kinematic parameters for analyzing pitching performance.

Aim Sit-to-stand (STS) test is extensively used to assess the functionality of the lower body in elderly people. This study aimed to examine how the score of STS can be associated with that of maximal walking (MW) tests through a cross-sectional as well as longitudinal analysis for non-disabled older women. Method Times taken for a 10-time-repeated STS (STS time) and 5-m MW (MW time) were determined before (pre) and after (post) a 3-month body mass-based exercise program in 154 non-disabled women aged 60 to 79 years. In addition to the time scores, STS and MW power indexes (STS-PI and MW-PI, respectively) were calculated using the following equations: STS-PI = (body height − 0.4) × body mass × 10/STS time and MW-PI = body mass × 5/MW time. Results At pre- and post-intervention, STS-PI was significantly correlated to MW-PI, with higher correlation coefficients (r = 0.545–0.567, P

This study examined the validity of muscle thickness (MT)-based prediction equation for the muscle volume of the quadriceps femoris (QFMV) by evaluating the applicability of a prediction equation previously derived from young men and by developing a new prediction equation in middle-aged and older individuals. The MT at the midpoint of the thigh anterior and QFMV were determined using ultrasonography and magnetic resonance imaging in 30 men and 30 women aged 51 to 77 years. First, we examined the validity of the MT-based prediction equation previously developed for young men to estimate the QFMV of middle-aged and older individuals. Second, we allocated the subjects to validation or cross-validation group and developed a prediction equation for estimating the QFMV using a stepwise multiple regression analysis. The published equation generated a small but a significant difference between the measured and estimated QFMV, with a systematic error depending on the size of QFMV. A multiple regression analysis for the validation group produced the following equation: QFMV (cm3) = (sex × 267.7) + (MT × 249.3) + (thigh length × 41.1) − 1663.7 (sex: man = 1, woman = 0). R 2 and SEE of the regression equation were 0.888 and 124.4 cm3 (12.0 %), respectively. The developed equation was validated and cross-validated. For middle-aged and older individuals, the prediction equation previously derived from young men is not applicable, and the newly developed prediction equation with sex, MT, and thigh length as independent variables is applicable for estimating QFMV.

It is unknown whether severe sarcopenia produces unfavorable effects on cardiovascular risk factors. To examine the influence of severe and moderate sarcopenia on selected cardiovascular risk factors, 687 men were screened; those exhibiting clinically relevant diseases and higher body fat percentage (25% fat) were excluded. A total of 410 men aged 40-76 years (mean age 56.0 years) were used for data analyses.Sarcopenia was defined as a skeletal muscle mass (SM) index (muscle mass/height squared) of 1-2 standard deviations (SD) below (moderate) or2 SDs below (severe) the mean for young adult men. Ultrasound-measured subcutaneous fat and muscle thicknesses were used to estimate the SM, percent body fat, and fat-free mass. Serum total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) levels were determined using fasting blood samples. Systolic blood pressure and diastolic blood pressure were also measured.HDL-C was similar among the groups, but TC was lower in severe and moderate sarcopenia groups compared to the normal group. As a result, the TC:HDL-C ratio was lower in the moderate and severe sarcopenia groups than in the normal group. After adjusting for age, body mass index (BMI), waist circumference, and percent body fat, HDL-C was lower in both sarcopenia groups compared to the normal group, but other parameters were similar among the groups. A low prevalence of high HDL-C and high prevalence of moderate HDL-C were observed in the severe and the moderate sarcopenia groups.Our results suggest that moderate and severe sarcopenia may influence the HDL-C level, although the values are still maintained in the clinically normal range.

FUJITA, E., H. KANEHISA, Y. YOSHITAKE, T. FUKUNAGA, and H. NISHIZONO. Association between Knee Extensor Strength and EMG Activities during Squat Movement. Med. Sci. Sports Exerc., Vol. 43, No. 12, pp. 2328–2334, 2011. Purpose: The present study aimed to clarify how the force-generating capability of quadriceps femoris (QF) is associated to its surface EMG activity during a body mass–based squat movement. Methods: Isometric knee extension torque (KET) during maximal voluntary contraction and EMG activities of the rectus femoris and vastus lateralis muscles during a body mass–based squat movement were determined in 53 men and 48 women age 19–90 yr, including 18 frail elderly persons who used the long-term care insurance system. The rectified EMG signals during the squat movement were averaged and normalized as the relative value (%EMGmax) to that during maximal voluntary contraction. The %EMGmax values for rectus femoris and vastus lateralis were averaged and used as an index representing the level of muscular activities of QF during the squat movement (QF %EMGmax). Results: QF %EMGmax was nonlinearly related to KET relative to body mass (KET/BM). Linear piecewise continuous regression analysis showed that there was a breakpoint of 1.9 NImIkg j1 in the relationship between the two variables. In individuals with KET/BM less than 1.9 NImIkg j1 ,Q F %EMG max rapidly increased as KET/BM decreased. Conclusions: The current results indicate that the activity level of QF during a body mass–based squat movement is influenced by its force generation capability. For individuals with a KET/BM less than 1.9 NImIkg j1 , body mass–based squat movement is considered to be a fairly high-intensity exercise. The breakpoint of 1.9 NImIkg j1 may be assumed to be a threshold level of knee extensor strength

TAKAI, Y., Y. KATSUMATA, Y. KAWAKAMI, H. KANEHISA, and T. FUKUNAGA. Ultrasound Method for Estimating the Cross-Sectional Area of the Psoas Major Muscle. Med. Sci. Sports Exerc., Vol. 43, No. 10, pp. 2000–2004, 2011. Purpose: The present study aimed to develop an ultrasonographic method for estimating the cross-sectional area of the psoas major muscle. Methods: The muscle cross-sectional area (CSAMRI) and thickness (MTMRI) of the psoas major muscle at L4–L5 on the right and left sides of the body were measured using magnetic resonance imaging in 11 healthy sedentary men age 21 to 25 yr. Ultrasonographic images were obtained at the corresponding sites where CSAMRI and MTMRI measurements were performed. From the ultrasonographic images, the thickness of the psoas major muscle (MTUS) was analyzed on both sides of the body. Results: The interclass correlation coefficient of MTUS measurements performed on two separated days was 0.951 for the right side and 0.971 for the left side. CSAMRI was significantly correlated to MTMRI (r = 0.934 for the right side and r = 0.910 for the left side). There was no significant difference between MTMRI (4.68 T 0.39 cm for the right side and 4.73 T 0.39 cm for the left side) and MTUS (4.67 T 0.40 cm for the right side and 4.72 T 0.43 cm for the left side). The MTUS was significantly correlated to MTMRI (r = 0.979 for the right side and r = 0.980 for the left side) and CSAMRI (r = 0.947 for the right side and r = 0.916 for the left side). Conclusion: The current results indicate that the psoas major muscle thickness determined by the ultrasonographic method is useful for estimating the cross-sectional area of the psoas major muscle. Key Words: B-MODE ULTRASONOGRAPHY, MRI, MUSCLE THICKNESS, MUSCLE CROSS-SECTIONAL AREA

The present study examined spatial changes in the muscle activation pattern with different contraction intensity using magnetic resonance imaging (MRI). Transverse relaxation time (T2)-weighted MRI was used to acquire 22 axial slices, which covered the entire medial gastrocnemius muscle, before and immediately after seven sets of 10 plantarflexions with loads that were approximately 20 and 60% of their one-repetition maximum, respectively. Reconstructions of the activated regions from MR images revealed the following: (1) the muscle activation determined by MRI correlated significantly (P < 0.05) with the results of electromyography; (2) the activated area distribution increased with increasing force levels; and (3) differential activation between 20 and 60% load was distributed in a spatially non-uniform manner within the muscle, and some regions indicated reduced activity. These results indicate that at submaximal contraction intensity, activation does not necessarily increase in the whole muscle with increase in contraction intensity.

The present study investigated the effect of movement frequencies on the behavior of fascicles and tendons of synergistic muscles. Seven male subjects performed ankle bending (calf-raise) exercises at four movement frequencies (1.33, 1.67, 1.84, and 2.00 Hz), performed with an identical range of ankle joint motion. The fascicle and tendon behavior of medial gastrocnemius (MG) and soleus (SOL) was measured by ultrasonography while kinematic and kinetic parameters of the ankle were recorded. The torque of ankle joint was larger at higher exercise frequencies. The length change of muscle decreased and that of tendon increased at higher frequencies both for MG and for SOL, with no significant inter-muscle differences in the relative changes of muscle or tendon lengths to that of MTU. Changes of pennation angles and electromyographic activities as a function of movement frequency were also comparable for MG and SOL. These results suggest that under a stretch-shortening cycle action, the muscle-tendon interaction is altered by the movement frequency toward greater use of tendon elastic energy to provide greater MTU power at a higher frequency. Results also suggest that the movement frequency dependence of fascicle and tendon behavior is comparable between MG and SOL.

The purpose of this study was to compare the age-related muscle loss in both the appendicular and trunk regions in 207 Japanese and 111 German men aged 20-62 years. Ultrasound-measured muscle thickness (MTH) was taken at eight sites from the anterior and posterior aspects of the body, and the MTH was expressed in terms relative to limb length (MTH/L) or standing height (MTH/Ht). In both the Japanese and Germans, age was correlated with quadriceps MTH (Japanese, r = -0·347; Germans, r = -0·292; both P

The aim of the present study was to examine elbow joint extension power-load characteristics with and without a countermovement. Eight male participants performed maximal elbow extensions with and without a countermovement against different loads (0, 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 kg). Electromyographic activity of the lateral and long heads of the triceps brachii and the biceps brachii muscles was recorded. The average joint power in the concentric phase was significantly enhanced in the countermovement condition at all loads except for 0 kg. The optimal load for the maximal joint power was greater in the countermovement (7.5 kg) than in the no countermovement condition (5.0 kg). Electromyographic activity was unchanged over the intensities and conditions. Our results suggest that the optimal load for the maximal joint power depends on the type of action (i.e. with or without a counter-movement), and that the enhanced joint power in the countermovement condition is due primarily to the storage and utilization of elastic energy.

In humans, an inhibitory via Ia afferent pathway from the medial gastrocnemius (MG) to the soleus (SOL) motoneuron pool has been suggested. Herein, we examined the relation between MG fascicle length changes and the SOL H-reflex modulation during passive knee movement. Twelve subjects performed static and passive (5 degrees s(-1)) knee movement tasks with the ankle immobilized using an isokinetic dynamometer in sitting posture. The maximal H- and M-waves were measured at four target angles (20 degrees, 40 degrees, 60 degrees, and 80 degrees flexion from full knee extension). The MG fascicles length and velocity were measured using a B-mode ultrasonic apparatus. Results demonstrated that the SOL Hmax/Mmax; i.e., ratio of the maximal H- to M-waves, was attenuated with increasing MG fascicle length in static tasks. The SOL Hmax/Mmax at 20 degrees was significantly attenuated compared with 60 degrees and 80 degrees with increasing MG fascicle length and lengthening velocity in passive knee extension. However, no significant differences in the SOL Hmax/Mmax were found across the target angles in the passive knee flexion task. In conclusion, as muscle spindles increase their discharge with lengthening fascicle velocity, but keep silent when fascicles shorten, our data suggest that lengthening the MG facilitates an inhibitory Ia pathway from MG to SOL, and modulates SOL motoneuron activity during movements.

The purpose of this study was to investigate changes in ankle joint stiffness and the associated changes in the gastrocnemius muscle and tendon due to static stretching. Seven healthy male participants lay supine with the hip and knee joints fully extended. The right ankle joint was rotated into dorsiflexion from a 30° plantar flexed position and the torque measured by a dynamometer. The ankle joint was maintained in a dorsiflexed position for 20 min (static stretching of the calf muscles). We performed surface electromyography of the medial and lateral gastrocnemii, the soleus, and the tibialis anterior of the right leg to confirm no muscle activity throughout static stretching and the passive test (passive dorsiflexion). During static stretching, the ankle joint angle and elongation of the gastrocnemius were recorded by goniometry and ultrasonography, respectively. Tendon elongation of the gastrocnemius was calculated based on the changes in the ankle joint angle and muscle elongation. In addit...

The purpose of this study was to determine the interindividual variability of the upper and lower limb muscle size in young men. Subjects were 655 Japanese men aged 18-39 years. They were sedentary and mildly to highly active individuals, including college athletes of various sports. Muscle thicknesses at each of the anterior and posterior portions of the upper arm, thigh, and lower leg were measured using B-mode ultrasonography. Interindividual variability of muscle thickness was evaluated by coefficients of variation (CVs). The CVs of muscle thicknesses were found to be in the order of upper arm posterior (17.7%), thigh anterior (14.8%), thigh posterior (12.6%), upper arm anterior (12.2%), lower leg anterior (9.8%), and lower leg posterior (9.4%). The CVs were significantly different between each pair of measurement sites except for those of upper arm anterior-thigh posterior and lower leg anterior-posterior. These differences remain significant even when the muscle thicknesses were normalized to the segment length. The observed differences in the size variability can be interpreted as muscle-related differences in hypertrophic responsiveness to resistance training. The muscle-dependent size variability may be related to the differences in the fiber-type composition and/or muscle usage in daily life among examined muscle groups.

The purpose of the present study was to examine the influence of tendon elasticity, muscle strength and muscle activities on the amount of mechanical work enhancement associated with a counter movement. Twenty-one athletes performed a unilateral maximal jump using only the ankle joint with (CMJ) and without (no-CMJ) a counter movement on a sledge apparatus. Mechanical work done by the ankle joint was calculated from the ground reaction force and ankle joint kinematic parameters, and the difference between CMJ and no-CMJ conditions (ΔWork) was determined. During the exercise, electromyographic (EMG) activities were recorded from the triceps surae muscles. The maximal isometric plantar flexion torque and Achilles tendon stiffness were also determined using a torque meter and ultrasonogram. No significant correlation was found between ΔWork and either tendon stiffness or the maximal torque. In addition, neither the difference between CMJ and no-CMJ in iEMG nor mEMG was correlated with ΔWork. On the other hand, ΔWork was significantly correlated with the integrated EMG during the braking phase (r=0.52, p

The present study examined the age-related changes in muscle thickness (MT) and volume (MV) of elbow flexors and developed a prediction equation of the MV based on the MT applicable to men and women with a wide range of age. The MT and MV were determined from a single ultrasonographic image and multiple magnetic resonance imaging scans, respectively, in 72 men and 75 women aged 19-77 year. As a result of examining the age-MT and age-MV relationships by calculation of partial correlation coefficients with the control variable of gender, MV was decreased with aging whereas the corresponding decline in MT was not significant. The subjects were randomly separated into either a validation (38 men and 42 women) or a cross-validation (34 men and 33 women) group, and a multiple regression equation to estimate MV using not only MT but also upper arm length (L), age and gender as independent variables [MV (cm(3)) = 60.8 x MT (cm) + 6.48 x L (cm) - 0.709 x age (year) + 51.4 x gender (0 women, 1 men) - 187.4] was validated and cross-validated. Thus, the prediction equation for MV of elbow flexors newly developed was shown to be applicable to men and women with a wide range of age.

Fatigue-induced changes in force production of synergist muscles were evaluated through observation of fascicle-tendon geometry and electromyography (EMG). Seven subjects performed 60 maximal isometric plantar flexions intermittently. No statistically significant intermuscle difference was observed in the decrease of mean EMG amplitudes or mean power frequency for the medial gastrocnemius (MG) and soleus (SOL) muscles. The tendon elongation of MG significantly decreased after the 19th contraction, and MG fascicle length increased after the 29th contraction, while SOL fascicle and tendon length did not change except for the last contraction. The declines in torques were highly correlated with the increase of MG fascicle length and decrease in tendon elongation in each subject, while no consistent relationship was found for SOL. These results suggest that changes in force-production of MG and SOL over repeated contractions differ, which is reflected in fascicle-tendon geometry.

Objective: the present study examined which of muscle volume (MV) and cross-sectional area (CSA) is appropriate for evaluating the relation with elbow flexor muscle strength in young and elderly individuals. Methods: the subjects were 52 young (20‐34 year; 30 men and 22 women) and 51 elderly individuals (60‐77 year, 19 men and 32 women). The MV and maximal anatomical CSA (ACSA) of elbow flexors were determined by magnetic resonance imaging. The torque developed during maximal voluntary contraction of isometric elbow joint flexion was converted to force by dividing it by the forearm length of each subject. Results: torque was significantly correlated with MV in young and elderly individuals (r = 0.564‐0.926). Similarly, force was also significantly correlated with ACSA in each of them (r = 0.637‐0.906). However, the y-intercepts of the regression lines for the ACSA-force relationship in young men and women were significantly higher than zero. There was no age effect on torque per MV, whereas force per ACSA was significantly higher in young adults than in elderly individuals. Conclusion: for elbow flexors, MV compared to ACSA is appropriate for evaluating the size‐strength relationship and the existence of age-related difference in muscle strength per size.

The present study examined how muscle cross-sectional area (CSA) indices determined at rest and during maximal voluntary contraction (MVC) are related to muscle strength in middle-aged and elderly individuals (22 men and 36 women, 51-77 years). The muscle thickness (MT) of elbow flexors and circumference (C) at the level 60% distal to the upper arm was measured by ultrasonography and a measuring tape, respectively, both at rest and during isometric MVC of elbow flexion. The muscle strength (F) of elbow flexors was calculated by dividing the torque developed during MVC by the forearm length of each subject. The product of MT and C (MTxC) and the square of MT (MT) were defined as the muscle CSA indices. The F was significantly correlated with MTxC during MVC (r = 0.905, p < or = 0.001) and at rest (r = 0.778, p < or = 0.001), with the former relationship significantly stronger than the latter (p < or = 0.001). Similarly, F was significantly correlated with MT both during MVC (r = 0.896, p < or = 0.001) and at rest (r = 0.780, p < or = 0.001), and there was also a significant difference between the correlation coefficients (p < or = 0.01). These findings show that, in middle-aged and elderly individuals, muscle strength is more closely related to muscle CSA indices during MVC than at rest. It is concluded that the present muscle CSA indices taken during MVC enable easy and practical evaluation of the muscle strength per size of elbow flexors in middle-aged and elderly individuals.

To investigate the relationship between fascicle behavior and joint torque, the fascicle behavior of the triceps surae during isometric and eccentric (30 and 60 deg/s) plantar flexion by maximal voluntary and submaximal electrical activation (MVA and SEA) was measured by real-time ultrasonography. Eccentric torque at 30 and 60 deg/s was significantly higher than isometric torque under SEA, but not under MVA. However, fascicle length did not significantly differ between isometric and eccentric trials under either condition. Therefore, the difference in developed torque by MVA and SEA cannot be explained by fascicle behavior. Under both MVA and SEA conditions, eccentric torque at 30 and 60 deg/s was equivalent. Similarly, fascicle lengthening velocities at 30 and 60deg/s did not show any significant difference. Such fascicle behavior can be attributed to the influence of tendinous tissue and pennation angle, and lead to a lack of increase in eccentric torque with increasing angular velocity.

This study compared the postactivation potentiation of the medial gastrocnemius (MG) and soleus muscles by using mechanomyography (MMG). Twitch responses were evoked by stimulating the posterior tibial nerve with supramaximal intensity before and after a 10-s maximal voluntary plantar flexion, and potentiation of each muscle was evaluated by peak-to-peak amplitude of the MMG signal. The MG showed greater potentiation than the soleus, reflecting the reported fiber type composition of these muscles. This result points to the possibility that one can delineate contrasting responses of synergist muscles to postactivation potentiation by this method. Muscle Nerve 39: 703-706, 2009.

The present study examined whether a sit-to-stand score can be related to the force-generating capacity of knee extensor muscles. Fifty-seven subjects (28 men, 63.0+/-7.8 yrs, and 29 women, 64.2+/-7.5 yrs, means+/-SDs) performed a 10-repeated sit-to-stand test as fast as possible, on a steel molded chair. The time taken (T(sit-stand)) was measured with a manual stopwatch. The leg length (L), defined as the distance from the great trochanter of the femur to the malleolus lateralis, was measured using a tape. A power index of the test (P(sit-stand)) was calculated by using the following equation: P(sit-stand)=(L-0.4) x body mass x g x 10/T(sit-stand). The cross-sectional area of the quadriceps femoris muscle (CSA(KE)) and the maximal voluntary isometric knee extension force (F(KE)) were measured using MRI and a static myometer, respectively. There was no significant correlation between T(sit-stand) and each of CSA(KE) and F(KE). On the other hand, the P(sit-stand) was highly correlated with CSA(KE) and F(KE), even after the influence of body mass and L was statistically eliminated. These results indicate that P(sit-stand), derived from three variables of body mass, leg length, and time taken for a sit-to-stand test, can be a useful index to assess the force-generating capacity of the knee extensor muscles of elderly individuals.