Tetsuo Fukunaga

National Institute of Fitness and Sports in Kanoya · sports science

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 4...

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‐...

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...

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...

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...

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...

We aimed to elucidate the impact of the conducting state in exercise programs and the degree of improvement in sit-to-stand power index (STS-PI) on the continuation of Chokin exercise by participants one year from the completion of the intervention period. Subjects participated in a 12-week Chokin exercise class for the elderly, which consisted of...

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 durin...

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 (th...

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 approxi...

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 calculate...

Purpose We hypothesized that body mass-to-waist ratio is strongly associated with the total-body skeletal muscle volume (SMV) in children. The purpose of the present study was to examine this hypothesis. Methods By using magnetic resonance imaging, total-body SMV (SMVMRI) was determined in 70 boys and 53 girls aged 6 to 12 years. Waist was measure...

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 a...

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 three force pl...

Background: 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. Methods: The MT at the...

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 an...

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-repeate...

Introduction: Muscle injury such as muscle strain frequently occurs in the hamstring, especially in the long head of the biceps femoris (BFl). Pre-exercise stretching has been widely performed as one of the methods for preventing the hamstring muscle strain in sports. It has been reported that less flexibility of the hamstring muscle-tendon unit as...

Background: For middle-aged and elderly women, age-related decline in an index representing power production during STS task (STS-PI), calculated by using an equation reported previously, has been shown to be greater than that in the force generation capability of lower extremity. Whether this is specific to women remains unclear. This study exami...

The aims of this study were to determine contraction-induced changes in the elbow flexor cross-sectional area (CSA) and to examine whether the maximal CSA during a high-intensity contraction is more closely related to the strength than that at rest in the elbow flexors. Fourteen young male subjects participated in this study. The elbow flexor CSAs...

Although the moment arm of the triceps brachii muscle has been shown to be associated with the muscle's anatomical cross-sectional area, whether training-induced muscle hypertrophy alters the moment arm of the muscle remains unexplored. Therefore, the present study aimed to examine this. Eleven men underwent a 12-week resistance-training program fo...

Background This study examined whether the age-related change in power, calculated from the score of a sit-to-stand (STS) test, corresponds to those in knee extension torque and leg lean tissue mass in Japanese women aged 50 years or older. Findings Time for a 10-times-repeated STS test and knee extension torque were determined in 556 Japanese wom...

Objective This study aimed to examine the applicability of ultrasound muscle thickness (MT) measurements for predicting whole body fat-free mass (FFM) in elderly individuals. Design and setting Crosssectional study of 77 healthy elderly individuals. Methods MTs at nine sites of the body and FFM were determined using B-mode ultrasound and dual-ene...

Purpose To examine the relationships between body mass to waist circumference (BM:W) ratio or body mass index (BMI) and muscularity, 140 overweight (BMI ≥ 25 kg/m2 and <30 kg/m2), 265 normal weight (BMI > 18.5 kg/m2 and <25 kg/m2) and 26 underweight (BMI ≤ 18.5 kg/m2) Japanese women aged 60–80 years volunteered (overall 431 women). Methods Muscle...

The present study examined neuromuscular adaptations following 12-week maximal voluntary co-contraction training. Sixteen young men were allocated to training (TG, n = 9) or control (CG, n = 7) group. TG conducted a training program (3 days/week), which consisted of 4-s maximal voluntary contractions of elbow flexors and extensors by simultaneously...

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 an...

The skeletal muscle mass of the lower limb plays a role in its mobility during daily life. From the perspective of physical resources, leg muscle mass dominantly decreases after the end of the fifth decade. Therefore, an accurate estimate of the muscle mass is important for the middle-aged and older population. The present study aimed to clarify th...

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 4s simultaneous maximal voluntary contractions of...

The purpose of this study was to compare the prevalence of severe sarcopenia detected by total skeletal muscle mass (SM) index and of site-specific thigh sarcopenia for differing age groups in men and women. Japanese nonobese men and women aged 20 to 85 (n = 1,994, 55 % women) had muscle thickness (MTH) measured by ultrasound at six sites on the an...

Abstract To better understand the cascade from neural activation up to force production within in vivo contracting muscle-tendon units, we estimated activation of contractile elements from experimentally measured human fascicle length change and force using a Hill-type muscle model. The experiment was conducted with respect to twitch contractions o...

Body mass index (BMI), expressed as the ratio of body mass to height squared (kg/m2), involves not only fat but also lean mass. The present study aimed to clarify how BMI is associated with total muscle mass (TMM) in older Japanese women and men. Using a B-mode ultrasound apparatus, muscle thickness was measured at nine sites (forearm, upper arm an...

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 () or a control () group. The training group trained one leg for the combined program of static calf stretching...

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,...

Background: 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...

Asians seem to have less skeletal muscle mass (SMM) than other ethnic groups, but it is not clear whether relative SMM, i.e., SMM / height square or SMM to fat-free mass (FFM) ratio, differs among different ethnic groups at the same level of body mass index (BMI). To compare the SMM to fat-free mass (FFM) ratio as well as anthropometric variables a...

The purpose of the present study was to examine a hypothesis that the musculotendinous behavior during a propelling action with a countermovement can be altered by a single practice session through modulation of neuromuscular activities. Eight males performed unilateral maximal plantarflexion with (CMJ) and without (noCMJ) countermovement before an...

To compare the effect of habitual recreational sports and exercise activity on age-related, site-specific muscle loss in young and old women in Japan. Participants included 152 young (aged 20-35 years) and 157 old (aged 60-85 years) women who were classified into 4 subgroups on the basis of their habitual (more than once a week) sports and exercise...

The purpose of this study was to examine if the regional difference in muscle hypertrophy after chronic resistance training is associated with muscle activation after one session of resistance exercise. Twelve men performed one session of resistance exercise of elbow extensors. Before and immediately after the exercise, transverse relaxation time (...

In this study, we examined applicability of existing equations to predicting the body surface area (BSA) of children, and newly developed prediction equations for the BSA of children. BSA of 87 children of both genders (7∼12 yr) was determined by the three-dimensional photonic image scanning (3DPS), which was used as reference. BSA predicted using...

The purpose of this study was to highlight the issues related to thickness-based muscle size evaluation that is commonly done in field studies. The cross-sectional area, thickness (the vertical distance from the upper end of the elbow flexors to that of the humerus) and width (the horizontal distance from the left to the right end of the elbow flex...

In the present study, we examined the relationships between muscle volume and joint torque for the elbow flexors and extensors in young and elderly individuals, with the aim of evaluating age effects on these relationships. The participants were 45 young (27 men and 18 women aged 20–37 years) and 51 elderly (19 men and 32 women aged 60–77 years) in...

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/...

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...

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...

Findings from animal experiments are sometimes contradictory to the idea that the tendon structure is a simple elastic spring in series with muscle fibers, and suggest influence of muscle contraction on the tendon mechanical properties. The purpose of the present study was to investigate the influence of muscle contraction levels on the force-lengt...

# {#article-title-2} to the editor: As comprehensively explained in their Viewpoint article ([1][1]), the answer to the question posed in the title has received conflicting answers. Since the contractile machinery in children is the same as that in adults, there is no reason to believe that

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. 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...

We investigated the relationship between age and muscle size in both the appendicular and trunk regions of 1507 Japanese men and women aged 20 to 95 years. Seven hundred twenty-two men (young [aged 20-39 years], n = 211; middle-aged [aged 40-59 years], n = 347; and old [aged 6095 years], n = 164) and 785 women (young, n = 207; middle-aged, n = 341;...

The present study determined in vivo deformation of the entire Achilles tendon in the longitudinal and transverse directions during isometric plantar flexions. Twelve young women and men performed isometric plantar flexions at 0% (rest), 30%, and 60% of the maximal voluntary contraction (MVC) while a series of oblique longitudinal and cross-section...

The present study aimed to develop an ultrasonographic method for estimating the cross-sectional area of the psoas major muscle. The muscle cross-sectional area (CSA(MRI)) and thickness (MT(MRI)) 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...

This study investigated whether the drift in oxygen consumption (VO2 drift) during prolonged cycling exercise at the lactate threshold (LT) is smaller in endurance-trained subjects than in sedentary subjects, and whether the change in muscle activity assessed using electromyography (EMG) during prolonged exercise is affected by training status and...

The purpose of this study was to examine whether postactivation potentiation (PAP) influences dynamic torque development in humans. Nine recreationally active men performed sets of 3 maximal isokinetic concentric plantar flexions at 180 degrees/second in the following sequence: before and immediately (5 seconds) after a 10-second maximal voluntary...

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 o...

The purpose of this study was to test the hypothesis that the musculotendon moment arm length is affected by the muscle anatomical cross-sectional area. The moment arm length of the triceps brachii (TB) muscle at 30°, 50°, 70°, 90°, 110° elbow flexion positions was measured in sagittal magnetic resonance images (MRI) of 18 subjects as the perpendic...

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 a...

This study aimed to investigate whether fatigue-induced changes in synergistic muscle forces match their tendon elongation. The medial gastrocnemius muscle (MG) was fatigued by repeated electrical stimulation (1 min x 5 times: interval 30 s, intensity: 20-30% of maximal voluntary plantar flexion torque) applied at the muscle belly under a partial o...

The purpose of this study was to examine the effect of ankle joint angle on the intermuscle difference in postactivation potentiation (PAP) between the medial gastrocnemius (MG) and soleus (SOL) muscles. At the neutral position of joint angle, dorsiflexion of 20 degrees , and plantarflexion of 20 degrees , twitch responses were evoked by stimulatin...

To evaluate whether regularly performed rowing exercise affects the trunk muscles size and function, and to examine the effect of rowing exercise on thigh muscle size and function in elderly rowers, we compared the cross-sectional area (CSA) and strength of these muscles in elderly male rowers and in age-matched untrained men. Participants were 16...

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 t...

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...

The present study aimed to introduce a new index of muscle cross-sectional area (CSA) and to examine the relationship between the muscle CSA index determined during isometric maximal voluntary contraction (MVC) and muscle strength. As a result of the quantification of cross-sections of elbow flexor muscles at rest and during a low-intensity contrac...

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, respectivel...

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 tas...

The present study aimed to clarify the effects of knee joint angle on the behavior of the medial gastrocnemius muscle (MG) fascicles during eccentric plantar flexions. Eight male subjects performed maximal eccentric plantar flexions at two knee positions [fully extended (K0) and 90 degrees flexed (K90)]. The eccentric actions were preceded by stati...

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 pow...

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. 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...

This study was conducted to examine the reliability of three-dimensional photonic image scanning (3DPS) for measuring body surface area (BSA), and formulate equations for predicting BSA based on 3DPS. The surface area (SA) of a cylinder with known SA and BSA of 7 males were repeatedly measured by 3DPS. BSA was determined by 3DPS for 122 subjects (2...

The body composition of 36 professional Sumo wrestlers and 39 collegiate male students were assessed densitometrically. The means of body weight, BMI and %fat for Sumo wrestlers were 117.1 kg, 36.5 and 26.2%, extraordinarily large compared with untrained men (p < 0.001). Results of the analysis of variance of divisions of Sumo wrestlers revealed si...

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...

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 realtime ultrasonography. Eccentric torque at 30 and 60 deg/s was significantl...

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-t...

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...

The present study aimed to clarify age and gender differences in the electromyographic (EMG) activity levels of lower limb muscles during daily physical actions. Forty young and 22 elderly individuals performed five physical actions, i.e. normal walking, ascending and descending stairs, standing up from and sitting onto a chair, and a calf raise ex...

The aim of the present study was to examine differences in thigh muscularity and dynamic torque between elite junior (15.7 +/- 0.2 years) and senior (22.6 +/- 2.4 years) soccer players. Cross-sectional areas of the total muscle compartment, quadriceps femoris, and hamstrings + adductors were determined using magnetic resonance imaging. Knee extensi...

The purpose of the present study was to determine whether the frequency features of the MMG signals during quiet standing reflect body sway as well as recurring muscle activity. Twenty healthy men maintained quiet standing in a barefoot position with their eyes open or closed. During quiet standing, MMG detected using uniaxial piezoresistive accele...