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Comparison of Elasticity of Human Tendon and Aponeurosis in Knee Extensors and Ankle Plantar Flexors in Vivo

Keitaro Kubo, Hiroaki Kanehisa, and Tetsuo Fukunaga

The purposes of this study were to compare the elasticity of tendon and aponeurosis in human knee extensors and ankle plantar flexors in vivo and to examine whether the maximal strain of tendon was correlated to that of aponeurosis. The elongation of tendon and aponeurosis during isometric knee extension (n = 23) and ankle plantar flexion (n = 22), respectively, were determined using a real-time ultrasonic apparatus, while the participants performed ramp isometric contractions up to voluntary maximum. To calculate the strain values from the measured elongation, we measured the respective length of tendon and aponeurosis. For the knee extensors, the maximal strain of aponeurosis (12.1 ± 2.8%) was significantly greater than that of the patella tendon (8.3 ± 2.4%), p < 0.001. On the contrary, the maximal strain of Achilles tendon (5.9 ± 1.4%) was significantly greater than that of aponeurosis in ankle plantar flexors (2.7 ± 1.4%), p < 0.001. Furthermore, for both knee extensors and ankle plantar flexors there was no significant correlation between maximal strain of tendon and aponeurosis. These results would be important for understanding the different roles of tendon and aponeurosis during human movements and for more accurate muscle modeling.

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Transverse Strain of Aponeurosis in Human Tibialis Anterior Muscle at Rest and during Contraction at Different Joint Angles

Tetsuro Muraoka, Tadashi Muramatsu, Hiroaki Kanehisa, and Tetsuo Fukunaga

The aim of the present study was to determine the transverse strain of aponeuroses in human tibialis anterior muscle (TA) in vivo and to clarify the influence of muscle fiber length and state of contraction on the transverse strain. Sagittal and horizontal images of TA were taken in seven men and one woman at ankle angles of –20° (dorsiflexed direction), 0° (neutral anatomic position), and 45° (plantar-flexed direction) both at rest and during submaximal dorsiflexion contraction (20 Nm: 0° and 45°; 10 Nm: –20°) using B-mode ultrasonography. The width of the TA central aponeurosis changed from 21.7 ± 1.0 (mean ± SE) to 25.5 ± 1.1 mm when muscle fiber length changed from 91.0 ± 3.5 (45° in the resting state) to 55.1 ± 3.2 mm (–20° in the active state). The transverse strain of the TA central aponeurosis, which was change in relative width compared with the width at 45° in the resting state, increased when the muscle fiber length decreased. The transverse strain of the TA central aponeurosis was directly proportional to the muscle fiber length to the –1/2 power in both resting and active states (R = 0.81 and 0.74, p < 0.05 for both), and there was no significant difference (p < 0.05) between correlation coefficients and regression slopes for resting and active states. The findings suggest that the transverse strain of the TA central aponeurosis was closely related to muscle fiber length and that the transverse strain of the aponeurosis should be considered for accurate 3-D muscle modeling.

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Associations Between Individual Lower-Limb Muscle Volumes and 100-m Sprint Time in Male Sprinters

Norihide Sugisaki, Kai Kobayashi, Hiroyasu Tsuchie, and Hiroaki Kanehisa

Purpose: To elucidate the relationship between the muscularity of individual lower-limb muscles and 100-m-race time (t 100) in young-adult male sprinters. Methods: Thirty-one young-adult male sprinters took part in this study (age 19.9 ± 1.4 y, height 173.5 ± 4.6 cm, body mass 67.0 ± 4.9 kg, t 100 10.23–11.71 s). Cross-sectional images from the origin to insertion of 12 lower-limb muscles were obtained with via magnetic resonance imaging (MRI). The absolute volume of each muscle, the ratio of total volume of measured muscles to body mass, the ratio of individual muscle volume to body mass, and the ratio between 2 individual muscle volumes were calculated as indices of muscularity using the images. A stepwise multiple-regression analysis was performed to examine the association between the indices and t 100. Results: A stepwise multiple-regression analysis produced an equation (adjusted R 2 = .234) with the gluteus maximus–to–quadriceps femoris muscle-volume ratio (β = −0.509, P = .003) as the explanatory variable. Conclusions: Individual differences in 100-m-race performance cannot be explained by the muscularity of specific muscles, and 23% of the variability in the performance can be explained by the relative difference between the muscularity of gluteus maximus and quadriceps femoris; faster runners have a greater gluteus maximus relative to quadriceps femoris.

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Relationship Between Muscle Architecture and Joint Performance During Concentric Contractions in Humans

Taku Wakahara, Hiroaki Kanehisa, Yasuo Kawakami, Tetsuo Fukunaga, and Toshimasa Yanai

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.

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The Effects of Ankle Restriction on the Multijoint Coordination of Vertical Jumping

Hiroshi Arakawa, Akinori Nagano, Dean C. Hay, and Hiroaki Kanehisa

The current study aimed to investigate the effect of ankle restriction on the coordination of vertical jumping and discuss the influence of energy transfer through m. gastrocnemius on the multijoint movement. Eight participants performed two types of vertical jumps: a normal squat jump, and a squat jump with restricted ankle joint movement. Mechanical outputs were calculated using an inverse dynamics analysis. Custom-made shoes were used to restrict plantar flexion, resulting in significantly (P < .001) reduced maximum power and work at the ankle joint to below 2% and 3%, while maintaining natural range of motion at the hip and knee. Based on the comparison between the two types of jumps, we determined that the ankle restriction increased (P < .001) the power (827 ± 346 W vs. 1276 ± 326 W) and work (92 ± 34 J vs. 144 ± 36 J) at the knee joint. A large part of the enhanced output at the knee is assumed to be due to ankle restriction, which results in the nullification of energy transport via m. gastrocnemius; that is, reduced contribution of the energy transfer with ankle restriction appeared as augmentation at the knee joint.

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Association of Sprint Performance With Ground Reaction Forces During Acceleration and Maximal Speed Phases in a Single Sprint

Ryu Nagahara, Mirai Mizutani, Akifumi Matsuo, Hiroaki Kanehisa, and Tetsuo Fukunaga

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.

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Effects of Training on Muscle and Tendon in Knee Extensors and Plantar Flexors in Vivo

Keitaro Kubo, Toshihiro Ikebukuro, Hideaki Yata, Naoya Tsunoda, and Hiroaki Kanehisa

The purpose of this study was to compare the effects of resistance training on muscle and tendon properties between knee extensors and plantar flexors in vivo. Twenty healthy young men voluntarily participated in this study. The subjects were randomly divided into two training groups: knee extension group (n = 10) and plantar flexion group (n = 10). They performed five sets of exercises with a 1-min rest between sets, which consisted of unilateral knee extension for the knee extension group and plantar flexion for the plantar flexion group at 80% of 1 repetition maximum with 10 repetitions per set (4 days/wk, 12 wk). Before and after training, muscle strength, neural activation level (by interpolated twitch), muscle volume (by magnetic resonance imaging), and tendon stiffness (by ultrasonography) were measured. There were no differences in the training-induced increases in muscle strength, activation level, muscle volume, and tendon stiffness between knee extensors and plantar flexors. These results suggested that if the used protocol of training (i.e., intensity, repetition, etc.) were the same, there were no differences in the training-induced changes in muscle and tendon properties between knee extensors and plantar flexors.

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Relationship Between Muscle Cocontraction and Proficiency in Whole-Body Sensorimotor Synchronization: A Comparison Study of Street Dancers and Nondancers

Akito Miura, Kazutoshi Kudo, Tatsuyuki Ohtsuki, Hiroaki Kanehisa, and Kimitaka Nakazawa

In this study, we investigated muscle cocontraction during a street dance movement task to provide evidence that the level of muscle cocontraction is associated with degree of proficiency in whole-body sensorimotor synchronization movement. Skilled street dancers and nondancers were required to synchronize a knee-bending movement in a standing position to a metronome beat. The dancer group showed significantly smaller variability of temporal deviation (defined as the peak kneeflexion time minus beat onset time), and lower level of muscle cocontraction analyzed by electromyographic data of the agonist and antagonist muscles of the upper and lower leg than did the nondancer group. In addition, multiple regression analyses revealed that the group effect significantly predicted the level of muscle cocontraction. These results show that the level of muscle cocontraction in the lower limbs during whole-body sensorimotor synchronization movement is associated with the degree of proficiency of the movement.

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In Vivo Measurements of Moment Arm Lengths of Three Elbow Flexors at Rest and During Isometric Contractions

Ryota Akagi, Soichiro Iwanuma, Satoru Hashizume, Hiroaki Kanehisa, Toshimasa Yanai, and Yasuo Kawakami

The purpose of this study was to determine in vivo moment arm lengths (MAs) of three elbow flexors at rest and during low- and relatively high-intensity contractions, and to examine the contraction intensity dependence of MAs at different joint positions. At 50°, 80° and 110° of elbow flexion, MAs of the biceps brachii, brachialis and brachioradialis were measured in 10 young men using sagittal images of the right arm obtained by magnetic resonance imaging, at rest and during 20% and 60% of isometric maximal voluntary elbow flexion. In most conditions, MAs increased with isometric contractions, which is presumably due to the contraction-induced thickening of the muscles. This phenomenon was especially evident in the flexed elbow positions. The influence of the contraction intensities on the increases in MAs varied across the muscles. These results suggest that in vivo measurements of each elbow flexor MA during contractions are essential to properly examine the effects on the interrelationships between elbow flexion torque and individual muscle forces.

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Estimation of Passive Ankle Joint Moment during Standing and Walking

Tetsuro Muraoka, Tadashi Muramatsu, Daisuke Takeshita, Hiroaki Kanehisa, and Tetsuo Fukunaga

This study estimated the passive ankle joint moment during standing and walking initiation and its contribution to total ankle joint moment during that time. The decrement of passive joint moment due to muscle fascicle shortening upon contraction was taken into account. Muscle fascicle length in the medial gastrocnemius, which was assumed to represent muscle fascicle length in plantarflexors, was measured using ultrasonography during standing, walking initiation, and cyclical slow passive ankle joint motion. Total ankle joint moment during standing and walking initiation was calculated from ground reaction forces and joint kinematics. Passive ankle joint moment during the cyclical ankle joint motion was measured via a dynamometer. Passive ankle joint moment during standing and at the time (Tp) when the MG muscle-tendon complex length was longest in the stance phase during walking initiation were 2.3 and 5.4 Nm, respectively. The muscle fascicle shortened by 2.9 mm during standing compared with the length at rest, which decreased the contribution of passive joint moment from 19.9% to 17.4%. The muscle fascicle shortened by 4.3 mm at Tp compared with the length at rest, which decreased the contribution of passive joint moment from 8.0% to 5.8%. These findings suggest that (a) passive ankle joint moment plays an important role during standing and walking initiation even in view of the decrement of passive joint moment due to muscle fascicle shortening upon muscle contraction, and (b) muscle fascicle shortening upon muscle contraction must be taken into account when estimating passive joint moment during movements.