Introduction: Specificity and Plasticity of Skeletal Muscle Architecture
Yasuo Kawakami and Tetsuo Fukunaga
Specific Movement Power Related to Athletic Performance in Weight Lifting
Kazuo Funato, Akifumi Matsuo, and Tetsuo Fukunaga
In order to evaluate how mechanical power relates to athletic performance in weight lifting, specific movement power (SMP) was investigated using a newly developed dynamometer. Four simulated pull movements in weight lifting were measured: weight lifting pull (WL), second pull, back strength pull, and shoulder shrug pull. Subjects included 12 elite (EL) and 14 district (DI) level Japanese weight lifters. Athletic performance was defined as the highest total combined weight (snatch plus clean and jerk) lifted during competition. The highest SMP was observed in the WL. Force, velocity, and power relations were derived from the WL, showing higher velocity and power values in EL than DI at an identical force level. SMP in WL was found to be significantly correlated to athletic performance. SMP measured as a simulated pull movement in weight lifting employing the present dynamometer appears useful in evaluating athletic performance. Furthermore, this dynamometer provides force-velocity relationships during multiarticular explosive movements.
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.
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.
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.
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.
Muscle–Tendon Behavior and Kinetics in Gastrocnemius Medialis During Forefoot and Rearfoot Strike Running
Tomonari Takeshita, Hiroaki Noro, Keiichiro Hata, Taira Yoshida, Tetsuo Fukunaga, and Toshio Yanagiya
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 < .001 and 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.
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.
Reliability and Validity of Kinetic and Kinematic Parameters Determined With Force Plates Embedded Under a Soil-Filled Baseball Mound
Toshimasa Yanai, Akifumi Matsuo, Akira Maeda, Hiroki Nakamoto, Mirai Mizutani, Hiroaki Kanehisa, and Tetsuo Fukunaga
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.