The purpose of the present study was to elucidate how plyometric training improves stretch–shortening cycle (SSC) exercise performance in terms of muscle strength, tendon stiffness, and muscle–tendon behavior during SSC exercise. Eleven men were assigned to a training group and ten to a control group. Subjects in the training group performed depth jumps (DJ) using only the ankle joint for 12 weeks. Before and after the period, we observed reaction forces at foot, muscle–tendon behavior of the gastrocnemius, and electromyographic activities of the triceps surae and tibialis anterior during DJ. Maximal static plantar flexion strength and Achilles tendon stiffness were also determined. In the training group, maximal strength remained unchanged while tendon stiffness increased. The force impulse of DJ increased, with a shorter contact time and larger reaction force over the latter half of braking and initial half of propulsion phases. In the latter half of braking phase, the average electromyographic activity (mEMG) increased in the triceps surae and decreased in tibialis anterior, while fascicle behavior of the gastrocnemius remained unchanged. In the initial half of propulsion, mEMG of triceps surae and shortening velocity of gastrocnemius fascicle decreased, while shortening velocity of the tendon increased. These results suggest that the following mechanisms play an important role in improving SSC exercise performance through plyometric training: (1) optimization of muscle–tendon behavior of the agonists, associated with alteration in the neuromuscular activity during SSC exercise and increase in tendon stiffness and (2) decrease in the neuromuscular activity of antagonists during a counter movement.

PurposeInstrument-assisted soft tissue mobilization (IASTM) has been reported to improve joint range of motion (flexibility). However, it is not clear whether this change in the joint range of motion is accompanied by any alterations in the mechanical and/or neural properties. This study aimed to investigate the effects of IASTM in plantarflexors and Achilles tendon on the mechanical and neural properties of them.MethodsThis randomized, controlled, crossover study included 14 healthy volunteers (11 men and 3 women, 21–32 yr). IASTM was performed on the skin over the posterior part of the lower leg for 5 min and targeted the soft tissues (gastrocnemii, soleus, and tibialis posterior muscles; overlying deep fascia; and Achilles tendon). As a control condition, the same participants rested for 5 min between pre- and postmeasurements without IASTM on a separate day. The maximal ankle joint dorsiflexion angle (dorsiflexion range of motion), the peak passive torque (stretch tolerance), and the ankle joint stiffness (slope of the relationship between passive torque and ankle joint angle) during the measurement of the dorsiflexion range of motion and muscle stiffness of the triceps surae (using shear wave elastography) were measured before and immediately after the interventions.ResultsAfter IASTM, the dorsiflexion range of motion significantly increased by 10.7% ± 10.8% and ankle joint stiffness significantly decreased by −6.2% ± 10.1%. However, peak passive torque and muscle stiffness did not change. All variables remained unchanged in the repeated measurements of controls.ConclusionIASTM can improve joint range of motion, without affecting the mechanical and neural properties of the treated muscles.

Ikeda, N and Ryushi, T. Effects of 6-week static stretching of knee extensors on flexibility, muscle strength, jump performance, and muscle endurance. J Strength Cond Res XX(X): 000-000, 2018-The purpose of this study was to evaluate the changes in flexibility and muscular performance after stretching training for 6 weeks. Twelve healthy young men were assigned to a stretching group and 13 to a control group. The participants of the stretching group performed static stretching of knee extensors for 6 weeks. Knee flexion range of motion (KFROM), leg extension strength, rate of force development (RFD) in leg extension, jump performance (squat and countermovement jump height, and index of rebound jump), and strength decrement index of 50 repetitions of isokinetic knee extension (muscle endurance) were measured before and after the interventions. In the stretching group, KFROM significantly increased from 145.2 ± 17.3 to 158.7 ± 6.3° (p < 0.05), whereas RFD significantly improved from 10,173 ± 2,401 to 11,883 ± 2,494 N·s (p < 0.05). By contrast, leg extension strength and jump performance of each jump type did not improve significantly. Furthermore, muscle endurance decreased significantly. All variables remained unchanged in the control group. In conclusion, 6 weeks of stretching training of knee extensors improved KFROM and RFD in leg extension, but not leg extension strength and jump performance; moreover, muscle endurance decreased. These findings indicate that this stretching training protocol can be used by athletes in sports who require high flexibility and those who require high-power exertion.

Computational fluid dynamics (CFD) is considered to be a promising tool for haemodynamic analysis of the intracranial aneurysm. However, aneurysm CFD is still not regarded as fully reliable mainly because the computational result is influenced by too many factors such as the luminal geometry of the model, spatiotemporal resolutions and boundary conditions. Among the influential factors, this paper focuses on outflow boundary conditions used when the computational domain has multiple outlets. Four outflow strategies found in published articles are reviewed: 1) prescription of constant or zero pressure, 2) flow splitting based on the power law, 3) traction-free and zero velocitygradient conditions and 4) coupling of CFD with a reducedorder model. None of them has proved definitely superior or inferior to others. For accurate quantification of the haemodynamic state in the aneurysm, it is crucial to incorporate the physiologically correct flow splitting ratio in CFD analysis by means of accurate specification of pressure or flow rate at the outlets. A coupling of CFD and a 0-d model (a subtype of the reduced-order model) appears to be the most promising although further study is necessary to achieve accurate estimation of model parameters.

A novel stretching modality was developed to provide repetitive small length changes to the plantar flexors undergoing passive stretch defined as "minute oscillation stretching" (MOS). This study investigated the effects of MOS on neuromuscular activity during force production, the rate of torque development (RTD), and the elastic properties of the plantar flexors and Achilles tendon. Ten healthy males participated in this study. The neuromuscular activity of the triceps surae and tibialis anterior muscles during maximal voluntary plantar flexion torque [MVT], RTD of plantar flexion, Achilles tendon stiffness, and muscle stiffness were measured before and after two types of interventions for a total of 5 minutes: static stretching (SS) and MOS at 15 Hz and without intervention (control). Achilles tendon stiffness was calculated from the tendon elongation measuring by ultrasonography. Muscle stiffness was determined for the medial gastrocnemius [MG] using shear wave elastography. The MVT, mean electromyographic amplitudes [mEMG] of MG and lateral gastrocnemius [LG], and RTD were significantly decreased following SS (MVT: −7.2 ± 7.9%; mEMG of MG: −8.7 ± 10.2%; mEMG of LG: −12.4 ± 10.5%; RTD: −6.6 ± 6.8%), but not after MOS. Achilles tendon stiffness significantly decreased after SS (−13.4 ± 12.3%) and MOS (−9.7 ± 11.5%), with no significant differences between them. Muscle stiffness significantly decreased in SS and MOS, with relative changes being significantly greater for MOS (−7.9 ± 8.3%) than SS (−2.3 ± 2.9%) interventions. All variables remained unchanged in the controls. In conclusion, MOS changed muscle‐tendon compliance without loss of muscle function.

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accompanied by a significantly larger muscle elongation but not tendon elongation. Elevated 36 dorsiflexion range of motion was maintained until 30 min after the local vibration stretching 37 while it returned to baseline level (pre-intervention) in 15 min after the static stretching. 38All variables remained unchanged in the control condition. In conclusion, local vibration 39 stretching improves extensibility of the muscle belly without decreasing strength, and the 40 increased flexibility is retained longer than static stretching.

Abstract"Priority Urban Redevelopment Areas" in Tokyo, Japan, are currently undergoing large-scale urban renewal. However, the heat island phenomenon has become a serious problem in large cities in Japan.We surveyed the temperature and wind conditions in two adjacent areas: a new skyscraper district on the coast (A district) and a typical inland urban district (B district). Our observations indicated local temperature increases and unstable wind with weak velocity in B district.It is possible that differences in the wind environment infl uence the local temperature. We analyzed the relationship between undulations in ground level and the wind environment by wind tunnel experiments. The results confi rmed that there was a weak wind area in B district located behind A district from the direction of the coastline.Our fi ndings indicate that it is important to consider the heat island phenomenon in urban planning in order to make best use of the cooling effect of the breeze from the sea at waterfront areas.Keywords: cooling effect of the sea breeze; heat island phenomenon; urban structure