Ballistic stretching

It is expected that the energy-diffusion propagator in a one-dimensional nonlinear lattice with three conserved quantities: energy, momentum, and stretch, consists of a central heat mode and two sound modes. The heat mode follows a Lévy distribution. Consequently, the heat diffusion is super, i.e., the second moment of the diffusion propagator diverges as t^{β} with β>1; and the heat conduction is anomalous, i.e., the heat conductivity is size dependent and diverges with size N by N^{α}, with α>0...

PURPOSE: During a soccer match, horizontal acceleration ability during short sprints is determinant for performance. Development of sprint force and velocity qualites have been reported after plyometric training. However, orientation of plyometric training exercises can influence the functional performance. The purpose of this study was to compare the horizontal and vertical orientation of plyometric training on explosiveness performances and sprint force-velocity profile in young soccer players...

Sasajima, S and Kubo, K. Effect of static stretching on tendon hysteresis and efficiency during repetitive jumping. J Strength Cond Res XX(X): 000-000, 2024-To date, no studies have experimentally shown a relationship between tendon hysteresis and exercise efficiency. However, previous studies showed that tendon hysteresis decreased immediately after static stretching. The purposes of this study were to (a) investigate the change in tendon hysteresis during the recovery period after static stretching and (b) determine whether exercise efficiency is enhanced because of the decline of tendon hysteresis after static stretching...

INTRODUCTION: Pelvic organ prolapse (POP) is a significant health concern for young Nepali women, with potential risk factors including pelvic floor trauma from vaginal delivery and heavy lifting. The prevalence of symptomatic POP (SPOP) among nulliparous women in Nepal is 6%, while the general population of Nepali women aged 15-49 years reports a prevalence of 7%. Surprisingly, the average age of SPOP onset in Nepal is 27 years, challenging the assumption that postmenopausal age and vaginal delivery are the sole risk factors...

BACKGROUND: Stretching has garnered significant attention in sports sciences, resulting in numerous studies. However, there is no comprehensive overview on investigation of stretching in healthy athletes. OBJECTIVES: To perform a systematic scoping review with an evidence gap map of stretching studies in healthy athletes, identify current gaps in the literature, and provide stakeholders with priorities for future research. METHODS: Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 and PRISMA-ScR guidelines were followed...

BACKGROUND: Warm-up is commonly performed by track-and-field athletes before performing maximal sprinting activities. Whilst some warm-up strategies may enhance athletes' physical and mental readiness, less is known about the current athletes' behaviors and warm-up practices in track and field. Therefore, this study aimed to identify the warm-up practices in a population of athletes performing in sprinting disciplines. METHODS: A cross-sectional exploratory study was performed in which track-and-field athletes, performing in athletics at a competitive level in disciplines requiring maximal acceleration and sprinting were recruited...

We present a study on the excitation of individual vibrational modes with ballistic charge carriers propagating along the Cu(110) surface. By means of the molecular nanoprobe technique, where the reversible switching of a molecule-in this case tautomerization of porphycene-is utilized to detect excitation events, we reveal anisotropic coupling of two distinct vibrational modes to the substrate. The N-H bending mode, excited below | E | ≈ 376 meV, exhibits maxima perpendicular to the rows of the Cu(110) substrate and minima along the rows...

BACKGROUND: It is well known that stretch training can induce prolonged increases in joint range of motion (ROM). However, to date more information is needed regarding which training variables might have greater influence on improvements in flexibility. Thus, the purpose of this meta-analysis was to investigate the effects of stretch training on ROM in healthy participants by considering potential moderating variables, such as stretching technique, intensity, duration, frequency, and muscles stretched, as well as sex-specific, age-specific, and/or trained state-specific adaptations to stretch training...

Over the last decade, acute increases in range of motion (ROM) in response to foam rolling (FR) have been frequently reported. Compared to stretching, FR-induced ROM increases were not typically accompanied by a performance (e.g., force, power, endurance) deficit. Consequently, the inclusion of FR in warm-up routines was frequently recommended, especially since literature pointed out non-local ROM increases after FR. However, to attribute ROM increases to FR it must be ensured that such adaptations do not occur as a result of simple warm-up effects, as significant increases in ROM can also be assumed as a result of active warm-up routines...

Stretch reflexes are crucial for performing accurate movements and providing rapid corrections for unpredictable perturbations. Stretch reflexes are modulated by supraspinal structures via corticofugal pathways. Neural activity in these structures is difficult to observe directly, but the characterization of reflex excitability during volitional movement can be used to study how these structures modulate reflexes and how neurological injuries impact this control such as in spasticity after stroke. We have developed a novel protocol to quantify stretch reflex excitability during ballistic reaching...

The present study aimed to examine the effects of muscle-tendon mechanical properties and electromyographic activity on joint stiffness and jumping height and to explore the determinants of joint stiffness and jumping height. Twenty-nine males performed unilateral drop jumps at three drop heights (10, 20, and 30 cm) using only the ankle joint on the sledge apparatus. Ankle joint stiffness, jumping height, and electromyographic activity of the plantar flexor muscles were measured during drop jumps. Active muscle stiffness of the medial gastrocnemius muscle was calculated according to changes in the estimated muscle force and fascicle length during fast stretching at five different angular velocities (100, 200, 300, 500, and 600 deg s-1 ) after submaximal isometric contractions...

We predict a novel metallic state of matter that emerges in a Weyl-semimetal superstructure with spatially varying Weyl-node positions. In the new state, the Weyl nodes are stretched into extended, anisotropic Fermi surfaces, which can be understood as being built from Fermi arclike states. This "Fermi-arc metal" exhibits the chiral anomaly of the parental Weyl semimetal. However, unlike in the parental Weyl semimetal, in the Fermi-arc metal the "ultraquantum state," in which the anomalous chiral Landau level is the only state at the Fermi energy, is already reached for a finite energy window at zero magnetic field...

Poly(amic acid) (PAA) materials as the precursor of polyimide generally show remarkably poor mechanical properties, thus limiting their application as the engineering plastics. In this study, we demonstrate that the mechanical properties of PAA materials can be improved significantly for tens of folds with breaking strength > 50 MPa, Young's modulus > 400 MPa, and elongation at break > 300% by incorporation of 20% (mol%) poly(propylene glycol) (PPO) soft segments. The optimization for suitable hard-soft composition with 20% PPO and the existence of various hydrogen bonds with different binding energies can dissipate energies efficiently, which simultaneously improve the material strength and toughness...

The idea of flexible body armor has been around for many years. Initial development included shear thickening fluid (STF) as a backbone polymer to impregnate ballistic fibers such as Kevlar. At the core of the ballistic and spike resistance was the instantaneous rise in viscosity of STF during impact. Increase in viscosity was due to the hydroclustering of silica nanoparticles dispersed in polyethylene glycol (PEG) through a centrifuge and evaporation process. When STF composite was dry, hydroclustering was not possible due to absence of any fluidity in PEG...

This study aims to compare the effects of standard warm-up versus warm-up using stretching exercises on the physical performance of male youth soccer players. Eighty-five male soccer players (age: 10.3 ± 4.3 years; body mass index: 19.8 ± 4.3 kg/m2 ) were assessed for countermovement jump height (CMJ, cm), 10 m, 20 m and 30 m running sprint speed (s) and ball kicking speed (km/h) for the dominant and non-dominant leg under five (randomized) warm-up conditions. Using 72 h of recovery between conditions, the participants completed a control condition (CC) and four experimental conditions, including static stretching (SSC), dynamic stretching (DSC), ballistic stretching (BSC), and proprioceptive neuromuscular facilitation (PNFC) exercises...

Stretching can affect balance ability by generating biomechanical and physiological changes in the postural muscles. Stretching of the lower extremity muscles can greatly affect posture maintenance strategies and balance ability. However, the relationship between stretching and balance ability has not been clarified. Therefore, this study aimed to investigate the effect of plantar flexor stretching on balance ability. Forty-four healthy young adults were randomly assigned to four groups (static stretching, dynamic stretching, ballistic stretching, and control)...

PURPOSE: To quantify the acute effects of a spectrum of eccentric load reductions on neuromechanical adjustments during the performance of weighted jump squats (WJSs). METHODS: On separate days, 16 well-trained participants performed WJS trials with various eccentric load reductions (0% [body mass only], 25%, 50%, 75%, and 100% [standard WJS] of concentric load) with a mechanical braking unit, while concentric load was set at 30% of peak isometric squat force in all trials...

The spinal stretch reflex is a fundamental building block of motor function, with a sensitivity that varies continuously during movement and when changing between movement and posture. Many have investigated task-dependent reflex sensitivity, but few have provided simple, quantitative analyses of the relationship between the volitional control and stretch reflex sensitivity throughout tasks that require coordinated activity of several muscles. Here we develop such an analysis and use it to test the hypothesis that modulation of reflex sensitivity during movement can be explained by the balance of activity within agonist and antagonist muscles better than by activity only in the muscle homonymous with the reflex...

The gelation of PEGylated gold nanoparticles dispersed in a glycerol-water mixture is probed in situ by x-ray photon correlation spectroscopy. Following the evolution of structure and dynamics over 104 s, a three-step gelation process is found. First, a simultaneous increase of the Ornstein-Zernike length ξ and slowdown of dynamics is characterized by an anomalous q-dependence of the relaxation times of τ ∝ q-6 and strongly stretched intermediate scattering functions. After the structure of the gel network has been established, evidenced by a constant ξ, the dynamics show aging during the second gelation step accompanied by a change toward ballistic dynamics with τ ∝ q-1 and compressed correlation functions...

QUESTIONS: In people recovering from traumatic brain injury, is a 3-month ballistic resistance training program targeting three lower limb muscle groups more effective than non-ballistic exercise rehabilitation for improving mobility, strength and balance? Does improved mobility translate to better health-related quality of life? DESIGN: A prospective, multicentre, randomised trial with concealed allocation, intention-to-treat analysis and blinded measurement. PARTICIPANTS: A total of 144 people with a neurological movement disorder affecting mobility as a result of traumatic brain injury...