Search Results (5,127)

Background/Objectives: Whether caffeine provides additional benefit when superimposed on individualized plyometric conditioning remains unclear. We examined whether 3 mg·kg⁻¹ caffeine altered the temporal countermovement jump (CMJ) response following reactive strength index (RSI)-derived individualized drop-jump (DJ) conditioning and explored moderation by habitual caffeine exposure. Methods: Thirty Chinese Han male basketball players (median age, 22.0 years [IQR, 21.0–27.75]) entered a randomized, double-blind, placebo-controlled crossover trial; 17 reported no caffeine exposure and 13 reported exposure during the preceding 4 weeks. After caffeine (CAF; 3 mg·kg⁻¹) or placebo (PLA), a 60-min absorption period, and warm-up, participants performed a post-supplement, pre-conditioning CMJ followed by 3 × 5 DJs. CMJ was assessed at 15 s, 3, 6, 9, and 12 min. The primary outcome was the Condition × Time effect on CMJ. All 30 randomized participants contributed data; three did not complete Period 2 because readiness criteria were not met, but Period 1 data were retained (57 participant-period observations). Results: CMJ varied across time (p < 0.001), but Condition × Time was not significant (p = 0.305). CAF–PLA differences at 15 s, 3, 6, 9, and 12 min were 0.89 cm (95% CI, −0.11 to 1.88), 0.39 (−0.61 to 1.38), 0.21 (−0.79 to 1.21), 0.84 (−0.15 to 1.84), and 0.71 (−0.29 to 1.71), respectively (all Holm-adjusted p ≥ 0.399). Habitual caffeine exposure showed no global moderation continuously (p = 0.158) or categorically (p = 0.116). An isolated 9-min contrast at zero reported exposure favored CAF by 1.83 cm (95% CI, 0.74–2.92; Holm-adjusted p = 0.031) but was exploratory. RPE showed no Condition × Time interaction (p = 0.253); at 15 s, CAF–PLA was −0.60 points (95% CI, −1.09 to −0.12; Holm-adjusted p = 0.088). Conclusions: This study did not obtain clear evidence that 3 mg·kg⁻¹ caffeine provided additional CMJ improvement following this specific RSI-derived individualized DJ protocol. Habitual caffeine exposure did not systematically moderate the temporal response; the isolated signal was exploratory. Full article

The 1973 M_S7.6 Luhuo earthquake is the most representative strike-slip event in the Xianshuihe fault zone, yet published source models differ markedly, and the mechanism that arrested its rupture near Renda remains poorly understood. Using spectral-element dynamic rupture simulations with a nonplanar fault geometry, three-dimensional velocity model, and depth-dependent initial stress field, we test whether fault geometry or inherited stress heterogeneity controlled the termination. Our results show that N75° W is the optimal maximum principal stress orientation, yielding surface offsets, a bilateral rupture mode, and an intensity pattern consistent with observations. Fault geometry alone cannot explain the termination: continuous and dipping faults rupture completely, and a 1 km stepover at Renda blocks the rupture jump yet leaves minor slip on the secondary fault. Introducing the 1923 Daofu earthquake stress change as a low-stress barrier instead terminates rupture near Renda, and simulated magnitude, offsets, and intensity then agree with observations. A compliant damage zone raises coseismic slip and lowers the moment magnitude while contracting the meizoseismal zone, whereas topography barely alters the rupture but appreciably modulates ground motion. These findings demonstrate that inherited stress heterogeneity, rather than fault geometry, can be the primary control on rupture arrest and can inform seismic hazard assessment for the Sichuan-Yunnan fault system. Full article

Background/Objectives: Rapid changes, jumping, and high-intensity movements are common among football players and are vulnerable to ankle sprains and functional ankle instability (FAI). This study aimed to determine the prevalence of FAI and assess the correlation with related factors among male football players in southwestern Saudi Arabia. Methods: A cross-sectional observational study was conducted among 364 male football players aged ≥18 years in southwestern Saudi Arabia. Participants completed the Arabic version of the Identification of Functional Ankle Instability (Ar-IdFAI) questionnaire. Descriptive statistics were used to estimate prevalence. Differences in Ar-IdFAI scores across playing positions were examined using analysis of covariance (ANCOVA), adjusted for age, body mass index (BMI), playing experience, and weekly training hours. Multivariable binary logistic regression was used to examine factors associated with IdFAI-defined probable FAI. Results: IdFAI-defined probable FAI was identified in 47.8% (174/364) of participants (95% CI: 42.7–52.9%). After adjustment for age, BMI, playing experience, and weekly training hours, playing position was not significantly associated with Ar-IdFAI score (ANCOVA, F(3,356) = 2.106, p = 0.099). In the exploratory participant-level logistic regression analysis, greater playing experience was associated with lower odds of Ar-IdFAI-defined probable FAI (OR = 0.93, 95% CI: 0.88–0.98, p = 0.018), whereas playing position, age, BMI, weekly training hours, and dominant limb were not statistically associated with the outcome. Conclusions: FAI is prevalent among all male field-position footballers, regardless of their position. Playing position was not independently associated with instability, whereas greater playing experience demonstrated an inverse association with functional ankle instability. Findings highlight the necessity for preventive and rehabilitation approaches targeting all players regardless of position. Full article

We construct a resolvent operator framework for multi-term fractional Cauchy problems with damping in Banach spaces, where the fractional derivatives are of the Caputo–Fabrizio (CF) type. Using Laplace transform techniques, we obtain necessary and sufficient conditions for the generation of the associated resolvent families and establish the existence and uniqueness of generalized solutions. Since the CF derivative vanishes at the origin, the classical initial condition $u\left(0^{+}\right)=x$ is unattainable when $Ax\ne 0$; the resolvent constructed here gives rise to a generalized solution with $u\left(0^{+}\right)=T\left(0\right)x\ne x$. We make this initial jump precise, show that it vanishes at the rate $O(1-\alpha )$ as $\alpha \to 1^{-}$, and indicate when it is physically meaningful. The abstract theory is applied to a biharmonic plate model with structural damping, producing explicit analytical solutions and a quantitative bound on the jump. Full article

This study presents a full-scale steady CFD methodology for evaluating flow quality in a large-scale low-speed wind tunnel (8 m × 6 m test section, 130 m/s). The tunnel geometry is resolved at 1:1 scale, the damping screens and honeycomb are modeled as porous media, and results are validated against wind tunnel test data and the GJB 1179A-2012 acceptance criteria. The baseline configuration reproduces the axial static pressure gradient within the acceptance criterion but substantially overpredicts turbulence intensity, dynamic pressure coefficient, and both velocity direction deviation angles. Damping screens, modeled as porous jumps, provide the dominant correction, bringing all metrics within the acceptance limits. Adding honeycomb yields incremental improvement: porous zone modeling preserves or improves all metrics, whereas a porous jump representation pushes velocity direction deviations beyond the limit. Between RNG k-ε and SST k-ω, only turbulence intensity is closure-dependent, with RNG k-ε closer to experiment. At Ma ≈ 0.38, compressibility does not alter the flow quality assessment, confirming that incompressible assumption is sufficient. By replacing costly physical trials with a validated CFD workflow, these findings provide a practical, resource-efficient reference for the CFD-based evaluation, design, and retrofit of wind tunnel infrastructure that underpins renewable-energy and energy-efficiency research. Full article

Mobile health (mHealth) apps increasingly capture the physiological, biomechanical, and psychological variables involved in sport training, but the evidence remains fragmented across single-domain reviews, leaving practitioners without a consolidated basis for selecting and deploying these tools across the training process. This scoping review aimed to identify and characterize research on mHealth apps in sport training, focusing on their performance testing, training load and recovery monitoring, technical and skill development, injury screening and prevention, and athlete self-management. It also synthesized evidence regarding their applications, intended purposes, technical characteristics, and the evidence supporting their effectiveness. Five databases (PubMed, Scopus, Web of Science, SPORTDiscus, Embase) were searched from inception to July 2026 for journal articles reporting original empirical data on app research on the sport training process in athletes. Studies involving only the promotion of physical activity or lacking human-subject testing, including commercially available apps without supporting research on their effectiveness, were excluded. Findings were synthesized narratively, and methodological quality was appraised with the Mixed Methods Appraisal Tool. Of 9476 records identified, 111 studies met the inclusion criteria and were inductively classified into ten application categories: sport skill training (n = 26), performance measurement (n = 20), vertical jump measurement (n = 18), self-reported monitoring (n = 12), physiological measurement (n = 12), musculoskeletal screening (n = 10), psychological intervention (n = 5), nutrition (n = 3), anthropometric and maturation screening (n = 3), and tactical and match analysis (n = 2). Most apps relied on built-in smartphone sensors or no sensing at all and used manual or deterministic computation; processing location went unreported in 74.8% of studies, which reflects a reporting gap rather than an architectural profile of the field, and reported that AI or machine learning labels did not track with actual method disclosure. Validation and reliability designs dominated the evidence base (52%), while randomized or controlled effectiveness trials were rare (10%). Apps generally showed good relative validity but limited absolute accuracy against criterion instruments, and wherever apps were deployed longitudinally, adherence rather than accuracy determined their real-world value. mHealth apps now support nearly every stage of sport training and can substitute for laboratory instruments in select, validated use cases, including video-based sprint and jump timing and chest-strap-paired heart-rate variability monitoring. However, the field remains organized around demonstrating measurement accuracy rather than showing that app-guided decisions improve athlete outcomes. A successful pathway for mHealth app development should progress from technical validity, through measurement reliability and responsiveness, to decision rules, and then to practitioner adoption by coaches and athletes, ultimately yielding better athlete outcomes. Full article

Background: While the biomechanical, physiological, and nutritional determinants of table tennis (TT) performance have already been summarized, a dedicated synthesis of players’ anthropometric and motor characteristics is still lacking. This review aimed to synthesize current evidence across different ages, genders, and competitive levels. Methods: BASE, PubMed, ScienceDirect, Scopus, Semantic Scholar, and Web of Science databases were searched for study selection. Cross-sectional studies investigating the anthropometric and motor characteristics of healthy TT players aged 7–40 years were considered eligible. Results: Thirty-one studies were included. Eighteen studies focused on motor characteristics, seven on anthropometric traits, and six examined both. Conclusions: Adult male TT players predominantly exhibit an endomorph–ectomorph profile with greater lean mass, whereas females show an endomorph–ectomorph somatotype. Moreover, higher-ranked athletes generally display greater lean mass. Compared to specific strength-based sports athletes, TT players tend to have lower limb circumferences and lower lean and muscle mass, while showing higher body fat than specific speed- and agility-based sports. Higher-level players tend to demonstrate faster reaction and movement times, as well as superior change-of-direction abilities. Compared to other racket sports, they tend to exhibit superior coincidence-anticipation timing under high stimulus velocities and distinctive motor coordination. In terms of strength, TT players show proficiency in horizontal jumps and dynamic back strength, despite lower vertical explosive power. The identified characteristics provide a descriptive profile of table tennis players and may inform future longitudinal research investigating their potential relevance for talent identification and development. Full article

Background: Anterior cruciate ligament reconstruction (ACLR) is the standard of care for ACL injuries, and graft choice may influence the recovery of function assessed with vertical jump tests. Objective: To evaluate the effect of graft type on vertical jump performance in adults after ACLR and to synthesise the differences between grafts. Material and Methods: This systematic review was conducted in accordance with the PRISMA 2020 and SWiM guidelines. The following databases were searched: Scopus, Web of Science, PubMed, MEDLINE and SPORTDiscus (EBSCOhost), up to 31 January 2026. Studies with an unambiguously defined graft type and objective jump tests (CMJ, SL CMJ/SL VJ, DVJ/DJ, SJ) were included. Risk of bias was assessed using the RoB 2, ROBINS-I, JBI and MINORS tools, and the certainty of evidence using the GRADE approach. Because of substantial clinical and methodological heterogeneity, a structured narrative synthesis was performed in accordance with the SWiM guidelines; no pooled analysis was undertaken. Results: Forty-seven studies (>3400 participants) were included. BPTB was associated with greater eccentric-phase asymmetry in the bilateral CMJ in the early/intermediate phase compared with HT, with equalisation after 9–12 months. QT provided jump height comparable to HT but a more favourable dynamic valgus profile. Autograft and allograft did not differ in jump performance. Deficits followed a biphasic course: normalisation of symmetry after approximately 2 years, with reduced height/power for up to 5 years. Conclusions: Forty-two of the studies (89.4%) were non-randomised, and the certainty of evidence was low for one clinical question and very low for all others. Studies comparing BPTB with HT showed an association suggesting greater eccentric-phase asymmetry in the bilateral CMJ in the early and intermediate phase after BPTB, but findings were inconsistent and two studies reported no difference. Evidence suggesting that these differences equalise after 9–12 months derives from between-study comparisons. Jump height did not differ between QT and HT; a single study of 26 patients reported smaller dynamic valgus after QT. Autograft and allograft did not differ in vertical jump performance. Registration: This review was registered in the PROSPERO database and is available under the number CRD420261386307. Full article

The extended Kalman filter (EKF) remains one of the most widely used tools for state estimation, tracking, forecasting, and data assimilation in nonlinear stochastic dynamical systems. This paper does not propose a replacement for the EKF or a modification of the filter itself. Instead, it investigates how the classical EKF may fail when used as a default estimation tool in a unified but practically interpretable nonlinear tracking problem. A stochastic moving-target observation model with angular and range measurements from two identical independent radar channels co-located at the origin of the coordinate system is used as the test environment. To the standard EKF scheme, we add only the technique of linear pseudomeasurements: the EKF is kept in its classical recursive form, and only the observation representation is changed, while the filtering algorithm itself remains unchanged. Within this framework, several systematic model modifications are considered: inaccurate state initialization, absence of prior information about the mean motion parameter, jump-like changes of motion parameters, and incorrect specification of observation-noise characteristics. The experiments show that EKF instability is not limited to explicit divergence. It may also appear as hidden degradation of estimation quality, coordinate-selective failure, physically counterintuitive accuracy behavior, and cases in which the filter remains formally bounded but performs worse than a simple direct estimate based on current measurements. In several experiments, unstable behavior becomes visible only when the Monte Carlo sample size is increased. The results provide a classification of qualitatively different EKF failure modes and support practical diagnostic criteria for testing EKF applicability in nonlinear observation models. Full article

Interlimb asymmetry is relevant for monitoring neuromuscular function in athletes, but evidence on futsal-specific preventive strategies in youth players remains limited. This study examined the effects of a 20-week Futsal Preventive Program (FPP) on functional interlimb asymmetry and explored injury risk during a 9-month surveillance period. Sixty-seven youth male outfield players completed pre- and post-intervention assessments (control group, n = 36; experimental group, n = 31), while 79 players were included in the injury-risk analysis (control group, n = 41; experimental group, n = 38). The experimental group performed a 15 min neuromuscular warm-up weekly, while the control group continued its usual warm-up. Asymmetry was assessed using countermovement jump (CMJ), horizontal jump (HJ), and 505 change-of-direction (COD 505) tests. The program produced a task-specific reduction in COD 505 asymmetry compared with the control group (cluster-adjusted difference = −1.27 percentage points; 95% CI: −2.00 to −0.53; Bonferroni-adjusted p = 0.03), whereas no significant intervention effects were observed for CMJ or HJ asymmetry. Across the full 9-month surveillance period, the crude cumulative injury-risk estimate was RR = 0.92 (95% CI: 0.59–1.45), with the confidence interval including the null value. These findings support a task-specific effect of the FPP on COD 505 asymmetry, without evidence of corresponding effects on CMJ or HJ asymmetry. Injury findings were descriptive and hypothesis-generating and do not establish preventive efficacy. Further studies with a larger number of randomized teams, greater weekly intervention exposure, and individual training and match exposure monitoring are warranted to clarify potential effects on injury incidence. Full article

Background: Exercise-induced fatigue (EIF) and exercise-induced muscle damage (EIMD) impair neuromuscular performance and delay post-exercise recovery. However, human evidence regarding the structural and functional recovery kinetics following Lactiplantibacillus plantarum GKK1 supplementation remains limited. Objective: This randomized, double-blind, placebo-controlled trial investigated whether 4 weeks of L. plantarum GKK1 supplementation improves functional recovery and modulates biochemical responses after an EIMD protocol in healthy men. Methods: Forty-eight healthy men with no regular exercise habits were randomly assigned to receive either placebo (n = 24) or L. plantarum GKK1 (two capsules daily, totaling 1.0 × 10¹¹ CFU; n = 24) for 28 consecutive days. The trial was registered at ClinicalTrials.gov (NCT06893549). After supplementation, participants completed 100 maximal plyometric jumps. Countermovement jump (CMJ), isometric mid-thigh pull (IMTP), and Wingate anaerobic performance were assessed before EIMD and at 3, 24, and 48 h post-EIMD. Blood biomarkers of muscle damage, inflammation, oxidative stress, endocrine response, and sympathoadrenal activity were analyzed, and urinary 3-methylhistidine and creatinine were measured. Results: Compared with placebo, GKK1 supplementation was associated with smaller post-exercise decrements in the CMJ rate of force development, relative peak force, jump height, IMTP relative peak force and peak RFD, and Wingate anaerobic performance (p < 0.05). GKK1 also attenuated post-exercise increases in CK, myoglobin, hs-CRP, and TBARS, and was associated with more favorable testosterone, HGH, catecholamine, and dopamine responses. At 24 h post-EIMD, urinary 3-methylhistidine and the 3-methylhistidine/urinary creatinine ratio were lower in the GKK1 group than in the placebo group. No adverse changes were observed in clinical safety biomarkers. Conclusion: These findings suggest that GKK1 may be a safe nutritional strategy to facilitate functional recovery, attenuate secondary inflammatory responses and modulate urinary markers associated with muscle breakdown following muscle-damaging exercise in healthy young men. Full article

Positioning jumps are a primary cause of trajectory discontinuities in urban canyon environments, severely hindering the widespread adoption of autonomous vehicles. This paper proposes a CNN-GRU fusion-based method for correcting such positioning jumps. A complete 15-dimensional error-state extended Kalman filter (EKF) framework is established to analyze the jump generation mechanisms from three perspectives—pseudorange distortion, inertial drift, and filter gain divergence—thereby justifying the use of inertial measurement unit (IMU) time-series data for anomaly prediction. An end-to-end mapping model is further constructed, in which a one-dimensional convolutional neural network (CNN) extracts cross-channel spatial features from multi-axis inertial data, while a gated recurrent unit (GRU) captures long-term temporal error evolution. A hysteresis navigation quality factor and a piecewise Huber loss function are incorporated to enable hierarchical adaptive optimization. Experimental results demonstrate that the proposed method reduces the positioning root mean square error (RMSE) from 1.24 m to 0.70 m, achieves a jump suppression rate of 43.5%, and maintains a single-frame inference latency of 11.8 ms, meeting the real-time requirements for future autonomous driving localization. Full article

Leg-spring hysteresis, the mechanical energy dissipated within the force–length loop during ground contact, is a whole-limb, indirect indicator of stretch-shortening cycle (SSC) function. Whether international-level track-and-field and club-level multi-sport athletes differ in hysteresis responses to drop height, and whether hysteresis is associated with jump height, remains unclear. Here, 40 athletes (15 international-level, 25 club-level) performed bilateral (BLJ), dominant-leg (DOM), and non-dominant-leg (NDOM) drop jumps from 0.26 to 0.42 m. Hysteresis and jump height were computed from three-dimensional kinematics (500 Hz) and ground reaction forces. Group × drop-height interactions were significant for hysteresis in all conditions (partial eta-squared, η²p = 0.647, 0.507, 0.466; p < 0.001): international-level athletes became increasingly negative (net active energy contribution) at 0.42 m, whereas club-level athletes became positive (net dissipation). Between-group differences at 0.42 m were large (Cohen’s d = −1.73, DOM; −1.95, NDOM); jump height was also higher in international-level athletes (d = 1.14–1.77). Pooled, hysteresis was associated with jump height (coefficient of determination, R² = 0.44–0.60), although caliber differences inflate this estimate, and within-group associations were weaker. Hysteresis discriminated reactive-jumping capacity beyond jump height alone; because competitive level was confounded with sport discipline and sex, these differences should not be attributed to caliber per se. Full article

The filling-and-emptying valve and downstream shaft are crucial components of navigation-lock systems. Under insufficient downstream submergence, air can be drawn through the shaft and trapped in the post-valve culvert, altering the flow structure and compromising hydraulic stability. A three-dimensional Reynolds-averaged Navier–Stokes/volume-of-fluid model was developed to investigate shaft aeration and entrapped-air-pocket evolution under varying inlet velocities and downstream-submergence depths. The aeration process comprises three stages: jet establishment, air-pocket formation, and air-pocket breakup and reorganization. Downstream-submergence depth determines whether a continuous air-intake pathway forms, whereas inlet velocity primarily controls aeration intensity and air-pocket persistence once the pathway is established. With decreasing submergence depth, the flow transitions successively from a water-sealed regime to a transition regime, a stable entrapped-air-pocket regime, and a strongly unsteady hydraulic-jump-like regime. For the present geometry and fixed valve opening, the transition from transient to sustained shaft aeration is identified within the downstream-submergence interval of h_w = 2–5 m. Combined analyses of the air-pocket volume per unit width, pressure response, vortex structures, and shear-layer characteristics indicate that enhanced jet-induced shear is closely associated with shaft aeration and air entrapment, while pressure fluctuations are closely coupled with air-pocket formation, persistence, breakup, and reorganization. Full article

The universal operator-growth hypothesis (OGH) states that, in a closed chaotic system, the Lanczos coefficients grow linearly, $b_n\simeq \alpha n$. We ask how this structure is modified when the system is coupled to a Markovian environment, so that the generator becomes non-Hermitian. Applying the Arnoldi recursion to the vectorized Lindbladian in the infinite-temperature Wightman inner product, we organize the resulting pair of growth rates ${\alpha }_{\mathbb{C}}\equiv {\alpha }_R+i{\alpha }_I$—defined as effective slopes of the sub-diagonal and diagonal Arnoldi coefficients over a pre-registered fit window—around two statements whose logical status we delimit precisely. First, whenever the dissipator acts as $\mathcal{D}=-2\gamma \widehat{G}$ with $\widehat{G}$, a Hermitian grading (all dephasing-type baths), the diagonal obeys the identity $\mathrm{Re}{a}_n=-2\gamma {⟨\widehat{G}⟩}_n$: the imaginary rate measures how fast the growing operator accumulates weight in the dissipation channels. Second, we prove a conditional parity theorem: if the Hamiltonian, jump operators, and seeds can be made simultaneously real in some basis (an antiunitary condition), then $b_n$ is even, and $\mathrm{Re}{a}_n$ is odd in $\gamma$ exactly, so ${\alpha }_R$ is renormalized only at $O\left({\gamma }^2\right)$, and ${\alpha }_I=2{\kappa }_0\gamma$ follows from closed-system data alone. We exhibit a one-qubit Lindbladian that satisfies the often-assumed generator symmetry ${\mathcal{G}}^{†}\left(\gamma \right)=-\mathcal{G}(-\gamma )$ yet violates parity ($b_1=|1-\gamma |$), showing that the extra condition is essential; all models studied here satisfy it bit-exactly. For large-q SYK, these ingredients predict ${\alpha }_{\mathbb{C}}=\mathcal{J}-2i(q-2)\gamma$, whose imaginary part is fixed solely by the interaction range; the first ladder step is exact, and the multi-step increments approach $q-2$ with system size ($1.92\pm 0.04$ at $N=12$, $q=4$). Under a common fit protocol, the closed-system rates saturate by $N=10$ (${\alpha }_R\left(0\right)\to 0.437$, $2{\kappa }_0\to 0.224$). The imaginary rate is not an independent observable at leading order—its content is its sign, which resolves how the growing operator meets its environment (opposite for spin chains and SYK). Full article