Adaptive Bayesian variable clustering via structural learning of breast cancer data.

The clustering of proteins is of interest in cancer cell biology. This article proposes a hierarchical Bayesian model for protein (variable) clustering hinging on correlation structure. Starting from a multivariate normal likelihood, we enforce the clustering through prior modeling using angle-based unconstrained reparameterization of correlations and assume a truncated Poisson distribution (to penalize a large number of clusters) as prior on the number of clusters. The posterior distributions of the parameters are not in explicit form and we use a reversible jump Markov chain Monte Carlo based technique is used to simulate the parameters from the posteriors. The end products of the proposed method are estimated cluster configuration of the proteins (variables) along with the number of clusters. The Bayesian method is flexible enough to cluster the proteins as well as estimate the number of clusters. The performance of the proposed method has been substantiated with extensive simulation studies and one protein expression data with a hereditary disposition in breast cancer where the proteins are coming from different pathways.

Launching a Drop via Interplay of Buoyancy and Stick-Jump Dissolution.

According to Archimedes' principle, a submerged object with a density lower than that of aqueous acid solution is more buoyant than a smaller one. In this work, a remarkable phenomenon is reported wherein a dissolving drop on a substrate rises in the water only after it has diminished to a much smaller size, though the buoyancy is smaller. The drop consisting of a polymer solution reacts with the acid in the surrounding, yielding a water-soluble product. During drop dissolution, water-rich microdroplets form within the drop, merging with the external aqueous phase along the drop-substrate boundary. Two key elements determine the drop rise dynamics. The first is the stick-jump behavior during drop dissolution. The second is that buoyancy exerts a strong enough force on the drop at an Archimedean number greater than 1, while the stick-jump behavior is ongoing. The time of the drop rise is controlled by the initial size and the reaction rate of the drop. This novel mechanism for programmable drop rise may be beneficial for many future applications, such as microfluidics, microrobotics, and device engineering where the spontaneous drop detachment may be utilized to trigger a cascade of events in a dense medium.

Influence of an inspiratory muscle fatigue protocol on healthy youths on respiratory muscle strength, vertical jump performance and muscle oxygen saturation: a randomized controlled trial.

BACKGROUND: Inspiratory muscle fatigue has been shown to have effects on limbs blood flow and physical performance. This study aimed to evaluate the influence of an inspiratory muscle fatigue protocol on respiratory muscle strength, vertical jump performance and muscle oxygen saturation in healthy youths. METHODS: A randomized and double-blinded controlled clinical trial, was conducted. Twenty-four participants aged 18-45 years, non-smokers and engaged in sports activity at least three times a week for a minimum of one year were enrolled in this investigation. Participants were randomly assigned to three groups: Inspiratory Muscle Fatigue (IMFG), Activation, and Control. Measurements of vertical jump, diaphragmatic ultrasound, muscle oxygen saturation, and maximum inspiratory pressure were taken at two stages: before the intervention (T1) and immediately after treatment (T2). RESULTS: The IMFG showed lower scores in muscle oxygen saturation and cardiorespiratory variables after undergoing the diaphragmatic fatigue intervention compared to the activation and control groups (p < 0.05). For the vertical jump variables, intragroup differences were found (p < 0.01), but no differences were shown between the three groups (p > 0.05). CONCLUSIONS: Inspiratory muscle fatigue appears to negatively impact vertical jump performance, muscle oxygen saturation and inspiratory muscle strength in healthy youths. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT06271876. Date of registration 02/21/2024. https://clinicaltrials.gov/study/NCT06271876 .

Pseudomonas syringae coffee blight is associated with the horizontal transfer of plasmid-encoded type III effectors.

The emergence of new pathogens is an ongoing threat to human health and agriculture. While zoonotic spillovers received considerable attention, the emergence of crop diseases is less well studied. Here, we identify genomic factors associated with the emergence of Pseudomonas syringae bacterial blight of coffee. Fifty-three P. syringae strains from diseased Brazilian coffee plants were sequenced. Comparative and evolutionary analyses were used to identify loci associated with coffee blight. Growth and symptomology assays were performed to validate the findings. Coffee isolates clustered in three lineages, including primary phylogroups PG3 and PG4, and secondary phylogroup PG11. Genome-wide association study of the primary PG strains identified 37 loci, including five effectors, most of which were encoded on a plasmid unique to the PG3 and PG4 coffee strains. Evolutionary analyses support the emergence of coffee blight in PG4 when the coffee-associated plasmid and associated effectors derived from a divergent plasmid carried by strains associated with other hosts. This plasmid was only recently transferred into PG3. Natural diversity and CRISPR-Cas9 plasmid curing were used to show that strains with the coffee-associated plasmid grow to higher densities and cause more severe disease symptoms in coffee. This work identifies possible evolutionary mechanisms underlying the emergence of a new lineage of coffee pathogens.

A Wright-Fisher graph model and the impact of directional selection on genetic variation.

We introduce a multi-allele Wright-Fisher model with mutation and selection such that allele frequencies at a single locus are traced by the path of a hybrid jump-diffusion process. The state space of the process is given by the vertices and edges of a topological graph, i.e. edges are unit intervals. Vertices represent monomorphic population states and positions on the edges mark the biallelic proportions of ancestral and derived alleles during polymorphic segments. In this setting, mutations can only occur at monomorphic loci. We derive the stationary distribution in mutation-selection-drift equilibrium and obtain the expected allele frequency spectrum under large population size scaling. For the extended model with multiple independent loci we derive rigorous upper bounds for a wide class of associated measures of genetic variation. Within this framework we present mathematically precise arguments to conclude that the presence of directional selection reduces the magnitude of genetic variation, as constrained by the bounds for neutral evolution.

Pólya-splitting distributions as stationary solutions of multivariate birth-death processes under extended neutral theory.

Multivariate count distributions are crucial for the inference of ecological processes underpinning biodiversity. In particular, neutral theory provides useful null distributions allowing the evaluation of adaptation or natural selection. In this paper, we build a broader family of multivariate distributions: the Polya-splitting distributions. We show that they emerge naturally as stationary distributions of a multivariate birth-death process. This family of distributions is a consistent extension of non-zero sum neutral models based on a master equation approach. It allows considering both total abundance of the community and relative abundances of species. We emphasize that this family is large enough to encompass various dependence structures among species. We also introduce the strong closure under addition property that can be useful to generate nested multi-level dependence structures. Although all Pólya splitting distributions do not share this property, we provide numerous example verifying it. They include the previously known example with independent species, and also new ones with alternative dependence structures. Overall, we advocate that Polya-splitting distribution should become a part of the classic toolbox for the analysis of multivariate count data in ecology, providing alternative approaches to joint species distribution framework. Comparatively, our approach allows to model dependencies between species at the observation level, while the classical JSDM's model dependencies at the latent process strata.

Joint structure learning and causal effect estimation for categorical graphical models.

The scope of this paper is a multivariate setting involving categorical variables. Following an external manipulation of one variable, the goal is to evaluate the causal effect on an outcome of interest. A typical scenario involves a system of variables representing lifestyle, physical and mental features, symptoms, and risk factors, with the outcome being the presence or absence of a disease. These variables are interconnected in complex ways, allowing the effect of an intervention to propagate through multiple paths. A distinctive feature of our approach is the estimation of causal effects while accounting for uncertainty in both the dependence structure, which we represent through a directed acyclic graph (DAG), and the DAG-model parameters. Specifically, we propose a Markov chain Monte Carlo algorithm that targets the joint posterior over DAGs and parameters, based on an efficient reversible-jump proposal scheme. We validate our method through extensive simulation studies and demonstrate that it outperforms current state-of-the-art procedures in terms of estimation accuracy. Finally, we apply our methodology to analyze a dataset on depression and anxiety in undergraduate students.

A Bayesian survival treed hazards model using latent Gaussian processes.

Survival models are used to analyze time-to-event data in a variety of disciplines. Proportional hazard models provide interpretable parameter estimates, but proportional hazard assumptions are not always appropriate. Non-parametric models are more flexible but often lack a clear inferential framework. We propose a Bayesian treed hazards partition model that is both flexible and inferential. Inference is obtained through the posterior tree structure and flexibility is preserved by modeling the log-hazard function in each partition using a latent Gaussian process. An efficient reversible jump Markov chain Monte Carlo algorithm is accomplished by marginalizing the parameters in each partition element via a Laplace approximation. Consistency properties for the estimator are established. The method can be used to help determine subgroups as well as prognostic and/or predictive biomarkers in time-to-event data. The method is compared with some existing methods on simulated data and a liver cirrhosis dataset.

Role of proprioception in corrective visually-guided movements: larger movement errors in both arms of a deafferented individual compared to control participants.

Proprioception plays an important role in both feedforward and feedback processes underlying movement control. This has been shown with individuals who suffered a profound proprioceptive loss and use vision to partially compensate for the sensory loss. The purpose of this study was to specifically examine the role of proprioception in feedback motor responses to visual perturbations by examining voluntary arm movements in an individual with a rare case of selective peripheral deafferentation (GL). We compared her left and right hand movements with those of age-matched female control participants (70.0 years ± 0.2 SEM) during a reaching task. Participants were asked to move their unseen hand, represented by a cursor on the screen, quickly and accurately to reach a visual target. A visual perturbation could be pseudorandomly applied, at movement onset, to either the target position (target jump) or the cursor position (cursor jump). Results showed that despite the continuous visual feedback that was provided, GL produced larger errors in final position accuracy compared to control participants, with her left nondominant hand being more erroneous after a cursor jump. We also found that the proprioceptively-deafferented individual produced less spatially efficient movements than the control group. Overall, these results provide evidence of a heavier reliance on proprioceptive feedback for movements of the nondominant hand relative to the dominant hand, supporting the view of a lateralization of the feedback processes underlying motor control.

Effects of far-infrared radiation lamp therapy on recovery from a simulated soccer-match in elite female soccer players.

We investigated the effects of far-infrared radiation (FIR) lamp therapy on changes in muscle damage and performance parameters following six sets of 15-min Loughborough intermittent shuttle test (LIST), a simulated soccer match. Twenty-four elite female soccer players (20-24 y) were assigned into FIR or sham treatment group (n = 12/group). The participants received a 60-min FIR or sham treatment (30 min per muscle) over knee extensors (KE) and flexors (KF) at 2, 25, 49, 73, and 97 h post-LIST. Maximal voluntary isometric contraction (MVC) torque and muscle soreness of the KE and KF, plasma creatine kinase (CK) activity as muscle damage markers, and several performance parameters including countermovement jump (CMJ) and Yo-Yo intermittent recovery test level 1 (YYIR1) were measured before and 1, 24, 48, 72, 96, and 120 h post-LIST. Changes in the measures were compared between groups by a mixed-design two-way ANOVA. The running distance covered during LIST and changes in the measures at 1-h post-LIST (before the treatment) were similar (p = 0.118-0.371) between groups. Changes in muscle damage markers at 24-120 h post-LIST were smaller (p < 0.05, η2 = 0.208-0.467) for the FIR (e.g., MVC-KE torque decrease at 48-h post-LIST: -1 ± 2%, peak KE soreness: 16 ± 10 mm, peak CK: 172 ± 42 IU/L) than sham group (-11 ± 9%, 33 ± 7 mm, 466 ± 220 IU/L, respectively). Performance parameters recovered faster (p < 0.05, η2 = 0.142-0.308) to baseline for the FIR (e.g., decreases at 48-h post-LIST; CMJ: 0 ± 1%, YYIR1: 0 ± 1%) than sham group (-6 ± 2%, -9 ± 6%, respectively). These results suggest that the FIR lamp therapy was effective for enhancing recovery from a soccer match.

Respiratory patterns and physical fitness in healthy adults: a cross-sectional study.

BACKGROUND: The altered respiratory patterns have a significant impact on our health. However, the links between respiration patterns during spontaneous breathing and physical fitness remain unknown. Therefore, we sought to examine how the respiratory pattern during spontaneous breathing interacts with physical fitness. METHODS: A total of 610 participants (aged 20-59 years) were enrolled; 163 men (age = 41 ± 11) and 401 women (age = 42 ± 9) were included for analysis. The parameters of the respiration pattern were respiration rate (RR) and inhalation/exhalation (I/E) ratio. The physical fitness components were body size, visuomotor reaction time, balance, flexibility, hand grip strength, back extension strength, vertical jump height, number of push-ups, number of sit-ups, and the maximum rate of oxygen consumption. The data were analyzed separately for two gender groups. Participants within each gender group were further divided into two age categories (young: 20-39 years, middle-aged: 40-59 years) for the analysis, and both correlational and comparative tests were used to solidify the results. RESULTS: Neither RRs nor the I/E ratios were substantially correlated with physical fitness in women. In addition, the I/E ratios showed no significant correlation with physical fitness in young men, while the results from correlational and comparative tests were inconsistent in middle-aged men. Consistently, men with lower RRs exhibited significantly shorter visuomotor reaction times in two age groups, and demonstrated significantly higher vertical jump heights in the middle-aged group. CONCLUSIONS: In women, respiratory patterns were not correlated with physical fitness. The relationship between middle-aged men's I/E ratios and their physical fitness warrants further investigation. Men with lower RRs may have better visual-motor coordination and/or sustained attention, while middle-aged men with lower RRs may also have greater leg explosive power and neuromuscular coordination, which should be considered for physical assessment and health improvement.

Test-retest reliability of lower limb muscle strength, jump and sprint performance tests in elite female team handball players.

PURPOSE: This study aimed to assess the reliability of lower limb muscle function (knee extensor/flexor peak torque, rate of torque development (RTD), impulse, and countermovement jump (CMJ) performance) and sprint performance (acceleration capacity). METHODS: CMJ performance was evaluated on a force plate. MVIC, RTD and impulse variables were investigated using a portable isometric dynamometer and sprint performance was assessed with dual-beam photocells in elite female athletes. RESULTS: CMJ test variables maximal vertical jump height, peak and mean power, concentric work, and body center of mass displacement demonstrated good-to-excellent test-retest correlations between Test 1 and Test 2 (ICC ≥ 0.70, CWw-s = 3.4-11.0%). Peak MVIC torque for the knee extensors and flexors demonstrated excellent test-retest correlations (both ICC = 0.84) along with CVw-s values of 6.8 and 6.0%, respectively. Late-phase (0-100 ms, 0-200 ms) RTD for the knee flexors demonstrated excellent test-retest correlations (ICC = 0.89-0.91, CVw-s = 4.8-8.5%). Sprint times at 10- and 20-m demonstrated excellent test-retest reproducibility (ICC = 0.83 and ICC = 0.90, respectively) with CVw-s values of 1.9 and 1.5%. For 5-m sprint times, test-retest reproducibility was good (ICC = 0.71) with CVw-s of 2.8%. Sprint testing performed while dribbling a handball improved (p < 0.05) from test to retest at 5-, 10- and 20-m. CONCLUSION: In conclusion, the force plate, the mobile isometric dynamometer, and dual-beam photocells provide reproducible tools for field-based testing of countermovement jump performance, knee extensor and flexor strength and sprint performance.

Impact of curcumin supplementation on exercise performance and muscle damage after a soccer match: a double-blind placebo-controlled cross-over study.

PURPOSE: Curcumin ingestion can mitigate muscle damage, soreness, and inflammation following a laboratory-based eccentric exercise. Similar effects were observed in recent field-based studies wherein responses were evaluated after a soccer match. However, various potential confounding factors, such as matching opponent skill levels and daily training conditions, may have influenced the outcomes. In the present study, we investigated whether curcumin intake ameliorates changes in muscle damage markers following a soccer match while controlling for the potential confounding factors. METHODS: Fifteen collegiate athletes were tested in a randomized, double-blind, cross-over manner. They were recruited from the same college soccer team and thus followed the same daily training regimen and competition levels. Furthermore, athletes positioning during matches were counterbalanced. They consumed either 180 mg/day of curcumin or a placebo starting 1 h before the match and continuing for 2 days after a match (two 45-min plays and a 15-min half-time). Muscle soreness, jump performance (including countermovement jump and rebound jump index), and inflammatory and muscle damage markers (high-sensitive C-reactive protein, serum creatine kinase activity, and urinary N-terminal fragment of titin concentration) were evaluated before and after the match. The washout period between matches was set at 1 week. RESULTS: After the match, all markers showed similarity between the placebo and curcumin conditions (all P > 0.208). CONCLUSION: These findings indicate that ingesting 180 mg/day of curcumin may not expedite recovery from muscle damage elicited by soccer matches in collegiate soccer players.

Computational study of extrinsic factors affecting ACL strain during single-leg jump landing.

BACKGROUND: Non-contact anterior cruciate ligament (ACL) injuries are a major concern in sport-related activities due to dynamic knee movements. There is a paucity of finite element (FE) studies that have accurately replicated the knee geometry, kinematics, and muscle forces during dynamic activities. The objective of this study was to develop and validate a knee FE model and use it to quantify the relationships between sagittal plane knee kinematics, kinetics and the resulting ACL strain. METHODS: 3D images of a cadaver knee specimen were segmented (bones, cartilage, and meniscus) and meshed to develop the FE model. Knee ligament insertion sites were defined in the FE model via experimental digitization of the specimen's ligaments. The response of the model was validated against multiple physiological knee movements using published experimental data. Single-leg jump landing motions were then simulated on the validated model with muscle forces and kinematic inputs derived from motion capture and rigid body modelling of ten participants. RESULTS: The maximum ACL strain measured with the model during jump landing was 3.5 ± 2.2%, comparable to published experimental results. Bivariate analysis showed no significant correlation between body weight, ground reaction force and sagittal plane parameters (such as joint flexion angles, joint moments, muscle forces, and joint velocity) and ACL strain. Multivariate regression analysis showed increasing trunk, hip and ankle flexion angles decreases ACL strain (R2 = 90.04%, p < 0.05). CONCLUSIONS: Soft landing decreases ACL strain and the relationship could be presented through an empirical equation. The model and the empirical relation developed in this study could be used to better predict ACL injury risk and prevention strategies during dynamic activities.

Repetitive temporal interference stimulation improves jump performance but not the postural stability in young healthy males: a randomized controlled trial.

BACKGROUND: Temporal interference (TI) stimulation, an innovative non-invasive brain stimulation technique, has the potential to activate neurons in deep brain regions. The objective of this study was to evaluate the effects of repetitive TI stimulation targeting the lower limb motor control area (i.e., the M1 leg area) on lower limb motor function in healthy individuals, which could provide evidence for further translational application of non-invasive deep brain stimulation. METHODS: In this randomized, double-blinded, parallel-controlled trial, 46 healthy male adults were randomly divided into the TI or sham group. The TI group received 2 mA (peak-to-peak) TI stimulation targeting the M1 leg area with a 20 Hz frequency difference (2 kHz and 2.02 kHz). Stimulation parameters of the sham group were consistent with those of the TI group but the current input lasted only 1 min (30 s ramp-up and ramp-down). Both groups received stimulation twice daily for five consecutive days. The vertical jump test (countermovement jump [CMJ], squat jump [SJ], and continuous jump [CJ]) and Y-balance test were performed before and after the total intervention session. Two-way repeated measures ANOVA (group × time) was performed to evaluate the effects of TI stimulation on lower limb motor function. RESULTS: Forty participants completed all scheduled study visits. Two-way repeated measures ANOVA showed significant group × time interaction effects for CMJ height (F = 8.858, p = 0.005) and SJ height (F = 6.523, p = 0.015). The interaction effect of the average CJ height of the first 15 s was marginally significant (F = 3.550, p = 0.067). However, there was no significant interaction effect on the Y balance (p > 0.05). Further within-group comparisons showed a significant post-intervention increase in the height of the CMJ (p = 0.004), SJ (p = 0.010) and the average CJ height of the first 15 s (p = 0.004) in the TI group. CONCLUSION: Repetitive TI stimulation targeting the lower limb motor control area effectively increased vertical jump height in healthy adult males but had no significant effect on dynamic postural stability.

Decreased proprioception is associated with inferior postural control during unplanned landing in individuals with chronic ankle instability.

Poor postural control during jump landing may increase ankle sprain incidences among people with chronic ankle instability (CAI). The effects of anticipation on it and its relationship with proprioception need further examination. Fifteen participants with CAI and 15 healthy controls were recruited to perform single-leg jump landings when knowing the landing side before (planned) or after (unplanned) take-off respectively, along with a step-down proprioception test differentiating four inclination platforms (inverted 12°, 14°, 16° and 18°). Ground reaction force data (peak force, loading rate and time of stabilisation) during landings and proprioception scores were collected and analysed. The CAI group exhibited a higher loading rate (59.6 ± 7.6 vs 49.4 ± 6.7 N/kg*seconds, p = 0.011) and longer medial-lateral time to stabilisation (4.82 ± 0.69 vs 4.11 ± 0.47 seconds, p = 0.023) compared to the control group during an unplanned landing. Furthermore, the above variables were negatively correlated with the step-down proprioception score only in the unplanned condition but not in the planned condition. CAI participants had inferior medial-lateral time-to-stabilisation and loading attenuation during unplanned jump landing than healthy controls, which were associated with decreased proprioception, highlighting the importance of addressing proprioception to improve balance control during unpredictable landing situations.

The role of ball path curvature in basketball shooting accuracy.

During the shooting motion of a basketball, the path of the ball from the beginning of the lift to release follows an S-shaped trajectory. This study is the first to investigate how two distinctive features of the S-shaped ball path, the maximum curvature, κmax, and terminal curvature, σ, are associated with longitudinal accuracy. The sagittal plane ball path and curvature were found using Bezier curves for 31 professional male basketball athletes. Terminal release curvature had a very strong positive correlation to intra-individual release velocity standard deviation (r = 0.73, p < 0.001) indicating that shooters with straighter terminal ball paths had better longitudinal shooting accuracy. It was also observed that κmax coincided with the transition to the forward shooting motion and that players with higher κmax tend to have a clear two-part shooting style rather than a single fluid motion. A comparison between groups of good and poor shooters identified a mean difference in κmax of 7.9 m-1 (p < 0.001, 95% CI: 11.8-4.0 m-1) suggesting that good shooters typically have a higher κmax than poor shooters.

Improving the estimation of countermovement jump height from force plate recordings by considering the interaction between multiple procedural steps: An optimisation approach.

Force plates are used as standalone measurement systems in research and practice to evaluate metrics such as jump height. Calculating jump height involves multiple procedural steps, but previous investigations aiming to improve calculation procedures have only considered the influence of a single procedural step in isolation. The purpose of this study was to investigate if considering the interacting influence of multiple procedural steps in conjunction would impact the accuracy of jump height calculated from force plate recordings. An optimisation procedure was used to determine the combination of filter type, filter order, filter cut-off, integration start point and instant of take-off, that would minimize the root mean squared difference between force plate calculated jump height and a kinematic criterion. The best filter approach was a fifth order Butterworth filter with a 6 Hz cut-off frequency or a third order Chebyshev filter with a 5 Hz cut-off frequency. The best starting point for integration was approximately 0.25 s prior to the onset of the jump and the instant of take-off was best identified by finding the first instant that the force-time signal decreased by the magnitude of system weight. The presented optimisation technique provides an improved quantitative approach to develop standard procedures.

Discrepancy between 'contributing to' and 'sharing variance with' the effective energy for height in high jump.

In high jump, the thigh and shank rotations mainly induce the effective energy for height (Evert) by directly or indirectly (via joint work) converting horizontal-kinetic energy. Meanwhile, inter-individual differences in Evert may not only be explained by large contributors. Here we show that the Evert components due to relatively small contributor segments share variance with total Evert while those due to the two largest contributor segments do not, by analyzing high jump of 15 male jumpers (personal best: 1.90-2.31 m). The largest Evert components were from the stance-leg thigh and shank (36 ± 7%, 34 ± 7% of total Evert), but each of them did not significantly share variance with total Evert (r2 < 0.12). Meanwhile, each of the thoracic and stance-leg-foot components significantly shared variance with total increase in Evert (r2 > 0.30), despite their relatively small contributions (11 ± 2%, 4 ± 1%). The stance-leg thigh and shank components had a strongly trade-off relationship (r2 = 0.60). We reveal that large contributors to the performance variable do not directly imply by their large contribution that they explain inter-individual differences in motor performance, and vice versa. We provide an example where large contributors to the performance variable are related to individually different strategies for achieving performance rather than to performance itself.

A new approach for classification of stretch-shortening cycle: Beyond 250 ms of ground contact time.

The stretch-shortening cycle (SSC) has been classified into fast (<250 ms) and slow (>250 ms) groups based on ground contact time (GCT) threshold values. However, there are gaps in the literature on how the 250 ms threshold value was found and which variables affect it. The purpose of this study is to validate the 250 ms threshold by investigating the factors affecting this threshold. For this purpose, force-time variables during a drop jump (DJ) with a force plate and achilles tendon (AT) muscle-tendon unit mechanical properties using shear-wave elastography in 46 recreationally active men were analysed. A regression tree analysis was conducted using R studio to classify GCT with correlated variables (p < 0.05). The new GCT threshold values (GCT < 188 ms, 188 ≤ GCT < 222 ms and GCT ≥ 222 ms) were found according to the lowest root mean square error of approximation value (0.1985) at reactive strength index. Comparisons of GCT groups showed significant differences in force, time, power variables and AT length (p < 0.05). AT length is the main variable differentiating GCT groups: Short AT results in a short GCT and long AT results in a long GCT. This study reveals that SSC can be classified into three groups using new GCT threshold values, offering a new perspective for SSC assessment.