Abstract
und:Post-activation potentiation (PAPE) enhances athletic performance through brief, high-intensity reactivation and holds significant application value in competitive sports. As a core offensive and defensive technique in Sanda, the side kick demands exceptional neuromuscular coordination. However, current research on PAPE applications in specialized techniques for competitive sports remains limited. There is a lack of com- parative analysis on neuromuscular activation characteristics of the side kick in high-level Sanda athletes across different PAPE protocols, and the optimal adaptation scheme remains unidentified. Muscle coordination analysis based on non-negative matrix factorization (NMF) offers an objective perspective to elucidate the neuromuscular control mechanisms underlying this technique, thereby addressing this research gap.Methods:Eighteen high- level Sanda athletes (National Level 1 or above) participated in a randomized crossover design, sequentially undergoing three PAPE protocols—ESG, RBG, and SQG—with 10-day intervals between each intervention. Using the Noraxon wireless surface electromyography system, high-speed cameras, and the MY JUMP APP, we simultaneously collected vertical jump height data at different time points (6, 8, 10 min) post-intervention, along with elec- tromyography and kinematic data of the side kick movement 6 min post-intervention. The NMF algorithm was employed to extract muscle coordination features (activation weights, activation coefficients), and repeated measures ANOVA or Friedman tests were used to assess intergroup differences.Results:Vertical jump height was significantly higher in the ESG group than in the RBG group at 6, 8, and 10 min post-intervention (p< 0.05). At 6 min post-intervention, it was also significantly higher than in the SQG group
employed to extract muscle coordination features (activation weights, activation coefficients), and repeated measures ANOVA or Friedman tests were used to assess intergroup differences.Results:Vertical jump height was significantly higher in the ESG group than in the RBG group at 6, 8, and 10 min post-intervention (p< 0.05). At 6 min post-intervention, it was also significantly higher than in the SQG group (p< 0.05). SQG showed significantly higher ESG than RBG at 8 min post-intervention (p< 0.05), with no significant differences from the other two groups at 10 min. Regarding muscle coordina- tion, ESG and SQG exhibited significantly higher right rectus femoris activation weights than RBG (p< 0.05); ESG’s gluteus maximus and rectus femoris activation weights were significantly higher than RBG (p< 0.05), with generally longer activation durations across all synergistic modules compared to the other two groups. Although RBG’s vastus lateralis and gluteus medius activation weights were significantly higher than some groups, this did not translate into overall performance advantages.Conclusions:Different PAPE protocols exert distinct effects on vertical jump height and muscle coordination patterns during side kicks in elite Sanda athletes. The combined electrical stimulation protocol, which combines the immediate and sustained effects of PAPE, effectively enhances key muscle activation weights and prolongs coordination module activation duration. It represents the optimal solution for optimizing neuromuscular activation characteristics during sidekicks. Sensors2026,26, 296 https://doi.org/10.3390/s26010296
Sensors2026,26, 296 2 of 17 Keywords:post-activation potentiation; muscle synergy; surface electromyography; sanda athletes; neuromuscular coordination 1. Introduction Post-activation potentiation (PAPE) is a physiological mechanism that can acutely enhance motor performance by activating neuromuscular regulatory pathways through prior high-intensity, short-duration muscle contractions [1–3]. While long-term systematic training remains the fundamental basis for athletic development, PAPE offers a comple- mentary strategy to optimize performance in trained individuals. Its potential value lies in the ability to temporarily elevate muscle contraction efficiency, augment central ner- vous system drive, and improve inter-muscular coordination through precise pre-activity protocols. This may reduce movement economy and support the precise expression of force during explosive, skill-based actions [4]. Research indicates that PAPE can enhance power output and movement stability in sports such as basketball and swimming. When integrated into a periodized training plan, it may serve as a useful tool for pre-competition priming and sport-specific skill potentiation in elite athletes, potentially helping to fine-tune peak performance [5,6]. Sanda, also known as Chinese Combat, is a modern full-contact competitive combat sport originating from Chinese martial arts. Its technical system highly integrates punching, kicking, and grappling techniques, emphasizing the three-dimensional tactical principle of “kick from a distance, strike up close, and grapple at close quarters”. It places extremely high demands on athletes’ strength, speed, neuromuscular coordination, and tactical adapt- ability. During competition, athletes engage in full-contact sparring on a padded ring, aiming to score points by landing effective strikes or executing takedowns. In this study, the side kick emerges as a core and critical technique within Sanda [7]. As a core offensive and defensive technique in Sanda, the side kick combines long attack range, explosive power, and broad control coverage. It serves as a critical means for scoring, counter-defense, and spatial control during combat, with its technical quality directly influencing match outcomes [8]. This movement requires a continuous biomechanical process of “push-off, rotation, extension, and force generation”, involving the coordinated participation of mul- tiple muscle groups including lower-body push-off muscles, core stabilizers, and trunk regulators. It demands exceptional neuromuscular synchronization, force transmission efficiency, and movement precision [9]. For elite Sanda athletes
control during combat, with its technical quality directly influencing match outcomes [8]. This movement requires a continuous biomechanical process of “push-off, rotation, extension, and force generation”, involving the coordinated participation of mul- tiple muscle groups including lower-body push-off muscles, core stabilizers, and trunk regulators. It demands exceptional neuromuscular synchronization, force transmission efficiency, and movement precision [9]. For elite Sanda athletes whose techniques have reached maturity, traditional training offers limited potential for performance enhance- ment [10]. The core challenge in specialized training lies in scientifically optimizing the neuromuscular activation patterns of the side kick, improving its movement economy, and enhancing its practical applicability in combat. Surface electromyography (sEMG), as a non-invasive, high-temporal-resolution biosig- nal acquisition technique, has been widely applied in the fields of exercise science, reha- bilitation medicine, and sports engineering. By recording the electrophysiological signals generated by muscle activity, electromyography sensors objectively reflect the activation state, temporal characteristics, and coordination patterns of the neuromuscular system during movement, providing quantitative evidence for motion analysis, training opti- mization, and injury prevention. In recent years, advancements in wireless transmission, multi-channel synchronous acquisition, and signal processing algorithms have deepened the application of sEMG sensors in competitive sports, demonstrating significant value particularly in sport-specific technique analysis, fatigue monitoring, and performance evaluation. In combat sports such as Sanda, boxing, and judo, sEMG technology has https://doi.org/10.3390/s26010296
Sensors2026,26, 296 3 of 17 been employed to analyze force characteristics, muscle coordination patterns, and bilateral coordination mechanisms during key technical movements, providing critical data support for scientific training [11]. The emergence of advanced wearable sensing technologies has revolutionized the collection and analysis of biomechanical and physiological data in sports science, providing a bridge between laboratory-grade measurements and real-world athletic environments. In particular, lightweight, wireless surface electromyography (sEMG) systems, such as the one utilized in this study, exemplify this wearable paradigm. They enable the non- invasive, high-fidelity capture of neuromuscular activity during dynamic, sport-specific movements with minimal movement restriction [12]. This study leverages such wearable sEMG technology to investigate the acute effects of PAPE on muscle synergy patterns during the Sanda side kick. By employing a multi-channel, wireless setup, we move beyond traditional performance metrics (e.g., jump height) to obtain a portable, detailed, and objective mapping of the neuromuscular coordination strategies underpinning technical performance. Therefore, this work not only addresses the effects of different PAPE protocols but also demonstrates the practical application of wearable sensors in delivering nuanced, athlete-specific neurophysiological insights, contributing to the field of precision training in combat sports. Non-negative Matrix Factorization (NMF) serves as a core method for analyzing muscle coordination patterns. It extracts physiologically meaningful muscle coordination structures from complex electromyographic signals, quantifies the central nervous system’s integrated regulatory strategies for multiple muscles, and provides an objective, precise analytical perspective for revealing the neuromuscular control mechanisms underlying athletic techniques [13]. Current PAPE research predominantly focuses on enhancing fun- damental strength performance [14], with limited application studies targeting specialized techniques in combat sports like Sanda. Particularly lacking are comparative analyses of neuromuscular activation characteristics in high-level athletes performing sidekicks under different PAPE protocols, leaving unclear which PAPE intervention optimally aligns with the technical demands of the side kick. Therefore, this study aimed to identify the optimal post-activation potentiation (PAPE) protocol for enhancing the neuromuscular performance of the side kick in elite Sanda athletes. To achieve this, we employed a randomized crossover design with high-level athletes and utilized non-negative matrix factorization (NMF) to analyze and compare the muscle
intervention optimally aligns with the technical demands of the side kick. Therefore, this study aimed to identify the optimal post-activation potentiation (PAPE) protocol for enhancing the neuromuscular performance of the side kick in elite Sanda athletes. To achieve this, we employed a randomized crossover design with high-level athletes and utilized non-negative matrix factorization (NMF) to analyze and compare the muscle synergy patterns, neural drive efficiency, and activation timing of the side kick following three distinct PAPE interventions. The findings are intended to provide scientific evidence and practical guidance for the precision training and personalization of this essential technique. 2. Research Subjects and Methods 2.1. Research Subjects This study employed G*Power 3.1 software for pre-test sample size calculation. Re- peated measures ANOVA was selected as the statistical method, with effect size f = 0.30, α= 0.05, statistical power (1–β) = 0.80, three intra-group measurements, and a correlation co- efficient of 0.5. Calculations indicated a minimum sample size of 16 participants to achieve adequate statistical power. The study ultimately included 18 high-level Sanda athletes, meeting the sample size requirement. Recruited 18 national-level or higher sanda athletes with five or more years of training experience. All athletes were sourced from provincial or municipal professional teams, with an average training duration of 7.8±2.5 years, age of 22.5±3.1 years, height of 176.5±6.2 cm, and weight of 70.2±18.3 kg. Participants had no history of neurological disorders or significant lower limb injuries and signed informed https://doi.org/10.3390/s26010296
Sensors2026,26, 296 4 of 17 consent forms prior to the experiment. Basic information is presented in Table. This research protocol was reviewed and approved by the Ethics Committee for Sports Science at Shanghai University of Sport. All participants received detailed explanations of the study content and potential risks prior to the experiment and signed written informed consent forms. The experimental process strictly adhered to the ethical guidelines of the Declaration of Helsinki, ensuring the rights and safety of participants. Table 1.Characteristics of subjects (n = 18). Age (Years) Height (cm) Weight (kg) Training Duration (Years) Dominant Leg 22.5±3.1 176.5 ±6.2 70.2 ±18.3 7.8 ±2.5 Right 2.2. Research Methods 2.2.1. Experimental Equipment Surface Electromyography Acquisition System: Utilizes the Noraxon wireless sur- face sEMG system (Noraxon U.S.A. Inc., Scottsdale, AZ, USA), which operated at a sam- pling frequency of 2000 Hz with a signal bandwidth 10–500 Hz, common-mode rejection ratio > 110 dB, compliant with SENIAM standards. High-Speed Camera: Utilizes a 200 Hz model. Prior to experiments, three-dimensional spatial calibration is performed using a 12-point calibration frame (1×1×0.8 m), with a reprojection error < 0.3 mm. Vertical Jump Height Testing Device: Utilized the MY JUMP APP (iPhone version) to capture vertical jump height. Vertical Jump Height Testing Device: The My Jump 2 appli- cation (Version 2.0.1 for iOS) was used to capture vertical jump height. This application analyzes flight time from takeoff to landing using the smartphone’s high-speed camera function and calculates height based on physics formulas. Its validity and reliability have been extensively validated [15]. The vertical jump test was employed as a well-validated, non-invasive proxy for assessing lower-limb explosive power and neuromuscular readiness. While it does not directly measure the force or velocity of the side kick, improvements in vertical jump height following PAPE interventions are indicative of an enhanced state of the neuromuscular system’s capacity for rapid force production, which is a fundamental physical quality underpinning the performance of explosive technical movements like the side kick [16]. Intervention Equipment: Eleiko barbells were used for squat training. Umay resis- tance bands provided variable resistance. Neuromuscular electrical stimulation (NMES) employed the
jump height following PAPE interventions are indicative of an enhanced state of the neuromuscular system’s capacity for rapid force production, which is a fundamental physical quality underpinning the performance of explosive technical movements like the side kick [16]. Intervention Equipment: Eleiko barbells were used for squat training. Umay resis- tance bands provided variable resistance. Neuromuscular electrical stimulation (NMES) employed the Compex SP 8.0 stimulator (biphasic square wave, 75 Hz, pulse width 400µs, intensity at 90% of maximum tolerated level). Standard Sanda protective gear and punching bags were uniformly used during testing to ensure equipment consistency. 2.2.2. Test Actions Maximum Voluntary Contraction (MVC) Test: Conducted prior to formal testing, each target muscle performs 3 maximum voluntary contractions, with the maximum value used for electromyographic signal normalization. Side Kick Test: Perform 6 sidekicks at maximum speed against a punching bag on a standard Sanda ring. Target the punching bag at the subject’s chest/rib height. sEMG and kinematic data. Vertical Jump Height Test: Vertical jump height is measured using the MY JUMP APP (iPhone version). At each designated testing time point (6, 8, and 10 min post- intervention), subjects perform 3 arm-swing-free vertical jumps. The highest value is recorded for subsequent analysis. https://doi.org/10.3390/s26010296
Sensors2026,26, 296 5 of 17 2.2.3. Intervention Methods and Intensity A randomized crossover design was employed, with all subjects sequentially receiving three interventions at 10-day intervals, preceded by a 15 min warm-up session. The specific protocol is detailed in Table. Table 2.Experimental Intervention Protocol. Parameter ESG (Electrical Stimulation + Squat) RBG (Resistance Band) SQG (Heavy Squat) Primary Exercise Barbell Back Squat Band-Resisted Lateral Steps Barbell Back Squat Additional Stimulation Synchronized Neuromuscular Electrical Stimulation (NMES) on quadriceps None None Exercise Description Squat synchronized with NMES Band placed above knees; lateral stepping with controlled knee flexion (100–120 ◦ ) Squat with controlled depth (knee flexion < 90 ◦ ) Load Intensity 70% of 1RM 20% of Body Weight 90% of 1RM NMES Parameters 80 Hz, 400µs, 90% of maximal tolerated intensity / / Volume 3 sets ×3 repetitions 3 sets ×15 m 3 sets ×3 repetitions Inter-set Rest 3 min 2 min 3 min ESG: Electrical Stimulation Group; RBG: Resistance Band Group; SQG: Squat Group. 2.2.4. Testing Muscle Selection Based on the biomechanical characteristics of the side kick movement and prior research foundations, this study selected 15 muscles closely associated with the movement for sEMG signal acquisition. The selected muscles included: brachioradialis (BR), biceps brachii (BB), triceps brachii (TB), anterior deltoid (AD), external oblique (EO), gluteus maximus (GM), gluteus medius (GMed), biceps femoris (BF), rectus femoris (RF), vastus lateralis (VL), Tibialis Anterior (TA), Gastrocnemius Medial Head (GAS), as well as the right Tibialis Anterior (TAR), right Gluteus Maximus (GMR), and right Rectus Femoris (RFR). The aforementioned muscles encompass the primary agonists and synergists involved in key movement components during the side kick: trunk stabilization, hip flexion and extension, knee extension, and ankle flexion/extension. This selection comprehensively reflects the neuromuscular activation pattern and bilateral coordination characteristics of this technical movement [17]. 2.3. Data Acquisition 2.3.1. Vertical Jump Height Acquisition To accurately measure subjects’ vertical jump height, this study employed the smart- phone application My Jump App for data collection. The measurement procedure is as follows: (1) Equipment Setup: Secure the smartphone on a tripod with the camera positioned horizontally and approximately 2–3 m
bilateral coordination characteristics of this technical movement [17]. 2.3. Data Acquisition 2.3.1. Vertical Jump Height Acquisition To accurately measure subjects’ vertical jump height, this study employed the smart- phone application My Jump App for data collection. The measurement procedure is as follows: (1) Equipment Setup: Secure the smartphone on a tripod with the camera positioned horizontally and approximately 2–3 m from the subject’s jump area, ensuring full-body movement is clearly visible. (2) Jump Execution: Subjects stand within the measurement area and perform vertical jumps without arm swing. Each jump is spaced at least 30 s apart to prevent fatigue. (3) Video Recording: Use the My Jump App to record the entire process from takeoff to landing, ensuring no significant obstructions appear in the footage. (4) Height calculation: The application automatically identifies the start and end frames of the jump and calculates the jump height based on airtime (formula:h= 1 8 gt 2 , Among them: g = 9.81 m/s 2 . https://doi.org/10.3390/s26010296
Sensors2026,26, 296 6 of 17 (5) Data recording: At each designated test time point (6, 8, and 10 min post- intervention), subjects completed three vertical jumps, with the highest value recorded for subsequent analysis. 2.3.2. Electromyography Data Acquisition sEMG signals and kinematic data from 15 target muscles were simultaneously acquired using the Noraxon wireless sEMG system and a high-speed camera. To ensure consis- tency and reproducibility, the placement of all sEMG electrodes was conducted in strict accordance with a detailed, pre-defined experimental protocol. This protocol integrated the SENIAM recommendations for applicable lower limb muscles and, for muscles not covered by SENIAM (e.g., brachioradialis, biceps brachii, triceps brachii, anterior deltoid, external oblique), was based on well-established electrode placement protocols derived from previous research on similar dynamic movements [18]. The side kick motion was divided into four consecutive phases based on biomechanical characteristics: preparation phase (a,b), knee lift phase (b,c), kicking phase (c,d), and recovery phase (d,e) (Figure). Figure 1.Phases of the Side Kick Movement: preparation phase (a,b), knee lift phase (b,c), kicking phase (c,d), and recovery phase (d,e). 2.4. Data Processing Muscle synergies, intermuscular coherence, and vertical jump height analyses were performed using SPSS statistical software, R software (version 4.2.0), the Muscle Syner- gies v1.2.5 package, and custom Python(version 3.12) scripts. The specific workflow is as follows: 2.4.1. Data Extraction and Preprocessing Regarding the number of movement cycles used for synergy extraction, it is acknowl- edged that studies investigating highly stereotypical, repetitive cyclic movements (e.g., walking or cycling) often recommend analyzing a larger number of cycles (e.g., 20–40) to achieve a robust estimation of muscle synergy structures [19,20]. However, the present study focused on a discrete, maximal-effort, sport-specific skill—the Sanda side kick. For such explosive, high-intensity technical movements, the primary methodological consider- ation is to balance data representativeness against the confounding influence of fatigue, which itself can significantly alter neuromuscular coordination patterns if too many con- secutive trials are performed. Consequently, our protocol of six trials per condition was designed to capture consistent, peak-performance attempts while minimizing fatigue. This approach is consistent with established methodologies in sports science research analyzing https://doi.org/10.3390/s26010296
consider- ation is to balance data representativeness against the confounding influence of fatigue, which itself can significantly alter neuromuscular coordination patterns if too many con- secutive trials are performed. Consequently, our protocol of six trials per condition was designed to capture consistent, peak-performance attempts while minimizing fatigue. This approach is consistent with established methodologies in sports science research analyzing https://doi.org/10.3390/s26010296
Description
This study analyzes the effects of various PAPE protocols on side kick performance.