Physical Load Research Articles

Enhancing Acceleration Capabilities in Professional Women’s Football Players: A Comparative Analysis of Game-Based Versus Resisted Sprint Trainings

The recognition of high-speed demands in football has led elite academies to prioritize acceleration capabilities for player selection and promotion, particularly given their fundamental role in the motor skills of professional players and their impact on goal-related opportunities. This study explored the effectiveness of game-based versus resisted sprint training methods in enhancing the acceleration abilities of professional women’s football players. Over the entire competitive period, the training load of 26 athletes (24.2 ± 3.7 years) was assessed using GPS devices, and sprint capabilities were evaluated through four 30-m acceleration tests spaced six weeks apart. Linear mixed models (LMMs) analyzed physical load parameters, including distance covered at high speeds, speed events, and maximum speed, with periods and players as fixed and random effects, respectively. Significant sprint performance improvements were observed across all intervals, particularly when high-intensity distance volumes were combined with resisted sprint training. Conversely, high-intensity running without additional stimuli also led to performance gains, albeit to a lesser extent. Both game-based and resisted sprint training methods were effective in enhancing acceleration capabilities, while the absence of specific sprint focus did not significantly alter sprint performance. These findings support the inclusion of tailored sprint training in athletic programs to optimize acceleration in women’s football players.

External Validation of Accelerometry-Based Mechanical Loading Prediction Equations

Accurately predicting physical activity-associated mechanical loading is crucial for developing and monitoring exercise interventions that improve bone health. While accelerometer-based prediction equations offer a promising solution, their external validity across different populations and activity contexts remains unclear. This study aimed to validate existing mechanical loading prediction equations by applying them to a sample and testing conditions distinct from the original validation studies. A convenience sample of 49 adults performed walking, running, and jumping activities on a force plate while wearing accelerometers at their hip, lower back, and ankle. Peak ground reaction force (pGRF) and peak loading rate (pLR) predictions were assessed for accuracy. Substantial variability in prediction accuracy was found, with pLR showing the highest errors. These findings highlight the need to improve prediction models to account for individual biomechanical differences, sensor placement, and high-impact activities. Such refinements are essential for ensuring the models’ reliability in real-world applications, particularly in clinical and biomechanical research contexts, where accurate assessments of mechanical loading are critical for designing rehabilitation programs, injury prevention strategies, and optimizing bone health interventions.

Morning versus Nocturnal Heart Rate and Heart Rate Variability Responses to Intensified Training in Recreational Runners

BackgroundResting heart rate (HR) and HR variability (HRV) are widely used parameters to assess cardiac autonomic nervous system function noninvasively. While resting assessments can be performed during sleep or after awakening, it would be relevant to know how interchangeable the results of these measurements are. This study aimed at examining the alignment between nocturnal and morning assessments during regular endurance training and in response to intensive training. A total of 24 recreational runners performed a 3-week baseline period (BL) and a 2-week overload (OL) period (Lucia’s training impulse + 80%). Their running performance was assessed with a 3000-m running test after the BL and OL. The participants recorded daily their nocturnal HR and HRV (the natural logarithm of the root mean square of successive differences; LnRMSSD) with a photoplethysmography-based wrist device and performed an orthostatic test (2-min supine, 2-min standing) every morning with a chest-strap HR sensor. The HR and LnRMSSD segments that were analyzed from the nocturnal recordings included start value (SleepStart), end value (SleepEnd), first 4-h segment 30 min after detected sleep onset (Sleep4h), and full sleep time (SleepFull). The morning segments consisted of the last-minute average in both body positions. All segments were compared at BL and in response to the 3000-m test and OL.ResultsAll nocturnal HR and LnRMSSD segments correlated with supine and standing segments at BL (r = 0.42 to 0.91, p < 0.05). After the 3000-m test, the HR increased and LnRMSSD decreased only in the SleepStart, Sleep4h, and SleepFull segments (p < 0.05). In response to the OL, the standing HR decreased (p < 0.01), while the LnRMSSD increased (p < 0.05) in all segments except for SleepStart. The Pearson correlations between relative changes in nocturnal and morning segments were − 0.11 to 0.72 (3000-m) and − 0.25 to 0.79 (OL). The OL response in Sleep4h HR and LnRMSSD correlated with the relative change in 3000-m time (r = 0.63, p = 0.001 and r=-0.50, p = 0.013, respectively).ConclusionsNocturnal and morning HR and LnRMSSD correlated moderately or highly in the majority of cases during the BL, but their responses to intensive training were not similarly aligned, especially in LnRMSSD. The nocturnal segments seemed to be sensitive to physical loading, and their responses were associated with the performance-related training responses.

Development of a seat support mechanism for guiding users to an appropriate posture in a seated-style echocardiography robot

Abstract This paper proposes a seat support mechanism to solve the problem of misalignment between the chest examination and probe scanning areas when the patient is bent in a seated-style echocardiography robot. To guide the patient to an appropriate body position where their chest is within the examination range of the chest examination unit while minimizing the physical load of the patient, the posture of the patient must satisfy the three following conditions. (i) The breech must be in contact with the seat surface, (ii) the legs must be vertical to the floor, and (iii) the chest and mechanism must be parallel while the probe scanning and chest examination ranges must match. The human body was modeled to derive a posture that satisfies the aforementioned conditions for the height of each individual, and a seat support mechanism with four degrees of freedom was installed to guide the user to the derived posture. By installing this mechanism, the body load of the left biceps brachii, right biceps brachii, left latissimus dorsi, and right latissimus dorsi was reduced to 64.7%, 52.7%, 86.4%, and 80.2%, respectively. The sharpness of the image contours was improved to 103.8%.

Experimental and Numerical Indentation Tests to Study the Crack Growth Properties Caused by Various Indenters Under High Temperature

ABSTRACTThis paper investigates the influence of indenter shape and rock texture on the crack growth properties and rock hardness. For this purpose, two different rock specimens such as basalt and marble with various textures were prepared and tested by Vickers indentation hardness device with rhombus indenter shape under two different temperatures of 35°C and 100°C. Concurrent with the experimental test, Vickers indentation simulations have been done on three calibrated rock models with nine different indenter shapes. The tensile strength of marble was 8 MPa, while basalt had a tensile strength of 10.8 MPa. Regarding compressive strength, marble exhibited 71 MPa, whereas basalt had a compressive strength of 153 MPa. Marble and basalt had elastic moduli of 45 and 95 GPa, respectively. The physical loading was applied vertically at a rate of 0.004 mm/min. The rock's texture and temperature significantly impact Vickers indentation hardness. Penetration by the Vickers indenter creates an elastic‐plastic stress field, leading to radial cracks due to exceeding the critical stress level. Ring cracks are caused by bulging of the test material and nested cracks directly under the indentation due to high shear and bending stresses in the region. The indentation shape affected the extent of the damage zone below it, leading to increased crack growth with smaller indentation diameters. The radial fracture number increased when the cross‐section changed from circular to quadrilateral shape. The crack growth and damage zone area increased with higher rock temperature due to increased rock brittleness.

Changes in the functional state of athletes under the influence of physical load

The main goal of the presented research is to study the effect of sports physical activity on the quality of regulation and adaptive capacity of the cardiovascular system of athletes and non-athletes. The obtained results showed that the number of heart beats decreases during the rest period. Changes in the number of heart rates when performing a physical load correspond to the age norms of athletes. In addition, no significant changes were founding in the number of heart rates and systolic blood pressure, but diastolic blood pressure significantly decreased, and pulse pressure increased.

Formation and Development of Professionally Important Qualities of Civil Defense Specialists at Higher Education Institutions

The article deals with the peculiarities of the formation and development of professionally important qualities of civil defense specialists at higher education institutions. Different approaches to the definition of the concept of «professionally important qualities» are analyzed, according to which the concept is considered as biologically determined (physiological, psychological, innate abilities and inclinations), individual and psychological properties of a personality as a specialist as well as personal properties formed and developed in the process of training and professional activities. The author considers some classifications of professionally important qualities of a civil defense specialist. For any type of professional activity, such professionally important qualities as discipline, responsibility, accuracy, attentiveness, observation, sensitivity, punctuality, restraint, ingenuity, ability to self-control and professional self-assessment of one's own states and actions, purposefulness, developed visual and figurative memory and analytical thinking are relevant. Risky professions require physical endurance, coordination of movements, dexterity, ability to tolerate heavy physical loads and high temperatures, determination and courage, mental and emotional stability, risk-taking, ability to switch, distribute, concentrate and hold attention, react quickly to the situation and make independent decisions and act in extreme conditions, a sense of duty, etc. The following groups of professionally important qualities for civil defense specialists are identified and substantiated: psychophysiological, intellectual, emotional and volitional, moral and ethical, managerial and communicative. The possibilities of their formation and development in the process of cadets' professional training at a higher education institution are considered.

Optimizing E-Bike Controls for Human-bike Interaction to Enhance Riding Experience and Efficiency

E-bikes are now used for sports, rehabilitation, and work, not just commuting. Riders adjust power assistance and transmission to handle different conditions and reach their desired physical load. This interaction between the rider, bike, and environment can become complex due to faster speeds, shorter response times, and varying conditions, potentially leading to discomfort. A study with 21 non-athletes explored how riders manage the physical load on e-bikes during a simulated indoor riding session with 66 stages of varying slope resistance. Participants controlled the e-bike to maintain a moderate intensity, and data on latency of e-bike control, number of controls, acceptable pedaling power, heart rate, and perceived exertion were collected. On average, riders made their control adjustment 5.3 seconds after a slope change and used 2.7 control attempts to reach an acceptable pedaling power. The study found that the most acceptable pedaling power were similar across different slopes, suggesting a consistent preferred load. Participants aimed to maintain stable pedaling power despite external disturbances, targeting a moderate exercise intensity (66.9% maximal heart rate and a rate of perceived exertion of 12.1). The findings indicate that it's possible to estimate a personal preferred load, which could inform future studies on maintaining this load and improving the e-bike riding experience.

Effect of Soft Knee Brace on Shank Movement in Running

Background: Soft knee braces are used for the protection and treatment of knee injuries in light-intensity activities of daily life. Soft knee braces have several functions, such as stabilizing and supporting the lower limb posture. However, previous studies did not investigate the effects of a soft knee brace on the lower limbs during vigorous-intensity activities. Aims: The objective of this study was to investigate the effect of a soft knee brace on the physical load and stability of the lower limb during running as a vigorous-intensity activity. Methods: Participants were asked to run with or without a soft knee brace, and lower-limb movements during running were measured using an inertial sensor on the shank. Results: The result showed that soft knee brace significantly reduced the magnitude and mediolateral standard deviation of shank acceleration. Conclusion: The results of this study indicate the possibility that wearing a soft knee brace can improve the physical load and stability of the lower limbs during running.

Проблема футбольного інтелекту у сучасних дослідженнях

Speed, dynamism, high physical and mental loads characterize modern soccer. In this regard, the player's intelligence plays an important role during the game, because it: affects the form of tactical behavior; allows to make effective decisions in stressful situations; increases the player's ability to understand and establish links between game episodes and solve problematic game episodes using available tactical information. Therefore, the study of theoretical, tactical and psychological aspects of the development of intellectual abilities of a player is important for obtaining high results in this sport. The aim of the study is to analyze theoretical research on the peculiarities and development of intellectual abilities of soccer players. Research methods: theoretical analysis and generalization of scientific and methodological literature. Research results. As a result of the conducted analysis of literary sources it was determined that soccer intelligence is a way of thinking that allows a player to solve problem situations using knowledge, experience, skills and natural data, which are best suited for a particular game situation. Player's intelligence is a complex multilevel structure that is the result of player's adaptation to the conditions of the game space, constitutes a special form of tactical behavior of the player, is the result of purposeful tactical training of the player as a set of elementary processes of information processing and a system of cognitive processes. Conclusions. In soccer, the intellectual component is an integral part of both the game itself and the training process. Coaches are interested in its improvement and effective use because soccer intelligence is a way of thinking that allows a player to successfully solve problem situations using knowledge, experience, skills, and natural data that are best suited for a particular game situation.

Effects of small-sided games on some recovery markers in football

Background and Study Aim. Small-sided games (SSGs) are widely used in football training to replicate match conditions while controlling the physical load on players. Variations in the number of players during these games can significantly influence key recovery markers. This study aims to investigate the effects of variations in player numbers on maximal heart rate, blood lactate levels, and perceived exertion in small-sided games acutely applied in football. Material and Methods. The study involved 28 male football players who were also university students (mean age 24.89±4.59 years, mean height 179±0.04 cm, mean body weight 73.21±4.34 kg). The participants were divided into three groups based on the number of players (2 vs. 2, 4 vs. 4, and 8 vs. 8). Heart rate and lactate levels were measured at three time points: before training, immediately after training, and 30 minutes post-training. Results. The study revealed that post-training maximal heart rates (MHR) and lactate levels were significantly higher across all groups compared to pre-training levels, while measurements taken 30 minutes post-training were significantly lower than post-training levels (P&lt;0.05). No significant differences were found between pre-training and 30-minute post-training MHR values across the three groups (P&gt;0.05). Post-training MHR values were similar between the 2 vs. 2 and 4 vs. 4 groups (P&gt;0.05), whereas the 8 vs. 8 group showed significantly higher values (P&lt;0.05). Post-training and 30-minute post-training lactate levels were similar between the 4 vs. 4 and 8 vs. 8 groups (P&gt;0.05), but the 2 vs. 2 group had significantly lower levels (P&lt;0.05). Perceived exertion levels post-training were similar between the 2 vs. 2 and 4 vs. 4 groups (P&gt;0.05), while the 8 vs. 8 group reported significantly higher perceived exertion levels (P&lt;0.05). Conclusions. Small-sided games with varying numbers of players are an effective method for modulating physical load during football training. These findings underscore the importance of considering game format in designing training sessions to optimize player performance and recovery.

КОНДИЦІЙНЕ ТРЕНУВАННЯ КІБЕРСПОРТСМЕНІВ З ВИКОРИСТАННЯМ МОБІЛЬНИХ ДОДАТКІВ

The issue of insufficient physical activity among computer game players remains relevant. This study proposes a solution based on the comprehensive use of gaming-oriented mobile applications for the conditioning training of esports athletes. A sequential pedagogical experiment was conducted to determine the effectiveness of esports athletes applying an aerobic-focused conditioning training program (slow running). The program’s unique feature is its implementation in a remote format using mobile applications for planning, execution, control, and performance evaluation. It is based on an original concept of implementing running training in the form of a mobile running application (the so-called “exergame”) with a game-like nature (“Zombies, Run!”). The program was designed for a six-week implementation. Its effectiveness was determined by evaluating the dynamics of indicators: 1600 m run time; calculated maximal oxygen consumption (VO2 max); and heart rate (HR). Subjective attitudes towards the program’s physical loads were assessed using the Rating of Perceived Exertion (RPE) scale and the Physical Activity Satisfaction Needs scale. It was found that esports athletes significantly (p&lt;0.05) improved their 1600 m run time, VO2 max, and HR indicators under the influence of the slow running program. Along with the volume and intensity increase of the running load, a decrease in RPE scale indicators was observed. The obtained data confirmed the advantages of the comprehensive use of mobile applications for normalizing the motor activity of esports athletes in the form of conditioning training. Both the remote format of planning and accounting and the game format of activities contributed to increasing the engagement of esports athletes in physical activity. The effectiveness of the slow running training program for esports athletes using mobile applications was established in terms of increasing physical activity (regular, organized physical activity), improving physical fitness (duration and volume of slow running), enhancing physical condition (VO2 max, HR), and interest in physical activity (adherence).

Role and Impact of Prophylactic Interventions in the Conservative Treatment of Carpal Tunnel Syndrome

Carpal tunnel syndrome (CTS) refers to the compression or tension over the median nerve at the level of the wrist and represents the most commonly encountered compression mononeuropathy. It is diagnosed significantly more often in individuals, whose work involves similar, repetitive movements. The condition affects approximately 4–6% of the active population. Its social aspect stems from the significant deterioration of patients' professional and private life, which, in a high percentage of cases, leads to a change in profession. Multiple surgical and conservative treatment approaches have been described. The literature proposes a general recommendation for compliance with prophylactic interventions and a specific mobilization regimen but a consensus on the subject has not yet been achieved. In our study, we followed 45 patients diagnosed with CTS who reported pain and altered sensation, over a period of 6 months. The patients were divided into three groups which were randomly assigned to different treatment modalities. All patients received the same prophylactic interventions with regard to the physical load and exercises, which were to be followed individually over the course of the study. At the end of the study, the obtained data were analyzed statistically and we reported a correlation between patient improvement and the frequency of the exercises.

Spatially defined microenvironment for engineering organoids

In the intricately defined spatial microenvironment, a single fertilized egg remarkably develops into a conserved and well-organized multicellular organism. This observation leads us to hypothesize that stem cells or other seed cell types have the potential to construct fully structured and functional tissues or organs, provided the spatial cues are appropriately configured. Current organoid technology, however, largely depends on spontaneous growth and self-organization, lacking systematic guided intervention. As a result, the structures replicated in vitro often emerge in a disordered and sparse manner during growth phases. Although existing organoids have made significant contributions in many aspects, such as advancing our understanding of development and pathogenesis, aiding personalized drug selection, as well as expediting drug development, their potential in creating large-scale implantable tissue or organ constructs, and constructing multicomponent microphysiological systems, together with functioning at metabolic levels remains underutilized. Recent discoveries have demonstrated that the spatial definition of growth factors not only induces directional growth and migration of organoids but also leads to the formation of assembloids with multiple regional identities. This opens new avenues for the innovative engineering of higher-order organoids. Concurrently, the spatial organization of other microenvironmental cues, such as physical stresses, mechanical loads, and material composition, has been minimally explored. This review delves into the burgeoning field of organoid engineering with a focus on potential spatial microenvironmental control. It offers insight into the molecular principles, expected outcomes, and potential applications, envisioning a future perspective in this domain.

On the osteogenic differentiation of dental pulp stem cells by a fabricated porous nano-hydroxyapatite substrate loaded with sodium fluoride

In the present study, nano-hydroxyapatite (n-HA) powder was extracted from carp bone waste to fabricate porous n-HA substrates by a molding and sintering process. Subsequently, the substrates were loaded with different amounts of sodium fluoride (NaF) through immersion in NaF suspensions for 10, 7.5, and 5 min. The NaF-loaded n-HA substrates were then examined for their structural and physical properties, chemical bonds, loading and release profile, pH changes, cytotoxicity, and osteogenic effect on dental pulp stem cells (DPSCs) at the level of RNA and protein expression. The results showed that the n-HA substrates were porous (> 40% porosity) and had rough surfaces. The NaF could be successfully loaded on the substrates, which was 6.43, 4.50, and 1.47 mg, respectively for n-HA substrates with immersion times of 10, 7.5, and 5 min in the NaF suspensions. It was observed that the NaF release rate was rather fast during the first 24 h in all groups (39.06%, 36.43%, and 39.57% for 10, 7.5, and 5 min, respectively), and decreased dramatically after that, indicating a slow detachment of NaF. Furthermore, the pH of the medium related to all materials was changed during the first 4 days of immersion (from 7.38 to pH of about 7.85, 7.84, 7.63, and 7.66 for C0, C5, C7.5, and C10, respectively). The pH of media associated with the C7.5, and C10 increased up to 4 days and remained relatively constant until day 14 (pH = 7.6). The results of the cytotoxicity assay rejected any toxicity of the fabricated NaF-loaded n-HA substrates on DPSCs, and the cells could adhere to their surfaces with enlarged morphology. The results showed no effect on the osteogenic differentiation at the protein level. Nevertheless, this effect was observed at the gene level.

Kaempferol Reduces Cardiopulmonary Load and Muscular Damage in Repeated 400‐m Sprints: A Double‐Blind, Randomized, Placebo‐Controlled Trial

ABSTRACTPlants exposed to hypoxic conditions have been suggested to produce more biologically active phytochemicals than those exposed to normal oxygen levels. Previously, we investigated 314 highland crop species and showed that the flavonoid kaempferol extracted from a highland quinoa grain markedly increased mitochondrial metabolism and ATP production in a hypoxic environment in vitro. Thus, we hypothesized that kaempferol would be effective during exercise under harsh conditions, in which anaerobic metabolism occurs. This study adopted a double‐blind, placebo‐controlled, crossover design to investigate the effect of a single oral dose of kaempferol (10 mg) on the athletic performance‐related indicators of 13 male university athletes (20.8 ± 0.7 years) who performed two consecutive 400‐m runs with the shortest 90‐min interval assuming qualifying and main races. Although no significant differences were observed in the 400‐m race times between the placebo and kaempferol groups, kaempferol intake markedly reduced the respiratory and heart rates during the second run (p &lt; 0.05). In addition, kaempferol intake reduced the levels of muscle damage markers, myoglobin, and aspartate transaminase (p &lt; 0.05). A single oral dose of kaempferol reduced the cardiopulmonary burden and muscle damage in individuals participating in 400‐m runs. Kaempferol may be a useful supplement for relieving the physical load, particularly in individuals performing strenuous exercises with high oxygen demand.Trial Registration: UMIN Clinical Trials Registry in Japan: UMIN000049588

The Relationship Between Physical And Mental Workload On Job Fatigue In Maxim Car Drivers In Kupang City In 2024

Transportation is a system consisting of certain facilities along with the flow and control system that allows people or goods to move from one place to another efficiently at any time to support human activities. Indonesia as a developing country certainly has a very rapid development of services in the fields of land, sea and air transportation. Transportation owned by the Indonesian Nation certainly has innovations from past to present in order to advance transportation services, one of which is an online provider company. Online transportation companies offer transportation services such as online motorcycle taxis, online taxis, delivery of goods, food delivery and so on, thus making this service in demand by many people. Likewise in Kupang City where there are several online transportation options, one of which is Maxim car transportation which has the advantage of being quite cheap. The high demand for Maxim online transportation in Kupang City has an impact on the fatigue experienced by online transportation drivers. One of them is also felt by Maxim Mobil drivers. Based on the researcher's initial survey of Maxim drivers in Kupang city, fatigue often occurs in Maxim Car drivers due to the increase in Maxim Car users in Kupang City. This type of research is quantitative using analytic survey method and cros sectional research design. The sample in this study amounted to 81 respondents from a total population of 430 drivers selected using accidental sampling method. The results showed that there was no significant relationship between physical load and work fatigue and there was a significant relationship between mental load and fatigue in maxim car drivers in Kupang City.

Complex therapy of mineral metabolism in service dogs

The high physical and functional load of service dogs causes changes not only in body systems, but also in metabolism as a whole. An integrated approach to the study of this problem and the search for a pharmacotherapeutic solution will allow us to correct biochemical changes in the body of dogs and improve the performance and quality of life of animals. The purpose of the study was to study the therapeutic effectiveness of a complex of metabolic stimulants for the correction of mineral metabolism. For the study, 16 service dogs were selected in the area of application of the general search profile, belonging to the Ministry of Internal Affairs of Russia in the Altai Territory. Blood was drawn at the beginning and end of the study to analyze red blood cell counts, hemoglobin, hematocrit, glucose, cholesterol, triglycerides, iron, magnesium, zinc, calcium, phosphorus, and chloride. According to the results of the study, it was established that a violation of homeostasis in service dogs was accompanied by changes in some indicators of red blood, as well as pathology of mineral metabolism. After a course of pharmacotherapy, an increase in red blood cells (up to 7.9±0.22*×1012 cells/l) and hemoglobin (up to 141.66±7.32 g/l) was observed in dogs. Carbohydrate metabolism in both groups was characterized by hypoglycemia (3.34±0.21–3.43±0.28 mmol/l). By the end of the study, the glucose level in the experimental group significantly increased by 31.4% relative to the animals in the control group. By the end of the study, cholesterol levels in dogs in the experimental group decreased more rapidly compared to the control group. The study of the dynamics of mineral metabolism indicators revealed a significant increase in iron levels in the experimental group of animals (up to 25.3±1.9 µmol/l), which was 22.8% higher than the control value. Changes in other indicators of mineral metabolism did not differ significantly between the groups, although dogs receiving stimulating therapy showed positive dynamics of changes in mineral metabolism indicators. The use of a complex of metabolic stimulants “Suiferrovita”, “Strolitin”, “Amber Acid” stabilized red blood counts and contributed to the development of a tendency towards the restoration of mineral metabolism.

Evolution and Characterization of Uniaxial Compression Damage of Coal Measure Rock

In order to study the evolution law of uniaxial compression damage and its characterization method, three kinds of rocks with different lithology that commonly exist in coal measure rock were taken as the research objects to explore the relationship between their mineral composition, microstructure and mechanical properties, and the feasibility of acoustic emission (AE) characteristic parameters and AE spatial location to characterize the evolution process of uniaxial compression damage of rocks was compared and analyzed. A damage constitutive model based on AE cumulative ringing count was established and verified by numerical simulation. The results show that the differences in the micromorphology and mineral composition of coal measures with different lithology directly affect their physical and mechanical properties and load damage characteristics. AE characteristic ringing count can effectively represent the damage evolution process of rock during loading. Based on rock porosity characteristics and AE cumulative ringing count during loading, a constitutive model considering initial damage and cumulative damage was established. The theoretical analysis results of the damage constitutive model are in good agreement with the results of laboratory experiments and numerical simulation, which can be used to analyze the damage process of coal measure rock under load.

HEART RATE VARIABILITY IN FOOTBALL PLAYERS AND TRACK AND FIELD ATHLETES

Objective of the study: To investigate the state of the autonomic nervous system in athletes based on heart rate variability indicators. Materials and methods: The study was conducted on 142 male athletes (67 football players and 75 track and field athletes) aged 17-20 years, with an average age of 18.5±1.5 years. Depending on the type of higher nervous activity, athletes were divided into 4 groups: sanguine (41.55%), choleric (28.87%), phlegmatic (19.01%), and melancholic (10.56%). Heart rate variability (HRV) was studied using the "BioMouse" system. A t-test for independent samples (Welch's t-test) was used to analyze the significance of differences between the groups. Results of the study: It was found that the highest adaptive capabilities were observed in phlegmatic athletes, who demonstrated high SDNN and HF values, as well as a low tension index (IN). Their calm temperament allows for better adaptation to physical exertion and maintaining a balance between sympathetic and parasympathetic activity. The lowest adaptive capabilities were observed in melancholics, who showed high IN and LF values, as well as low SDNN and HF, indicating an imbalance in the autonomic nervous system and lower resilience to physical stress. Overall, beginner athletes tended to have slightly higher heart rates and lower HRV indicators (SDNN), LF, and HF compared to more experienced athletes of the 2nd-3rd ranks. This is due to the fact that first-year athletes have not yet fully adapted to physical loads, leading to more pronounced dominance of the sympathetic nervous system and less parasympathetic activity. KEYWORDS: variability, heart rate, athletes, football players, track and field athletes, autonomic nervous system, physical exertion