This observational longitudinal study will examine the somatic and psychological profile of team sport athletes across seasonal training cycles. The study will include male and female athletes who play football, volleyball, or ice hockey. The planned study population consists of 300 participants, including 200 adults aged 18 to 38 years and an additional 100 adolescent athletes aged 14 to 17 years.

Participants will be assessed at two time points, before and after a transitional period in the annual training cycle, such as the off-season, holiday break, preparatory period, or competitive period. These periods are associated with changes in training load, recovery, daily routine, and lifestyle, and may therefore influence both body composition and psychological functioning. The longitudinal design will allow evaluation of changes over time and identification of factors associated with more favorable or less favorable adaptations.

The study will assess body composition and selected behavioral and psychological characteristics. Adult participants will undergo body composition assessment using bioelectrical impedance analysis and dual-energy X-ray absorptiometry (DEXA). Adolescent participants included under the approved amendment will undergo the same study procedures except for DEXA. All participants will complete standardized self-report questionnaires assessing eating behavior, physical activity, sport-related perfectionism, and body esteem.

The questionnaires used in the study include the Three-Factor Eating Questionnaire (TFEQ-13), the International Physical Activity Questionnaire (IPAQ), the sport perfectionism questionnaire, and the Body Esteem Scale. These tools will be used to examine whether eating behaviors, activity patterns outside formal training, perfectionism, and body image are associated with changes in body composition and related characteristics across different phases of the sports season.

The main goal of the study is to improve understanding of how seasonal changes in training and daily habits affect the physical and psychological characteristics of athletes. The results may help identify factors linked to beneficial or unfavorable changes in body composition and well-being, and may support the development of more individualized monitoring, nutrition, training, and psychological support strategies for athletes.

Participation in the study is voluntary. All participants, and legal guardians in the case of minors, will receive information about the study procedures, potential risks, and study aims before consent is obtained. Data will be handled confidentially and analyzed in anonymized form. Study findings are intended for scientific publication and for practical application in athlete monitoring and care.

This study is designed to evaluate the somatic and psychological profile of athletes across seasonal training cycles in team sports. The project focuses on football, volleyball, and ice hockey players and aims to improve understanding of how seasonal changes in training load, competition demands, recovery, and daily routine are associated with changes in body composition, eating-related behaviors, physical activity patterns, perfectionism, and body image. The study is observational and longitudinal and will follow athletes across selected transitional periods of the sports season.

The rationale for the study is based on the assumption that athletic performance is influenced not only by sport-specific training but also by the interaction between physical and psychological factors. Body composition is an important component of sports readiness, as fat mass, muscle mass, and bone-related parameters may affect strength, power, speed, endurance, and movement efficiency. At the same time, athletes' eating behavior, activity outside formal training, perfectionistic tendencies, and body esteem may influence how they respond to changes in training or competition demands throughout the season.

The study population will include male and female athletes participating in organized team sports. The planned total enrollment is 300 participants. The original protocol includes 200 adult athletes aged 18 to 38 years. Under an approved amendment, the study population has been expanded to include an additional 100 adolescent athletes aged 14 to 17 years. Both healthy and injured athletes may participate, provided that they meet the study eligibility criteria and belong to football, volleyball, or ice hockey teams.

The study will be carried out at two time points, before and after a selected transitional period within the annual training cycle. Depending on the team schedule, this period may correspond to the off-season, holiday break, preparatory period, or competitive period. These phases are especially relevant because they are commonly associated with changes in training volume, training intensity, recovery, nutrition-related routines, and general lifestyle organization. Such changes may lead to measurable variation in both somatic characteristics and psychological or behavioral responses.

The main objective of the study is to assess associations between selected behavioral and psychological factors and physical characteristics in athletes across seasonal cycles. In particular, the study will examine how eating-related behaviors, physical activity, sport-related perfectionism, and body image are related to body composition and how these relationships may change over time. The study also aims to identify factors associated with more favorable or less favorable changes in somatic characteristics during periods of altered training demands.

A further objective is to describe the typical somatic profile of male and female team sport athletes and to determine whether this profile changes across different phases of the season. The study will examine body mass and body composition characteristics, including fat mass, lean or muscle-related mass, bone-related parameters, and the regional distribution of body tissues. The project is intended to provide a more comprehensive understanding of how athletes adapt to seasonal demands and whether some of these changes may be interpreted as beneficial sport-specific adaptation or as potentially unfavorable from a health or performance perspective.

Adult participants will undergo body composition assessment using two methods. The first method is bioelectrical impedance analysis (BIA), which will be used to estimate body mass and body composition. The second method is dual-energy X-ray absorptiometry (DEXA), which will provide a more detailed assessment of body composition, including fat-related and bone-related measures and their distribution across body segments. According to the approved amendment, adolescent participants aged 14 to 17 years will undergo the same study procedures except for DEXA. For this group, the protocol excludes DEXA while preserving the remainder of the study procedures.

In addition to body composition measurements, participants will complete a set of standardized self-report questionnaires. These tools are intended to assess selected behavioral and psychological domains that may be relevant to seasonal changes in athletes. The questionnaires include the Three-Factor Eating Questionnaire (TFEQ-13), which evaluates cognitive restraint, loss of control over eating, and emotional eating; the International Physical Activity Questionnaire (IPAQ), which assesses physical activity performed in everyday life; the sport perfectionism questionnaire (DKPS), which measures dimensions of perfectionism in the sports context; and the Body Esteem Scale (BES), which evaluates body-related self-perception and satisfaction.

These tools were selected because they allow multidimensional analysis of athlete functioning beyond standard physical measurements. Eating behavior may influence energy balance, body mass regulation, and responses to training or reduced activity. Physical activity outside organized training may contribute to total energy expenditure and may differ across phases of the season. Perfectionism may act as a motivating factor in some athletes but may also be linked to stress, self-criticism, or maladaptive responses. Body esteem may be relevant to self-perception, well-being, and the athlete's relationship with body composition changes. The combination of these measures is intended to provide a broad profile of athlete functioning across the season.

The repeated-measures design will make it possible to compare findings before and after a defined seasonal period and to estimate the direction and magnitude of change over time. This design may also support the identification of predictors of change. For example, the study will explore whether stronger cognitive control of eating is associated with more stable body composition, whether emotional eating is associated with less favorable changes in body mass or fat mass, and whether specific perfectionism profiles are linked to better maintenance of desirable physical characteristics during changes in routine or training load.

The study also allows comparison across sex and sport discipline. Football, volleyball, and ice hockey differ in movement demands, contact characteristics, energy expenditure, and seasonal structure. These differences may be associated with different patterns of body composition change and different behavioral or psychological responses. The study therefore seeks to identify both general patterns across team sports and discipline-specific features that may be relevant for athlete monitoring and support. Differences between male and female athletes will also be considered, particularly in relation to body image, eating-related behaviors, and responses to seasonal variation.

The practical significance of the project lies in its potential contribution to athlete care and performance monitoring. The findings may help coaches, sports dietitians, psychologists, physiotherapists, and sports medicine professionals better understand how athletes respond to different phases of the season. Improved knowledge in this area may support more individualized strategies for training planning, nutrition support, body composition monitoring, recovery management, and psychological assistance. The results may be especially useful during transition periods, when athletes may be more vulnerable to unfavorable changes in routine, body composition, or well-being.

The study is not designed to assign participants to any treatment or intervention. It is an observational project in which participants are assessed under real-life sport conditions without experimental allocation to behavioral, nutritional, or training interventions. The purpose is to observe and analyze naturally occurring variation in somatic and psychological characteristics across seasonal cycles rather than to test the efficacy of a specific intervention.

Participation in the study is voluntary. Participants will be informed about the purpose of the study, the study procedures, and any potential inconvenience or risk associated with participation. For the additional group of adolescent participants, informed participation procedures will be applied in accordance with the approved amendment. The amendment states that all newly included participants will receive information about the purpose, course, and potential risks of the study and will sign informed consent to participate; for minors, this should be implemented in a manner consistent with applicable consent requirements.

The risks associated with study participation are expected to be low. BIA is non-invasive and commonly used in body composition assessment. DEXA in adult participants involves exposure to a very low dose of ionizing radiation, and the original study documentation indicates that no major direct adverse effects are expected, although a minimal long-term radiation-related risk is acknowledged. The examination may be mildly uncomfortable because participants are required to remain still for several minutes. Completion of questionnaires may involve temporary fatigue or mild emotional discomfort, particularly when questions concern eating behavior, body image, or perfectionistic tendencies, but serious risk is not expected. Participants may withdraw from the study at any time.

The study documentation states that participants may benefit from receiving detailed individual information about their body composition, including fat-related, muscle-related, and bone-related measures where applicable. More broadly, the project may generate knowledge with value for future scientific publications and practical application in the field of sports science and athlete support.

Data collected in the study will be processed confidentially and stored securely. According to the protocol, personal data will be protected in accordance with applicable data protection requirements, stored on password-protected devices, and accessed only by authorized study personnel. Identifying data will be replaced with study codes so that analysis and dissemination of results can be performed in anonymized form. The results are intended for scientific publication, conference presentation, and further academic use in a way that does not allow identification of individual participants.

Overall, the project seeks to provide an integrated description of how team sport athletes change across seasonal cycles and how physical and psychological variables interact in that process. By combining body composition assessment with behavioral and psychological measures in a repeated observational design, the study aims to produce findings that are relevant both scientifically and practically. The inclusion of both adult and adolescent athletes broadens the scope of the project and may help identify age-related similarities and differences in the response of athletes to seasonal demands, while maintaining the protocol distinction that DEXA is not used in the adolescent group added by amendment.

Inclusion Criteria

• Male or female athletes.
• Age 14 to 38 years.
• Participation in a team sport, including football, volleyball, or ice hockey.
• Regular training experience of at least 5 years.
• Current membership in a sports club.
• Valid medical clearance confirming no contraindications to sport participation.
• Ability to understand the study procedures and complete study questionnaires.
• Willingness to provide informed consent.
• For participants under 18 years of age, written consent from a parent or legal guardian.

Exclusion Criteria

• Does not meet one or more inclusion criteria.
• Pregnancy, due to exposure to ionizing radiation in adult participants undergoing DEXA.
• Refusal or inability to provide informed consent.
• For minors, absence of parental or legal guardian consent.
• Any medical or organizational condition that, in the investigators' opinion, would prevent safe participation or valid completion of the study procedures.

DEXA will be performed only in adult participants.

Male and female team sport athletes recruited from sports clubs and academies in Poland, including football, volleyball, and ice hockey players aged 14 to 38 years.