Laboratory-based assessment of cardiorespiratory function is a widely applied method in sports science. Most performance evaluations focus on oxygen uptake parameters. Despite the well-established concept of oxygen deficit introduced by Hill in the 1920s, relatively few studies have examined its behavior during submaximal exercise, with limited exploration of deficit dynamics. The present study aimed to analyze the behavior of oxygen deficit in young female handball players (N = 42, age: 15.4 ± 1.3 years) during graded exercise. Oxygen deficit was estimated using the American College of Sports Medicine (ACSM) algorithm, restricted to subanaerobic threshold segments of a quasi-ramp exercise protocol. Cardiorespiratory parameters were measured with the spiroergometry test on treadmills, and body composition was assessed via Dual Energy X-ray Absorptiometry (DEXA). Cluster and principal component analyzes revealed two distinct athlete profiles with statistically significant differences in both morphological and physiological traits. Cluster 2 showed significantly higher relative VO₂ peak (51.43 ± 3.70 vs. 45.70 ± 2.87 mL·kg⁻¹·min⁻¹; p < 0.001; Cohen’s d = 1.76), yet also exhibited a greater oxygen deficit per kilogram (39.03 ± 16.71 vs. 32.56 ± 14.33 mL·kg⁻¹; p = 0.018; d = 0.80). Cluster 1 had higher absolute body mass (69.67 ± 8.13 vs. 59.66 ± 6.81 kg; p < 0.001), skeletal muscle mass (p < 0.001), and fat mass (p < 0.001), indicating that body composition strongly influenced oxygen deficit values. The observed differences in oxygen deficit profiles suggest a strong influence of genetic predispositions, particularly in cardiovascular and muscular oxygen utilization capacity. Age also emerged as a critical factor in determining the potential for adaptation. Oxygen deficit during submaximal exercise appears to be a multifactorial phenomenon shaped by structural and physiological traits. While certain influencing factors can be modified through training, others especially those of genetic origin pose inherent limitations. Early development of cardiorespiratory capacity may offer the most effective strategy for long-term optimization.

Purpose: The assessment of endocrine status in elite athletes is typically linked to training load and perceived stress; however, the relationship between hormonal parameters and psychosomatic and stress indicators remains insufficiently understood. This study aimed to investigate the associations between endocrine status and stress, mood, and psychosomatic status indicators in elite handball players. Methods: In a cross-sectional study, salivary cortisol (with no strict control over wake-up time), testosterone, and—in female athletes—17-β-estradiol concentrations were assessed in 584 elite handball players aged 14–35 years using ELISA. Psychological variables were evaluated using the Perceived Stress Scale (PSS), Profile of Mood States (POMS), and the Health Behavior in School-aged Children Symptom Checklist (HBSC-SCL). Associations were examined using non-parametric tests and general linear models adjusted for age. Results: Hormonal and psychological variables demonstrated significant age-related trends. No significant associations were observed between hormonal parameters and perceived stress or mood disturbance (values for the general linear model (GLM) were all p > 0.05). In contrast, psychosomatic symptom severity was significantly associated with cortisol levels in male athletes (GLM, p < 0.001) and testosterone levels in female athletes (GLM, p = 0.009). Multivariate analyses confirmed the relevance of psychosomatic symptoms and indicated interaction effects between stress-related factors. Conclusion: Psychosomatic symptoms were more closely associated with endocrine status than with perceived stress or mood disturbance in elite handball players. However, these associations were characterized by relatively small effect sizes, indicating that psychosomatic symptoms explain only a limited proportion of the variance in hormonal parameters. These findings suggest that psychosomatic indicators may provide a more sensitive reflection of physiological strain and support the use of integrated monitoring approaches combining endocrine and psychosomatic measures in elite sport. In practical terms, routine monitoring of psychosomatic symptoms alongside hormonal measures may help practitioners to identify early signs of physiological strain and support timely adjustments in training load and recovery strategies.