A direct relationship exists between micronutrient status and the performance level of athletes. However, this relationship is often not given due importance when compared with the macronutrient status of an athlete. An exponential growth has been observed in the number of women participating in various sports in recent years [1]; however, as several physiological and hormonal patterns are specific to females, these athletes are more prone to injuries and various health disorders compared with their male counterparts [2]. Female athletes tend to have lower hemoglobin levels than those of male athletes and non-athletic counterparts, a condition that is termed “sports anemia.” This could be due to factors, such as plasma volume expansion, hemodilution, increased iron loss, imbalanced diet, or poor iron absorption [3]. The hematological status of female athletes is significantly linked to their fitness levels. Reduced hemoglobin levels can lead to reduced oxygen-carrying capacity, which can result in reduced oxygen to the muscles during exercise, leading to hindered performance [4].

Iron supplementation in iron-depleted female athletes has been shown to improve iron status and energy efficiency [5]. To address the increasing training needs and optimize performance, female athletes need to maintain their hematological status in the optimal range by consuming a well-balanced, colorful diet that includes various foods rich in iron [6,7]. Endurance athletes are frequently reported to have a higher prevalence of iron deficiency owing to the predominant role of iron in aerobic pathways [8]. Although several studies have assessed the prevalence of anemia in adolescents, research on the prevalence of anemia in Indian female athletes remains limited, which necessitates the current study. Additionally, a huge gap in research exists regarding nutritional strategies for better performance in female athletes [9]. Sufficient evidence to establish a correlation between hematological status and endurance lacks, specifically in ball badminton and volleyball athletes, making this the first study to correlate and analyze their relationship with the dietary iron intake of Indian female athletes. Hence, this study aimed to analyze the relationships among hematological status, endurance performance, and dietary iron intake in female ball badminton and volleyball athletes in India.

Table 1 shows the descriptive statistics for the VB and BB athletes, and for all the athletes together. The VB athletes were significantly heavier and taller than the BB athletes (p < 0.001). They also had better endurance than BB athletes as reflected in their VO₂ max levels (p < 0.001). Significant differences were not observed in hemoglobin levels; however, BB athletes had higher WBC (p < 0.018) and platelet levels (p < 0.002).

Among all the athletes, 53.8% (n = 56) were anemic, with a higher percentage of BB athletes (31.7%) compared with that of VB athletes (22.1%) Table 2. Most athletes had normal WBC, RBC, and platelet counts.

Approximately 58.7% of the athletes had been practicing their sport for 4-7 years and the majority of athletes participated at the collegiate and national levels (Table 3).

Among all the athletes, those with higher than normal hemoglobin levels exhibited better endurance. Non-anemic athletes performed better than anemic athletes (Table 4).

A moderate positive correlation was observed between hemoglobin level and cardiorespiratory endurance among VB athletes (Table 5). A significant correlation was exhibited between platelet level and muscular endurance for all athletes. Significant positive correlations were also observed among WBC count, hematocrit, MCV levels, and plank test results for BB athletes.

The frequency of consumption of iron-rich foods, including green leafy vegetables, organ meat, nuts, and seeds, was extremely low (Table 6). Jaggery is a good substitute for white sugar; however, it was not used by the majority of female athletes. The dietary iron intake of the athletes was found to be 12.11 mg and the mean dietary intake of the BB athletes (12.44 mg) was slightly higher than that of the VB athletes (11.79 mg).

This study aimed to correlate the hematological status of female athletes with their endurance levels. The study findings confirm that the cardiorespiratory and muscular endurance of non-anemic athletes was better than that of anemic female athletes and athletes with elevated levels of hemoglobin performed better. More than half of all the athletes were anemic and the dip in endurance of female athletes could be attributed to lower levels of hemoglobin.

The stature and weight of the VB athletes were higher than those of the BB athletes. A previous study of 163 elite female VB players reported body heights ranging from 161 to 194 cm [14], which is similar to the average height of VB athletes (166.45 ± 10 cm) in this study. The cardiorespiratory and muscular endurance of VB athletes was significantly higher when compared with that of BB athletes. An Indonesian study of female VB players also indicated that 40% of athletes had good levels of VO₂ max [15].

A greater number of VB athletes had a normal BMI than BB athletes.

The average BMI of VB athletes in the current study (21.3 ± 3.02) was similar to the BMI levels of female VB players > 18 years of age in a study of 61 female VB athletes [16]. The near-ideal body composition of VB athletes could be attributed to their increased physical activity compared with that of BB athletes. The prevalence of anemia was 53.8% in all athletes, whereas it was 31.7% and 22.1% in BB and VB athletes, respectively. The Hb and RBC levels of these athletes were considerably low when compared with the Hb and RBC levels of elite Korean wrestlers, whereas their WBC levels were similar [17]. Despite the implementation of several governmental initiatives to reduce the burden of anemia in females, the prevalence remains high not only in non-athletic women but also in the athletic population [18]. An increased loss of iron is observed in female athletes owing to heavy training loads and altered hepcidin production in athletes with low energy availability and diminished carbo-hydrate intake [19,20].

Non-anemic female athletes performed better in the Cooper and plank tests, confirming the positive correlation between hemoglobin level and endurance [21] In endurance athletes, a close relationship may exist between changes in intravascular volume and exercise capacity [22]. A cross-sectional study involving 178 adolescents from the Physical Activity and Health Longitudinal Study (PAHLS) also demonstrated a moderately positive association between Hb and VO₂ max in adolescent girls [23]. This study also showed a significant positive correlation between the WBC count and muscular endurance. Consistent with this, a plank test has been shown to improve immunocyte function [24]. A lower WBC count was observed in elite athletes training in aerobic sports than in team sport athletes, which is consistent with the current findings of a significant correlation between WBC count and muscular endurance [25].

The dietary intake of iron was much lower than the recommended dietary allowance for a normal adult woman, which is 29 mg/day [26]. The overall intake of dietary iron through the consumption of iron-rich foods must be increased to meet the recommended dietary allowances [20]. Nutritional interventions that can improve hematological status should be implemented by the government, especially for athletes. Providing nutrition education to female athletes can prove beneficial for athletes to include iron-rich foods along with a diet that is balanced in all other macro-and micronutrients, thereby enhancing performance [28].

This study demonstrated a positive correlation between hematological status and endurance levels in female athletes. The prevalence of anemia in female athletes is a cause for concern because of its impact on diminishing cardiorespiratory and muscular endurance. The consumption pattern of iron-rich foods highlights the need to encourage athletes to improve their iron intake through adequate intake of energy and protein, and regular consumption of iron-rich foods in combination with vitamin C-rich foods.

The strength of the current study is the determination of the complete blood count of female athletes (i.e., it was not limited to the estimation of hemoglobin alone), which has provided added insights into its relationship to endurance in athletes. Additionally, the use of venous blood instead of capillary blood to estimate hemoglobin eliminates errors in estimation.

One of the limitations of this study is that it only focused on the hematological status of female athletes; however, the assessment of their iron status through serum ferritin and transferrin levels strongly validate the results of the current study. Another major limitation is the lack of a non-athlete control group, which would have strengthened comparisons and clearly defined the effect of sports training on hematological status and endurance. The dietary intake of iron by athletes was self-reported and hence needs to be validated through future studies on female athletes using more accurate and validated food weight methods. Future studies with larger sample sizes for each type of sport and the inclusion of female athletes in other sport categories will further validate the findings of this study. An in-depth analysis of dietary patterns and sociodemographic factors will provide a better understanding of the causal relationship between hematological status and endurance in female athletes.