Rev Bras Fisiol Exerc. 2026;25:e255653

doi:  10.33233/rbfex.v25i1.5653

ORIGINAL ARTICLE

Inflammatory profile and tissue injury in runners (5, 10, 15 km) and ultramarathon: IL-6, myoglobin

Perfil inflamatório e lesão tecidual em corredores (5, 10, 15 km) e ultramaratona: IL-6, mioglobina

 

Helvio de Oliveira Affonso1,2, Mylena Barros de Souza1

 

1Appto Assessoria Esportiva, Vitória, ES, Brazil

2Universidade de Vila Velha (UVV), Vila Velha, ES, Brazil

 

Received: December14, 2026; Accepted: February 27, 2026

Correspondence: Helvio de Oliveira Affonso, helvio@appto.com.br

 

How to cite

Affonso HO, Souza MB. Inflammatory profile and tissue injury in runners (5, 10, 15 km) and ultramarathon: IL-6, myoglobin. Rev Bras Fisiol Exerc. 2026;25:e255653. doi: 10.33233/rbfex.v25i1.5653

 

Abstract

Introduction: Understanding the inflammatory responses and changes in muscle damage biomarkers induced by endurance exercise is crucial for optimizing training and recovery protocols. Method: This study analyzed interleukin-6 (IL-6) and myoglobin (MYO) levels in 75 recreational runners in Vitória-ES, across distances of 5, 10, 15 km, and a 12-hour ultramarathon (79.93 ± 28.65 km). The runners had average paces of 5.19 ± 1.22 min/km (5 km), 5.16 ± 0.57 min/km (10 km), 4.36 ± 0.12 min/km (15 km), and 10.91 ± 5.83 min/km (ultramarathon). Capillary blood samples were collected using micro EDTA tubes, with digital puncture and automatic lancets, and analyzed by point of care testing (POCT) technology. Results: 5 km, IL-6 decreased by 27.30% and MYO increased by 240.41%. 10 km, IL-6 decreased by 13.99% and MYO increased by 343.31%. 15 km, IL-6 decreased by 3.10% and MYO increased by 1062.61%. Ultramarathon IL-6: Pre: 7.66 ± 3.77 pg/ml, Mid-race: 48.55 ± 81.57 pg/ml (+ 533.68%), Post-race: 26.54 ± 20.82 pg/ml (-91.84% relative to pre-exercise). Eight days later: 4.07 ± 1.47 pg/ml (-46.86% relative to pre-exercise). Myoglobin: Pre: 22.42 ± 19.73 ng/ml, Mid-race: 314.19 ± 160.76 ng/ml (+ 1300.85%), Post-race: 423.07 ± 149.65 ng/ml (+1787.20% relative to pre-exercise). Eight days later: 40.50 ± 18.81 ng/ml (+ 80.70% relative to pre-exercise). Conclusion: The variability in responses reinforces the need for monitoring and individualized approaches, considering biopositive and bionegative adaptations resulting from biological individuality and physiological capacity.

Keywords: interleukin-6; myoglobin; running; inflammation, biomarkers; muscle fatigue

 

Resumo

Introdução: Compreender respostas inflamatórias e alterações nos biomarcadores de dano muscular provocadas pelo exercício de endurance é crucial para otimizar protocolos de treino e recuperação. Método: Este estudo analisou os níveis de interleucina-6 (IL-6) e mioglobina (MYO) em 75 corredores recreacionais em Vitória-ES, distâncias de 5, 10, 15 km e ultramaratona 12 h (79,93 ± 28,65 km). Os corredores apresentaram paces médios de 5,19 ± 1,22 min/km (5 km), 5,16 ± 0,57 min/km (10 km), 4,36 ± 0,12 min/km (15 km) e 10,91 ± 5,83 min/km (ultramaratona). As amostras de sangue capilar foram coletadas em micro tubos EDTA, com punção digital e lancetas automáticas, analisadas por tecnologia POCT (point of care testing). Resultados: 5 km IL-6: PRÉ 4,33 ± 2,28 pg/ml e PÓS: 3,16 ± 2,64 pg/ml, (-27,30%). Mioglobina: PRÉ: 22,39 ± 8,50 ng/ml e PÓS 63,11 ± 28,70 ng/ml, (+ 240,41%). 10 km IL-6: PRÉ: 4,78 ± 2,11 pg/ml PÓS: 4,17 ± 2,53 pg/ml, (-13,99%). Mioglobina: PRÉ: 30,43 ± 12,30 ng/ml e PÓS: 129,70 ± 45,60 ng/ml (+343,31%). 15 km IL-6: PRÉ: 5,99 ± 1,98 pg/ml. PÓS: 5,70 ± 2,45 pg/ml (-3,10%). Mioglobina: PRÉ: 28,91 ± 10,70 ng/ml. PÓS: 263,88 ± 85,50 ng/ml (+1062,61%). Ultramaratona IL-6: Pré: 7,66 ± 3,77 pg/ml Meio: 48,55 ± 81,57 pg/ml (+ 533,68%), Pós: 26,54 ± 20,82 pg/ml, (- 91,84%) em relação ao pré-exercício. Oito dias após: 4,07 ± 1,47 pg/ml (- 46,86%) em relação ao pré-exercício. Mioglobina: Pré: 22,42 ± 19,73 ng/ml, Meio da prova: 314,19 ± 160,76 ng/ml (+1300,85%), Pós: 423,07 ± 149,65 ng/ml, (+ 1787,20%) em relação ao pré-exercício. Oito dias após: 40,50 ± 18,81 ng/ml (+ 80,70%) em relação ao pré-exercício. Conclusão: A variabilidade nas respostas reforça a necessidade de monitoramento e abordagens individualizadas, considerando as adaptações biopositivas e bionegativas resultantes da individualidade biológica e lastro fisiológico.

Palavras-chave: interleucina-6; mioglobina; corrida; inflamação; biomarcadores; fadiga muscular

 

Introduction

 

Long-distance running has emerged as a widely adopted practice in Brazil, especially in vibrant urban centers like the metropolitan region of Vitória-ES [1,2,3]. This phenomenon not only reflects a trend towards health and well-being but also provides a rich platform to investigate the complexities of physiological responses to exercise [3]. In 2021, Vitória was recognized as one of the "Brazilian Cities Friendly to Physical Activity" by PUC-PR, highlighting the local commitment to healthy practices and sustainable urban development [4].

Endurance exercise, while widely recognized for its cardiovascular health benefits and overall well-being [5,6], also induces an acute inflammatory response [7,8,9,10]. This response can result in exercise-induced muscle damage (EIMD), characterized by an increase in metabolic demand and the production of reactive oxygen species (ROS) [11,12]. These ROS have the potential to compromise muscle cell membrane integrity, resulting in the release of tissue biomarkers into the bloodstream [11].

In this context, two biomarkers stand out: interleukin-6 (IL-6) and myoglobin. IL-6, released by both muscles and the immune system during intense physical activity [14], serves as a central mediator of the inflammatory response [10,13,15,16,17,18,19]. Its release is a clear indicator of physical and inflammatory stress, essential for adapting and modulating the body's immune response to exercise [13,14,16,17,18,19]. Myoglobin, an essential muscle protein, is released into the bloodstream when cell damage occurs [20,21,22], serving as a direct marker of muscle injury and reflecting the extent of tissue damage induced by physical exertion [20,21,22].

Monitoring these biomarkers is crucial due to interindividual variability [23], influenced by factors such as age, training level, genetics, and nutrition [13]. This variability is especially important for recreational runners, as it significantly affects recovery and injury risk [2]. Understanding inflammatory and muscle damage response patterns in specific populations allows for the optimization of recovery strategies and exercise prescriptions, improving practitioners' quality of life and preventing long-term health complications [23].

This study aims to characterize IL-6 and myoglobin levels in recreational runners at various distances in the metropolitan region of Vitória-ES. Additionally, it seeks to correlate these responses with anthropometric and performance variables, highlighting the importance of monitoring these biomarkers in exercise management. By understanding these responses, we can develop more personalized approaches to recovery and injury prevention, promoting safer and more effective sports practice. This not only contributes to individual health but also advances scientific knowledge in the field of sports and physical exercise.

 

Methods

 

Study design

 

This longitudinal study was conducted during 5 km, 10 km, 15 km, and ultramarathon (12-hour duration, average distance of approximately 80 km) running events in the metropolitan region of Vitória-ES. The research was approved by the Research Ethics Committee of the University of Vila Velha (CAAE 78770017.0.0000.5064), and all participants signed the Informed Consent Form before data collection.

 

Sample eligibility criteria

 

The sample included 75 recreational runners, distributed among the distances of 5 km, 10 km, 15 km, and ultramarathon (12-hour duration, average distance of approximately 80 km). Inclusion criteria were: (1) age over 18 years; (2) participation in at least one running event in the past year; (3) absence of acute musculoskeletal injuries. Exclusion criteria included: (1) presence of chronic inflammatory diseases or infections; (2) use of anti-inflammatory drugs seven days prior to collection; (3) pregnancy; (4) inability to participate in pre-exercise blood collection.

 

Ultramarathon eligibility criteria

 

Age: over 18 years; no participation in more than one ultramarathon that year; absence of acute musculoskeletal injuries; participation in at least one running event in the past year. Exclusions: presence of chronic inflammatory diseases or infections; use of anti-inflammatory drugs seven days prior to collection; pregnancy; inability to participate in pre-exercise blood collection.

 

Data collection

 

Performance was assessed by running pace (minutes per kilometer), using Global Positioning System (GPS) data from athletes' individual wearables, confirmed and adjusted by official race results.

 

 

Figure 1 - Runner group summary

 

Blood sample collection and analysis

 

Capillary blood samples were collected in EDTA microtubes by finger lobe puncture, using G-Tech 28G automatic lancets, at two points: (1) pre-exercise, at rest, at least 30 minutes before the run; (2) immediately post-run, for the 5, 10, and 15 km groups. For the ultramarathon group, samples were collected at four points: (1) pre-exercise, at rest, at least 30 minutes before the run; (2) mid-race (approx. 6h into the race); (3) immediately post-race (12h post); and (4) eight days post-race. Samples were analyzed using the AFIAS-6, an automated fluorescence immunoassay point-of-care system, offering quick and precise biomarker identification.

 

Inflammatory biomarker determination

 

Levels of interleukin-6 (IL-6) for understanding inflammatory response status and myoglobin for understanding tissue (muscle) injury status were measured using the AFIAS-6, which combines the accessibility of point-of-care systems with the robustness of automated systems. This method offers fast and reliable results for biomarker evaluation.

 

Results

 

Figure 2 – Results 5 km

 

 

Figure 3 – Results 10 km

 

Figure 4 - Results 15 km

 

 

Figure 5 – Results ultramarathon

 

 

Statistical analysis

 

Descriptive analysis with calculations of mean, standard deviation, minimum, and maximum for biomarkers pre- and post-exercise was performed. The percentage variation was calculated using the formula: [(Post Value - Pre Value) / Pre Value] × 100. Correlations between body weight and biomarker variation were tested using Pearson's correlation coefficient. All analyses were performed using statistical software with a significance level of p < 0.05.

 

Table I - Correlations between pace and biomarker variation

 

 

Discussion

 

Long-distance running, especially in ultramarathon events, offers a unique opportunity to explore the complexities of physiological responses to exercise, particularly in the urban context of Vitória-ES [2], a city recognized for its commitment to healthy practices [4]. The ultramarathon, involving 12-hour runs, presents significant challenges to the human body, highlighting the need to understand the inflammatory and muscle damage responses associated with such extreme exercise.

Endurance exercise, like ultramarathons, is widely recognized for its cardiovascular health benefits and overall well-being [5,6]. However, it also triggers an acute inflammatory response [7,8,10], which can result in exercise-induced muscle damage (EIMD) [11]. This phenomenon is characterized by increased metabolic demand and the production of reactive oxygen species (ROS) [11,12], which can compromise muscle cell membrane integrity and release tissue biomarkers into the bloodstream.

Two critical biomarkers in this context are interleukin-6 (IL-6) and myoglobin. During ultramarathons, IL-6 levels experience a significant increase, reflecting the intense inflammatory response and physical stress associated with these prolonged runs [10,14]. IL-6, released by both muscles and the immune system [15,16,17], acts as a central mediator of the inflammatory response [18,19], modulating the immune response to intense exercise. In contrast, myoglobin, a muscle protein [20,21], is released into the blood when cell damage occurs, serving as a direct marker of muscle injury [22]. During ultramarathons, myoglobin levels increase substantially, indicating the extent of tissue damage.

Monitoring the kinetics of these biomarkers is crucial due to interindividual variability [9], influenced by factors such as age, training level, genetics, and nutrition [13]. This variability is especially relevant for recreational runners participating in ultramarathons [2], as it significantly affects recovery and injury risk. Understanding inflammatory and muscle damage response patterns in ultramarathon events allows for the optimization of recovery strategies and exercise prescriptions, improving participants' quality of life and preventing long-term health complications [23].

This study aims to deepen the understanding of IL-6 and myoglobin responses in ultramarathon runners in the metropolitan region of Vitória-ES. Additionally, it seeks to correlate these responses with anthropometric and performance variables [3], underscoring the importance of monitoring these biomarkers in exercise management. Understanding these responses allows the development of more personalized approaches to recovery and injury prevention, promoting safer and more effective sports practice. This not only contributes to individual health but also advances scientific knowledge in the field of sports and physical exercise, providing valuable insights for coaches, athletes, and health professionals.

 

Analysis by running distance

 

5 km

IL-6 pre vs. post-levels: There was a decrease from 4.33 ± 2.28 pg/ml to 3.16 ± 2.64 pg/ml (-27.30%). This reduction suggests that in shorter runs, the inflammatory response may be minimal or recovery begins quickly after the run.

Myoglobin pre vs. post-levels: Increased from 22.39 ± 8.50 ng/ml to 63.11 ± 28.70 ng/ml (+240.41%), indicating some degree of muscle damage, but on a smaller scale compared to longer distances.

 

10 km

IL-6 pre vs. post-levels: Levels decreased from 4.78 ± 2.11 pg/ml to 4.17 ± 2.53 pg/ml (-13.99%). The slight decrease suggests a moderate inflammatory response that is quickly regulated.

Myoglobin pre vs. post-levels: Increased from 30.43 ± 12.30 ng/ml to 129.70 ± 45.60 ng/ml (+343.31%), showing a more pronounced increase in muscle damage compared to 5 km.

 

15 km

IL-6 pre vs. post-levels: Slight reduction from 5.99 ± 1.98 pg/ml to 5.70 ± 2.45 pg/ml (-3.10%). This indicates that the inflammatory response is more sustained but still controlled.

Myoglobin pre vs. post-levels: Rose from 28.91 ± 10.70 ng/ml to 263.88 ± 85.50 ng/ml (+1062.61%), indicating a substantial increase in muscle damage, which becomes more pronounced with increased distance.

 

Ultramarathon

IL-6 Levels: Pre vs. Mid: Increase from 7.66 ± 3.77 pg/ml to 48.55 ± 81.57 pg/ml (+533.68%), reflecting an intense inflammatory response.

Pre vs. Post: Reduction to 26.54 ± 20.82 pg/ml (-91.84% relative to pre) and further decrease to 4.07 ± 1.47 pg/ml eight days after (-46.86% relative to pre), indicating a prolonged recovery process.

Myoglobin pre vs. mid-levels: Increased from 22.42 ± 19.73 ng/ml to 314.19 ± 160.76 ng/ml (+1300.85%), showing a sharp increase in muscle damage.

Pre vs. Post: Increase to 423.07 ± 149.65 ng/ml (+1787.20%), with levels still elevated eight days later (40.50 ± 18.81 ng/ml, +80.70% relative to pre), suggesting that muscle recovery is more extended.

 

General discussion

 

The data from this study highlight a clear correlation between the distance covered and the intensity of physiological responses, specifically in terms of inflammation and muscle damage. As running distance increases, there is an escalation in both the inflammatory response and muscle damage indicators, as evidenced by rising levels of interleukin-6 (IL-6) and myoglobin.

 

Responses in short-distance runs

 

In shorter runs, such as 5 km, inflammatory responses are more moderate, and recovery is fast. This may be due to shorter duration of intense physical exertion, which allows the body to better manage metabolic stress and tissue damage. Studies show that shorter-duration activities result in less pronounced inflammatory responses, facilitating more efficient recovery [13].

 

Responses in medium-distance runs

 

For 10 km and 15 km runs, there is a more noticeable increase in IL-6 and myoglobin levels. This increase suggests that, as distance and intensity of effort increase, the body faces more significant metabolic demand, resulting in a more robust inflammatory response and evident muscle damage [10].

 

Responses in ultramarathons

 

In ultramarathon events, the inflammatory response and muscle damage become significantly more pronounced. Prolonged running results in substantial production of reactive oxygen species (ROS), increasing oxidative stress and muscle damage. This type of extreme exercise requires more elaborate and prolonged recovery strategies [12].

 

Importance of individualized monitoring

 

Interindividual variability in physiological responses, influenced by factors such as age, training level, and genetics, underscores the need for personalized monitoring. The literature emphasizes the importance of adapting recovery and training strategies to athletes' individual needs, considering their unique characteristics and competition types [7].

 

Implications for training and recovery

 

Understanding the relationship between running distance and physiological response is crucial for developing effective training programs. Coaches and athletes can use this information to adjust training loads and implement recovery strategies that maximize performance and minimize injury risk. Additionally, this knowledge can inform exercise prescription and nutritional counseling, ensuring athletes are physically prepared to handle the challenges of long-distance running. In conclusion, this study not only emphasizes the importance of adapting recovery strategies to exercise distance and intensity but also highlights the need for individualized approaches, considering the complexity of the physiological responses involved.

 

Conclusion

 

Understanding these physiological dynamics allows for the development of more personalized approaches to recovery and injury prevention, promoting safer and more effective sports practice. Furthermore, precise biomarker monitoring provides valuable insights for performance optimization and injury risk reduction, contributing to significant advances in the field of sports and exercise science.

 

Conflicts of interest

The authors declare no conflicts of interest.

 

Funding sources

Study conducted without specific financial support.

 

Author contributions

Concept and design: Affonso HO; Data collection: Affonso HO, Souza MB; Analysis and interpretation: Affonso HO, Manuscript writing: Affonso HO, Souza MB, Critical review: Affonso HO

 

 

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