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Salivary IL-6/cortisol ratio and RSImod may serve as non-invasive indicators of non-functional overreaching in NCAA Division I American football athletes, with role-specific physiological signatures.

In a 15-week observational study of 39 NCAA Division I American football players, both starters and non-starters exhibited patterns consistent with non-functional overreaching (NFOR), but with distinct physiological signatures. Higher IL-6/cortisol ratios were associated with higher RSImod in starters, while in non-starters, higher IL-6/cortisol ratios were associated with poorer recovery despite lower external loads. Mid-season declines in countermovement jump performance coincided with biomarker changes suggestive of accumulated fatigue.

Last updated: Aug 8, 2026โ€ข0 RCTsโ€ข๐Ÿ“– Read as article โ†’

Evidence Score

Evidence Score32/100
Human RCTโ˜†โ˜†โ˜†โ˜†โ˜†
Meta-analysisโ˜†โ˜†โ˜†โ˜†โ˜†
Mechanismโ˜…โ˜…โ˜…โ˜…โ˜…
Safetyโ˜…โ˜…โ˜…โ˜…โ˜†
Confidencelow

Study Evidence

Study 1. Multimodal indicators of non-functional overreaching in NCAA Division I American football athletes: evidence for role-specific physiological adaptation.

observational

Aychman MM, Vinson K, Tasnim N, Perez J, Hodes GE, Basso JC ยท Frontiers in physiology (2026)

Participants: N/A
Duration: 15 weeks
Intervention: Observational monitoring of salivary biomarkers (cortisol, testosterone, IL-6, TNF-ฮฑ), neuromuscular performance (countermovement jump metrics, PlayerLoad), and recovery self-reports (sleep quality, muscle soreness) across a competitive season.
Outcome: Associations between biomarker ratios (testosterone/cortisol, IL-6/cortisol) and recovery/performance measures; patterns indicative of NFOR.
Effect Size: N/A
Population: 39 male NCAA Division I American football athletes (age 20.4 ยฑ 1.75 years), including starters and non-starters.

Result:

PubMed: 42553027DOI: 10.3389/fphys.2026.1818629

Mechanism Graph

Accumulated training and competition stress leads to altered salivary biomarker ratios, particularly increased IL-6/cortisol ratio.
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These biomarker changes are associated with reduced neuromuscular performance (e.g., lower RSImod) and poorer recovery (higher soreness, lower sleep quality).
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Physiological responses differ by role: starters show better recovery with higher testosterone/cortisol, while non-starters show greater strain despite lower external loads.
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Result: Both groups exhibit NFOR, but with role-specific physiological signatures, suggesting the need for tailored recovery strategies.

Limitations

  • โš Observational design; no control group, so causality cannot be established.
  • โš Small sample size (n=39) and single-site study may limit generalizability to other teams or sports.

Frequently Asked Questions

What is non-functional overreaching (NFOR) and how is it detected in this study?โ–ผ

NFOR is a state of accumulated training stress leading to performance decrements and prolonged fatigue. In this study, NFOR was inferred from patterns of salivary biomarkers (e.g., IL-6/cortisol ratio), neuromuscular performance (e.g., RSImod), and self-reported recovery metrics across a season.

How does the IL-6/cortisol ratio relate to recovery in football athletes?โ–ผ

Higher IL-6/cortisol ratios were associated with poorer recovery in non-starters (higher soreness, lower sleep quality) despite lower external loads, while in starters, higher IL-6/cortisol ratios were associated with higher RSImod, suggesting a different adaptive response.

Are there role-specific differences in physiological adaptation to training?โ–ผ

Yes, starters showed a positive association between testosterone/cortisol ratio and better recovery, while non-starters exhibited greater physiological strain (higher IL-6/cortisol) even with lower external loads, indicating that monitoring and recovery strategies should be tailored by playing role.

What practical implications do these findings have for coaches and sports scientists?โ–ผ

Salivary biomarker ratios, especially IL-6/cortisol, combined with neuromuscular measures like RSImod, could serve as non-invasive tools to monitor fatigue and guide individualized recovery interventions in American football athletes.

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References

  1. 1.Aychman MM, Vinson K, Tasnim N, Perez J, Hodes GE, Basso JC. "Multimodal indicators of non-functional overreaching in NCAA Division I American football athletes: evidence for role-specific physiological adaptation.." Frontiers in physiology, 2026. PMID: 42553027 DOI: 10.3389/fphys.2026.1818629
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.