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The running science nerd alert.

Learn to train smart, run fast, and be strong with Thomas Solomon PhD

December 2024

This page contains the latest research studies on exercise science and sports nutrition.

Use them to help level up your running performance or coaching practice.

The studies are divided into sub-topics: general training methods, sports nutrition and hydration, sports supplements, recovery (inc. sleep), athlete health (inc. mental health), injuries and rehab, and female athlete physiology, plus my beer of the month to wash it all down.

I’ve provided a deeper insight into my favourite studies of the month. For everything else, you can click on the study title to plunge deep into the full paper and evaluate the authors’ findings. In doing so, aim to be skeptical, not cynical.

My favourite papers this month.

Towards Precision Sports Nutrition for Endurance Athletes: A Scoping Review of Application of Omics and Wearables Technologies. Bedrač et al. (2024) Nutrients. (click the title to access the full article)

What type of study is in this article?

Scoping reviewA scoping review ask a broad question like “What is already known about this intervention?” or “What outcomes have already been examined in the treatment of this condition?”. This helps us understand what is known about a topic and whether a systematic review to answer a specific research question is needed (or possible) given the available evidence..

What is the hypothesis or research question?

How are omics technologies and wearable devices applied in systems biology-driven sports nutrition for endurance athletes?

What did the authors do to test the hypothesis or answer the research question?

Used a scoping review following PRISMA-ScR guidelines. The approach used a literature search in PubMed, Scopus, Web of Science, and Google Scholar from June to October 2024.
The eligibility criteria for including studies were endurance athletes, omics approaches, wearable technologies, and nutritional interventions.
A total of 52 studies were included — 31 randomized controlled trials (RCTs), 11 non-randomized interventions, 7 longitudinal cohort studies, and 3 case studies (6%) — containing 1695 participants, 123 of whom were classified as elite athletes.

What did they find?

The review identified studies using omics: Metagenomics (11 studies), metabolomics (10), nutrigenetics (10), multi-omics (7), CGM (11), proteomics (1), epigenomics (1), lipidomics (1).
Common Interventions included nutritional supplements (such as caffeine, polyphenols, and pequi oil), Carbohydrate and Protein Supplements, Fruit and Plant-Based Polyphenols, Beetroot and Nitrate-Based Products, Omega-3 Fatty Acids and Lipid-Based Supplements, Continuous Glucose Monitoring (CGM), Oligopeptides and Amino Acids, and Hydration Strategies and Electrolyte Drinks.
Outcome metrics showed a high variability in biomarkers linked to recovery, performance, and health. There was no consensus on the impact of omics technologies on long-term outcomes.
Meta-analyses included in the review contained limited heterogeneity data (i.e. variability between studies was not documented), GRADE certainty levels (an evaluation of evidence quality) were not consistently reported, and there was high variability (I-squared greater than 75%) in many interventions.

What are the strengths of the study?

The review included a comprehensive inclusion of diverse omics platforms and cutting-edge wearable technologies and used rigorous methodology following PRISMA-ScR guidelines.
There was an emphasis on research gaps and future directions in precision sports nutrition.

What are the weaknesses of the study?

The review identified that many studies have a small sample size.
There is a lack of consistent protocols between studies and, therefore, limited generalizability of findings.
There is a a lack of high-powered crossover randomised onctrolled trials to validate biomarker-based dietary interventions.
And there is no unified framework for applying findings to dietary guidelines.

Are there any funding issues or conflicts of interest that may influence the findings?

No → There are no specific conflicts of interest are reported in the article.

Are the findings useful in application to training and/or coaching practice?

Partially → The review highlights the need for individualized dietary strategies over traditional guidelines and demonstrates the applicability for tailoring nutrition plans using biomarkers and wearables. However, the evidence base is far from being able to inform how this could be done because there is a lack of high-quality randomised controlled trials.

What is my Rating of Perceived scientific Enjoyment?

RP(s)E = 9 out of 10.

Reliability and Validity of Predicted Performance in the Severe-Intensity Domain From the 3-Minute All-Out Running Test. Busso et al. (2024) Int J Sports Physiol Perform. (click the title to access the full article)

What type of study is in this article?

Observational studyObservational studies can have different types of study designs, including cross sectional, case-control, retrospective cohort, and prospective cohort studies. Typically, an observational study examines a specific cohort of people to characterise them and learn about them; there are no intentional interventions (e.g.,. people are not prescribed a diet). Sometimes the cohort of people is followed over time to determine whether there is a relationship between the natural exposure to a specific variable (e.g. exposure to dietary saturated fat intake) and a specific outcome of interest (e.g. cardiovascular disease)..

What is the hypothesis or research question?

Can the 3-minute all-out running test (3MT) provide reliable and valid predictions of performance in the severe-intensity domain?

What did the authors do to test the hypothesis or answer the research question?

They studied 12 male runners, aged 37 ± 12 years, experienced in high-intensity interval training. Of these, 8 performed additional time trials..
Participants underwent two 3MTs (test #1 and test #2) on a 400m outdoor track after a familiarization session..
GPS data (18 Hz) were used to estimate critical speed (CS) and distance covered above CS (D′).
Predicted times for 1200m (T1200) and 3600m (T3600) were calculated and compared to actual performance in time trials.
They used intraclass correlation coefficients (ICCs) to examine reliability with systematic and random error analysis, and Pearson correlations to assess predictive validity.

What did they find?

Good-to-excellent reliability for CS, T1200, and T3600 (ICC > 0.95; standard error of measurement [SEM]: 1.3%–2.2%).
Poor reliability for D′ (ICC = 0.55; SEM = 27%).
Strong correlation between predicted and actual times for T1200 (r = 0.87) and T3600 (r = 0.91). Significant systematic underestimation for T3600 (6.4%–7.8%).
Random error for T1200 and T3600 ranged between 4.4%–6.1%.
To conclude, 3MT reliably predicts performance changes over time but has limitations for individual long-duration predictions due to random and systematic errors.

What are the strengths of the study?

Robust methodology using repeated measures and advanced statistical analysis.
Inclusion of real-world running conditions with outdoor track assessments.
Application of high-frequency GPS data (18 Hz) for accurate tracking.
Strong predictive correlation for mid-duration (5 min) exercises.

What are the weaknesses of the study?

Small sample size (n=12; only 8 completed all trials).
Poor reliability of D′ limits its standalone utility.
Systematic underestimation of performance for longer durations (e.g., T3600).
Potential influence of learning effects despite familiarization sessions.
Limited generalizability to untrained or elite athletes.

Are there any funding issues or conflicts of interest that may influence the findings?

Unknown → No funding or conflict of interest details were provided in the article.

Are the findings useful in application to training and/or coaching practice?

Yes → The findings are useful for detecting training adaptations in the severe-intensity domain. However, caution is needed when applying 3MT predictions to individual athletes, especially for long-duration events, due to inherent errors. And, although there is good reliability and robust predictive methods, there is a small sample size and notable underestimation errors for long-duration predictions.

What is my Rating of Perceived scientific Enjoyment?

RP(s)E = 7 out of 10.

Iron deficiency, supplementation, and sports performance in female athletes: A systematic review. Pengelly et al. (2024) J Sport Health Sci. (click the title to access the full article)

What type of study is in this article?

Systematic reviewA systematic review answers a specific research question by systematically collating all known experimental evidence, which is collected according to pre-specified eligibility criteria. A systematic review helps inform decisions, guidelines, and policy..

What is the hypothesis or research question?

Does iron deficiency negatively impact sports performance in high-level female athletes, and can iron supplementation improve these performance outcomes?

What did the authors do to test the hypothesis or answer the research question?

The authors conducted a systematic review following PRISMA guidelines and searching Medline, SPORTDiscus, Web of Science, Scopus, CINAHL databases.
Inclusion criteria were female athletes classified as high-level (e.g., VO2max > 45 mL/kg/min or training > 5 hours per week) collegiate, semi-elite, or elite athletes diagnosed with serum ferritin < 40 mg/L as the primary biomarker for iron deficiency. They included original research studies with primary data relevant to the effect of iron deficiency or iron supplementation on exercise or sports performance. They excluded non-English articles.
The authors used the Downs and Black checklist to assess the quality of the included papers.

What did they find?

The review included 23 studies with 669 high-level female athletes (VO2max > 45 mL/kg/min or training > 5 hours/week) aged 13–47, involved in 16 sports.
Endurance performance declined by 3–4% in iron deficient athletes.
Anaerobic power and strength were inconsistently affected (−23% to +4% for strength; −5% to +9% for power).
Endurance performance improved by 2–20% with daily or bi-daily doses of 100 mg elemental iron.
Maximal aerobic capacity increased by 6–15% with supplementation.
Heterogeneity in outcomes for strength and anaerobic power; benefits more pronounced with severe deficiency (serum ferritin < 16 mg/L).
There were variable statistical methods among studies: the improvement in aerobic metrics was only reported with confidence intervals and effect sizes in some studies.

What are the strengths of the study?

Comprehensive inclusion of studies across various sports and performance levels.
Standardized inclusion criteria (serum ferritin < 40 mg/L).
Rigorous quality assessment (Downs and Black checklist).

What are the weaknesses of the study?

Most studies (78%) had group sizes ≤ 20 athletes, limiting statistical power.
Lack of meta-analysis due to heterogeneity in methods and outcomes.
Limited direct measurement of tissue oxidative capacity and mechanistic insights.
Variability in supplementation protocols between studies and a lack of consistency in dose and duration limits the generalisability of the findings.

Are there any funding issues or conflicts of interest that may influence the findings?

Unclear → No specific funding or conflicts of interest were noted in the paper.

Are the findings useful in application to training and/or coaching practice?

Yes → Findings suggest that iron supplementation is beneficial for endurance athletes with iron deficiency because doing so can enhance training outcomes.
IMPORTANT: this does not mean that you should self-diagnose and take an iron supplement right away; always consult your doctor for a serum ferritin test and advice on when and how to take an iron supplement.

What is my Rating of Perceived scientific Enjoyment?

RP(s)E = 7 out of 10.

The effect of sodium bicarbonate mini-tablets ingested in a carbohydrate hydrogel system on 40 km cycling time trial performance and metabolism in trained male cyclists. Shannon et al. (2024) Eur J Appl Physiol. (click the title to access the full article)

What type of study is in this article?

Randomised controlled trial with crossoverA randomised controlled trial is the “gold standard” approach for determining whether a treatment has a causal effect on an outcome of interest. In such a study, a sample of people that represent the population of interest are randomised to receive the treatment or a no-treatment placebo (control) and the outcome of interest is measured before and after the exposure to treatment/control..

What is the hypothesis or research question?

Does ingesting sodium bicarbonate (NaHCO3) mini-tablets delivered via a carbohydrate (CHO) hydrogel enhance 40 km time trial performance and metabolism in trained male cyclists?

What did the authors do to test the hypothesis or answer the research question?

The authors conducted a randomized, double-blind, crossover trial with 14 trained male cyclists (mean age: 43 ± 15 years; VO2Peak: 51.9 ± 6.4 mL·kg⁻¹·min⁻¹).
Participants completed three trials (familiarization and two experimental 40 km time trials) under two conditions (NaHCO3 supplementation or placebo).
The dose of NaHCO3 was 0.3 g·kg⁻¹ body mass.
Blood acid–base balance, gastrointestinal symptoms, and performance metrics were assessed.

What did they find?

NaHCO3 ingestion improved TT performance by 54.14 ± 18.16 s (p = 0.002; Hedge’s g = 0.22).
Elevated blood bicarbonate (HCO3⁻) and pH pre- and post-exercise (p < 0.001). No significant differences in heart rate, cadence, or VO2 were observed.
Increased blood lactate and CO2 production during NaHCO3 trials (p < 0.01). Respiratory exchange ratio (RER) was higher in the NaHCO3 condition.
Minimal gastrointestinal symptoms were reported with the novel ingestion strategy.

What are the strengths of the study?

Randomised controlled trial with cross-over design (all participants complete all interventions).
Innovative ingestion method (CHO hydrogel with NaHCO3 mini-tablets) reduced common side effects.
Individualized ingestion timing based on peak alkalosis improved methodological rigor.
Comprehensive data on metabolic and physiological outcomes.

What are the weaknesses of the study?

Small sample size (14 participants).
Limited to trained male cyclists; results may not generalize to females, elite athletes, or untrained individuals.
No direct comparison to alternative NaHCO3 delivery methods beyond a placebo.

Are there any funding issues or conflicts of interest that may influence the findings?

Yes → Sodium bicarbonate products were supplied by Maurten AB, Sweden, but the company had no influence on study design, data collection, or analysis.

Are the findings useful in application to training and/or coaching practice?

Yes → The findings demonstrate the practical use of NaHCO3 supplementation with reduced GIS for prolonged, high-intensity cycling, which is potentially useful for athletes aiming to enhance time trial performance with minimal discomfort. However, while the study used strong methodology, the findings are limited by the small sample size and lack of generalizability beyond trained male cyclists.

What is my Rating of Perceived scientific Enjoyment?

RP(s)E = 7 out of 10.

Durability of Running Economy: Differences between Quantification Methods and Performance Status in Male Runners. Zanini et al. (2024) Med Sci Sports Exerc. (click the title to access the full article)

What type of study is in this article?

Observational studyObservational studies can have different types of study designs, including cross sectional, case-control, retrospective cohort, and prospective cohort studies. Typically, an observational study examines a specific cohort of people to characterise them and learn about them; there are no intentional interventions (e.g.,. people are not prescribed a diet). Sometimes the cohort of people is followed over time to determine whether there is a relationship between the natural exposure to a specific variable (e.g. exposure to dietary saturated fat intake) and a specific outcome of interest (e.g. cardiovascular disease)..

What is the hypothesis or research question?

Do different methods of quantifying running economy (energy cost vs. oxygen cost) yield different results during prolonged running?
And, does running economy durability differ between high-performing and low-performing male endurance runners?.

What did the authors do to test the hypothesis or answer the research question?

The study was laboratory-based, within-subject design with repeated measures in 44 male runners (mean VO₂max: 62.4 ml·kg⁻¹·min⁻¹; average 10 km time: 35:50 ± 4:40).
Subgroups: high-performing runners (10 km faster than 33:00) and low-performingrunners (10 km slower than 38:00)..
Participants made 2 visits to the lab:
Visit 1: Incremental treadmill tests to determine lactate threshold and VO₂max.
Visit 2: A 90-minute treadmill run at lactate threshold (LT1) with respiratory gas sampling every 15 minutes. Running economy was measured via energy cost (kcal·kg⁻¹·km⁻¹) and oxygen cost (ml·kg⁻¹·km⁻¹).

What did they find?

High-performing runners had less deterioration in running economy over 90 minutes compared to low-performing runners:
Energy cost change: High-performing runners (+2.3%) vs low-performing runners (+4.3%) at 90 min.
Oxygen cost change: High-performing runners (+2.4%) vs low-performing runners (+4.5%) at 90 min.
Statistical analysis found a significan time × group interactions for both Energy cost and Oxygen cost changes (p<0.01).
The authors concluded that high-performing runners maintain superior running economy durability compared to low-performing runners. Furthermore, the choice between using Energy cost and Oxygen cost has minimal impact on assessing running economy over time.

What are the strengths of the study?

Inclusion of both high- and low-performing endurance runners allowed for meaningful comparisons.
Use of standardized treadmill protocols at lactate threshold ensured consistent metabolic intensity.
Comprehensive statistical analysis with adjustments for body mass loss during the trial.
Large sample size for this type of study (n=44).

What are the weaknesses of the study?

The small absolute changes in running economy limit practical relevance.
Protocol did not assess durations beyond 90 minutes, limiting insights for marathon scenarios and ultra running.
Lack of blinding or randomization in testing procedures.
Differences in prior training mileage between groups could confound results.

Are there any funding issues or conflicts of interest that may influence the findings?

No → There was no external funding and the authors declared no conflicts of interest.

Are the findings useful in application to training and/or coaching practice?

Yes → Due to the observed durability of running economy in high performing runners, the study highlights the importance of consistent high training mileage for enhancing durability. However, despite the well-structured and relevant study design, there are limited practical insights for marathon or ultra-endurance contexts and a lack of diversity in participant demographics.

What is my Rating of Perceived scientific Enjoyment?

RP(s)E = 8 out of 10.

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All the other interesting papers I found this month are below.

You can dig in and evaluate the authors’ findings by clicking on the titles to access the full papers.

Learn to critically evaluate each paper using the framework I used for my favourite papers.

General training methods.

Reliability and Validity of Predicted Performance in the Severe-Intensity Domain From the 3-Minute All-Out Running Test. Busso et al. (2024 ) Int J Sports Physiol Perform.

Durability of Running Economy: Differences between Quantification Methods and Performance Status in Male Runners. Zanini et al. (2024 ) Med Sci Sports Exerc.

A Snapshot of Vitamin D Status, Performance, Blood Markers, and Dietary Habits in Runners and Non-Runners. Pegreffi et al. (2024 ) Nutrients.

Consumption of a Branched-Chain Amino Acids-Containing Sports Beverage During 21 km of Running Reduces Dehydration, Lowers Muscle Damage, and Prevents a Decline in Lower Limb Strength. Liang et al. (2024 ) Nutrients.

Power or speed: Which metric is more accurate for modelling endurance running performance on track? Ruiz-Alias et al. (2024 ) Eur J Sport Sci.

Polarized running training adapted to versus contrary to the menstrual cycle phases has similar effects on endurance performance and cardiovascular parameters. Kubica et al. (2024 ) Eur J Appl Physiol.

Sports nutrition and hydration.

Assessment of Urolithin A effects on muscle endurance, strength, inflammation, oxidative stress, and protein metabolism in male athletes with resistance training: an 8-week randomized, double-blind, placebo-controlled study. Zhao et al. (2024 ) J Int Soc Sports Nutr.

Protein expression changes in Tibetan middle-to-long distance runners after the transition from high altitude to low altitude: Implications for enhancing endurance training. Wang et al. (2024 ) Sports Med Health Sci.

The effects of a sugar-free amino acid-containing electrolyte beverage on 5-kilometer performance, blood electrolytes, and post-exercise cramping versus a conventional carbohydrate-electrolyte sports beverage and water. McIntosh et al. (2024 ) J Int Soc Sports Nutr.

Towards Precision Sports Nutrition for Endurance Athletes: A Scoping Review of Application of Omics and Wearables Technologies. Bedrač et al. (2024 ) Nutrients.

Use of Carbohydrate (CHO), Gluten-Free, and FODMAP-Free Diets to Prevent Gastrointestinal Symptoms in Endurance Athletes: A Systematic Review. Montero-Carrasco et al. (2024 ) Nutrients.

Male Endurance Athletes: Examination of Energy and Carbohydrate Availability and Hormone Responses. Moore et al. (2024 ) Nutrients.

Sports supplements.

Creatine supplementation protocols with or without training interventions on body composition: a GRADE-assessed systematic review and dose-response meta-analysis. Pashayee-Khamene et al. (2024 ) J Int Soc Sports Nutr.

Effect of caffeine ingestion on time trial performance in cyclists: a systematic review and meta-analysis. Chen et al. (2024 ) J Int Soc Sports Nutr.

Iron deficiency, supplementation, and sports performance in female athletes: A systematic review. Pengelly et al. (2024 ) J Sport Health Sci.

Effects of Creatine Supplementation and Resistance Training on Muscle Strength Gains in Adults <50 Years of Age: A Systematic Review and Meta-Analysis. Wang et al. (2024 ) Nutrients.

Recovery (including sleep).

The Efficacy of Non-Steroidal Anti-Inflammatory Drugs in Athletes for Injury Management, Training Response, and Athletic Performance: A Systematic Review. Pham et al. (2024 ) Sports (Basel).

Athlete health (including mental health).

Training with reduced carbohydrate availability affects markers of bone resorption and formation in male academy soccer players from the English Premier League. Stables et al. (2024 ) Eur J Appl Physiol.

Does Relative Energy Deficiency in Sport (REDs) Syndrome Exist? Jeukendrup et al. (2024 ) Sports Med.

Use of Carbohydrate (CHO), Gluten-Free, and FODMAP-Free Diets to Prevent Gastrointestinal Symptoms in Endurance Athletes: A Systematic Review. Montero-Carrasco et al. (2024 ) Nutrients.

Mental health matters: Evaluating the preparedness of sport psychologists to incorporate within their role. Winter et al. (2024 ) Eur J Sport Sci.

Sport practice and depression during adolescence: Special emphasis on performance level and sport discipline. Sitko et al. (2024 ) J Sci Med Sport.

Injury and rehab.

Co-creation of injury prevention measures for competitive adolescent distance runners: knowledge, behavior, and needs of athletes and coaches enrolled on England Athletics' Youth Talent Programme. Mann et al. (2024 ) Ann Med.

Addressing muscle-tendon imbalances in adult male athletes with personalized exercise prescription based on tendon strain. Weidlich et al. (2024 ) Eur J Appl Physiol.

Risk factors for running-related injuries: An umbrella systematic review. Correia et al. (2024 ) J Sport Health Sci.

Female athlete physiology and sex differences.

Influence of Menstrual-Cycle Phase on Sleep and Recovery Following High- and Low-Intensity Training in Eumenorrheic Endurance-Trained Women: The Female Endurance Athlete Project. Taylor et al. (2024 ) Int J Sports Physiol Perform.

Female Athlete Sport Science Versus Applied Practice: Bridging the Gap. Burden et al. (2024 ) Int J Sports Physiol Perform.

The Effects of Social Support on Athlete Burnout and Well-Being in Female Collegiate Athletes. Gray et al. (2024 ) J Sport Rehabil.

The Menstrual Health Manager (MHM): A Resource to Reduce Discrepancies Between Science and Practice in Sport and Exercise. Badenhorst et al. (2024 ) Sports Med.

And, to help you wash down the latest evidence, here's a snifter from my recent indulgence...

My beer of the month.

Peanut Butter Brownie Imperial Stout.
brewery

Brewed by Mallassepät (Naantali, Finland).
type of beer

Double pastry stout.
strength

12% ABV.

Peanut buttery, slightly roasted, and malty, rich, and ever-so-slightly bready. Mallassepät know exactly how to tingle my senses.

RP(be)E(r)
(Rating of Perceived beer Enjoyment)
8 out of 10

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Disclaimer: I occasionally mention brands and products but it is important to know that I am not affiliated with, sponsored by, an ambassador for, or receiving advertisement royalties from any brands. I have conducted biomedical research for which I have received research money from publicly-funded national research councils and medical charities, and also from private companies, including Novo Nordisk Foundation, AstraZeneca, Amylin, A.P. Møller Foundation, and Augustinus Foundation. I’ve also consulted for Boost Treadmills and Gu Energy on their research and innovation grant applications and I’ve provided research and science writing services for Examine — some of my articles contain links to information provided by Examine but I do not receive any royalties or bonuses from those links. These companies had no control over the research design, data analysis, or publication outcomes of my work. Any recommendations I make are, and always will be, based on my own views and opinions shaped by the evidence available. My recommendations have never and will never be influenced by affiliations, sponsorships, advertisement royalties, etc. The information I provide is not medical advice. Before making any changes to your habits of daily living based on any information I provide, always ensure it is safe for you to do so and consult your doctor if you are unsure.