The running science nerd alert.
February 2024
Learn to train smart, run fast, and be strong with Thomas Solomon PhD 
Here are this month's latest research studies on running-related exercise and nutrition science.
The studies are divided into sub-topics — training methods, sports nutrition, supplements, recovery, athlete health, injuries, and female athletes, etc. Plus, there’s my beer of the month.
I’ve provided a brief conclusion from each study but click on the study title to go deep and read the full paper.
My favourite paper this month.
Mathematical model: Assessing exogenous carbohydrate intake needed to optimize human endurance performance across sex: Insights from modeling runners pursuing a sub-2-hour marathon. Lukasiewicz et al. (2024) J Appl Physiol.
“ The present study aimed to scrutinize the overall efficacy of existing nutritional guidelines for elite male and female marathon runners in pursuit of a sub2 marathon, as well as to explore potential sex-specific biases inherent in these recommendations. Key findings reveal that 65% of modeled male and female runners would require exogenous carbohydrate intakes exceeding the current upper limit of 90 grams per hour to successfully complete a sub2 marathon. Furthermore, these guidelines appear to be twice as suitable for male runners, satisfying 47% of modeled needs, compared to only 23% for female runners. This underscores a potential yet notable inadequacy in current nutritional guidelines for all elite endurance athletes, but particularly for females. Given these disparities, there is a more pressing need for future research to prioritize the inclusion of female athletes, thereby fostering a more equitable and optimized approach to endurance performance.”
Training methods.
Systematic review: Assessing anaerobic speed reserve: A systematic review on the validity and reliability of methods to determine maximal aerobic speed and maximal sprinting speed in running-based sports. Thron et al. (2024) PLoS One. “ Beyond assessing single performance parameters, the anaerobic speed reserve can provide further insights into an athlete’s physiological and neuromuscular profile by considering the individual tolerance to high-intensity exercise. As anaerobic speed reserve consists of the parameters maximal aerobic speed and maximal sprinting speed, the methods to assess these parameters need to be valid and reliable.Maximal aerobic speed can be defined during cardiopulmonary exercise testing, yet there are different testing protocols without a consensus about the most appropriate one. Due to physiological considerations based on energy supply, the speed at the onset of the VO2-plateau seems to be the most appropriate method to determine true maximal aerobic speed. For field tests, studies’ results on validity are heterogeneous and do not favor a specific field test (incremental continuous or shuttle runs) for the determination of maximal aerobic speed. However, results on time trials indicate that distances adapted to the subjects’ sporting background, fitness or sex might be suitable to estimate maximal aerobic speed.
Regarding maximal sprinting speed, linear sprints using timing gates or video analysis seem to provide valid and reliable results besides the gold standard method, i.e. radar or laser measurements. The validity of GPS or sprinting on a treadmill cannot be confirmed. Sprinting distances between 20 and 40 m should be selected for recreational subjects or type of sports in which shorter sprints are crucial, e.g. team sports, whereas trained track and field sprinters might need longer total distances (40 to 70 m) to reach maximal sprinting speed.
In particular the use for prescribing training emphasizes the importance of valid and reliable measurements of maximal aerobic speed and maximal sprinting speed to achieve optimal and desired intensity based on anaerobic speed reserve. Methods–ideally with a low measurement error and therefore a high reliability–should be maintained throughout the training routine so that changes in anaerobic speed reserve can be attributed to changes in the individual performance and not to differing results because of the testing method. ”
Narrative review: Combining Heat and Altitude Training to Enhance Temperate, Sea-Level Performance. Girard et al. (2024) Int J Sports Physiol Perform. “ Despite evidence supporting environment-specific physiological adaptations, a synthesis of the current literature suggests that the addition of simultaneous heat and hypoxia does not enhance performance more than training with either thermal or hypoxic stimuli or temperate training alone. It is noteworthy that these conclusions are drawn from a restricted number of intervention studies. Future studies are required to determine the potential benefits of conducting heat and altitude exposure either simultaneously (ie, in close proximity in a session), concurrently (ie, within the same training block but not at the same time), or sequentially (ie, one after the other, to maximize adaptative responses over a sequential week or training block), likely requiring careful periodization.”Sports nutrition.
Mathematical model: Assessing exogenous carbohydrate intake needed to optimize human endurance performance across sex: Insights from modeling runners pursuing a sub-2-hour marathon. Lukasiewicz et al. (2024) J Appl Physiol. “ The present study aimed to scrutinize the overall efficacy of existing nutritional guidelines for elite male and female marathon runners in pursuit of a sub2 marathon, as well as to explore potential sex-specific biases inherent in these recommendations. Key findings reveal that 65% of modeled male and female runners would require exogenous carbohydrate intakes exceeding the current upper limit of 90 grams per hour to successfully complete a sub2 marathon. Furthermore, these guidelines appear to be twice as suitable for male runners, satisfying 47% of modeled needs, compared to only 23% for female runners. This underscores a potential yet notable inadequacy in current nutritional guidelines for all elite endurance athletes, but particularly for females. Given these disparities, there is a more pressing need for future research to prioritize the inclusion of female athletes, thereby fostering a more equitable and optimized approach to endurance performance.” Pre-clinical study in rodents (this caught my eye because the authors were interested in the effects of pale ale craft beer on running performance; however, since the study is in rats, don’t make any changes to your practice based on its findings): Enhancing satiety and aerobic performance with beer microparticles-based non-alcoholic drinks: exploring dose and duration effects. Cahuê et al. (2024) Front Nutr. “ In summary, our study reveals that prolonged utilization of non-alcoholic PABM-based beverages led to a notable enhancement in exercise performance for up to 4 weeks, yet this effect was mitigated by an extended 8-week regimen, displaying a clear dose-dependent pattern. Intriguingly, the ingestion of beer microparticles corresponded to a reduction in food intake, all while maintaining body weight. To comprehensively elucidate the intricate interplay underlying the augmentation of exercise performance and regulation of food consumption, a deeper exploration into the molecular mechanisms is necessary.” Randomised controlled trial: Ad libitum ice slurry ingestion and half-marathon performance in a hot environment: A study comparing the effects of the amount and moment of ingestion between ice slurry and water at 37 °C. Andrade et al. (2024) J Therm Biol. “ Under the investigated conditions, the athletes ingest less ad libitum ice slurry than ad libitum 37 °C water. Moreover, ad libitum ice slurry ingestion does not affect performance and physiological/perceptual variables measured during a self-paced 21.1 km run under environmental heat stress. However, we provide preliminary evidence that a lower beverage ingestion (either ice slurry or warm water) may improve performance during a simulated half marathon in a hot environment than when a higher amount was ingested. Interestingly, ingesting less beverage does not lead to more significant dehydration, as evidenced by similar plasma osmolality after exercise in all four experimental trials.” Systematic review and meta-analysis: The effect of pre-exercise oral hyperhydration on endurance exercise performance, heart rate and thermoregulation: a meta-analytical review. McCubbin et al. (2024) Appl Physiol Nutr Metab. “ In conclusion, pre-exercise hyperhydration appears to have a small, beneficial effect on performance in endurance time-to-exhaustion and time-trial (time-to-completion) tasks, predominately during cycling exercise in male, recreational and trained (but not elite) athletes. No clear benefit of hyperhydration was seen for total work tasks. These findings appear independent of the method of hyperhydration used, fluid volume consumed, or ambient conditions. This strategy however is not well studied in elite athletes, especially females and in running-based activities. More research in these population groups and performance tasks are warranted, with more ecologically valid differences in pre-exercise fluid intake between intervention and comparator groups.” Randomised controlled trial: The effects of carbohydrate availability on cycling endurance at the maximal lactate steady state. Quinn et al. (2024) Am J Physiol Regul Integr Comp Physiol. “ The maximal lactate steady state (MLSS) is an important threshold for exercise performance, testing, and training. This study demonstrates that MLSS is not limited by carbohydrate availability under typical conditions, as carbohydrate loading did not improve time-to-task-failure at the MLSSp; however, recent, intense exercise attenuated the time-to-task-failure at MLSS, indicating that carbohydrate may limit performance when availability is inadequate. Metabolic responses to exercise at the MLSS (e.g., blood lactate, respiratory exchange ratio, and substrate oxidation) were impacted by carbohydrate availability; however, blood lactate stability was unaffected such that only the reduction in time-to-task-failure hindered MLSS determination. With relevance to sports nutrition guidelines and exercise testing protocols, our results suggest that minor differences in diet and exercise are unlikely to affect MLSS determination but that recent strenuous exercise should be avoided prior to MLSS determination, particularly if proper refueling strategies are neglected.”Supplements.
Randomised controlled trial: Effect of Personalized Sodium Replacement on Fluid and Sodium Balance and Thermophysiological Strain During and After Ultraendurance Running in the Heat. McCubbin et al. (2023) Int J Sports Physiol Perform. “ Complete, personalized replacement of sweat sodium losses during 5-hour continuous running in the heat appears to have minimal impact on thirst, ad libitum water intake, net water balance, and body water shifts between compartments and no impact on thermophysiological strain. Furthermore, when water is consumed ad libitum, sodium replacement increases plasma sodium and plasma osmolality rather than preventing its decline. There was no evidence for release of osmotically inactive sodium stores in response to a large sodium deficit incurred during running, when such a deficit is not accompanied by large reductions in total body water or plasma volume. Net sodium loss during exercise causes a substantial postexercise renal sodium conservation, although in ultraendurance exercise this is inadequate to fully restore sodium balance within 24 hours without deliberately increased postexercise sodium intake.” Systematic review and meta-analysis: Effects of Beetroot-Based Supplements on Muscular Endurance and Strength in Healthy Male Individuals: A Systematic Review and Meta-Analysis. Evangelista et al. (2024) J Am Nutr Assoc. “ In conclusion, the results of this systematic review with meta-analysis reveal that acute or short-term beetroot-based supplement administration seems to be a useful intervention to improve muscular endurance (particularly in isotonic exercises) and muscular strength (particularly in fatigued state) in healthy male individuals. The ergogenic effect does not seem to be affected by training level, muscle group involved, supplemented nitrate dose, or supplementation frequency do not affect the results.” Systematic review and meta-analysis: Effects of caffeine ingestion on cardiopulmonary responses during a maximal graded exercise test: a systematic review with meta-analysis and meta-regression. Marinho et al. (2024) Crit Rev Food Sci Nutr. “ The findings of the present meta-analysis indicate that caffeine provokes a small increase in VĖ peak and time to exhaustion during graded-exercise tests, without a significant effect on other cardiopulmonary variables (including peak oxygen uptake, peak heart rate, peak blood lactate concentration, peak tidal volume, peak breathing frequency, or peak power output).” Systematic review: Effect of Probiotic Supplementation on Gut Microbiota and Sport Performance in Athletes and Physically Active Individuals: A Systematic Review. Porepp et al. (2024) J Diet Suppl. “ Our findings suggest that probiotics are a promising alternative and complementary tool for athletes and physically active individuals, as they may improve sports performance, physiological parameters, and post-exercise recovery, through the improvement of biochemical parameters linked to inflammation. However, the high risk of bias and different methodologies used in the included studies is an important limitation for the analysis of our results and should be taken into consideration. Also, well-conducted randomized controlled trials, with pre-registered protocols, larger samples, and possibly with closer dietary monitoring, are needed to increase the quality and certainty of the evidence.”Recovery (inc. sleep).
Systematic review and meta-analysis: Effects of photobiomodulation therapy on the functional performance of healthy individuals: a systematic review with meta-analysis. Bezerra et al. (2024) Lasers Med Sci. “ In summary, this systematic review with meta-analysis indicates that photobiomodulation therapy demonstrates a moderate improvement in reducing fatigue when compared to placebo treatment. However, when it comes to enhancing strength and improving functional capacity in healthy individuals, the evidence remains inconclusive, with confidence levels ranging from very low to moderate. As such, further clinical trials are warranted to thoroughly investigate the potential impact of photobiomodulation therapy on strength and functional capacity.”Athlete health (inc. mental health).
Narrative review: Direct and indirect impact of low energy availability on sports performance. Melin et al. (2024) Scand J Med Sci Sports. “ In conclusion, more research needs to be done to fully understand the effects of low energy availability on different physiological systems and how the interplay of these may ultimately affect physical capacity and athletic performance. Severe low energy availability exposure has the potential to be a serious problem leading to impaired sports performance, most likely mediated through direct/indirect health effects, hormonal alterations, and suboptimal levels of energy substrate (i.e., muscle glycogen). Therefore, athletes who desire to optimize body mass and body composition (and use low energy availability to achieve those goals) to improve competitive performance should emphasize the use of well-planned and supervised gradual weight-loss methodologies with moderate low energy availability exposure to maintain health and performance. These athletes should also have baseline medical and psychological assessment to ascertain whether there is undue risk to even undertake body mass or body composition changes. That said, the coach and athlete support team (e.g., physiotherapist, physician) must remain vigilant of the athletes' responses and health status to ensure the prevention of Relative Energy Deficiency in Sport (REDs).
Severe low energy availability exposure in athletes increases the risk for the development of REDs and associated health consequences of both a physiological and psychological nature. Current nutritional status, as well as optimal muscle protein synthesis are important factors for maximizing training adaptations, as well as improving immune function, wound healing, and rehabilitation of musculoskeletal injuries in athletes. Hence, monitoring, detection, and treatment of athletes with exposure to severe low energy availability in the sports medicine setting will potentially improve athletes' health and ultimately performance, as well as their rehabilitation process from illness and injuries.”
Injury and rehab.
Systematic review: Risk Factors for Running-Related Injury in High School and Collegiate Cross Country Runners: A Systematic Review. Joachim et al. (2023) J Orthop Sports Phys Ther. “ Findings: A runner’s sex and history of injury, both of which are non-modifiable, had the strongest evidence for being potential predictors of running-related injury in high school and collegiate cross country runners. There was moderate evidence indicating increased Relative Energy Deficiency in Sport (REDs) risk factors (e.g. menstrual dysfunction, poor bone health) may be associated with increased risk of running-related injury. Implications: The most likely risk factors for running-related injury are non-modifiable. There is a significant need for more research in high school and collegiate runners to determine modifiable risk factors for running-related injury and guide future interventional studies. Caution: High-quality research on modifiable risk factors for running-related injury in this population is lacking and the present findings are supported by few studies.” Systematic review and meta-analysis: Do Exercise-Based Prevention Programs Reduce Injury in Endurance Runners? A Systematic Review and Meta-Analysis. Wu et al. (2024) Sports Med. “ Injury prevalence is high in endurance runners; however, the research investigating the use of exercise to reduce injury risk specifically in endurance runners has not been reviewed adequately. Pooled data showed that exercise-based injury prevention programs provide no reduction in injury risk or injury rate compared to running only. Studies that used an element of supervision during interventions tended to have greater compliance with the exercise programs and showed significantly lower injury risk compared to control groups. Most studies in this area are of low quality, indicating that future research should use more robust study designs with supervised exercise interventions.”Female athletes and sex differences.
Randomised controlled trial: Low Energy Availability Followed by Optimal Energy Availability Does Not Benefit Performance in Trained Females. Oxfeldt et al. (2024) Med Sci Sports Exerc. “ We found that 10 days of low energy availability in trained females resulted in impaired muscle function, repeated sprint ability, and 4-min time trial performance (absolute values), with concomitant reductions in muscle glycogen. Two days of recovery with optimal energy availability only partially restored these impairments, although some measures of physical performance (absolute values) remained inferior to being in optimal energy availability the whole period. Importantly, when performance outcomes were normalized to body mass, no superior effect was observed following a period of low energy availability. Together, these results challenge the common perception that a small reduction in body mass will lead to an improved power-to-mass ratio and, thus, increased physical performance.” Systematic review and meta-analysis: The Influence of Menstrual Cycle Phases on Maximal Strength Performance in Healthy Female Adults: A Systematic Review with Meta-Analysis. Niering et al. (2024) Sports (Basel). “ Overall, it can be concluded that the early follicular phase is unfavorable for all three tested maximal strength classes during the menstrual cycle. The late follicular phase is the optimal time for peak performance in isometric maximal strength, while the late luteal phase, likely due to low estrogen levels, is the least suitable. In contrast, isokinetic maximal strength is low during the late follicular phase, while the ovulatory phase is the best time according to the included studies, probably due to the increase in luteinizing hormone, which also stimulates testosterone availability. The late follicular phase appears to be the most conducive time for achieving dynamic maximal strength, possibly because of the high levels of estrogen present. Conversely, the mid-luteal phase is considered the least suitable time for optimal muscle function, due to decreased levels of estrogen (reduced neuromuscular facilitation) and increased levels of progesterone (decreased neuromuscular/synaptic transmission). This hormonal shift, as identified by Tenan et al., suggests a potential reduction in maximal force generation during this phase, further influenced by the complex interplay with luteinizing hormone and its role in testosterone production.
The large variance among studies may be due to several methodological factors, the limited number of participants (Ø n = 19.7), and the associated high sample variance. Characteristics of participants, including sports history and related experience, may have also contributed to the significant heterogeneity observed between studies. On average, the studies investigated three conditions and involved fewer than 20 participants, leading to small effects.
The query arises as to who would benefit from discerning the nuanced variation in maximal strength performance during the menstrual cycle. In this regard, female competitive athletes are particularly pertinent. Thus, future studies should consider them as a distinct target population by incorporating more uniform participants to enhance result comparability. This review is the first to examine and identify differences in the three categories of maximal strength. However, none of the included studies examined the difference between all three categories, which could be a focus for future studies. Further attention should also be devoted to achieving high study quality, including implementing a suitable method for determining the correct menstrual cycle phase and conducting an a priori power analysis to optimize effect sizes and increase the informative value of the results. In particular, the late follicular phase and measurements of maximal dynamic strength should be given more attention in future studies. Due to the advantages in the hormonal regulation of this phase, especially during explosive movements, a transfer to sports-specific applications could be possible. The primary goal should be to obtain meaningful results that can inform practical recommendations, potentially also including those relevant to amateur athletes.”
And, to help you wash down the latest evidence, here's a snifter from my recent indulgence...
What is the beer called? Toasted Coconut Lemon Drizzle Doughnut.
Which brewery made it? Vault City Brewing (Edinburgh, UK).
What type of beer is it? Sour (Smoothie / Pastry).
How strong is the beer? 4.1% ABV.
How would I describe this beer?
Lemony and donuty and soury and amazingy. I was lost for words.
What is my Rating of Perceived beer Enjoyment?
RP(be)E(r) = 8½ 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.