The running science nerd alert.
December 2023
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.
Scoping review: Barriers and enablers influencing female athlete return-to-sport postpartum: a scoping review. Tighe et al. (2023) Br J Sports Med.
“ This review synthesised existing literature to identify barriers and enablers that can influence female athletes successful return-to-sport postpartum. This will help guide the development of evidence-based policies that support female athletes during this unique life stage, as few of these policies currently exist. Postpartum recovery time, time to manage motherhood and sport demands, sport organisation policies, stereotypes and social support were identified as the most significant of factors to influence female athletes successful return-to-sport postpartum. Moreover, paid maternity leave offering job security, travel support for carer and child and affordable and accessible childcare are critical policy inclusions to appropriately support female athletes in their return-to-sport postpartum. In addition to policy development, various opportunities exist for clinicians and sport organisations to better support postpartum athletes. To build on the current body of evidence, future research should adopt standardised definitions of the ‘postpartum period' and ‘athlete’ as well as report time taken to return-to-sport and the level of sport athletes returned to postpartum.. ”
Training methods.
Systematic review and meta-analysis: The Effect of Pre-Exercise Hyperhydration on Exercise Performance, Physiological Outcomes and Gastrointestinal Symptoms: A Systematic Review. Jardine et al. (2023) Sports Med. “ The main finding was that hyperhydration can improve exercise capacity, potentially due to an increase in plasma volume that may aid in reducing heart rate and core temperature when exercising at a constant work rate to exhaustion, although it must be acknowledged that not all studies measured changes in plasma volume which provides scope for further investigation. Future research should investigate the effects of hyperhydration on exercise performance in more practical settings (e.g. field studies or competitive events) using valid and reliable protocols (i.e. time-trials) in thermally challenging conditions using different modalities (e.g. endurance running) with a strong level of control. The effect of different phases of the menstrual cycle on key outcome variables in females (e.g. fluid retention and core temperature) remains to be adequately investigated and represents the next immediate priority area for this research area. ” Randomised controlled trial: Aerobic high-intensity intervals improve VO2max more than supramaximal sprint intervals in females, similar to males. Helgerud et al. (2023) Scand J Med Sci Sports. “ In conclusion, high-intensity interval training improves VO2max more than sprint interval training with both long and short recovery periods in aerobically well-trained females, while sprint interval training improves sprint running performance more than high-intensity interval training. Treadmill running sprint interval training 10 × 30 s induced an unacceptable rate of muscular strains, and it should therefore be carefully considered if applying this treadmill protocol is necessary. ” Observational study: Correlation properties of heart rate variability to assess the first ventilatory threshold and fatigue in runners. Van Hooren et al. (2023) J Sports Sci. “ Our findings show that a DFA-a1 (a non-linear heart rate variability index) of 0.75 during an incremental exercise ramp was closely related to the gas exchange VT1 (ventilatory threshold 1), with the accuracy at an individual level being comparable to the accuracy of other methods for VT1 determination. These findings therefore add further validation to the concept of using heart rate variability threshold (HRVT) for exercise intensity demarcation. An important novelty to previous studies that typically used ECG or cycling, is that we used a commercial heart rate (variability) chest belt during a treadmill run, which better reflects in-field conditions for runners. We also observed a shift in agreement between the VO2 and heart rate at HRVT during a second ramp, indicating that the DFA-a1 derived correlation properties of heart rate variability are sensitive to fatigue, which may therefore be used to guide exercise and training prescription. Nevertheless, further (hardware) improvements are required to ensure robust functioning of this method across all individuals. ” Systematic review and meta-analysis: Quantifying demands on the hamstrings during high-speed running: A systematic review and meta-analysis. McNally et al. (2023) Scand J Med Sci Sports. “ Faster running intensity/speed places higher activation and higher kinetic demands on the hamstring muscles. Joint moments to which the hamstrings contribute also increase with increasing running speed, although some intersubject variability exists. While concerns about reporting and methodological quality prevent firm conclusions regarding the magnitude of hamstring demands, clinicians may still find the data presented here to be of value in training, testing, and return to play decision-making strategies. Future research on activation (particularly muscle functional magnetic resonance imaging) and kinetic (particularly rate of moment development) measures is warranted to further enhance our understanding of the demands on hamstring muscles of healthy individuals during high-speed running. ” Observational study: Effects of a Regular Endurance Training Program on Running Economy and Biomechanics in Runners. Rodriguez-Barbero et al. (2023) Int J Sports Med. “ Based on these findings, we recommend that coaches and athletes should complete a performance test after an 8-week endurance training program to monitor physiological changes. Tracking cardiometabolic parameters appears to be more crucial than evaluating mechanical parameters, as the only observed gait pattern changes were in the recreational runners, specifically related to neuromuscular stiffness and ground contact time. Therefore, monitoring the cardiometabolic responses can provide valuable insights into the effectiveness of the training program and the athletes’ overall performance. ” PhD thesis: Running footwear matters: decoding the influence of running shoe characteristics on physiology, biomechanics and running performance. Carranza et al. (2023) Br J Sports Med. “ Advanced footwear technology improved the performance of the top 100 runners in 10k, half marathon and marathon, also improving the critical speed, however, it did not equally improve the performance of all runners. General recommendations suggest a shoe life range between 400 km and 500km for racing shoes, such as advanced footwear technology. However, our results demonstrate different changes in advanced footwear technology with PEBA and EVA midsole properties after 450km of road running, leading to changes in running economy and minor kinematic adaptations. Therefore, shoe companies could create advanced footwear technology with EVA midsole for training offering longer shoe life and design advanced footwear technology with PEBA and full curved carbon fibre plate for competition days to improve running performance. ” Randomised controlled trial: Independent, additive and interactive effects of acute normobaric hypoxia and cold on submaximal and maximal endurance exercise. Callovini et al. (2023) Eur J Appl Physiol. “ The combination of cold (−20 °C) and hypoxia (≈3500 m) exerted additive rather than synergistic effects on exercise performance, decreasing LT and maximal exercising workload to an extent that is equal to the sum of the two stimuli alone. Both exclusive effects of hypoxia (i.e., maximal and submaximal SpO, submaximal Rf and RPE at LT) and cold (i.e., submaximal Vt and TS) and different additive (i.e., maximal and LT HR, Ve max) and synergistic (i.e., TSmax and Ve at LT) effects of the two stressors were found on the investigated maximal and submaximal physiological and perceptual variables. Future studies should (i) better understand the magnitude of influence of cold induced bronchoconstriction on exercise performance, especially when combined to acute hypoxic ventilatory response and (ii) consider combined cold and hypoxic effect on performance when also a significant reduction in core and muscle temperature is expected, accurately measuring these parameters. These results provide new insight into human responses to exercise in cold and hypoxic environments, highlighting the need for careful consideration of independent and combined stressor impact on considered variables for optimal exercise intensity prescription and training load monitoring in athletes training/competing in hypoxic and/or cold environments. ” Randomised controlled trial: Partial-body cryostimulation procured performance and perceptual improvements in amateur middle-distance runners. De Nardi et al. (2023) PLoS One. “ A single partial-body cryostimulation session may represent a favorable set-up routine before running, improving middle-distance running performance and reducing RPE for the same external effort also in moderate-temperature conditions. Future studies should investigate the optimal integration of partial-body cryostimulation with the traditional elements of active of pre-exercise routines, so to maximize middle-distance performance. ”
Supplements.
Systematic review and meta-analysis: Effect of Soy Protein Supplementation on Muscle Adaptations, Metabolic and Antioxidant Status, Hormonal Response, and Exercise Performance of Active Individuals and Athletes: A Systematic Review of Randomised Controlled Trials. Zare et al. (2023) Sports Med. “ This systematic review reveals that soy proteins may increase lean mass during resistance training similarly to whey protein; nevertheless, certain studies indicate that milk and whey proteins may be preferable for increasing lean mass at a faster rate. When compared with whey protein, maltodextrin or placebo, the evidence suggests that long-term soy protein supplementation along with exercise training may boost antioxidant defence and limit lipid peroxidation. In terms of its effects on hormonal response, there are often contradictory findings regarding the effect of soy protein supplementation on testosterone and cortisol levels, and on biomarkers associated with muscle androgenic or estrogenic signalling. While soy protein supplementation in athletes/active individuals is promising, the studies included in the review have several limitations, such as heterogeneity of interventions, exercises performed, exercise intensities and frequency and timing of protein intake. Therefore, future studies adjusting total daily protein intake as ~ 1.6 g/protein, including both leucine-matched and dose-matched protein administration, and ≥ 12 weeks of training protocols along with the supplementation are needed. Finally, more research is needed to elucidate the body compositional and exercise performance effects of soy proteins compared to other proteins in different states of energy balance (i.e. sustained hypo- and hypercaloric conditions). ” Systematic review and meta-analysis: Effects of citrulline on endurance performance in young healthy adults: a systematic review and meta-analysis. Harnden et al. (2023) J Int Soc Sports Nutr. “ With the addition of two studies published in 2020, it was felt there was sufficient evidence surrounding citrulline supplementation and endurance performance to perform a systematic review and meta-analysis to pool and summarize the results. Two meta-analyses were performed as it was deemed inappropriate to combine the results of the two observed outcome measures, time-to-exhaustion and time-to-completion. The results of the meta-analyses indicate that acute citrulline supplementation does not significantly improve the endurance performance measures, time-to-exhaustion (pooled standardised mean difference = 0.03 [−0.27, 0.33]) and time-to-completion (pooled standardised mean difference = −0.07 [−0.39, 0.26]), in comparison to control in young healthy adults. The small number of included studies prevented further subgroup analyses. In the context of other evidence, these results are not surprising. ” Randomised controlled trial: Effects of Specific Bioactive Collagen Peptides in Combination with Concurrent Training on Running Performance and Indicators of Endurance Capacity in Men: A Randomized Controlled Trial. Jerger et al. (2023) Sports Med Open. “ In summary, the results of this placebo-controlled trial showed that specific collagen peptides supplementation in combination with concurrent training (a combination of resistance and endurance training) improved indicators of endurance capacity in response to a 12-week concurrent training program in recreationally active men. The main result was a significant improvement in a 1-h time trial by 15%. In addition, the velocity at the aerobic and individual anaerobic threshold increased significantly in the participants receiving 15 g specific collagen peptides on a daily basis. Therefore, daily supplementation with specific collagen peptides could positively enhance the adaptions of a concurrent resistance and endurance training program, which are often lower compared to isolated endurance or strength training due to the interference effect. The results could potentially be explained by an improved aerobic capacity or structural adaptations within the musculotendinous structures, or a combination of both effects. However, this needs to be confirmed and further investigated by forthcoming studies. ”
Recovery (inc. sleep).
Narrative review: Dawn of a New Dawn: Advances in Sleep Health to Optimize Performance. LaGoy et al. (2023) Sleep Med Clin. “ Recent advances in commercially available sleep tracking devices have allowed for enhanced sleep monitoring capabilities, that, when combined with advances in biomathematical modeling may inform targeted performance optimization strategies. When sufficient sleep cannot be obtained, evidence-based use of sleep banking, caffeine, and light may attenuate performance deficits over an acute period. When considering implementation of sleep health interventions in real-world settings, barriers to implementation specific to the population of interest must be considered. ”
Athlete health (inc. mental health).
Observational study: "I RUN CLEAN Project"-An Innovative and Self-Sustainable Approach to Develop Clean Sport Behaviours in Grassroots Athletes. Codella et al. (2023) Eur J Investig Health Psychol Educ. “ Values-based anti-doping interventions are highly warranted to promote clean sport behaviours at the elite, grassroots and community levels. The efficacy of the tools developed in the European Athletics I Run Clean project is essential for expanding its impact and outreach. This study confirms the quality of the project design and delivery, and these confirmations can be used as leverage when engaging athletic federations outside of the project consortium and other potential partners in Europe and beyond. ”
Injury and rehab.
Systematic review and meta-analysis: The Effects of Exercise-Based Injury Prevention Programmes on Injury Risk in Adult Recreational Athletes: A Systematic Review and Meta-Analysis. Liddle et al. (2023) Sports Med. “ The use of exercise-based injury prevention programmes is a growing research area given the prevalence of injury in athletes at all levels. Our primary finding was that there is insufficient evidence to support the idea that exercise-based injury prevention programmes are effective in reducing injury risk for adult recreational populations. Our review is the first to synthesise the effects of exercise-based injury prevention programmes in a variety of sports, involving adult recreational participants. Our results support the need for further development and appropriate implementation of exercise-based injury prevention programmes by practitioners, specifically in sports other than soccer. Researchers might concentrate on larger studies and programmes for non-contact sports such as running, which is a highly popular recreational activity but has received limited attention in the scientific literature. Furthermore, the development of programmes that focus on high reward for little time commitment presents a potential strategy to enhance adherence. Given the added information and statistical precision that time-to-event survival analyses ofer, future research may also beneft from adoption of this design and analysis approach. ”
Female athletes and sex differences.
Case study: Low Energy Intake Leads to Body Composition and Performance Decrements in a Highly-Trained, Female Athlete: The WANDER (Woman's Activity and Nutrition during an Extensive Hiking Route) Case Study. Saenz et al. (2023) J Am Nutr Assoc. “ In this case study, low energy availability led to decreased performance, body composition, and energy in a well-trained, Master class, female thru-hiker. This study underscores the critical need for adequate energy intake during thru-hiking, ultra-endurance athletic events, especially those with challenging environmental stressors. It also strongly supports the need for multidisciplinary approaches for optimizing performance and reducing injury risks in ultra-endurance female athletes. There are several gaps in the literature remaining, particularly how low energy availability, and possibly Relative Energy Deficiency in Sport (RED-S), expresses itself in Master class athletes. Adequate energy intake is paramount to a successful thru-hike and more research, and robust assessments, on energy needs, sustainable and enjoyable dietary approaches, and optimal thru-hike-specific dietary counseling can provide much-needed insight into ways to reduce injury risks and support performance and recovery in thru-hiking athletes. ” Scoping review: Barriers and enablers influencing female athlete return-to-sport postpartum: a scoping review. Tighe et al. (2023) Br J Sports Med. “ This review synthesised existing literature to identify barriers and enablers that can influence female athletes successful return-to-sport postpartum. This will help guide the development of evidence-based policies that support female athletes during this unique life stage, as few of these policies currently exist. Postpartum recovery time, time to manage motherhood and sport demands, sport organisation policies, stereotypes and social support were identified as the most significant of factors to influence female athletes successful return-to-sport postpartum. Moreover, paid maternity leave offering job security, travel support for carer and child and affordable and accessible childcare are critical policy inclusions to appropriately support female athletes in their return-to-sport postpartum. In addition to policy development, various opportunities exist for clinicians and sport organisations to better support postpartum athletes. To build on the current body of evidence, future research should adopt standardised definitions of the ‘postpartum period' and ‘athlete’ as well as report time taken to return-to-sport and the level of sport athletes returned to postpartum.. ” Narrative review: Women at Altitude: Sex-Related Physiological Responses to Exercise in Hypoxia. Raberin et al. (2023) Sports Med. “ The pulmonary system seems to be one of the functions most impacted by sex differences and exposure in hypoxia, with women becoming more hypoxemic and having a greater work of breathing than men. Cardiac hemodynamics are not impacted by sex in hypoxia, but vascular reactivity is greater in women at rest or combined with exercise; hence, women seem less peripherally limited than men in hypoxia. While sex differences in hematological parameters are well known, they do not impact acute hematological responses to hypoxia (i.e., plasma contraction). Regarding increases in hemoglobin mass, no clear consensus is apparent and the putative sex differences seem due to low iron stores (more common in women). Although these responses are known to be sensitive to sex hormone fluctuations, the effect of menstrual cycle and the influence of menopause on physiological responses to hypoxia remain poorly investigated. All these responses demand further investigation, with appropriate designs to characterize sex-specific differences. While a growing body of evidence has demonstrated the mechanisms that could impact sex-dependent responses to hypoxia, the impact on performance in hypoxia, mountaineering, and susceptibility to severe altitude illness is not yet fully understood. Further work is required to translate these sex differences in responses to hypoxia into practical recommendations, either for reducing the risks at high altitude or for improving performance or health benefits associated with altitude training or hypoxic conditioning
. ” Consensus statement: The Biological Basis of Sex Differences in Athletic Performance: Consensus Statement for the American College of Sports Medicine. Hunter et al. (2023) Med Sci Sports Exerc. “ Males outperform females in sports and athletic endeavors that require aerobic endurance, muscle strength, power, and speed. The biological differences between males and females result in ~10%–30% sex difference in athletic performance, although the magnitude depends on the demands of the event/sport and which biologic systems are most involved. Males are taller with longer limbs, stronger, more powerful, and faster than females over short and long distances. Males have a larger skeletal muscle mass, less percentage body fat, and faster contracting muscle due to a larger proportional area and volume of fast contracting muscle fibers than females. Sex differences in endurance performance such as distance running (~10% among the world’s best) is dictated by the higher aerobic power of males compared with females. This is because males have a larger heart size, and thus greater stroke volume, blood hemoglobin concentration, and mass, larger muscle mass, larger airways and lung volume, less body fat, and consequently a higher VO2max than females. Sex differences in athletic events that are reliant primarily on muscular power, including weightlifting and jumping events, can be as high as 30% because males have more muscle mass and faster contracting muscles, with longer limbs and taller stature that together generate more limb power for males compared with females.
The primary cause for the large sex difference in athletic performance is exposure to high levels of endogenous testosterone in boys at the onset of puberty (~12 yr) that will rise 30-fold in males but remains low in females. Females, on the other hand, experience the menstrual cycle and monthly fluctuations in endogenous hormones including estradiol, which is important in maintenance of bone mass, skeletal muscle, and tendon protein metabolism. However, estradiol does not have the same anabolic effects as testosterone, which dictates the large sex differences in performance. The effects of the sex steroid hormones, in particular the potent, quick-acting, and long-lasting effects of testosterone, are evident in 1) experiments/studies where sex steroid hormones have been added or suppressed in both males and females, 2) studies of the physiology and performance of individuals with various differences of sex development (DSD), and 3) studies of transgender men and transgender women in response to gender-affirming hormone therapy (GAHT).
Although it is clear that biologic males outperform biologic females in muscular power, strength, and endurance, primarily due to the potent effects of testosterone, there remain knowledge gaps in our understanding of the sex and gender differences in athletic performance and the training response of males and females across many different events/sports. Table 5 highlights several areas for opportunity and future directions. Many of the acute exercise and training studies are conducted on men, often with the assumption that the effects are similar in women. The suggested future directions in Table 5 are opportunities for high-impact studies, with the goal of providing a more complete understanding of the sex differences in athletic performance and the adaptations associated with training. ”
Systematic review: Perspectives on Concurrent Strength and Endurance Training in Healthy Adult Females: A Systematic Review. Mikkonen et al. (2023) Sports Med. “ Concurrent strength and endurance training appears to improve strength and endurance capacity in female populations. However, there are several research paradigms that still need to be explored, such as the “interference” effect in athletic female populations, the effects of concurrent strength and endurance training on fast-force production in females, and the effect of menstrual status and hormonal contraceptive use (hormone profiles) on concurrent strength and endurance training adaptations. Additionally, the influence of time of day (chronobiology) on concurrent strength and endurance training outcomes is yet to be investigated in females.
A meta-analysis of concurrent strength and endurance training in females is premature due to the limited volume of concurrent strength and endurance training research in females. Furthermore, a meta-analysis of such a heterogeneous group of studies may not accurately reflect the efficacy of concurrent strength and endurance training. Likewise, it is difficult to draw strong conclusions or generalizations regarding specific combinations of concurrent strength and endurance training in females, due to the heterogeneous fitness levels, training plans, and training durations presented in the included literature. Indeed, several challenges exist in the area of concurrent strength and endurance training research, as a plethora of training combinations exist (and are constantly added). Different approaches to training may reveal subtle, but meaningful, differences in training responses and adaptations. As such, and based on the included literature, evidence-based modifications to specific exercise prescription for females cannot be made, although it may be suggested the “more important” training mode be completed first when combining strength and endurance into the same session and that concurrent strength and endurance training may be most effective (in recreationally active populations) when performed on separate days. Additional exploration of sport-specific concurrent strength and endurance training, including the upper body, would be useful for practitioners making evidence-based decisions regarding testing and training for some athlete populations. Furthermore, future research about concurrent strength and endurance training in females should consider hormone profiles including menstrual status (energy availability) and hormonal contraceptive use and potentially also the reason for hormonal contraceptive use. ”
And, to help you wash down the latest evidence, here's a snifter from my recent indulgence...
What is the beer called? Stormburst IPA.
Which brewery made it? O'Hara's Brewery (Carlow, Ireland).
What type of beer is it? American IPA.
How strong is the beer? 7.2% ABV.
How would I describe this beer?
Cloudy amber to the eye, classic hoppy IPA to the nose, a creamy mouth feel with a jazzy citrus-ness on the tongue, smooth down the hatch, and a pleasant tropical not-too-sweet not-too-bitter aftertaste.
What is my Rating of Perceived beer Enjoyment?
RP(be)E(r) = 7 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.