Metabolic factors limiting performance in marathon runners

Fractional utilization of the 10-minute treadmill test velocity in running performance

This study aimed to evaluate the applicability of the 10-minute submaximal treadmill test (T10 test), a self-paced test, in determining critical speed (CS) and predicting running performance. Specifically, we sought to identify the percentage of T10 velocity (vT10) that runners performed in official distance races, and to compare physiological and performance indicators between sexes. 60 recreational runners (n=34 males and n=26 females) underwent a maximum incremental test, the novel T10 test, and ran 1200-m and 2400-m on the track. Runners self-reported their best performance times. Generalized Linear Model was used to compare running performances between sexes. For both males and females, the %vT10 in 5 km, 10 km, and half-marathon races occurred at 107.5% and 106.5%, 99.9% and 100.8%, and 92.6% and 97.1%, respectively. There was no interaction effect (p=0.520) and no main effect of sex (p=0.443). There was a main effect of distance (p<0.001), indicating that %vT10 in the 5km race differed from that found in the 10 km race (p=0.012), as well as in the half-marathon (p<0.001). Our findings suggest that %vT10 values can be used to determine pace in recreational endurance runners for race distances regardless of sex.

Brain, Metabolic, and RPE Responses during a Free-Pace Marathon: A Preliminary Study

The concept of the "central governor" in exercise physiology suggests the brain plays a key role in regulating exercise performance by continuously monitoring physiological and psychological factors. In this case report, we monitored, for the first time, a marathon runner using a metabolic portable system and an EEG wireless device during an entire marathon to understand the influence of brain activity on performance, particularly the phenomenon known as "hitting the wall". The results showed significant early modification in brain activity between the 10th and 15th kilometers, while the RPE remained low and cardiorespiratory responses were in a steady state. Thereafter, EEG responses decreased after kilometer 15, increased briefly between kilometers 20 and 25, then continued at a slower pace. After kilometer 30, both speed and respiration values dropped, along with the respiratory exchange ratio, indicating a shift from carbohydrate to fat metabolism, reflecting glycogen depletion. The runner concluded the race with a lower speed, higher RPE (above 15/20 on the Borg RPE scale), and reduced brain activity, suggesting mental exhaustion. The findings suggest that training strategies focused on recognizing and responding to brain signals could allow runners to optimize performance and pacing strategies, preventing premature exhaustion and improving overall race outcomes.

Effects of Short-Term Nighttime Carbohydrate Restriction Method on Exercise Performance and Fat Metabolism

BACKGROUND

The sleep-low method has been proposed as a way to sleep in a low-glycogen state, increase the duration of low glycogen availability and sleep and temporarily restrict carbohydrates to improve exercise performance. However, long-term dietary restriction may induce mental stress in athletes. Therefore, if it can be shown that the effects of the sleep-low method can be achieved by restricting the carbohydrate intake at night (the nighttime carbohydrate restriction method), innovative methods could be developed to reduce weight in individuals with obesity and enhance athletes' performance with reduced stress and in a shorter duration when compared with those of previous studies. With this background, we conducted a study with the purpose of examining the intervention effects of a short-term intensive nighttime carbohydrate restriction method.

METHODS

A total of 22 participants were recruited among university students participating in sports club activities. The participants were assigned at random to groups, including a nighttime carbohydrate restriction group of 11 participants (6 males, 5 females; age 22.3 ± 1.23) who started a carbohydrate-restricted diet and a group of 11 participants (5 males, 6 females; age 21.9 ± 7.9) who continued with their usual diet. The present study had a two-group parallel design. In the first week, no dietary restrictions were imposed on either group, and the participants consumed their own habitual diets. In the second week, the total amount of calories and carbohydrate intake measured in the first week were divided by seven days, and the average values were calculated. These were used as the daily calorie and carbohydrate intakes in the second week. Only the nighttime carbohydrate restriction group was prohibited from consuming carbohydrates after 4:00 p.m. During the two-week study period, all participants ran for one hour each day before breakfast at a heart rate of 65% of their maximum heart rate.

RESULTS

The results obtained from young adults participating in sports showed significant differences in peak oxygen consumption (V·O2peak), work rate max, respiratory quotient (RQ), body weight and lean body mass after the intervention when compared with before the intervention in the nighttime carbohydrate restriction group (p < 0.05).

CONCLUSIONS

Our findings suggest that the nighttime carbohydrate restriction method markedly improves fat metabolism even when performed for a short period. This method can be used to reduce body weight in individuals with obesity and enhance athletes' performance. However, it is important to consider the intake of nutrition other than carbohydrates.

Functional nutrition for the health of exercising individuals and elite sportspersons

INTRODUCTION

Elite sportspersons who are involved in high-intensity physical sports indulge in severe training and competition schedules, which exposes them to high levels of inflammatory and oxidative stress, hence it may hamper their health sometimes. Disturbance in the health of sportspersons also induces compromised performances.

THE PREMISE FOR FUNCTIONAL NUTRITION

Functional nutrition is essential for elite sportspersons training for securing both rest and recovery to have proper health and anticipated performance. Apart from serving the energy needs of the sportspersons, the nutrition strategies should provide them with certain metabolic advantages, which provide greater health and immunity, to ensure proper training and competition. The diet of the sportspersons needs to contain appropriate anti-inflammatory and antioxidative nutrients, to ensure to reduction and control of the physiological stress of tissues during high-intensity physical sports, especially during marathon running. Preserving anabolic valence among sportspersons for muscle myokine optimization is an essential aspect of sports nutrition, which secures health and provides excellent performance potential. Preservation and optimization of gut microbiome among sportspersons enhance immune health and performance, through proper gut integrity and enhanced metabolic cascades. As the genes are to be properly expressed for excellent manifestation in protein synthesis and other metabolic signaling, achieving genetic valance through proper nutrition ensures the health of the sportspersons.

CONCLUSION

Functional nutrition seems a very necessary and potent factor in the training and competition aspects of elite sportspersons since nutrition not only provides recovery but also ensures proper health for elite sportspersons.

Assessing exogenous carbohydrate intake needed to optimize human endurance performance across sex: insights from modeling runners pursuing a sub-2-h marathon

Carbohydrate (CHO) availability sustains high metabolic demands during prolonged exercise. The adequacy of current CHO intake recommendations, 30-90 g·h-1 dependent on CHO mixture and tolerability, to support elite marathon performance is unclear. We sought to scrutinize the current upper limit recommendation for exogenous CHO intake to support modeled sub-2-h marathon (S2M) attempts across elite male and female runners. Male and female runners (n = 120 each) were modeled from published literature with reference characteristics necessary to complete a S2M (e.g., body mass and running economy). Completion of a S2M was considered across a range of respiratory exchange rates, with maximal starting skeletal muscle and liver glycogen content predicted for elite male and female runners. Modeled exogenous CHO bioavailability needed for male and female runners were 93 ± 26 and 108 ± 22 g·h-1, respectively (P < 0.0001, d = 0.61). Without exogenous CHO, males were modeled to deplete glycogen in 84 ± 7 min, females in 71 ± 5 min (P < 0.0001, d = 2.21) despite higher estimated CHO oxidation rates in males (5.1 ± 0.5 g·h-1) than females (4.4 ± 0.5 g·h-1; P < 0.0001, d = 1.47). Exogenous CHO intakes ≤ 90 g·h-1 are insufficient for 65% of modeled runners attempting a S2M. Current recommendations to support marathon performance appear inadequate for elite marathon runners but may be more suitable for male runners in pursuit of a S2M (56 of 120) than female runners (28 of 120).NEW & NOTEWORTHY This study scrutinizes the upper limit of exogenous carbohydrate (CHO) recommendations for elite male and female marathoners by modeling sex-specific needs across an extreme metabolic challenge lasting ∼2 h, a sub-2-h marathon. Contemporary nutritional guidelines to optimize marathon performance appear inadequate for most elite marathon runners but appear more appropriate for males over their female counterparts. Future research examining possible benefits of exogenous CHO intakes > 90 g·h-1 should prioritize female athlete study inclusion.

The pacing differences in performance levels of marathon and half-marathon runners

Introduction

Many studies indicate a considerable impact of optimal pacing on long-distance running performance. Given that the amount of carbohydrates in metabolic processes increases supralinearly with the running intensity, we may observe differences between the pacing strategies of two long-distance races and different performance levels of runners. Accordingly, the present study aimed to examine the differences in pacing strategies between marathon and half-marathon races regarding the performance levels of runners.

Methods

The official results and split times from a total of 208,760 (marathon, N = 75,492; half-marathon, N = 133,268) finishers in the "Vienna City Marathon" between 2006 and 2018 were analyzed. The percentage of the average change of speed for each of the five segments (CS 1-5), as well as the absolute change of speed (ACS) were calculated. The CS 1-5 for the marathon are as follows: up to the 10th km, 10th - 20th km, 20th - 30th km, 30th - 40th km, and from the 40th km to the 42.195 km. For the half-marathon, the CS 1-5 are half of the marathon values. Four performance groups were created as quartiles of placement separately for sexes and races: high-level (HL), moderate to high-level (MHL), moderate to low-level (MLL), and low-level (LL).

Results

Positive pacing strategies (i.e., decrease of speed) were observed in all performance groups of both sex and race. Across CS 1-5, significant main effects (p < 0.001) were observed for the segment, performance level, and their interaction in both sex and race groups. All LL groups demonstrated higher ACS (men 7.9 and 6.05%, as well as women 5.83 and 5.49%, in marathon and half-marathon, respectively), while the HL performance group showed significantly lower ACS (men 4.14 and 2.97%, as well as women 3.16 and 2.77%, in marathon and half-marathon, respectively). Significant main effects (p < 0.001) for the race were observed but with a low effect size in women (ŋ2 = 0.001).

Discussion

Better runners showed more even pacing than slower runners. The half-marathoners showed more even pacing than the marathoners across all performance groups but with a trivial practical significance in women.

Recovery of the autonomic nervous system following football training among division I collegiate football athletes: The influence of intensity and time

The autonomic nervous system (ANS) is profoundly affected by high intensity exercise. However, evidence is less clear on ANS recovery and function following prolonged bouts of high intensity exercise, especially in non-endurance athletes. Therefore, this study aimed to investigate the relationships between duration and intensity of acute exercise training sessions and ANS recovery and function in Division I football athletes. Fifty, male football athletes were included in this study. Subjects participated in 135 days of exercise training sessions throughout the 25-week season and wore armband monitors (Warfighter Monitor, Tiger Tech Solutions) equipped with electrocardiography capabilities. Intensity was measured via heart rate (HR) during an 'active state', defined as HR ≥ 85 bpm. Further, data-driven intensity thresholds were used and included HR < 140 bpm, HR < 150 bpm, HR < 160 bpm, HR ≥ 140 bpm, HR ≥ 150 bpm and HR ≥ 160 bpm. Baseline HR and HR recovery were measured and represented ANS recovery and function 24h post-exercise. Linear regression models assessed the relationships between time spent at the identified intensity thresholds and ANS recovery and function 24h post-exercise. Statistical significance set at α < 0.05. Athletes participated in 128 training sessions, totaling 2735 data points analyzed. Subjects were predominantly non-Hispanic black (66.0%), aged 21.2 (±1.5) years and average body mass index of 29.2 (4.7) kg⋅(m2)-1. For baseline HR, statistically significant associations between duration and next-day ANS recovery were observed at HR < 140 bpm (β = -0.08 ± 0.02, R2 = 0.31, p < 0.001), HR above 150 and 160 bpm intensity thresholds (β = 0.25 ± 0.02, R2 = 0.69, p < 0.0000 and β = 0.59 ± 0.06, R2 = 0.71, p < 0.0000). Similar associations were observed for HR recovery: HR < 140 bpm (β = 0.15 ± 0.03, R2 = 0.43, p < 0.0000) and HR above 150 and 160 bpm (β = -0.33 ± 0.03, R2 = 0.73, p < 0.0000 and β = -0.80 ± 0.06, R2 = 0.71, p < 0.0000). The strengths of these associations increased with increasing intensity, HR ≥ 150 and 160 bpm (baseline HR: β range = 0.25 vs 0.59, R2: 0.69 vs 0.71 and HR recovery: β range = -0.33 vs -0.80, R2 = 0.73 vs 0.77). Time spent in lower intensity thresholds, elicited weaker associations with ANS recovery and function 24h post-exercise, with statistical significance observed only at HR < 140 bpm (β = -0.08 ± 0.02, R2 = 0.31, p < 0.001). The findings of this study showed that ANS recovery and function following prolonged high intensity exercise remains impaired for more than 24h. Strength and conditioning coaches should consider shorter bouts of strenuous exercise and extending recovery periods within and between exercise training sessions.

Effect of a low carbohydrate, high fat diet versus a high carbohydrate diet on exercise efficiency and economy in recreational male athletes

BACKGROUND

Exercise efficiency and economy are key determinants of endurance exercise performance. In this cross-over intervention trial, we investigated the effect of adherence to a low carbohydrate, high fat (LCHF) diet versus a high carbohydrate (HC) diet on gross efficiency (GE) and (OC) during exercise, both after 2 days and after 14 days of adherence.

METHODS

Fourteen recreational male athletes followed a two-week LCHF diet (<10 energy % carbohydrate) and a two-week HC diet (>50 energy % carbohydrate), in random order, with a wash-out period of three weeks in between. After 2 and 14 days on each diet, the athletes performed a 90-minutes submaximal exercise session on a bicycle ergometer. Indirect calorimetry measurements were done after 60 minutes of exercise to calculate GE and OC.

RESULTS

GE was significantly lower on the LCHF diet compared to the HC diet, after 2 days (17.6±1.9 vs. 18.8±1.2%, P=0.011, for the LCHF and HC diet respectively), not after 14 days. OC was significantly higher on the LCHF diet compared to the HC diet, after 2 days (1191±138 vs. 1087±72 mL O<inf>2</inf>/kCal, P=0.003, for the LCHF and HC diet respectively), and showed a strong tendency to remain higher after 14 days, P=0.018.

CONCLUSIONS

Although LCHF diets are popular strategies to increase fat oxidation during exercise, adherence to a LCHF diet was associated with a lower exercise efficiency and economy compared to a HC diet.

Exercise in adults with type 1 diabetes mellitus

Regular physical activity improves cardiometabolic and musculoskeletal health, helps with weight management, improves cognitive and psychosocial functioning, and is associated with reduced mortality related to cancer and diabetes mellitus. However, turnover rates of glucose in the blood increase dramatically during exercise, which often results in either hypoglycaemia or hyperglycaemia as well as increased glycaemic variability in individuals with type 1 diabetes mellitus (T1DM). A complex neuroendocrine response to an acute exercise session helps to maintain circulating levels of glucose in a fairly tight range in healthy individuals, while several abnormal physiological processes and limitations of insulin therapy limit the capacity of people with T1DM to exercise in a normoglycaemic state. Knowledge of the acute and chronic effects of exercise and regular physical activity is critical for the formulation of clinical strategies for the management of insulin and nutrition for active patients with T1DM. Emerging diabetes-related technologies, such as continuous glucose monitors, automated insulin delivery systems and the administration of solubilized glucagon, are demonstrating efficacy for preserving glucose homeostasis during and after exercise in this population of patients. This Review highlights the beneficial effects of regular exercise and details the complex endocrine and metabolic responses to different types of exercise for adults with T1DM. An overview of basic clinical strategies for the preservation of glucose homeostasis using emerging technologies is also provided.

Heart Rate Does Not Reflect the %VO2max in Recreational Runners during the Marathon

Exercise physiologists and coaches prescribe heart rate zones (between 65 and 80% of maximal heart rate, HR_max) during a marathon because it supposedly represents specific metabolic zones and the percentage of V˙O_2max below the lactate threshold. The present study tested the hypothesis that the heart rate does not reflect the oxygen uptake of recreational runners during a marathon and that this dissociation would be more pronounced in the lower performers' group (>4 h). While wearing a portable gas exchange system, ten male endurance runners performed an incremental test on the road to determine V˙O_2max, HR_max, and anaerobic threshold. Two weeks later, the same subjects ran a marathon with the same device for measuring the gas exchanges and HR continuously. The %HR_max remained stable after the 5th km (between 88% and 91%, p = 0.27), which was not significantly different from the %HR_max at the ventilatory threshold (89 ± 4% vs. 93 ± 6%, p = 0.12). However, the %V˙O_2max and percentage of the speed associated with V˙O_2max decreased during the marathon (81 ± 5 to 74 ± 5 %V˙O_2max and 72 ± 9 to 58 ± 14 %vV˙O_2max, p < 0.0001). Hence, the ratio between %HR_max and %V˙O_2max increased significantly between the 5th and the 42nd km (from 1.01 to 1.19, p = < 0.001). In conclusion, pacing during a marathon according to heart rate zones is not recommended. Rather, learning about the relationship between running sensations during training and racing using RPE is optimal.

Consistency of pacing profile according to performance level in three different editions of the Chicago, London, and Tokyo marathons

Running pacing has become a focus of interest over recent years due to its relationship with performance, however, it is still unknown the consistency of each race in different editions. The aim of this study is to analyze the consistency of pacing profile in three consecutive editions of three marathon races. A database of 282,808 runners, compiled from three different races (Chicago, London, and Tokyo Marathon) and three editions (2017, 2018, and 2019) was analyzed. Participants were categorized according to their time performance in the marathon, every 30 min from 2:30 h to sub-6 h. The relative speed of each section for each runner was calculated as a percentage of the average speed for the entire race. The intraclass correlation coefficients (ICC) of relative speed at the different pacing section, taking into account the runner time categories, was excellent over the three marathon editions (ICC > 0.93). The artificial intelligence model showed an accuracy of 86.8% to classify the runners' data in three marathons, suggesting a consistency between editions with identifiable differences between races. In conclusion, although some differences have been observed between editions in certain sections and marathon runner categories, excellent consistency of the pacing profile was observed. The study of pacing profile in a specific marathon can, therefore, be helpful for runners, coaches and marathon organizers for planning the race and improving its organization.

High Energetic Demand of Elite Rowing - Implications for Training and Nutrition

Purpose: Elite rowers have large body dimensions, a high metabolic capacity, and they realize high training loads. These factors suggest a high total energy requirement (TER), due to high exercise energy expenditure (EEE) and additional energetic needs. We aimed to study EEE and intensity related substrate utilization (SU) of elite rowers during rowing (EEE_ROW) and other (EEE_NON-ROW) training.

Methods: We obtained indirect calorimetry data during incremental (N = 174) and ramp test (N = 42) ergometer rowing in 14 elite open-class male rowers (body mass 91.8 kg, 95% CI [87.7, 95.9]). Then we calculated EEE_ROW and SU within a three-intensity-zone model. To estimate EEE_NON-ROW, appropriate estimates of metabolic equivalents of task were applied. Based on these data, EEE, SU, and TER were approximated for prototypical high-volume, high-intensity, and tapering training weeks. Data are arithmetic mean and 95% confidence interval (95% CI).

Results: EEE_ROW for zone 1 to 3 ranged from 15.6 kcal·min⁻¹, 95% CI [14.8, 16.3] to 49.8 kcal·min⁻¹, 95% CI [48.1, 51.6], with carbohydrate utilization contributing from 46.4%, 95% CI [42.0, 50.8] to 100.0%, 95% CI [100.0, 100.0]. During a high-volume, a high-intensity, or a taper week, TER was estimated to 6,775 kcal·day⁻¹, 95% CI [6,651, 6,898], 5,772 kcal·day⁻¹, 95% CI [5,644, 5,900], or 4,626 kcal∙day⁻¹, 95% CI [4,481, 4,771], respectively.

Conclusion: EEE in elite open-class male rowers is remarkably high already during zone 1 training and carbohydrates are dominantly utilized, indicating relatively high metabolic stress even during low intensity rowing training. In high-volume training weeks, TER is presumably at the upper end of the sustainable total energy expenditure. Periodized nutrition seems warranted for rowers to avoid low energy availability, which might negatively impact performance, training, and health.

One hundred marathons in 100 days: Unique biomechanical signature and the evolution of force characteristics and bone density

BACKGROUND

An extraordinary long-term running performance may benefit from low dynamic loads and a high load-bearing tolerance. An extraordinary runner (age = 55 years, height = 1.81 m, mass = 92 kg) scheduled a marathon a day for 100 consecutive days. His running biomechanics and bone density were investigated to better understand successful long-term running in the master athlete.

METHODS

Overground running gait analysis and bone densitometry were conducted before the marathon-a-day challenge and near its completion. The case's running biomechanics were compared pre-challenge to 31 runners who were matched by a similar foot strike pattern.

RESULTS

The case's peak vertical loading rate (Δx̄ = -61.9 body weight (BW)/s or -57%), peak vertical ground reaction force (Δx̄ = -0.38 BW or -15%), and peak braking force (Δx̄ = -0.118 BW or -31%) were remarkably lower (p < 0.05) than the control group at ∼3.3 m/s. The relatively low loading-related magnitudes were attributed to a remarkably high duty factor (0.41) at the evaluated speed. The foot strike angle of the marathoner (29.5°) was greater than that of the control group, affecting the peak vertical loading rate. Muscle powers in the lower extremity were also remarkably low in the case vs. controls: peak power of knee absorption (Δx̄ = -9.16 watt/kg or -48%) and ankle generation (Δx̄ = -3.17 watt/kg or -30%). The bone mineral density increased to 1.245 g/cm² (+2.98%) near completion of the challenge, whereas the force characteristics showed no statistically significant change.

CONCLUSION

The remarkable pattern of the high-mileage runner may be useful in developing or evaluating load-shifting strategies in distance running.

Triceps Surae Muscle-Tendon Properties as Determinants of the Metabolic Cost in Trained Long-Distance Runners

Purpose: This study aimed to determine whether triceps surae's muscle architecture and Achilles tendon parameters are related to running metabolic cost (C) in trained long-distance runners. Methods: Seventeen trained male recreational long-distance runners (mean age = 34 years) participated in this study. C was measured during submaximal steady-state running (5 min) at 12 and 16 km h-1 on a treadmill. Ultrasound was used to determine the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and soleus (SO) muscle architecture, including fascicle length (FL) and pennation angle (PA), and the Achilles tendon cross-sectional area (CSA), resting length and elongation as a function of plantar flexion torque during maximal voluntary plantar flexion. Achilles tendon mechanical (force, elongation, and stiffness) and material (stress, strain, and Young's modulus) properties were determined. Stepwise multiple linear regressions were used to determine the relationship between independent variables (tendon resting length, CSA, force, elongation, stiffness, stress, strain, Young's modulus, and FL and PA of triceps surae muscles) and C (J kg-1m-1) at 12 and 16 km h-1. Results: SO PA and Achilles tendon CSA were negatively associated with C (r 2 = 0.69; p < 0.001) at 12 km h-1, whereas SO PA was negatively and Achilles tendon stress was positively associated with C (r 2 = 0.63; p = 0.001) at 16 km h-1, respectively. Our results presented a small power, and the multiple linear regression's cause-effect relation was limited due to the low sample size. Conclusion: For a given muscle length, greater SO PA, probably related to short muscle fibers and to a large physiological cross-sectional area, may be beneficial to C. Larger Achilles tendon CSA may determine a better force distribution per tendon area, thereby reducing tendon stress and C at submaximal speeds (12 and 16 km h-1). Furthermore, Achilles tendon morphological and mechanical properties (CSA, stress, and Young's modulus) and triceps surae muscle architecture (GM PA, GM FL, SO PA, and SO FL) presented large correlations with C.

Exercise blood-drop metabolic profiling links metabolism with perceived exertion

Background: Assessing detailed metabolism in exercising persons minute-to-minute has not been possible. We developed a "drop-of-blood" platform to fulfill that need. Our study aimed not only to demonstrate the utility of our methodology, but also to give insights into unknown mechanisms and new directions. Methods: We developed a platform, based on gas chromatography and mass spectrometry, to assess metabolism from a blood-drop. We first observed a single volunteer who ran 13 km in 60 min. We particularly monitored relative perceived exertion (RPE). We observed that 2,3-bisphosphoglycerate peaked at RPE in this subject. We next expanded these findings to women and men volunteers who performed an RPE-based exercise protocol to RPE at Fi O ₂ 20.9% or Fi O ₂ 14.5% in random order. Results: At 6 km, our subject reached his maximum relative perceived exertion (RPE); however, he continued running, felt better, and finished his run. Lactate levels had stably increased by 2 km, ketoacids increased gradually until the run's end, while the hypoxia marker, 2,3 bisphosphoglycerate, peaked at maximum relative perceived exertion. In our normal volunteers, the changes in lactate, pyruvate, ß hydroxybutyrate and a hydroxybutyrate were not identical, but similar to our model proband runner. Conclusion: Glucose availability was not the limiting factor, as glucose availability increased towards exercise end in highly exerted subjects. Instead, the tricarboxylic acid→oxphos pathway, lactate clearance, and thus and the oxidative capacity appeared to be the defining elements in confronting maximal exertion. These ideas must be tested further in more definitive studies. Our preliminary work suggests that our single-drop methodology could be of great utility in studying exercise physiology.

Supplement intake in half-marathon, (ultra-)marathon and 10-km runners - results from the NURMI study (Step 2)

The primary nutritional challenge facing endurance runners is meeting the nutrient requirements necessary to optimize the performance and recovery of prolonged training sessions. Supplement intake is a commonly used strategy by elite and recreational distance runners to meet nutritional recommendations. This study was conducted to investigate the patterns of supplement intake among different groups of distance runners and the potential association between supplement intake and sex, age, running and racing experiences.In a cross-sectional design, from a total of 317 runners participating in this survey, 119 distance runners were involved in the final sample after data clearance, assigned into three groups of 10-km runners (n = 24), half-marathoners (n = 44), and (ultra-)marathoners (n = 51). Personal characteristics, training and racing experiences, as well as patterns of supplement intake, including type, frequency, and dosage, were evaluated by questionnaire. Food Frequency Questionnaire was implemented to assess macronutrient intake. ANOVA and logistic regression were used for statistical analysis.While 50 % of total distance runners reported consuming supplements regularly, no differences between distance groups in consumption of carbohydrate/protein, mineral, or vitamin supplements were observed (p > 0.05). In addition, age, sex, running and racing experience showed no significant association with supplement intake (p > 0.05). Vitamin supplements had the highest intake rate in runners by 43 % compared to minerals (34 %) and carbohydrate/protein supplements (19 %).The present findings provide a window into the targeted approaches of long-distance runners as well as their coaches and sport nutrition specialists when applying and suggesting sustainable nutritional strategies for training and competition.Trial registration: ISRCTN73074080. Retrospectively registered 12th June 2015.

Characterizing Marathon-Induced Metabolic Changes Using 1H-NMR Metabolomics

Although physical activity is a health-promoting, popular global pastime, regular engagement in strenuous exercises, such as long-distance endurance running races, has been associated with a variety of detrimental physiological and immunological health effects. The resulting altered physiological state has previously been associated with fluctuations in various key metabolite concentrations; however, limited literature exists pertaining to the global/holistic metabolic changes that are induced by such. This investigation subsequently aims at elucidating the metabolic changes induced by a marathon by employing an untargeted proton nuclear magnetic resonance (¹H-NMR) spectrometry metabolomics approach. A principal component analysis (PCA) plot revealed a natural differentiation between pre- and post-marathon metabolic profiles of the 30-athlete cohort, where 17 metabolite fluctuations were deemed to be statistically significant. These included reduced concentrations of various amino acids (AA) along with elevated concentrations of ketone bodies, glycolysis, tricarboxylic acid (TCA) cycle, and AA catabolism intermediates. Moreover, elevated concentrations of creatinine and creatine in the post-marathon group supports previous findings of marathon-induced muscle damage. Collectively, the results of this investigation characterize the strenuous metabolic load induced by a marathon and the consequential regulation of main energy-producing pathways to accommodate this, and a better description of the cause of the physiological changes seen after the completion of a marathon.

Age and Sport Intensity-Dependent Changes in Cytokines and Telomere Length in Elite Athletes

Exercise-associated immune response plays a crucial role in the aging process. The aim of this study is to investigate the effect of sport intensity on cytokine levels, oxidative stress markers and telomere length in aging elite athletes. In this study, 80 blood samples from consenting elite athletes were collected for anti-doping analysis at an anti-doping laboratory in Italy (FMSI). Participants were divided into three groups according to their sport intensity: low-intensity skills and power sports (LI, n = 18); moderate-intensity mixed soccer players (MI, n = 31); and high-intensity endurance sports (HI, n = 31). Participants were also divided into two age groups: less than 25 (n = 45) and above 25 years old (n = 35). Serum levels of 10 pro and anti-inflammatory cytokines and two antioxidant enzymes were compared in age and sport intensity groups and telomere lengths were measured in their respective blood samples. Tumor necrosis factor-alpha (TNF-α) was the only cytokine showing significantly higher concentration in older athletes, regardless of sport intensity. Interleukin (IL)-10 increased significantly in HI regardless of age group, whereas IL-6 concentration was higher in the older HI athletes. IL-8 showed a significant interaction with sport intensity in different age groups. Overall, significant positive correlations among levels of IL-6, IL-10, IL-8 and TNF-α were identified. The antioxidant catalase activity was positively correlated with levels of TNF-α. Telomere length increased significantly with sport intensity, especially in the younger group. HI had longer telomeres and higher levels of pro- and anti-inflammatory cytokines, suggesting less aging in HI compared to low and moderate counterparts in association with heightened immune response. Investigation of the functional significance of these associations on the health and performance of elite athletes is warranted.

Effect of Carbohydrate Content in a Pre-event Meal on Endurance Performance-Determining Factors: A Randomized Controlled Crossover-Trial

The current study aimed to investigate the effect of the relative CHO content in a pre-event meal on time to exhaustion (TTE), peak oxygen uptake (V∙O2peak), the 2nd lactate threshold (LT2), onset of blood lactate accumulation (OBLA), and work economy (WE) and to compare responses between well-trained and recreationally trained individuals. Eleven well-trained and 10 recreationally trained men performed three trials in a randomized cross-over design, in which they performed exercise tests (1) after a high-CHO pre-event meal (3 g · kg⁻¹), (2) a low-CHO pre-event meal (0.5 g · kg⁻¹), or (3) in a fasted-state. The test protocol consisted of five submaximal 5-min constant-velocity bouts of increasing intensity and a graded exercise test (GXT) to measure TTE. A repeated measure ANOVA with a between-subjects factor (well-trained vs. recreational) was performed. A main effect of pre-event meal was found (p = 0.001), with TTE being 8.0% longer following the high-CHO meal compared to the fasted state (p = 0.009) and 7.2% longer compared to the low-CHO meal (p = 0.010). No significant effect of pre-event meal on V∙O2peak, LT2, OBLA, or WE (p ≥ 0.087) was found and no significant interaction effect between training status and pre-event CHO intake was found for TTE or any of the performance-determining variables (p ≥ 0.257). In conclusion, high-CHO content in the pre-event meal led to a longer TTE compared to a meal with a low-CHO content or exercising in a fasted state, both in well-trained and recreationally trained participants. However, the underlying physiological reason for the increased TTE is unclear, as no effect of pre-event meal on the main physiological performance-determining variables was found. Thus, pre-event CHO intake should be standardized when the goal is to assess endurance performance but seems to be of less importance when assessing the main performance-determining variables.

How recreational marathon runners hit the wall: A large-scale data analysis of late-race pacing collapse in the marathon

INTRODUCTION

In the marathon, how runners pace and fuel their race can have a major impact on race outcome. The phenomenon known as hitting the wall (HTW) refers to the iconic hazard of the marathon distance, in which runners experience a significant slowing of pace late in the race, typically after the 20-mile mark, and usually because of a depletion of the body's energy stores.

AIM

This work investigates the occurrence of significant late-race slowing among recreational marathoners, as a proxy for runners hitting the wall, to better understand the likelihood and nature of such slowdowns, and their effect on race performance.

METHODS

Using pacing data from more than 4 million race records, we develop a pacing-based definition of hitting the wall, by identifying runners who experience a sustained period of slowing during the latter stages of the marathon. We calculate the cost of these slowdowns relative to estimates of the recent personal-best times of runners and compare slowdowns according to runner sex, age, and ability.

RESULTS

We find male runners more likely to slow significantly (hit the wall) than female runners; 28% of male runners hit the wall compared with 17% of female runners, χ2(1, N = 1, 928, 813) = 27, 693.35, p < 0.01, OR = 1.43. Such slowdowns are more frequent in the 3 years immediately before and after a recent personal-best (PB) time; for example, 36% of all runners hit the wall in the 3 years before a recent PB compared with just 23% in earlier years, χ2(1, N = 509, 444) = 8, 120.74, p < 0.01, OR = 1.31. When runners hit the wall, males slow more than females: a relative slowdown of 0.40 vs. 0.37 is noted, for male and female runners, when comparing their pace when they hit the wall to their earlier race (5km-20km) pace, with t(475, 199) = 60.19, p < 0.01, d = 0.15. And male runners slow over longer distances than female runners: 10.7km vs. 9.6km, respectively, t(475, 199) = 68.44, p < 0.01, d = 0.17. Although, notably the effect size of these differences is small. We also find the finish-time costs of hitting the wall (lost minutes) to increase with ability; r2(7) = 0.91, p < 0.01 r2(7) = 0.81, p < 0.01 for male and female runners, respectively.

CONCLUSIONS

While the findings from this study are consistent with qualitative results from earlier single-race or smaller-scale studies, the new insights into the risk and nature of slowdowns, based on the runner sex, age, and ability, have the potential to help runners and coaches to better understand and calibrate the risk/reward trade-offs that exist as they plan for future races.

Understanding the Holobiont: Crosstalk Between Gut Microbiota and Mitochondria During Long Exercise in Horse

Endurance exercise has a dramatic impact on the functionality of mitochondria and on the composition of the intestinal microbiome, but the mechanisms regulating the crosstalk between these two components are still largely unknown. Here, we sampled 20 elite horses before and after an endurance race and used blood transcriptome, blood metabolome and fecal microbiome to describe the gut-mitochondria crosstalk. A subset of mitochondria-related differentially expressed genes involved in pathways such as energy metabolism, oxidative stress and inflammation was discovered and then shown to be associated with butyrate-producing bacteria of the Lachnospiraceae family, especially Eubacterium. The mechanisms involved were not fully understood, but through the action of their metabolites likely acted on PPARγ, the FRX-CREB axis and their downstream targets to delay the onset of hypoglycemia, inflammation and extend running time. Our results also suggested that circulating free fatty acids may act not merely as fuel but drive mitochondrial inflammatory responses triggered by the translocation of gut bacterial polysaccharides following endurance. Targeting the gut-mitochondria axis therefore appears to be a potential strategy to enhance athletic performance.

The importance of protein intake in master marathon runners

OBJECTIVES

The aim of this study was to investigate the relationships between protein intake (during the tapering period and the race), marathon performance, body composition, acute race-induced changes, and selected metabolic- and muscle damage-related blood biomarkers in recreational master runners.

METHODS

In 58 experienced master runners (58.28 y ± 1.07 y, 174.06 cm ± 0.72 cm, 78.51 kg ± 0.76 kg body mass, 21.38% ± 0.52% body fat, mean ± SEM), nutritional intake was evaluated 1 wk before the race and during the marathon. Body composition was evaluated before and 2 h after the race. Blood samples were collected at the same time points.

RESULTS

Body fat and lean body mass (LBM) were significantly reduced after the marathon (P < 0.01; η²: 0.311-0.888). Significant negative correlations were observed between energy intake from carbohydrates and proteins (expressed per LBM), marathon performance, and race-induced changes of blood metabolic-muscle damage indices (P < 0.05; r: -0.522 to -0.789). Positive correlations were observed between energy from carbohydrates and proteins per LBM, and body mass and LBM changes (P < 0.05; r: 0.485-0.814). The specific contribution of protein intakes per LBM (beta coefficient: -0.789 to 0.615) on race-induced changes of body composition and blood markers was the same as that of carbohydrate intakes per LBM (beta coefficient: -0.777 to 0.559).

CONCLUSIONS

Marathon-induced changes in body composition and metabolic blood indices are highly related to protein intake, either during the tapering period or during the race, with runners experiencing the lowest changes when consuming higher protein intakes.

Analysis of the Impact of a Multi-Strain Probiotic on Body Composition and Cardiorespiratory Fitness in Long-Distance Runners

Use of probiotic supplements, the benefits of which have not been proven in sportspeople, is becoming more widespread among runners. The aim of this study was to evaluate the effect of a multi-strain probiotic on body composition, cardiorespiratory fitness and inflammation in the body. The randomised, double-blind study included 66 long-distance runners. The intervention factor was a multi-strain probiotic or placebo. At the initial and final stages of the study, evaluation of body composition and cardiorespiratory fitness was performed and the presence of inflammation determined. In the group of men using the probiotic, an increase in lean body mass (p = 0.019) and skeletal muscle mass (p = 0.022) was demonstrated, while in the group of women taking the probiotic, a decrease in the content of total body fat (p = 0.600) and visceral fat (p = 0.247) was observed. Maximum oxygen consumption (VO_2max) increased in women (p = 0.140) and men (p = 0.017) using the probiotic. Concentration of tumour necrosis factor-alpha decreased in women (p = 0.003) and men (p = 0.001) using the probiotic and in women (p = 0.074) and men (p = 0.016) using the placebo. Probiotic therapy had a positive effect on selected parameters of body composition and cardiorespiratory fitness of study participants and showed a tendency to reduce inflammation.

Effect of marathon characteristics and runners' time category on pacing profile

This study aimed to analyse differences in pacing profiles in four marathon competitions and to explore that pacing per time category. A database of 91,493 runners gathered from 4 different races was analysed (Valencia, Chicago, London and Tokyo Marathon). Participants were categorized in accordance with their completion time. The relative speed of each section for each runner was calculated as a percentage of the average speed for the entire race. In the four marathons studied, the first 5 km differed widely, presenting London the highest relative speeds (5 km: CI95% London vs. Valencia [12.1, 13.6%], p < 0.001 and ES = 2.1; London vs. Chicago [5.5, 7.1%], p < 0.001 and ES = 1.1; London vs. Tokyo [15.2, 16.8%], p < 0.001 and ES = 2.3). Races did not differ at each section for high-performance runners (sub-2:30), but differences between races increased as the time category increases (e.g. 35 km and sub-3:00: CI95% London vs. Tokyo [-3.1, -1.8%], p < 0.001 and ES = 0.7; 35 km and sub-5:00: London vs. Tokyo [-9.8, -9.2%], p < 0.001 and ES = 1.3). The difference in relative speed between the first and second half of the marathon was higher in London than in the other marathons (e.g. CI95% London vs. Valencia [10.3, 10.8%], p < 0.001 and ES = 1.3). In conclusion, although race characteristics affect pacing, this effect was higher as the category time increases. Race pacing characteristics should be taken into consideration for runners and coaches choosing the race and working on pacing strategies, for researches to extrapolate or interpret results, or for race organizations to improve its pacing characteristics.Highlights The first 5 km differed widely on pacing profiles between the four marathons assessed.London had the highest relative speeds in the first 5 km.Race characteristics affect pacing, but this effect was higher as the category time increases.The difference in relative speed between the first and second half of the marathon was higher in London than in the other marathons.

Tactical behavior of high-level male marathon runners

This study analyzes the strategy used by the best male runners who participated in one of the major city marathons (Frankfurt Marathon, 2008-2018), the all-time performances <2:04:00, the male world records achieved during the 21st century and the Nike Breaking2 Project and INEOS 1:59 Challenge (total = 235 races). The races of the best runners in the Frankfurt Marathon (top 10) were analyzed (n = 110 runners, range: 2:03:42-2:14:05 hours); the runners were divided into two groups according to the tactical used. The pace of Group A (stable pace) remained steady throughout the race, while in Group B (decrease in running speed toward the end of the race) a moderate, but significant drop in speed was detected (P ≤ .001), starting from halfway through the race and getting sharper from the 30th kilometer (30-35 km = 1.6%, P ≤ .001 - 35-40 km = 4.3%, P ≤ .001 - 40-42.195 km: 3.9%, P ≤ .001, total = ≈10%). In the races in which the world record is achieved, the running speed tends to be steady and relatively conservative during the first stretch of the race, increasing smoothly in the second half and achieving a significant increase in the last 2195 m of the race (P = .016, ES = 1.14). Among all the possible strategies, running at a steady pace throughout the race seems the most effective option, especially when priority is given to time rather than position (ie, world records and best all-time races).

Synergistic effect of vascular endothelial growth factor gene inactivation in endothelial cells and skeletal myofibres on muscle enzyme activity, capillary supply and endurance exercise in mice

NEW FINDINGS

What is the central question of this study? Does vascular endothelial growth factor (VEGF) expressed by both endothelial cells and skeletal myofibres maintain the number of skeletal muscle capillaries and regulate endurance exercise? What is the main finding and its importance? VEGF expressed by both endothelial cells and skeletal myofibres is not essential for maintaining capillary number but does contribute to exercise performance.

ABSTRACT

Many chronic diseases lead to exercise intolerance, with loss of skeletal muscle capillaries. While many muscle cell types (myofibres, satellite cells, endothelial cells, macrophages and fibroblasts) express vascular endothelial growth factor (VEGF), most muscle VEGF is stored in myofibre vesicles which can release VEGF to signal VEGF receptor-expressing cells. VEGF gene ablation in myofibres or endothelial cells alone does not cause capillary regression. We hypothesized that simultaneously deleting the endothelial cell (EC) and skeletal myofibre (Skm) VEGF gene would cause capillary regression and impair exercise performance. This was tested in adult mice by simultaneous conditional deletion of the VEGF gene (Skm/EC-VEGF^-/- mice) through the use of VEGFLoxP, HSA-Cre-ER^T2 and PDGFb-iCre-ER^T2 transgenes. These double-deletion mice were compared to three control groups - WT, EC VEGF gene deletion alone and myofibre VEGF gene deletion alone. Three weeks after initiating gene deletion, Skm/EC-VEGF^-/- mice, but not SkmVEGF^-/- or EC-VEGF^-/- mice, reached exhaustion 40 min sooner than WT mice in treadmill tests (P = 0.002). WT, SkmVEGF^-/- and EC-VEGF^-/- , but not Skm/EC-VEGF^-/- , mice gained weight over the 3 weeks. Capillary density, fibre area and capillary: fibre ratio in soleus, plantaris, gastrocnemius and cardiac papillary muscle were similar across the groups. Phosphofructokinase and pyruvate dehydrogenase activities increased only in Skm/EC-VEGF^-/- mice. These data suggest that deletion of the VEGF gene simultaneously in endothelial cells and myofibres, while reducing treadmill endurance and despite compensatory augmentation of glycolysis, is not required for muscle capillary maintenance. Reduced endurance remains unexplained, but may possibly be related to a role for VEGF in controlling perfusion of contracting muscle.

Bifidobacterium longum subsp. longum OLP-01 Supplementation during Endurance Running Training Improves Exercise Performance in Middle- and Long-Distance Runners: A Double-Blind Controlled Trial

Bifidobacterium longum subsp. longum Olympic No. 1 (OLP-01) has been shown in previous animal experiments to improve exercise endurance performance, but this effect has not been confirmed in humans, or more particularly, in athletes. Toward this end, the current study combined OLP-01 supplementation with regular exercise training in well-trained middle- and long-distance runners at the National Taiwan Sport University. The study was designed as a double-blind placebo-controlled experiment. Twenty-one subjects (14 males and seven females aged 20–30 years) were evenly distributed according to total distance (meters) traveled in 12 min to one of the following two groups: a placebo group (seven males and three females) and an OLP-01 (1.5 × 10¹⁰ colony forming units (CFU)/day) group (seven males and four females). All the participants received placebo or OLP-01 supplements for five consecutive weeks consisting of three weeks of regular training and two weeks of de-training. Before and after the experiment, the participants were tested for 12-min running/walking distance, and body composition, blood/serum, and fecal samples were analyzed. The results showed that OLP-01 significantly increased the change in the 12-min Cooper’s test running distance and the abundance of gut microbiota. Although no significant change in body composition was found, OLP-01 caused no adverse reactions or harm to the participants’ bodies. In summary, OLP-01 can be used as a sports nutrition supplement, especially for athletes, to improve exercise performance.

Runners' metabolomic changes following marathon

Introduction

Marathon, as a long-distance aerobic exercise, has become a fashionable or popular sport. However, little is known about the holistic metabolic changes occurring within the serum metabolome of athletes after the completion of a marathon.

Objectives

The goal of current study was to have an in-depth understanding of the impact of marathon on human metabolomics as well as the relationships among a variety of metabolites.

Methods

The 20 studied subjects were all adult males who participated in a marathon. The serum samples of these participants were collected before and after the marathon and the biochemical metabolites in the serum were identified by an untargeted two-dimensional gas chromatography time-of-flight mass spectrometry.

Results

All participants completed the marathon within 3 h. Compared to those before exercise, serum urea and creatine kinase, as well as cortisol, elevated significantly (p < 0.05), whereas testosterone decreased significantly (p < 0.01). Metabolomic analysis showed that, compared to those before the competition, metabolites pyruvic acid, glyceric acid, malic acid, cis-aconitic acid, galacturonic acid, methyl fumaric acid, maltotriose, and others increased significantly after the competition (p < 0.05), but glucosamine and O-succinyl-L-homoserine decreased significantly (p < 0.05). Amino acid indexes, such as alanine, L-tyrosine and phenylalanine, increased significantly after exercise compared with those before exercise (p < 0.05), whereas serine, valine and asparagine decreased significantly (p < 0.05). Lipid metabolism indexes, glycerol, glyceric acid, octanoic acid, and quinic acid increased significantly (p < 0.05). Theophylline, xanthine and other indicators of caffeine metabolism increased significantly (p < 0.05). Furthermore, marathon performance, fat percentage, VO₂max, and hemoglobin were correlated with the serum metabonomic indicators, so were serum testosterone and cortisol.

Conclusion

These results illustrate that the metabolism of glucose and lipid of the athletes was enhanced following the marathon match. In addition, the metabolism of glucosamine was decreased and the metabolism of caffeine was increased. Our data provide new insights for marathon performance and nutritional status.

Metabolite Shifts Induced by Marathon Race Competition Differ between Athletes Based on Level of Fitness and Performance: A Substudy of the Enzy-MagIC Study

This study compared metabolite shifts induced by training for, participation in, and recovery from a marathon race competition among athletes divided into three groups based on fitness (relative maximum oxygen uptake (VO₂max)) and performance levels (net running time). Plasma samples from 76 male runners participating in the Munich Marathon were analyzed for metabolite shifts using a targeted metabolomics panel. For the entire cohort of runners, pronounced increases were measured immediately after the race for plasma concentrations of acylcarnitines (AC), the ratio (palmitoylcarnitine + stearoylcarnitine)/free carnitine that is used as a proxy for the activity of the mitochondrial enzyme carnitine palmitoyltransferase, and arginine-related metabolites, with decreases in most amino acids (AA) and phospholipids. Plasma levels of AA and phospholipids were strongly increased 24 and 72 h post-race. Post-race plasma concentrations of AC and arginine-related metabolites were higher in the low compared to top performers, indicating an accumulation of fatty acids and a reliance on protein catabolism to provide energy after the marathon event. This study showed that marathon race competition is associated with an extensive and prolonged perturbation in plasma metabolite concentrations with a strong AC signature that is greater in the slower, less aerobically fit runners. Furthermore, changes in the arginine-related metabolites were observed.

Pacing Strategy Affects the Sub-Elite Marathoner's Cardiac Drift and Performance

The question of cardiac strain arises when considering the emerging class of recreational runners whose running strategy could be a non-optimal running pace. Heart rate (HR) monitoring, which reflects exercise intensity and environmental factors, is often used for running strategies in marathons. However, it is difficult to obtain appropriate feedback for only the HR value since the cardiovascular drift (CV drift) occurs during prolonged exercise. The cardiac cost (CC: HR divided by running velocity) has been shown to be a potential index for evaluation of CV drift during the marathon race. We sought to establish the relationship between recreational marathoners' racing strategy, cardiac drift, and performance. We started with looking for a trend in the speed time series (by Kendall's non-parametric rank correlation coefficient) in 280 (2 h30-3 h40) marathoners. We distinguished two groups, with the one gathering the large majority of runners (n = 215, 77%), who had a significant decrease in their speed during the race that appeared at the 26th km. We therefore named this group of runners the "fallers." Furthermore, the fallers had significantly lower performance (p = 0.006) and higher cardiac drift (p < 0.0001) than the non-fallers. The asymmetry indicator of the faller group runners' speed is negative, meaning that the average speed of this category of riders is below the median, indicating that they ran more than the half marathon distance (56%) above their average speed before they "hit the wall" at the 26th km. Furthermore, we showed that marathon performance was correlated with the amplitude of the cardiac drift (r = 0.18, p = 0.0018) but not with those of the increase in HR (r = 0.01, p = 0.80). In conclusion, for addressing the question of the cardiac drift in marathon, which is very sensitive to the running strategy, we recommend to utilize the cardiac cost, which takes into account the running speed and that could be implemented in the future, on mobile phone applications.

Exercise-Induced Muscle Damage and Cardiac Stress During a Marathon Could be Associated with Dietary Intake During the Week Before the Race

Adequate food intake is important prior to endurance running competitions to facilitate adequate exercise intensity. However, no investigations have examined whether dietary intake could prevent exercise-induced muscle damage (EIMD) and cardiac stress (EICS). Thus, this study’s objective was to determine the associations between EIMD, EICS and endurance athlete diets one week before a marathon race. Sixty-nine male runners participated in this study. Food intake during the week prior to the race was collected through a seven-day weighed food record. Dietary intake on race day was also recorded. At the end of the marathon, blood samples were drawn to determine serum creatine kinase (CK) and myoglobin, and muscle–brain isoform creatine kinase (CK-MB), prohormone of brain natriuretic peptide (NT-proBNP), cardiac troponin I (TNI), and cardiac troponin T (TNT) concentration as markers of EIMD and EICS, respectively. To determine the association between these variables, a stepwise regression analysis was carried out. The dependent variable was defined as EIMD or EICS and the independent variables were defined as the number of servings within each different food group. Results showed that the intake of meat during the previous week was positively associated with post-race CK (Standardized Coefficients (β) = 0.643; p < 0.01) and myoglobin (β = 0.698; p < 0.001). Vegetables were negatively associated the concentration of post-race CK (β = −0.482; p = 0.002). Butter and fatty meat were positively associated with NT-proBNP (β = 0.796; p < 0.001) and TNI (β = 0.396; p < 0.001) post-marathon values. However, fish intake was negatively associated with CK (β = −0.272; p = 0.042), TNI (β = −0.593; p < 0.001) and TNT (β = −0.640; p = 0.002) post-marathon concentration. Olive oil was negatively associated with TNI (β = −0.536; p < 0.001) and TNT (β = −0.415; p = 0.021) values. In conclusion, the consumption of meat, butter, and fatty meat might be associated with higher levels of EIMD and EICS. On the other hand, fish, vegetables, and olive oil might have a protective role against EIMD and EICS. The selection of an adequate diet before a marathon might help to reduce some of the acute burdens associated with marathon races.

Predicting Recreational Runners' Marathon Performance Time During Their Training Preparation

Esteve-Lanao, J, Del Rosso, S, Larumbe-Zabala, E, Cardona, C, Alcocer-Gamboa, A, and Boullosa, DA. Predicting marathon performance time throughout the training preparation in recreational runners. J Strength Cond Res XX(X): 000-000, 2019-The objective of this study was to predict marathon performance at different time points along the season using different speeds derived from ventilatory thresholds and running economy (RE). Sixteen recreational runners (8 women and 8 men) completed a 16-week marathon training macrocycle. Aerobic threshold (AeT), anaerobic threshold (AnT), and maximal oxygen uptake were assessed at the beginning of the season, whereas speeds eliciting training zones at AeT and AnT, and RE were evaluated at 5-time points during the season (M1-M5). Analyses of variance and hierarchical regression analyses were conducted. Training improved AeT and AnT speeds at M2 vs. M1 (p = 0.001) and remained significantly higher at M3, M4, and M5 (p = 0.001). There was a significant effect of time (p = 0.003) for RE, being higher at M4 and M5 compared with M1 and M3. Significant correlations were found between marathon performance and speeds at AeT and AnT at every time point (r = 0.81-0.94; p < 0.05). Speed at AnT represented the main influence (65.9 and 71.41%) in the final time prediction at M1 and M2, whereas speed at AeT took its place toward the end of the macrocycle (76.0, 80.4, and 85.0% for M3, M4, and M5, respectively). In conclusion, assessment of speeds at AeT and AnT permits for reasonable performance prediction during the training preparation, therefore avoiding maximal testing while monitoring 2 fundamental training speeds. Future research should verify if these findings are applicable to runners of different levels and other periodization models.

Heart rate cost of running in track estimates velocity associated with maximal oxygen uptake

BACKGROUND

Running velocity associated with VO₂max (vVO₂max) is a parameter widely used for exercise prescription and is related to endurance performance. However, the vVO₂max determination usually requires a maximal effort test and equipped laboratory for expired gas analysis, what make difficulty its assessment.

OBJECTIVE

We aimed to test the validity of a simple method of vVO₂max prediction through the heart rate cost of running (HRC) in a submaximal 6-min running test, both in treadmill and in a 400-meter track.

METHODS

Male recreational runners (n = 16; 30.3 ± 8.0 years; VO₂max of 46.2 ± 3.2 ml·kg^-1·min^-1) randomly underwent an incremental test in treadmill with gas analysis, and a 3000-m time trial in a track, to determine vVO₂max. Before every maximal test, participants also performed a submaximal 6-min running (~85% HRmax), both in the treadmill and in a track, to assess HRC (bpm^-1m·min^-1) by dividing the submaximal running velocity by its respective HR. The vVO₂max (km·h^-1) was predicted by dividing the HRmax (bpm)/HRC (bpm^-1m·min^-1).

RESULTS

No differences were verified (p > .05) among vVO₂max determined both in the treadmill (13.8 ± 0.9 km·h^-1) and track (13.6 ± 0.9 km·h^-1) to those predicted by the HRC method both in treadmill (13.5 ± 0.8 km·h^-1) and track (13.6 ± 1.0 km·h^-1). The vVO₂max measured directly with expired gas analysis was highly correlated with vVO₂max estimated through HRC in treadmill and track (p < .05). Additionally, the intraclass correlation coefficient (ICC) and Bland-Altman technique revealed good agreement and reliability classified with substantial agreement [ICC = 0.673 (95% CI 0.064-0.886; p = .019)] and almost perfect agreement [ICC = 0.870 (95% CI 0.628-0.955 p = .0001)] between methods to identify vVO₂max, respectively.

CONCLUSION

A submaximal 6-min exercise test protocol to assess HRC of running was considered valid to estimate vVO₂max of recreational runners both in treadmill and outdoor track.

Utilizing Dietary Nutrient Ratios in Nutritional Research: Expanding the Concept of Nutrient Ratios to Macronutrients

We recently showed that using micronutrient ratios in nutritional research might provide more insights into how diet affects metabolism and health outcomes, based on the notion that nutrients, unlike drugs, are not consumed one at a time and do not target a single metabolic pathway. In this paper, we present a concept of macronutrient ratios, including intra- and inter-macronutrient ratios. Macronutrient intakes from food only, from the What We Eat in America website (summarized National Health and Nutrition Examination Survey data) were transposed into Microsoft Excel to generate ratios. Overall, the dietary ratios of macronutrients may be more revealing and useful in epidemiology and in basic nutritional research than focusing on individual protein, fat, and carbohydrate intakes. While macronutrient ratios may be applied to all types of nutritional research, nutritional epidemiology, and, ultimately, dietary guidelines, the methodology required has not been established yet. In the meantime, intra- and inter-macronutrient ratios may serve as a measure of individual and total macronutrient quality.

Relationship between oxygen cost and C-reactive protein response to marathon running in college recreational runners

Purpose

Individual variations in response of C-reactive protein (CRP) to acute strenuous exercise are less well known. The purpose of this study was to investigate the relationship between running economy and systemic inflammation following a marathon.

Materials and methods

Sixteen college recreational runners participated in this study. To measure maximal oxygen uptake and running economy, the treadmill running test was performed 1-2 weeks before the marathon race. Running economy was defined as oxygen cost (mL/kg/km) at submaximal running. CRP and muscle damage markers (creatine kinase and lactate dehydrogenase) were measured before and 1, 2, and 3 days after the race.

Results

All subjects completed the race in 4 hours 7 minutes 43 seconds±44 minute 29 seconds [mean±SD]. The marathon running significantly increased CRP and muscle damage markers. The levels of inflammation and muscle damage peaked after 1 day and remained high throughout the 3-day recovery period compared to that before the race. Spearman correlation analysis showed that the change in CRP level was significantly positively correlated with oxygen cost (r=0.619, P=0.011) but not maximal oxygen uptake. There was no significant relationship in responses between muscle damage markers and CRP.

Conclusion

These findings suggest that running economy is related to postmarathon race CRP response. Further study to clarify the cause of the relationship and clinical significance of transient increase in CRP is necessary.

Considerations for ultra-endurance activities: part 1- nutrition

Ultra-endurance activities (≥ 4h) present unique challenges that, beyond fatigue, may be exacerbated by sub-optimal nutrition during periods of increased requirements and compromised gastrointestinal function. The causes of fatigue during ultra-endurance exercise are multi-factorial. However, mechanisms can potentially include central or peripheral fatigue, thermal stress, dehydration, and/or endogenous glycogen store depletion; of which optimising nutrition and hydration can partially attenuate. If exercise duration is long enough (e.g. ≥ 10h) and exercise intensity low enough (e.g. 45-60% of maximal oxygen uptake), it is bio-energetically plausible that ketogenic adaptation may enhance ultra-endurance performance, but this requires scientific substantiation. Conversely, the scientific literature has consistently demonstrated that daily dietary carbohydrates (3-12g/kg/day) and carbohydrate intake (30-110g/h) during ultra-endurance events can enhance performance at individually tolerable intake rates. Considering gastrointestinal symptoms are common in ultra-endurance activities, effective dietary prevention and management strategies may provide functional, histological, systemic, and symptomatic benefits. Taken together, a well-practiced and individualized fuelling approach is required to optimize performance in ultra-endurance events.

Modelling perception-action coupling in the phenomenological experience of "hitting the wall" during long-distance running with exercise induced muscle damage in highly trained runners

Background

“Hitting the wall” (HTW) can be understood as a psychophysiological stress process characterised by (A) discrete and poignant onset, (B) dynamic interplay between physiological, affective, motivational, cognitive, and behavioural systems, and (C) unintended alteration of pace and performance. A preceding companion article investigated the psychophysiological responses to 20-km self-paced treadmill time trials after producing exercise-induced muscle damage (EIMD) via a standardised muscle-lengthening contraction protocol.

Methods

A 5-step procedure was applied determining the extent to which the observed data fit the hypothesised cause-effect relationships. Running with EIMD negatively impacts performance fatigability via (A) amplified physiological responses and a non-adaptive distress response and (B) deterioration in perceived fatigability: increase in perceived physical strain precedes decrease in valence, which in turn precedes increase in action crisis, eventually dissolving the initially aspired performance goal.

Results

First, haematological indicators of EIMD predicted increased blood cortisol concentration, which in turn predicted increased performance fatigability. Second, perceived physical strain explained 44% of the relationship between haematological indicators of EIMD and valence, which in turn predicted increased action crisis, which in turn predicted increased performance fatigability. The observed data fitted the hypothesised dual-pathway model well with good model-fit indices throughout.

Conclusions

The hypothesised interrelationships between physiological strain, perception, and heuristic and deliberative decision-making processes in self-regulated and goal-directed exercise behaviour were applied, tested, and confirmed: amplified physiological strain and non-adaptive distress response as well as strain-perception-thinking-action coupling impact performance fatigability. The findings provide novel insights into the psychophysiological processes that underpin the phenomenological experience of HTW and alteration in pacing behaviour and performance.

Electronic supplementary material

The online version of this article (10.1186/s40798-018-0144-1) contains supplementary material, which is available to authorized users.

Pacing of an Untrained 17-Year-Old Teenager in a Marathon Attempt

Although there has been increased scientific interest for physiological responses to endurance running and pacing, limited information exists for adolescents participating in endurance events. We are reporting the case of an untrained 17-year-old female teenager (body mass 50.6 kg, height 167 cm and body mass index 18.1 kg/m²) who intended to run a marathon within 6 hours without preparation. The young woman missed her goal by just 2 km. When the average running speed per hour was analysed, there was a major effect of race hour on running speed (p = 0.013, η² = 0.320), where the running speed in the fifth hour (6.3 ± 0.2 km/h) was lower than in the second hour (6.9 ± 0.1 km/h). Despite a progressive decrease in running speed, she was still able to put on a final spurt, indicated by a 4^th degree non-linear regression (R²=0.55). Creatine-kinase reached the initial value again after 5 days and the fall of hemoglobin and hematocrit indicated expansion of plasma volume. Running a marathon as a teenager did not impair physical health, especially when a self-selected pace was adopted. Laboratory parameters during running showed similar changes as have been reported for teenagers and adults after running a marathon. Increased values returned to base line within a few days. In summary, a female teenager at the age of 17 years without specific running preparation is able to achieve nearly a marathon distance during 6 hours of continuous running without harmful effects on health.

Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes

BACKGROUND

Low-carbohydrate diets have recently grown in popularity among endurance athletes, yet little is known about the long-term (>4wk) performance implications of consuming a low-carbohydrate high fat ketogenic diet (LCKD) in well-trained athletes.

METHODS

Twenty male endurance-trained athletes (age 33±11y, body mass 80±11kg; BMI 24.7±3.1kg/m²) who habitually consumed a carbohydrate-based diet, self-selected into a high-carbohydrate (HC) group (n=11, %carbohydrate:protein:fat=65:14:20), or a LCKD group (n=9, 6:17:77). Both groups performed the same training intervention (endurance, strength and high intensity interval training (HIIT)). Prior to and following successful completion of 12-weeks of diet and training, participants had their body composition assessed, and completed a 100km time trial (TT), six second (SS) sprint, and a critical power test (CPT). During post-intervention testing the HC group consumed 30-60g/h carbohydrate, whereas the LCKD group consumed water, and electrolytes.

RESULTS

The LCKD group experienced a significantly greater decrease in body mass (HC -0.8kg, LCKD -5.9kg; P=0.006, effect size (ES): 0.338) and percentage body fat percentage (HC -0.7%, LCKD -5.2%; P=0.008, ES: 0.346). Fasting serum beta-hydroxybutyrate (βHB) significantly increased from 0.1 at baseline to 0.5mmol/L in the LCKD group (P=0.011, ES: 0.403) in week 12. There was no significant change in performance of the 100km TT between groups (HC -1.13min·s, LCKD -4.07min·s, P=0.057, ES: 0.196). SS sprint peak power increased by 0.8 watts per kilogram bodyweight (w/kg) in the LCKD group, versus a -0.1w/kg reduction in the HC group (P=0.025, ES: 0.263). CPT peak power decreased by -0.7w/kg in the HC group, and increased by 1.4w/kg in the LCKD group (P=0.047, ES: 0.212). Fat oxidation in the LCKD group was significantly greater throughout the 100km TT.

CONCLUSIONS

Compared to a HC comparison group, a 12-week period of keto-adaptation and exercise training, enhanced body composition, fat oxidation during exercise, and specific measures of performance relevant to competitive endurance athletes.

Effects of Low Versus Moderate Glycemic Index Diets on Aerobic Capacity in Endurance Runners: Three-Week Randomized Controlled Crossover Trial

The glycemic index (GI) of ingested carbohydrates may influence substrate oxidation during exercise and athletic performance. Therefore, the aim of this study was to assess the effect of low- and moderate-GI three-week diets on aerobic capacity and endurance performance in runners. We conducted a randomized crossover feeding study of matched diets differing only in GI (low vs. moderate) in 21 endurance-trained runners. Each participant consumed both, low- (LGI) and moderate-GI (MGI) high-carbohydrate (~60%) and nutrient-balanced diets for three weeks each. At the beginning and end of each diet, participants had their aerobic capacity and body composition measured and performed a 12-min running test. After LGI, time to exhaustion during incremental cycling test (ICT) and distance covered in the 12-min run were significantly increased. The MGI diet led to an increase in maximal oxygen uptake (V˙O₂max), but no performance benefits were found after the MGI diet. The LGI and MGI diets improved time and workload at gas exchange threshold (GET) during ICT. The results indicate that a three-week high-carbohydrate LGI diet resulted in a small but significant improvement in athletic performance in endurance runners. Observed increase in V˙O₂max on MGI diet did not affect performance.

50 years of comparative biochemistry: The legacy of Peter Hochachka

Peter Hochachka was an early pioneer in the field of comparative biochemistry. He passed away in 2002 after 4 decades of research in the discipline. To celebrate his contributions and to coincide with what would have been his 80th birthday, a group of his former students organized a symposium that ran as a satellite to the 2017 Canadian Society of Zoologists annual meeting in Winnipeg, Manitoba (Canada). This Special Issue of CBP brings together manuscripts from symposium attendees and other authors who recognize the role Peter played in the evolution of the discipline. In this article, the symposium organizers and guest editors look back on his career, celebrating his many contributions to research, acknowledging his role in training of generations of graduate students and post-doctoral fellows in comparative biochemistry and physiology.

The Crosstalk between the Gut Microbiota and Mitochondria during Exercise

Many physiological changes occur in response to endurance exercise in order to adapt to the increasing energy needs, mitochondria biogenesis, increased reactive oxygen species (ROS) production and acute inflammatory responses. Mitochondria are organelles within each cell that are crucial for ATP production and are also a major producer of ROS and reactive nitrogen species during intense exercise. Recent evidence shows there is a bidirectional interaction between mitochondria and microbiota. The gut microbiota have been shown to regulate key transcriptional co-activators, transcription factors and enzymes involved in mitochondrial biogenesis such as PGC-1α, SIRT1, and AMPK genes. Furthermore, the gut microbiota and its metabolites, such as short chain fatty acids and secondary bile acids, also contribute to host energy production, ROS modulation and inflammation in the gut by attenuating TNFα- mediated immune responses and inflammasomes such as NLRP3. On the other hand, mitochondria, particularly mitochondrial ROS production, have a crucial role in regulating the gut microbiota via modulating intestinal barrier function and mucosal immune responses. Recently, it has also been shown that genetic variants within the mitochondrial genome, could affect mitochondrial function and therefore the intestinal microbiota composition and activity. Diet is also known to dramatically modulate the composition of the gut microbiota. Therefore, studies targeting the gut microbiota can be useful for managing mitochondrial related ROS production, pro-inflammatory signals and metabolic limits in endurance athletes.

Acute Normobaric Hypoxia Increases Post-exercise Lipid Oxidation in Healthy Males

The primary objective of the current study was to determine the effect of moderate normobaric hypoxia exposure during constant load cycling on post-exercise energy metabolism recorded in normoxia. Indirect calorimetry was used to examine whole body substrate oxidation before, during, 40–60 min post, and 22 h after performing 60 min of cycling exercise at two different fractions of inspired oxygen (F_IO₂): (i) F_IO₂ = 0.2091 (normoxia) and (ii) F_IO₂ = 0.15 (hypoxia). Seven active healthy male participants (26 ± 4 years of age) completed both experimental trials in randomized order with a 7-day washout period to avoid carryover effects between conditions. Resting energy expenditure was initially elevated following cycling exercise in normoxia and hypoxia (Δ 0.14 ± 0.05, kcal min⁻¹, p = 0.037; Δ 0.19 ± 0.03 kcal min⁻¹, p < 0.001, respectively), but returned to baseline levels the next morning in both conditions. Although, the same absolute workload was used in both environmental conditions (157 ± 10 W), a shift in resting substrate oxidation occurred after exercise performed in hypoxia while post-exercise measurements were similar to baseline after cycling exercise in normoxia. The additional metabolic stress of hypoxia exposure was sufficient to increase the rate of lipid oxidation (Δ 42 ± 11 mg min⁻¹, p = 0.019) and tended to suppress carbohydrate oxidation (Δ −55 ± 26 mg min⁻¹, p = 0.076) 40–60 min post-exercise. This shift in substrate oxidation persisted the next morning, where lipid oxidation remained elevated (Δ 9 ± 3 mg min⁻¹, p = 0.0357) and carbohydrate oxidation was suppressed (Δ −22 ± 6 mg min⁻¹, p = 0.019). In conclusion, prior exercise performed under moderate normobaric hypoxia alters post-exercise energy metabolism. This is an important consideration when evaluating the metabolic consequences of hypoxia exposure during prolonged exercise, and future studies should evaluate its role in the beneficial effects of intermittent hypoxia training observed in persons with obesity and insulin resistance.

Novel ketone diet enhances physical and cognitive performance

Ketone bodies are the most energy-efficient fuel and yield more ATP per mole of substrate than pyruvate and increase the free energy released from ATP hydrolysis. Elevation of circulating ketones via high-fat, low-carbohydrate diets has been used for the treatment of drug-refractory epilepsy and for neurodegenerative diseases, such as Parkinson's disease. Ketones may also be beneficial for muscle and brain in times of stress, such as endurance exercise. The challenge has been to raise circulating ketone levels by using a palatable diet without altering lipid levels. We found that blood ketone levels can be increased and cholesterol and triglycerides decreased by feeding rats a novel ketone ester diet: chow that is supplemented with (R)-3-hydroxybutyl (R)-3-hydroxybutyrate as 30% of calories. For 5 d, rats on the ketone diet ran 32% further on a treadmill than did control rats that ate an isocaloric diet that was supplemented with either corn starch or palm oil (P < 0.05). Ketone-fed rats completed an 8-arm radial maze test 38% faster than did those on the other diets, making more correct decisions before making a mistake (P < 0.05). Isolated, perfused hearts from rats that were fed the ketone diet had greater free energy available from ATP hydrolysis during increased work than did hearts from rats on the other diets as shown by using [31P]-NMR spectroscopy. The novel ketone diet, therefore, improved physical performance and cognitive function in rats, and its energy-sparing properties suggest that it may help to treat a range of human conditions with metabolic abnormalities.-Murray, A. J., Knight, N. S., Cole, M. A., Cochlin, L. E., Carter, E., Tchabanenko, K., Pichulik, T., Gulston, M. K., Atherton, H. J., Schroeder, M. A., Deacon, R. M. J., Kashiwaya, Y., King, M. T., Pawlosky, R., Rawlins, J. N. P., Tyler, D. J., Griffin, J. L., Robertson, J., Veech, R. L., Clarke, K. Novel ketone diet enhances physical and cognitive performance.

Fat Utilization During High-Intensity Exercise: When Does It End?

Background

This study examined substrate oxidation at high-intensity exercise and aimed to determine when fat oxidation ends (FAT_min). We hypothesized the existence of a connection between the anaerobic threshold (AnT) and FAT_min point.

Methods

Breath-by-breath data obtained from indirect calorimetry during a graded treadmill test were used to measure substrate oxidation and maximal oxygen uptake (VO_2max) on 47 males (30 athletes (ATL) and 17 non-athletes (NATL)). Pearson correlation coefficient (r) and effect size (R²) were used to test correlations between VO₂ at AnT and at FAT_min.

Results

Maximal oxygen uptake (VO_2max) was 56.17 ± 4.95 and 46.04 ± 3.25 ml kg⁻¹ min⁻¹ in ATL and NATL, respectively. In ATL, AnT was observed at 87.57 ± 1.30 % of VO_2max and FAT_min was observed at 87.60 ± 1.60 % of VO_2max. In NATL, AnT and FAT_min were at 84.64 ± 1.10 % of VO_2max and 85.25 ± 1.10 % of VO_2max, respectively. Our data show large correlations between VO₂ at AnT and VO₂ at FAT_min for ATL (r = 0.99, p < 0.01, 95 % CI 0.99 to 1.00) and NATL (r = 0.97, p < 0.01, 95 % CI 0.91 to 0.98). The effect size of correlations for ATL and NATL were 0.98 and 0.94, respectively.

Conclusions

Our results show high correlation between AnT and FAT_min in both ATL and NATL with equal substrate oxidation rates at AnT.