Dynamics of Gut Microbiota and Short-Chain Fatty Acids during a Cycling Grand Tour Are Related to Exercise Performance and Modulated by Dietary Intake.

BACKGROUND: Regular exercise has been described to modify both the diversity and the relative abundance of certain bacterial taxa. To our knowledge, the effect of a cycling stage race, which entails extreme physiological and metabolic demands, on the gut microbiota composition and its metabolic activity has not been analysed. OBJECTIVE: The aim of this cohort study was to analyse the dynamics of faecal microbiota composition and short-chain fatty acids (SCFAs) content of professional cyclists over a Grand Tour and their relationship with performance and dietary intake. METHODS: 16 professional cyclists competing in La Vuelta 2019 were recruited. Faecal samples were collected at four time points: the day before the first stage (A); after 9 stages (B); after 15 stages (C); and on the last stage (D). Faecal microbiota populations and SCFA content were analysed using 16S rRNA sequencing and gas chromatography, respectively. A principal component analysis (PCA) followed by Generalised Estimating Equation (GEE) models were carried out to explore the dynamics of microbiota and SCFAs and their relationship with performance. RESULTS: Bifidobacteriaceae, Coriobacteriaceae, Erysipelotrichaceae, and Sutterellaceae dynamics showed a strong final performance predictive value (r = 0.83, ranking, and r = 0.81, accumulated time). Positive correlations were observed between Coriobacteriaceae with acetate (r = 0.530) and isovalerate (r = 0.664) and between Bifidobacteriaceae with isobutyrate (r = 0.682). No relationship was observed between SCFAs and performance. The abundance of Erysipelotrichaceae at the beginning of La Vuelta was directly related to the previous intake of complex-carbohydrate-rich foods (r = 0.956), while during the competition, the abundance of Bifidobacteriaceae was negatively affected by the intake of simple carbohydrates from supplements (r = -0.650). CONCLUSIONS: An ecological perspective represents more realistically the relationship between gut microbiota composition and performance compared to single-taxon approaches. The composition and periodisation of diet and supplementation during a Grand Tour, particularly carbohydrates, could be designed to modulate gut microbiota composition to allow better performance.

Frequent participation in high volume exercise throughout life is associated with a more differentiated adaptive immune response.

Exercise induces changes in the immune system depending on its intensity and duration. For example, transient states of immunodepression can be induced after acute intense physical activity whereas beneficial anti-inflammatory effects of moderate chronic exercise on many diseases and longevity have been described. To study the impact of high volume exercise over a lifetime on aspects of immunity we compared immunological features of 27 young and 12 elderly athletes with 30 young and 26 elderly non-athletes stratified by their CMV serostatus. We characterized blood leukocyte and lymphocyte subpopulations by flow cytometry, quantified TREC content, and measured activation and proliferation ability of T-lymphocytes in the presence of anti-CD3. NK-cells functionality was determined in response to K-562, 721.221 and 721.221-AEH cell-lines. High volume physical activity reduced the total number of circulating leukocytes, neutrophils, and lymphocytes. In the lymphocyte compartment, athletes had higher frequencies of NK-cells and CD8+ T-lymphocytes, whereas CD4+ T-lymphocytes were present at significantly lower levels in CMV-seropositive athletes. We found, in the high volume physical activity individuals, a higher degree of differentiation in CD4+ T-lymphocytes. CD8+ T-lymphocytes from young athletes had reduced TREC content and lower frequencies of recent thymic emigrants. Furthermore, the functional ability of CD4+ and CD8+ T-lymphocytes was significantly impaired in young but not in elderly athletes, and may be compensated for significantly higher activation and degranulation of NK-cells. In conclusion, high volume exercise throughout life appears to be associated with increased levels of biomarkers that are associated with an aging immune system, which are partially reduced with physiological aging.

Exercise intensity during off-road cycling competitions.

PURPOSE: This study was designed to quantify and describe the intensity profile of cross-country mountain-biking races using heart rate (HR) recorded during competitions. METHODS: Nine mountain bikers participated in four cross-country circuit races of international and national levels. Each cyclist was tested before the competitions to determine lactate threshold (LT), the onset of blood lactate accumulation (OBLA4), and the relationship between percentage of maximum HR and percentage of VO(2max). RESULTS: To control for intersubject variability, only the five off-road cyclists who completed all four competitions were included in the statistical analysis. The four races' mean absolute and relative time expressed in percentage of race duration (147 +/- 15 min) spent in the EASY(ZONE) (HR below LT) were 27 +/- 16 min and 18 +/- 10%, in the MODERATE(ZONE) (HR between LT and OBLA4) were 75 +/- 19 min and 51 +/- 9%, and in the HARD(ZONE) (HR above OBLA4) were 44 +/- 21 min and 31 +/- 16%. The average HR was 171 +/- 6 beats x min(-1), corresponding to 90 +/- 3% of maximum (84 +/- 3% of VO(2max). CONCLUSION: This study shows that cross-country events are conducted at very high intensity, especially at the start of the race. Coaches must take into account the distribution of the effort and the high exercise intensity characteristic of mountain-biking cross-country events when prescribing specific training programs.

Diagnosing external iliac endofibrosis by postexercise ankle to arm index in cyclists.

PURPOSE: The aim of this study was to determine a noninvasive method of evaluating external iliac endofibrosis in cyclists. METHODS: Eighteen highly trained male cyclists were divided into two groups: a pathology group (PG; 3 professional and 4 elite) and a control group (CG; 6 professional and 5 elite). Mean age was 26 +/- 6.1 yr for the PG and 24 +/- 4.09 for the CG. We studied humeral and tibial posterior pressure by using Doppler ultrasound and the ankle to arm index (AAI) before and after an incremental exercise test, performed on bike-ergometer until exhaustion. A Wilcoxon test was used to compare pressures and AAI in the PG. A Mann-Whitney test was used to compare the PG with the CG. Fisher discriminant analysis was done to obtain a classification of the legs in ill or normal legs. RESULTS: The minimal AAI achieved in the PG was 0.76 +/- 0.13 for the normal leg (NL) and 0.35 +/- 0.04 for the ill leg (IL). We found significant differences (P < 0.01) from the 1st to 4th minute after exercise between the NL and the IL in the PG, and from the 1st to 10th minute after exercise between the IL and CG. We found significant differences in leg pressures between NL and IL in PG from the 1st to 4th minute (P < 0.01), and from the 1st to the 10th minute after exercise between CG and IL in the PG. Through discriminant analysis, we obtained a classification of the legs as ill or normal by applying a mathematical function at each recovery time studied. CONCLUSIONS: AAI and leg pressures response to maximal exercise is a valid and noninvasive method for the evaluation of external iliac endofibrosis.