ECSS Paris 2023: OP-PN05
INTRODUCTION: Passive heating may be an alternative or adjunct to exercise to maintain cardiovascular and cerebral function and health. Hot water immersion (HWI) improves peripheral vascular function via shear-mediated mechanisms; however, it remains unclear if acute HWI can improve cerebrovascular function. This study determined the influence of HWI on cerebral haemodynamics and subsequent cerebrovascular reactivity to carbon dioxide (CVRco2) within the internal carotid artery (ICA), an index of cerebrovascular function. METHODS: Fifteen healthy adults (six female, mean age 28 ± 8 years) completed two experimental trials separated by at least 48 hours. Females were tested in the same menstrual cycle phase for both trials. In the HWI trial, participants were immersed in 39°C water to the sternum for 60 min whilst in the CON trial they rested in 21°C air in the same semi-recumbent posture and duration as in the HWI trial. Thermal and haemodynamic variables were assessed throughout trials. CVRco2 was determined before and 45 min after the 60 min HWI and CON interventions by participants breathing four minutes of a hypercapnic gas (6% CO2, 21% O2, N2 balance) whilst ICA blood velocity and diameter were measured by duplex ultrasound. RESULTS: At 60 min of the interventions core body temperature and heart rate were higher on HWI than CON (CON, 36.9 ± 0.3°C; HWI, 38.1 ± 0.3°C, P < 0.001. CON, 60 ± 10 bpm; HWI, 96 ± 13 bpm, P < 0.001). No differences were observed between the HWI and CON interventions for ICA diameter (P = 0.34), ICA blood velocity (P = 0.97), ICA shear rate (P = 0.75) and ICA blood flow (CON, 311 ± 80 ml·min-1; HWI, 338 ± 92 ml·min-1, P = 0.39). Compared to CON, HWI intervention reduced mean arterial blood pressure (CON, 82 ± 7 mmHg; HWI, 67 ± 8 mmHg, P < 0.001), and increased ICA conductance (CON, 3.9 ± 1.3 ml·min-1·mmHg-1; HWI, 5.2 ± 2.0 ml·min-1·mmHg-1, P = 0.03). A 45 min after the interventions no difference was detected for CVRco2 between the trials (CON, pre: 13.9 ± 9.2 to post: 11.3 ± 6.1 ml·min-1·mmHg-1; HWI, pre: 14.6 ± 7.9 to post: 10.9 ± 5.4 ml·min-1·mmHg-1; Interaction P = 0.65). CONCLUSION: HWI reduced blood pressure and increased ICA conductance (i.e. autoregulation) to maintain blood flow to the brain. Nevertheless, despite differences in cerebral vascular tone between interventions, HWI did not influence subsequent cerebrovascular function, as assessed by cerebrovascular reactivity to carbon dioxide. These findings support hot water immersion as an intervention to reduce blood pressure, which if repeated regularly may help to maintain cardiovascular and cerebral health.
Read CV Sam LeaneyECSS Paris 2023: OP-PN05
INTRODUCTION: This study aims to investigate the association between the gut microbiota and physical activity (PA) and physical fitness (PF) in children by comparing extreme levels of PA and PF, in order to provide a basis for the development of individualized exercise nutrition intervention strategies in early childhood. METHODS: PF and PA were assessed in 6,074 children aged 6-9 years using the National Standards for Students Physical Health (2014 Revision) and the International Physical Activity Questionnaire Short Form, respectively. Children in the top 25th percentile (high) and bottom 25th percentile (low) for both PF and PA were selected and categorized into four groups: low PA-low PF, high PA-low PF, low PA-high PF, and high PA-high PF. Thirty participants were randomly selected from each group (total n = 120), and fecal samples were collected for 16S rRNA V3-V4 region gene sequencing. Gut microbiota composition and α and β diversity were analyzed for each group. Between-group differences in α diversity were assessed using the Wilcoxon rank-sum test; for β diversity, PERMANOVA was used to test the significance of between-group differences, and Principal Co-ordinates Analysis and Non-metric Multidimensional Scaling (NMDS) were used for visualization. Linear discriminant analysis effect size analysis was used to identify differentially abundant taxa. Pearson correlation and Mantel tests were used to analyze the correlation between the relative abundance of gut microbiota and exercise performance indicators. RESULTS: At equivalent PA levels, children with high PF showed significantly greater gut microbiota richness and diversity (Chao1, Shannon indices; p < 0.01). The low PA-low PF group was enriched in Gammaproteobacteria (Escherichia coli), linked to dysbiosis and inflammation. The high PA-low PF group was enriched in SCFAs-producing Akkermansia and Bacteroides coprocola. The low PA-high PF group was enriched in fiber-fermenting Clostridia and Faecalibacterium. Community structure differed significantly between the low PA-low PF group and others (p < 0.05). Firmicutes correlated positively with weight, BMI, and sit-ups; Bacteroidetes negatively with BMI; and Proteobacteria positively with vital capacity and long jump, implicating these phyla in energy metabolism, body composition, and athletic performance. CONCLUSION: childrens gut microbiota composition varies significantly based on the combined levels of PA and PF. Children with high PF show greater microbial diversity within similar PA levels, particularly under high PA conditions. PERMANOVA-assessed group differences (weighted vs. unweighted UniFrac NMDS) suggest the low PA-low PF group harbors unique species, potentially linked to its distinct microbial enrichment. PA and PF are associated with gut microbiota composition and potential nutrient metabolism in children. Higher PF correlates with greater gut microbiota diversity and may reflect more efficient nutrient utilization.
Read CV Xiang PanECSS Paris 2023: OP-PN05
INTRODUCTION: Laser therapy, now more referred to as photobiomodulation (PBM), is gaining interest as a non-invasive treatment for various conditions and as a potential means to enhance health and performance. While in vitro and in vivo animal studies provide promising evidence, surprisingly little research has been conducted on the proposed capacity for PBM treatment to activate metabolism in skin and skeletal muscle tissue in vivo in humans. METHODS: In a within-participant study design, 12 healthy, young men and women (6/6 m/f; age: 25±6 y; BMI: 23.3±2.2 kg/m2) received PBM on a randomly chosen leg, while the other leg received sham-treatment (no light emitted, CON). Three cycles of PBM were performed for 5 min 16 sec each, separated by 5 min of rest. During the rest periods the other leg received the sham treatment. In total 16.8 kJ in form of light energy was applied (3 x 5.6 kJ) in PBM using wavelengths of 660, 800, 905 and 970 nm in intermittent Continuous Wave (CW), Pulsed Wave (PW), SuperPulse (SP), and IntenseSuperPulse (ISP) mode. Skin temperature was measured before and after treatment. After the treatment, skin and muscle tissue biopsy samples were collected from both legs at the location where the PBM and sham treatments were applied. Permeabilized muscle fiber bundles were prepared from skeletal muscle tissue to measure mitochondrial respiration in an Oroboros Oxygraph-O2k. Skin tissue was minced, and respiration was analyzed in an Oroboros Oxygraph-O2k. Mitochondrial respiration data were compared between treatments (PBM vs CON) using paired samples t-tests. Skin temperature data were analyzed by a repeated measures ANOVA with time (pre/post) and treatment (PBM/CON) as a within-participants factors. Statistical significance was set at P<0.05. All data in text and figures are expressed as mean±SD. RESULTS: PBM increased skin temperature by 8.0±1.4 °C (P<0.05), with no changes in the control leg (P>0.05). In permeabilized muscle fibers, leak mitochondrial respiration (pyruvate, malate) was not altered by PBM (25.7±6.9 vs 24.2±5.6 pmol/sec/mg dry weight in PBM vs CON, respectively; P=0.37). Furthermore, maximal complex I+II-linked respiration (pyruvate, malate, ADP, glutamate, succinate) did not differ between legs (474±114 vs 467±81 pmol/sec/mg dry weight, respectively; P=0.71). Furthermore, no differences were observed in mitochondrial sensitivity to submaximal ADP levels (apparent ADP half-time: 1310±180 vs 1229±240 µM ADP, respectively; P=0.14). In skin tissue, maximal complex I+II-linked respiration did not differ between legs (2.7±0.8 vs 2.6±0.7 pmol/sec/mg wet weight, respectively; P=0.66). CONCLUSION: A single session of photobiomodulation does not increase mitochondrial respiration in skin or underlying muscle tissue in vivo in humans. The proposed benefits of photobiomodulation via high intensity laser therapy are not attributed to the direct activation of tissue metabolism.
Read CV Thorben AussiekerECSS Paris 2023: OP-PN05