Impairment in maximal lactate steady state after carbon monoxide inhalation is related to training status.

NEW FINDINGS: What is the central question of this study? What is the effect of an elevated carboxyhaemoglobin (COHb) concentration following carbon monoxide inhalation on the maximal lactate steady state (MLSS) in humans and is this effect dependent on aerobic fitness? What is the main finding and its importance? An elevated COHb concentration intensified physiological responses to exercise at the MLSS - including heart rate, ventilation and peripheral fatigue - in general and reduced the MLSS (i.e., destabilized the blood lactate concentration) in trained but not untrained males and females. ABSTRACT: This study investigated whether a lower effective [Hb], induced by carbon monoxide (CO) inhalation, reduces the peak oxygen uptake ( V ̇ O 2 peak ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ ) and the maximal lactate steady state (MLSS) and whether training status explains individual variation in these impairments. Healthy young participants completed two ramp incremental tests (n = 20, 10 female) and two trials at MLSS (n = 16, eight female) following CO rebreathe tests and sham procedures (SHAM) in random orders. All fitness variables were normalized to fat-free mass (FFM) to account for sex-related differences in body composition, and males and females were matched for aerobic fitness. The V ̇ O 2 peak ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ (mean (SD): -4.2 (3.7)%), peak power output (PPO) (-3.3 (2.2)%) and respiratory compensation point (RCP) (-6.3 (4.5)%) were reduced in CO compared with SHAM (P < 0.001 for all), but the gas exchange threshold (-3.3 (7.1)%) was not (P = 0.077). Decreases in V ̇ O 2 peak ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ (r = -0.45; P = 0.047) and PPO (r = -0.49; P = 0.029) in CO were correlated with baseline aerobic fitness. Compared to SHAM, physiological and perceptual indicators of exercise-related stress were exacerbated by CO while cycling at MLSS. Notably, the mean blood lactate concentration ([La]) increased (i.e., Δ[La] >1.0 mM) between 10 min (5.5 (1.4) mM) and 30 min (6.8 (1.3) mM; P = 0.026) in CO, with 9/16 participants classified as unstable. These unstable participants had a higher V ̇ O 2 peak ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ (66.2 (8.5) vs. 56.4 (8.8) ml kg FFM-1  min-1 , P = 0.042) and V ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ at MLSS (55.8 (7.0) vs. 44.3 (7.0) ml kg FFM-1  min-1 , P = 0.006) compared to the stable group. In conclusion, a reduced O2 -carrying capacity decreased maximal and submaximal exercise performance, with higher aerobic fitness associated with greater impairments in both.

Metabolic and Gut Microbiota Responses to Sourdough Pasta Consumption in Overweight and Obese Adults.

Increasing consumer interest in fermented products has driven the emergence of a number of novel foods including shelf-stable sourdough pasta. This study comprehensively examined the impact of fermentation on the microbial composition of the culture, pasta, its subsequent effects on glycemic responses and gut microbiota in overweight men and women (>25 kg/m2) compared to a conventional, non-fermented pasta. Two, randomized crossover trials were performed. Study A examined acute feeding responses to each product wherein fasted participants completed a meal tolerance test comprised of 75 g of conventional or sourdough pasta to examine glycemic responses. Results showed enhanced gastric emptying with sourdough, but no difference in overall blood glucose, insulin or satiety hormone responses between the treatments. Study B consisted of three standard oral glucose tolerance tests as well as fecal collection for sequencing at baseline and following each pasta intervention (150 g or 2 serving/d for 5 days) followed by a 2-week washout period. Results showed no differential impact of either pasta treatment on glucose tolerance. Analysis of fecal bacterial and fungal (mycobiome) microbiota showed no change at the individual species or genus levels. However, fungi were adaptive following chronic pasta consumption with decreases in alpha diversity of fungi following sourdough, but not conventional pasta. This was accompanied by reductions in total fecal short chain fatty acid concentrations. In conclusion, sourdough fermentation did not change the overall glycemic properties of the pasta, incretin responses or bacterial gut microbiota, but appears to impact microbiome fungal community structure with chronic consumption.