Anni Vanhatalo’s research while affiliated with University of Exeter and other places

From a physiological perspective, the delineation between steady-state and non-steady-state exercise, also referred to as the maximal metabolic steady state, holds paramount importance for evaluating athletic performance and designing and monitoring training programs. The critical power and the maximal lactate steady state are two widely used indices to estimate this threshold, yet previous studies consistently reported significant discrepancies between their associated power outputs. These findings have fueled the debate regarding the interchangeability of critical power and the maximal lactate steady state in practice. This paper reviews the methodological intricacies intrinsic to the determination of these thresholds, and elucidates how inappropriate determination methods and methodological inconsistencies between studies have contributed to the documented differences in the literature. Through a critical examination of relevant literature and by integration of our laboratory data, we demonstrate that differences between critical power and the maximal lactate steady state may be reconciled to only a few Watts when applying appropriate and strict determination criteria, so that both indices may be used to estimate the maximal metabolic steady-state threshold in practice. To this end, we have defined a set of good practice guidelines to assist scientists and coaches in obtaining the most valid critical power and maximal lactate steady state estimates.

The nitrate (NO3⁻) reducing bacteria resident in the oral cavity have been implicated as key mediators of nitric oxide (NO) homeostasis and human health. NO3⁻-reducing oral bacteria reduce inorganic dietary NO3⁻ to nitrite (NO2⁻) via the NO3⁻-NO2⁻-NO pathway. Studies of oral NO3⁻-reducing bacteria have typically sampled from either the tongue surface or saliva. The aim of this study was to assess whether other areas in the mouth could contain a physiologically relevant abundance of NO3⁻ reducing bacteria, which may be important for sampling in clinical studies. The bacterial composition of seven oral sample types from 300 individuals were compared using a meta-analysis of the Human Microbiome Project data. This analysis revealed significant differences in the proportions of 20 well-established oral bacteria and highly abundant NO3⁻-reducing bacteria across each oral site. The genera included Actinomyces, Brevibacillus, Campylobacter, Capnocytophaga, Corynebacterium, Eikenella, Fusobacterium, Granulicatella, Haemophilus, Leptotrichia, Microbacterium, Neisseria, Porphyromonas, Prevotella, Propionibacterium, Rothia, Selenomonas, Staphylococcus, Streptococcus and Veillonella. The highest proportion of NO3⁻-reducing bacteria was observed in saliva, where eight of the bacterial genera were found in higher proportion than on the tongue dorsum, whilst the lowest proportions were found in the hard oral surfaces. Saliva also demonstrated higher intra-individual variability and bacterial diversity. This study provides new information on where samples should be taken in the oral cavity to assess the abundance of NO3⁻-reducing bacteria. Taking saliva samples may benefit physiological studies, as saliva contained the highest abundance of NO3⁻ reducing bacteria and is less invasive than other sampling methods. These results inform future studies coupling oral NO3⁻-reducing bacteria research with physiological outcomes affecting human health.

A low carbohydrate, high fat (LCHF) diet in athletes increases fat oxidation but impairs sports performance, potentially due to impaired exercise economy. Dietary nitrate supplementation can improve exercise economy via an increase in nitric oxide production, which is initiated by the reduction of nitrate to nitrite within the oral cavity. This reaction is dependent on the presence of nitrate-reducing oral bacteria, which can potentially be altered by dietary changes, including a LCHF diet. This study explored the effect of a LCHF diet on the oral microbiome and subsequent changes to plasma nitrite concentration following nitrate supplementation. Following five days of LCHF or high carbohydrate (HCHO) control dietary intervention, highly trained male race walkers consumed 140 mL beetroot juice containing 8.4 mmol nitrate; they then provided (a) blood samples for plasma nitrate and nitrite analysis and (b) saliva samples for 16S rRNA sequencing of the oral microbiome. The LCHF diet (n = 13) reduced oral bacterial diversity and changed the relative abundance of the genera Neisseria (+10%), Fusobacteria (+3%), Prevotella (−9%), and Veillonella (−4%), with no significant changes observed following the HCHO diet (n = 11). Following beetroot juice ingestion, plasma nitrite concentrations were higher for the LCHF diet compared to the HCHO diet (p = 0.04). However, the absence of an interaction with the trial (pre–post) (p = 0.71) suggests that this difference was not due to the dietary intervention. In summary, we found an increase in plasma nitrate and nitrite concentrations in response to nitrate supplementation independent of diet. This suggests the oral microbiome is adaptive to dietary changes and can maintain a nitrate reduction capacity despite a decrease in bacterial diversity following the LCHF diet.

Objective The nitrate-nitrite-nitric oxide pathway contributes to blood pressure (BP) regulation in humans. However, it is unknown if the pathway alters arterial haemodynamic parameters derived from reservoir-excess pressure analysis. We therefore determined whether an enhancement/disruption of nitrate-nitrite-nitric oxide pathway by dietary nitrate and antibacterial mouthwash, respectively, would alter reservoir-excess pressure parameters in older adults. Design and method Healthy older adults (n = 30, 71.0 ± 2.6 yrs, 19F, 133 ± 11 mmHg for systolic BP and 70 ± 6 mmHg for diastolic BP) participated in this study. Participants were randomised to either a 2-week active nitrate treatment (BR: ∼12.4 mmol beetroot juice daily as a nitrate source) or 2-week placebo treatment (PL: nitrate-depleted beetroot juice) followed by 2-week washout. They then crossed-over to the alternate treatment which was followed by another 2-week washout. Thereafter, they completed a twice-daily antibacterial mouthwash treatment (MW) for two weeks with the aim of disrupting enterosalivary nitrate circulation. Prior to and following each 2-week treatment, reservoir-excess pressure parameters including reservoir pressure integral, excess pressure integral (INTXSP), systolic rate constant (SRC) and diastolic rate constant were obtained through radial artery tonometry along with brachial systolic and diastolic BP. Aortic pulse wave velocity (aPWV) was estimated as previously described (Hughes et al., Front Physiol 2020;11:550). Results Circulating plasma nitrate [614 (95%CI: 545, 683) microM] and nitrite [0.51 (95%CI: 0.30, 0.72) microM] increased with BR, and decreased with MW [nitrate, -17.1 (95%CI: -28.1, -6.1) microM; nitrite, -0.03 (95%CI:-0.05, -0.01) microM]. Relative to PL, BR reduced brachial systolic BP [-2.0 (95%CI: -3.9, -0.1) mmHg], INTXSP [-0.4 (95%CI: -0.7, -0.1) mmHg·s], and aPWV [-0.2 (95%CI: -0.4, 0.0) m/s]. MW increased brachial systolic [2.0 (95%CI: 0.0, 3.9) mmHg], diastolic [1.2 (95%CI: 0.4, 2.0) mmHg] BP, and decreased SRC [-0.2 (95%CI: -0.3, 0.0) 1/s] relative to PL. Conclusions Favourable (INTXSP with BR) and unfavourable (SRC with MW) alterations in reservoir-excess pressure parameters were observed with 2-week dietary nitrate and antibacterial mouthwash treatments, which was accompanied by a small change in brachial systolic BP. These observations may suggest a potential link between enhancing/disrupting nitrate-nitrite-nitric oxide pathway and cardiovascular health in older adults.