ECSS Paris 2023: OP-PN37
INTRODUCTION: Background: High-intensity interval training (HIIT) is often compared to moderate-intensity continuous exercise. However, these comparisons manipulate intensity and obscure whether delivery mode elicits a unique exercise stimulus. Purpose: We compared metabolic and cardiovascular responses between work-, time-, and intensity domain-matched interval and continuous exercise. METHODS: Methods: Sixteen adults (8 females; 22±5 years, 171.8±12.2 cm, 73.0±14.0 kg) underwent three laboratory visits including: a step-ramp-step cycling test to determine the power outputs (PO) at gas exchange threshold (GET) and respiratory compensation point (RCP), and two randomized work-, intensity-, and time-matched severe-intensity bouts of interval (HIIT) and continuous (HCT) exercise. HIIT consisted of 10, 45-s work intervals at ~140%RCP with 45-s recovery at 80%GET and HCT involved duration-matched constant-PO cycling above RCP (~101-109%RCP); selected to match total work of HIIT. Open-circuit inert gas breathing-derived cardiac output (Q̇) and blood pressure were measured every other interval in HIIT and at matched time points in HCT. Breath-by-breath gas exchange and heart rate were continuously monitored by transmitter belt and mass spectrometer-pneumotach combination. RESULTS: Results: PO averaged 184±78 W in HCT and 240±99 (intervals) and 115±51 W (recoveries) in HIIT. Two-way repeated measures ANOVA revealed main effects of time but not condition for all variables. Peak oxygen uptake did not differ (p=0.438) amongst HIIT (2.81±0.94 L∙min-1), HCT (2.85±1.01 L∙min-1) and ramp exercise (3.01±1.22 L∙min-1). No between-condition differences were observed for peaks in Q̇ (20.7±5.2 vs 19.9±5.6 L∙min-1, HIIT vs HCT, p=0.139), heart rate (180±9 vs 177±11 bpm, p=0.100), stroke volume (116±32 vs 113±32 mL, p=0.271), systolic pressure (179±28 vs 185±32 mmHg, p=0.539), nor arteriovenous oxygen difference (13±22 vs 14±2 mLO2/dL, p=0.167). CONCLUSION: Conclusion: HIIT and HCT elicit comparable acute cardiovascular and metabolic responses. Mode of exercise delivery may not alter the stimulus imposed on the cardiovascular system provided intensity is matched.
Read CV Daniel GregoryECSS Paris 2023: OP-PN37
INTRODUCTION: Regular exercise can benefit cognitive functions in later life (1, 2), but the mediating mechanisms remain unclear. Changes to brain vascular health are hypothesised to underpin training-induced brain health benefits (3, 4). However, how long-term exercise training impacts cerebral haemodynamics in older adults is poorly understood. METHODS: This preregistered cross-sectional study compared cerebral haemodynamics and cognitive functions between untrained and long-term endurance trained (≥10 years) older adults (n = 28 per group, respective age = 66.0 ± 5.3 and 66.2 ± 5.2 years, respective peak oxygen consumption (V̇O2peak) = 28.4 ± 4.7 and 42.3 ± 7.2 mL/kg/min). Multiple post-labelling delay arterial spin labelling (ASL) data were used to estimate cerebral blood flow (CBF) and arterial transit time (ATT) in grey matter at rest. Furthermore, in trained participants, global cerebral oxygen extraction fraction (OEF) was estimated using T2-relaxation-under-spin-tagging (TRUST) data (n = 26). RESULTS: There were no significant between-group differences (trained – untrained) in global CBF (5.6 [-2.6, 13.9] mL/100 g/min, P = 0.197), but global ATT was shorter in trained participants (-0.11 [-0.21, -0.02] seconds, P = 0.031). Within regions fed by anterior cerebral arteries, CBF was greater in trained participants (15.8 [3.2, 29.1] mL/100 g/min), but the effect did not survive multiple comparison adjustment (Padjusted = 0.064). Cognitive functions did not differ between the groups and were not associated with cerebral haemodynamics. OEF was not associated with V̇O2peak in trained participants but was strongly inversely associated with global CBF (β = -0.96 [-1.21, -0.75], P = 0.002). CONCLUSION: In conclusion, older adults engaging with long-term endurance training have shorter ATT, counteracting normal age-related ATT lengthening. Longer-term longitudinal studies are required to confirm training-induced regional CBF elevations, which would also counteract normal age-related CBF declines. There was no evidence of relationships with cognitive functions, although the sample was predominantly healthy, educated, and aged 60 – 70 years. Using multiple post-labelling delays is crucial for future ASL research to isolate CBF and ATT from one another, improving estimation accuracy and delineating between different age-related cerebrovascular mechanisms. 1) Josefsson (2012). J Am Geriatr Soc. https://doi.org/10.1111/jgs.12000. 2) Barha (2017). Frontiers in Neuroendocrinology. https://doi.org/10.1016/j.yfrne.2017.04.002. 3) Bliss (2021). J Cereb Blood Flow Metab. https://doi.org/10.1177/0271678X20957807. 4) Tomoto (2023). J Cereb Blood Flow Metab. https://doi.org/10.1177/0271678X221133861.
Read CV Jack FeronECSS Paris 2023: OP-PN37
INTRODUCTION: Background Aerobic exercise training is known to induce beneficial adaptations in cerebrovascular reactivity (CVR), a key indicator of cerebrovascular health, but the acute response to exercise remains understudied. This is particularly relevant in inactive middle-aged adults, where cerebrovascular regulation may already be compromised. Moreover, the time course and kinetic response of CVR to acute aerobic exercise remain uncharacterised and may provide insight into longer-term adaptations. Therefore, this study examined the acute effects of moderate-intensity continuous training (MICT) and two high-intensity interval training (HIIT) protocols on: 1) hypercapnic CVR, 2) hypocapnic CVR, and 3) kinetic MCAv responses to hypercapnia. METHODS: Methods Seventeen inactive middle-aged adults (10 males, 47.2±8.9 years, V̇O2max 29.2±5.7 ml/kg/min) completed one preliminary and four experimental visits. During the preliminary visit, participants performed a ramp incremental cycle test to exhaustion to determine the gas exchange threshold (GET) and maximal oxygen uptake (V̇O2max), which was verified by a supramaximal test. Participants then completed four time-matched (30 min) experimental conditions on separate days in a counterbalanced order: seated control (CON), MICT performed at 90% GET, and two HIIT conditions [(10x1 min intervals at 70%Δ (HIIE10) or 4x4 min intervals at 20%Δ (HIIT4)], where Δ represents the difference between GET and V̇O2max. Middle cerebral artery blood velocity (MCAv) and end-tidal CO2 (PETCO2) were continuously measured using transcranial doppler ultrasound and a gas analyser. All CVR measures were assessed before, 10 and 60 min following each condition. Hypercapnic CVR was expressed as the absolute change in MCAv per mmHg change in PETCO₂ during 4 min of 6% CO₂ inhalation. Hypocapnic CVR was assessed during 1 min of voluntary hyperventilation performed at 25 breaths.min-1, with MCAv and PETCO₂ changes calculated from the final 10 s. The kinetic response of MCAv to hypercapnia was analysed using a novel mono-exponential model. Two-way repeated-measures ANOVA tested effects of condition and time on CVR, MCAv, PETCO₂, and kinetic parameters RESULTS: Results Baseline PETCO₂ was lower at 10 min vs pre- and 60 min in HIIT10 (Both P≤0.016) and HIIT4 (Both P≤0.021), and lower at 10 min vs CON in all exercise trials (all P≤0.042). Baseline MCAv remained unchanged across all trials (all P≥0.121). CVR to hypercapnia (all P>0.122) and hypocapnia (all P>0.296) was unchanged following all conditions. Kinetic analysis revealed no significant interaction effect for MCAv time delay (P=0.428), time constant (P=0.834) and amplitude (P=0.218). CONCLUSION: Conclusion. These novel findings indicate that CVR remains stable in the acute post-exercise period in inactive middle-aged adults. Furthermore, the absence of change in MCAv kinetics to hypercapnic stimuli after moderate- and high-intensity exercise, offers new insight into the temporal stability of CVR following acute exercise.
Read CV Philip BuysECSS Paris 2023: OP-PN37