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Scientific Programme

Physiology & Nutrition

OP-PN24 - Cardiovascular Physiology I

Date: 04.07.2024, Time: 13:45 - 15:00, Lecture room: Carron 1

Description

Chair TBA

Chair

TBA
TBA
TBA

ECSS Paris 2023: OP-PN24

Speaker A Gabriele Marinari

Speaker A

Gabriele Marinari
University of Calgary, Kinesiology
Canada
"The oxygen uptake dynamics conform to changes in muscle activation and total hemoglobin concentration during constant-work rate exercise."

INTRODUCTION: Patterns of muscle activation and near-infrared spectroscopy (NIRS)-derived total hemoglobin concentration ([THC]; a proxy for the dynamics in red blood cell volume), may have an important role for changes in oxygen uptake (VO2) during exercise. However, the interplay between electromyography (EMG)-derived muscle activation and [THC] when taken as a single variable, and its potential association to V̇O2 during constant-work rate (WR) exercise are yet to be explored. This study investigated the EMG/[THC] ratio and its potential correspondence to the dynamics of VO2 during heavy-intensity exercise. METHODS: Eleven and nine participants were recruited in part one and part two of the study, respectively. The heavy-intensity domain was identified through the step-ramp-step protocol. Part one: participants randomly performed: i) a 21-min square-wave transition from 20 W to a WR corresponding to 75% of the heavy-intensity domain amplitude (CWR); ii) a ramp (20 W·min-1) to the same constant-WR, which was then sustained for 21 min (r-CWR). The CWR and r-CWR trials were repeated to increase the signal-to-noise ratio. Part two: participants performed a 42-min square-wave transition to the same WR, interrupted by a 20-sec period at 20 W between min 21 and 22 (CWRx2). Pulmonary VO2, as well as the root mean square derived from the EMG signal and [THC] from the vastus lateralis, were measured and expressed as a percent of baseline (0%) to end exercise (100%). The EMG/[THC] ratio was calculated and expressed as a percent of its peak value and its end value. The EMG signal was further decomposed using wavelet transform. Significance was set at P<0.05 RESULTS: Part 1: No significant main effect of condition existed for both CWR and r-CWR between the dynamics of VO2 and the dynamics of the EMG/[THC] ratio (P>0.05), which was consistent for all the 21 min pairwise comparisons (all P>0.05). The EMG signal during the CWR condition decreased across time from min 1 (P<0.05), while no differences were observed during the constant-WR portion of the r-CWR condition (P>0.05). No significant main effect of condition for the median power frequency (MPF; Hz) was observed (P>0.05), with a significant time effect (P<0.05) for the CWR condition where MPF was increasing over time, with stable responses during the r-CWR condition (P>0.05). Part 2: No differences in EMG were observed between min 21 and min 22 (i.e., pre and post the 20-sec interruption at 20 W) for the CWRx2 condition (P>0.05). CONCLUSION: This study indicated that the VO2 dynamics during heavy-intensity exercise at constant-WR conform to the changes in EMG/[THC] ratio. This suggests that changes in muscle activation and peripheral oxygen delivery concurrently adjust to support oxidative phosphorylation over time. Further, although muscle activation decreased over time during the CWR condition, MPF increased, suggesting an overall reduced number of recruited muscle fibers, but with a shift to higher-order muscle fibers.

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ECSS Paris 2023: OP-PN24

Speaker B Indyanara Ribeiro

Speaker B

Indyanara Ribeiro
Faculdade de Medicina da Universidade de São Paulo - FM/USP, Rheumatology
Brazil
"Protocol to assess muscle blood flow during cycle ergometer exercise using Doppler ultrasound: descriptive responses and associations with cardiorespiratory parameters and muscle oxygenation"

INTRODUCTION: The assessment of muscle blood flow during whole-body dynamic exercise can offer valuable information about the mechanisms underlying exercise tolerance and fatigue in different populations. However, costs (e.g., magnetic resonance imaging) and/or invasiveness (e.g., intravenous cannulation/contrast injection) are challenging obstacles to wider application, warranting the development of practical, non-invasive, low-cost alternative methods. Objectives: To test the initial validity of a non-invasive ultrasound-based protocol developed to measure muscle blood flow responses during cycle ergometer exercise. METHODS: Twelve healthy participants (7 males/5 females; 28.9±1.4 years) attended the laboratory for a progressive square wave test on an upright cycle ergometer. The test consisted of 4-min stages at each of the four following intensity domains: 1) moderate (36±9% of maximal workload [WLmax]); 2) moderate-to-heavy (46±10% WLmax); 3) heavy (67±7% WLmax); 4) maximal (100% WLmax). After each stage, participants stopped pedalling and stayed still for 60s for the assessment of the right common femoral artery blood flow (CFBF) using a Doppler ultrasound (Logiq E, GE Medical System, China). Additionally, quadriceps oxygenation (oxy-, deoxy- and total haemoglobin [HbO2, HHb, THb], and tissue saturation index [TSI]) were assessed via Near-infrared spectroscopy. Cardiorespiratory variables were evaluated using a metabolic cart. Mean CFBF responses at baseline and after each stage were compared using a One-way repeated measures ANOVA. The associations between CFBF and cardiorespiratory and NIRS responses (changes from baseline) were performed using aggregated data from all participants across all exercise stages using repeated measures correlation analysis (rmcorr, Stata v18.0). Strength of the linear association between the variables tested were calculated via the rmcorr coefficient (rrm). Significance was set at P<0.05. RESULTS: CFBF increased following a "quasi-linear" pattern (baseline=0.26±0.15 L/min; moderate=2.28±1.15 L/min; moderate-to-heavy=2.42±1.39 L/min; heavy=3.93±2.11 L/min; maximal=4.16±2.17; P<0.001). CFBF responses to exercise were strongly and linearly correlated with exercise workload (rrm=0.69, P<0.01) and with HHb (rrm=0.68, P<0.01), VO2 (rrm=0.69, P<0.01) and heart rate (rrm=0.70, P<0.01). Additionally, CFBF responses were moderately or weakly correlated to THb, TSI and oxygen pulse (rrm=0.4-0.59 and P<0.05). CONCLUSION: The results of this study indicate that the proposed protocol may be a valid approach to investigate lower limb muscle blood flow responses during cycle ergometer exercise. This approach can provide a practical and non-invasive alternative to assess muscle blood flow in an applied context.

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ECSS Paris 2023: OP-PN24

Speaker C HUI-MING HUANG

Speaker C

HUI-MING HUANG
University of Taipei, EXERCISE AND HEALTH SCIENCES
Taiwan
"Estimating Metabolism during Varying Workloads of Chemical Corps Personnel Using Non-Invasive Physiological Monitoring"

INTRODUCTION: Chemical Corps personnel wear nuclear, biological, and chemical protective clothing (NBC-PC) for mission operations, increasing metabolic rates and fatigue risk (1,2). Monitoring their physical strain non-invasively aids command in strategizing. The purpose of this study is to develop an estimated model to monitor workload. METHODS: Ten Chemical Corps personnel (male: n = 5, age = 23.6 ± 1.7 years; female: n = 5, age = 24.7 ± 3.9 years) were recruited for a study involving body composition analysis, micro-environment temperature (MT) and humidity (MH), and metabolic equivalents (METs) analysis by using the COSMED K5 wearable metabolic system. They underwent walking tests at 4, 6, and 8 km/h speeds, carrying loads of 0 kg, 10 kg, and 20 kg at ambient conditions 25°c. The statistical method used simple and multiple linear regression analysis to construct the most optimal estimated model with the highest correlation with METs. RESULTS: Simple regression analysis showed heart rate (HR) reserve ratio (HRRratio: HRactivity−HRresting/HRmax−HRresting) had the highest coefficient of determination for METs (R2 = 0.569, p < 0.001). The estimated model was [METs = 3.82+7.70×HRRratio]. Multiple regression analysis showed the combination of HR, HRRratio, and MH had the highest coefficient of determination for METs (R2 = 0.717, p < 0.001). The estimated model was[METs = -15.479+0.261×HR+17.929×HRRratio−0.045×MH] CONCLUSION: The combination of multiple physiological parameters HR, HRRratio, and MH showed a high coefficient of determination for METs estimation. The METs increased by 2.4% to 20.9% when subjects performed activities in NBC-PC compared to standard uniforms (3). Aerobic capacity may be impaired at ambient temperature 35-35.5°C (4). Wearing NBC-PC results in an increase of 5.6°C for light work and 11.2°C for moderate to heavy work (5). The environmental temperature has a significant impact on the workload of individuals wearing NBC-PC. Therefore, this estimated model was only applicable at 25°C. Further research is required for extreme high and low temperature environments to develop specific estimated models. References: 1. Young et al., Aviation, Space and Environmental Medicine, 2000 2. Gómez-Oliva et al., Physiol Behav., 2019 3. Dorman and Havenith, Eur J Appl Physiol., 2009 4. Cuddy, et al., J Therm Biol., 2014 5. McLellan, et al., Compr Physiol., 2013

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ECSS Paris 2023: OP-PN24