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Scientific Programme

Physiology & Nutrition

OP-PN05 - Physiology 1

Date: 03.07.2024, Time: 14:45 - 16:00, Lecture room: Alsh 1

Description

Chair TBA

Chair

TBA
TBA
TBA

ECSS Paris 2023: OP-PN05

Speaker A Milan Betz

Speaker A

Milan Betz
Maastricht University, Department of Human Biology, Institute of Nutrition and Translational Research in Metabolism (NUTRIM) and Department of Internal Medicine, School for Cardiovascular Diseases (CARIM)
Netherlands
"Aerobic preconditioning does not further augment muscle hypertrophy during subsequent resistance exercise training in healthy older adults"

INTRODUCTION: Resistance exercise training is an effective treatment strategy to counteract the age-related loss of muscle mass and strength in older adults. However, there is a large inter-individual variation in muscle fiber hypertrophy following resistance exercise training in older adults. It has been hypothesized that an increase in muscle fiber capillarization and perfusion capacity are prerequisite to maximize muscle hypertrophy during resistance exercise training in older adults. We assessed whether 8 weeks of aerobic exercise preconditioning, to improve muscle fiber capillarization and perfusion capacity, augments the gains in muscle mass and strength during subsequent resistance exercise training in older adults. METHODS: In a randomized parallel design, thirty-four healthy older adults (71±5 y) participated in 12 weeks of progressive resistance exercise training, preceded by either 8 weeks of aerobic preconditioning (AER) or no exercise control (CON). Muscle strength (1RM), aerobic capacity (VO2peak test), and muscle fiber characteristics (immunohistochemistry) were assessed at baseline, following 8 weeks of AER or CON, and after subsequent 12 weeks of resistance exercise training. Femoral artery blood flow and vastus lateralis muscle microvascular perfusion kinetics were assessed at baseline and following 8 weeks of AER or CON intervention. Thigh muscle volume (MRI-scan) was assessed before and after 12 weeks of resistance exercise training. Data were analyzed by two-way repeated-measures ANOVA. A statistical level of P<0.05 was accepted. All data are expressed as mean±SD. RESULTS: Aerobic exercise preconditioning increased type I (C/Fi :+19±19%, P<0.05) and type II (C/Fi: +35±37%, P<0.05) muscle fiber capillarization, with no changes in the CON group (C/Fi Type I: +0±17% Type II: -3±26%). Whereas femoral artery blood flow remained unchanged, the vastus lateralis muscle microvascular perfusion capacity tended (interaction effect, P=0.051) to be lower during post-exercise recovery following aerobic exercise preconditioning, with no changes in the CON group. Subsequent resistance exercise training increased 1RM leg press (+16±10% vs +12±8%, respectively, P<0.001) and thigh muscle volume (+0.42±0.69 vs +0.31±0.62 L, respectively, P<0.001), with no differences between AER and CON group (interaction effects, P>0.4). No differences were observed in type I and type II muscle fiber hypertrophy in response to the entire intervention program between groups (interaction effect, P>0.5). CONCLUSION: Aerobic exercise preconditioning increases in type I and type II muscle fiber capillarization in healthy older adults. Aerobic exercise preconditioning does not further increase muscle hypertrophy during subsequent resistance exercise training in healthy older adults. Both structural and functional microvascular characteristics do not seem to restrict the skeletal muscle adaptive response to resistance type exercise training in healthy older adults.

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ECSS Paris 2023: OP-PN05

Speaker B Massimiliano Ansaldo

Speaker B

Massimiliano Ansaldo
University of Pavia, Department of molecular medicine
Italy
"ECCENTRIC TRAINING INDUCES DIFFERENT MUSCLE MITOCHONDRIAL ADAPTATIONS IN OLD VERSUS YOUNG MEN"

INTRODUCTION: Skeletal muscle aging is not only characterized by loss of muscle mass and power but also by mitochondrial impairments and reduced oxidative function (1). Resistance training (RT) is considered among the most effective strategies to counteract muscle atrophy and preserve muscle function (2). Moderate-intensity exercise based on eccentric (ECC) contractions has been proposed as an alternative to the classic conventional RT due to its potential efficacy in increasing muscle mass and function without requiring excessive effort for the elderly population (3,4). Notably, recent evidence showed significant improvement in mitochondrial function following chronic RT (5). However, the impact of eccentric-resistance training (ECC-RT) on mitochondrial adaptations is still not known. Thus, we investigated mitochondrial adaptations in response to 8 weeks of moderate ECC-RT in old (O) vs young (Y) individuals. METHODS: Eight O (67±1.3 y.o.) and eight Y (25±6 y.o.) subjects underwent 8 weeks of moderate-load ECC-RT consisting of 4 sets of 15 repetitions performed at 60% of ECC 1RM, 3 times/week. Before the first (PRE) and after the last (POST) training session, knee-extensors maximal voluntary isometric contraction (MVIC) torque was assessed at 3 different joint angles 60°, 70°, 80° and maximum isometric torque value obtained over the three joint angles was chosen as MVIC peak value. Muscle volume (QV) was measured by MRI. Muscle biopsies were also collected from the Vastus Lateralis and markers of mitochondrial biogenesis, content, and dynamics were analyzed by western blot. Data were analyzed by two-way ANOVA. RESULTS: After 8 weeks of eccentric resistance training, MVIC force increased in both O and Y (17 vs. 13%, respectively p<0.05 for both groups). QV increased in both O and Y (4% vs. 5%) (p<0.001) (p<0.01). After training, PGC-1α decreased in O (-44%, p<0.05) while no changes were observed in Y (p>0.05). TOM20 and CS decreased in O (-29% and -31% respectively, p<0.01) but they remained unaffected in Y (p>0.05). MNF1 increased in Y (+65%, p<0.05), while did not change in O (p>0.05). Regarding mitochondrial fission, levels p637DRP1 decreased in O (-41%, p<0.05) and not in Y (P>0.05); p616DRP1 increased in Y (+300%, p<0.05) and not in O (P>0.05). CONCLUSION: Despite the positive effect on muscle mass and strength in both O and Y, ECC-RT dampened mitochondrial biogenesis, reduced mitochondrial content, and promoted fission in O while both fission and fusion increased in Y. We can hypothesize an age-dependent response to moderate ECC-RT, with a negative effect on mitochondrial adaptations in O compared to Y. This is of particular interest, as such exercise modality, which could be tailored for elderly populations for its positive neuromuscular adaptations could not be entirely suitable for counteracting reductions in oxidative function. (1) Tieland & Trouwborst & Clark 2017 (2) Hoppeler, 2016 (3) Quinlan et al, 2021 (4) Franchi & Reeves & Narici, 2017 (5) Mesquita et al, 2020

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ECSS Paris 2023: OP-PN05

Speaker C Michiel Ewalts

Speaker C

Michiel Ewalts
Bangor University, UK, Institute for Applied Human Physiology
Netherlands
"Effect of pulmonary mechanoreceptors on sympathetic outflow during mild intensity exercise in healthy humans"

INTRODUCTION: During exercise, increased sympathetic vasomotor outflow optimizes blood flow to exercising muscles and maintains blood pressure. Several mechanisms activate vasomotor outflow during exercise, including central command, muscle afferent feedback, and the arterial baroreceptor reflex. We have shown that a sustained increase in pulmonary arterial pressure, like that displayed during exercise, elicits sympathetic activation in experimental animals and humans exposed to high altitude hypoxia. The aim of this study was to investigate an additional mechanism of exercise induced sympathetic activation, which potentially arises from mechanoreceptors located in the pulmonary arterial system. METHODS: To address our aim, 12 healthy individuals (F=2; 28±7 years old) were studied under hypoxic conditions, a setting designed to elevate pulmonary arterial systolic pressure (PASP) above normal. The experiment comprised of three conditions: i) rest in acute hypoxia (FiO2=12.5%; baseline); ii) mild intensity exercise (RPE 11-12) in acute hypoxia (EX) and iii) mild intensity exercise in acute hypoxia combined with inhalation of vasodilator nitric oxide (iNO, 40 ppm) to selectively reduce PASP (EX reduced PASP). Muscle sympathetic nerve activity (MSNA; microneurography), ventilation (VE; breath-by-breath online gas collection system), blood pressure (BP; photoplethysmography) and heart rate (HR) were measured continuously, and ratings of perceived exertion was assessed in the final minute of exercise. PASP was measured using Doppler echocardiography. Vascular-sympathetic baroreflex gain was determined using spontaneous baroreflex sensitivity. To detect differences between conditions, a one-way repeated measures ANOVA was performed, followed by Bonferroni corrected T-tests. A statistical level of p<0.05 was accepted. All data are expressed as mean±SD. RESULTS: PASP increased during exercise (baseline 28±7 vs. EX 42±9 mmHg; P<0.001) and was lower in EX reduced PASP vs EX (42±9 vs. 36±8 mmHg; P=0.018). MSNA burst frequency increased by 61% during exercise (baseline 21±7 vs. EX 34±9 burst/min; P=0.001), which was partially reversed (12%) by reducing PASP with iNO during exercise (EX 34±9 vs. EX reduced PASP 30±9 burst/min; P=0.027). Reducing PASP during exercise also reduced MSNA operating point (burst incidence; 28±9 vs. 25±8 bursts/100Hb; P=0.030), without changing diastolic operating pressure (79±16 vs. 78±12 mmHg; P=0.307), or spontaneous vascular-sympathetic baroreflex gain (P=0.726). Reducing PASP during exercise had no effect on HR (P=0.999), VE (p=0.159), workload (P=0.701) or RPE (P=0.667). CONCLUSION: Lowering PASP reduced sympathetic outflow and reset vascular sympathetic baroreflex control of MSNA downward during hypoxic exercise. Our findings indicate that, in addition to established neural mechanisms, an input from pulmonary arterial mechanoreceptors contributes to sympathetic activation and arterial baroreceptor reflex resetting during exercise.

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ECSS Paris 2023: OP-PN05