Bruno Grassi

Bruno Grassi
University of Udine | UNIUD · Department of Medicine

MD, PhD

About

172
Publications
24,723
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
7,485
Citations
Citations since 2017
4 Research Items
2183 Citations
20172018201920202021202220230100200300400
20172018201920202021202220230100200300400
20172018201920202021202220230100200300400
20172018201920202021202220230100200300400
Introduction
Skills and Expertise

Publications

Publications (172)
Article
Key points: Superposition of hypoxia on 21 day bed rest did not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone. A significant impairment of maximal oxidative performance was identified downstream of cardiovascular O2 delivery, involving both the intramuscular matching between O2 supply and utilization and mit...
Article
Background & aims: Aging and experimental bed rest are associated with muscle atrophy and resistance to post-prandial stimulation of protein synthesis or anabolic resistance (AR). We have used in young and older adult volunteers, during short-term bed rest, a quick and non-invasive method, based on a single oral bolus of the stable isotope L[ring-...
Article
Cardiac function, skeletal (soleus) muscle oxidative metabolism and the effects of exercise training were evaluated in a transgenic murine model (Tgαq*44) of chronic heart failure (CHF) during the critical period between the occurrence of an impairment of cardiac function and the stage at which overt cardiac failure ensues (i.e. from 10 to 12 month...
Article
The objective of this study was to characterize static and dynamic thoraco-abdominal volumes in obese adolescents and to test the effects of a 3-week multidisciplinary body weight reduction program (MBWRP), entailing an energy-restricted diet, psychological and nutritional counseling, aerobic physical activity, and respiratory muscle endurance trai...
Article
Full-text available
This investigation aimed to compare the response of older adult and young men to bed-rest and subsequent rehabilitation. Sixteen older (OM: 55-65 years) and seven young men (YM: 18-30 years) were exposed to 14-day bed rest (BR) followed by 14-day rehabilitation (R). Quadriceps muscle volume (QVOL), force (QF) and explosive power (QP) of leg extenso...
Article
Full-text available
Purpose We investigated the effects of moderate-intensity training at low and high altitude on V˙O2 and Q˙aO2 kinetics and on myosin heavy-chain expression (MyHC) in seven women (36.3 yy ± 7.1; 65.8 kg ± 11.7; 165 cm ± 8) who participated in two 12- to 14-day trekking expeditions at low (598 m) and high altitude (4132 m) separated by 4 months of re...
Article
During high-intensity submaximal exercise muscle fatigue and decreased efficiency are closely intertwined, and each contributes to exercise intolerance. Fatigue and muscle inefficiency share common mechanisms, e.g. decreased "metabolic stability", muscle metabolite accumulation, decreased free energy of ATP breakdown, limited O2 or substrate availa...
Article
Bilateral deficit (BLD) occurs when the force (or power) generated by both limbs together is smaller than the sum of the forces (or powers) developed separately by the two limbs. The amount of BLD can be altered by neural adaptations brought about by the repetitive execution of specific motor tasks (training). Prolonged disuse also leads to relevan...
Article
Key points: Skeletal muscle atrophy occurs as a result of disuse. Although several studies have established that a decrease in protein synthesis and increase in protein degradation lead to muscle atrophy, little is known about the triggers underlying such processes. A growing body of evidence challenges oxidative stress as a trigger of disuse atro...
Article
Full-text available
Purpose: Microgravity leads to a decline of muscle power especially in the postural muscles of the lower limb. Muscle atrophy primarily contributes to this negative adaptation. Nutritional countermeasures during unloading were shown to possibly mitigate the loss of muscle mass and strength. The aim of this study was to investigate the effects of d...
Article
Full-text available
Purpose: In obesity, an increased work of breathing contributes to a higher O2 cost of exercise and negatively affects exercise tolerance. The purpose of the study was to determine whether, in obese adolescents, acute respiratory muscle unloading via normoxic helium-O2 breathing reduces the O2 cost of cycling and perceived exertion. Methods: Nin...
Article
The effect of prolonged endurance training on the pulmonary V'O2 on- and off-kinetics in humans, in relation to muscle mitochondria biogenesis, is investigated. Eleven untrained physically active men (mean ± SD: age 22.4 ± 1.5 years, V'O2peak 3187 ± 479 ml∙min(-1)) performed endurance cycling training (4 sessions per week) lasting 20 weeks. Trainin...
Article
Full-text available
Patients with McArdle's disease (McA) typically show the "second wind" phenomenon, a sudden decrease in heart rate (HR) and an improved exercise tolerance occurring after a few minutes of exercise. In the present study we investigated whether in McA a first bout of exercise determines a second wind during a second bout, separated by the first by a...
Article
Full-text available
Purpose: to investigate: 1) the role of V'O2max, fraction of it (F) and metabolic cost of transport (CoT) in determining performance during an ultra-endurance competition and 2) the effects of the race on several biomechanical and morphological parameters of the lower limbs that are likely to affect CoT. Methods: Eleven runners (age: 29-54 years) p...
Article
At the onset of muscular exercise, the kinetics of pulmonary oxygen uptake (VO2P) reflect the integrated dynamic responses of the ventilatory, circulatory and neuromuscular systems for oxygen transport and utilization. Muscle VO2 (VO2m) kinetics, however, are dissociated from VO2P kinetics by intervening O2 capacitances and the dynamics of the circ...
Article
Full-text available
With current techniques, experimental measurements alone cannot characterize the effects of oxygen blood-tissue diffusion on muscle oxygen uptake (VO2) kinetics in contracting skeletal muscle. To complement experimental studies, a computational model is used to quantitatively distinguish the contributions of convective oxygen delivery, diffusion in...
Article
Full-text available
We hypothesized, in a group of obese women (OB), a more significant impairment of aerobic metabolism during knee extension (KE) exercise vs. that described during cycle ergometer exercise, lending support to the role of skeletal muscles in limiting exercise tolerance in OB. Eleven OB (age 29.5 ± 5.5 years, body mass index 43.2 ± 5.4 kg m(-2)) and 1...
Article
Full-text available
Oxidative function during exercise was evaluated in 11 young athletes with marked skeletal muscle hypertrophy induced by long-term resistance training (RTA, body mass 102.6±7.3 kg, mean±SD) and 11 controls (CTRL, body mass 77.8±6.0). Pulmonary O2 uptake (V'O2) and vastus lateralis muscle fractional O2 extraction (by near-infrared spectroscopy) were...
Article
Full-text available
Enzyme replacement therapy (ERT) has recently became available for patients with glycogen storage disease type II. Previous studies have demonstrated clinical efficacy of enzyme replacement therapy, however, data on physiological variables related to exercise tolerance are scarce. Four glycogen storage disease type II late-onset patients (45 ± 6 ye...
Article
The effects of 5 weeks moderate-intensity endurance training on pulmonary oxygen uptake kinetics (VO2 on-kinetics) were studied in fifteen healthy males (means ± S.D.: age 22.7 ± 1.8 years, body weight 76.4 ± 8.9 kg, VO2max 46.0 ± 3.7 ml kg-1 min-1). Training caused a significant acceleration (P = 0.003) of VO2 on-kinetics during moderate-intensity...
Article
Based on experimental studies, the relationship between intracellular O(2) (iPO(2)) and work rate (WR) in skeletal muscle is not unique. One study found that iPO(2) reached a plateau at 60% maximal WR, while another found that iPO(2) decreased linearly at higher WR, inferring capillary permeability-surface area (PS) and blood-tissue oxygen gradient...
Article
Full-text available
A recent study has demonstrated that neuromuscular electrical stimulation (NMES) determines, in vitro, a fast-to-slow shift in the metabolic profile of muscle fibers. The aim of the present study was to evaluate if, in the same subjects, these changes would translate, in vivo, into an enhanced skeletal muscle oxidative metabolism. Seven young men w...
Article
Background: Pulmonary VO2 on-kinetics during light-to-moderate-intensity constant-work-rate exercise, an experimental model mirroring energetic transitions during daily activities, has been shown to speed up with aerobic exercise training (AET) in normal subjects, but scant data are available in chronic heart failure (CHF). Methods and results:...
Article
The effect of maximal voluntary isometric strength training of knee extensor muscles on pulmonary V'O(2) on-kinetics, the O(2) cost of cycling and peak oxygen uptake (V'O(2peak)) in humans was studied. Seven healthy males (mean ± SD, age 22.3 ± 2.0 years, body weight 75.0 ± 9.2 kg, V'O(2peak) 49.5 ± 3.8 ml kg(-1) min(-1)) performed maximal isometri...
Article
Full-text available
We would like to thank Dr Kemp for the keen insight provided by his detailed analysis (Kemp, 2011, preceding Letter in this issue of The Journal of Physiology) of the results from our recently published experiment (Wust et al. 2011). These data and analyses suggest an apparent cooperativity in the control of mitochondrial respiration () in vivo tha...
Article
Enzyme replacement therapy (ERT) has recently became available for Pompe disease. Data on the effects of ERT on physiological variables related to exercise tolerance have never been published. Pulmonary gas exchange, cardiac output (by impedance cardiography), and vastus lateralis muscle O₂ extraction (by near-infrared spectroscopy) were determined...
Article
Full-text available
A functional evaluation of skeletal muscle oxidative metabolism during dynamic knee extension (KE) incremental exercises was carried out following a 35-day bed rest (BR) (Valdoltra 2008 BR campaign). Nine young male volunteers (age: 23.5 ± 2.2 yr; mean ± SD) were evaluated. Pulmonary gas exchange, heart rate and cardiac output (by impedance cardiog...
Article
Full-text available
Our objective was to correlate skeletal muscle mass (SM) with cardiopulmonary exercise testing (CPET) descriptors of exercise capacity in patients with amyotrophic lateral sclerosis (ALS) and compare ALS CPET data with those of patients with mitochondrial myopathy (MM) and normal subjects (N). Twenty-four early-stage ALS patients (63±11 years) unde...
Article
Full-text available
Fast kinetics of muscle oxygen consumption () is characteristic of effective physiological systems integration. The mechanism of kinetic control in vivo is equivocal as measurements are complicated by the twin difficulties of making high-frequency direct measurements of and intramuscular metabolites, and in attaining high [ADP]; complexities that c...
Article
Full-text available
The V·O₂ slow component, a slowly developing increase in V·O₂ during constant-work-rate exercise performed above the lactate threshold, represents a progressive loss of skeletal muscle contractile efficiency and is associated with the fatigue process. This brief review outlines the current state of knowledge concerning the mechanistic bases of the...
Article
Full-text available
An analysis of previously published data obtained by our group on patients characterized by markedly slower pulmonary VO₂ kinetics (heart transplant recipients, patients with mitochondrial myopathies, patients with McArdle disease) was carried out in order to suggest that slow VO₂ kinetics should not be considered the direct cause, but rather a mar...
Article
Full-text available
A functional evaluation of skeletal muscle oxidative metabolism was performed in a group of obese adolescents (OB). The various components of pulmonary O(2) uptake (Vo(2)) kinetics were evaluated during 10-min constant-load exercises (CLE) on a cycloergometer at different percentages of Vo(2max). The relationships of these components with the gas e...
Article
Creatine kinase (CK) plays a key role both in energy provision and in signal transduction for the increase in skeletal muscle O2 uptake () at exercise onset. The effects of acute CK inhibition by iodoacetamide (IA; 5 mm) on kinetics were studied in isolated canine gastrocnemius muscles in situ (n = 6) during transitions from rest to 3 min of electr...
Article
Full-text available
Data are lacking regarding age-related modifications of phase I (PhI) of pulmonary Vo(2) on-kinetics during moderate-intensity exercise. We studied three groups (aged 20-30, 40-50, and 60-70 years) of 10 normal subjects, who underwent one incremental and four below-gas exchange threshold constant-power cardiopulmonary exercise tests. Data from cons...
Article
Full-text available
"Central" and "peripheral" limitations to oxidative metabolism during exercise were evaluated in 10 young males following a 35-day horizontal bed rest (BR). Incremental exercise (IE) and moderate- and heavy-intensity constant-load exercises (CLE) were carried out on a cycloergometer before and 1-2 days after BR. Pulmonary gas exchange, cardiac outp...
Article
The aim was to identify additional noninvasive tools allowing to detect and to quantify the metabolic impairment in patients with mitochondrial myopathies (MM) or McArdle's disease (McA). Kinetics of adjustment of pulmonary oxygen uptake (VO2 kinetics) during transitions to constant-load moderate-intensity cycle ergometer exercise were determined o...
Article
Full-text available
The energy cost of running (Cr) is classically determined from steady-state oxygen consumption (Vo2) at constant speed, divided by running speed. In the present study, Cr was determined during incremental treadmill tests in the course of the assessment of Vo(2max) and related parameters as follows. Assume that the running speed is increased by a co...
Article
Electrical myostimulation (EMS) has recently been proposed as an interesting rehabilitation tool in patients with chronic heart failure (CHF). Although its beneficial effects on exercise capacity and muscle strength have been demonstrated, the neuromuscular adaptations responsible for improved performance are not well understood. This preliminary c...
Article
Full-text available
The "slow component" of O2 uptake (VO2) kinetics during constant-load heavy-intensity exercise is traditionally thought to derive from a progressive recruitment of muscle fibers. In this study, which represents a reanalysis of data taken from a previous study by our group (Grassi B, Hogan MC, Greenhaff PL, Hamann JJ, Kelley KM, Aschenbach WG, Const...
Article
Previous studies have shown that increased oxygen delivery, via increased convection or arterial oxygen content, does not speed the dynamics of oxygen uptake, Vo(2m), in dog muscle electrically stimulated at a submaximal metabolic rate. However, the dynamics of transport and metabolic processes that occur within working muscle in situ is typically...
Article
Exercise training is known to improve exercise tolerance in elderly subjects. Therefore the present study aimed at investigating the effects of one year of combined endurance and resistance training in healthy older people. After baseline evaluation, subjects were assigned to either the training group (n=24, age 77.2+/-3.6) or the control group (n=...
Article
During exercises with relatively small muscle masses, limitations to exercise performance by the cardiovascular system should be significantly reduced, allowing one to fully-test the “oxidative potential” of the investigated muscles. Ten elderly males (E, 77.8 ± 2.9 years [ \( \overline{x} \pm {\text{SD}} \)]) and eight young controls (Y, 26.6 ± 3....
Article
Patients with mitochondrial myopathies (MM) or myophosphorylase deficiency (McArdle's disease, McA) show impaired capacity for O(2) extraction, low maximal aerobic power, and reduced exercise tolerance. Non-invasive tools are needed to quantify the metabolic impairment. Six patients with MM, 6 with McA, 25 with symptoms of metabolic myopathy but ne...
Article
VO(2) kinetics and O(2) deficit are important determinants of exercise tolerance. In "normal" conditions convective and diffusive O(2) delivery to skeletal muscle fibers do not represent important determinants of VO(2) kinetics, whose limiting factors seem mainly located within muscle fibers. Whereas a limiting role by PDH has not been confirmed, t...
Article
Full-text available
It is well known that the oxygen uptake kinetics during rest-to-work transition (V(O2) on-kinetics) in trained subjects is significantly faster than in untrained individuals. It was recently postulated that the main system variable that determines the transition time (t(1/2)) of the V(O2) on-kinetics in skeletal muscle, at a given moderate ATP usag...
Article
Full-text available
The condition of persistently high plasma CK levels is frequently encountered in asymptomatic patients with normal neurological examination. This condition may be the unique manifestation of several neuromuscular disorders, whose diagnosis is now possible using new diagnostic techniques. However, even if these patients are intensely investigated, s...
Article
The main aim of the present study was to investigate skeletal muscle oxidative metabolism in heart transplant recipients (HTR) by noninvasive tools. Twenty male HTR (age 50.4 +/- 2.6 yr; mean +/- SE) and 17 healthy untrained age-matched controls (CTRL) performed an incremental exercise (IE) and a series of constant-load (CLE) moderate-intensity exe...
Article
The aim of the present study was to assess age-dependent changes of proteins in the vastus lateralis muscle of physically active elderly and young subjects by a combination of two-dimensional difference gel electrophoresis, SDS-PAGE and ESI-MS/MS. The differences observed in the elderly group included down-regulation of regulatory myosin light chai...
Article
Ageing is associated with an increased susceptibility to muscle damage but little is known on how this affects muscle recovery after exercise. Hence, this study is aiming at investigating the effects of a heavy-resistance training session of neuromuscular recovery of the calf muscles of a group of elderly men aged >65. Maximal isometric and isokine...
Article
The rate at which skeletal muscle oxidative phosphorylation adjusts to a new metabolic requirement ("VO2 kinetics") is one of the determinants of exercise tolerance. The VO2 kinetics does not seem to depend, in normal conditions, on O2 availability, at least for moderate-intensity exercise. A relatively minor limiting factor for the VO2 kinetics co...
Article
In isolated single skeletal myocytes undergoing long-term fatiguing contractions, caffeine (CAF) can result in nearly immediate restoration of generated tension to near-prefatigue levels by increasing Ca2+ release via activation of sarcoplasmic reticulum release channels. This study tested whether arterial CAF infusion (>5 mm) would cause a similar...
Article
Nitric oxide (NO) has an inhibitory action on O2 uptake (VO2) at the level of the mitochondrial respiratory chain. The aim of this study was to evaluate the effects of NO synthase (NOS) inhibition on muscle (VO2) kinetics. Isolated canine gastrocnemius muscles in situ (n = 6) were studied during transitions from rest to 4-min of electrically stimul...
Article
In "normal" conditions (e.g., normoxia, absence of pathological conditions) convective and diffusive O(2) delivery to skeletal muscle fibers do not seem to represent important determinants for the kinetics of adjustment of oxidative phosphorylation following increases in metabolic demand. Whereas a limiting role by PDH has not been experimentally c...
Article
Physical training is recommended as an efficient therapy in patients with chronic heart failure (CHF). Low-frequency electrical myostimulation (EMS) has recently been suggested as a good alternative to conventional aerobic training. The aim of this study was to compare the effects of EMS and conventional exercise training in patients with moderate...
Article
Tibetan highlanders develop at altitude peak aerobic power levels close to those of Caucasians at sea level. In order to establish whether this feature is genetic and, as a consequence, retained by Tibetan lowlanders, altitude-induced changes of peak aerobic performance were assessed in four groups of volunteers with different ethnic, altitude expo...
Article
Full-text available
Serial evaluation of aerobic metabolism and exercise tolerance early after heart transplantation (HT). Fifteen heart transplant recipients (HTR), aged 52.0 +/- 9.9 yr (mean +/- SD), not undergoing structured rehabilitation programs, were tested two to four times during the first 2 yr post-HT. As a reference, a group of 11 healthy untrained controls...
Article
Full-text available
BORRELLI, E., S. POGLIAGHI, A. MOLINELLO, F. DICIOLLA, M. MACCHERINI, and B. GRASSI. Serial Assessment of Peak V̇O2 and V̇O2 Kinetics Early after Heart Transplantation. Med. Sci. Sports Exerc., Vol. 35, No. 11, pp. 1798-1804, 2003. Purpose: Serial evaluation of aerobic metabolism and exercise tolerance early after heart transplantation (HT). Method...
Article
The various mechanisms responsible for ATP resynthesis include phosphocreatine (PCr) hydrolysis, anaerobic glycolysis and oxidative phosphorylation. Among these, the latter represents the most important mechanism of energy provision. However, oxidative phosphorylation is characterized by a lower maximal power and a slow attainment of a steady state...
Article
Full-text available
The purpose of this study was to test the hypothesis that increasing muscle contraction frequency, which alters the duty cycle and metabolic rate, would increase the contribution of the contractile phase to mean venous blood flow in isolated skeletal muscle during rhythmic contractions. Canine gastrocnemius muscle (n = 5) was isolated, and 3-min st...