Ioannis S Vrabas | Aristotle University of Thessaloniki (original) (raw)

Papers by Ioannis S Vrabas

British Journal of Sports Medicine, Feb 23, 2005

To compare the effects of proprioceptive neuromuscular facilitation (PNF) and isokinetic training... more To compare the effects of proprioceptive neuromuscular facilitation (PNF) and isokinetic training on fibre type distribution and cross sectional area of the vastus lateralis muscle. Methods: Twenty four male university students were divided into two equal groups: PNF training and isokinetic training (ISO). The training regimen for the PNF group consisted of three sets of 30 repetitions against maximal resistance, alternating two patterns of sequential movements of the right lower extremity: (a) toe flexion and ankle plantar flexion and eversion; (b) knee extension and hip extension, abduction, and internal rotation. The ISO group performed three sets of 30 repetitions alternating knee extension and flexion of the right leg at angular velocities of 180 and 90˚/s in an isokinetic dynamometer (Cybex). Both groups trained three times a week for a total of eight weeks. Muscle biopsy specimens were obtained from the right vastus lateralis muscle before and after training. Results: The mean percentage area of type IIB fibre was significantly decreased (p,0.01) after eight weeks of PNF training, whereas that of type IIA fibre was significantly (p,0.05) increased. The mean percentage area of ISO trained type IIAB fibres exhibited an augmentative pattern (p,0.01) with a parallel reduction (p,0.05) in type IIA. Percentage fibre type distribution exhibited a similar pattern. Conclusions: Both PNF and ISO training alter fibre type distribution and mean cross sectional area. These changes occur in the type II fibre subgroup.

The Internet journal of microbiology, Jan 27, 2014

Background: Muscle strength is a key factor to the performance in all sports. Thus, it is importa... more Background: Muscle strength is a key factor to the performance in all sports. Thus, it is important to correctly implement training programmes to improve it. Eccentric training programmes increase muscle strength and causes hypertrophy. However, the effectiveness of eccentric exercise in changing the architectural structure of muscles, using multi-joint isokinetic dynamometer at high intensity, has not been studied. The purpose of this study was to investigate the effects of eccentric isokinetic training of high loads on the architectural structure of amateur soccer players' rectus femoris, utilizing a multi-joint dynamometer. Methods: Sixteen subjects (18-26 years) without musculoskeletal problems took part in this study. Eight of them were amateur soccer players and 8 non-trained individuals. The equipment utilized was the following: a) a multi-joint isokinetic dynamometer (MID-Hydrodynamic AF), b) a force plate (Kistler, 9281-CA), a computer and a video projector in order to provide feedback regarding the characteristics of the power-time curve during training and c) an ultrasound device used to record the architectural structure of the RF (General Electric, model: LOGIQ 400). Results: The experimental group demonstrated statistically significant differences regarding all the tested variables: Xapon, t(7)=-4,288 p=,004, Lfiber, t(7)=-4,209 p=,004 and Φpterosi, t(7)=-3,418 p=, 011, while the control group did not. Conclusion: The multi-joint isokinetic dynamometer is a tool that leads to the maximization the eccentric strength.

European journal of nutrition, Feb 6, 2019

Purpose Older individuals suffer from low NADH levels. We have previously shown that nicotinamide... more Purpose Older individuals suffer from low NADH levels. We have previously shown that nicotinamide riboside [NR; a NAD(P)(H) precursor] administration impaired exercise performance in young rats. It has been suggested that supplementation of redox agents exerts ergogenic effect only in deficient individuals. We hypothesized that old individuals would more likely benefit from NR supplementation. We investigated the effect of acute NR supplementation on redox homeostasis and physical performance in young and old individuals. Methods Twelve young and twelve old men received NR or placebo in a double-blind cross-over design. Before and 2 h after NR or placebo supplementation, blood and urine samples were collected, while physical performance (VO 2max , muscle strength, and fatigue) was assessed after the second blood sample collection. Results At rest, old individuals exhibited lower erythrocyte NAD(P)H levels, higher urine F 2-isoprostanes and lower erythrocyte glutathione levels compared to young (P < 0.05). NR supplementation increased NADH (51% young; 59% old) and NADPH (32% young; 38% old) levels in both groups (P < 0.05), decreased F 2-isoprostanes by 18% (P < 0.05), and tended to increase glutathione (P = 0.078) only in the old. NR supplementation did not affect VO 2max and concentric peak torque, but improved isometric peak torque by 8% (P = 0.048) and the fatigue index by 15% (P = 0.012) in the old. In contrast, NR supplementation did not exert any redox or physiological effect in the young. Conclusions NR supplementation increased NAD(P)H levels, decreased oxidative stress, and improved physical performance only in old subjects, substantiating that redox supplementation may be beneficial only in individuals with antioxidant deficiencies.

Medicine and Science in Sports and Exercise, May 1, 1996

Clinical Orthopaedics and Related Research, Nov 6, 2019

Background Alpha-tocopherol, a well-known antioxidative agent, may have a positive effect on bone... more Background Alpha-tocopherol, a well-known antioxidative agent, may have a positive effect on bone formation during the remodeling phase of secondary fracture healing. Fracture healing and osseointegration of implants share common biological pathways; hence, alpha-tocopherol may enhance implant osseointegration. Each author certifies that neither he, nor any member of his immediate family, has funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article. Each author certifies that his institution approved the animal protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research.

Biology

This study aimed to elucidate whether muscle blood flow restriction during maximal exercise is as... more This study aimed to elucidate whether muscle blood flow restriction during maximal exercise is associated with alterations in hemodynamics, cerebral oxygenation, cerebral activation, and deterioration of exercise performance in male participants. Thirteen healthy males, cyclists (age 33 ± 2 yrs., body mass: 78.6 ± 2.5 kg, and body mass index: 25.57 ± 0.91 kg·m−1), performed a maximal incremental exercise test on a bicycle ergometer in two experimental conditions: (a) with muscle blood flow restriction through the application of thigh cuffs inflated at 120 mmHg (with cuffs, WC) and (b) without restriction (no cuffs, NC). Exercise performance significantly deteriorated with muscle blood flow restriction, as evidenced by the reductions in V˙O2max (−17 ± 2%, p < 0.001), peak power output (−28 ± 2%, p < 0.001), and time to exhaustion (−28 ± 2%, p < 0.001). Muscle oxygenated hemoglobin (Δ[O2Hb]) during exercise declined more in the NC condition (p < 0.01); however, at exhausti...

Acta Physiologica

AimWe aimed to investigate the inter‐individual variability in redox and physiological responses ... more AimWe aimed to investigate the inter‐individual variability in redox and physiological responses of antioxidant‐deficient subjects after antioxidant supplementation.MethodsTwo hundred individuals were sorted by plasma vitamin C levels. A low vitamin C group (n = 22) and a control group (n = 22) were compared in terms of oxidative stress and performance. Subsequently, the low vitamin C group received for 30 days vitamin C (1 g) or placebo, in randomized, double‐blind, crossover fashion, and the effects were examined through a mixed‐effects model, while individual responses were calculated.ResultsThe low vitamin C group exhibited lower vitamin C (−25 μmol/L; 95%CI[−31.7, −18.3]; p < 0.001), higher F2‐isoprostanes (+17.1 pg/mL; 95%CI[6.5, 27.7]; p = 0.002), impaired VO2max (−8.2 mL/kg/min; 95%CI[−12.8, −3.6]; p < 0.001) and lower isometric peak torque (−41.5 Nm; 95%CI[−61.8, −21.2]; p < 0.001) compared to the control group. Regarding antioxidant supplementation, a significant ...

International Journal of Sports Physiology and Performance

Purpose: This study examined the underlying mechanisms of postactivation potentiation and the tim... more Purpose: This study examined the underlying mechanisms of postactivation potentiation and the time course of muscular- and neural-related variables. Methods: Fourteen trained males executed 4 sets of six 6-second maximum isometric conditioning plantar flexions, with 15 seconds and 2 minutes of interval between the contractions and sets, respectively. Peak twitch torque (TT), rate of torque development, time to peak torque, half relaxation time, and the neural-related variables of H-reflex and electromyogram, normalized to the maximum M-wave (H/M and RMS/M, respectively), were evaluated, as well as the level of the voluntary activation, assessed by the twitch interpolation technique. All neural-related variables were analyzed for the trial within each set when TT was maximal and for the trial within each set when the neural-related variable itself was maximal. Results: Compared with the baseline measures, TT and rate of torque development significantly increased in all sets (P < ....

International Journal of Sports Medicine, 2021

Differences in blood flow patterns and energy cost between isometric and dynamic resistance exerc... more Differences in blood flow patterns and energy cost between isometric and dynamic resistance exercise may result to variant cardiovascular, neural, and muscle metabolic responses. We aimed to compare the cardiovascular, baroreceptor sensitivity, and muscle oxygenation responses between workload-matched, large muscle-mass isometric and dynamic resistance exercises. Twenty-four young men performed an isometric and a dynamic double leg-press protocol (4 sets×2 min) with similar tension time index (workload). Beat-by-beat hemodynamics, baroreceptor sensitivity, muscle oxygenation, and blood lactate were assessed. The increase in blood pressure was greater (p<0.05) in the 1st set during dynamic than isometric exercise (by ~4.5 mmHg), not different in the 2nd and 3rd sets, and greater in the 4th set during isometric exercise (by ~5 mmHg). Dynamic resistance exercise evoked a greater increase in heart rate, stroke volume, cardiac output, and contractility index (p<0.05), and a greater...

The Journal of sports medicine and physical fitness, 2015

AIM The aim of the present investigation was to determine the greater rate of lactate removal aft... more AIM The aim of the present investigation was to determine the greater rate of lactate removal after a maximal rowing test using different intensities during active recovery. METHODS Thirty elite male rowers performed a simulated incremental exercise protocol on rowing ergometer to determine their maximal oxygen uptake and they divided into three equal sized group according to the type of the recovery that followed the assessment. The first group (N.=10) subjected to 20 min of passive recovery, while the second (N.=10) and the third (N.=10) groups performed 20 min of active recovery using the 25% and the 50% of each individual’s maximal power output, respectively. During the recovery period, every two min were performed measurements for the assessment of blood lactate, oxygen consumption and heart rate (HR). RESULTS It was found that after 10 min of active recovery at 50% and 25% of maximal power output lactate concentration reduced by 43% and 15%, respectively, while during passive ...

Applied Physiology, Nutrition, and Metabolism, 2021

This study tested the hypothesis that muscle blood flow restriction reduces muscle and cerebral o... more This study tested the hypothesis that muscle blood flow restriction reduces muscle and cerebral oxygenation at rest. In 26 healthy males, aged 33 ± 2 yrs, physiological variables were continuously recorded during a 10-min period in 2 experimental conditions: a) with muscle blood flow restriction through thigh cuffs application inflated at 120 mm Hg (With Cuffs, WC) and b) without restriction (No Cuffs, NC). Muscle and cerebral oxygenation were reduced by muscle blood flow restriction as suggested by the increase in both muscle and cerebral deoxygenated hemoglobin (Δ[HHb]; p < 0.01) and the decrease of muscle and cerebral oxygenation index (Δ[HbDiff]; p < 0.01). Hemodynamic responses were not affected by such muscle blood flow restriction, whereas baroreflex sensitivity was reduced (p = 0.009). The perception of leg discomfort was higher (p < 0.001) in the WC than in the NC condition. This study suggests that thigh cuffs application inflated at 120 mm Hg is an effective meth...

IUBMB Life, 2021

A signal in biology is any kind of coded message sent from one place in an organism to another pl... more A signal in biology is any kind of coded message sent from one place in an organism to another place. Biology is rich in claims that reactive oxygen and nitrogen species transmit signals. Therefore, we define a “redox signal as an increase/decrease in the level of reactive species”. First, as in most biology disciplines, to analyze a redox signal you need first to deconstruct it. The essential components that constitute a redox signal and should be characterized are: (i) the reactivity of the specific reactive species, (ii) the magnitude of change, (iii) the temporal pattern of change, and (iv) the antioxidant condition. Second, to be able to translate the physiological fate of a redox signal you need to apply novel and bioplausible methodological strategies. Important considerations that should be taken into account when designing an experiment is to (i) assure that redox and physiological measurements are at the same or similar level of biological organization and (ii) focus on molecules that are at the highest level of the redox hierarchy. Third, to reconstruct the redox signal and make sense of the chaotic nature of redox processes, it is essential to apply mathematical and computational modeling. The aim of the present study was to collectively present, for the first time, those elements that essentially affect the redox signal as well as to emphasize that the deconstructing, decoding and reconstructing of a redox signal should be acknowledged as central to design better studies and to advance our understanding on its physiological effects.

The Journal of Physiological Sciences, 2020

The present study aimed to investigate whether endurance exercise-induced changes in blood plasma... more The present study aimed to investigate whether endurance exercise-induced changes in blood plasma composition may lead to adaptations in erythrocytes, skeletal muscle and liver. Forty sedentary rats were randomly distributed into two groups: a group that was injected with pooled plasma from rats that swam until exhaustion and a group that was injected with the pooled plasma from resting rats (intravenous administration at a dose of 2 mL/kg body weight for 21 days). Total antioxidant capacity, malondialdehyde and protein carbonyls were higher in the plasma collected from the exercised rats compared to the plasma from the resting rats. Νo significant difference was found in blood and tissue redox biomarkers and in tissue metabolic markers between rats that received the “exercised” or the “non-exercised” plasma (P > 0.05). Our results demonstrate that plasma injections from exercised rats to sedentary rats do not induce redox or metabolic adaptations in erythrocytes, skeletal muscle...

Digestive Surgery, 2019

Background: One of the most challenging operations is the resection of the pancreas, which is ass... more Background: One of the most challenging operations is the resection of the pancreas, which is associated with high morbidity. Metabolic control during the perioperative period remains an issue that is sometimes difficult to manage. Objectives: Exercise has a positive effect on glycaemic control. The objective of this trial was determining whether exercise has any benefit for oxidative stress and glucose levels. Method: The study was an open-label, randomised clinical trial. It has been registered in the International Standard Randomised Controlled Trial registry. The patients were selected according to the Consolidated Standard of Reporting Trials criteria. Results: In total, 56 patients were assessed for eligibility. There was no statistical difference between the 2 groups (the exercise and the control one) regarding the disease characteristics, morbidity or influence of exercise on oxidative stress; however, the control of glucose was superior in the exercise group. Conclusions: E...

Journal of Clinical Medicine Research, 2019

Background: Pancreatic resection is still a challenging operation characterised by high morbidity... more Background: Pancreatic resection is still a challenging operation characterised by high morbidity. The quality of life in patients after pancreatectomy is a critical outcome. The aim of our trial is to prove whether or not exercise has any benefit to the life of these patients. Methods: The study was an open-label, randomized clinical trial. The patients were selected according to the Consolidated Standard of Reporting Trials criteria.

Journal of Human Sport and Exercise, 2017

The purpose of this study was to assess the kinematic characteristics of the gait of preschoolers... more The purpose of this study was to assess the kinematic characteristics of the gait of preschoolers before and after the implementation of an intervention training program. A group of twenty preschoolers without motor disorders participating in the study were assigned to two groups: the experimental group-10 preschoolers (mean age 4.9±0.2 years)-and the control group-10 preschoolers (mean age 4.8±0.3 years). Participants were assessed using the same test before and after the implementation of the intervention training program: they had to walk in a straight line three times along a distance of 5 meters (m). Kinematic variables were analysed based on 3D video processing using APAS software. Repeated Measures ANOVA was used to examine the effectiveness of the intervention training program (p<0.05). Results indicated that there were statistically significant differences in the Displacement of the Center of Mass during the Right Foot Support phase. There is a need for intervention training programs to enhance motor skill levels and the quality of movement in all children.

American Journal of Sports Science, 2014

The sprint performance on natural and artificial grass of 5 th generation was assessed. Sixty eig... more The sprint performance on natural and artificial grass of 5 th generation was assessed. Sixty eight young male soccer players, which were divided in two groups according to their age [children (n=36; 12.1±0.5y) and adolescents (n=32; 14.2±0.4y)], performed 30-m sprint tests with and without handling the ball on natural and artificial grass. The performance was recorded during 0-10m, 10-30m, and 0-30m running distances. It was found that children were significantly faster during 0-10m running distance on the artificial compared to natural grass when handling the ball while adolescents revealed no differences in sprint performance between the surfaces irrespectively of the ball condition. In running distances 10-30m and 0-30m, children were significant faster in the artificial compared to the natural grass either with or without ball, while the adolescents were significantly faster in the artificial grass only without handling the ball. Children run faster on artificial than natural grass while adolescent soccer players are faster in artificial grass when they do not have to handle the ball. It is clear that children should be more careful when play soccer on artificial grass because the ball is moving faster and greater skill is needed in order to avoid injuries.

Exercise has been consistently used as an oxidant stimulus in redox biology studies. However, pre... more Exercise has been consistently used as an oxidant stimulus in redox biology studies. However, previous studies have focused on group differences and did not examine individual differences. As a result, it remains untested whether all individuals experience oxidative stress after acute exercise. Therefore, the main aim of the present study was to investigate whether some individuals exhibit unexpected responses after an acute eccentric (i.e., muscle-damaging) exercise session. Ninety eight (N = 98) young men performed an isokinetic eccentric exercise bout with the knee extensors. Plasma, erythrocytes and urine samples were collected immediately before and 2 days post-exercise. Three commonly used redox biomarkers (F 2-isoprostanes, protein carbonyls and glutathione) were assayed. As expected, the two oxidant biomarkers (F 2-isoprostanes and protein carbonyls) significantly increased 2 days after exercise (46% and 61%, respectively); whereas a significant decrease in glutathione levels (by −21%) was observed after exercise. A considerable number of the participants exhibited changes in the levels of biomarkers in the opposite, unexpected direction than the group average. More specifically, 13% of the participants exhibited a decrease in F 2-isoprostanes and protein carbonyls and 10% of the participants exhibited an increase in glutathione levels. Furthermore, more than 1 out of 3 individuals exhibited either unexpected or negligible (from 0% to ± 5%) responses to exercise in at least one redox biomarker. It was also observed that the initial values of redox biomarkers are important predictors of the responses to exercise. In conclusion, although exercise induces oxidative stress in the majority of individuals, it can induce reductive stress or negligible stress in a considerable number of people. The data presented herein emphasize that the mean response to a redox stimulus can be very misleading. We believe that the wide variability (including the cases of reductive stress) described is not limited to the oxidant stimulus used and the biomarkers selected.