Kinetic Studies and Mechanism of Hydrogen Peroxide Catalytic Decomposition by Cu(II) Complexes with Polyelectrolytes Derived from L-Alanine and Glycylglycine

The catalytic decomposition of hydrogen peroxide by Cu(II) complexes with polymers bearing L-alanine (PAla) and glycylglycine (PGlygly) in their side chain was studied in alkaline aqueous media. The reactions were of pseudo-first order with respect to [H2O2] and [L-Cu(II)] (L stands for PAla or PGlygly) and the reaction rate was increased with pH increase. The energies of activation for the reactions were determined at pH 8.8, in a temperature range of 293–308 K. A suitable mechanism is proposed to account for the kinetic data, which involves the Cu(II)/Cu(I) redox pair, as has been demonstrated by ESR spectroscopy. The trend in catalytic efficiency is in the order PGlygly>PAla, due to differences in modes of complexation and in the conformation of the macromolecular ligands

The acute effects of different high-intensity conditioning activities on sprint performance differ between sprinters of different strength and power characteristics

The purpose of the present study was to examine the effect of different conditioning activities (CAs) on short-term increase in sprint performance. In twelve male sprinters (21.1±2.6 years, 100 m performance: 11.5±0.6 s) their body composition, half squat maximum strength, 100 m sprinting and countermovement jump performances were evaluated. The performance of a 50 m sprint (splits at 10 m, 30 m and 50 m) was evaluated before and 5, 10 and 15 min after four postactivation performance enhancement CAs on different occasions: [1] 3 sets x 4 s maximum isometric half squat (IHF), [2] 3 sets x 3 consecutive countermovement jumps (cCMJs), [3] 3 repetitions x 30 m overspeed sprinting (OVSP) and [4] dynamic submaximal half squat (2 sets x 2 reps x 90% of 1-RM half squat; HSQ). Significant improvements of sprinting performance were found 10 and 15 min following the cCMJs, OVSP and HSQ’s interventions, in all distances (p.05). Significant inter-individual differences were found in the magnitude of sprint performance improvements as well as in the optimal time window (p<.05), with the stronger sprinters responding better after HSQs, while the more powerful sprinters after cCMJs and OVSPs. In conclusion, it seems that cCMJs, OVSP and HSQ can acutely increase sprinting performance after 10 min, but CA’s induced increases in sprinting performance are highly related to the strength and power characteristics of each sprinter

A Brief Review on Concurrent Training: From Laboratory to the Field

The majority of sports rely on concurrent training (CT; e.g., the simultaneous training of strength and endurance). However, a phenomenon called &#8220;Concurrent training effect&#8222; (CTE), which is a compromise in adaptation resulting from concurrent training, appears to be mostly affected by the interference of the molecular pathways of the underlying adaptations from each type of training segments. Until now, it seems that the volume, intensity, type, frequency of endurance training, as well as the training history and background strongly affect the CTE. High volume, moderate, continuous and frequent endurance training, are thought to negatively affect the resistance training-induced adaptations, probably by inhibition of the Protein kinase B&#8212;mammalian target of rapamycin pathway activation, of the adenosine monophosphate-activated protein kinase (AMPK). In contrast, it seems that short bouts of high-intensity interval training (HIIT) or sprint interval training (SIT) minimize the negative effects of concurrent training. This is particularly the case when HIIT and SIT incorporated in cycling have even lower or even no negative effects, while they provide at least the same metabolic adaptations, probably through the peroxisome proliferator-activated receptor-&#947; coactivator (PGC-1a) pathway. However, significant questions about the molecular events underlying the CTE remain unanswered

Ταχύτητα αγωγής των νευρικών ώσεων στις μυϊκές ίνες και παραγωγή της μυϊκής ισχύος

Εισαγωγή. Η ταχύτητα αγωγής των δυναμικών ενέργειας των μυϊκών ινών έχει διερευνηθεί ελάχιστα στην αθλητική επιστήμη. Στο πλαίσιο της παρούσας διατριβής πραγματοποιήθηκαν τρεις ξεχωριστές, αλλά αλληλένδετες εργασίες, όπου σκοπός της πρώτης εργασίας ήταν η διερεύνηση της σχέσης μεταξύ της ταχύτητας αγωγής και της μυϊκής ισχύος όπως και του ρυθμού εφαρμογής της δύναμης, σκοπός της δεύτερης ήταν η διερεύνηση πιθανών διαφορών στην ταχύτητα αγωγής μεταξύ αθλητών δύναμης, ισχύος και αντοχής και σκοπός της τρίτης μελέτης ήταν η διερεύνηση της επίδρασης της προπόνησης ισχύος και του συνδυασμού προπόνησης ισχύος με αερόβια προπόνηση στην ταχύτητα αγωγής των νευρικών ώσεων στις μυϊκές ίνες. Μέθοδος. Στην 1η εργασία αξιολογήθηκε η μυϊκή ισχύς, ο ρυθμός εφαρμογής της δύναμης και η ταχύτητα αγωγής μέσω προκλητών δυναμικών με ενδομυϊκά ηλεκτρόδια σε 15 νεαρές γυναίκες (ηλικία 21,1±0,4 έτη, ανάστημα 165±4,5 cm, μάζα 56,7±6 kg, δείκτης μάζας σώματος 20,8±1,7 kg•m-2, ισχύς αποτελεσμάτων 0,958). Στη 2η εργασία πραγματοποιήθηκαν οι ίδιες αξιολογήσεις σε 38 νεαρούς άνδρες (ισχύς αποτελεσμάτων 0,936) με διαφορετικό προπονητικό υπόβαθρο: μαραθωνοδρόμοι (n=9), αθλητές ισχύος (n=10), αθλητές δύναμης (n=9), αγύμναστοι (n=10). Εκτός από τις προαναφερόμενες μετρήσεις, πραγματοποιήθηκε μυϊκή βιοψία στον έξω πλατύ μηριαίο μυ για την αξιολόγηση της μορφολογίας των μυϊκών ινών. Στην 3η έρευνα, 17 μέτρια γυμνασμένες γυναίκες (21,62,2 ετών, ανάστημα 166,35,4 εκ., μάζα 57,66,8 kg, ισχύς αποτελεσμάτων: 0,910), χωρίστηκαν σε 2 πειραματικές ομάδες: oμάδα προπόνησης ισχύος (Π.Ι.; n=8) και oμάδα προπόνησης ισχύος-αερόβιας (Π.Ι.Α.; n=9). Πριν και μετά την προπονητική παρέμβαση, διάρκειας 6 εβδομάδων, πραγματοποιήθηκαν οι ίδιες αξιολογήσεις όπως στην 2η έρευνα. Αποτελέσματα. Στην 1η και 2η έρευνα, σημαντικές συσχετίσεις βρέθηκαν μεταξύ της ταχύτητας αγωγής και της μέγιστης ισχύος κατά το άλμα με αιώρηση, της μέγιστης ισομετρικής δύναμης, καθώς και του ρυθμού εφαρμογής της δύναμης στα 50-250ms (συντελεστής Pearson r=0,538-0,924; p&lt;0,01). Η ταχύτητα αγωγής σχετίζονταν υψηλότερα με τον ρυθμό εφαρμογής της δύναμης (r: 0,538-0,918; p&lt;0,01) παρά με τη μέγιστη ισομετρική δύναμη (r: 0,599-0,656; p&lt;0,01). Ωστόσο, όπως φάνηκε από την 2η έρευνα οι συσχετίσεις αυτές επηρεάζονται από την εγκάρσια επιφάνεια και το ποσοστό καταλαμβανόμενης επιφάνειας των μυϊκών ινών τύπου ΙΙ. Επίσης βρέθηκε ότι ο στατιστικός γραμμικός συνδυασμός της ταχύτητας αγωγής και της μυϊκής ισχύος μπορεί να προβλέψει την εγκάρσια επιφάνεια και το ποσοστό καταλαμβανόμενης επιφάνειας των μυϊκών ινών τύπου ΙΙ. Στην 3η έρευνα διαπιστώθηκε ότι 6 εβδομάδες προπόνησης ισχύος προκαλούν αύξηση της ταχύτητας αγωγής, του μεγέθους των μυϊκών ινών και της μυϊκής ισχύος, ενώ η προσθήκη ήπιας έντασης αερόβιας άσκησης εκμηδενίζει αυτές τις αυξήσεις. Στο σύνολο των δοκιμαζόμενων, η ποσοστιαία μεταβολή της ταχύτητας αγωγής συσχετιζόταν με την ποσοστιαία μεταβολή του μεγέθους των μυϊκών ινών και της μυϊκής ισχύος (r=0,574 ώς 0,628; p&lt;0,05). Ωστόσο, οι συσχετίσεις μεταξύ της ποσοστιαίας μεταβολής της ταχύτητας αγωγής και της μυϊκής ισχύος, επηρεάζονταν από την ποσοστιαία μεταβολή της εγκάρσιας επιφάνειας των μυϊκών ινών. Συμπεράσματα. Τα αποτελέσματα δείχνουν ότι η ταχύτητα αγωγής των μυϊκών ινών του έξω πλατύ, συνδέεται στενά με την απόδοση σε εκρηκτικές πολυαρθρικές δραστηριότητες. Παράλληλα, φαίνεται ότι τη ταχύτητα αγωγής συνδέεται καλύτερα με τον ρυθμό εφαρμογής της δύναμης κατά την πραγματοποίηση εκρηκτικών δραστηριοτήτων παρά με τη μέγιστη δύναμη. Επιπρόσθετα, όπως είναι γνωστό, το είδος της συστηματικής προπόνησης προκαλεί διαφορετικές προσαρμογές στην εγκάρσια επιφάνεια των μυϊκών ινών. Τα αποτελέσματα της παρούσας εργασίας δείχνουν ότι οι αλλαγές στην εγκάρσια επιφάνεια των ινών προκαλούν αλλαγές στην ταχύτητα αγωγής κάτι που δείχνει ότι η ταχύτητα αγωγής είναι ένα χαρακτηριστικό το οποίο καθορίζεται σε μεγάλο βαθμό από το μέγεθος των μυϊκών ινών και μπορεί να αλλάζει ανάλογα με τα χαρακτηριστικά του προπονητικού ερεθίσματος. Η προσθήκη αερόβιας άσκησης χαμηλής έντασης στην προπόνηση ισχύος αναστέλλει τη μυϊκή υπερτροφία, και που οδηγεί σε αναστολή της αύξησης της ταχύτητας αγωγής

Can Exercise-Induced Muscle Damage Be a Good Model for the Investigation of the Anti-Inflammatory Properties of Diet in Humans?

Subclinical, low-grade, inflammation is one of the main pathophysiological mechanisms underlying the majority of chronic and non-communicable diseases. Several methodological approaches have been applied for the assessment of the anti-inflammatory properties of nutrition, however, their impact in human body remains uncertain, because of the fact that the majority of the studies reporting anti-inflammatory effect of dietary patterns, have been performed under laboratory settings and/or in animal models. Thus, the extrapolation of these results to humans is risky. It is therefore obvious that the development of an inflammatory model in humans, by which we could induce inflammatory responses to humans in a regulated, specific, and non-harmful way, could greatly facilitate the estimation of the anti-inflammatory properties of diet in a more physiological way and mechanistically relevant way. We believe that exercise-induced muscle damage (EIMD) could serve as such a model, either in studies investigating the homeostatic responses of individuals under inflammatory stimuli or for the estimation of the anti-inflammatory or pro-inflammatory potential of dietary patterns, foods, supplements, nutrients, or phytochemicals. Thus, in this review we discuss the possibility of exercise-induced muscle damage being an inflammation model suitable for the assessment of the anti-inflammatory properties of diet in humans

Rate of Force Development and Muscle Architecture after Fast and Slow Velocity Eccentric Training

The aim of the study was to investigate the rate of force development (RFD) and muscle architecture early adaptations in response to training with fast- or slow-velocity eccentric squats. Eighteen young novice participants followed six weeks (two sessions/week) of either fast-velocity (Fast) or slow-velocity (Slow) squat eccentric-only training. Fast eccentric training consisted of nine sets of nine eccentric-only repetitions at 70% of 1-RM with &lt;1 s duration for each repetition. Slow eccentric training consisted of five sets of six eccentric-only repetitions at 90% of 1-RM with ~4 sec duration for each repetition. Before and after training, squat 1-RM, countermovement jump (CMJ), isometric leg press RFD, and vastus lateralis muscle architecture were evaluated. Squat 1-RM increased by 14.5 &#177; 7.0% (Fast, p &lt; 0.01) and by 5.4 &#177; 5.1% (Slow, p &lt; 0.05). RFD and fascicle length increased significantly in the Fast group by 10&#8315;19% and 10.0 &#177; 6.2%, p &lt; 0.01, respectively. Muscle thickness increased only in the Slow group (6.0 &#177; 6.8%, p &lt; 0.05). Significant correlations were found between the training induced changes in fascicle length and RFD. These results suggest that fast eccentric resistance training may be more appropriate for increases in rapid force production compared to slow eccentric resistance training, and this may be partly due to increases in muscle fascicle length induced by fast eccentric training

The Effect of Bodyweight Support and Incline Running on Triceps Surae Electromyographic Activity

Body weight support (BWS) and incline running (IR) are commonly used either during rehabilitation or during training separately, with many positive effects on athletes' performance and rehabilitation. The aim of the present study was to investigate the interaction between bodyweight support and incline running on the electromyographic activity of the triceps surae and compare it to flat running. In eighteen healthy men (age: 20.3 ± 1.2 years, body weight: 70.2 ± 4.8 kg, body height: 179.6 ± 5.4 cm), the changes in electromyographic activity (EMGA) during a 10 min run with BWS (15% or 30% of body weight; in different occasions) and IR at 7%, as well as jumping performance and gait spatiotemporal parameters, were evaluated. A lower Rating of Perceived Exertion and a significant decrease in the size of the Vastus Lateralis (VL) (33.4%), Soleus (SOL) (17%), and Gastrocnemius Lateralis (GL) EMGA (28.5%, p 0.05), was observed during BWS30% at 7% slope compared to flat running. Also, low-frequency fatigue of the quadriceps was induced only after running without BWS on a 7% slope (p = 0.011). No changes were found in jumping performance (p = 0.246) and gait spatiotemporal parameters (p > 0.05) except for flight time (p < 0.006). In conclusion, running with a slope of 7% and 30% of BWS can result in EMG activity comparable to that observed during level running. This method can also be used in prevention and rehabilitation training programs without creating fatigue

The Importance of Lean Body Mass for the Rate of Force Development in Taekwondo Athletes and Track and Field Throwers

The rate of force development (RFD) is vital for power athletes. Lean body mass (LBM) is considered to be an essential contributor to RFD, nevertheless high RFD may be achieved by athletes with either high or low LBM. The aim of the study was to describe the relationship between lower-body LBM and RFD, and to compare RFD in taekwondo athletes and track and field (T&amp;F) throwers, the latter having higher LBM when compared to taekwondo athletes. Nine taekwondo athletes and nine T&amp;F throwers were evaluated for countermovement jumping, isometric leg press and leg extension RFD, vastus lateralis (VL), and medial gastrocnemius muscle architecture and body composition. Lower body LBM was correlated with RFD 0&ndash;250 ms (r = 0.81, p = 0.016). Taekwondo athletes had lower LBM and jumping power per LBM. RFD was similar between groups at 30&ndash;50 ms, but higher for throwers at 80&ndash;250 ms. RFD adjusted for VL thickness was higher in taekwondo athletes at 30 ms, but higher in throwers at 200&ndash;250 ms. These results suggest that lower body LBM is correlated with RFD in power trained athletes. RFD adjusted for VL thickness might be more relevant to evaluate in power athletes with low LBM, while late RFD might be more relevant to evaluate in athletes with higher LBM

Effect of Different Local Vibration Durations on Knee Extensors' Maximal Isometric Strength

The prolonged application (>20 min) of local vibration (LV) on muscles or tendons is known to reduce maximal isometric strength. However, the effect of short vibration durations (≤6 min) is still unknown. In fourteen participants, the changes in maximal voluntary isometric contraction (MVIC) were measured after 1, 3, and 6 min of rest (CONT) or local vibration (LV) over the quadricipital tendon (frequency: 100 Hz; amplitude: 0.5 mm). Before and after each condition, the amplitude of the twitch induced by a 100 Hz potentiated electrical doublet (PD POT); the relative electromyographic activity of the vastus medialis and rectus femoris muscle during the MVIC (RMS MVIC .M −1); the torque developed 50 ms after the onset of contraction (T 50); and the voluntary activation level (VAL) were evaluated. None of the three LV durations significantly changed the MVIC compared with the control condition (p = 0.379). The indices of central (i.e., VAL, T 50 , RMS MVIC .M −1) and peripheral (e.g., PD POT) fatigue were unaffected (p > 0.147). In conclusion, a short-duration LV (≤6 min) on a voluminous muscle group does not impair maximal force production or induce any central or peripherical fatigue