The Effect of Warm-up Running Technique on Sprint Performance.

ABSTRACT: Gil, MH, Neiva, HP, Alves, AR, Sousa, AC, Ferraz, R, Marques, MC, and Marinho, DA. The effect of warm-up running technique on sprint performance. J Strength Cond Res 35(12): 3341-3347, 2021-The purpose of the current study was to analyze the effect of changing the running technique during warm-up on sprint performances, running biomechanics, physiological, and psychophysiological responses. Thirty-one physically active men aged 18-23 years (mean ± SD: 19.35 ± 1.08 years of age; 1.77 ± 0.07 m of height; 71.90 ± 10.37 kg of body mass) volunteered to participate and randomly performed 2 maximal 30-m sprints, 5 minutes after completing a warm-up focused on increased stride length-SL (WUL) or a warm-up focused on increased stride frequency-SF (WUF). The results showed that there were no differences between the 30-m sprint performances and in running biomechanics. However, WUF showed increased performances in the first 15 m of the race (WUF: 2.59 ± 0.11 seconds vs. WUL: 2.63 ± 0.15 seconds; p = 0.03), and WUL resulted in higher performances in the last 15 m (1.94 ± 0.19 seconds vs. 1.88 ± 0.09 seconds; p = 0.05). In the second 30-m time trial, WUF also resulted in faster starting 15 m of the race (2.58 ± 0.12 seconds vs. 2.63 ± 0.16 seconds; p = 0.04). Interestingly, the WUF was the warm-up that revealed more stability in performances and running biomechanics between both trials. These results showed that there were no significant differences between warm-ups comprising exercises focusing in higher SL or higher SF in 30-m sprint biomechanics and performance. Nevertheless, different running strategies were caused by those 2 warm-ups and a more stabilized running pattern, and performance values were found when warm-up focused on higher SF.

Does the inclusion of ballistic exercises during warm-up enhance short distance running performance?

BACKGROUND: Warm-up is considered essential to optimize running performance, but little is known about the effect of specific warm-up tasks, specifically in the real competitive context. The current study aimed to verify the acute effects of a warm-up including ballistic exercises in 30m running performance. In addition, a second 30m trial was assessed to better understand the warm-up effects in training/competition. METHODS: Twenty-two men (19.32±1.43 years-old) randomly completed the time-trials on separate days and after a typical warm-up (WU), a WU complemented with ballistic exercises (postactivation potentiation [PAP]) or no warm-up (NWU). Biomechanical, physiological and psychophysiological variables were assessed. RESULTS: The participants were 1.9% faster in the first 30m sprint after WU compared with NWU, mainly increased performance in the first 15m (P=0.03, ES=0.48). WU resulted in greater stride length in the last 15m of the first sprint. PAP did not differ from NWU and WU, despite eight participants performed better after this warm-up. CONCLUSIONS: These results highlight the positive effects of warm-up for sprinting, despite failed to evidence positive effects when ballistic exercises are included. In addition, the influence of warm-up in the running technique was highlighted by the changes in the running kinematics and a need for individualization of warm-up procedures.

Concurrent Training and Detraining: The Influence of Different Aerobic Intensities.

Sousa, AC, Neiva, HP, Gil, MH, Izquierdo, M, Rodríguez-Rosell, D, Marques, MC, and Marinho, DA. Concurrent training and detraining: the influence of different aerobic intensities. J Strength Cond Res 34(9): 2565-2574, 2020-The aim of this study was to verify the effects of different aerobic intensities combined with the same resistance training on strength and aerobic performances. Thirty-nine men were randomly assigned to a low-intensity group (LIG), moderate-intensity group (MIG), high-intensity group (HIG), and a control group. The training program consisted of full squat, jumps, sprints, and running at 80% (LIG), 90% (MIG), or 100% (HIG) of the maximal aerobic speed for 16-20 minutes. The training period lasted for 8 weeks, followed by 4 weeks of detraining. Evaluations included 20-m sprints (0-10 m: T10; 0-20 m: T20), shuttle run, countermovement jump (CMJ), and strength (1RMest) in full squat. There were significant improvements from pre-training to post-training in T10 (LIG: 4%; MIG: 5%; HIG: 2%), T20 (3%; 4%; 2%), CMJ (9%; 10%; 7%), 1RMest (13%; 7%; 8%), and oxygen uptake (V[Combining Dot Above]O2max; 10%; 11%; 10%). Comparing the changes between the experimental groups, 1RMest gains were significantly higher in the LIG than HIG (5%) or MIG (6%). Furthermore, there was a tendency for higher gains in LIG and MIG compared with HIG, with "possibly" or "likely" positive effects in T10, T20, and CMJ. Detraining resulted in performance decrements, but minimal losses were found for V[Combining Dot Above]O2max in LIG (-1%). Concurrent training seems to be beneficial for strength and aerobic development regardless of the aerobic training intensity. However, choosing lower intensities can lead to increased strength and is recommended when the cardiorespiratory gains should be maintained for longer.

Acute effects of low and high-volume resistance training on hemodynamic, metabolic and neuromuscular parameters in older adults.

OBJECTIVE: To analyze the acute effects of low or high-volume resistance training (RT) on hemodynamic, metabolic and neuromuscular parameters in institutionalized older adults. METHODS: Thirty-one subjects (78.9 ±â€¯7.2 years old) performed two RT protocols (low versus high-volume), separated by one-week rest. Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR) and blood lactate concentration ([La-]) were evaluated before and immediately after both RT protocols. The seated medicine ball throw (SMBT) was evaluated before and 5 min after both sessions, the countermovement jump (CMJ) height was evaluated before and 6 min after both RT protocols and the absolute handgrip strength (HGS) was evaluated before and 7 min after both RT protocols. RESULTS: At baseline, no significant differences between RT protocols were found in all variables. After training session, both RT protocols induced significant increases in SBP (low versus high-volume: 5.3% vs 10.7%), DBP (5.9% vs 6.8%), HR (6.8% vs 17.9%) and [La-] (86.1% vs 200.0%). Moreover, the high-volume protocol induced significant decreases in SMBT (-2.5%) and CMJ (-8.3%), whilst the low-volume protocol significantly increased the HGS (3.4%). CONCLUSIONS: Both RT protocols induced significant acute responses on cardiovascular and metabolic parameters, as well as on neuromuscular function in institutionalized older adults. However, a greater acute response after the high-volume RT protocol was found, thus reflecting greater hemodynamic, metabolic and neuromuscular stress than low-volume RT. Moreover, low-volume RT showed an acute increase in general strength.

The Effect of Ballistic Exercise as Pre-Activation for 100 m Sprints.

The benefits of warm-up in sports performance has received a special interest in the current literature. However, there is a large gap of knowledge about the tasks to be performed, specifically in the real competitive environment. The purpose of the study was to verify the acute effects of a warm-up including ballistic exercises in 100 m running performance. In addition, a second 100 m trial was assessed to better understand the warm-up effects in training and competition. Eleven men (25.4 ± 6.2 years of age, 1.76 ± 0.08 m of height, 78.2 ± 8.6 kg of body mass) were submitted to three different protocols, in a randomized order: no warm-up (NWU), typical warm-up (WU) and WU complemented with ballistic exercises (PAP). Biomechanical, physiological and psychophysiological variables were assessed. Differences were found between the three conditions assessed in the first 100 m sprint with 7.4% and 7.6% faster performances after the WU and PAP, compared to NWU. Stride length was higher in the second part of the 100 m after PAP compared with WU. These results highlight the positive effects of warm-up for sprinting performance. The inclusion of ballistic exercises, besides being used to improve sprint performance, can increase stride length in the final of the 100 m race.

Preparation of gentamicin sulfate eluting fiber mats by emulsion and by suspension electrospinning.

This work investigates the immobilization of the antibiotic gentamicin sulfate (GS) in electrospun fiber mats composed of poly(lactic acid) (PLA), poly(ε-caprolactone) (PCL) and the copolymer poly(lactic-co-glycolic acid) (PLGA). Since GS is highly water soluble but weakly soluble in the organic solvents commonly used in the electrospinning process, two methods of immobilization were investigated: by suspension electrospinning, in which GS particles were directly dispersed in the polymeric organic solutions, and by emulsion electrospinning, in which GS was solubilized in an aqueous phase that was then dispersed in the organic polymeric solution containing the surfactant SPAN80. Fibers with distinct diameters and morphologies were obtained for the different methods and compositions. Contrary to the fibers prepared by suspension electrospinning, emulsion electrospinning based fibers exhibited an excellent wettability, allegedly due to the effect of the surfactant SPAN80. Despite the differences between both methods the produced mats presented similar GS release profiles, with a considerable burst release in the first 8 h followed by a gradual release of the remaining drug during the next 4-6 days. Finally, all GS loaded fiber mats proved to have an antibacterial effect against the bacterial strain Staphylococcus aureus.

Concurrent Training Followed by Detraining: Does the Resistance Training Intensity Matter?

Sousa, AC, Marinho, DA, Gil, MH, Izquierdo, M, Rodríguez-Rosell, D, Neiva, HP, and Marques, MC. Concurrent training followed by detraining: does the resistance training intensity matter? J Strength Cond Res 32(3): 632-642, 2018-The aim of this study was to analyze the training and detraining (DT) effects of concurrent aerobic training and resistance training against 3 different external loads on strength and aerobic variables. Thirty-two men were randomly assigned to 4 groups: low-load (LLG, n = 9), moderate-load (MLG, n = 9), high-load (HLG, n = 8), and control group (CG, n = 6). Resistance training consisted of full squat (FS) with a low load (40-55% 1 repetition maximum [1RM]), a moderate load (55-70% 1RM), or a high load (70-85% 1RM) combined with jump and sprint exercises. Aerobic training was performed at 75% of the maximal aerobic speed for 15-20 minutes. The training period lasted for 8-week, followed by 4-week DT. Pretraining, post-training, and post-DT evaluations included 20-m running sprints (0-10 m: T10; 0-20 m: T20), shuttle run test, countermovement vertical jump (CMJ) test, and loading test (1RM) in FS. All the experimental groups showed improvements (p ≤ 0.05) in all the parameters assessed, except the LLG for T10 and the HLG for T20. The LLG, MLG, and HLG showed great changes in 1RM and V[Combining Dot Above]O2max compared with the CG (p ≤ 0.05), whereas the HLG and MLG showed a greater percentage change than the CG in T10 (p < 0.001) and CMJ (p ≤ 0.05). The 4-week DT period resulted in detrimental effects in all variables analyzed for all 3 experimental groups. In conclusion, our results suggest that strength training programs with low, moderate, or high external loads combined with low-intensity aerobic training could be effective for producing significant gains in strength and aerobic capacities. Moreover, the higher loads used increased gains in explosive efforts.

Poly(ester amide)s based on (L)-lactic acid oligomers and α-amino acids: influence of the α-amino acid side chain in the poly(ester amide)s properties.

Novel biodegradable and low cytotoxic poly(ester amide)s (PEAs) based on α-amino acids and (L)-lactic acid (L-LA) oligomers were successfully synthesized by interfacial polymerization. The chemical structure of the new polymers was confirmed by spectroscopic analyses. Further characterization suggests that the α-amino acid plays a critical role on the final properties of the PEA. L-phenylalanine provides PEAs with higher glass transition temperature, whereas glycine enhances the crystallinity. The hydrolytic degradation in PBS (pH = 7.4) at 37 °C also depends on the α-amino acid, being faster for glycine-based PEAs. The cytotoxic profiles using fibroblast human cells indicate that the PEAs did not elicit an acute cytotoxic effect. The strategy presented in this work opens the possibility of synthesizing biodegradable PEAs with low citotoxicity by an easy and fast method. It is worth to mention also that the properties of these materials can be fine-tuned only by changing the α-amino acid.

VEGF-functionalized dextran has longer intracellular bioactivity than VEGF in endothelial cells.

Herein, we report that VEGF-functionalized dextran (dexOx-VEGF) is comparatively superior to free VEGF in prolonging the phosphorylation of VEGF receptor 2 (VEGFR-2). Both dexOx-VEGF and free VEGF activate VEGFR-2, and the complexes are internalized into early endosomes (EEA1(+) vesicles) and then transported to lysosomes (Rab7(+) vesicles). However, after cell activation, dexOx-VEGF is preferentially colocalized in early endosomes where VEGF signaling is still active while free VEGF is preferentially transported to late endosomes or lysosomes. We further show that dexOx-VEGF after phosphorylation of VEGF receptor 2 induces an increase of intracellular Ca(2+) and activates VEGF downstream effectors such as Akt and extracellular signal-regulated kinase (ERK1/2) proteins. Under specific conditions, the activation level is different from the one observed for free VEGF, thus suggesting mechanistic differences, which is illustrated by cell migration and cord-like formation studies. DexOx-VEGF can be cross-linked with adipic acid dihydrazide to form a degradable gel, which in turn can be incorporated in a fibrin gel containing endothelial cells (ECs) to modulate their activity. We envision that these constructs might be beneficial to extend the pro-angiogenic activity of VEGF in ischemic tissues and to modulate the biological activity of vascular cells.

Synthesis and Characterization of Co-polymers Based on Methyl Methacrylate and 2-Hexyl Acrylate Containing Naphthopyrans for a Light-Sensitive Contact Lens.

Three different naphthopyrans were incorporated in co-polymers of methyl methacrylate (MMA) and 2-ethylhexyl acrylate (EHA), with and without cross-linking with ethyleneglycol dimethacrylate (EGDMA), by a free radical polymerization method. The obtained materials were characterised in terms of some of their chemical and physical properties that could be important for the final functional properties of the envisaged application. Despite other important functional properties that should be evaluated in the near future, the system based in the physical entrapment of 3,3-bis(4-methoxyphenyl)-3H-naphtho [2,1-b]pyran presented a good potential for its application as novel light-sensitive contact lenses.

Supercritical fluid-assisted preparation of imprinted contact lenses for drug delivery.

The aim of this work was to develop an innovative supercritical fluid (SCF)-assisted molecular imprinting method to endow commercial soft contact lenses (SCLs) with the ability to load specific drugs and to control their release. This approach seeks to overcome the limitation of the common loading of preformed SCLs by immersion in concentrated drug solutions (only valid for highly water soluble drugs) and of the molecular imprinting methods that require choice of the drug before polymerization and thus to create drug-tailored networks. In particular, we focused on improving the flurbiprofen load/release capacity of daily wear Hilafilcon B commercial SCLs by the use of sequential SCF flurbiprofen impregnation and extraction steps. Supercritical carbon dioxide (scCO2) impregnation assays were performed at 12.0 MPa and 40 °C, while scCO2 extractions were performed at 20.0 MPa and 40 °C. Conventional flurbiprofen sorption and drug removal experiments in aqueous solutions were carried out for comparison purposes. SCF-processed SCLs showed a recognition ability and a higher affinity for flurbiprofen in aqueous solution than for the structurally related ibuprofen and dexamethasone, which suggests the creation of molecularly imprinted cavities driven by both physical (swelling/plasticization) and chemical (carbonyl groups in the network with the C-F group in the drug) interactions. Processing with scCO2 did not alter some of the critical functional properties of SCLs (glass transition temperature, transmittance, oxygen permeability, contact angle), enabled the control of drug loaded/released amounts (by the application of several consecutive processing cycles) and permitted the preparation of hydrophobic drug-based therapeutic SCLs in much shorter process times than those using conventional aqueous-based molecular imprinting methods.

Drug delivery systems: Advanced technologies potentially applicable in personalized treatments.

Advanced drug delivery systems (DDS) present indubitable benefits for drug administration. Over the past three decades, new approaches have been suggested for the development of novel carriers for drug delivery. In this review, we describe general concepts and emerging research in this field based on multidisciplinary approaches aimed at creating personalized treatment for a broad range of highly prevalent diseases (e.g., cancer and diabetes). This review is composed of two parts. The first part provides an overview on currently available drug delivery technologies including a brief history on the development of these systems and some of the research strategies applied. The second part provides information about the most advanced drug delivery devices using stimuli-responsive polymers. Their synthesis using controlled-living radical polymerization strategy is described. In a near future it is predictable the appearance of new effective tailor-made DDS, resulting from knowledge of different interdisciplinary sciences, in a perspective of creating personalized medical solutions.

Ocular injectable formulation assessment for oxidized dextran-based hydrogels.

Initiator-free injectable hydrogels are very interesting for drug and/or cell delivery applications, since they can be administered in a minimally invasive way, and avoid the use of potentially harmful chemical initiators. In the current work, oxidized dextran crosslinked with adipic acid dihydrazide hydrogels were further characterized and tuned to produce formulations, with the aim of producing an injectable formulation for the possible treatment of posterior eye diseases. The gelation rate and the hydrogel dissolution profile were shown to be dependent on the balance between the degree of dextran oxidation, and the concentration of both components. For the in vitro studies, rabbit corneal endothelial cells were seeded on the hydrogels to assess cytotoxicity. Hydrogels prepared with low oxidized dextrans were able to promote cell adhesion and proliferation to confluence in just 24h, while more highly oxidized samples promoted cell adhesion and proliferation, but without achieving confluence. Cell viability studies were performed using MTS assays to verify the non-cytotoxicity of hydrogels and their degradation byproducts, rendering these formulations attractive for further in vivo studies.

New approaches in drug delivery systems: application for diabetes treatment.

Advanced drug delivery systems present indubitable advantages for drug administration. During the past three decades, new approaches for the development of new carriers for this topic have been suggested. This led to explosion of publication activity in the area. This article reviews briefly the history of the topic and focuses on general concepts in the issue. One of the most crucial properties of advanced delivery systems is their ability to be well controlled in terms of a carrier structure which is responsible for an optimal drug release. Here we describe new polymerization technologies which consider this particular aspect. A special attention is paid to the preparation of materials by LRP (Living Radical Polymerization) and perspectives of its practical application to the treatment of single diseases. Due to the epidemic scale of Diabetes mellitus, novel drug delivery systems play an important role in and are highly relevant for improved treatment of worldwide permanently growing sub-population of diabetic patients. Type 1 is the insulin-dependent diabetes which accounts for 5 till 10 percent of the whole pool of diabetic cases and currently attracts main attention in research activity devoted to the development of advanced drug delivery systems. Minimal invasive insulin administration approaches and/or improvement of pancreatic activity in own insulin production is the main goal of novel drug delivery systems highly desirable for advanced treatment of diabetic patients with both type 1 and type 2 of the disease.

Preparation and characterization of flurbiprofen-loaded poly(3-hydroxybutyrate-co-3-hydroxyvalerate) microspheres.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) microspheres containing flurbiprofen were prepared by an oil-in-water emulsion solvent evaporation method, in order to develop a particulate drug delivery system for localized administration. A response surface method (RSM) using a central composite design was employed to evaluate the effect of the poly(vinyl alcohol) (PVA) (%, w/v) concentration in the aqueous phase and the PHBV concentration in the organic phase (%, w/v) on some of the resulting microspheres properties. The response variables were the encapsulation efficiency (EE), the mean particle size, the width of particle size distribution (expressed by the SPAN value) and the required time for the in vitro release of 50% of the encapsulated drug (t(50%)). Second-order polynomial and linear equations were fitted to experimental data and were also used to interpret the results. Results indicated that the concentration of the stabilizer (PVA) showed a highly negative effect on the EE probably due to the increased drug solubility in the aqueous phase as a result of the higher PVA concentrations. Particle diameter mean size increased with the increased polymer concentration while the width of the particle size distribution was found to decrease with the increase of the stabilizer agent. Finally, results indicated that none of the investigated variables presented a significant effect on the t(50%) values.

Biocatalytic synthesis of highly ordered degradable dextran-based hydrogels.

We have prepared unique macroporous and ordered dextran-based hydrogels using a single-step biocatalytic transesterification reaction between dextran and divinyladipate in neat dimethylsulfoxide. These hydrogels show a unimodal distribution of interconnected pores with average diameters from 0.4 to 2.0 microm depending on the degree of substitution. In addition, the hydrogels show a higher elastic modulus for a given swelling ratio than chemically synthesized dextran-based hydrogels. In vivo studies in rats show that the hydrogel networks are degradable over a range of time scales from 5 to over 40 days, and possess good biocompatibility, as reflected in only a mild inflammatory reaction and minor fibrous capsule formation during the time-frame of subcutaneous implantation. These combined properties may offer competitive advantages in biomedical applications ranging from tissue engineering to controlled drug delivery.

Immobilisation of cardosin A in chitosan sponges as a novel implant for drug delivery.

Cardosin A is extracted from the pistils of the plant Cynara cardunculus L. and chitosan is a polysaccharide derived from chitin with valuable properties as a biomaterial. In this work we report our experiments on the synthesis of chitosan sponges and immobilisation of cardosin A, by entrapment. We observed that 10-15% of the incorporated cardosin A were released over 6 days of incubation. In addition, we could also note that this immobilisation procedure did not induce any specificity alterations on cardosin A. The specificity study of the enzyme, using beta-chain of oxidised insulin, showed that the immobilised and released enzymes have the same hydrolysis pattern as the free enzyme. The ability of this enzyme to hydrolyse type I collagen was maintained, after the immobilisation procedure. The biocompatibility in vivo of these sponges was evaluated by histological staining after implantation in rats submitted to abdominal surgery. Results of this study demonstrated that these chitosan sponges are very promising vehicles for the application of cardosin A, in abdominal cavity for prevention and reduction of the adhesions formation.

Biocompatibility of chemoenzymatically derived dextran-acrylate hydrogels.

The biocompatibility of chemoenzymatically generated dextran-acrylate hydrogels has been evaluated in vitro, using human foreskin fibroblasts, and in vivo, by subcutaneous and intramuscular implantation in Wistar rats for up to 40 days. In vitro tests show that hydrogel extracts only minimally reduced (<10%) the mitochondrial metabolic activity of fibroblasts. Direct contact of the hydrogels with cells induced a cellular proliferation inhibition index (CPII) of 50-80%, compared with a control, whereas through indirect contact, the CPII values were <16%, suggesting that the high CPII values achieved in the direct assay test were likely due to mechanical stress or limitations in oxygen diffusion. Hence, the hydrogels were noncytotoxic. Moreover, cell-material interaction studies show that these hydrogels were nonadhesive. Finally, histologic evaluation of tissue response to subcutaneous and intramuscular implants showed acceptable levels of biocompatibility, as characterized by a normal cellular response and the absence of necrosis of the surrounding tissues of the implant. In the first 10 days, the foreign-body reaction in the intramuscular implantation was more severe than in subcutaneous implantation, becoming identical after 30 days. In both cases, dextran hydrogels did not show signs of degradation 6 weeks postimplantation and were surrounded by a thin fibrous capsule and some macrophages and giant cells. This response is typical with a number of nondegradable biocompatible materials. These results indicate that dextran hydrogels are biocompatible, and may have suitable applications as implantable long-term peptide/protein delivery systems or scaffolds for tissue engineering.

Enzymatic synthesis of dextran-containing hydrogels.

Dextran, a natural glucose-containing polysaccharide, has been acylated by Proleather FG-F and lipase AY, a protease and lipase from Bacillus sp. and Candida rugosa, respectively, in anhydrous dimethylsulfoxide in the presence of vinyl acrylate (VA). The efficiency of the reaction in the presence of Proleather FG-F and the isolated yields were ca. 71% and 45%, respectively. Dextran derivatized with VA (dexT70-VA) was characterized by gel permeation chromatography and its structure was established by NMR indicating two positional isomers at the 2 and 3 positions on the glucose moieties in equal amounts. Furthermore, the dextran glucopyranose residues were mono-substituted. The benefits of the biocatalytic synthesis of dextran acrylates was demonstrated using 4-dimethylaminopyridine as a chemical catalyst. Gels were prepared by free radical polymerization of aqueous solutions of dexT70-VA with different degrees of substitution and monomer concentrations. Intermolecular linkages and physical entanglements are predominantly formed by concentrated solutions, however, a part of the acrylate groups did not react. Gel pore sizes were calculated from swelling experiments and ranged from ca. 18 to 182 A.