Graphene oxide modulates inter-particle interactions in 3D printable soft nanocomposite hydrogels restoring magnetic hyperthermia responses.

Hydrogels loaded with magnetic iron oxide nanoparticles that can be patterned and which controllably induce hyperthermic responses on AC-field stimulation are of interest as functional components of next-generation biomaterials. Formation of nanocomposite hydrogels is known to eliminate any Brownian contribution to hyperthermic response (reducing stimulated heating) while the Néel contribution can also be suppressed by inter-particle dipolar interactions arising from aggregation induced before or during gelation. We describe the ability of graphene oxide (GO) flakes to restore the hyperthermic efficiency of soft printable hydrogels formed using Pluronics F127 and PEGylated magnetic nanoflowers. Here, by varying the amount of GO in mixed nanocomposite suspensions and gels, we demonstrate GO-content dependent recovery of hyperthemic response in gels. This is due to progressively reduced inter-nanoflower interactions mediated by GO, which largely restore the dispersed-state Néel contribution to heating. We suggest that preferential association of GO with the hydrophobic F127 blocks increases the preponderance of cohesive interactions between the hydrophilic blocks and the PEGylated nanoflowers, promoting dispersion of the latter. Finally we demonstrate extrusion-based 3D printing with excellent print fidelity of the magnetically-responsive nanocomposites, for which the inclusion of GO provides significant improvement in the spatially-localized open-coil heating response, rendering the prints viable components for future cell stimulation and delivery applications.

Changes in Neuromuscular Status Across a Season of Professional Men's Ice Hockey.

ABSTRACT: Gannon, EA, Higham, DG, Gardner, BW, Nan, N, Zhao, J, and Bisson, LJ. Changes in neuromuscular status across a season of professional men's ice hockey. J Strength Cond Res 35(5): 1338-1344, 2021-To quantify changes in neuromuscular function over a full professional men's ice hockey season, 27 players (n = 18 forwards and 9 defensemen) performed 3 countermovement jumps (CMJ) each week over 30 sessions separated into 4 phases: preseason, early-season, midseason, and late-season. Outcome variables represented jump performance (jump height), kinematics (mean velocity and peak velocity), and movement strategy (countermovement depth). Mixed models characterized relationships between positional group, season phase, and CMJ outcomes. Statistical significance was set at p ≤ 0.05. Concentric peak velocity (p = 0.02), jump height (p = 0.001), and countermovement depth (p < 0.001) displayed a significant reduction across the season. Peak velocity was lower during the early-season than the preseason (-0.10 ± 0.06 m·s-1, mean change ± 95% confidence limit, p = 0.05). Countermovement depth was reduced during the early-season (-0.06 ± 0.03 m, p = 0.02), midseason (-0.10 ± 0.04 m, p = 0.002), and late-season (-0.15 ± 0.04 m, p < 0.001) relative to the preseason. Reductions in CMJ variables from preseason to in-season ranged from trivial to large. Changes in countermovement depth differed for forwards and defensemen by the season phase (p = 0.04). A professional ice hockey season decreases CMJ performance, with the effects of fatigue most prominent during the late-season phase. Countermovement depth was most sensitive to fatigue and differentiated positional-group responses. Frequent CMJ testing is useful for identifying the neuromuscular status of team-sport athletes relative to season-specific phases. Fatigue monitoring should incorporate movement-strategy variables alongside traditional measures of performance and kinematics.

Strength and Power Development in Professional Rugby Union Players Over a Training and Playing Season.

PURPOSE: To investigate strength and power development in elite rugby players during the different phases of a professional season. METHODS: Sixteen professional rugby union athletes from an English premiership team were monitored for measures of lower-body peak force, force at 50 ms, force at 100 ms (all isometric squat), and power (explosive hack squat). Athletes were assessed at the start of preseason (T1), postpreseason (T2), midway through the competitive season (T3), and at the end of the competitive season (T4). Effect-size (ES) statistics with magnitude-based inferences were calculated to interpret differences in physical performance between the different stages of the season. RESULTS: Very likely beneficial increases in force at 50 ms (+16%, ES = 0.75 ± 0.4) and 100 ms (+14%, ES = 0.63 ± 0.4) were observed between T1 and T2. A likely beneficial increase in power was observed between T2 and T3 (+4%, ES = 0.31 ± 0.2). Between T3 and T4, decreases in force at 50 ms (-6%, ES = -0.39 ± 0.3) and 100 ms (-9%, ES = -0.52 ± 0.4) occurred, while peak force and power were maintained. Over the full season (T1-T4) clear beneficial increases in all measures of strength and power were identified. CONCLUSIONS: Meaningful increases in strength and power can be achieved in professional English premiership rugby players over a full playing season. The greatest opportunity for strength and power development occurs during pre- to midseason phases, while these measures are maintained or decrease slightly during the latter stages of a season.

Is ventilatory efficiency (VE/VCO(2) slope) associated with right ventricular oxidative metabolism in patients with congestive heart failure?

BACKGROUND: The relationship between minute ventilation and the rate of CO2 elimination (VE/VCO2 slope) is associated with mortality in patients with congestive heart failure (CHF). The VE/VCO2 slope > or =34 denotes a poor prognosis and has been proposed to reflect abnormalities in pulmonary perfusion. AIMS: To study whether increased VE/VCO2 slope is associated with elevated right ventricular (RV) oxidative metabolism relative to the left ventricle (LV). METHODS: 21 patients with stable NYHA II-III CHF underwent symptom limited cardiopulmonary exercise testing. Dynamic [(11)C]acetate positron emission tomography (PET) was used to measure oxidative metabolism (k(mono)) of the LV and RV. Corrected RV oxidative metabolism (RVOx) was calculated as RV/LV k(mono) ratio. RESULTS: Peak VO2 was 16.2+/-4.1 ml/min/kg and the VE/VCO2 slope was 33.4+/-6.1. LV and RV k(mono) were 0.046+/-0.009 and 0.037+/-0.007 min(-1), respectively, with a RVOx of 0.83+/-0.17. There was a good correlation between RVOx and the VE/VCO2 slope (r=0.61, p=0.0034). RVOx was 0.77+/-0.16 in patients with a VE/VCO2 slope <34 and 0.93+/-0.16 in patients with VE/VCO2 slope > or =34 (p=0.047). CONCLUSION: RVOx correlates with VE/VCO2 slope in CHF patients. This supports the hypothesis that pulmonary vascular resistance is a determinant of the VE/VCO2 slope.