Can 3 mg·kg−1 of Caffeine Be Used as An Effective Nutritional Supplement to Enhance the Effects of Resistance Training in Rugby Union Players?

The present study uniquely examined the effect of 3 mg·kg−1 chronic caffeine consumption on training adaptations induced by 7-weeks resistance training and assessed the potential for habituation to caffeine’s ergogenicity. Thirty non-specifically resistance-trained university standard male rugby union players (age (years): 20 ± 2; height (cm): 181 ± 7; body mass (kg): 92 ± 17) completed the study), who were moderate habitual caffeine consumers (118 ± 110 mg), completed the study. Using a within-subject double-blind, placebo-controlled experimental design, the acute effects of caffeine intake on upper and lower limb maximal voluntary concentric and eccentric torque were measured using isokinetic dynamometry (IKD) prior to and immediately following a resistance training intervention. Participants were split into strength-matched groups and completed a resistance-training program for seven weeks, consuming either caffeine or a placebo before each session. Irrespective of group, acute caffeine consumption improved peak eccentric torque of the elbow extensors (p < 0.013), peak concentric torque of the elbow flexors (p < 0.005), total eccentric work of the elbow flexors (p < 0.003), total concentric work of the knee extensors (p < 0.001), and total concentric and eccentric work of the knee flexors (p < 0.046) following repeated maximal voluntary contractions. Many of these acute caffeine effects were still prevalent following chronic exposure to caffeine throughout the intervention. The training intervention resulted in significant improvements in upper and lower body one-repetition maximum strength (p < 0.001). For the most part, the effect of the training intervention was equivalent in both the caffeine and placebo groups, despite a small but significant increase (p < 0.037) in the total work performed in the participants that consumed caffeine across the course of the intervention. These results infer that caffeine may be beneficial to evoke acute improvements in muscular strength, with acute effects prevalent following chronic exposure to the experimental dose. However, individuals that consumed caffeine during the intervention did not elicit superior post-intervention training- induced adaptations in muscular strength.

Si può parlare di un’arte femminista queer?

Language "is a place of struggle," says bell hooks. The relationship between art and feminism is complex and stratified, for this reason the definition of "feminist art" is tricky. I attempt here a recognition of theoretical landmarks and epistemologies come forth in the debate that examined the intersection between artistic practices and experiments of feminist policies, from the historical speeches of Nochlin, Pollock, Phelan to the Italian anomaly marked by Carla Lonzi’s eccentric work, up to to the most recent openings. From this scheme, questions active at present appear, relating to the patriarchal myth of authorship, to the status of the work, to the invisibility of material processes and to cultural appropriation. The prospect is one of a thought of practices destabilizing the canon through strategies of decolonization, countercultural practices, "positional geographies" and new epistemologies.

Does Chronic Ankle Instability Influence Knee Biomechanics of Females during Inverted Surface Landings?

The primary purpose of the study was to determine whether atypical knee biomechanics are exhibited during landing on an inverted surface. A seven-camera motion analysis system and two force plates were used to collect lower extremity biomechanics from two groups of female participants: 21 subjects with chronic ankle instability (CAI) and 21 with pair-matched controls. Subjects performed ten landings onto inverted and flat platforms on the CAI/matched and non-test limbs, respectively. Knee and ankle joint angles, joint angular displacements, joint moments and eccentric work were calculated during the landing phase and/or at the initial contact. Paired t-tests were used to compare between-group differences (p<0.05). We observed that CAI group displayed a significantly increased knee flexion angle, knee flexion displacement, peak knee extension moment and internal rotation moment, and eccentric work in the sagittal plane, possibly due to altered ankle biomechanics. Participants with CAI employed some compensatory strategy to improve their ankle and postural stability during landing onto the tilted surface. The increased knee extension and internal rotation moments of CAI participants could potentially result in a greater ACL loading. In future studies, it may be worthwhile to measure or estimate the ACL loading to confirm whether CAI could relate to the mechanism of ACL injury.

Changes in Kinematics, Metabolic Cost, and External Work During Walking with a Forward Assistive Force

We examined how the application of a forward horizontal force applied at the waist alters the metabolic cost, kinematics, and external work of gait. Horizontal assist forces of 4%, 8% and 12% of a subject’s body weight were applied via our testing apparatus while subjects walked at comfortable walking speed on a level treadmill. Kinematic and metabolic parameters were measured using motion capture and ergospirometry respectively on a group of 10 healthy male subjects. Changes in kinematic and metabolic parameters were quantified and found similar to walking downhill at varying grades. A horizontal assist force of 8% resulted in the greatest reduction of metabolic cost. Changes in recovery factor, external work, and center of mass (COM) movement did not correlate with changes in metabolic rate and therefore were not driving the observed reductions in cost. The assist force may have performed external work by providing propulsion as well as raising the COM as it pivots over the stance leg. Assist forces may decrease metabolic cost by reducing the concentric work required for propulsion while increasing the eccentric work of braking. These findings on the effects of assist forces suggest novel mobility aids for individuals with gait disorders and training strategies for athletes.

Changes of muscle-derived cytokines in relation to thiol redox status and reactive oxygen and nitrogen species

The aim of this study was to compare the levels of the plasma muscle-derived cytokines (myokines) and reactive oxygen and nitrogen species (RONS) after muscle damage triggered by different exercises, and to demonstrate the relationships between RONS, thiol redox status and myokines. Sixteen young men participated in a 90-min run at 65 % VO2max (Ex.1) or 90-min run at 65 % VO2max finished with a 15-min eccentric phase (Ex.2, downhill running). Plasma samples were collected before and at 20 min, 24 h and 48 h after exercise. The exercise trials significantly elevated the concentrations of plasma hydrogen peroxide (H2O2) and 8-isoprostane at 20 min rest. Myokines IL-6 and IL-10 increased at 20 min rest while IL-1β and TNFα increased at 24 h rest following both running. Ex.2 caused a significant increase in nitric oxide (NO), IL-6, IL-10 and oxidized glutathione (GSSG) levels. Thiol redox status (GSHtotal2GSSG/GSSG) decreased by about 30 % after Ex.2 as compared to Ex.1. H2O2 and NO directly correlated with IL-6, IL-10, IL-1β, TNFα and glutathione. These results show that eccentric work is an important factor that enhances the production of RONS and muscle-derived cytokines, and that there is a possible participation of thiol redox status in the release of myokines to blood.

Strength Profiles of Shoulder Rotators in Healthy Sport Climbers and Nonclimbers

Objective: To establish the isokinetic strength profiles and work ratios of the shoulder internal and external rotators in sport climbers and to compare them with these profiles and ratios in nonclimbers. We hypothesized that the strength profiles of the shoulder rotators were different between sport climbers and nonclimbers. Design: Cross-sectional study. Setting: Exercise science laboratory. Patients or Other Participants: Thirty-one experienced sport climbers and 27 nonclimbers. Main Outcome Measure(s): We tested all participants by measuring the isokinetic concentric and eccentric work output of their shoulder rotators in the middle 110° of shoulder rotation. We measured mean conventional work ratios of concentric external rotation (ER) to internal rotation (IR) (con ER:IR) and eccentric ER to IR (ecc ER:IR), and we measured mean functional work ratios of eccentric ER to concentric IR (ecc ER:con IR) and eccentric IR to concentric ER (ecc IR:con ER). Results: All work ratios were different between the 2 groups (P &lt; .001). In the climbers, the conventional work ratios were smaller than 1 for con ER:IR (0.79) and ecc ER:IR (0.88), whereas for the nonclimbers, the ratios were 1.03 and 1.13, respectively. The functional work ratio of ecc ER:con IR was smaller for the climbers (1.05) than for the nonclimbers (1.30), but the functional work ratio of ecc IR:con ER was larger for the climbers (1.58) than for the nonclimbers (1.17). Conclusions: The difference in work ratios of the shoulder rotators between participant groups might be due to training-induced changes in the shoulder rotation muscles of sport climbers. The clinical implication of this strength difference in shoulder IR and ER in climbers has yet to be examined.

Chronic eccentric exercise: improvements in muscle strength can occur with little demand for oxygen

Eccentric contractions, the lengthening of muscle while producing force, are a common part of our everyday movements. This study presents a challenge to the accepted notion that eccentric work causes obligatory muscle injury while demonstrating that an increase in muscle strength, via eccentric work, can occur with little demand for oxygen. Nine healthy subjects, ages 18–34, were randomly placed in either an eccentric or a concentric training group. Both groups trained for 6 wk while progressively increasing training frequency and duration. Significant gains in isometric leg strength were seen in the eccentrically trained subjects only. While training, the oxygen consumption required to do the eccentric work was equal to or less than that required to do the concentric work. The results demonstrate that by progressively increasing the eccentric work rate, significant isometric strength gains can be made without muscle injury and with minimal increase in metabolic demand for oxygen. The potential clinical implications of an eccentric training program that uncouples skeletal muscle strength improvements from the demand for oxygen are alluring.