Κυριακή, 8 Ιουλίου 2018

Correction to: The Effectiveness of Resisted Sled Training (RST) for Sprint Performance: A Systematic Review and Meta-analysis

Page 1: Abstract, Conclusions, sentence 4. The following sentence, which read:

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Abstract

Classification is a defining characteristic of para-sports whereby eligible athletes are allocated a sport class to compete against others with similar activity limitations. To account for the unique characteristics of each sport, para-sports should develop their own classification system using evidence that demonstrates the impact of impairment on performance in that sport. Although the move towards sport-specific classification has progressed in sports for athletes with physical and intellectual impairments, sports for athletes with vision impairment (VI) continue to use the same three classes irrespective of the sport, with classes delineated by legal definitions of low vision and blindness. The aim of this joint International Paralympic Committee/International Blind Sports Federation (IPC/IBSA) Position Stand is to provide guidance for how evidence-based sport-specific classification should be achieved in VI sports. It does so by outlining three conceptual research models (correlation, simulation, and component analysis) that can be used to establish both the minimum impairment required to compete plus the appropriate number of sport classes and their inclusion criteria. The present evaluation of vision relies on measures of visual acuity and field, but new criteria may require a sport-specific combination of additional measures of visual function (e.g. contrast, motion, and light sensitivity) to better account for the impact of VI on sport performance. Moreover, the test procedures used during athlete evaluation (e.g. whether to evaluate both eyes individually or together) should be chosen to better represent the habitual viewing situation experienced in that sport. The development of sport-specific criteria should enhance the legitimacy of competition and encourage increased grassroots participation in VI sports.

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Purpose

Cold-induced vasodilatation (CIVD) is a peripheral blood flow response, observed in both the hands and feet. Exercise has been shown to enhance the response, specifically by increasing mean skin temperatures (Tsk), in part due to the increased number of CIVD waves. In contrast, hypobaric hypoxia has been suggested to impair digit skin temperature responses, particularly during subsequent hand rewarming following the cold stimulus. This study examined the combined effect of exercise and hypobaric hypoxia on the CIVD response. We compared the CIVD responses in the digits of both the hands and feet of a team of alpinists (N = 5) before and after a 35-day Himalayan expedition to Broadpeak, Pakistan (8051 m).

Methods

Five elite alpinists participated in hand and foot cold water immersion tests 20 days before and immediately upon return from their expedition.

Results

The alpinists summited successfully without supplemental oxygen. Post-expedition, all alpinists demonstrated higher minimum Tsk in their hands (pre: 9.9 ± 1.1, post: 10.1 ± 0.7 °C, p = 0.031). Four alpinists had either greater CIVD waves, and, consequently, higher mean Tsk in their hands, or higher recovery temperatures (pre: 26.0 ± 5.5 °C post: 31.0 ± 4.1 °C, p = 0.052), or faster rewarming rate (pre: 2.6 ± 0.5 °C min−1 post: 3.1 ± 0.4 °C min−1,p = 0.052). In the feet, the responses varied: 1/5 had higher wave amplitudes and 1/5 had higher passive recovery temperatures, whereas 3/5 had lower mean toe temperatures during cold exposure.

Conclusions

The results of the cold stress test suggest after a 35-day Himalayan expedition, alpinists experienced a slight cold adaptation of the hands, but not the feet.

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Purpose

Exposure to hypoxia has been suggested to activate multiple adaptive pathways so that muscles are better able to maintain cellular energy homeostasis. However, there is limited research regarding the tissue specificity of this response. The aim of this study was to investigate the influence of tissue specificity on mitochondrial adaptations of rat skeletal and heart muscles after 4 weeks of normobaric hypoxia (FiO2: 0.10).

Methods

Twenty male Wistar rats were randomly assigned to either normobaric hypoxia or normoxia. Mitochondrial respiration was determined in permeabilised muscle fibres from left and right ventricles, soleus and extensorum digitorum longus (EDL). Citrate synthase activity and the relative abundance of proteins associated with mitochondrial biogenesis were also analysed.

Results

After hypoxia exposure, only the soleus and left ventricle (both predominantly oxidative) presented a greater maximal mass-specific respiration (+48 and +25%, p < 0.05) and mitochondrial-specific respiration (+75 and +28%, p < 0.05). Citrate synthase activity was higher in the EDL (0.63 ± 0.08 vs 0.41 ± 0.10 µmol min− 1 µg− 1) and lower in the soleus (0.65 ± 0.17 vs 0.87 ± 0.20 µmol min− 1 µg− 1) in hypoxia with respect to normoxia. There was a lower relative protein abundance of PGC-1α (25%, p < 0.05) in the right ventricle and a higher relative protein abundance of PGC-1β (+43%, p < 0.05) in the left ventricle of rats exposed to hypoxia, with few differences for protein abundance in the other muscles.

Conclusion

Our results show a muscle-specific response to 4 weeks of normobaric hypoxia. Depending on fibre type, and the presence of ventricular hypertrophy, muscles respond differently to the same degree of environmental hypoxia.

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Introduction

Exercise training is recommended for improving health and protecting against the development of metabolic and cardiovascular pathologies. Combined resistance and aerobic exercise training (CRAE) has been shown to provide unique benefits in older adults with cardiovascular diseases.

Purpose

We sought to determine the beneficial effects of CRAE in adolescent girls who are obese and hyperinsulinemic.

Methods

Forty adolescent girls who are obese (age 14.7 ± 1 years; BMI 30 ± 2) were randomly assigned to a "no exercise" (CON n = 20) or combined exercise group (EX n = 20). The EX group performed resistance and aerobic exercise for 12 weeks, 5 times per week. Exercise intensity was increased gradually, from 40 to 70% of heart rate reserve (HRR), every 4 weeks. The brachial-ankle pulse wave velocity (BaPWV), blood pressure (BP), heart rate (HR), blood leptin, adiponectin levels, and body composition were measured before and after the 12-week intervention.

Results

We observed that CRAE effectively reduced the body fat percentage, body weight, and waist circumference in the EX group (p < 0.05). After 12 weeks of training, subjects in the CRAE group maintained appropriate leptin and adiponectin levels and showed positive improvements of blood insulin, glucose, and insulin resistance parameters relative to baseline and to the CON group (p < 0.05).

Conclusion

CRAE is a useful therapeutic method to alleviate metabolic risk factors in adolescent girls who are obese and hyperinsulinemic.

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Purpose

This study aims to compare the isometric strength of hip abductors and external rotators in male athletes with and without patellar tendinopathy (PT), and to examine the correlation between hip strength, pain, and functional scores.

Methods

Sixty male athletes (30 with PT and 30 controls) were recruited from local volleyball and basketball teams. The isometric strength of the hip abductors and external rotators was quantified using a belt-stabilized handheld dynamometer. This study used the visual analog scale (VAS) and the Victorian Institute of Sport Assessment-Patella (VISA-p) questionnaire to measure the intensity of pain and functional scores in athletes with PT, respectively.

Results

The normalized isometric strength of the hip abductors and external rotators was significantly less in the PT group compared with controls. In subjects with PT, the normalized isometric strength was decreased by 22.0% (p = 0.000) in the hip abductors and by 20.0% in the hip external rotators (p = 0.004), compared with controls. Significant correlations were found between the normalized isometric strength of the hip abductors and intensity of pain (r = − 0.70; p < 0.05) and VISA-p score (r = 0.63; p < 0.05) in the affected leg in athletes with unilateral PT.

Conclusions

Athletes with PT have decreased isometric strength in their hip abductors and external rotators when compared with controls. In subjects with unilateral PT, decreased isometric strength in the hip abductors is associated with greater intensity of pain and lower functional scores. Results of this study implied that hip muscle assessment and strengthening should be included for reconditioning and rehabilitation in athletes with PT.

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Purpose

We have reported using near-infrared spectroscopy that an increase in prefrontal oxygenated-hemoglobin concentration (Oxy-Hb) at the start of cycling exercise has relation to central command, defined as a feedforward signal descending from higher brain centers. The final output of central command evokes the exercise effort-dependent cardiovascular responses. If the prefrontal cortex may output the final signal of central command toward the autonomic nervous system, the prefrontal oxygenation should increase depending on exercise effort. To test the hypothesis, we investigated the effects of exercise intensity and muscle mass on prefrontal oxygenation in 13 subjects.

Methods

The subjects performed one- or two-legged cycling at various relative intensities for 1 min. The prefrontal Oxy-Hb and cardiovascular variables were simultaneously measured during exercise.

Results

The increase in cardiac output and the decrease in total peripheral resistance at the start of one- and two-legged cycling were augmented in proportion to exercise intensity and muscle mass recruitment. The prefrontal Oxy-Hb increased at the start of voluntary cycling, while such increase was not developed during passive cycling. Mental imagery of cycling also increased the prefrontal Oxy-Hb, concomitantly with peripheral muscle vasodilatation. However, the increase in prefrontal Oxy-Hb at the start of voluntary cycling seemed independent of exercise intensity and muscle mass recruitment.

Conclusions

It is likely that the increased prefrontal activity at the start of cycling exercise is not representative of the final output signal of central command itself toward the autonomic nervous system but may trigger neuronal activity in the caudal brain responsible for the generation of central command.

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Purpose

Increased arterial stiffness is observed with ageing and in individuals with low cardiorespiratory fitness ( $$\dot {V}$$ O2peak), and associated with cardiovascular risk. Following an exercise bout, transient arterial stiffness reductions offer short-term benefit, but may depend on exercise intensity. This study assessed the effects of exercise intensity on post-exercise arterial stiffness in older adults with varying fitness levels.

Methods

Fifty-one older adults (72 ± 5 years) were stratified into fitness tertiles ( $$\dot {V}$$ O2peak: low-, 22.3 ± 3.1; mid-, 27.5 ± 2.4 and high-fit 36.3 ± 6.5 mL kg−1 min−1). In a randomised order, participants underwent control (no-exercise), moderate-intensity continuous exercise (40% of peak power output; PPO), and higher-intensity interval exercise (70% of PPO) protocols. Pulse wave velocity (PWV), augmentation index (AIx75) and reflection magnitude (RM) were assessed at rest and during 90 min of recovery following each protocol.

Results

After control, delta PWV increased over time (P < 0.001) and delta RM was unchanged. After higher-intensity interval exercise, delta PWV (P < 0.001) and delta RM (P < 0.001) were lower to control in all fitness groups. After moderate-intensity continuous exercise, delta PWV was not different from control in low-fit adults (P = 0.057), but was lower in the mid- and higher-fit older adults. Post-exercise AIx75 was higher to control in all fitness groups (P = 0.001).

Conclusions

In older adults, PWV increases during seated rest and this response is attenuated after higher-intensity interval exercise, regardless of fitness level. This attenuation was also observed after moderate-intensity continuous exercise in adults with higher, but not lower fitness levels. Submaximal exercise reveals differences in the arterial stiffness responses between older adults with higher and lower cardiorespiratory fitness.

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Introduction

Obesity and hypohydration independently affect postsynaptic endothelial function, but it is unknown if hypohydration affects lean and obese individuals differently.

Purpose

To examine the effect of hypohydration on postsynaptic cutaneous vasodilation and sweating in men with high and low adiposity (HI- and LO-BF, respectively).

Methods

Ten males with LO-BF and ten with HI-BF were instrumented for forearm microdialysis when euhydrated and hypohydrated. Changes in cutaneous vascular conductance (CVC) with intradermal infusion of sodium nitroprusside (SNP) and methacholine chloride (MCh) were assessed. Local sweat rate (LSR) was simultaneously assessed at the MCh site. At the end of the last dose, maximal CVC was elicited by delivering a maximal dose of SNP for 30 min to both sites with simultaneous local heating at the SNP site. The concentration of drug needed to elicit 50% of the maximal response (EC50) was compared between groups and hydration conditions.

Results

When euhydrated, EC50 of MCh-induced CVC was not different between LO- vs. HI-BF [− 3.04 ± 0.12 vs. − 2.98 ± 0.19 log (MCh) M, P = 0.841]. EC50 of SNP-induced CVC was higher in euhydrated HI- vs. LO-BF (− 1.74 ± 0.17 vs. − 2.13 ± 0.06 log (SNP) M, P = 0.034). Within each group, hydration status did not change MCh- or SNP-induced CVC (P > 0.05). LSR was not different between groups or hydration condition (P > 0.05).

Conclusions

These data suggest reduced sensitivity of endothelium-independent vasodilation in individuals with high adiposity when euhydrated. However, hypohydration does not affect cutaneous vasodilation or local sweat rate differently between individuals with low or high adiposity.

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Purpose

To determine whether stiffness of the patellar tendon and quadriceps muscles is altered immediately after and 48 h after a single bout of maximal eccentric exercise of the knee extensor muscles.

Methods

Thirteen healthy individuals [group mean (SD) age 22.4 (3.5) years; 7 female] performed a single bout of maximal eccentric exercise of the non-dominant knee extensors, using an isokinetic dynamometer. Shear-wave velocity (an index of tissue stiffness) was recorded from the patellar tendon, vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL), before, following (post0), and 48 h after (post48) exercise. To investigate features of exercise induced muscle damage, maximal voluntary isometric contraction (MVIC) and self-reported pain and stiffness (numerical rating scales 0 = no pain/stiffness to 100 = worst imaginable pain/stiffness) were measured before, post0, and post48 exercise. Serum creatine kinase (CK) was measured before and post48 exercise.

Results

Compared to preexercise, MVIC decreased and self-reported pain and stiffness increased at post0 and post48 and CK levels increased at post48 (all p < 0.01). Compared to preexercise, shear-wave velocity was greater at post0 for the patellar tendon [15.9 (24.6)%, p = 0.01] and RF [23.6 (16.7)%, p < 0.001], each returning to baseline by post48. No significant differences were observed for VL or VM post0 or post48 exercise.

Conclusion

Maximal eccentric exercise produced an immediate increase in the stiffness of the patellar tendon and RF, resolving by 48 h. As this change was not observed in VL and VM, future studies may explore heterogeneity within synergist muscles following eccentric exercise.

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Decreased occipital alpha oscillation in children who stutter during a visual Go/Nogo task

Publication date: Available online 7 July 2018

Source: Clinical Neurophysiology

Author(s): Johanna Piispala, Tuomo Starck, Eira Jansson-Verkasalo, Mika Kallio

Abstract
Objective

Our goal was to discover attention- and inhibitory control- related differences in the main oscillations of the brain of children who stutter (CWS) compared to typically developed children (TDC).

Methods

We performed a time-frequency analysis using wavelets, fast Fourier transformation (FFT) and the Alpha/Theta power ratio of EEG data collected during a visual Go/Nogo task in 7-9 year old CWS and TDC, including also the time window between consecutive tasks.

Results

CWS showed significantly reduced occipital alpha power and Alpha/Theta ratio in the "resting" or preparatory period between visual stimuli especially in the Nogo condition.

Conclusions

The CWS demonstrate reduced inhibition of the visual cortex and information processing in the absence of visual stimuli, which may be related to problems in attentional gating.

Significance

Occipital alpha oscillation is elementary in the control and inhibition of visual attention and the lack of occipital alpha modulation indicate fundamental differences in the regulation of visual information processing in CWS. Our findings support the view of stuttering as part of a wide-ranging brain dysfunction most likely involving also attentional and inhibitory networks.

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