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The impact of beetroot juice supplementation on muscular endurance, maximal strength and countermovement jump performance.
Jonvik, KL, Hoogervorst, D, Peelen, HB, de Niet, M, Verdijk, LB, van Loon, LJC, van Dijk, JW
European journal of sport science. 2021;(6):871-878
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Abstract
Purpose: Dietary nitrate has been shown to enhance muscle contractile function and has, therefore, been linked to increased muscle power and sprint exercise performance. However, the impact of dietary nitrate supplementation on maximal strength, performance and muscular endurance remains to be established. Methods: Fifteen recreationally active males (25 ± 4 y, BMI 24 ± 3 kg/m2) participated in a randomized double-blinded cross-over study comprising two 6-d supplementation periods; 140 mL/d nitrate-rich (BR; 985 mg/d) and nitrate-depleted (PLA; 0.37 mg/d) beetroot juice. Three hours following the last supplement, we assessed countermovement jump (CMJ) performance, maximal strength and power of the upper leg by voluntary isometric (30° and 60° angle) and isokinetic contractions (60, 120, 180 and 300°·s-1), and muscular endurance (total workload) by 30 reciprocal isokinetic voluntary contractions at 180°·s-1. Results: Despite differences in plasma nitrate (BR: 879 ± 239 vs. PLA: 33 ± 13 μmol/L, P < 0.001) and nitrite (BR: 463 ± 217 vs. PLA: 176 ± 50 nmol/L, P < 0.001) concentrations prior to exercise testing, CMJ height (BR: 39.3 ± 6.3 vs. PLA: 39.6 ± 6.3 cm; P = 0.39) and muscular endurance (BR: 3.93 ± 0.69 vs. PLA: 3.90 ± 0.66 kJ; P = 0.74) were not different between treatments. In line, isometric strength (P > 0.50 for both angles) and isokinetic knee extension power (P > 0.33 for all velocities) did not differ between treatments. Isokinetic knee flexion power was significantly higher following BR compared with PLA ingestion at 60°·s-1 (P = 0.001), but not at 120°·s-1 (P = 0.24), 180°·s-1 (P = 0.066), and 300°·s-1 (P = 0.36). Conclusion: Nitrate supplementation does not improve maximal strength, countermovement jump performance and muscular endurance in healthy, active males.
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Brain Motor Control Assessment Post Early Intensive Hand Rehabilitation After Spinal Cord Injury.
Zoghi, M, Galea, M
Topics in spinal cord injury rehabilitation. 2018;(2):157-166
Abstract
Background: The Brain Motor Control Assessment (BMCA) is a surface electromyography (sEMG)-based measure of motor output from the central nervous system during a variety of reflex and voluntary motor tasks. Objective: The aim of this study was to assess the pattern of voluntary movements in patients with spinal cord injury (SCI) to investigate whether BMCA could add more resolution to clinical assessments and the recovery path of these patients. Method: Ten participants were recruited from the Royal Talbot Rehabilitation Centre as part of a multicenter randomized controlled trial. Four participants received usual care while the other 3 participants received usual care plus an intensive task-specific hand training program in conjunction with functional electrical stimulation for 8 weeks. BMCA assessments were completed for 7 participants at this center 4 times over a period of 1 year. Results: Generalized linear model analysis showed a significant main effect of task (p < .001) and assessment time (p = .003) on the Similarity Index. However, there were no significant interactions among the factors (p > .05). Based on ARAT or summed upper limb strength scores, some participants showed significant improvement after 8 weeks of rehabilitation, however this improvement was not reflected in the pattern of muscle activation that was captured by BMCA. Conclusion: The quantifiable features of BMCA through surface EMG may increase the resolution of SCI characterization by adding subclinical details to the clinical picture of lesion severity and progression during rehabilitation.
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Task errors contribute to implicit aftereffects in sensorimotor adaptation.
Leow, LA, Marinovic, W, de Rugy, A, Carroll, TJ
The European journal of neuroscience. 2018;(11):3397-3409
Abstract
Perturbations of sensory feedback evoke sensory prediction errors (discrepancies between predicted and actual sensory outcomes of movements), and reward prediction errors (discrepancies between predicted rewards and actual rewards). When our task is to hit a target, we expect to succeed in hitting the target, and so we experience a reward prediction error if the perturbation causes us to miss it. These discrepancies between intended task outcomes and actual task outcomes, termed "task errors," are thought to drive the use of strategic processes to restore success, although their role is incompletely understood. Here, as participants adapted to a 30° rotation of cursor feedback representing hand position, we investigated the role of task errors in sensorimotor adaptation: during target-reaching, we either removed task errors by moving the target mid-movement to align with cursor feedback of hand position, or enforced task error by moving the target away from the cursor feedback of hand position, by 20-30° randomly (clockwise in half the trials, counterclockwise in half the trials). Removing task errors not only reduced the extent of adaptation during exposure to the perturbation, but also reduced the amount of post-adaptation aftereffects that persisted despite explicit knowledge of the perturbation removal. Hence, task errors contribute to implicit adaptation resulting from sensory prediction errors. This suggests that the system which predicts the sensory consequences of actions via exposure to sensory prediction errors is also sensitive to reward prediction errors.
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Physiological responses to different neuromuscular movement task during eccentric bench press.
Wilk, M, Stastny, P, Golas, A, Nawrocka, M, Jelen, K, Zajac, A, Tufano, JJ
Neuro endocrinology letters. 2018;(1):26-32
Abstract
OBJECTIVES Increasing muscular hypertrophy is one of the main reasons for participating in a resistance training program, where different movement task such as eccentric cadences may serve as a potent hypertrophic stimulus and improve movement stability. Aim of this study was to investigate the physiological responses between slow 6/0/2/0 (SLOW) and moderate 2/0/2/0 (REG) eccentric cadences during five sets of bench press to failure using 70% 1 repetition maximum (1RM). MATERIALS AND METHODS Blood samples from sixteen men (21-29y, 85.9±7.7kg, 130±17.5kg bench press 1RM) with at least five years of resistance training experience were taken before, immediately after, 30 min after, and 60 min after both protocols in a randomized cross over study design. RESULTS ANOVA showed that more repetitions were performed during each set in REG and for the entire REG protocol (p<0.001), but total time under tension was greater during SLOW in each set and for the entire protocol (p<0.001). The post-exercise levels of lactate (p=0.02), creatine kinase (p=0.04), and testosterone (p=0.01) were greater after SLOW. Post-exercise cortisol levels decreased in both protocols (p<0.001), but these decreases were not significantly different between protocols. CONCLUSIONS Therefore, intentionally slow eccentric speeds and increased eccentric time under tension seem to be effective for increasing acute hormonal responses after exercise. As such, although a SLOW tempo may decrease the amount of total work (i.e. fewer repetitions with the same load), the increased time under tension seems to drive hormonal responses and neurological response, which may play a large role in stimulating muscle growth, coordination and movement stability.
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The utility of bispectral index monitoring for prevention of rocuronium-induced withdrawal movement in children: A randomized controlled trial.
Lim, BG, Lee, IO, Kim, YS, Won, YJ, Kim, H, Kong, MH
Medicine. 2017;(2):e5871
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Abstract
BACKGROUND This study was designed to determine whether a deep hypnotic state with a bispectral index (BIS) value less than 40 could alleviate withdrawal movement (WM) upon rocuronium injection during anesthesia induction in children. METHODS Finally, 135 healthy children (3-12 years) scheduled for minor elective surgery were studied. Without premedication, anesthesia was induced with thiopental sodium 5 mg/kg. Patients were randomized into 2 groups (control vs experimental) and then by virtue of rocuronium injection time, patients in the experimental group were allocated into 2 groups, as follows: in the control group (group C; n = 45), rocuronium 0.6 mg/kg was administered at the loss of eyelash reflex; in the 1st experimental group, rocuronium 0.6 mg/kg was administered when BIS fell to less than 40 (group T; n = 45); however, if BIS did not fall below 40 after thiopental sodium administration, manual ventilation was provided with oxygen 6 L/minute using sevoflurane 8% and then rocuronium was administered when BIS fell below 40 (the 2nd experimental group, group S; n = 45). Rocuronium-induced WM was evaluated using a 4-point scale (no movement; movement/withdrawal involving the arm only; generalized response, with movement/withdrawal of more than 1 extremity, but no requirement for restraint of the body; and generalized response which required restraint of the body and caused coughing or breath-holding). RESULTS No significant differences were found among the groups for patient characteristics including age, sex, height, and location of venous cannula. However, body weight, height, and body mass index in group S were all smaller than those in group T. The incidence of WM caused by rocuronium was 100% in group C, 95.6% in group T, and 80% in group S, and was significantly lower in group S than in group C. The grade of WM was 3.7 ± 0.6 in group C, 3.2 ± 0.9 in group T, and 2.6 ± 1.0 in group S. It was significantly lower in group T than in group C and significantly lower in group S than in groups C and T. CONCLUSION The confirmation of a deep hypnotic state with BIS values lower than 40 using BIS monitoring can reduce the grade of rocuronium-induced WMs during anesthesia induction using thiopental sodium or sevoflurane in children.
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Accuracy of a combined heart rate and motion sensor for assessing energy expenditure in free-living adults during a double-blind crossover caffeine trial using doubly labeled water as the reference method.
Silva, AM, Santos, DA, Matias, CN, Júdice, PB, Magalhães, JP, Ekelund, U, Sardinha, LB
European journal of clinical nutrition. 2015;(1):20-7
Abstract
BACKGROUND/OBJECTIVES A combined heart rate (HR) and motion sensor (Actiheart) has been proposed as an accurate method for assessing total energy expenditure (TEE) and physical activity energy expenditure (PAEE). However, the extent to which factors such as caffeine may affect the accuracy by which the estimated HR-related PAEE contribution will affect TEE and PAEE estimates is unknown. Therefore, we examined the validity of Actiheart in estimating TEE and PAEE in free-living adults under a caffeine trial compared with doubly labeled water (DLW) as reference criterion. SUBJECTS/METHODS Using a double-blind crossover trial (Clinicaltrials.gov ID: #NCT01477294) with two conditions (4-day each with a 3-day-washout period), randomly ordered as caffeine (5 mg/kg per day) and placebo (malt-dextrine) intake, TEE was measured by DLW in 17 physically active men (20-38 years) who were non-caffeine users. In each condition, resting energy expenditure (REE) was assessed by indirect calorimetry and PAEE was calculated as (TEE-(REE+0.1 TEE)). Simultaneously, PAEE and TEE were estimated by Actiheart using an individual calibration (ACC+HRstep). RESULTS Under caffeine, ACC+HRstep explained 76 and 64% of TEE and PAEE from DLW, respectively; corresponding results for the placebo condition were 82 and 66%. No mean bias was found between ACC+HRstep and DLW for TEE (caffeine:-468 kJ per day; placebo:-407 kJ per day), although PAEE was slightly underestimated (caffeine:-856 kJ per day; placebo:-1147 kJ per day). Similar limits of agreement were observed in both conditions ranging from -2066 to 3002 and from -3488 to 1776 kJ per day for TEE and PAEE, respectively. CONCLUSIONS Regardless of caffeine intake, the combined HR and motion sensor is valid for estimating free-living energy expenditure in a group of healthy men but is less accurate for an individual assessment.
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Comparison of randomized preemptive dexketoprofen trometamol or placebo tablets to prevent withdrawal movement caused by rocuronium injection.
Aydın, GB, Polat, R, Ergil, J, Sayın, M, Caparlar, CO
Journal of anesthesia. 2014;(3):471-4
Abstract
Rocuronium is a non-depolarizing neuromuscular blocking agent which is associated with injection pain and induces withdrawal movement of the injected hand or arm or generalized movements of the body after intravenous injection. The aim of this randomized study was to compare the efficacy of pretreatment with oral dexketoprofen trometamol (Arvelles(®); Group A) with placebo (Group P) without tourniquet to prevent the withdrawal response caused by rocuronium injection. The study cohort comprised 150 American Society of Anaesthesiologists class I-III patients aged 18-75 years who were scheduled to undergo elective surgery with general anesthesia. The patients response to rocuronium was graded using a 4-point scale [0 = no response; 1 = movement/withdrawal at the wrist only, 2 = movement/withdrawal involving the arm only (elbow/shoulder); 3 = generalized response]. The overall incidence of withdrawal movement after rocuronium injection was significantly lower in Group A (30.1 %) than in Group P (64.6 %) (p < 0.001). The incidence of score 0 withdrawal movements was higher in Group A (69.9 %) than in Group P (35.4 %), that of score 1 withdrawal movements was similar between groups (Group A 21.9 %; Group B 26.1 %) (p = 0.560) and that of score 2 withdrawal movements was lower in Group A (8.2 %) than in Group P (38.5 %) (p < 0.001). There were no score 3 withdrawal movements in either group (p > 0.05). These results demonstrate that the preemptive administration of dexketoprofen trometamol can attenuate the degree of withdrawal movements caused by the pain of the rocuronium injection.
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Predicting punching acceleration from selected strength and power variables in elite karate athletes: a multiple regression analysis.
Loturco, I, Artioli, GG, Kobal, R, Gil, S, Franchini, E
Journal of strength and conditioning research. 2014;(7):1826-32
Abstract
This study investigated the relationship between punching acceleration and selected strength and power variables in 19 professional karate athletes from the Brazilian National Team (9 men and 10 women; age, 23 ± 3 years; height, 1.71 ± 0.09 m; and body mass [BM], 67.34 ± 13.44 kg). Punching acceleration was assessed under 4 different conditions in a randomized order: (a) fixed distance aiming to attain maximum speed (FS), (b) fixed distance aiming to attain maximum impact (FI), (c) self-selected distance aiming to attain maximum speed, and (d) self-selected distance aiming to attain maximum impact. The selected strength and power variables were as follows: maximal dynamic strength in bench press and squat-machine, squat and countermovement jump height, mean propulsive power in bench throw and jump squat, and mean propulsive velocity in jump squat with 40% of BM. Upper- and lower-body power and maximal dynamic strength variables were positively correlated to punch acceleration in all conditions. Multiple regression analysis also revealed predictive variables: relative mean propulsive power in squat jump (W·kg-1), and maximal dynamic strength 1 repetition maximum in both bench press and squat-machine exercises. An impact-oriented instruction and a self-selected distance to start the movement seem to be crucial to reach the highest acceleration during punching execution. This investigation, while demonstrating strong correlations between punching acceleration and strength-power variables, also provides important information for coaches, especially for designing better training strategies to improve punching speed.
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Power output in vertical jumps: does optimum loading depend on activity profiles?
Pazin, N, Berjan, B, Nedeljkovic, A, Markovic, G, Jaric, S
European journal of applied physiology. 2013;(3):577-89
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Abstract
The previously proposed maximum dynamic output hypothesis (MDO: i.e. the optimum load for maximizing the power output during jumping is one's own body) was tested on individuals of various activity profiles. Forty males (10 strength-trained athletes, 10 speed-trained athletes, 10 physically active non-athletes, and 10 sedentary individuals) performed different vertical jumps on a force plate while a pulley system was used to either reduce or increase the subject's body weight by 10-30 %. As expected, an increase in external loading resulted in a significant increase (p < 0.001) in force output and a concomitant decrease of peak jumping velocity in all groups of participants. The main finding, however, was that all groups revealed the maximum peak and mean power output at approximately the subjects' own body weight although their weight represented prominently different percentage of their maximum dynamic strength. While a significant (p < 0.05), albeit moderate, 'group × load' interaction in one jump was observed for the peak power output, the individual optimum load for maximizing the power output number did not differ among the groups. Although apparently further research on various types of movements is needed, the present results provide, so far, the strongest support of the MDO hypothesis.
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Effects of three-monthly oral 150,000 IU cholecalciferol supplementation on falls, mobility, and muscle strength in older postmenopausal women: a randomized controlled trial.
Glendenning, P, Zhu, K, Inderjeeth, C, Howat, P, Lewis, JR, Prince, RL
Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research. 2012;(1):170-6
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Abstract
Daily vitamin D in addition to calcium supplementation reduces falls and fractures in older women. However, poor adherence to therapy is a common clinical problem. To examine the effects of supervised oral 3-monthly vitamin D therapy on falls, muscle strength, and mobility, we conducted a 9-month randomized, double-blind, placebo-controlled trial in 686 community-dwelling ambulant women aged over 70 years. Participants received either oral cholecalciferol 150,000 IU every 3 months (n = 353) or an identical placebo (n = 333). All participants were advised to increase dietary calcium intake. Falls data were collected 3-monthly. At baseline, 3, 6, and 9 months, muscle strength was measured by a handheld dynamometer and mobility by the Timed Up and Go (TUG) test. Serum 25 hydroxyvitamin D (25OHD) was measured in a subgroup of 40 subjects. Mean age at baseline was 76.7 ± 4.1 years. The average serum 25OHD value at baseline was 65.8 ± 22.7 nmol/L. By 3, 6, and 9 months after supplementation, 25OHD levels of the vitamin D group were approximately 15 nmol/L higher than the placebo group. Calcium intake did not change significantly between baseline (864 ± 412 mg/day) and 9 months (855 ± 357 mg/day). Faller rates in the two groups did not differ: vitamin D group, 102 of 353 (29%); placebo group, 89 of 333 (27%). At 9 months, compared to placebo or baseline, muscle strength, and TUG were not altered by vitamin D. In conclusion, oral cholecalciferol 150,000 IU therapy administered 3-monthly had neither beneficial nor adverse effects on falls or physical function. These data together with previous findings confirm that intermittent large doses of vitamin D are ineffective or have a deleterious effect on falls. Thus despite adherence issues with daily vitamin D replacement, an intermittent, high-dose vitamin D regimen cannot be supported as a strategy to reduce falls and fractures.