The acute effects of a low and high dose of oral l-arginine supplementation in young active males at rest

2011 ◽  
Vol 36 (3) ◽  
pp. 405-411 ◽  
Author(s):  
Scott C. Forbes ◽  
Gordon J. Bell
Keyword(s):  
Body Mass ◽  
Repeated Measures ◽  
Plasma Concentrations ◽  
Insulin Response ◽  
High Dose ◽  
Placebo Condition ◽  
Double Blind ◽  
Physically Active ◽  
Significant Difference ◽  
Arginine Supplementation

l-arginine (2-amino-5-guanidinovaleric acid) is a conditionally essential amino acid. Intravenous (IV) administration of l-arginine invokes a large metabolic (nitrate/nitrite (NOx)) and hormonal (growth hormone (GH), insulin-like growth factor 1 (IGF-1), and insulin) response; however, research examining oral l-arginine supplementation is conflicting, potentially owing to dose. The purpose of this study was examine a low and high dose of oral l-arginine on blood l-arginine, NOx, GH, IGF-1, and insulin response. Fourteen physically active males (age: 25 ± 5 years; weight: 78.0 ± 8.5 kg; height: 179.4 ± 4.7 cm) volunteered to be in a randomized, double-blind, repeated-measures study. Following an overnight fast, an IV catheter was placed in a forearm vein and a resting blood sample was drawn at ∼0800 hours. Each subject was then provided 1 of 3 treatment conditions (placebo, low (0.075 g·kg–1 of body mass), or high (0.15 g·kg–1 of body mass of l-arginine)). Blood samples were drawn at 30, 60, 90, 120, and 180 min after consumption. l-arginine plasma concentrations significantly increased (p < 0.001) to a similar level at any time point in both the low- and high-dose conditions; there was no change over time in the placebo condition. There was no significant difference between conditions for NOx, GH, IGF-1, or insulin. Based on these findings, a low dose of l-arginine was just as effective at increasing plasma l-arginine concentrations as a high dose; however, neither dose was able to promote a significant increase in NOx, GH, IGF-1, or insulin at rest.

scholarly journals The Effects of High Doses of Caffeine on Maximal Strength and Muscular Endurance in Athletes Habituated to Caffeine

Nutrients ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1912 ◽  
Author(s):  
Michal Wilk ◽  
Michal Krzysztofik ◽  
Aleksandra Filip ◽  
Adam Zajac ◽  
Juan Del Coso
Keyword(s):  
Body Mass ◽  
Repeated Measures ◽  
Bench Press ◽  
Muscle Endurance ◽  
Experimental Session ◽  
Maximal Strength ◽  
Double Blind ◽  
Significant Difference ◽  
Endurance Tests ◽  
Double Blind Design

Background: The main goal of this study was to assess the acute effects of the intake of 9 and 11 mg/kg/ body mass (b.m.) of caffeine (CAF) on maximal strength and muscle endurance in athletes habituated to caffeine. Methods: The study included 16 healthy strength-trained male athletes (age = 24.2 ± 4.2 years, body mass = 79.5 ± 8.5 kg, body mass index (BMI) = 24.5 ± 1.9, bench press 1RM = 118.3 ± 14.5 kg). All participants were habitual caffeine consumers (4.9 ± 1.1 mg/kg/b.m., 411 ± 136 mg of caffeine per day). This study had a randomized, crossover, double-blind design, where each participant performed three experimental sessions after ingesting either a placebo (PLAC) or 9 mg/kg/b.m. (CAF-9) and 11 mg/kg/b.m. (CAF-11) of caffeine. In each experimental session, participants underwent a 1RM strength test and a muscle endurance test in the bench press exercise at 50% 1RM while power output and bar velocity were measured in each test. Results: A one-way repeated measures ANOVA revealed a significant difference between PLAC, CAF-9, and CAF-11 groups in peak velocity (PV) (p = 0.04). Post-hoc tests showed a significant decrease for PV (p = 0.04) in the CAF-11 compared to the PLAC group. No other changes were found in the 1RM or muscle endurance tests with the ingestion of caffeine. Conclusion: The results of the present study indicate that high acute doses of CAF (9 and 11 mg/kg/b.m.) did not improve muscle strength nor muscle endurance in athletes habituated to this substance.

Solumedrol Treatment for Severe Sepsis in Humans with a Blunted Adrenocorticotropic Hormone-Cortisol Response: A Prospective Randomized Double-Blind Placebo-Controlled Pilot Clinical Trial

2021 ◽  
pp. 088506662110388
Author(s):  
Divya Birudaraju ◽  
Sajad Hamal ◽  
John A. Tayek
Keyword(s):  
Blood Pressure ◽  
Clinical Trial ◽  
Adrenocorticotropic Hormone ◽  
Serum Cortisol ◽  
High Dose ◽  
Cortisol Response ◽  
Acth Stimulation ◽  
Double Blind ◽  
Significant Difference ◽  
To Receive

Purpose To test the benefits of Solumedrol treatment in sepsis patients with a blunted adrenocorticotropic hormone (ACTH)-cortisol response (delta <13 µg/dL) with regard to the number of days on ventilator, days on intravenous blood pressure support, length of time in an intensive care unit (ICU), 14-day mortality, and 28-day mortality. The trial was prospective, randomized, and double-blind. As part of a larger sepsis trial, 54 patients with sepsis had an intravenous ACTH stimulation test using 250 µg of ACTH, and serum cortisol was measured at times 0, 30, and 60 min. Eleven patients failed to increase their cortisol concentration above 19.9 µg/dL and were excluded from the clinical trial as they were considered to have adrenal insufficiency. The remaining 43 patients had a baseline cortisol of 32 ± 1 µg/dL increased to 38 ± 3 µg/dL at 30 min and 40 ± 3 at 60 min. All cortisol responses were <12.9 µg/dL between time 0 and time 60, which is defined as a blunted cortisol response to intravenous ACTH administration. Twenty-one were randomized to receive 20 mg of intravenous Solumedrol and 22 were randomized to receive a matching placebo every 8 h for 7-days. There was no significant difference between the two randomized groups. Data analysis was carried out bya two-tailed test and P < .05 as significant. Results Results: The mean age was 51 ± 2 (mean ± SEM) with 61% female. Groups were well matched with regard to APACHE III score in Solumedrol versus placebo (59 ± 6 vs 59 ± 6), white blood cell count (18.8 ± 2.2 vs 18.6 ± 2.6), and incidence of bacteremia (29 vs 39%). The 28-day mortality rate was reduced in the Solumedrol treated arm (43 ± 11 vs 73 ± 10%; P < .05). There was no change in days in ICU, days on blood pressure agents, or days on ventilator. Seven days of high-dose intravenous Solumedrol treatment (20 mg every 8 h) in patients with a blunted cortisol response to ACTH was associated with an improved 28-day survival. This small study suggests that an inability to increase endogenous cortisol production in patients with sepsis who are then provided steroid treatment could improve survival.

scholarly journals Evaluation of the Effects of 660-nm and 810-nm Low-Level Diode Lasers on the Treatment of Dentin Hypersensitivity

2020 ◽  
Vol 11 (2) ◽  
pp. 126-134
Author(s):  
Narges Naghsh ◽  
Mahdi Kachuie ◽  
Marzie Kachuie ◽  
Reza Birang
Keyword(s):  
Diode Laser ◽  
Repeated Measures ◽  
Diode Lasers ◽  
Tooth Surface ◽  
Control Group ◽  
Dentin Hypersensitivity ◽  
Double Blind ◽  
Group I ◽  
Significant Difference ◽  
Laser Group

Introduction: Dentin hypersensitivity is a common oral problem that occurs as a short and sharp pain. There are many techniques to treat this condition, the latest of which is laser treatment. The aim of this study was to evaluate the effect of two types of low-power diode lasers (660 nm and 810 nm) on dentin hypersensitivity in order to achieve an acceptable clinical application by adjusting the effective parameters. Methods: In this randomized, double-blind clinical trial, sensitive teeth of 7 patients were divided into three groups with a randomized matching method: group I, treated with 660-nm diode laser irradiation, group II, treated with diode laser 810-nm, and group III, the control group. Irradiation parameters for 660-nm and 810-nm diode lasers were the power of 30 mW and 100 mW respectively, in contact and continuous modes, perpendicular to the tooth surface with a sweeping motion. Treatments were carried out in four sessions at weekly intervals. The data obtained were analyzed with SPSS 22, using one-way repeated measures ANOVA and the LSD (least significant difference) test. The significance level was considered as P≤0.05. Results: There were no significant differences in visual analogue scale (VAS) score changes between the two laser groups after the intervention in the first, second and third weeks compared to the baseline (P>0.05). These changes in the fourth week were significantly higher in the 810-nm laser group compared to the 660-nm laser group (P=0.04), and in the 660-nm laser group, they were more than the control group (P=0.02). The mean VAS scores at 1-week, 1-month and 2-month postoperative intervals were significantly lower in the 810-nm laser group than in the 660-nm laser group, and in the 660-nm laser group, they were less than the control group (P<0.001). Conclusion: The use of 660-nm and 810-nm diode lasers with the power of 30 and 100 mW respectively for 120 seconds was effective in reducing pain in patients with dentin hypersensitivity. However, the effect of the 810-nm laser on reducing the dentin hypersensitivity was more long-lasting than that of the 660-nm laser.

scholarly journals Clopidogrel Pharmacokinetics in Malaysian Population Groups: The Impact of Inter-Ethnic Variability

2018 ◽  
Vol 11 (3) ◽  
pp. 74 ◽  
Author(s):  
Zaril Zakaria ◽  
Alan Fong ◽  
Raj Badhan
Keyword(s):  
Plasma Concentration ◽  
Plasma Concentrations ◽  
High Dose ◽  
Population Groups ◽  
Adjunct Treatment ◽  
Malaysian Population ◽  
Significant Difference ◽  
Target Plasma Concentration ◽  
Ethnic Variability ◽  
The Impact

Malaysia is a multi-ethnic society whereby the impact of pharmacogenetic differences between ethnic groups may contribute significantly to variability in clinical therapy. One of the leading causes of mortality in Malaysia is cardiovascular disease (CVD), which accounts for up to 26% of all hospital deaths annually. Clopidogrel is used as an adjunct treatment in the secondary prevention of cardiovascular events. CYP2C19 plays an integral part in the metabolism of clopidogrel to the active metabolite clopi-H4. However, CYP2C19 genetic polymorphism, prominent in Malaysians, could influence target clopi-H4 plasma concentrations for clinical efficacy. This study addresses how inter-ethnicity variability within the Malaysian population impacts the attainment of clopi-H4 target plasma concentration under different CYP2C19 polymorphisms through pharmacokinetic (PK) modelling. We illustrated a statistically significant difference (P < 0.001) in the clopi-H4 Cmax between the extensive metabolisers (EM) and poor metabolisers (PM) phenotypes with either Malay or Malaysian Chinese population groups. Furthermore, the number of PM individuals with peak clopi-H4 concentrations below the minimum therapeutic level was partially recovered using a high-dose strategy (600 mg loading dose followed by a 150 mg maintenance dose), which resulted in an approximate 50% increase in subjects attaining the minimum clopi-H4 plasma concentration for a therapeutic effect.

scholarly journals Acute Arginine Supplementation Is Associated with Increased Growth Hormone in Younger Healthy Males: A Randomized Controlled Trial

2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 609-609
Author(s):  
John Apolzan ◽  
Jennifer Rood ◽  
Robbie Beyl ◽  
Shengping Yang ◽  
Frank Greenway ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Repeated Measures ◽  
Controlled Trial ◽  
Hormone Secretion ◽  
Growth Hormone Secretion ◽  
Sex Hormone Binding Globulin ◽  
Double Blind ◽  
Time Points ◽  
Arginine Supplementation ◽  
Time Point

Abstract Objectives Assess the effects of the amino acid arginine on growth hormone (GH), other metabolites, and mood. Arginine is reported to increase GH, but the mechanism is not known. It was hypothesized prolactin mediated this effect since it is similar in structure to GH and, like GH, is secreted by the pituitary gland. Methods Thirty physically active healthy young males (18–39 y; 18.5–25 kg/m2) were enrolled in a randomized, double-blind, placebo-controlled, crossover trial. Two days prior and 1 day following each treatment a standardized diet was provided that maintained arginine at 3–5 g/d. Arginine or placebo treatments in the form of a beverage were consumed after an overnight fast. Treatment conditions were separated by at least a one week washout period. The beverages contained either 10 g of arginine or 0 g (placebo). Blood was collected at baseline and 1.5, 3.0, and 24 hr post treatment. Plasma GH, prolactin, amino acids, glucose, insulin, triacylglycerols, thyroid hormones, sex hormone binding globulin (SHBG), testosterone, cortisol, and dehydroepiandrosterone (DHEA) were assessed. The Profile of Mood States (POMS) was administered at the same time as blood draws. Repeated measures ANOVAs were used to estimate treatment effects at each time point. Results Arginine increased plasma arginine at 1.5, 3.0, and 24 hr (P ≤ 0.001) and GH at 24 hr (P ˂ 0.05) but not other time points. Arginine increased glucose and insulin at the 1.5 and 3.0 hr (P ˂ 0.05) but not 24 hr. Arginine did not affect any other dependent measure (P &gt; 0.05) including prolactin. When only individuals with detectable levels of GH (responders; n = 16) were analyzed separately, arginine increased GH at the 1.5 (P ˂ 0.05) but not the 3.0 or 24 hr time points. Among the responders, arginine also increased thyroid stimulating hormone (TSH) at the 24 hr time point (P ˂ 0.05) but not the 1.5 and 3.0 hr time points. Conclusions Arginine supplementation modestly increased growth hormone. Despite their similar structures, prolactin secretion was not elevated following arginine supplementation, thus another mechanism is responsible for growth hormone secretion. Funding Sources DoD and NIH P30DK072476. Views expressed are those of the authors and do not reflect official policy of the Army, DoD, or US Government.

scholarly journals Acute effects of MDMA on trust, cooperative behaviour and empathy: A double-blind, placebo-controlled experiment

2020 ◽  
pp. 026988112092667
Author(s):  
Anna Borissova ◽  
Bart Ferguson ◽  
Matthew B Wall ◽  
Celia JA Morgan ◽  
Robin L Carhart-Harris ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Ultimatum Game ◽  
Subjective Effects ◽  
Plasma Concentrations ◽  
Controlled Experiment ◽  
Prosocial Behaviour ◽  
Cooperative Behaviour ◽  
Acute Effects ◽  
Double Blind ◽  
Bayesian Analyses

Background: 3,4-Methylenedioxymethamphetamine (MDMA) is being actively researched as an adjunct to psychotherapy. It may be beneficial to trust, empathy and cooperative behaviour due to its acute prosocial effects. Aim: To test (a) the acute effects of MDMA on measures of empathy, trust and cooperative behaviour, and (b) subacute changes in mood three days after MDMA administration. Methods: Twenty-five participants ( n=7 female), participated in this double-blind, repeated-measures, placebo-controlled experiment. Participants attended two acute sessions, one week apart. Each acute session was followed by a subacute session three days later. Participants received placebo (100 mg ascorbic acid) during one acute session, and MDMA (100 mg MDMA-HCl) at the other, with order counterbalanced. Participants completed the following tasks assessing prosocial behaviour: a trust investment task, a trustworthy face rating task, an empathic stories task, a public project game, a dictator game and an ultimatum game. Participants reported subjective effects. Blood was taken pre-drug, 2 and 4 hours post-drug, and tested for plasma MDMA levels. Results: MDMA acutely increased self-reported ‘closeness to others’ and ‘euphoria’ and increased plasma concentrations of MDMA. MDMA did not significantly change task-based empathy, trust or cooperative behaviour. Using Bayesian analyses, we found evidence that MDMA and placebo did not differ in their effects on empathy and cooperative behaviour. MDMA did not significantly change subacute mood and this was supported by our Bayesian analyses. Conclusion: Despite augmentation in plasma MDMA levels and subjective drug effects, we found no increase in prosocial behaviour in a laboratory setting.

scholarly journals Time Course and Magnitude of Tolerance to the Ergogenic Effect of Caffeine on the Second Ventilatory Threshold

Life ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 343
Author(s):  
Carlos Ruiz-Moreno ◽  
Beatriz Lara ◽  
Jorge Gutiérrez-Hellín ◽  
Jaime González-García ◽  
Juan Del Coso
Keyword(s):  
Heart Rate ◽  
Aerobic Exercise ◽  
Body Mass ◽  
Repeated Measures ◽  
Time Course ◽  
Ventilatory Threshold ◽  
Statistical Significance ◽  
Ergogenic Effect ◽  
Double Blind ◽  
Main Effects

Pre-exercise caffeine ingestion has been shown to increase the workload at ventilatory threshold, suggesting an ergogenic effect of this stimulant on submaximal aerobic exercise. However, the time course of tolerance to the effect of caffeine on ventilatory threshold is unknown. This study aimed to determine the evolution of tolerance to the ergogenic effect of caffeine on the ventilatory threshold. Methods: Eleven participants (age 32.3 ± 4.9 yrs, height 171 ± 8 cm, body mass 66.6 ± 13.6 kg, VO2max = 48.0 ± 3.8 mL/kg/min) took part in a longitudinal, double-blind, placebo-controlled, randomized, crossover experimental design. Each participant took part in two identical treatments: in one treatment, participants ingested a capsule containing 3 mg of caffeine per kg of body mass per day (mg/kg/day) for twenty consecutive days; in the other treatment, participants ingested a capsule filled with a placebo for the same duration and frequency. During these treatments, participants performed a maximal ramp test on a cycle ergometer three times per week and the second ventilatory threshold (VT2) was assessed by using the ventilatory equivalents for oxygen and carbon dioxide. Results: A two-way ANOVA with repeated measures (substance × time) revealed statistically significant main effects of caffeine (p < 0.01) and time (p = 0.04) on the wattage obtained at VT2, although there was no interaction (p = 0.09). In comparison to the placebo, caffeine increased the workload at VT2 on days 1, 4, 6 and 15 of ingestion (p < 0.05). The size of the ergogenic effect of caffeine over the placebo on the workload at VT2 was progressively reduced with the duration of the treatment. In addition, there were main effects of caffeine (p = 0.03) and time (p = 0.16) on VO2 obtained at VT2, with no interaction (p = 0.49). Specifically, caffeine increased oxygen uptake at VT2 on days 1 and 4 (p < 0.05), with no other caffeine–placebo differences afterwards. For heart rate obtained at VT2, there was a main effect of substance (p < 0.01), while the overall effect of time (p = 0.13) and the interaction (p = 0.22) did not reach statistical significance. Heart rate at VT2 was higher with caffeine than with the placebo on days 1 and 4 (p < 0.05). The size of the effect of caffeine on VO2 and heart at VT2 tended to decline over time. Conclusion: Pre-exercise intake of 3 mg/kg/day of caffeine for twenty days enhanced the wattage obtained at VT2 during cycling ramp tests for ~15 days of ingestion, while there was a progressive attenuation of the size of the ergogenic effect of caffeine on this performance variable. Therefore, habituation to caffeine through daily ingestion may reduce the ergogenic effect of this stimulant on aerobic exercise of submaximal intensity.

Electromyography Activation Levels of the 3 Gluteus Medius Subdivisions During Manual Strength Testing

2015 ◽  
Vol 24 (3) ◽  
pp. 244-251
Author(s):  
Roald Otten ◽  
Johannes L. Tol ◽  
Per Holmich ◽  
Rodney Whiteley
Keyword(s):  
Study Design ◽  
Repeated Measures ◽  
Gluteus Medius ◽  
Strength Testing ◽  
Cross Sectional ◽  
Physically Active ◽  
Rehabilitation Programs ◽  
Significant Difference ◽  
The Individual ◽  
Hip Internal Rotation

Study Design:Cross-sectional.Context:Gluteus medius (GM) muscle dysfunction is associated with overuse injury. The GM is functionally composed of 3 separate subdivisions: anterior, middle, and posterior. Clinical assessment of the GM subdivisions is relevant to detect strength and activation deficits and guide specific rehabilitation programs. However, the optimal positions for assessing the strength and activation of these subdivisions are unknown.Objective:The first aim was to establish which strength-testing positions produce the highest surface electromyography (sEMG) activation levels of the individual GM subdivisions. The second aim was to evaluate differences in sEMG activation levels between the tested and contralateral (stabilizing) leg.Method:Twenty healthy physically active male subjects participated in this study. Muscle activity using sEMG was recorded for the GM subdivisions in 8 different strength-testing positions and analyzed using repeated-measures analysis of variance.Results:Significant differences between testing positions for all 3 GM subdivisions were found. There were significant differences between the tested and the contralateral anterior and middle GM subdivisions (P < .01). The posterior GM subdivision showed no significant difference (P = .154).Conclusion:Side-lying in neutral and side-lying with hip internal rotation are the 2 positions recommended to evaluate GM function and guide specific GM rehabilitation.

Absence of negative feedback by oxytocin on release from magnocellular neurones in conscious rats

1992 ◽  
Vol 70 (1) ◽  
pp. 100-105 ◽  
Author(s):  
Savio W. T. Cheng ◽  
William G. North
Keyword(s):  
Negative Feedback ◽  
Plasma Concentrations ◽  
Plasma Osmolality ◽  
High Plasma ◽  
High Dose ◽  
Salt Loading ◽  
Significant Difference ◽  
And Control ◽  
The Relationship ◽  
Oxytocin Neurones

Peripheral administration of vasopressin (VP) was previously shown to exert a negative feedback influence on its own release and on the release of oxytocin (OT). In this study we examined the possible influence that OT has on the function of hypothalamic magnocellular neurones. Oxytocin was administered intraperitoneally and its effects on release from VP neurones and from OT neurones were determined as indexed by plasma concentrations of vasopressin-associated neurophysin ([VP-RNP]) and oxytocin-associated neurophysin ([OT-RNP]) under basal conditions and conditions of high plasma osmolality (Posm) induced by acute salt loading. Studies were performed on conscious, chronically instrumented Long-Evans rats. Oxytocin (1 nmol or 10 nmol) dissolved in 1 mL of 0.9% saline was administered intraperitoneally to animals 1 h before they received an intravenous infusion of hypertonic saline over 60 min at a rate designed to raise Posm by approximately 0.75 mosmol∙min−1. Intraperitoneal injection of vehicle or 1 nmol of OT did not significantly alter [VP-RNP], [OT-RNP], or basal Posm. Administration of 10 nmol OT also had no effect on [VP-RNP] or [OT-RNP], but this dose of peptide significantly lowered basal Posm (299 ± 2 to 290 ± 2 mosmol/kg H2O, p < 0.001). Both doses of OT did not significantly alter the responsiveness of VP neurones to hyperosmotic stimulation. The slopes of the relationship between the rise in [VP-RNP] (A[VP-RNP]) and the rise in Posm (ΔPosm) for the groups receiving pretreatment of 1 nmol OT (n = 5), 10 nmol OT (n = 7), and vehicle (n = 7) were similar (6.1 ± 1.4, r = 0.86; 5.1 ± 0.9, r = 0.91; and 6.6 ± 0.9 fmol∙mL−1∙mosmol−1∙kg−1, r = 0.93, respectively). For the 1-nmol dose of OT that generated plasma OT levels in the physiological range, the slopes of the relationship between the rise in [OT-RNP] (Δ[OT-RNP]) and ΔPosm over the period of salt loading for peptide-treated animals and control animals (39.5 ± 8.9, r = 0.89 vs. 23.4 ± 5.9, fmol∙mL−1∙mosmol−1∙kg−1, r = 0.93) indicated an increased responsiveness of OT neurones, but this difference was not significant (p < 0.1426). Higher plasma levels of OT were generated by administering the 10 nmol dose of OT, and the slopes of the relationship between Δ[OT-RNP] and ΔPosm for peptide-treated animals and control animals (13.9 ± 1.6, r = 0.96 vs. 23.4 ± 8.9 fmol∙mL−1∙mosmol−1∙kg−1, r = 0.93) suggested a decreased responsiveness of OT neurones, but again this difference was not significant (p < 0.1637). However, there was a significant difference in the rise in OT-RNP with plasma osmolality for rats receiving high versus low dose of peptide (p < 0.0475). Our data indicate that peripherally administered OT, unlike VP, does not exert a negative feedback influence on osmotically stimulated release from VP neurones and most probably OT neurones. However, it cannot be ruled out that the lack of modulation of magnocellular neurones by the high dose of OT could be due to the summation of a positive OT effect (since the 1-nmol group appeared to exhibit an enhancing effect) and of a negative VP effect as indicated by blood pressure increases and plasma dilution. OT also does not appear to have an influence on basal release from magnocellular neurones.Key words: neurophysins, oxytocin neurones, vasopressin neurones.

scholarly journals The Dose-Effects of Caffeine on Lower Body Maximal Strength, Muscular Endurance, and Rating of Perceived Exertion in Strength-Trained Females

Nutrients ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 3342
Author(s):  
Louise Jones ◽  
Iona Johnstone ◽  
Charlotte Day ◽  
Sasha Le Marquer ◽  
Andrew T. Hulton
Keyword(s):  
Effect Size ◽  
Repeated Measures ◽  
Perceived Exertion ◽  
Hormonal Contraception ◽  
Rating Of Perceived Exertion ◽  
Muscular Endurance ◽  
Lower Body ◽  
Double Blind ◽  
Strength Performance ◽  
Significant Difference

Caffeine supplementation has shown to be an effective ergogenic aid enhancing athletic performance, although limited research within female populations exists. Therefore, the aim of the investigation was to assess the effect of pre-exercise caffeine supplementation on strength performance and muscular endurance in strength-trained females. In a double-blind, randomised, counterbalanced design, fourteen strength-trained females using hormonal contraception consumed either 3 or 6 mg·kg−1 BM of caffeine or placebo (PLA). Following supplementation, participants performed a one-repetition maximum (1RM) leg press and repetitions to failure (RF) at 60% of their 1RM. During the RF test, rating of perceived exertion (RPE) was recorded every five repetitions and total volume (TV) lifted was calculated. Repeated measures ANOVA revealed that RF (p = 0.010) and TV (p = 0.012) attained significance, with pairwise comparisons indicating a significant difference between 3 mg·kg−1 BM and placebo for RF (p = 0.014), with an effect size of 0.56, and for 6 mg·kg−1 BM (p = 0.036) compared to the placebo, with an effect size of 0.65. No further significance was observed for 1RM or for RPE, and no difference was observed between caffeine trials. Although no impact on lower body muscular strength was observed, doses of 3 and 6 mg·kg−1 BM of caffeine improved lower body muscular endurance in resistance-trained females, which may have a practical application for enhancing resistance training stimuli and improving competitive performance.

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