Article

Dose Effect of Caffeine on Testosterone and Cortisol Responses to Resistance Exercise

May 2008
International Journal of Sport Nutrition and Exercise Metabolism 18(2):131-41

DOI:10.1123/ijsnem.18.2.131

Source
PubMed

Project: Thesis - Hormone Mediated Strategies to Enhance Training and Performance

Authors:

Christopher Beaven

The University of Waikato

Matthew R. Wood

Auckland University of Technology

Show all 6 authorsHide

Interest in the use of caffeine as an ergogenic aid has increased since the International Olympic Committee lifted the partial ban on its use. Caffeine has beneficial effects on various aspects of athletic performance, but its effects on training have been neglected. To investigate the acute effect of caffeine on the exercise-associated increases in testosterone and cortisol in a double-blind crossover study. Twenty-four professional rugby-league players ingested caffeine doses of 0, 200, 400, and 800 mg in random order 1 hr before a resistance-exercise session. Saliva was sampled at the time of caffeine ingestion, at 15-min intervals throughout each session, and 15 and 30 min after the session. Data were log-transformed to estimate percent effects with mixed modeling, and effects were standardized to assess magnitudes. Testosterone concentration showed a small increase of 15% (90% confidence limits, +/- 19%) during exercise. Caffeine raised this concentration in a dose-dependent manner by a further small 21% (+/- 24%) at the highest dose. The 800-mg dose also produced a moderate 52% (+/- 44%) increase in cortisol. The effect of caffeine on the testosterone:cortisol ratio was a small decline (14%; +/- 21%). Caffeine has some potential to benefit training outcomes via the anabolic effects of the increase in testosterone concentration, but this benefit might be counteracted by the opposing catabolic effects of the increase in cortisol and resultant decline in the testosterone:cortisol ratio.

Real and Perceived Effects of Caffeine on Sprint Cycling in Experienced Cyclists

Preprint

Feb 2020

Anderson, DE, German, RE, Harrison, ME, Bourassa, KN, and Taylor, CE. Real and perceived effects of caffeine on sprint cycling in experienced cyclists. J Strength Cond Res XX(X): 000-000, 2020-Caffeine ingestion before an exercise bout may provide ergogenic effects on anaerobic performance, particularly in trained athletes. However, the degree of influence of caffeine may be coupled with the placebo effect. A double-blind, placebo-controlled, randomized design was used to determine the real and perceived effects of caffeine on anaerobic performance. Ten competitively trained cyclists (9 men and 1 woman) completed 3 trials of the Wingate Anaerobic Test (WAnT). Subjects were given coffee that they believed contained a high caffeine dose, a low caffeine dose, or a placebo 45 minutes before WAnT. Subjects were actually given 2 placebos (decaffeinated coffee) and one dose of caffeine (280 mg). Level of significance was p # 0.05. No significant differences were found between trials for blood lactate concentration and heart rate. Seven of the subjects (70%) correctly identified the caffeine trial as the high caffeine trial. Time to peak power was significantly shorter for the trial in which subjects incorrectly guessed they had consumed caffeine when given the placebo compared with placebo trial (1.6 6 0.1 vs. 2.3 6 0.2 seconds). Power drop was significantly higher for the trial in which subjects incorrectly guessed they had consumed caffeine when given the placebo compared with placebo trial (524 6 37 vs. 433 6 35 W). There seems to be a placebo effect of caffeine on anaerobic performance. Improved performance may result from psychological advantages rather than physical advantages. Coaches may find it beneficial to use a placebo to improve anaerobic performance, especially if concerned about the side effects or cost of caffeine.

Real and Perceived Effects of Caffeine on Sprint Cycling in Experienced Cyclists

Article

Jan 2020

Anderson, DE, German, RE, Harrison, ME, Bourassa, KN, and Taylor, CE. Real and perceived effects of caffeine on sprint cycling in experienced cyclists. J Strength Cond Res XX(X): 000-000, 2020-Caffeine ingestion before an exercise bout may provide ergogenic effects on anaerobic performance, particularly in trained athletes. However, the degree of influence of caffeine may be coupled with the placebo effect. A double-blind, placebo-controlled, randomized design was used to determine the real and perceived effects of caffeine on anaerobic performance. Ten competitively trained cyclists (9 men and 1 woman) completed 3 trials of the Wingate Anaerobic Test (WAnT). Subjects were given coffee that they believed contained a high caffeine dose, a low caffeine dose, or a placebo 45 minutes before WAnT. Subjects were actually given 2 placebos (decaffeinated coffee) and one dose of caffeine (280 mg). Level of significance was p ≤ 0.05. No significant differences were found between trials for blood lactate concentration and heart rate. Seven of the subjects (70%) correctly identified the caffeine trial as the high caffeine trial. Time to peak power was significantly shorter for the trial in which subjects incorrectly guessed they had consumed caffeine when given the placebo compared with placebo trial (1.6 ± 0.1 vs. 2.3 ± 0.2 seconds). Power drop was significantly higher for the trial in which subjects incorrectly guessed they had consumed caffeine when given the placebo compared with placebo trial (524 ± 37 vs. 433 ± 35 W). There seems to be a placebo effect of caffeine on anaerobic performance. Improved performance may result from psychological advantages rather than physical advantages. Coaches may find it beneficial to use a placebo to improve anaerobic performance, especially if concerned about the side effects or cost of caffeine.

Effect of Caffeine on Sprint Cycling in Experienced Cyclists

Article

Jun 2018

Anderson, DE, LeGrand, SE, and McCart, RD. Effect of caffeine on sprint cycling in experienced cyclists. J Strength Cond Res XX(X): 000-000, 2018-Research regarding the ergogenic effects of caffeine (CAF) in anaerobic activity remains inconclusive. However, some researchers have found significant improvements in anaerobic performance when testing specifically trained athletes. A double-blind, placebo-controlled, counterbalanced, cross-over design was implemented to assess the impact of CAF on a 30-second Wingate Anaerobic Test (WAnT) in experienced cyclists. Nine experienced cyclists volunteered to participate in this study (men, n = 7 and women, n = 2). The subjects completed 2 separate experimental trials consisting of a 30-second WAnT at a resistance of 9% body mass. In a random order, 1 hour before each WAnT, subjects ingested either a CAF (∼280 mg) or placebo (PLAC) coffee. For each trial, heart rate (HR) and blood lactate (BL) values were recorded at rest, pre-WAnT, post-WAnT, and 5 minutes post-WAnT. After each trial, the subjects recorded their perception of which treatment they received. Heart rate and BL responses were not significantly different between the CAF and PLAC conditions. The ingestion of CAF did not significantly improve peak anaerobic power, mean anaerobic power, nor fatigue index. In at least 1 of the 2 trials, 44% of the subjects incorrectly guessed which substance they had ingested. The findings of this study do not show a significant correlation between CAF ingestion and improved anaerobic performance in experienced cyclists. However, performance enhancements may depend on varying individual responses to CAF. Athletes who are positive CAF responders may consider using coffee before competition to improve anaerobic performance.

The Physiological and Performance Effects of Caffeine Gum Consumed During A Simulated Half-Time By Professional Academy Rugby Union Players

Article

Nov 2017

Despite the prevalence of caffeine as an ergogenic aid, few studies have examined the use of caffeinated gums, especially during half-time in team sports. The physiological (blood lactate, salivary hormone concentrations) and performance (repeated sprints, cognitive function) effects of consuming caffeine gum during a simulated half-time were examined. Professional academy rugby union players (n=14) completed this double-blind, randomized, counterbalanced study. Following pre-exercise measurements , players chewed a placebo (PL) gum for five min before a standardized warm-up and completing repeated sprint testing (RSSA1). Thereafter, during a 15 min simulated half-time period, players chewed either caffeine (CAF: 400 mg; 4.1 ± 0.5 mg·kg) or PL gum for five min before completing a second repeated sprint test (RSSA2). Blood lactate, salivary testosterone and cortisol concentrations, and indices of cognitive function (i.e., reaction time and Stroop test) were measured at baseline, pre-RSSA1, post-RSSA1, pre-RSSA2 and post-RSSA2. Sprint performance was not affected by CAF (P=0.995) despite slower sprint times following the first sprint of both RSSA tests (all P<0.002). Following half-time, salivary testosterone increased by 70% (+97±58 pg·mL) in CAF versus PLA (P<0.001) whereas salivary cortisol remained unchanged (P=0.307). Cognitive performance was unaffected by time and trial (all P>0.05). Although performance effects were absent, chewing caffeine gum increased the salivary testosterone concentrations of professional rugby union players over a simulated half-time. Practitioners may therefore choose to recommend caffeine gum between successive exercise bouts due to the increases in salivary testosterone observed; a variable associated with increased motivation and high-intensity exercise performance.

Nutritional ergogenics aids and rugby performance: systematic review [Ergogênicos nutricionais e desempenho no rugby: revisão sistemática]

Article

Full-text available

Jan 2014

Ergogênicos nutricionais e desempenho no rugby: revisão sistemática Nutritional ergogenics aids and rugby performance: systematic review R e s u m o _______________________________________________________________________________________ Objetivo: Apresentar ergogênicos nutricionais investigados cientificamente envolvendo jogadores de rugby e suas respostas no desempenho em treinos e jogos. Métodos: Foi conduzida revisão sistemática na base PubMed em Janeiro de 2013, utilizando-se as palavras-chave no campo resumo: rugby, suplementation, carbohydrate, protein, amino acid e caffeine de forma isolada e/ou combinada. Para análise, foram considerados estudos originais publicados nos últimos 10 anos. Resultados: Na busca inicial foram encontrados 53 artigos. Após leitura dos títulos e resumos foram excluídos 35 artigos. Cafeína e creatina foram os suplementos mais testados e representam 50% dos artigos analisados com jogadores de rugby. Outros suplementos como β-alanina, bicarbonato, carboidrato, HMB e Tribulus terrestris também foram testados e representam os outros 50% dos trabalhos analisados. Apenas cafeína e creatina apresentaram respostas positivas em medidas de desempenho. Conclusão: Cafeína e creatina podem adicionar respostas ao desempenho de jogadores de rugby submetidos a cargas intensas de trabalho. Por outro lado, consumo de álcool apresentou efeito ergolítico. P a l a v r as-c h a v e : Rugby. Suplementação. Desempenho. A b s t r a c t _______________________________________________________________________________________ Objective: To present nutritional ergogenic aids investigated by scientific research involving rugby players and their performance in trainings and matches. Methods: A systematic review was carried out through Pubmed database in January 2013 with the following keywords: rugby, supplementation, carbohydrate, protein, amino acid and caffeine isolated and/or combined. In the analyses, only original studies published in the last 10 years were considered. Results: Fifty-three articles were found in the initial search. After screening the title and abstract, 35 papers were excluded. Caffeine and creatine were the most tested supplements and they represented 50% of the papers analyzed. Others supplements, like β-alanine, bicarbonate, carbohydrate, HMB and Tribulus terrestris also were experimented and comprised the others 50% of the analyzed works. Only caffeine and creatine showed positive effects on performance measurements. Conclusion: Both caffeine and creatine can improve performance in rugby players under severe word load. On the other hand, alcohol consumption has ergolytic effect. K e y w o r d s : Rugby. Supplementation. Performance.

Caffeine Attenuates Acute Growth Hormone Response to a Single Bout of Resistance Exercise

Article

Jun 2010
J SPORT SCI MED

The purpose of this study was to investigate the effects of caffeine consume on substrate metabolism and acute hormonal responses to a single bout of resistance exercise (RE). Ten resistance-trained men participated in this study. All subjects performed one repetition maximum (1RM) test and then performed two protocols: caffeine (CAF, 6 mg·kg(-1)) and control (CON) in counter balanced order. Subjects performed RE (8 exercises, 3 sets of 10 repetitions at 75% of 1RM) after caffeine or placebo ingestion one hour prior to RE. Blood samples collected prior to treatment ingestion (pre-60), immediately prior to RE (pre-exe), and 0, 15, 30 min post to RE (P0, P15, P30) for analysis of insulin, testosterone, cortisol, growth hormone, glucose, free fatty acid and lactic acid. Each experiment was separated by seven days. In this study, statistical analysis of a two-way analysis of variance (treatment by time) with repeated measures was applied. After ingesting caffeine, the concentrations of free fatty acid (pre- exe, P0, P15, P30) in CAF were significantly higher than CON (p < 0.05). Additionally, the responses of GH (P0, P15, P30) in CAF were significantly lower than CON (p < 0.05), whereas the concentrations of insulin, testosterone and cortisol were not different between CAF and CON (p < 0.05) after RE. The results of this study indicated that caffeine ingestion prior to RE might attenuate the response of GH. This effect might be caused by the elevation in blood FFA concentration at the beginning of RE. Key pointsCaffeine ingestion may attenuate the response of GH to a single bout of resistance exercise.The depression of GH response may be caused by the elevation in serum FFA concentration at the beginning of resistance exercise.Caffeine ingestion before resistance exercise may not alert the concentration of cortisol and testosterone.

Connections between Different Sports and Ergogenic Aids—Focusing on Salivary Cortisol and Amylase

Article

Full-text available

Jul 2021
MED LITH

Athletes are exposed to a tremendous amount of stress, both physically and mentally, when performing high intensity sports with frequent practices, pushing numerous athletes into choose to use ergogenic aids such as caffeine or β-alanine to significantly improve their performance and ease the stress and pressure that is put onto the body. The beneficial or even detrimental effects of these so-called ergogenic aids can be appreciated through the use of numerous diagnostic tools that can analyze various body fluids. In the recent years, saliva samples are gaining more ground in the field of diagnostic as it is a non-invasive procedure, contains a tremendous amount of analytes that are subject to pathophysiological changes caused by diseases, exercises, fatigue as well as nutrition and hydration. Thus, we describe here the current progress regarding potential novel biomarkers for stress and physical activity, salivary α-amylase and salivary cortisol, as well as their use and measurement in combination with different already-known or new ergogenic aids.

Androgen and Glucocorticoid Receptor Phosphorylation Following Resistance Exercise and Pre-Workout Supplementation

Article

May 2021
STEROIDS

Purpose Consumption of caffeine or caffeine containing pre-workout supplements (SUPP) augments steroid hormone responses to resistance exercise (RE). However, the activation of glucocorticoid (GR) and androgen receptors (AR) following RE SUPP has not been investigated. The purpose of this study was to determine the influence of a pre-workout supplement on AR and GR phosphorylation following RE. Methods: In a randomized, counter-balanced, double-blind, placebo-controlled, within-subject crossover study, ten resistance-trained males ((X¯±SD, age=22±2.4 yrs, hgt=175±7 cm, body mass=84.1±11.8kg) performed four sets of 8 repetitions of barbell back squats at 75% of their 1-repetition maximum (1-RM) with two minutes of rest between sets and a fifth set of barbell back squats at 60% of 1-RM until concentric failure. A SUPP or flavor and color matched placebo (PL) was consumed 60-minutes prior to RE. Vastus lateralis muscle biopsies were obtained prior to supplementation at rest (BL), and ten minutes post-exercise (POST). Biopsies were analyzed for phosphorylated GR (ser134, ser211, and ser226) and phosphorylated AR (ser81, ser213, ser515, ser650) via western blotting. Results: pGRser134 decreased, and pGRser226 increased following RE (p<0.05) with no difference between conditions (p>0.05). pGRser211 was unchanged after RE (p>0.05). pARser515 increased, and total AR expression decreased after RE (p<0.05) in SUPP only. Testosterone and cortisol were not different between SUPP and PL at POST (p>0.05). Conclusion: RE influences AR and GR phosphorylation, and SUPP minimally influences this response in the early recovery period.

Effect of Aquarobic and Weight Training on Cortisol Levels in Obese Women

Article

Full-text available

Sep 2016

Exercise is physical stress which potentially causes disruption of homeostasis, especially in sports that is excessively done. Weight Training (LB) and Aquarobic Exercise (LA) can be modulators of handling stress. This research aims at investigating the effect of the difference between LB and LA to physical stress in obese women. The study was conducted in 2014. The method used in this study was randomized experimental pretest-posttest control group design in 36 obese women, aged 45-50 years who were divided into 3 groups, group LB 50% RM, 3 sets, 12 repetition, treatment two times a day for 8 weeks (n = 12), LA 75% HRmax, treatment 2 days for 8 weeks (n = 12) and control group (n = 12). Body Mass Index (BMI) and cortisol levels were measured before and after the treatment. Hypothesis testing was conducted using test (One-Way ANOVA and Kruskal-Wallis) and the mean difference test (Tukey HSD and Mann Whitneys). The results of BMI is increased in the WT group and is decreased in LA group as compared to control group (p <0.05). The decrease of cortisol level is higher than in LA and LB group and controls (p <0.05). LB and LA affect the physical stress that is characterized by the increase in cortisol levels in obese women. Conclusion: LB is more dominant than LA in increasing physical stress.

Acute Effects of 24-h Sleep Deprivation on Salivary Cortisol and Testosterone Concentrations and Testosterone to Cortisol Ratio Following Supplementation with Caffeine or Placebo

Article

Jan 2017

Caffeine has become a popular ergogenic aid amongst athletes and usage to improve athletic performance has been well documented. The effect of caffeine on anabolic and catabolic hormones in a sleep-deprived s tate has had little investigation to date. The purpose of the current study was to investigate the potential of caffeine to offset the effects, if any, of short-term sleep deprivation and exercise on an athlete’s testosterone and cortisol concentrations via salivary technique. Eleven competitive male athletes volunteered to be part of this prospective double-blinded study. Three test days were scheduled for each athlete; one non-sleep deprived, one sleep-deprived with caffeine supplementation (6 mg.kg⁻¹) and one sleep-deprived with placebo ingestion. Sleep deprivation was defined as 24-h without sleep. Each test day was composed of 2 aerobic components: a modified Hoff test and a Yo-Yo test. Testosterone and cortisol concentrations were measured via salivary analysis at 4 different time-points; T1 to T4, representing baseline, and pre- and post-aerobic components, respectively. Overall no significant differences were detected comparing the different sleep states for testosterone or cortisol concentrations. A trend existed whereby the sleep-deprived with caffeine ingestion state mirrored the non-sleep deprived state for cortisol concentration. Therefore, caffeine supplementation may have potential benefits for athletes during short-term aerobic exercise when sleep-deprived. An increase in mean testosterone concentration post-aerobic exercise was only observed in the sleep-deprived with caffeine ingestion state.

The Ergogenic Effects of Supplemental Nutritional AIDS on Anaerobic Performance in Female Athletes

Article

Apr 2016

ATHLETES ARE CONSTANTLY SEARCHING FOR METHODS WITH WHICH TO INCREASE ATHLETIC PERFORMANCE. THE USE OF ERGOGENIC AIDS IS POPULAR AMONG ATHLETES; HOWEVER, MOST RESEARCH IS COLLECTED IN MALE SUBJECTS. BASED ON PHYSIOLOGICAL AND MORPHOLOGICAL DIFFERENCES BETWEEN GENDERS, IT CANNOT BE ASSUMED WOMEN WILL DEMONSTRATE SIMILAR RESPONSES AS MEN. SIXTY-FIVE PERCENT OF FEMALE ATHLETES REPORT USE OF ERGOGENIC AIDS AND IT IS IMPERATIVE TO EVALUATE FEMALE-SPECIFIC BENEFITS. THIS REVIEW PRESENTS THE CURRENT LITERATURE EVALUATING EFFECTS OF ERGOGENIC AIDS ON ANAEROBIC PERFORMANCE IN WOMEN AND RECOMMENDATIONS FOR USE. FOR A VIDEO ABSTRACT OF THIS ARTICLE SEE SUPPLEMENTAL DIGITAL CONTENT 1, http://links.lww.com/SCJ/A180.

Effects of Caffeine Acute Consumption on the Metabolic And Performance Parameters in Male Individuals

Article

Full-text available

Jun 2010

The purpose of this study was to evaluate the effect of acute caffeine consumption on lipid oxidation and performance during aerobic exercise. Fifteen healthy male individuals, 22.3 ± 2.7 years old, performed a progressive test on treadmill for determination of maximal oxygen uptake (VO2max) and ventilatory thresholds. Each volunteer performed three submaximal tests at the intensity of 10% below the second ventilatory threshold, being guided to remain on exercise until exhaustion. Thirty minutes before each submaximal test, the subjects ingested 250ml of one of following drinks: coffee with sweetener (CSW), coffee with sugar (CS) or decaffeinated coffee with sweetener (CD). During the exercise, the individuals's heart rate was monitored and respiratory gases analyses were done. The lipid oxidation was predicted by the respiratory quotient (RQ) during the test and performance was verified by exercise duration. In order to compare the RQ results and time of exercise among the three groups, factorial Anova was used, and a value of p < 0.05 was considered as statistically significant. The individuals had VO2max of 50.18 ± 9.9 ml/kg/min. CAD ingestion caused RQ average of 0.98 ± 0.18, and the average exercise duration was of 24.1 ± 17.04 min; CA ingestion caused RQ average of 0.96 ± 0.2 and the average exercise duration was 24.4 ± 17.8 min. Finally, CD ingestion caused the RQ average of 1.01 ± 0.24, and the average exercise duration was of 20.6 ± 9.7 min. There were no significant differences in the RQ values or exercise duration among the three interventions (p = 0.697 and p = 0.598, respectively). Caffeine did not increase lipid oxidation or performance of young male individuals.

Effects of Carbohydrate Combined with Caffeine on Repeated Sprint Cycling and Agility Performance in Female Athletes

Article

Full-text available

Apr 2014
Sports Nutr Rev J

Background: Caffeine (CAF) has been shown to improve performance during early phase of repeated sprint exercise; however some studies show that CAF also increases the magnitude of physical stress represented by augmented blood lactate, glucose, and cortisol concentrations during latter phase of repeated sprint exercise. No studies have investigated the efficacy of combined carbohydrate (CHO) and CAF consumption during repeated sprint exercise (RSE) in female athletes. Thus, the purpose of this study was to investigate the effects of CAF with CHO supplementation on RSE and agility. Methods: Eleven female athletes completed four experimental trials performed 7 d apart in a double-blind, randomized, and counter-balanced crossover design. Treatments included CAF+PLA (placebo), CAF+CHO, PLA+CHO, and PLA+PLA. Participants ingested capsules containing 6 mg • kg-1 of CAF or PLA 60-min prior to RSE, and 0.8 g • kg-1 of CHO solution or PLA immediately before the RSE, which consisted of ten sets of 5×4-s sprints on the cycle ergometer with 20-s active recovery. The agility T-test (AT-test) was performed before and after the RSE. Blood samples were acquired to assess glucose, lactate, testosterone, and cortisol. Results: During Set 6 of RSE, peak power and mean power were significantly higher in PLA+CHO than those in CAF+PLA and PLA+PLA, respectively (p < .05). Total work was significantly increased by 4.8% and 5.9% with PLA+CHO than those of CAF+CHO and CAF+PLA during Set 3. PLA+CHO also increased total work more than CAF+PLA and PLA+PLA did during Set 6 (p < .05). No significant differences in AT-test performance either before or after the RSE were occurred among treatments (p > .05). Blood lactate and glucose concentrations were significantly higher under CAF+CHO, CAF+PLA, and PLA+CHO versus PLA+PLA (p < .05), but no differences in testosterone or cortisol levels were found (p > .05). Conclusions: Findings indicate that CAF+PLA or CAF+CHO ingestion did not improve repeated sprint performance with short rest intervals or agility. However, CHO ingested immediately prior to exercise provided a small but significant benefit on RSE performance in female athletes. Keywords: anaerobic capacity, ergogenic aids, fatigue, hormone, metabolic substrate, nutrition

Moderate-intensity Exercise Decreases Cortisol Response in Overweight Adolescent Women

Article

Full-text available

Nov 2022

The study purpose was to demonstrate the effect of moderate-intensity exercise on reducing cortisol levels in overweight adolescent women. Materials and methods. This study is an actual trial study with a pre-test randomized control group design involving 20 overweight adolescent women aged 19–22 as research subjects who were randomly divided into two groups, namely CNG (n = 10, control group) and EXG (n = 10, moderate-intensity exercise group). The moderate-intensity exercise intervention was performed for 40 minutes on a treadmill. Cortisol levels were measured using an Enzyme-linked immunosorbent assay (ELISA) kit. Data analysis technique used t-test of independent samples and correlation test using Pearson's correlation coefficient with Statistical Package for Social Sciences (SPSS) version 21. Results. Cortisol levels were obtained as a result of the best means between CNG and EXG (222.57 ± 56.04 vs 225.56 ± 63.96 ng/mL, (p ≥ 0.05)), post-test cortisol levels between CNG and EXG (238, 27 ± 77.94 vs 118.13 ± 12.90 ng/mL, (p ≤ 0.001)) and cortisol Δ between CNG vs EXG (15.71 ± 13.14 vs -107.43 ± 21, 13 ng/mL, (p ≤ 0.001)). Cortisol levels also showed a positive relationship with markers of overweight (p ≤ 0.05). Conclusions. Based on the study results, it was concluded that the cortisol response decreased after moderate-intensity exercise and found a positive relationship between cortisol levels and markers of overweight. These results could be used as a long-term approach to modifying an active lifestyle to reduce stress levels.

Black tea and coffee impact on steroid hormones status in young men

Article

Nov 2022

Tea and coffee alkaloids affect the hormonal status of the body. There are reports about the effect of caffeine on the body under stress, but nearly absent reports on the effect of tea and coffee alkaloids at rest. The aim of this work was to determine whether there is a significant difference in testosterone and cortisol concentrations in the blood of young men before and after drinking indicated beverages. The work was carried out on 21 healthy young males that were tested for blood cortisol levels before and after drinking tea or coffee on an empty stomach. The young men were divided into two groups: the first group comprised those whose cortisol levels increased after taking a single dose of tea, the second group – whose cortisol decreased. The third group comprised persons who took a single dose of strong-grain coffee. In addition, adrenaline and testosterone levels were determined as a hormonal panel. Our pioneer investigation found that coffee causes a significant decrease in cortisol levels at rest, but tea consumption by coffee drinkers leads to a more pronounced decrease in the cortisol levels than coffee. Keywords: black tea, coffee, cortisol, young man

Chemiluminescent immunoassay overestimates hormone concentrations and obscures testosterone sex differences relative to LC-MS/MS in a field study of diverse adolescents

Article

Full-text available

Apr 2022

Background Methodological comparisons of hormone quantification techniques have repeatedly demonstrated that, in adults, enzyme immunoassay (EIA) inflates steroid hormone concentrations relative to mass spectrometry. However, methodological comparisons in adolescent samples remain rare, and few studies have examined how chemiluminescent immunoassay (CLIA), another popular immunoassay, compares to mass spectrometry. Additionally, no studies have examined how differences in analytical techniques may be affecting relationships between steroid hormone levels and outcomes of interest, such as psychopathology. This pre-registered analysis of an existing dataset measured salivary cortisol and testosterone using both CLIA and liquid chromatography dual mass spectrometry (LC-MS/MS) in a repeated measures (516 samples) sample of 207 9th graders. Methods In aim 1, this study sought to expand on past findings by 1) measuring inflation of testosterone and cortisol by CLIA in a relatively large adolescent sample, and 2) showing that CLIA (like EIA) testosterone inflation was especially true in groups with low ‘true’ testosterone levels. In aim 2, this study sought to examine the impact of hormone quantification method on relationships between hormone levels and psychopathological measures (the Children's Depression Inventory, the Perceived Social Stress Scale, the UCLA Loneliness Scale, and the Anxious Avoidant and Negative Self Evaluation subscales of the Social Anxiety Scale for Adolescents). Results We found that CLIA, like EIA, inflated testosterone and cortisol levels and overestimated female testosterone resulting in suppressed sex differences in testosterone. We did not observe these same patterns when examining testosterone in individuals with differing levels of pubertal development. Results of psychopathology analyses demonstrated no significant method differences in hormone-psychopathology relationships. Conclusions Our findings show that CLIA introduces proportional bias in cortisol and testosterone in a manner that suppresses sex differences in testosterone. Steroid measurement method did not significantly moderate the relationship between hormones and psychopathology in our sample, though more work is needed to investigate this question in larger, clinical samples.

Effects of Nutritional Supplements on Judo‐Related Performance: A Review

Article

Full-text available

Jan 2021
J HUM KINET

The potential ergogenic effect of nutritional supplements depends on their dosage and the type of exercise executed. Aiming at reviewing the research literature regarding sport supplements utilized in judo in order to improve performance, a literature search was performed at the following databases: Dialnet, PubMed, Scielo, Scopus and SportDiscus. A total of 11 articles met the inclusion criteria and were selected. Evidence revised indicates that supplementation with caffeine, β-alanine, sodium bicarbonate, creatine, and β-hydroxy-β-methylbutyrate has a positive effect on judo-related performance. Moreover, there is evidence suggesting that combining some of these nutritional supplements may produce an additive effect.

Does caffeine exert dose‐response effects on saliva secretory IgA following prolonged submaximal running?

Article

Feb 2019

This study examined the dose‐response effects of caffeine on saliva secretory immunoglobulin A (SIgA) responses to prolonged submaximal running. In a double‐blind randomized crossover design, 12 endurance trained male runners (age: 29 ± 3, VO2peak 62.7 ± 5.1 mL·kg⁻¹·min⁻¹, mean ± SD) ran for 70 min at 80% VO2peak 60 min after ingesting 0 (PLA), 2 (2CAF), 4 (4CAF), 6 (6CAF) or 8 (8CAF) mg·kg⁻¹ body mass of caffeine. Unstimulated whole saliva samples were obtained pre‐supplementation, pre‐exercise, mid‐exercise, immediately post‐exercise and 1 h post‐exercise. Saliva caffeine concentrations were significantly increased above pre‐supplement at all time points following caffeine ingestion in a dose‐dependent manner (P < 0.001). Saliva SIgA concentration and secretion rates were unaffected by exercise or caffeine ingestion. Saliva α‐amylase activity was higher in 4CAF, 6CAF and 8CAF when compared to PLA and 2CAF (trial effect, all P < 0.05), but showed no dose‐response between trials (trial effect, all P > 0.05). Saliva α‐amylase activity was shown to be similar between PLA and 2CAF (P > 0.05). In summary, these findings suggest that regardless of dose, caffeine ingestion 60 min prior to prolonged submaximal running has no effect on saliva SIgA responses. This article is protected by copyright. All rights reserved.

Effects of Caffeine Supplementation on Power Performance in a Flywheel Device: A Randomised, Double-Blind Cross-Over Study

Article

Full-text available

Jan 2019

Despite the demonstrated evidence of the importance of eccentric contractions in sports performance, no research has evaluated the ergogenic effects of caffeine on this type of contraction means during flywheel exercises. Therefore, the aims of the present study were to compare the power outcomes, using different inertial loads, between caffeine and placebo conditions. Twenty-four young, healthy, and active men (age: 22.5 ± 4.8 years) took part in the study. A crossed, randomised double-blind design was used to analyse the effects of caffeine on lower limb power outcomes during a flywheel half-squat exercise. Participants completed four sets of eight all-out repetitions with a fixed three-minutes rest interval, and each set was performed using different inertial loads (i.e., 0.025, 0.050, 0.075 and 0.100 kg·m −2). Both the mean power (MP) and peak power (PP) in concentric (CON) and eccentric (ECC) movement phases at each inertial load were recorded after participants were administered either a caffeine supplement (6 mg·kg −1) or placebo (sucrose). Participants receiving a caffeine supplementation demonstrated improvements versus the placebo in total MP (MP total), as well as MP in CON phase (MP con) and in ECC phase (MP ecc) at each inertial load (22.68 to 26.53%; p < 0.01, effect size (ES) = 0.89-1.40). In addition, greater improvements with caffeine ingestion were obtained with respect to the placebo condition (18.79 to 24.98%; p < 0.01, ES = 1.03-1.40) in total PP (PP total), as well as PP in CON phase (PP con) and in ECC phase (PP ecc) at each inertial load. Thus, the supplementation of 6 mg·kg −1 caffeine may be considered to maximise on-field physical performance in those sports characterised by high demands of resistance.

The Influence of Caffeine Supplementation on Resistance Exercise: A Review

Article

Full-text available

Jan 2019
SPORTS MED

This paper aims to critically evaluate and thoroughly discuss the evidence on the topic of caffeine supplementation when performing resistance exercise, as well as provide practical guidelines for the ingestion of caffeine prior to resistance exercise. Based on the current evidence, it seems that caffeine increases both maximal strength and muscular endurance. Furthermore, power appears to be enhanced with caffeine supplementation, although this effect might, to a certain extent, be caffeine dose- and external load-dependent. A reduction in rating of perceived exertion (RPE) might contribute to the performance-enhancing effects of caffeine supplementation as some studies have observed decreases in RPE coupled with increases in performance following caffeine ingestion. However, the same does not seem to be the case for pain perception as there is evidence showing acute increases in resistance exercise performance without any significant effects of caffeine ingestion on pain perception. Some studies have reported that caffeine ingestion did not affect exercise-induced muscle damage, but that it might reduce perceived resistance exercise-induced delayed-onset muscle soreness; however, this needs to be explored further. There is some evidence that caffeine ingestion, compared with a placebo, may lead to greater increases in the production of testosterone and cortisol following resistance exercise. However, given that the acute changes in hormone levels seem to be weakly correlated with hallmark adaptations to resistance exercise, such as hypertrophy and increased muscular strength, these findings are likely of questionable practical significance. Although not without contrasting findings, the available evidence suggests that caffeine ingestion can lead to acute increases in blood pressure (primarily systolic), and thus caution is needed regarding caffeine supplementation among individuals with high blood pressure. In the vast majority of studies, caffeine was administered in capsule or powder forms, and therefore the effects of alternative forms of caffeine, such as chewing gums or mouth rinses, on resistance exercise performance remain unclear. The emerging evidence suggests that coffee might be at least equally ergogenic as caffeine alone when the caffeine dose is matched. Doses in the range of 3–9 mg·kg⁻¹ seem to be adequate for eliciting an ergogenic effect when administered 60 min pre-exercise. In general, caffeine seems to be safe when taken in the recommended doses. However, at doses as high as 9 mg·kg⁻¹ or higher, side effects such as insomnia might be more pronounced. It remains unclear whether habituation reduces the ergogenic benefits of caffeine on resistance exercise as no evidence exists for this type of exercise. Caution is needed when extrapolating these conclusions to females as the vast majority of studies involved only male participants.

Effects of two pre-workout supplements on concentric and eccentric force production during lower body resistance exercise in males and females: A counterbalanced, double-blind, placebo-controlled trial

Article

Full-text available

Dec 2017
Sports Nutr Rev J

Background Pre-workout supplements purportedly enhance feelings of energy, reduce fatigue and improve exercise performance. The purpose of this study was to examine the performance effects of caffeinated and non-caffeinated multi-ingredient pre-workout supplements. Methods In a counterbalanced, double-blind, placebo-controlled design, eccentric and concentric force production during lower body resistance exercise on a mechanized squat device were assessed after supplement ingestion. Repetitions-in-reserve/RPE and subjective feelings of energy, focus and fatigue were also examined. Twenty-one resistance-trained adults (12 F, 9 M) completed three conditions in random order: caffeinated supplement, non-caffeinated supplement and placebo. Subjects were not informed of the presence of a placebo condition. Thirty minutes after supplement ingestion, a 3-repetition maximum test and 5 sets of 6 repetitions were completed using the squat device. Each repetition involved 4-s eccentric and concentric phases, and the force signal throughout each repetition was sampled from a load cell contained within the squat device. The scaled and filtered force signals were analyzed using customized software. Repeated measures analysis of variance and appropriate follow-up analyses were utilized to compare dependent variables, and relevant effect sizes (d) were calculated. ResultsSupplement or placebo ingestion led to similar subjective responses (p > 0.05). Energy (+8 to 44%; d = 0.3 to 0.8) and focus (+8 to 25%; d = 0.3 to 0.5) were acutely increased by supplement or placebo ingestion and decreased as the exercise session progressed. Fatigue was acutely decreased by supplement or placebo ingestion (−7 to 38%; d = −0.1 to −0.6) and increased as the exercise session progressed. Eccentric and concentric forces were unimproved by supplementation during the exercise sets for both sexes. In the non-caffeinated supplement condition only, maximal eccentric force production was lower during sets 3 to 5, as compared to set 1 (p < 0.05). Effect size data indicated that both the caffeinated and non-caffeinated supplements may contribute to small increases in concentric force production in males (+5 to 20%, d = 0.2 to 0.4 relative to placebo), but not females. Conclusions As compared to placebo, caffeinated and non-caffeinated multi-ingredient pre-workout supplements failed to improve concentric and eccentric force production. In males, effect size data indicate a possible small benefit of supplementation on concentric force production, although this was not statistically significant. When resistance-trained subjects were unaware of the presence of a placebo, resistance exercise performance was similar regardless of whether a placebo or multi-ingredient supplement was ingested.

Influence of A Thermogenic Dietary Supplement on Safety Markers, Body Composition, Energy Expenditure, Muscular Performance and Hormone Concentrations: A Randomized, Placebo-Controlled, Double-Blind Trial

Article

Full-text available

Dec 2017
J SPORT SCI MED

Dietary supplementation is commonly employed by individuals seeking to improve body composition and exercise performance. The purpose of the present study was to examine the safety and effectiveness of a commercially available dietary supplement designed to promote thermogenesis and fat loss. In a randomized double-blind trial, participants were assigned to consume placebo or a multi-ingredient supplement containing caffeine, green tea extract, l-carnitine, evodiamine and other ingredients that purportedly enhance thermogenesis. The study included acute baseline testing, a 6-week progressive resistance training and supplementation intervention, and post-intervention testing. Laboratory assessments included resting energy expenditure responses to acute supplement ingestion, evaluation of body composition and muscular performance, and analysis of blood variables (metabolic panel, testosterone, estrogen and cortisol). Dependent variables were analyzed using ANOVA with repeated measures. No unfavorable effects of supplementation were reported, and the supplement did not adversely affect safety markers. However, the supplement did not reduce fat mass or increase lean mass relative to placebo. In the supplement group, lower body maximal strength was increased relative to placebo (+18%, d=1.1 vs. +10%, d=0.5), and cortisol concentrations were decreased relative to placebo (-16%; d=-0.4 vs. +15%, d=.75). However, no differences were observed for upper body maximal strength or muscular endurance. REE increased in response to both supplement and placebo ingestion (placebo: +5%; supplement: +11.5%), but the difference between conditions was not statistically significant. Overall, some select parameters may have been beneficially modified by supplementation, but this did not result in superior weight or fat loss over 6 weeks of supplementation and resistance training.

Effects of caffeine and carbohydrate mouth rinses on repeated sprint performance

Data

Full-text available

Sep 2017

Simultaneous measurement of salivary cortisol and alpha-amylase: Application and recommendations

Article

Aug 2017
NEUROSCI BIOBEHAV R

Salivary cortisol (sCort) and salivary alpha-amylase (sAA) constitute proxy measures of the two major stress response systems, i.e. the hypothalamic-pituitary-adrenal axis and the autonomic nervous system, respectively. Potentially confounding determinants of sCort and sAA may limit a reliable concurrent measurement of both biomarkers, if not adequately considered. We reviewed the most important determinants of sCort and sAA and provide recommendations for handling these potential confounders. We focused on a selection of potential confounders, resulting in an in-depth consideration of age, sex steroid-related factors, somatic health, acute medication, smoking, consumption of food and drinks, alcohol consumption, physical activity/fitness, and sleep. Our review further highlights the importance of the consideration of potential confounders for a reliable and valid simultaneous measurement of sCort and sAA. We thus recommend the control for potential confounders in the study design or in the data analysis.

Changes in Strength, Power, and Steroid Hormones During a Professional Rugby Union Competition

Article

Full-text available

Sep 2009

The purpose of this investigation was to assess changes in strength, power, and levels of testosterone and cortisol over a 13-week elite competitive rugby union season. Thirty-two professional rugby union athletes from a Super 14 rugby team (age, 24.4 +/- 2.7 years; height, 184.7 +/- 6.2 cm; mass, 104.0 +/- 11.2 kg; mean +/- SD) were assessed for upper-body and lower-body strength (bench press and box squat, respectively) and power (bench throw and jump squat, respectively) up to 5 times throughout the competitive season. Salivary testosterone and cortisol samples, along with ratings of perceived soreness and tiredness, were also obtained before each power assessment. An effect size of 0.2 was interpreted as the smallest worthwhile change. A small increase in lower-body strength was observed over the study period (8.5%; 90% confidence limits +/-7.2%), whereas upper-body strength was maintained (-1.2%; +/-2.7%). Decreases in lower-body power (-3.3%; +/-5.5%) and upper-body power (-3.4; +/-4.9%) were small and trivial. There were moderate increases in testosterone (54%; +/-27%) and cortisol (97%; +/-51%) over the competitive season, and the testosterone to cortisol ratio showed a small decline (22%; +/-25%), whereas changes in perceived soreness and tiredness were trivial. Individual differences over the competitive season for all measures were mostly trivial or inestimable. Some small to moderate relationships were observed between strength and power; however, relationships between hormonal concentrations and performance were mainly trivial but unclear. Positive adaptation in strength and power may be primarily affected by cumulative training volume and stimulus over a competitive season. Greater than 2 resistance sessions per week may be needed to improve strength and power in elite rugby union athletes during a competitive season.

Effects of caffeine and carbohydrate mouth rinses on repeated sprint performance

Data

Full-text available

Apr 2017

The effect of diet components on the level of cortisol

Article

Full-text available

Dec 2016
EUR FOOD RES TECHNOL

The way and the quality of nutrition are important factors that can have influence on behavior of both the health and well-being. Proper diet helps to maintain homeostasis in the body. Changes in lifestyle lead to increase the degree of food processing and hence reduce the nutritional value of available products. This forces the use of technological amendments in nourishment, i.e., fortification and formation of diet supplements. Modified food can complement diet in necessary nutrients. Environmental factors like activity can cause adaptation changes in endocrine system of every human. Cortisol is a corticosteroid, in which influence is varied depending on its concentration. Through its multipronged action, it mobilizes organism to fight stress, by ensuring a stable level of glucose, stimulating tissue’s regeneration and inhibiting inflammation processes. Factors like stressful work, personal problems, intensive trainings can lead to long-term sustained, excessive concentration of this hormone, affecting formation of metabolic disorders such as insulin resistance, increased blood pressure, abnormal bone regeneration and collagen synthesis or calcium deficiency in the organism. Diet supplementation is currently extensively used by both healthy and unwell people, in different age, but most commonly refers to physically active people. Lots of widely available dietary supplements contain nutrients which regulate steroid hormones homeostasis. Elaboration of optimal diet is one of the agents determining well-being, health and success. In this paper, we review the current knowledge on the effect of dietary components on level of cortisol.

Low Anabolic Profile in Assessing a Patients Overall Hair Loss

Article

Jan 2015

Lawrence J Shapiro

Today’s society recognizes how supplementation affects the body physiologically; conversely society does not understand the hidden side effects supplementation has on hair. This paper investigates and explains how hair loss is affected by various supplements. This paper was written in order to provide current and future hair loss professionals with an understanding of the numerous biochemical pathways that cause hair loss, and a method to evaluate, educate, and correct patients, resulting in hair loss prevention, growth, and/or faster regrowth. Supplements previously studied were included in this paper and explored further with relativity to the hair. These supplements include: anabolic steroids, creatine, growth hormone, androstenedione/similar pro-hormones, whey protein isolate(WPI), arginine, orthinine, DHEA (dehydroepiandrosterone), HCG (human chorionic gonadotropin), carnivores vs. vegetarians, soy, iodine, egg whites, and caffeine. In finding, particular supplements have a negative effect on hair loss (as illuminated through various metabolic pathways presented in this research). Specifically, whey protein isolate, growth hormones (GH), and anabolic precursors result in the highest amount of hair loss. Review of the patient’s supplements allows the medical practitioner to develop a plan towards hair loss prevention.

Using of Coffee and Cardamom Mixture to Ameliorate Oxidative Stress Induced in γ-irradiated Rats

Article

Jul 2012

Human exposure to ionizing radiation induced overproduction of free radicals leading to oxidative stress. This study aims to evaluate the possibility of using of coffee and cardamom mixture, as natural antioxidant compounds, to ameliorate the damage effect of oxidative stress. Phenolic contents in coffee and essential oils in cardamom were identified by using HPLC chromatography and GC/MS analysis. Four groups of adult male rats were used; the control group (A), the second group (B) received orally mixture extract of coffee and cardamom (60 mg/100g body weight) for 8 weeks, the third group (C) γ-irradiated (6 GY) and the fourth group (D) received orally mixture extract for 8 weeks and exposed to γ-irradiation at the 4th week. The results revealed that the administration of mixture extract of coffee and cardamom were significantly reduced the damage effect induced by γ-irradiation exposure. Accordingly, it could be concluded that, via the adjustment of the antioxidant status, decreasing the releasing of lipid peroxides and the subsequent amending of different biochemical parameters and some hormones, mixture of coffee and cardamom could ameliorate the hazardous effects of oxidative stress induced by irradiation exposure.

Effects of caffeine and carbohydrate mouth rinses on repeated sprint Performance

Article

Full-text available

Jun 2013

Our purpose was to examine the effectiveness of carbohydrate and caffeine mouth rinses in enhancing repeated sprint ability. Previously, studies have shown that a carbohydrate mouth rinse (without ingestion) has beneficial effects on endurance performance that are related to changes in brain activity. Caffeine ingestion has also demonstrated positive effects on sprint performance. However, the effects of carbohydrate or caffeine mouth rinses on intermittent sprints have not been examined previously. Twelve males performed 5 × 6-s sprints interspersed with 24 s of active recovery on a cycle ergometer. Twenty-five milliliters of either a noncaloric placebo, a 6% glucose, or a 1.2% caffeine solution was rinsed in the mouth for 5 s prior to each sprint in a double-blinded and balanced cross-over design. Postexercise maximal heart rate and perceived exertion were recorded, along with power measures. A second experiment compared a combined caffeine-carbohydrate rinse with carbohydrate only. Compared with the placebo mouth rinse, carbohydrate substantially increased peak power in sprint 1 (22.1 ± 19.5 W; Cohen's effect size (ES), 0.81), and both caffeine (26.9 ± 26.9 W; ES, 0.71) and carbohydrate (39.1 ± 25.8 W; ES, 1.08) improved mean power in sprint 1. Experiment 2 demonstrated that a combination of caffeine and carbohydrate improved sprint 1 power production compared with carbohydrate alone (36.0 ± 37.3 W; ES, 0.81). We conclude that carbohydrate and (or) caffeine mouth rinses may rapidly enhance power production, which could have benefits for specific short sprint exercise performance. The ability of a mouth-rinse intervention to rapidly improve maximal exercise performance in the absence of fatigue suggests a central mechanism.

Caffeine Ingestion Reverses the Circadian Rhythm Effects on Neuromuscular Performance in Highly Resistance-Trained Men

Article

Full-text available

Apr 2012
PLOS ONE

To investigate whether caffeine ingestion counteracts the morning reduction in neuromuscular performance associated with the circadian rhythm pattern. Twelve highly resistance-trained men underwent a battery of neuromuscular tests under three different conditions; i) morning (10:00 a.m.) with caffeine ingestion (i.e., 3 mg kg(-1); AM(CAFF) trial); ii) morning (10:00 a.m.) with placebo ingestion (AM(PLAC) trial); and iii) afternoon (18:00 p.m.) with placebo ingestion (PM(PLAC) trial). A randomized, double-blind, crossover, placebo controlled experimental design was used, with all subjects serving as their own controls. The neuromuscular test battery consisted in the measurement of bar displacement velocity during free-weight full-squat (SQ) and bench press (BP) exercises against loads that elicit maximum strength (75% 1RM load) and muscle power adaptations (1 m s(-1) load). Isometric maximum voluntary contraction (MVC(LEG)) and isometric electrically evoked strength of the right knee (EVOK(LEG)) were measured to identify caffeine's action mechanisms. Steroid hormone levels (serum testosterone, cortisol and growth hormone) were evaluated at the beginning of each trial (PRE). In addition, plasma norepinephrine (NE) and epinephrine were measured PRE and at the end of each trial following a standardized intense (85% 1RM) 6 repetitions bout of SQ (POST). In the PM(PLAC) trial, dynamic muscle strength and power output were significantly enhanced compared with AM(PLAC) treatment (3.0%-7.5%; p≤0.05). During AM(CAFF) trial, muscle strength and power output increased above AM(PLAC) levels (4.6%-5.7%; p≤0.05) except for BP velocity with 1 m s(-1) load (p = 0.06). During AM(CAFF), EVOK(LEG) and NE (a surrogate of maximal muscle sympathetic nerve activation) were increased above AM(PLAC) trial (14.6% and 96.8% respectively; p≤0.05). These results indicate that caffeine ingestion reverses the morning neuromuscular declines in highly resistance-trained men, raising performance to the levels of the afternoon trial. Our electrical stimulation data, along with the NE values, suggest that caffeine increases neuromuscular performance having a direct effect in the muscle.

A psychophysiological comparison of on-sight lead and top rope ascents in advanced rock climbers

Article

Feb 2012
SCAND J MED SCI SPOR

Research suggests that lead climbing is both physiologically and psychologically more stressful than top rope climbing for intermediate performers. This observation may not be true for advanced climbers, who train regularly on lead routes and are accustomed to leader falls. The aim of this study was to compare the psychophysiological stresses of lead and top rope on-sight ascents in advanced rock climbers. Twenty-one climbers (18 men and three women) ascended routes near or at the best of their ability (22 Ewbank). Psychological stress was measured preclimb using the Revised Comparative State Anxiety Inventory (CSAI-2R). Plasma cortisol was sampled at six intervals. The volume of oxygen (VO(2) ) and heart rate (Hr) were measured throughout the climbs. No significant differences were found in self-confidence, somatic, or cognitive anxiety between the conditions lead and top rope. No significant differences in plasma cortisol concentration were found between any time points. No significant relationships were found between cortisol and any CSAI-2R measures. No significant differences were found between conditions for VO(2) or blood lactate concentration. During the lead climb, Hr was significantly elevated during the last part of the route. Findings suggest that advanced rock climbers do not find lead climbing to be more stressful than top rope climbing during an on-sight ascent.

Skill execution and sleep deprivation: effects of acute caffeine or creatine supplementation - a randomized placebo-controlled trial

Article

Full-text available

Feb 2011
Sports Nutr Rev J

We investigated the effects of sleep deprivation with or without acute supplementation of caffeine or creatine on the execution of a repeated rugby passing skill. Ten elite rugby players completed 10 trials on a simple rugby passing skill test (20 repeats per trial), following a period of familiarisation. The players had between 7-9 h sleep on 5 of these trials and between 3-5 h sleep (deprivation) on the other 5. At a time of 1.5 h before each trial, they undertook administration of either: placebo tablets, 50 or 100 mg/kg creatine, 1 or 5 mg/kg caffeine. Saliva was collected before each trial and assayed for salivary free cortisol and testosterone. Sleep deprivation with placebo application resulted in a significant fall in skill performance accuracy on both the dominant and non-dominant passing sides (p < 0.001). No fall in skill performance was seen with caffeine doses of 1 or 5 mg/kg, and the two doses were not significantly different in effect. Similarly, no deficit was seen with creatine administration at 50 or 100 mg/kg and the performance effects were not significantly different. Salivary testosterone was not affected by sleep deprivation, but trended higher with the 100 mg/kg creatine dose, compared to the placebo treatment (p = 0.067). Salivary cortisol was elevated (p = 0.001) with the 5 mg/kg dose of caffeine (vs. placebo). Acute sleep deprivation affects performance of a simple repeat skill in elite athletes and this was ameliorated by a single dose of either caffeine or creatine. Acute creatine use may help to alleviate decrements in skill performance in situations of sleep deprivation, such as transmeridian travel, and caffeine at low doses appears as efficacious as higher doses, at alleviating sleep deprivation deficits in athletes with a history of low caffeine use. Both options are without the side effects of higher dose caffeine use.

Caffeinated chewing gum increases repeated sprint performance and augments increases in testosterone in competitive cyclists

Article

Full-text available

Dec 2010
EUR J APPL PHYSIOL

This investigation reports the effects of caffeinated chewing gum on fatigue and hormone response during repeated sprint performance with competitive cyclists. Nine male cyclists (mean ± SD, age 24 ± 7 years, VO(2max) 62.5 ± 5.4 mL kg(-1) min(-1)) completed four high-intensity experimental sessions, consisting of four sets of 30 s sprints (5 sprints each set). Caffeine (240 mg) or placebo was administered via chewing gum following the second set of each experimental session. Testosterone and cortisol concentrations were assayed in saliva samples collected at rest and after each set of sprints. Mean power output in the first 10 sprints relative to the last 10 sprints declined by 5.8 ± 4.0% in the placebo and 0.4 ± 7.7% in the caffeine trials, respectively. The reduced fatigue in the caffeine trials equated to a 5.4% (90% confidence limit ±3.6%, effect size 0.25; ±0.16) performance enhancement in favour of caffeine. Salivary testosterone increased rapidly from rest (~53%) and prior to treatments in all trials. Following caffeine treatment, testosterone increased by a further 12 ± 14% (ES 0.50; ± 0.56) relative to the placebo condition. In contrast, cortisol concentrations were not elevated until after the third exercise set; following the caffeine treatment cortisol was reduced by 21 ± 31% (ES -0.30; ± 0.34) relative to placebo. The acute ingestion of caffeine via chewing gum attenuated fatigue during repeated, high-intensity sprint exercise in competitive cyclists. Furthermore, the delayed fatigue was associated with substantially elevated testosterone concentrations and decreased cortisol in the caffeine trials.

Interactions of cortisol, testosterone, and resistance training: Influence of circadian rhythms

Article

Full-text available

Jun 2010
CHRONOBIOL INT

Diurnal variation of sports performance usually peaks in the late afternoon, coinciding with increased body temperature. This circadian pattern of performance may be explained by the effect of increased core temperature on peripheral mechanisms, as neural drive does not appear to exhibit nycthemeral variation. This typical diurnal regularity has been reported in a variety of physical activities spanning the energy systems, from Adenosine triphosphate-phosphocreatine (ATP-PC) to anaerobic and aerobic metabolism, and is evident across all muscle contractions (eccentric, isometric, concentric) in a large number of muscle groups. Increased nerve conduction velocity, joint suppleness, increased muscular blood flow, improvements of glycogenolysis and glycolysis, increased environmental temperature, and preferential meteorological conditions may all contribute to diurnal variation in physical performance. However, the diurnal variation in strength performance can be blunted by a repeated-morning resistance training protocol. Optimal adaptations to resistance training (muscle hypertrophy and strength increases) also seem to occur in the late afternoon, which is interesting, since cortisol and, particularly, testosterone (T) concentrations are higher in the morning. T has repeatedly been linked with resistance training adaptation, and higher concentrations appear preferential. This has been determined by suppression of endogenous production and exogenous supplementation. However, the cortisol (C)/T ratio may indicate the catabolic/anabolic environment of an organism due to their roles in protein degradation and protein synthesis, respectively. The morning elevated T level (seen as beneficial to achieve muscle hypertrophy) may be counteracted by the morning elevated C level and, therefore, protein degradation. Although T levels are higher in the morning, an increased resistance exercise-induced T response has been found in the late afternoon, suggesting greater responsiveness of the hypothalamo-pituitary-testicular axis then. Individual responsiveness has also been observed, with some participants experiencing greater hypertrophy and strength increases in response to strength protocols, whereas others respond preferentially to power, hypertrophy, or strength endurance protocols dependent on which protocol elicited the greatest T response. It appears that physical performance is dependent on a number of endogenous time-dependent factors, which may be masked or confounded by exogenous circadian factors. Strength performance without time-of-day-specific training seems to elicit the typical diurnal pattern, as does resistance training adaptations. The implications for this are (a) athletes are advised to coincide training times with performance times, and (b) individuals may experience greater hypertrophy and strength gains when resistance training protocols are designed dependent on individual T response.

The effect of ginseng supplementation on anabolic index, muscle strength, body composition, and testosterone and cortisol response to acute resistance exercise in male bodybuilders

Article

Mar 2021
SCI SPORT

Aims Bodybuilders are among the athletes who are more likely to take nutritional supplements such as ginseng. The aim of this study was to investigate the effect of ginseng supplementation on anabolic index, muscle strength, body composition, and testosterone (T) and cortisol (C) response to acute resistance exercise in male bodybuilders. Methods In a pretest–posttest control group design, twenty male bodybuilders were randomly divided into two experimental (EG, n = 10) and control (CG, n = 10) groups. The assessments were carried out in three stages: pre-supplementation (Pre-S), post-supplementation (Post-S), and post-exercise (Post-Ex = after a bodybuilding exercise session as acute resistance exercise). General characteristics of subjects, muscle strength, body composition and blood levels of T and C were measured. The supplementation period was six weeks (two ginseng capsules, twice daily, times of ingestion). The CG group also consumed similar capsules containing starch. Analyses of variances with repeated measures were used to test the significance of changes of variables between three stages of the assessment. P < 0.05 was set as level of significance. Results Ginseng supplementation has no significant effects on C (P = 0.059), anabolic index (T/C ratio, P = 0.463), body mass index (P = 0.182), waist to hip ratio (P = 0.828), and muscle strength (bench press P = 0.684, leg press P = 0.717), while it significantly decreased T levels after acute resistance exercise (EG: Pre-S 4.87 ± 2.54, Post-S 4.80 ± 2.46, Post-Ex 4.17 ± 2.85 ng/mL, CG: Pre-S 4.15 ± 1.36, Post-S 3.73 ± 1.30, Post-Ex 4.46 ± 1.40 ng/mL, P = 0.026) in male bodybuilders. Conclusion It does not appear that six weeks ginseng supplementation simultaneously with bodybuilding exercises has an extra effect on anabolic index, muscle strength and body composition in male bodybuilders, but it does have a decreasing effect on T levels response to acute resistance exercise.

Caffeine added to coffee does not alter the acute testosterone response to exercise in resistance trained males

Article

Oct 2019

Background: This study investigated the effects of coffee ingestion with supplemental caffeine (CAF) on serum testosterone (T) responses to exercise in recreationally strength-trained males. Methods: Subjects ingested 6 mg/kg body weight of caffeine via 12 ounces of coffee (CAF) supplemented with anhydrous caffeine or decaffeinated (DEC) coffee prior to exercise in a randomized, within-subject, crossover design. The exercise session consisted of 21 minutes of high-intensity interval cycling (alternating intensities at power outputs associated with 2.0 mmol/L lactate for two minutes and 4.0 mmol/L lactate for one minute) followed by resistance exercise (seven exercises, three sets of ten repetitions, 65% 1RM, one-minute rest periods). Subjects also completed repetitions to fatigue tests and soreness scales to determine muscle recovery 24 hours following the exercise. Results: T was elevated immediately and 30-minutes post-exercise by 20.5% and 14.3% respectively (P<0.05). There was no main effect for treatment and no exercise x treatment interaction. There were no differences in repetitions to fatigue or soreness between treatments (P>0.05). No relationships were observed between T and any proxy of recovery. Conclusions: While past literature suggests caffeine may enhance T post-exercise, data from the current study suggest that augmented T response is not evident following anhydrous caffeine added to coffee. The duration of T elevation indicates that this protocol is beneficial to creating long-lasting increases in serum testosterone.

Low Anabolic Profile in Assessing a Patient’s Overall Hair Loss

Chapter

May 2018

Today’s society recognizes how supplementation affects the body physiologically; conversely, society does not understand the hidden side effects supplementation has on hair. This scientific paper investigates and explains how hair loss is affected by various supplements. This paper was written in order to provide current and future hair loss professionals with an understanding of the numerous biochemical pathways that cause hair loss and a method to evaluate, educate, and correct patients, resulting in hair loss prevention, growth, and/or faster regrowth. Supplements previously studied were included in this paper and explored further with relativity to the hair. These supplements include anabolic steroids, creatine, growth hormone, androstenedione/similar prohormones, whey protein isolate, arginine, ornithine, DHEA (dehydroepiandrosterone), HCG (human chorionic gonadotropin), carnivores versus vegetarians, soy, iodine, egg whites, and caffeine. In finding, particular supplements have a negative effect on hair loss (as illuminated through various metabolic pathways presented in this research). Specifically, whey protein isolate, growth hormones, and anabolic precursors result in the highest amount of hair loss. Supplemental hormonal modulation of hair regrowth (HMH) is the next step in hair loss prevention.

Caffeine intake is not associated with serum testosterone levels in adult men: cross-sectional findings from the NHANES 1999–2004 and 2011–2012

Article

Apr 2018

Objective: The association of caffeine intake with testosterone remains unclear. We evaluated the association of caffeine intake with serum testosterone among American men and determined whether this association varied by race/ethnicity and measurements of adiposity. Methods: Data were analyzed for 2581 men (≥20 years old) who participated in the cycles of the NHANES 1999–2004 and 2011–2012, a cross-sectional study. Testosterone (ng/mL) was measured by immunoassay among men who participated in the morning examination session. We analyzed 24-h dietary recall data to estimate caffeine intake (mg/day). Multivariable weighted linear regression models were conducted. Results: We identified no linear relationship between caffeine intake and testosterone levels in the total population, but there was a non-linear association (pnonlinearity < .01). Similarly, stratified analysis showed nonlinear associations among Mexican-American and Non-Hispanic White men (pnonlinearity ≤ .03 both) and only among men with waist circumference <102 cm and body mass index <25 kg/m² (pnonlinearity < .01, both). Conclusion: No linear association was identified between levels of caffeine intake and testosterone in US men, but we observed a non-linear association, including among racial/ethnic groups and measurements of adiposity in this cross-sectional study. These associations are warranted to be investigated in larger prospective studies.

EFFECTS OF BITTER COLA (GARCINIA COLA) EXTRACT ON STEROID HORMONES AND SELECTED ELECTROLYTES IN WEST AFRICAN DWARF BUCKS

Preprint

Full-text available

Jan 2013

Twelve mature West African Dwarf bucks were allotted to four treatment groups of three animals per group to determine various doses of Garcinia cola seed extract (GCSE) on testosterone, cortisol, potassium (K +), sodium (Na +) and calcium (Ca 2+) in WAD bucks. Treatment A (0 mg GCSE) received saline solution; Treatment B (50 mg GCSE); Treatment C (100 mg GCSE) and Treatment D (150 mg GCSE). The animals were observed for 20 minutes after GCSE injection for behavioural response. Jugular blood samples were collected from the WAD bucks at 10 min intervals for 3 hours before and after GCSE injection. Plasma testosterone and cortisol concentrations were determined by radioimmunoassay method. Serum electrolytes were determined by atomic absorption spectrophotometry. Injection of GCSE had no effect on mean plasma testosterone concentration while cortisol significantly increased (P< 0.001) in the three treatments as compared with the control (12.21 ng/mL). The injection of GCSE induced behavioural changes in the animals resulting in depression, inability to stand, suppression of feed intake and lethargy for 15 mins after injection. Also, intravenous injection of GCSE significantly increased serum potassium (P< 0.001) and sodium (P< 0.05) but not calcium in the three treatments as compared in the control. These results indicate that GCSE may be involved in the regulation of cortisol, potassium and sodium secretion in bucks. Despite the reported potential benefits of Garcinia cola, its use should be with caution because GCSE has a depressant property.

Phosphodiesterase Inhibitors (PDE Inhibitors) and Male Reproduction

Chapter

Dec 2017
ADV EXP MED BIOL

The nonspecific PDE inhibitors, particularly the methylxanthines: caffeine, pentoxifylline (PTX), and theophylline, are known to stimulate sperm motility in vitro and have been used to treat sperm prior to insemination. The in vivo effects are less dramatic. A beneficial effect of caffeine, which is a constituent of some medications, remains controversial. Very high doses of caffeine do have negative effects on fertility endpoints in men and experimental species. The specific PDE5 inhibitors, particularly sildenafil and tadalafil, are prescribed for erectile dysfunction, as well as pulmonary hypertension, lower urinary tract symptoms, and premature ejaculation. PDE5 is expressed throughout the contractile tissues of the male reproductive tract, generally increasing contractility. Some PDE5 inhibitors tend to increase circulating testosterone levels somewhat. For short-term exposure consistent with use prior to intercourse, there appears to be minimal effects on semen quality. Several large, randomized controlled trials (RCTs) in healthy men have not found adverse effects of long-term use of these drugs on semen quality. RCTs in infertile men have demonstrated a modest increase in semen quality. Animal studies at human equivalent doses (HED) have produced similar results in young males, but a study in aging male rats found progressive decreases in epididymal sperm quality accompanied by consistent degeneration of the seminal tubules suggesting that studies in older men might be warranted. A concerning study in mice found lower fertilization rates in males treated with HED of sildenafil and mated the next day to untreated females than for control males. Fertility studies in humans are needed.

Behavioral Effects of Sport Nutritional Supplements: Fact or Fiction?

Chapter

Jul 2011

Stephen Flora

The pages of fitness, health, sport, and sport enthusiast (biking, running, bodybuilding, etc.) magazines are filled with advertisements for various nutritional supplements, all claiming to significantly improve the athletic performance of the supplement user. These advertisements often include dramatic “before and after” pictures showing greatly changed (improved) physiques that supposedly occurred as a result of taking the advertised supplement. The advertisements may also include pictures of individuals with impressively muscled physiques or pictures of famous athletes who claim to have achieved great results with the advertised supplement. However, “before and after” pictures are often altered. In some cases the pictures may even be taken on the same day and then altered on the computer (widening of the chest and shoulders, narrowing of the waist, airbrushing; Bell, 2008). In advertisements, muscular models might take the advertised supplement, but they also may ingest illegal steroids, use other products, and engage in other physique-altering activities (Bell, 2008). Furthermore, athletes providing testimonials for products are likely to be taking other nutritional supplements as well as participating in other performance-enhancing activities (physical training, getting proper rest) that may account more for performance outcomes than does taking the advertised supplement.

The effect of flywheel-based resistive exercise workouts on testosterone/cortisol ratios

Article

Feb 2012
ISOKINET EXERC SCI

To assess the subsequent testosterone/cortisol ratio (TCr) from flywheel-based resistive exercise, using a within-subjects design volunteers (7 men, 10 women) performed three seated leg press workouts on an ergometer (YoYo Technologies, Stockholm Sweden). Comprised of ten-repetition sets, the workouts entailed: a three-set protocol composed of concentric and eccentric actions (CE3), as well as concentric-only paradigms of three (CO3) and six (CO6) sets. Venous blood, collected before bouts and at one and 30 minutes post-exercise, was used to quantify the TCr. Data were examined with ANOVA and multivariate regression. ANOVA yielded a gender x time TCr interaction, as male values declined significantly yet women's data were unchanged. With the TCr at one and 30 minutes post-exercise as separate criterion measures, and data pooled across genders and workouts, multivariate regression revealed significance per dependent variable. Univariate correlations showed the best predictors of the post-exercise TCr in descending order were: body mass, average power and delta lactate. Gender and quadriceps muscle volume may have acted as confounding variables to allow body mass to the best current study predictor. Continued research should examine additional predictor variables, as current results only accounted for roughly 30% of the total criterion measure variance.

Effects of bitter cola (Garcinia cola) extract on steroid hormones and selected electrolytes in West African Dwarf bucks

Article

Full-text available

Sep 2013

Twelve mature West African Dwarf bucks were allotted to four treatment groups of three animals per group to determine various doses of Garcinia cola seed extract (GCSE) on testosterone, cortisol, potassium (K+), sodium (Na+) and calcium (Ca2+) in WAD bucks. Treatment A (0 mg GCSE) received saline solution; Treatment B (50 mg GCSE); Treatment C (100 mg GCSE) and Treatment D (150 mg GCSE). The animals were observed for 20 minutes after GCSE injection for behavioural response. Jugular blood samples were collected from the WAD bucks at 10 min intervals for 3 hours before and after GCSE injection. Plasma testosterone and cortisol concentrations were determined by radioimmunoassay method. Serum electrolytes were determined by atomic absorption spectrophotometry. Injection of GCSE had no effect on mean plasma testosterone concentration while cortisol significantly increased (P<0.001) in the three treatments as compared with the control (12.21 ng/mL). The injection of GCSE induced behavioural changes in the animals resulting in depression, inability to stand, suppression of feed intake and lethargy for 15 mins after injection. Also, intravenous injection of GCSE significantly increased serum potassium (P<0.001) and sodium (P<0.05) but not calcium in the three treatments as compared in the control. These results indicate that GCSE may be involved in the regulation of cortisol, potassium and sodium secretion in bucks. Despite the reported potential benefits of Garcinia cola, its use should be with caution because GCSE has a depressant property.

The Effects of Carbohydrate and Caffeine Mouth Rinsing on Arm Crank Time-Trial Performance

Article

Full-text available

Jan 2015

This study aimed to determine whether carbohydrate (CHO) and caffeine (CAFF) mouth rinsing would improve 30 minute arm cranking time-trial performance. Twelve male participants (age 21.54 ± 1.28 years, height 179.46 ± 7.38 cm and mass 73.69 ± 5.40 kg) took part in the current investigation. Participants came to the laboratory on 3 occasions during which they performed 30 minute self-paced arm crank time trials. On one occasion water was given as a mouth rinse for 5 s (PLA), on another occasion a 6.4% CHO solution was given for 5 s and finally a 0.032% CAFF solution was given for 5s. Key measurements of distance covered, heart rate (HR), ratings of perceived exertion (RPE), cadence and power output were recorded throughout all trials. Distance covered during the CAFF (15.43 ± 3.27 km) and CHO (15.30 ± 3.31) mouth rinse trials were significantly (p<0.05) greater in comparison to PLA (13.15 ± 3.36 km). Cadence and power output and velocity were also significantly greater during the CAFF and CHO trials compared to PLA and CHO (p<0.05). No significant (P>0.05) differences between trials were observed for HR and RPE. CAFF and CHO mouth rinse serve to improve 30 minute arm cranking performance by mediating increasing cadence and power output without a concurrent increase in RPE and HR.

Caffeine effect on exercise performance and disease issues: An updated mini review

Article

May 2013
Nutr Food Sci

Purpose – The paper aims to describe the effects of caffeine intake on exercise performance as well on diabetes, cirrhosis and asthma. Design/methodology/approach – The review includes the most updated studies found in Pub‐Med all of which are in relation to caffeine and exercise performance as well as its effects on disease issues. Findings – The majority of studies show that caffeine ingestion of about 6 mg of body weight mass may have a positive effect on endurance and anaerobic exercise performance. In addition, if it is consumed together with carbohydrates, it may also improve post‐recovery glycogen synthesis. Intake of caffeine was also found to have a positive effect on the prevention of liver cirrhosis, reducing asthma attacks and lowering the risk of type 2 diabetes. Originality/value – The paper gives information to nutritionists, clinical dietitians and sports nutritionists on the newest data about the effects of caffeine on exercise performance and disease issues.

A Comparison of Capillary, Venous, and Salivary Cortisol Sampling After Intense Exercise

Article

Mar 2014

Venipuncture is expensive, invasive and impractical for many sport science and clinical based settings. Salivary free cortisol is often cited as a non-invasive practical alternative. However, when cortisol concentrations exceed the corticosteroid binding globulin (CBG) point of 500nmol·L-1 a lack of agreement between salivary and venous blood cortisol has been found. Alternatively, capillary blood may present a minimally invasive, cost effective and practical surrogate for determining cortisol concentration. The aim of this study was to determine whether cortisol concentrations sampled from (a) capillary blood and (b) saliva accurately reflect those found in venous blood across a large range of concentrations following intense exercise. Eleven healthy aerobically trained male subjects were recruited. Capillary, salivary and venous blood samples were collected pre and post (immediately post and post 5, 10, 15 and 20 minutes) a treadmill VO2 max test. Capillary and venous concentrations increased at a similar rate following exercise (Cohen's d between 0.14 - 0.33), increasing up to 15 minutes post before a decline was seen. Salivary cortisol values increased at a slower rate compared to venous and capillary cortisol, but continued to increase post 15 minutes (Cohen's d 0.19 - 0.47 and 0.09 - 0.72 respectively). Capillary cortisol accurately reflects concentrations assayed from venous blood across a range of values below and above the CBG binding point. Capillary sampling provides a minimally invasive, cost effective practical surrogate for assessment of HPA function.

Capillary blood salivary cortisol samples accurately reflects venous cortisol following intense exercise

Article

Jan 2012
MED SCI SPORT EXER

Purpose: To determine whether capillary and salivary cortisol samples accurately reflect venous blood cortisol during intense exercise. Venepuncture is the establish “gold standard” for sampling cortisol, but is expensive, highly invasive and impractical for many experimental and clinical settings. Salivary free cortisol is a non-invasive and practical alternative; however, when cortisol concentrations exceed 500 nmol•l there is a lack of agreement between salivary and venous blood cortisol. No known research has assessed whether capillary cortisol accurately reflects venous blood cortisol across a range of concentrations. Methods. Eleven healthy male subjects (26.1 ± 5.0yrs) were recruited. Capillary, salivary and venous blood samples were collected pre and post (immediately post and post 5,10,15 and 20 minutes) a treadmill VO2 max test. Results: A strong relationship was found between capillary and venous coritsol samples (r = 0.899, P = <0.001). Bland-Altman analysis revealed a small but random bias for lower cortisol concentrations with capillary versus venous cortisol sampling. Two-way repeated measures ANOVA revealed a non-significant (P = 0.340) interaction between stage (time post-stress test) and sampling site. There was a moderate relationship between salivary and venous cortisol samples (r = 0.565, p = <0.001). However, Bland-Altman analysis revealed a bias for lower salivary cortisol with greater venous cortisol. Two-way repeated measures ANOVA revealed a significant interaction (P = 0.001) between stage (time post-stress test) and sampling site. Post-hoc contrasts revealed non-significant differences between sampling sites at 0 and 5 minutes post stress test, but significant differences at 10, 15 and 20 minutes – during which venous cortisol was >483.+14.3. Conclusions: Capillary but not salivary is a valid technique for measuring whole bound cortisol following intense exercise.

Capillary Cortisol Sampling during High-Intensity Exercise

Article

Full-text available

May 2012
INT J SPORTS MED

Venepuncture is the established "gold standard" for sampling cortisol, but it is expensive, highly invasive and impractical for many experimental and clinical settings. Salivary free cortisol is a non-invasive and practical alternative; however, when cortisol concentrations exceed 500 nmol · L there is a lack of agreement between salivary (free) and venous (bound) cortisol. No known research has assessed whether capillary cortisol accurately reflects venous blood cortisol across a range of concentrations. The objective of the current study was to determine the agreement between capillary and venous blood samples of total plasma cortisol across a range of concentrations. 11 healthy male subjects (26.1±5.3 years) were recruited. Capillary and venous blood samples were collected pre and post (immediately post and post 5, 10, 15 and 20 min) a treadmill VO2max test. Regression analysis revealed a strong relationship (R2=0.96, y=1.0028x+1.2964 (P<0.05)) between capillary and venous cortisol concentrations. A Bland-Altman plot showed all data was within the upper and lower bounds of the 95% confidence interval, and no systematic bias was evident. In conclusion, capillary sampling is a valid technique for measuring bound cortisol across a range of concentrations.

Acute Caffeine Ingestion's Increase of Voluntarily Chosen Resistance-Training Load After Limited Sleep

Article

Full-text available

Feb 2012
INT J SPORT NUTR EXE

This study aimed to determine whether caffeine ingestion would increase the workload voluntarily chosen by athletes in a limited-sleep state. In a double-blind, crossover study, 16 professional rugby players ingested either a placebo or 4 mg/kg caffeine 1 hr before exercise. Athletes classified themselves into nondeprived (8 hr+) or sleep-deprived states (6 hr or less). Exercise comprised 4 sets of bench press, squats, and bent rows at 85% 1-repetition maximum. Athletes were asked to perform as many repetitions on each set as possible without failure. Saliva was collected before administration of placebo or caffeine and again before and immediately after exercise and assayed for testosterone and cortisol. Sleep deprivation produced a very large decrease in total load (p = 1.98 × 10(-7)). Caffeine ingestion in the nondeprived state resulted in a moderate increase in total load, with a larger effect in the sleep-deprived state, resulting in total load similar to those observed in the nondeprived placebo condition. Eight of the 16 athletes were identified as caffeine responders. Baseline testosterone was higher (p < .05) and cortisol trended lower in non-sleep-deprived athletes. Changes in hormones from predose to preexercise correlated to individual workload responses to caffeine. Testosterone response to exercise increased with caffeine compared with placebo, as did cortisol response. Caffeine increased voluntary workload in professional athletes, even more so under conditions of self-reported limited sleep. Caffeine may prove worthwhile when athletes are tired, especially in those identified as responders.

Making Meaningful Inferences About Magnitudes

Article

Full-text available

Apr 2006

A study of a sample provides only an estimate of the true (population) value of an outcome statistic. A report of the study therefore usually includes an inference about the true value. Traditionally, a researcher makes an inference by declaring the value of the statistic statistically significant or nonsignificant on the basis of a P value derived from a null-hypothesis test. This approach is confusing and can be misleading, depending on the magnitude of the statistic, error of measurement, and sample size. The authors use a more intuitive and practical approach based directly on uncertainty in the true value of the statistic. First they express the uncertainty as confidence limits, which define the likely range of the true value. They then deal with the real-world relevance of this uncertainty by taking into account values of the statistic that are substantial in some positive and negative sense, such as beneficial or harmful. If the likely range overlaps substantially positive and negative values, they infer that the outcome is unclear; otherwise, they infer that the true value has the magnitude of the observed value: substantially positive, trivial, or substantially negative. They refine this crude inference by stating qualitatively the likelihood that the true value will have the observed magnitude (eg, very likely beneficial). Quantitative or qualitative probabilities that the true value has the other 2 magnitudes or more finely graded magnitudes (such as trivial, small, moderate, and large) can also be estimated to guide a decision about the utility of the outcome.

Hormonal and growth factor responses to heavy resistance exercise protocols

Article

Full-text available

Nov 1990

To examine endogenous anabolic hormone and growth factor responses to various heavy resistance exercise protocols (HREPs), nine male subjects performed each of six randomly assigned HREPs, which consisted of identically ordered exercises carefully designed to control for load [5 vs. 10 repetitions maximum (RM)], rest period length (1 vs. 3 min), and total work effects. Serum human growth hormone (hGH), testosterone (T), somatomedin-C (SM-C), glucose, and whole blood lactate (HLa) concentrations were determined preexercise, midexercise (i.e., after 4 of 8 exercises), and at 0, 5, 15, 30, 60, 90, and 120 min postexercise. All HREPs produced significant (P less than 0.05) temporal increases in serum T concentrations, although the magnitude and time point of occurrence above resting values varied across HREPs. No differences were observed for T when integrated areas under the curve (AUCs) were compared. Although not all HREPs produced increases in serum hGH, the highest responses were observed consequent to the H10/1 exercise protocol (high total work, 1 min rest, 10-RM load) for both temporal and time integrated (AUC) responses. The pattern of SM-C increases varied among HREPs and did not consistently follow hGH changes. Whereas temporal changes were observed, no integrated time (AUC) differences between exercise protocols occurred. These data indicate that the release patterns (temporal or time integrated) observed are complex functions of the type of HREPs utilized and the physiological mechanisms involved with determining peripheral circulatory concentrations (e.g., clearance rates, transport, receptor binding). All HREPs may not affect muscle and connective tissue growth in the same manner because of possible differences in hormonal and growth factor release.

The Effect of Different Dosages of Caffeine on Endurance Performance Time

Article

Full-text available

Jun 1995

The effect of different dosages of caffeine (0-5-9-13 mg.kg body weight-1) on endurance performance was examined. Nine well-trained cyclists participated in this study (VO2max 65.1 +/- 2.6 ml.kg-1.min-1). Caffeine capsules were administered in random order and double-blind. One hour after capsule ingestion, subjects cycled until exhaustion at 80% Wmax on an electromagnetically braked cycle ergometer. Blood samples were taken before, during and after the exercise test. Before and after the test a urine sample was obtained. A significant increase in endurance performance was found for all caffeine tests compared to placebo (endurance time 47 +/- 13, 58 +/- 11, 59 +/- 12 and 58 +/- 12 min for 0, 5, 9 and 13 mg.kg-1 body weight, respectively). No differences were found in endurance performance between the three caffeine dosages which indicates that no dose-response relation of caffeine and endurance performance was found. An increased free fatty acid and glycerol concentration was found after caffeine consumption compared with placebo. The mean urinary caffeine concentrations after exercise were 4.8 +/- 1.8, 8.9 +/- 5.2 and 14.9 +/- 6.9 micrograms.ml-1 urine for 5, 9 and 13 mg of caffeine.kg-1 body weight. Only the lowest dose of caffeine resulted in urine caffeine concentrations below the doping limit of the International Olympic Committee of 12 micrograms.ml-1 urine in all individuals. It is concluded that caffeine is an ergogenic aid that stimulates endurance performance. A dose-response relation between caffeine and endurance time was not found for the dose-range investigated.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic, catecholamine, and exercise performance responses to various doses of caffeine

Article

Full-text available

Mar 1995

This study examined the exercise responses of well-trained endurance athletes to various doses of caffeine to evaluate the impact of the drug on exercise metabolism and endurance capacity. Subjects (n = 8) withdrew from all dietary sources of caffeine for 48 h before each of four tests. One hour before exercise they ingested capsules of placebo or caffeine (3, 6, or 9 mg/kg), rested quietly, and then ran at 85% of maximal O2 consumption to voluntary exhaustion. Blood samples for methylxanthine, catecholamine, glucose, lactate, free fatty acid, and glycerol analyses were taken every 15 min. Plasma caffeine concentration increased with each dose (P < 0.05). Its major metabolite, paraxanthine, did not increase between the 6 and 9 mg/kg doses, suggesting that hepatic caffeine metabolism was saturated. Endurance was enhanced with both 3 and 6 mg/kg of caffeine (increases of 22 +/- 9 and 22 +/- 7%, respectively; both P < 0.05) over the placebo time of 49.4 +/- 4.2 min, whereas there was no significant effect with 9 mg/kg of caffeine. In contrast, plasma epinephrine was not increased with 3 mg/kg of caffeine but was greater with the higher doses (P < 0.05). Similarly only the highest dose of caffeine resulted in increases in glycerol and free fatty acids (P < 0.05). Thus the highest dose had the greatest effect on epinephrine and blood-borne metabolites yet had the least effect on performance. The lowest dose had little or no effect on epinephrine and metabolites but did have an ergogenic effect. These results are not compatible with the traditional theory that caffeine mediates its ergogenic effect via enhanced catecholamines.

Skeletal muscle adaptation during early phase of heavy-resistance training in men and women

Article

Full-text available

Apr 1994

An 8-wk progressive resistance training program for the lower extremity was performed twice a week to investigate the time course for skeletal muscle adaptations in men and women. Maximal dynamic strength was tested biweekly. Muscle biopsies were extracted at the beginning and every 2 wk of the study from resistance-trained and from nontrained (control) subjects. The muscle samples were analyzed for fiber type composition, cross-sectional area, and myosin heavy chain content. In addition, fasting blood samples were measured for resting serum levels of testosterone, cortisol, and growth hormone. With the exception of the leg press for women (after 2 wk of training) and leg extension for men (after 6 wk of training), absolute and relative maximal dynamic strength was significantly increased after 4 wk of training for all three exercises (squat, leg press, and leg extension) in both sexes. Resistance training also caused a significant decrease in the percentage of type IIb fibers after 2 wk in women and 4 wk in men, an increase in the resting levels of serum testosterone after 4 wk in men, and a decrease in cortisol after 6 wk in men. No significant changes occurred over time for any of the other measured parameters for either sex. These data suggest that skeletal muscle adaptations that may contribute to strength gains of the lower extremity are similar for men and women during the early phase of resistance training and, with the exception of changes in the fast fiber type composition, that they occur gradually.

The Effects of Supraphysiologic Doses of Testosterone on Muscle Size and Strength in Normal Men

Article

Full-text available

Aug 1996

Athletes often take androgenic steroids in an attempt to increase their strength. The efficacy of these substances for this purpose is unsubstantiated, however. We randomly assigned 43 normal men to one of four groups: placebo with no exercise; testosterone with no exercise; placebo plus exercise; and testosterone plus exercise. The men received injections of 600 mg of testosterone enanthate or placebo weekly for 10 weeks. The men in the exercise groups performed standardized weight-lifting exercises three times weekly. Before and after the treatment period, fat-free mass was determined by underwater weighing, muscle size was measured by magnetic resonance imaging, and the strength of the arms and legs was assessed by bench-press and squatting exercises, respectively. Among the men in the no-exercise groups, those given testosterone had greater increases than those given placebo in muscle size in their arms (mean [+/-SE] change in triceps area, 424 +/- 104 vs. -81 +/- 109 square millimeters; P < 0.05) and legs (change in quadriceps area, 607 +/- 123 vs. -131 +/- 111 square millimeters; P < 0.05) and greater increases in strength in the bench-press (9 +/- 4 vs. -1 +/- 1 kg, P < 0.05) and squatting exercises (16 +/- 4 vs. 3 +/- 1 kg, P < 0.05). The men assigned to testosterone and exercise had greater increases in fat-free mass (6.1 +/- 0.6 kg) and muscle size (triceps area, 501 +/- 104 square millimeters; quadriceps area, 1174 +/- 91 square millimeters) than those assigned to either no-exercise group, and greater increases in muscle strength (bench-press strength, 22 +/- 2 kg; squatting-exercise capacity, 38 +/- 4 kg) than either no-exercise group. Neither mood nor behavior was altered in any group. Supraphysiologic doses of testosterone, especially when combined with strength training, increase fat-free mass and muscle size and strength in normal men.

Muscle Strength and Hormonal Levels in Adolescents: Gender Related Differences

Article

Full-text available

Dec 1998

The purpose of the present investigation was to study muscle strength in adolescents and its relationship to serum levels of testosterone and growth hormone in both genders. Thirty active adolescents (15 boys; age range 11 -12 y/o) participated in the first study. Isokinetic muscle strength of the dominant knee extensors (KE) was determined at 0, 12, 20, 30, 120, 180 and 240 deg/sec using a Cybex 340 dynamometer. The assessment of pubertal status was accomplished using the criteria of Tanner. Serum levels of total testosterone (T) and growth hormone (GH) were determined using radioimmunoassay techniques. Boys had higher (p< 0.001) T levels but no differences in muscle strength were detected between genders. Fifty-seven additional subjects representing three age groups (11-12 y/o, n=18; 13-14, n=21; 17-18, n=18) participated in the second study. A significant increase in peak torque (absolute and corrected for body weight) with age was observed in both genders. There were no significant gender differences in strength for the two youngest age groups, but boys were stronger than girls in the oldest age group (group 3). Testosterone and GH levels increased with age in boys but not in girls. Gender related differences in T were found in groups 2 and 3. A positive correlation (r=0,64 boys; r=0.46 girls) between testosterone levels and absolute muscle strength was seen in both genders. Our results suggest that increases in anabolic hormones precede muscle strength gains in adolescent males. In addition, gender related differences in muscle strength during adolescents cannot be explained solely on the basis of difference in body size or T levels.

Hormonal responses to physical training in high-level peripubertal male gymnasts

Article

Full-text available

Jan 1999
Eur J Appl Physiol Occup Physiol

The effects of performing intensive training during growth remains controversial, with claims of negative effects upon growth and maturation purportedly due at least in part to a combination of hormonal disturbances and inappropriate nutrition. We examined the training-related responses of total testosterone (T), insulin-like growth factor-1 (IGF-1), cortisol (C) and diet in 16 peripubertal (pubertal stage <2) male gymnasts [mean (SD) age 10.5 (0.9) years, training 17.2 (5.6) h x week(-1)] and 17 controls [mean (SD) age 9.6 (1.2) years] over a 10-month period. Fasted, resting morning blood samples (0730-0900 hours) were taken from all children on Monday, Wednesday and Friday during a single week towards the end of each of three phases of gymnastics training: routine development (RD), precompetition (PC) and strength conditioning (SC). Serum concentrations of T, C and IGF-1 did not differ between the groups at any time. The ratio between IGF-1 and cortisol was significantly reduced in gymnasts relative to controls during RD and SC training (P<0.05), although no differences were detected for the T:C ratio. Diet did not correlate with any of the hormonal measurements, and no intergroup differences were found for the rate of growth in height. In summary, these results suggest that either the gymnastics training performed by these subjects was not intense enough to alter adrenal function, or that the gymnasts were well adapted to the training. In contrast, the reduction in the anabolic to catabolic balance represented by the IGF-1:C ratio is suggestive of a catabolic state, perhaps resulting from overstrain, insufficient recovery and/or inadequate caloric intake relative to energy output. While physical training during growth may induce a catabolic state, further research is needed to determine the biological significance of this finding, particularly with regard to growth and maturation.

Caffeine potentiates low frequency muscle force in habitual and nonhabitual caffeine consumers

Article

Full-text available

Dec 2000

The mechanism of action underlying the ergogenic effect of caffeine is still unclear. Caffeine increases the force of muscular contraction during low-frequency stimulation by potentiating calcium release from the sarcoplasmic reticulum. Studies have also suggested an enhancement of lipid oxidation and glycogen sparing as potential mechanisms. Given that several studies have found an ergogenic effect of caffeine with no apparent metabolic effects, it is likely that a direct effect upon muscle is important. Twelve healthy male subjects were classified as habitual (n = 6) or nonhabitual (n = 6) caffeine consumers based on a 4-day diet record analysis, with a mean caffeine consumption of 771 and 14 mg/day for each group, respectively. Subjects were randomly allocated to receive caffeine (6 mg/kg) and placebo (citrate) in a double-blind, cross-over fashion approximately 100 min before a 2-min tetanic stimulation of the common peroneal nerve in a custom-made dynamometer (2 trials each of 20 and 40 Hz). Tetanic torque was measured every 30 s during and at 1, 5, and 15 min after the stimulation protocol. Maximal voluntary contraction strength and peak twitch torque were measured before and after the stimulation protocol. Caffeine potentiated the force of contraction during the final minute of the 20-Hz stimulation (P<0.05) with no effect of habituation. There was no effect of caffeine on 40-Hz stimulation strength nor was there an effect on maximal voluntary contraction or peak twitch torque. These data support the hypothesis that some of the ergogenic effect of caffeine in endurance exercise performance occurs directly at the skeletal muscle level.

Hormonal Responses after Various Resistance Exercise Protocols

Article

Full-text available

Apr 2003
MED SCI SPORT EXER

This study examined the effects of the number of sets on testosterone, cortisol, and growth hormone (hGH) responses after maximum strength (MS), muscular hypertrophy (MH), and strength endurance (SE) protocols. Eleven young men performed multi-joint dynamic exercises using MS (5 reps at 88% of one-repetition maximum (1-RM), 3-min rest) and MH (10 reps at 75% of 1-RM, 2-min rest) protocols with 2, 4, and 6 sets at each exercise; and an SE (15 reps at 60% of 1-RM, 1-min rest) with 2 and 4 sets. Hormonal concentrations were measured before exercise, immediately after, and at 15 and 30 min of recovery. The number of sets did not affect the hormonal responses after the MS protocol. Cortisol and hGH were higher (P < 0.05) after the four-set compared with the two-set sessions in the MH and SE protocols. No differences were observed between the six-set and the four-set sessions in the MH protocol. Cortisol and hGH were higher (P < 0.05) than the MS after the SE and MH protocols, and only when four and six sets were performed in the latter. hGH was higher than the MH after the SE protocol, whether two or four sets were executed, whereas cortisol (P < 0.05) was higher after the SE protocol only when two sets were performed. Testosterone did not change with any workout. The number of sets functions up to a point as a stimulus for increased hormonal concentrations in order to optimize adaptations with MH and SE protocols, and has no effect on a MS protocol. Furthermore, the number of sets may differentiate long-term adaptations with MS, MH, and SE protocols causing distinct hormonal responses.

The association of age, lifestyle factors and chronic disease with testosterone in men: The Tromso Study

Article

Full-text available

Aug 2003

To study whether lifestyle factors and/or chronic disease are associated with the age-related decline of total and free testosterone in men, or if these factors might be associated with the variation of total and free testosterone but not with their age-related decline. A population-based, cross-sectional study was used. Total testosterone and sex hormone binding globulin (SHBG) levels were analyzed and free testosterone levels were calculated in 1563 men participating in the Tromsø study in 1994/1995. Anthropometric characteristics were also measured and two standardized questionnaires completed, including lifestyle factors and medical history. The data were analyzed with multiple linear regression analysis of covariance, and logistic regression. Total and free testosterone were inversely associated (P=0.001 and P<0.001), while SHBG was positively associated (P<0.001) with age. Body mass index (BMI) was inversely associated with total (P<0.001) and free (P=0.016) testosterone and SHBG (P<0.001). Both total and free testosterone were positively associated with tobacco consumption (P<0.001 and P=0.004) and total testosterone was positively associated with coffee consumption (P<0.001). SHBG was positively associated with smoking (P=0.004) and coffee consumption (P<0.001). Men who reported having had a stroke or having a cancer diagnosis had lower levels of total testosterone (P<0.001 and P<0.01) and free testosterone (P<0.01). BMI and smoking are independent contributors to the variation of total and free testosterone and SHBG levels, and coffee consumption to the variation of total testosterone and SHBG. Thus, lifestyle factors can have a direct effect on circulating levels of free endogenous sex hormones and to total levels due to the effect on SHBG levels.

A Hypothalamic-Testicular Neural Pathway Is Influenced by Brain Catecholamines, But Not Testicular Blood Flow

Article

Full-text available

May 2004

We previously reported the existence of a descending multisynaptic, pituitary-independent, neural pathway between the hypothalamus and the testes in the male rat. Stimulation of this pathway by the intracerebroventricular (icv) injection of IL-1beta or corticotropin-releasing factor blunts the testosterone (T) response to human chorionic gonadotropin (hCG). This response is mediated at least in part by catecholamine beta-adrenergic receptor activation. The present work was performed to further investigate the role of brain catecholamines and testicular blood flow in this pathway. The icv injection of 5 microl of 200 proof ethanol (EtOH; 86 micromol) did not result in detectable levels of the drug in the general circulation and did not induce neuronal damage, but rapidly blunted hCG-induced T release while not decreasing LH levels or altering testicular blood flow. EtOH significantly up-regulated transcripts of the immediate-early gene c-fos in the paraventricular nucleus (PVN) of the hypothalamus. Lesions of the PVN blocked the inhibitory effect of IL-1beta on T, but only partially interfered with the influence of EtOH. PVN catecholamine turnover significantly increased after icv injection of IL-1beta, but not EtOH. Brain catecholamine depletion due to the neurotoxin 6-hydroxydopamine did not alter the ability of hCG to induce T release, but significantly reversed the inhibitory effect of icv EtOH or IL-1beta on this response. Collectively, these results indicate that icv-injected IL-1beta or EtOH blunts hCG-induced T secretion through a catecholamine-mediated mechanism that does not depend on either peripherally mediated effects or pituitary LH, and that the PVN plays a role in these effects.

Caffeine and ephedrine: Physiological, metabolic and performance-enhancing effects

Article

Full-text available

Feb 2004

Preparations containing caffeine and ephedrine have become increasingly popular among sportspersons in recent years as a means to enhance athletic performance. This is due to a slowly accumulating body of evidence suggesting that combination of the two drugs may be more efficacious than each one alone. Caffeine is a compound with documented ergogenicity in various exercise modalities, while ephedrine and related alkaloids have not been shown, as yet, to result in any significant performance improvements. Caffeine-ephedrine mixtures, however, have been reported in several instances to confer a greater ergogenic benefit than either drug by itself. Although data are limited and heterogeneous in nature to allow for reaching consensus, the increase in performance is a rather uniform finding as it has been observed during submaximal steady-state aerobic exercise, short- and long-distance running, maximal and supramaximal anaerobic cycling, as well as weight lifting. From the metabolic point of view, combined ingestion of caffeine and ephedrine has been observed to increase blood glucose and lactate concentrations during exercise, wheareas qualitatively similar effects on lipid fuels (free fatty acids and glycerol) are less pronounced. In parallel, epinephrine and dopamine concentrations are significantly increased, wheareas the effects on norepinephrine are less clear. With respect to pulmonary gas exchange during short-term intense exercise, no physiologically significant effects have been reported following ingestion of caffeine, ephedrine or their combination. Yet, during longer and/or more demanding efforts, some sporadic enhancements have indeed been shown. On the other hand, a relatively consistent cardiovascular manifestation of the latter preparation is an increase in heart rate, in addition to that caused by exercise alone. Finally, evidence to date strongly suggests that caffeine and ephedrine combined are quite effective in decreasing the rating of perceived exertion and this seems to be independent of the type of activity being performed. In general, our knowledge and understanding of the physiological, metabolic and performance-enhancing effects of caffeine-ephedrine mixtures are still in their infancy. Research in this field is probably hampered by sound ethical concerns that preclude administration of potentially hazardous substances to human volunteers. In contrast, while it is certainly true that caffeine and especially ephedrine have been associated with several acute adverse effects on health, athletes do not seem to be concerned with these, as long as they perceive that their performance will improve. In light of the fact that caffeine and ephedra alkaloids, but not ephedrine itself, have been removed from the list of banned substances, their use in sports can be expected to rise considerably in the foreseeable future. Caffeine-ephedra mixtures may thus become one of most popular ergogenic aids in the years to come and while they may indeed prove to be one of the most effective ones, and probably one of the few legal ones, whether they also turn out to be one of the most dangerous ones awaits to be witnessed.

Acute Hormonal Responses to Heavy Resistance Exercise in Strength Athletes Versus Nonathletes

Article

Full-text available

Nov 2004
Can J Appl Physiol

The aim of the present study was to investigate acute hormonal and neuromuscular responses and recovery in strength athletes versus nonathletes during heavy resistance exercise performed with the forced and maximum repetitions training protocol. Eight male strength athletes (SA) with several years of continuous resistance training experience and 8 physically active but non-strength athletes (NA) volunteered as subjects. The experimental design comprised two loading sessions: maximum repetitions (MR) and forced repetitions (FR). MR included 12-RM squats for 4 sets with a 2-min recovery between sets. In FR the initial load was higher than in MR so that the subject could lift approximately 8 repetitions by himself and 4 additional repetitions with assistance. Before and after the loading protocols, blood samples were drawn to determine serum testosterone, free testosterone, cortisol and growth hormone concentrations, and blood lactate. Maximal voluntary isometric force and EMG activity of the leg extensors was measured before and after the loading as well as 24 and 48 hrs after the loading. The concentrations of the hormones measured increased significantly (p < .01-.001) after both loadings in both groups. The responses tended to be higher in FR than the MR loading and the increases of testosterone concentrations were significantly (p < .01) greater in both loadings in SA than in NA. Both loading protocols in both groups also led to neuromuscular fatigue observable with significant acute decreases in isometric strength by 32-52% (p < .001) and in maximal iEMG (p < .05-01) associated with large increases in blood lactate. These data suggest that, at least in experienced strength athletes, the forced-repetition protocol is a viable alternative to the more traditional maximum-repetition protocol and may even be a superior approach.

Hormonal Responses and Adaptations to Resistance Exercise and Training

Article

Full-text available

Feb 2005

Resistance exercise has been shown to elicit a significant acute hormonal response. It appears that this acute response is more critical to tissue growth and remodelling than chronic changes in resting hormonal concentrations, as many studies have not shown a significant change during resistance training despite increases in muscle strength and hypertrophy. Anabolic hormones such as testosterone and the superfamily of growth hormones (GH) have been shown to be elevated during 15-30 minutes of post-resistance exercise providing an adequate stimulus is present. Protocols high in volume, moderate to high in intensity, using short rest intervals and stressing a large muscle mass, tend to produce the greatest acute hormonal elevations (e.g. testosterone, GH and the catabolic hormone cortisol) compared with low-volume, high-intensity protocols using long rest intervals. Other anabolic hormones such as insulin and insulin-like growth factor-1 (IGF-1) are critical to skeletal muscle growth. Insulin is regulated by blood glucose and amino acid levels. However, circulating IGF-1 elevations have been reported following resistance exercise presumably in response to GH-stimulated hepatic secretion. Recent evidence indicates that muscle isoforms of IGF-1 may play a substantial role in tissue remodelling via up-regulation by mechanical signalling (i.e. increased gene expression resulting from stretch and tension to the muscle cytoskeleton leading to greater protein synthesis rates). Acute elevations in catecholamines are critical to optimal force production and energy liberation during resistance exercise. More recent research has shown the importance of acute hormonal elevations and mechanical stimuli for subsequent up- and down-regulation of cytoplasmic steroid receptors needed to mediate the hormonal effects. Other factors such as nutrition, overtraining, detraining and circadian patterns of hormone secretion are critical to examining the hormonal responses and adaptations to resistance training.

Caffeine improves endurance in 75-yr-old citizens: A randomized, double-blind, placebo-controlled, crossover study

Article

Full-text available

Jan 2006

This study investigated the effect of caffeine on physical performance in healthy citizens aged > or =70 yr. The randomized, double-blind, placebo-controlled, crossover study was conducted in 15 men and 15 women recruited by their general practitioner. Participants abstained from caffeine for 48 h and were randomized to receive one capsule of placebo and then caffeine (6 mg/kg) or caffeine and then placebo with 1 wk in between. One hour after intervention, we measured reaction and movement times, postural stability, walking speed, cycling at 65% of expected maximal heart rate, perceived effort during cycling, maximal isometric arm flexion strength, and endurance. Analysis was by intention to treat, and P < 0.05 was regarded as significant. Caffeine increased cycling endurance by 25% [95% confidence interval (CI): 13-38; P = 0.0001] and isometric arm flexion endurance by 54% (95% CI: 29-83; P = 0.0001). Caffeine also reduced the rating of perceived exertion after 5 min of cycling by 11% (95% CI: 5-17; P = 0.002) and postural stability with eyes open by 25% (95% CI: 2-53; P = 0.03). Caffeine ingestion did not affect muscle strength, walking speed, reaction, and movement times. At the end of the study, 46% of participants correctly identified when they received caffeine and placebo. Caffeine increased exercise endurance in healthy citizens aged > or =70 yr, but the participants' reasons for stopping the test may have varied between subjects, as the cycling test was done at approximately 55% of maximal oxygen consumption. Further studies are required to investigate whether caffeine can be utilized to improve the physical performance of elderly citizens.

Independent and combined effets of liquid carbohydrate/essential amino acid ingestion on hormonal and muscular adaptations following resistance training in untrained men

Article

Full-text available

May 2006

This investigation examined chronic alteration of the acute hormonal response associated with liquid carbohydrate (CHO) and/or essential amino acid (EAA) ingestion on hormonal and muscular adaptations following resistance training. Thirty-two untrained young men performed 12 weeks of resistance training twice a week, consuming ~675 ml of either, a 6% CHO solution, 6 g EAA mixture, combined CHO + EAA supplement or placebo (PLA). Blood samples were obtained pre- and post-exercise (week 0, 4, 8, and 12), for determination of glucose, insulin, and cortisol. 3-Methylhistidine excretion and muscle fibre cross-sectional area (fCSA) were determined pre- and post-training. Post-exercise cortisol increased (P<0.05) during each training phase for PLA. No change was displayed by EAA; CHO and CHO + EAA demonstrated post-exercise decreases (P<0.05). All groups displayed reduced pre-exercise cortisol at week 12 compared to week 0 (P<0.05). Post-exercise insulin concentrations showed no change for PLA; increases were observed for the treatment groups (P<0.05), which remained greater for CHO and CHO + EAA (P<0.001) than PLA. EAA and CHO ingestion attenuated 3-methylhistidine excretion 48 h following the exercise bout. CHO + EAA resulted in a 26% decrease (P<0.01), while PLA displayed a 52% increase (P<0.01). fCSA increased across groups for type I, IIa, and IIb fibres (P<0.05), with CHO + EAA displaying the greatest gains in fCSA relative to PLA (P<0.05). These data indicate that CHO + EAA ingestion enhances muscle anabolism following resistance training to a greater extent than either CHO or EAA consumed independently. The synergistic effect of CHO + EAA ingestion maximises the anabolic response presumably by attenuating the post-exercise rise in protein degradation.

Cortisol responses to mental stress, exercise, and meals following caffeine intake in men and women

Article

Full-text available

Mar 2006
PHARMACOL BIOCHEM BE

Caffeine elevates cortisol secretion, and caffeine is often consumed in conjunction with exercise or mental stress. The interactions of caffeine and stress on cortisol secretion have not been explored adequately in women. We measured cortisol levels at eight times on days when healthy men and women consumed caffeine (250 mg x 3) and underwent either mental stress or dynamic exercise protocols, followed by a midday meal, in a double blind, placebo-controlled, crossover design. Men and women had similar cortisol levels at the predrug baselines, but they responded differently to mental stress and exercise. The cortisol response to mental stress was smaller in women than in men (p=.003). Caffeine acted in concert with mental stress to further increase cortisol levels (p=.011), the effect was similar in men and women. Exercise alone did not increase cortisol, but caffeine taken before exercise elevated cortisol in both men and women (ps<.05). After a postexercise meal, the women had a larger cortisol response than the men, and this effect was greater after caffeine (p<.01). Cortisol release in response to stress and caffeine therefore appears to be a function of the type of stressor and the sex of the subject. However, repeated caffeine doses increased cortisol levels across the test day without regard to the sex of the subject or type of stressor employed (p<.00001). Caffeine may elevate cortisol by stimulating the central nervous system in men but may interact with peripheral metabolic mechanisms in women.

The Effects of Caffeine Ingestion on Performance Time, Speed and Power during a Laboratory-based 1 km Cycling Time-trial

Article

Full-text available

Dec 2006

There is little published data in relation to the effects of caffeine upon cycling performance, speed and power in trained cyclists, especially during cycling of approximately 60 s duration. To address this, eight trained cyclists performed a 1 km time-trial on an electronically braked cycle ergometer under three conditions: after ingestion of 5 mg x kg-1 caffeine, after ingestion of a placebo, or a control condition. The three time-trials were performed in a randomized order and performance time, mean speed, mean power and peak power were determined. Caffeine ingestion resulted in improved performance time (caffeine vs. placebo vs. control: 71.1 +/- 2.0 vs. 73.4 +/- 2.3 vs. 73.3 +/- 2.7 s; P = 0.02; mean +/- s). This change represented a 3.1% (95% confidence interval: 0.7-5.6) improvement compared with the placebo condition. Mean speed was also higher in the caffeine than placebo and control conditions (caffeine vs. placebo vs. control: 50.7 +/- 1.4 vs. 49.1 +/- 1.5 vs. 49.2 +/- 1.7 km x h-1; P = 0.0005). Mean power increased after caffeine ingestion (caffeine vs. placebo vs. control: 523 +/- 43 vs. 505 +/- 46 vs. 504 +/- 38 W; P = 0.007). Peak power also increased from 864 +/- 107 W (placebo) and 830 +/- 87 W (control) to 940 +/- 83 W after caffeine ingestion (P = 0.027). These results provide support for previous research that found improved performance after caffeine ingestion during short-duration high-intensity exercise. The magnitude of the improvements observed in our study could be due to our use of sport-specific ergometry, a tablet form and trained participants.

Statistical power analysis for the behavioral sciences

Book

Jan 1988

J. Cohen

Sifting the evidence-what's wrong with significance tests?

Article

Aug 2001

The findings of medical research are often met with considerable scepticism, even when they have apparently come from studies with sound methodologies that have been subjected to appropriate statistical analysis. This is perhaps particularly the case with respect to epidemiological findings that suggest that some aspect of everyday life is bad for people. Indeed, one recent popular history, the medical journalist James Le Fanu's The Rise and Fall of Modern Medicine , went so far as to suggest that the solution to medicine's ills would be the closure of all departments of epidemiology.1 One contributory factor is that the medical literature shows a strong tendency to accentuate the positive; positive outcomes are more likely to be reported than null results.2–4 By this means alone a host of purely chance findings will be published, as by conventional reasoning examining 20 associations will produce one result that is “significant at P = 0.05” by chance alone. If only positive findings are published then they may be mistakenly considered to be of importance rather than being the necessary chance results produced by the application of criteria for meaningfulness based on statistical significance. As many studies contain long questionnaires collecting information on hundreds of variables, and measure a wide range of potential outcomes, several false positive findings are virtually guaranteed. The high volume and often contradictory nature5 of medical research findings, however, is not only because of publication bias. A more fundamental problem is the widespread misunderstanding of the nature of statistical significance. In this paper we consider how the practice of significance testing emerged; an arbitrary division of results as “significant” or “non-significant” (according to the commonly used threshold of P = 0.05) was not the intention of the founders of statistical inference. P values need to be …

Adenosine Receptors and Autonomic Regulation

Article

Dec 2012

Italo Biaggioni

This chapter focuses on adenosine receptors and autonomic regulation and presynaptic effects of adenosine on efferent nerves and ganglionic transmission. Adenosine A1 receptors are found in target organs innervated by the sympathetic nervous system. A1 receptors are coupled to inhibition of adenylate cyclase and their effects are opposite to those of β-adrenoreceptor agonists. Adenosine inhibits the release of neurotransmitters through putative presynaptic A1 receptors in both the brain and the periphery. Adenosine acts as a neuromodulator within the central nervous systems, mostly through interaction with A1 and A2A receptors. Of particular relevance to this review are its actions on brainstem nuclei involved in autonomic cardiovascular regulation. Pain resembling angina has been reported with intravenous and intracoronary administration of adenosine presumably because of activation of sensory afferents. Intracoronary adenosine also elicits a pressor reflex in humans, which may be explained by activation of myocardial afferents. ATP has also been implicated as a trigger of skeletal muscle afferent activation.

Caffeine and Ephedrine

Article

Nov 2004

Dose Effect of Caffeine on Testosterone and Cortisol Responses to Resistance Exercise

Abstract

No full-text available