Placebo Effect of Caffeine on Maximal Strength and Strength Endurance in Healthy Recreationally Trained Women Habituated to Caffeine

Low and High Doses of Espresso Coffee Improve Repeated Sprint Performance and Eye-Hand Coordination Following Fatigue Status in Male Basketball Players

Background

Although several studies have evaluated the effect of coffee on sports performance, the effect of caffeine on sports performance during fatigue status remains unclear.

Objectives

This study aimed to determine the effect of high and low doses of coffee on the repeated sprint test (RST), perceived fatigue (PF), and eye-hand coordination following physical fatigue status in male basketball players.

Methods

Twenty-four male basketball players were randomly placed in 4 conditions including 1) low-dose espresso coffee (LDEC); 2) high-dose espresso coffee (HDEC); 3) decaffeinated espresso coffee (PLA); and 4) no drinking (CON). PF and eye-hand coordination were measured using the soda pop test (SPT) at baseline, immediately after the RST, and 5 min after the 10 all-out sprints with a 30-s interval of RST.

Results

The time of the first to tenth sprints (RST1 to RST10), total time (RST-TT), mean time (RST-MT), best time (RST-BT), and percentage of performance decrement (PD) were recorded. Coffee dose-dependently significantly improved RST-TT, RST-MT, and RST-BT compared with PLA and CON. PF increased significantly in all conditions immediately after RST compared with baseline. Five minutes after RST, PF was reduced compared to immediately after RST. Immediately after RST, coffee reduced PF dose-dependently compared with PLA and CON. SPT decreased immediately after RST in PLA and CON compared with baseline, whereas no significant change was observed for LDEC and HDEC. At baseline and immediately after RST, coffee and placebo consumption increased SPT performance compared with CON. Immediately and 5 min after RST, coffee increased SPT performance compared to PLA dose-dependently.

Conclusions

HDEC and LDEC improved RST performance and eye-hand coordination in male basketball players. However, HDEC showed a more profound effect compared with LDEC.

Nutritional Strategies for Optimizing Health, Sports Performance, and Recovery for Female Athletes and Other Physically Active Women: A Systematic Review

CONTEXT

Despite the progress toward gender equality in events like the Olympic Games and other institutionalized competitions, and the rising number of women engaging in physical exercise programs, scientific studies focused on establishing specific nutritional recommendations for female athletes and other physically active women are scarce.

OBJECTIVE

This systematic review aimed to compile the scientific evidence available for addressing the question "What dietary strategies, including dietary and supplementation approaches, can improve sports performance, recovery, and health status in female athletes and other physically active women?"

DATA SOURCES

The Pubmed, Web of Science, and Scopus databases were searched.

DATA EXTRACTION

The review process involved a comprehensive search strategy using keywords connected by Boolean connectors. Data extracted from the selected studies included information on the number of participants and their characteristics related to sport practice, age, and menstrual function.

DATA ANALYSIS

A total of 71 studies were included in this review: 17 focused on the analysis of dietary manipulation, and 54 focused on the effects of dietary supplementation. The total sample size was 1654 participants (32.5% categorized as competitive athletes, 30.7% as highly/moderately trained, and 37.2% as physically active/recreational athletes). The risk of bias was considered moderate, mainly for reasons such as a lack of access to the study protocol, insufficient description of how the hormonal phase during the menstrual cycle was controlled for, inadequate dietary control during the intervention, or a lack of blinding of the researchers.

CONCLUSION

Diets with high carbohydrate (CHO) content enhance performance in activities that induce muscle glycogen depletion. In addition, pre-exercise meals with a high glycemic index or rich in CHOs increase CHO metabolism. Ingestion of 5-6 protein meals interspersed throughout the day, with each intake exceeding 25 g of protein favors anabolism of muscle proteins. Dietary supplements taken to enhance performance, such as caffeine, nitric oxide precursors, β-alanine, and certain sport foods supplements (such as CHOs, proteins, or their combination, and micronutrients in cases of nutritional deficiencies), may positively influence sports performance and/or the health status of female athletes and other physically active women.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD480674.

Caffeine Expectancy Does Not Influence the Physical Working Capacity at the Fatigue Threshold

ABSTRACT

Ambrozy, CA, Hawes, NE, Hayden, OL, Sortzi, I, and Malek, MH. Caffeine expectancy does not influence the physical working capacity at the fatigue threshold. J Strength Cond Res 38(6): 1056-1062, 2024-The placebo effect occurs when a desired outcome is experienced due to the belief that a treatment is effective, even in the absence of an active ingredient. One explanation for this effect is based on a person's expectations of a drug or supplement. Although caffeine's effects on sports performance have been studied, little is known about how expectations of caffeine affect neuromuscular fatigue during continuous muscle action. The physical working capacity at the fatigue threshold (PWCFT) can be used to assess neuromuscular fatigue noninvasively using surface electromyography. Thus, the purpose of this study was to investigate whether caffeine expectancy influences PWCFT. We hypothesized that regardless of expectancy, caffeine consumption would delay neuromuscular fatigue. The study involved 8 healthy college-aged men (mean ± SEM: age, 25.6 ± 1.0 years) who visited the laboratory on 4 occasions, each separated by 7 days. The subjects completed 4 experimental conditions, in random order, where they were told that they were consuming caffeine or placebo and either received caffeine or placebo. After consuming the drink, the subjects remained in the laboratory for an hour and then performed an incremental exercise test. The results showed that the condition where subjects were told that they were consuming caffeine and received caffeine had significantly higher mean values for maximal power output (F(3, 21) = 11.75; p < 0.001), PWCFT (F(3, 21) = 12.28; p < 0.001), PWCFT (%maximal power output; F(3, 21) = 8.75; p < 0.001), and heart rate at end exercise (%predicted; F(3, 21) = 3.83; p = 0.025) compared with the 2 conditions where placebo was received. However, no statistically significant mean differences were found from the condition where subjects were told that they were consuming placebo but consuming caffeine. This suggests that a person's expectancy and potential somatic response may serve as a cue for how an ergogenic aid or placebo could affect subsequent performance.

Repeated mouth rinsing of coffee improves the specific-endurance performance and jump performance of young male futsal players

BACKGROUND

Mouth-rinsing with ergogenic solutions such as carbohydrate and caffeinated drinks has been considered among athletes as a practical nutritional strategy. Therefore, this study aimed to determine the effect of repeated coffee mouth-rinsing (CMR) doses on specific performances of futsal players.

METHOD

Twenty-four male futsal players randomly participated in this randomized, double-blind, and crossover design study. During the intervention, participants were randomly placed in four different conditions including 1. low-dose CMR (LDC, n = 6, ~60 mg caffeine); 2. high-dose CMR (HDC, n = 6, ~125 mg caffeine); 3. decaffeinated CMR (PLA, n = 6, ~10 mg caffeine); and 4. no CMR (CON, n = 6). Vertical jump height was measured at baseline, baseline after CMR (baseline-CMR), immediately after the intermittent futsal endurance test (FIET) (IA-FIET), 5 min after the FIET (5"A-FIET) and 10 min after the FIET (10"A-FIET). Perceived fatigue was also measured by visual analogue scale (VAS) at baseline, IA-FIET, 5"A-FIET, and 10"A-FIET. CMR was also performed at baseline, during FIET (Repeated between levels), and 10'A-FIET. The collected data were analyzed (with SPSS software) by one- and two-way repeated measure ANOVA and Bonferroni post hoc test at P < 0.05 level.

RESULTS

The findings of the present study illustrated that the perceived fatigue in IA-FIET increased significantly compared to the baseline which was accompanied by a significant decrease in 5"A-FIET and 10"A-FIET compared to IA-FIET (P < 0.05), and no significant difference was observed between conditions in the baseline, IA-FIET, 5"A-FIET, and 10"A-FIET (P > 0.05). However, HDC and LDC rose significantly the distance covered in FIET compared to CON and PLA (P < 0.05). In addition, HDC increased the FIET performance more than LDC (P < 0.05). Although there was no difference between any of the conditions at baseline (P > 0.05), baseline-CMR increased significantly the vertical jump height (P < 0.05). At IA-FIET, vertical jump height decreased to baseline levels in CMR conditions but increased in 5"A-FIET, which remained constant until 10"A-FIET (P < 0.05). In addition, vertical jump height in HDC and LDC conditions was significantly higher than CON in IA-FIET, 5"A-FIET, and 10"A-FIET.

CONCLUSION

This study showed that repeated CMR with low and high doses is a useful strategy to improve specific futsal performance. However, higher dose CMR appears to have more profound effects on performance improvement than lower doses.

Acute effects of two caffeine doses on bar velocity during the bench press exercise among women habituated to caffeine: a randomized, crossover, double-blind study involving control and placebo conditions

PURPOSE

The main goal of this study was to evaluate the effectiveness of two different doses of caffeine (3 and 6 mg/kg) to enhance bar velocity during the bench press in women habituated to caffeine.

METHODS

Twelve recreationally trained women (age: 23.3 ± 0.8 years, body mass: 60.7 ± 5.7 kg, bench press one-repetition maximum (1RM): 44.3 ± 7.8 kg, daily caffeine ingestion: 5.7 ± 2.0 mg/kg/day) participated in a randomized double-blind experimental design. Each participant performed four different experimental sessions: after no supplementation (control, CON), after ingesting 3 and 6 mg/kg of caffeine (CAF-3 and CAF-6, respectively), or after ingesting a placebo (PLAC). In each experimental session, the participants performed 3 sets of 3 repetitions of the bench press exercise at 50% 1RM.

RESULTS

A two-way repeated-measures ANOVA with subsequent post hoc analyses indicated significant increases in peak velocity (p < 0.01; ES = 0.91) and mean velocity (p < 0.01; ES = 0.78) after the intake of CAF-6 compared to CON. The study did not show significant differences in bar velocity between CAF-6 and PLAC and between CAF-3 and PLAC. No significant differences in bar velocity were observed between CAF-3 and CAF-6 conditions.

CONCLUSION

These results suggest that 6 mg/kg of caffeine can be an effective dose to improve power-specific training outcomes in women habituated to caffeine. However, the ergogenic effect of 6 mg/kg of caffeine may be derived from a combination of biological effects and expectancy, as this dose was only superior to the control condition with no differences over the placebo.

Effects of Caffeine on Resistance Exercise: A Review of Recent Research

In the last few years, a plethora of studies have explored the effects of caffeine on resistance exercise, demonstrating that this field of research is growing fast. This review evaluates and summarizes the most recent findings. Given that toxic doses of caffeine are needed to increase skeletal muscle contractility, the binding of caffeine to adenosine receptors is likely the primary mechanism for caffeine's ergogenic effects on resistance exercise. There is convincing evidence that caffeine ingestion is ergogenic for (i) one-repetition maximum, isometric, and isokinetic strength; and (ii) muscular endurance, velocity, and power in different resistance exercises, loads, and set protocols. Furthermore, there is some evidence that caffeine supplementation also may enhance adaptations to resistance training, such as gains in strength and power. Caffeine ingestion is ergogenic for resistance exercise performance in females, and the magnitude of these effects seems to be similar to that observed in men. Habitual caffeine intake and polymorphisms within CYP1A2 and ADORA2A do not seem to modulate caffeine's ergogenic effects on resistance exercise. Consuming lower doses of caffeine (e.g., 2-3 mg/kg) appears to be comparably ergogenic to consuming high doses of caffeine (e.g., 6 mg/kg). Minimal effective doses of caffeine seem to be around 1.5 mg/kg. Alternate caffeine sources such as caffeinated chewing gum, gel, and coffee are also ergogenic for resistance exercise performance. With caffeine capsules, the optimal timing of ingestion seems to be 30-60 min before exercise. Caffeinated chewing gums and gels may enhance resistance exercise performance even when consumed 10 min before exercise. It appears that caffeine improves performance in resistance exercise primarily due to its physiological effects. Nevertheless, a small portion of the ergogenic effect of caffeine seems to be placebo-driven.

Placebo Effect of Caffeine on Substrate Oxidation during Exercise

By using deceptive experiments in which participants are informed that they received caffeine when, in fact, they received an inert substance (i.e., placebo), several investigations have demonstrated that exercise performance can be enhanced to a similar degree as a known caffeine dose. This 'placebo effect' phenomenon may be part of the mechanisms explaining caffeine's ergogenicity in exercise. However, there is no study that has established whether the placebo effect of caffeine is also present for other benefits obtained with acute caffeine intake, such as enhanced fat oxidation during exercise. Therefore, the aim of this investigation was to investigate the placebo effect of caffeine on fat oxidation during exercise. Twelve young men participated in a deceptive double-blind cross-over experiment. Each participant completed three identical trials consisting of a step incremental exercise test from 30 to 80% of V.O_2max. In the two first trials, participants ingested either 3 mg/kg of cellulose (placebo) or 3 mg/kg of caffeine (received caffeine) in a randomized order. In the third trial, participants were informed that they had received 3 mg/kg of caffeine, but a placebo was provided (informed caffeine). Fat oxidation rates were derived from stoichiometric equations. In received caffeine, participants increased their rate of fat oxidation over the values obtained with the placebo at 30%, 40%, 50%, and 60% of V.O_2max (all p < 0.050). In informed caffeine, participants increased their rate of fat oxidation at 30%, 40%, 50% 60%, and 70% of V.O_2max (all p < 0.050) over the placebo, while there were no differences between received versus informed caffeine. In comparison to placebo (0.32 ± 0.15 g/min), the rate of maximal fat oxidation was higher in received caffeine (0.44 ± 0.22 g/min, p = 0.045) and in informed caffeine (0.41 ± 0.20 g/min, p = 0.026) with no differences between received versus informed caffeine. However, the intensity at which maximal fat oxidation rate was obtained (i.e., Fat_max) was similar in placebo, received caffeine, and informed caffeine trials (42.5 ± 4.5, 44.2 ± 9.0, and 41.7 ± 10.5% of V.O_2max, respectively, p = 0.539). In conclusion, the expectancy of having received caffeine produced similar effects on fat oxidation rate during exercise than actually receiving caffeine. Therefore, the placebo effect of caffeine is also present for the benefits of acute caffeine intake on substrate oxidation during exercise and it may be used to enhance fat oxidation during exercise in participants while reducing any risks to health that this substance may have.