Caffeine Timing Improves Lower-Body Muscular Performance: A Randomized Trial

Abstract

Little is known about the optimal time to consume caffeine prior to exercise to maximize the ergogenic benefits of the substance.Purpose: To determine the optimal pre-exercise time interval to consume caffeine to improve lower-body muscular performance. A secondary aim was to identify the presence of any sex differences in responses to timed caffeine administration.Methods: Healthy, resistance-trained males (n = 18; Mean±SD; Age: 25.1 ± 5.7 years; Height: 178.4 ± 7.1 cm; Body mass: 91.3 ± 13.5 kg; Percent body fat: 20.7 ± 5.2; Average caffeine consumption: 146.6 ± 100.3 mg/day) and females (n = 11; Mean ± SD; Age: 20.1 ± 1.6 years; Height: 165.0 ± 8.8 cm; Body mass: 65.8 ± 10.0 kg; Percent bodyfat: 25.8 ± 4.2; Average caffeine consumption: 111.8 ± 91.7 mg/day) participated in this investigation. In a randomized, double-blind, placebo-controlled, crossover fashion, participants consumed 6 mg·kg−1 caffeine or placebo solution at three time points: 2 h prior (2H), 1 h prior (1H), or 30 min prior (30M) to exercise testing. During three visits, caffeine was randomly administered at one time point, and placebo was administered at the other two time points. During one visit, placebo was administered at all three time points. Next, participants performed isometric mid-thigh pulls (IMTP), countermovement vertical jumps (CMVJ), and isometric/isokinetic knee extensor testing (ISO/ISOK).Results: Caffeine administered at 1H significantly improved absolute CMVJ and ISO performance relative to placebo. Mean CMVJ jump height was significantly higher during 1H compared to 30M. However, only caffeine administered at 30M significantly improved absolute measures of isokinetic performance. Analysis of the pooled caffeine conditions revealed that muscular performance was more consistently augmented by caffeine in males compared to females.Conclusions: Pre-exercise caffeine timing significantly modulated participant responses to the substance, with 1H exerting the most consistent ergogenic benefits relative to other time points, particularly compared to 2H. Male participants were found to respond more consistently to caffeine compared to female participants. These results suggest that active individuals can maximize the ergogenic effects of caffeine by consuming the substance ~1 h prior to the point when peak muscular performance is desired.

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

“…One study [35] included 15 resistancetrained women and reported that caffeine ingestion (4 mg/ kg) enhanced 1RM strength and muscular endurance in the bench press and squat. Positive effects of caffeine on muscular strength and endurance were essentially confirmed in six other studies [25,36,40,48,49,52].…”

“…Studies have also provided novel data that expanded our knowledge about caffeine's ergogenic effects on isometric and isokinetic strength [9,25,31,32,35,37,45,49,66,67] (Table 1). These studies have reinforced that caffeine ingestion has a significant ergogenic effect on isometric and isokinetic strength, with effect sizes ranging from 0.15 to 0.65 [9,25,32,35,49]. Besides affecting maximum strength, caffeine ingestion also has a moderate effect (Cohen's d: 0.56) on the rate of torque development [37].…”

“…This was highlighted in a commentary that summarized data from 362 primary studies on caffeine and exercise and found that only 13% of participants included in the studies were females [80]. Several studies recognized this limitation and directly explored caffeine's effects on resistance exercise performance in women [25,28,35,36,40,48,49,52]. One study [35] included 15 resistancetrained women and reported that caffeine ingestion (4 mg/ kg) enhanced 1RM strength and muscular endurance in the bench press and squat.…”

“…While it is clear that caffeine ingestion enhances resistance exercise performance in women, it is not yet fully elucidated if there is a sex-specific response to these ergogenic effects. Several studies directly compared the effects of caffeine on muscular strength and endurance between men and women while reporting similar responses between sexes [9,25,81]. For example, one study [81] included ten elite collegiate male and female athletes.…”

Energy Drinks May Improve Postural Sway While Provoking an Early Onset of Muscle Fatigue

“…It is likewise fundamental to delve into the effects of EDs in younger populations, such as those 14-18 years old, who are frequently the consumers of these EDs. One last note, as suggested by Harty, PS et al [24], additional considerations could focus on data collection after one hour of caffeine/ED consumption.…”