Fact: while we may call them coffee beans, the “beans” that give us our favorite morning beverage are actually the seeds of a cherry fruit plant! None of this actually matters, but it does make a great argument for getting coffee in and passing it off as a serving of fruit (mostly kidding… of course).
Speaking of coffee, caffeine is a widely used supplement among strength- and performance-oriented athletes and a very common ingredient to see added into food/beverage items as well. It helps us improve our focus and alertness, gives us an energy boost, and it can even act as a slight appetite suppressant for dieters.
We just released a podcast on caffeine use and abuse as well! Check it out here.
Caffeine can be very useful in and out of dieting phases (depending on the context), although the literature does appear to be a little conflicting regarding its real impact on performance and strength measures. Some studies show positive changes while others don’t show much change at all. In addition to this, most of the research has been done on trained and untrained men, so the present study will give us some novel insight on caffeine and its impact on resistance-trained women!
Prior findings
Research has shown us that a low-moderate dose of caffeine (approximately 3-6 mg/kg) is beneficial for sustained endurance performance and high-intensity bouts of exercise. Strength and power performance, however, is where the findings become more equivocal, showing either positive benefits or no changes at all for performance enhancement. There are more factors at play worth discussing with these findings, but given the prior discoveries of using low-moderate dosages, Goldstein and colleagues (2010) went forward with using the higher end of this range for the current investigation as a practical baseline for the subjects.
The study
15 resistance-trained females participated in this study. The study itself was made to be a placebo-controlled crossover design which basically means that each subject will have the chance to experience both testing protocols being used here. These two testing protocols include: a caffeine group who received a dose of 6 mg/kg, or a placebo group (PL). Both of which would be given about 60 minutes before testing (in a randomized order).
It was established beforehand that the women in the study would need to have participated in resistance training for at least 3-5 days per week for the past 6 months immediately prior to the study period. One other point was made to include women who can bench press approximately 70% of their relative body weights. This just reassures the investigators that the women being studied are more experienced trainees and have some background with strength training as well, as to not greatly skew outcomes and/or to mitigate limitations where they can.
As for general lifestyle habits, the women were instructed to continue with their typical exercise and nutritional habits during the week prior as well as throughout the exercise testing sessions. 3-day dietary recalls were also collected in order to verify the consistency of their diets.
Testing
Subjects reported to the lab on three separate occasions. The first being for a familiarization session where the subjects were instructed on proper technique and execution of the bench press movement. The remaining two sessions to follow were the actual testing trials for the study, where the subjects reported to the lab for training in the morning fasted (without food) for 12 hours. These two trials were placed seven days apart and the women were told to avoid any vigorous activity and the overconsumption of caffeine (via food or drink) in the 24-hour period leading up to testing. Finally, 60 minutes before training the doses of either caffeine or placebo would be administered to the subjects. The placebo control being used to replace the use of the caffeine supplement was a serving of flavored water (Propel brand).
As for the two training sessions undergone for testing, the women were put through assessments to determine their respective 1RM, or 1 repetition maximum, as well as testing repetitions to failure (RF) at 60% of that estimated 1RM for the barbell bench press.
Results
The major finding of this study was the that acute caffeine supplementation is found to enhance maximum strength performance in resistance-trained females, a question that no other studies have specifically sought to answer. Post-testing, the researchers observed a significant increase in barbell bench press maximum with caffeine. As for repetitions to failure at 60% 1RM, there were no stark differences seen between the two protocols.
Using a moderate dosage of caffeine seemed to be an appropriate call, as individuals are likely to have varying responses and symptoms from caffeine ingestion. This ties into previous research indicating a level of diminishing returns (i.e. more does not equal better), or simply the differing levels of habituation among the subjects (those who drink caffeine regularly versus those who do not). With this in mind, it is good to note the ranges of the participants’ caffeine consumption here, which seemed to be evenly split. Caffeine intakes ranged from 0-416 mg per day with eight of the women consuming < 250 mg per day, and the remaining 7 consuming > 250 mg per day.
Application to you
There are some limitations to keep in mind when interpreting these results such as the small sample size and the fact that inclusion criteria (bench press strength, training history, etc.) that was definitely more strict/narrow than most studies. With that said, these findings are specific to trained women (and the upper body performance of women to be exact).
When working with clients, whether they are dieting specifically for a show or working on lifestyle habits, it is always a good idea to gauge how much caffeine we’re intaking. For dieters, caffeine can be a very useful tool to keep in our back pockets as we get deeper into the dieting phase and energy levels dip lower than normal. It can help keep us energized and focused day to day, and even suppress our appetite a bit. Especially where training intensity is concerned, prioritizing caffeine consumption at the times we’ll need it most can make a huge difference in performance while in prep and ensure that we’re still getting the most out of our sessions (despite the lower food, slower recovery, and so on.)
As for lifestyle clients, we’re in a better position where we’re: 1. not dieting to extreme levels, and 2. should have ample fuel to keep us energized through our days so we won’t have to rely on caffeine as much. Caffeine can still be useful here, though, for those tougher/heavier training sessions we may have coming up in order to get an extra energy boost. More often than not it will come down to balancing this intake day to day based on how the client feels. For example, keeping tabs on any adverse symptoms like jitters/heightened anxiety, sleep quality/quantity changes, and so on.
Overall acute caffeine supplementation is a great way to aid in our dieting efforts and keep our output and training intensity where we need it most! We just need to keep our individual responses/symptoms and goals in mind when gauging that intake. Plus, we all (or most of us!) have those little morning rituals that just wouldn’t feel right without it.
References
Goldstein E., Jacobs, P.L., Whitehurst, M., et al. Journal of the International Society of Sports Nutrition. 2010, 7:18.
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