Key Points

Caffeine is More Effective in the Morning: Caffeine consumption before morning workouts improves performance by closing the natural gap between morning and evening performance levels.
Avoid Evening Caffeine to Protect Sleep: Consuming caffeine in the evening doesn't significantly boost performance and increases the risk of sleep disruption, negatively affecting recovery and long-term progress.
Optimal Dose: 3–6 mg/kg of Body Weight: A dose of 3–6 mg/kg provides the best performance-enhancing effects while minimizing the risk of side effects like jitteriness and sleep disturbances.

Introduction:

I, like I assume many of you, cannot get through the day, let alone a workout, without an almost lethal dose of caffeine. Caffeine is the world's most widely consumed stimulant, fueling early morning risers and late-night workers alike. But how much does caffeine really impact your workout performance, and is there a "right" time to consume it?

As pre-workout supplements continue to gain popularity, caffeine is often the star ingredient, promising enhanced focus, energy, and strength. Yet, recent research reveals that the effectiveness of caffeine on performance might depend on factors like the time of day and how much caffeine you're consuming. A growing body of evidence suggests that while caffeine can indeed help you lift more or run faster, it’s not a magic bullet. The effects may be far more nuanced than many believe, especially when considering sleep disruption and potential side effects.

In this post, we’ll dive into the science of caffeine and exercise performance. Drawing from a recent study on how caffeine affects athletes at different times of the day, we’ll explore whether it’s more beneficial to drink your caffeine fix in the morning or evening and how much of a performance edge you can expect. Additionally, we’ll look at the potential downsides of evening caffeine consumption, including its impact on sleep and recovery.

The Science of Caffeine and Exercise Performance

At its core, caffeine operates by blocking adenosine receptors in the brain, thereby reducing feelings of fatigue and enhancing alertness. This inhibition leads to an increase in the activation of the central nervous system, which can improve muscle fiber recruitment during exercise, particularly in maximal and submaximal muscle contractions (1)(2). As a result, caffeine has been shown to enhance muscle endurance, movement velocity, and overall physical performance in both strength and endurance exercises.

Meta-analyses of caffeine’s effects have consistently demonstrated ergogenic (performance-enhancing) effects, particularly in aerobic endurance activities (2)(3). Caffeine has been shown to improve performance across various modalities, from aerobic endurance and sprinting to jumping and resistance exercises (3). Its benefits are well-documented at doses of 3–6 mg/kg, making it an attractive option for athletes of all levels (1)(3). However, the time of day when caffeine is consumed, along with the dosage, can greatly influence its effectiveness and potential side effects.

RECENT FINDINGS: Morning vs. Evening Caffeine Administration

Bougrine et al. (2024) conducted a study specifically to understand the impact of different caffeine doses on performance when consumed in the morning versus the evening. The study involved 15 young, well-trained female handball players, who were given either a placebo, 3 mg/kg of caffeine, or 6 mg/kg of caffeine before performing a series of physical tests. These tests included countermovement jumps (CMJ), modified agility T-tests (MATT), and repeated sprint ability (RSA) tests (4).

The results showed that caffeine had a significantly more positive impact when consumed in the morning compared to the evening. In the morning, a 6 mg/kg dose of caffeine improved performance across all tests more than a 3 mg/kg dose. However, neither dose improved evening performance to the same extent. In fact, caffeine consumed in the evening did not significantly enhance performance compared to the placebo, and it also came with a higher incidence of side effects, particularly insomnia, tachycardia, and headaches (3)(4). This suggests that caffeine’s ergogenic effects are more pronounced when consumed earlier in the day, likely due to the body's circadian rhythms and the tendency for evening caffeine to interfere with sleep.

Why Caffeine Works Better in the Morning

One of the most intriguing findings of this study was that caffeine supplementation in the morning seemed to close the performance gap between morning and evening tests. Typically, athletes perform better in the late afternoon or evening compared to the early morning (3)(5). This is due to circadian variations in body temperature, neuromuscular function, and hormone levels, all of which peak later in the day. When caffeine was consumed in the morning, it helped to mitigate these morning performance deficits, bringing morning performance closer to the levels usually seen in the evening (3).

This aligns with other studies that have found caffeine to be more effective in the morning for boosting performance. For instance, caffeine has been shown to improve endurance performance more significantly when consumed in the morning (3)(5). These effects can be attributed to the fact that morning exercise often suffers from neuromuscular impairments that caffeine can help overcome, as well as the fact that caffeine may be metabolized more efficiently in the morning(3)(4).

Evening Caffeine: The Drawbacks

The primary drawback of evening caffeine consumption is its potential to disrupt sleep, which is crucial for recovery and long-term athletic performance. Bougrine et al. (2024) found that participants who consumed 6 mg/kg of caffeine in the evening reported significantly more side effects, including insomnia, headaches, and gastrointestinal issues (4). These side effects not only reduce the quality of sleep but can also impair next-day performance, undermining any short-term gains achieved by caffeine consumption (3).

Moreover, caffeine appears to be less effective in the evening, likely due to the body’s natural circadian rhythms. As performance typically peaks in the evening naturally, the added benefit of caffeine is reduced, and the risk of side effects increases (4). This is particularly concerning for athletes who rely on regular, high-quality sleep for recovery and long-term progress (5).

Dosage Matters: 3 mg/kg vs. 6 mg/kg

The dosage of caffeine is another critical factor in determining its effectiveness and potential side effects. While 3 mg/kg of caffeine was effective in improving performance in some morning tests, the 6 mg/kg dose provided more consistent and pronounced benefits (3)(4). However, higher doses of caffeine are associated with an increased risk of side effects, especially when consumed later in the day.

Interestingly, studies suggest that the lower boundary for effective caffeine dosing lies around 2 mg/kg, but the benefits are less consistent at this dose (1). For most athletes, a dose of 3–6 mg/kg is ideal for maximizing performance while minimizing side effects. It’s also important to note that individuals may respond differently to caffeine based on their genetics, habitual caffeine intake, and tolerance (3).

Real-World Implications: When and How to Use Caffeine

So, how can athletes and fitness enthusiasts apply these findings to their training? First and foremost, it seems that if you’re going to use caffeine to enhance your performance, the morning is the best time to do so. Caffeine can help mitigate the natural performance dip that occurs in the morning, bringing your performance closer to what you might achieve later in the day. However, if you train in the evening, it might be best to skip the caffeine. While it may provide some short-term benefits, the risk of sleep disruption and the resulting negative impact on recovery and next-day performance likely outweighs the benefits (3)(4).

For those who do train in the evening but still want to use caffeine, a lower dose of around 3 mg/kg may provide a small boost in performance without severely impacting sleep. However, it’s still important to monitor how your body responds to caffeine and to adjust your intake accordingly (5).

Conclusion: Is Caffeine Worth It?

Caffeine can be an effective tool for enhancing exercise performance, but its efficacy depends on the time of day it is consumed and the dose taken. Morning caffeine consumption, particularly at a dose of 6 mg/kg, has been shown to improve performance across various physical tasks, including: jumping, sprinting, and agility tests. However, caffeine’s ergogenic effects are diminished in the evening, and the likelihood of negative side effects, particularly sleep disruption, increases.

For athletes who train early in the day, caffeine can be a valuable aid in overcoming the natural morning performance dip. However, evening exercisers may want to avoid caffeine or use it sparingly to avoid disrupting their sleep and hindering long-term progress. Ultimately, caffeine remains one of the most widely used and well-researched supplements in the fitness world, but like any tool, it works best when used strategically.

Sources:

Giráldez-Costas V, Ruíz-Moreno C, González-García J, Lara B, Del Coso J, Salinero JJ. Pre-exercise Caffeine Intake Enhances Bench Press Strength Training Adaptations. Front Nutr. 2021 Jan 26;8:622564.
Grgic J, Grgic I, Pickering C, Schoenfeld BJ, Bishop DJ, Pedisic Z. Wake up and smell the coffee: caffeine supplementation and exercise performance-an umbrella review of 21 published meta-analyses. Br J Sports Med. 2020 Jun;54(11):681–8.
Guest NS, VanDusseldorp TA, Nelson MT, Grgic J, Schoenfeld BJ, Jenkins NDM, et al. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021 Jan 2;18(1):1.
Bougrine H, Ammar A, Salem A, Trabelsi K, Żmijewski P, Jahrami H, et al. Effects of Different Caffeine Dosages on Maximal Physical Performance and Potential Side Effects in Low-Consumer Female Athletes: Morning vs. Evening Administration. Nutrients. 2024 Jul 11;16(14):2223.
Pickering C, Grgic J. Caffeine and Exercise: What Next? Sports Med. 2019 Jul;49(7):1007–30.

DISCLAIMER

The information in this article is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider or medical professional before beginning any new exercise, rehabilitation, or health program, especially if you have existing injuries or medical conditions. The assessments and training strategies discussed are general in nature and may not be appropriate for every individual. At Verro, we strive to provide personalized guidance based on each client’s unique needs and circumstances.