How caffeine influences physical performance

<h3>Key takeaways:</h3><ul><li><strong>Caffeine is one of the most effective performance enhancers we have.</strong> Dozens of studies show benefits across endurance, strength, power, and repeated-effort sports.&nbsp;</li><li><strong>Endurance gets the biggest boost.</strong> Caffeine lowers rate of perceived exertion by about 6% and improves endurance time-trial performance by about 3% — enough to shave nearly a minute off a 30-minute cycling effort.</li><li><strong>Strength and power benefits show up at surprisingly low doses.</strong> In one study, as little as 76 mg (for a 185-pound person) improved one-rep max and muscular endurance.</li><li><strong>Dosing matters more than most people realize.</strong> For most workouts, 50 mg taken 15 minutes before you start lands peak effects mid-session — exactly when you want them. For multi-hour endurance events, smaller doses every 60 to 90 minutes beat a single front-loaded hit. For afternoon workouts, keep it low (25–50 mg) to protect your sleep.</li></ul><p><br></p><p>Caffeine is <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC5867441/#:~:text=Supplements%20claiming%20to%20directly%20or%20indirectly%20enhance%20performance%20are%20typically%20the%20largest%20group%20of%20products%20marketed%20to%20athletes%2C%20but%20only%20a%20few%20(including%20caffeine%2C%20creatine%2C%20specific%20buffering%20agents%20and%20nitrate)%20have%20good%20evidence%20of%20benefits." rel="noopener noreferrer" target="_blank">one of the most reliable supplements</a> we have for improving endurance, strength and power, and high-intensity output, and like <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#:~:text=Reports%20on%20over,rowing%20%5B116%5D." rel="noopener noreferrer" target="_blank">75% of competitive athletes</a>, I’ve used it as a performance enhancing compound. If I’m dragging in the afternoon for example, a quarter of a cup of coffee or an <a href="https://drinklmnt.com/products/lmnt-recharge-electrolyte-drink?variant=45073875599383" rel="noopener noreferrer" target="_blank">LMNT Lemonade Iced Tea</a> before my workout puts a little spring in my step to get me through.&nbsp;</p><p>Understanding how caffeine enhances performance can help you use it strategically, whether you’re grinding through long miles, chasing a deadlift PR, or pushing repeated bursts of effort in a team event.</p><p>One caveat worth flagging before we get into the research: <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#:~:text=Caffeine%20has%20consistently%20been%20shown%20to%20improve%20exercise%20performance%20when%20consumed%20in%20doses%20of%203%E2%80%936%E2%80%89mg/kg%20body%20mass." rel="noopener noreferrer" target="_blank">Many of the studies</a> on caffeine and athletic performance that I’m sharing use doses of 3 to 6 mg per kilogram of body weight, which for a 185-pound person works out to 252 to 504 mg. From two decades of coaching — from special forces to do-it-all parents — I’ve seen that 50 mg of caffeine per serving is plenty for even the hardest chargers.</p><h2>Caffeine and Endurance&nbsp;</h2><p>Caffeine’s strongest benefits show up in <a href="https://bjsm.bmj.com/content/54/11/681.long#:~:text=It%20seems%20that%20the%20magnitude%20of%20the%20effect%20of%20caffeine%20is%20generally%20greater%20for%20aerobic%20as%20compared%20with%20anaerobic%20exercise." rel="noopener noreferrer" target="_blank">endurance or aerobic exercise</a> like running or cycling, where large muscle groups sustain a rhythmic effort over time and fatigue accumulates gradually.&nbsp;</p><p><a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#Sec8:~:text=Caffeine%20has%20consistently%20been%20shown%20to%20improve%20endurance%20by%202%E2%80%934%25%20across%20dozens%20of%20studies%20using%20doses%20of%203%E2%80%936%E2%80%89mg/kg%20body%20mass%20%5B13%2C%20195%2C%20205%E2%80%93207%5D." rel="noopener noreferrer" target="_blank">Dozens</a> of studies show that caffeine <a href="https://www.sciencedirect.com/science/article/pii/S1440244018304596#bib0005" rel="noopener noreferrer" target="_blank">delays fatigue</a> signals, <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#:~:text=Indeed%2C%20a%20recent%20review,3%E2%80%89mg/kg%20servings." rel="noopener noreferrer" target="_blank">i</a>ncreases <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#:~:text=Indeed%2C%20a%20recent%20review,3%E2%80%89mg/kg%20servings." rel="noopener noreferrer" target="_blank">time to exhaustion</a>, and lowers your rate of <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#:~:text=A%20meta%2Danalysis,performance%20%5B12%5D." rel="noopener noreferrer" target="_blank">perceived exertion or effort (RPE)</a>.&nbsp;</p><p><a href="https://www.sciencedirect.com/science/article/abs/pii/S1440244018304596" rel="noopener noreferrer" target="_blank">One meta-analysis</a> found caffeine improved endurance time-trial performance — a measure of how quickly an athlete can cover a set distance at max effort — by about 3% compared to a placebo. That could look like shaving almost a minute off a cycling session that normally takes you 30 minutes. At the elite level, where races are often decided <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#Sec8:~:text=Less%20than%20a,an%20alluring%20opportunity." rel="noopener noreferrer" target="_blank">by margins well under 1%</a>, that’s a real advantage.&nbsp;</p><p><a href="https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1600-0838.2005.00445.x?saml_referrer" rel="noopener noreferrer" target="_blank">Another meta-analysis</a> found caffeine can lower the rate of perceived exertion (RPE) by about 6% during steady-state exercise. So if running at a decent clip would normally put you at a 7 out of 10 on the exertion scale, caffeine can bring that down to a 5, allowing you to sustain your overall effort longer.&nbsp;</p><p><a href="https://science.drinklmnt.com/did-you-know/how-caffeine-works-brain-perceived-energy" rel="noopener noreferrer" target="_blank">The mechanism</a> traces back to caffeine’s ability to <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#:~:text=Caffeine%20is%20believed,%2C%20170%5D." rel="noopener noreferrer" target="_blank">block adenosine receptors</a> (I talk about this in depth in “How caffeine works”):&nbsp;</p><ul><li>Adenosine is a chemical that builds up the longer you’re awake, especially with increased <a href="https://medicine.yale.edu/internal-medicine/pulmonary/news/national-sleep-week/good-sleep-recipe/#:~:text=Adenosine%20is%20a%20byproduct%20of%20cellular%20metabolism%2C%20so%20the%20more%20active%20and%20alert%20we%20are%20during%20the%20day%2C%20the%20more%20adenosine%20builds%20up%20in%20the%20brain.%20Exercise%20for%20example%20can%20increase%20brain%20adenosine%20levels%20and%20through%20stimulation%20of%20adenosine%20receptors%20promote%20sleep." rel="noopener noreferrer" target="_blank">physical activity and mental effort</a>.&nbsp;</li><li>When it binds to receptors in the brain, it slows neuronal firing and neurotransmitter release, <a href="https://www.sciencedirect.com/science/article/pii/S1440244018304596#sec0015" rel="noopener noreferrer" target="_blank">promoting drowsiness and fatigue</a>. In peripheral tissues like muscle, adenosine can accumulate during exercise, bind to receptors on sensory nerve endings, and contribute to exercise-induced <a href="https://journals.lww.com/nsca-jscr/fulltext/2008/11000/effects_of_caffeine_and_aspirin_on_light.32.aspx#:~:text=Adenosine%20concentration%20increases%20in%20the%20muscle%20during,the%20central%20governor%20theory%2C%20Noakes%20et%20al." rel="noopener noreferrer" target="_blank">pain</a>.&nbsp;</li><li>Caffeine <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC8467199/#:~:text=Caffeine%20is%20so%20close%20in%20structure%20to%20adenosine%20that%20it%20is%20able%20to%20bind%20to%20the%20receptors%20that%20are%20specific%20to%20adenosine%2C%20which%20plays%20an%20important%20role%20in%20understanding%20how%20caffeine%20acts%20in%20the%20human%20body." rel="noopener noreferrer" target="_blank">structurally mimics</a> adenosine and occupies those same receptors.&nbsp;</li><li>With adenosine blocked, <a href="https://www.sciencedirect.com/science/article/pii/S1440244018304596#sec0015" rel="noopener noreferrer" target="_blank">fatigue</a> and <a href="https://journals.lww.com/nsca-jscr/fulltext/2008/11000/effects_of_caffeine_and_aspirin_on_light.32.aspx#:~:text=Adenosine%20concentration%20increases%20in%20the%20muscle%20during,the%20central%20governor%20theory%2C%20Noakes%20et%20al." rel="noopener noreferrer" target="_blank">pain signals</a> are delayed, and neuronal firing ramps up. Neurotransmitters like dopamine and norepinephrine flow more freely, boosting alertness, motivation, and <a href="https://www.sciencedirect.com/science/article/pii/S0149763416300690" rel="noopener noreferrer" target="_blank">coordinated movement.</a>&nbsp;&nbsp;</li><li>The net result: Effort feels lower at the same intensity.</li></ul><p>Separate from its effects on adenosine, caffeine may also increase <a href="https://ascpt.onlinelibrary.wiley.com/doi/abs/10.1038/clpt.1984.195?sid=nlm%3Apubmed" rel="noopener noreferrer" target="_blank">beta-endorphins</a> — feel-good, pain-blunting chemicals — further reducing perceived exertion.</p><p>Individual variability is real here. How much of a boost you get from a given pre-workout dose of caffeine may depend on how much you usually consume. The <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#:~:text=for%20future%20research.-,Habitual%20caffeine%20intake,-The%20quantification%20of" rel="noopener noreferrer" target="_blank">research isn't unanimous</a>, but some studies suggest higher habitual intake may lead to less pronounced benefits.</p><p>The likely explanation: Chronic caffeine use may <a href="https://www.sciencedirect.com/science/article/pii/0024320583901194?via%3Dihub" rel="noopener noreferrer" target="_blank">increase the number of adenosine receptors</a> in the brain. More receptors to block means you need a larger dose of caffeine to achieve the same perceived effect — but the <a href="https://science.drinklmnt.com/did-you-know/how-caffeine-works-brain-perceived-energy" rel="noopener noreferrer" target="_blank">bigger the dose, the harder the landing</a>.</p><h2>Caffeine’s Impacts on Strength, Power, and Explosive Performance&nbsp;</h2><p>Caffeine delivers measurable gains in the weight room, during high-intensity interval training (HIIT), and in team sports. The right dose for you — at the right time —&nbsp;can improve:&nbsp;</p><ul><li><strong>Maximal strength: </strong>the most weight you can move in a single rep, which reflects the greatest force your muscles can produce</li><li><strong>Peak power</strong>: how fast you can apply that force — crucial for explosive movements</li><li><strong>Muscular endurance</strong>: the ability to sustain repeated muscular contractions against resistance.</li></ul><p>Again, these effects trace back to caffeine’s ability to <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC5839013/#:~:text=Motor%20unit%20recruitment%2C%20in,29%2C%2030%5D." rel="noopener noreferrer" target="_blank">block adenosine receptors</a>. In addition to curbing fatigue, reducing pain, and boosting motivation, this blockade <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC12845049/#:~:text=Consequently%2C%20its%20ergogenic,voluntary%20movement%20execution." rel="noopener noreferrer" target="_blank">increases the activity of motor neurons</a> in the brain and spinal cord that control muscle movement.</p><p>Stronger signaling between motor neurons and muscles boosts the <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC12845049/#:~:text=Consequently%2C%20its%20ergogenic,voluntary%20movement%20execution." rel="noopener noreferrer" target="_blank">recruitment and firing rate</a> of <a href="https://www.sciencedirect.com/topics/neuroscience/motor-unit" rel="noopener noreferrer" target="_blank">motor units</a> (each motor unit is a neuron and the muscle fibers it controls.) With more motor units active — and firing faster — <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC12845049/#:~:text=Consequently%2C%20its%20ergogenic,voluntary%20movement%20execution." rel="noopener noreferrer" target="_blank">muscles generate more force quickly</a>, and you move more efficiently.</p><h3>Max strength and muscular endurance (the weight room)</h3><p>Caffeine can modestly <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC11336343/" rel="noopener noreferrer" target="_blank">make resistance training feel easier</a>. Studies show it improves both strength ( your one-rep max, or the most weight you can lift in a single squat, deadlift, or bench press) and muscular endurance (how many reps you can perform before fatigue sets in)</p><p>You don’t need massive doses to see benefits. In <a href="https://www.sciencedirect.com/science/article/abs/pii/S089990072200017X" rel="noopener noreferrer" target="_blank">one study</a>, as little as 76 to 168 mg (for a 185-pound person) was effective.&nbsp;</p><p>These effects hold across <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC5839013/" rel="noopener noreferrer" target="_blank">upper-</a> and <a href="https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1686283/full" rel="noopener noreferrer" target="_blank">lower-body</a> movement, though some research suggests caffeine may be a bit <a href="https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1686283/full#:~:text=4.2.4%20Muscle%20group,the%20upper%20body" rel="noopener noreferrer" target="_blank">more effective</a> for <a href="https://www.sciencedirect.com/science/article/abs/pii/S089990072200017X" rel="noopener noreferrer" target="_blank">enhancing strength</a> in larger, lower-body muscle groups.&nbsp;&nbsp;&nbsp;&nbsp;</p><p>Both low- and high-habitual caffeine users <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC8199301/#:~:text=Habitual%20caffeine%20intake%20among,varying%20habitual%20caffeine%20intake." rel="noopener noreferrer" target="_blank">see these benefits</a>. <a href="https://science.drinklmnt.com/did-you-know/why-caffeine-tolerance-is-individual" rel="noopener noreferrer" target="_blank">Tolerance</a> may <a href="https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1686283/full#:~:text=Our%20observed%20effect,habitual%20caffeine%20consumption." rel="noopener noreferrer" target="_blank">blunt these effects</a> to an extent, but doesn't eliminate them.</p><h3>Explosive power and speed (short-burst athletes)</h3><p>Caffeine shines in sports that demand short bursts of all-out effort — sprinting, jumping, lifting, throwing, gymnastics.&nbsp;</p><p>The benefits show up most clearly in muscular power versus max strength. Specifically caffeine improves <a href="https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1686283/full#:~:text=Recent%20reviews%20suggest%20that%20caffeine%20may%20have%20a%20greater%20effect%20on%20muscular%20power%20%E2%80%93%20specifically%20movement%20velocity%20and%20power%20output%20%E2%80%93%20than%20on%20maximal%20strength%20during%20resistance%20exercise%20(13%2C%2014)." rel="noopener noreferrer" target="_blank">movement velocity</a> (how fast you move a load) and power output (a function of load and velocity combined).</p><p>A recent <a href="https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1686283/full" rel="noopener noreferrer" target="_blank">meta-analysis</a> found that caffeine improves barbell speed and average power output in lifts like bench presses and back squats across a wide range of loads — especially for lower-body movements and in people with low-to-moderate habitual caffeine intake.&nbsp;</p><p>It<a href="https://www.mdpi.com/2072-6643/17/21/3475?" rel="noopener noreferrer" target="_blank"> also boosts</a> peak power output and repeated sprint ability (RSA) — your capacity to perform multiple consecutive high-intensity sprints with minimal recovery — in both cycling and running.&nbsp;&nbsp;&nbsp;</p><h3>Repeated high-intensity efforts (team &amp; court sports)</h3><p>Caffeine is useful in sports defined by repeated bursts of high-intensity effort — the intermittent sprinting, hard cuts, jumping, and explosive contact that characterize a 1 to 2 hour tennis, soccer, rugby, basketball, or combat sports match.</p><p>A <a href="https://pubmed.ncbi.nlm.nih.gov/39168455/" rel="noopener noreferrer" target="_blank">2024 meta-analysis</a> found that pre-exercise caffeine helped athletes perform more high-intensity actions — and succeed more often — during competition. In one of the included studies, soccer players who consumed 3 mg/kg of caffeine (252 mg for a 185-pound athlete) before a match completed an average of 30 sprints versus 24 in the placebo group — a meaningful gap at match intensity.</p><p>This benefit may even extend beyond sports to physically demanding jobs like <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC11204757/#:~:text=A%20popular%20ergogenic,may%20be%20beneficial" rel="noopener noreferrer" target="_blank">firefighting</a> or construction that require endurance plus repeated bursts of effort, but more research is needed.</p><h2>Caffeine and Cognitive-Motor Performance&nbsp;</h2><p>Caffeine may sharpen cognitive-motor performance — how well your brain and body work together to respond to what's happening in your environment.</p><p>One <a href="https://www.sciencedirect.com/science/article/abs/pii/S0765159722000934" rel="noopener noreferrer" target="_blank">meta-analysis</a> found that 3-6 mg/kg caffeine about 60 minutes before exercise improved reaction time and agility in sports like soccer, taekwondo, and volleyball. <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#Abs1:~:text=Foskett%20et%20al.%20%5B,mg/kg%20%5B348%5D." rel="noopener noreferrer" target="_blank">Individual studies</a> also show better fine motor control and passing accuracy in soccer players.</p><p>Mechanism-wise, we're back to adenosine blockade. With those receptors occupied by caffeine, <a href="https://www.sciencedirect.com/science/article/pii/S0149763416300690" rel="noopener noreferrer" target="_blank">dopamine activity ramps up</a> — and you get the downstream benefits: sharper alertness, faster mental processing, better coordinated movement. Motor units also fire faster, so your muscles respond quicker. In any sport where split-second decisions decide the outcome, that's a real edge.</p><h2>Caffeine Dosing and Timing: Short vs. Long Workouts</h2><p>Most studies test the effect of a single moderate-to-large dose of caffeine taken <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#:~:text=Caffeine%20has%20consistently,an%20ergogenic%20effect." rel="noopener noreferrer" target="_blank">60 minutes before exercise</a>. But in the real world, ideal timing and dosing should be based on workout duration, along with your <a href="https://science.drinklmnt.com/did-you-know/why-caffeine-tolerance-is-individual" rel="noopener noreferrer" target="_blank">personal caffeine metabolism and tolerance</a>.&nbsp;</p><h3>For most workouts</h3><p><a href="https://www.sciencedirect.com/science/article/pii/S089990072200017X?via%3Dihub" rel="noopener noreferrer" target="_blank">50 to 100 mg</a> taken about 15 minutes before you start is enough to get the benefits without the jitters. "Caffeine's effects start to kick in about 15 minutes after you ingest it, then build to a peak around 60 minutes before slowly coming back down <a href="https://www.sciencedirect.com/science/article/pii/S2772417424000104#:~:text=The%20rate%20of%20caffeine%20metabolism%20differs%20greatly%2C%20with%20half%2Dlife%20ranging%20from%20about%202%20to%2012%C2%A0h%20%5B31%5D.%20The%20average%20half%2Dlife%20of%20caffeine%20is%20about%204%E2%80%935%C2%A0h%20in%20healthy%20adults%20%5B14%5D.%20The%20differences%20in%20half%2Dlife%20are%20due%20to%20genetic%20individual%20variation%20and%20other%20physiological%20and%20environmental%20factors." rel="noopener noreferrer" target="_blank">over several hours</a>," says endurance coach, ultramarathoner, podcaster, and LMNT Partner <a href="https://zachbitter.com/" rel="noopener noreferrer" target="_blank">Zach Bitter</a> — meaning peak effects land mid-workout, which is exactly when you want them.</p><p>If you typically workout in the afternoon, stick to lower doses. I usually cap it at about 25–50 mg — about a quarter cup of coffee or one stick pack of <a href="https://drinklmnt.com/products/lmnt-recharge-electrolyte-drink?variant=45073875599383" rel="noopener noreferrer" target="_blank">LMNT Lemonade Iced Tea</a> — but you may need less or slightly more. Dial it back if you notice it impacting your sleep.&nbsp;</p><p>For evening sessions, it’s best to skip it and prioritize sleep and recovery.</p><h3>Longer efforts call for a different approach&nbsp;</h3><p>For marathons, ultramarathons, century rides, or prolonged training sessions lasting several hours, smaller doses <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7777221/#:~:text=The%20most%20common,beneficial%20%5B196%5D." rel="noopener noreferrer" target="_blank">spread out</a>&nbsp;tend to work better than a single front-loaded hit.&nbsp;</p><p>“With an ultramarathon where the intensity is pretty low, you don’t necessarily want that big hit of stimulation,” says Bitter. “You want something stable, where you can maintain a perceived effort at a set pace and just lock it in. For me that’s usually 50–75 mg every 60–90 minutes.”&nbsp;</p><h2>Bottom Line on Caffeine and Physical Performance</h2><p>Caffeine is one of the most effective and affordable tools we have for improving physical performance. It can boost endurance, strength, power, and endurance, making it useful whether you’re logging miles, lifting weights, or competing on the court or field. That's a wide net —&nbsp;all pulled by a single mechanism: Block adenosine, and your nervous system can drive harder, longer, faster.</p><p>But just like with caffeine’s <a href="https://science.drinklmnt.com/did-you-know/how-caffeine-influences-mental-performance" rel="noopener noreferrer" target="_blank">cognitive benefits</a>, more isn’t necessarily better. As you dial in your approach, keep in mind that <a href="https://science.drinklmnt.com/did-you-know/why-caffeine-tolerance-is-individual" rel="noopener noreferrer" target="_blank">caffeine metabolism and tolerance vary</a>. Your ideal dose and cutoff time may look different from someone else's. <strong>Start conservative, pay attention to how you respond, and adjust from there. That's how we get there with most things worth doing.</strong></p><p>Dose and timing are two of the three variables that shape your caffeine experience. The third is source — and it might matter more than you think. That's where we're headed next in <a href="http://science.drinklmnt.com/did-you-know/is-all-caffeine-same-why-source-matters" rel="noopener noreferrer" target="_blank"><em>Is All Caffeine the Same? Why the Source Matters.</em></a></p><p><em></em></p><p><em>This was the fifth article in our six-part caffeine education series. Want to read the other articles? Check them out below:&nbsp;</em></p><ul><li><a href="https://science.drinklmnt.com/did-you-know/how-caffeine-works-brain-perceived-energy" rel="noopener noreferrer" target="_blank">How caffeine works: The science behind perceived energy</a></li><li><a href="https://science.drinklmnt.com/did-you-know/why-caffeine-tolerance-is-individual" rel="noopener noreferrer" target="_blank">Why your caffeine tolerance is different from everyone else’s</a></li><li><a href="https://science.drinklmnt.com/did-you-know/caffeine-timing-dosing-cycling" rel="noopener noreferrer" target="_blank">Timing, dosing, and cycling: Personalizing your caffeine strategy</a></li><li><a href="https://science.drinklmnt.com/did-you-know/how-caffeine-influences-mental-performance" rel="noopener noreferrer" target="_blank">How caffeine influences mental performance</a></li><li><a href="http://science.drinklmnt.com/did-you-know/is-all-caffeine-same-why-source-matters" rel="noopener noreferrer" target="_blank">Is all caffeine the same? Why the source matters</a></li></ul>