Each week in my Research Update, I distill the latest sports science research into three practical insights to help you improve your training, performance, and recovery.
In this week's update:
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Whether daily caffeine use reduces the performance boost from a race-day dose
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What nutrition can (and can’t) do to help you handle extreme heat
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The 5 most evidence-backed performance supplements, and the doses that work
Does Your Daily Coffee Habit Cancel Out Race-Day Caffeine? Mostly, No
This review tackled a question a lot of habitual coffee-drinking endurance athletes ask: does regular caffeine intake blunt the performance boost from a pre-race caffeine dose?
Searching literature from January 2020 to June 2026, the authors found that acute caffeine (the standard 3–6 mg/kg dose) consistently enhances endurance performance. The largest relevant meta-analysis (44 randomized placebo-controlled studies) found mean power output improved 2.92% and time-trial completion time improved 2.26% versus placebo, and critically, that pooled effect wasn't significantly reduced by habitual intake.
That said, some longitudinal data suggest repeated daily exposure can partially blunt the size of the benefit over time in certain individuals, without eliminating it. This is a "partial, context-dependent habituation" rather than a hard tolerance wall. Genetics, dose, timing, and delivery form all still shape how much any one athlete responds.
Why it matters:
This is a direct, practical answer to something we get asked constantly: no, being a regular coffee drinker doesn't mean your race-day caffeine strategy stops working, though the effect may be somewhat smaller for very habituated users.
My thoughts:
This is a good one to point people to when they ask if they should "cycle off" caffeine before a big race to make it hit harder. The honest answer from this review is that it's probably not necessary for most people, since the pooled data shows the effect holding up in habitual users. Though, if you're someone who drinks caffeine constantly all day and feels like race-day doses aren't doing much, the individual variability angle here is worth exploring with a short trial period rather than assuming caffeine just "doesn't work for you."
Nutrition Can Help You Handle a Heatwave, but It's Not the Main Defense
This review synthesized evidence across climate-health, physiology, and nutrition research on dietary and hydration strategies for coping with extreme heat, relevant to anyone training or working outdoors through increasingly common heatwaves.
Regular water intake is described as the single most strongly supported strategy; most healthy people don't need routine electrolyte supplementation on top of adequate fluid and food intake, though athletes and outdoor workers sweating heavily may benefit from it. Water-rich foods (fruit, vegetables, soups, dairy) support hydration but shouldn't replace plain water, alcohol should be limited, and sugary drinks shouldn't be a primary hydration source.
The review is candid that direct heatwave-specific intervention studies are sparse, and much of this, including the Mediterranean-diet angle, rests on physiological plausibility rather than trials that tested heat tolerance directly.
Why it matters:
For runners, cyclists, and hybrid athletes training through summer heat (or planning a hot-weather race), this is a reasonable, unglamorous checklist and a reminder that nutrition supports, rather than replaces, actual cooling strategies.
My thoughts:
Nothing here overturns what most of us already do: drink consistently, don't over-rely on sugary sports drinks as your main fluid source, and use electrolytes when you're genuinely sweating heavily rather than as a default. The honest caveat about weak direct evidence is worth keeping in mind, so treat this as sensible practice, not proven heat-protection science.
5 Supplements With Real Evidence Behind Them and the Doses That Work
This review published in NASM's new Journal of Fitness, Wellness, and Human Performance synthesized the mechanistic and applied evidence behind the 5 most evidence-backed ergogenic aids in sports nutrition: caffeine, sodium bicarbonate, dietary nitrates, creatine, and beta-alanine.
Each gets its own dosing protocol and performance focus:
- Caffeine (3–6 mg/kg, taken 30–60 minutes before exercise) consistently improves endurance performance, cuts perceived exertion, and sharpens vigilance and reaction time.
- Sodium bicarbonate (0.2–0.3 g/kg) helps most in high-intensity efforts lasting 30 seconds to 12 minutes, though GI distress is a common limiter.
- Dietary nitrate (8–16 mmol) lowers the oxygen cost of exercise and extends time to exhaustion, especially in recreationally active people, but the effect is less noticeable in elite athletes.
- Creatine increases muscle phosphocreatine content by roughly 10–40% depending on baseline levels, dosing, and loading strategy.
- Beta-alanine (3.2–6.4 g/day for 4+ weeks) raises intramuscular carnosine and delays fatigue specifically in high-intensity efforts lasting 1–4 minutes, with little effect on very short or very long continuous efforts.
Why it matters:
Four of these five ingredients (caffeine, nitrate, creatine, beta-alanine) are core to our product lineup, and this review is a clean, single-source confirmation of the dosing windows and performance domains the research actually supports for each. This is useful as a sanity check against claims that stretch beyond the evidence.
My thoughts:
What I like about this one is how specific it stays. It doesn't just say "these supplements work," it tells you which effort duration and dose range the evidence actually covers. If there's one takeaway to repeat to others, it's that beta-alanine and dietary nitrate both have a fairly narrow effort-duration sweet spot (1–4 minutes for beta-alanine, extended sub-maximal efforts for nitrate), while caffeine and creatine are more broadly useful across effort types. Worth bookmarking as a reference the next time someone asks "how much of X should I actually take?" so you can help them out.
— That's all for now, train hard!
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