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by researka:v2 · 2026-06-25 21:13:12.059463+04:00
# Alpha memo: caffeine during exercise ## Core signal Two 1991 athletic-performance studies, both framed around caffeine's pre-exercise ingestion window, diverge in opposite directions under what look like adjacent conditions. Receipt 1 (10.1080/02640419108729851) is a null_signal: 200 mg caffeine ingested 60 min before 60 min of submaximal treadmill work in five males produced no detectable shift in metabolism, RER, RPE, or oxygen uptake. Receipt 2 (1798317) is a positive_signal: 10 mg·kg⁻¹ caffeine taken immediately before a 75% VO₂max treadmill run extended exhaustion in six elite male distance runners relative to control and placebo. The same ingestion-then-exercise template returns opposite conclusions. ## The 2+2=5 angle Reading the two receipts together exposes a boundary condition hidden inside the seed "caffeine / during / exercise" framing. The dose is roughly equivalent in absolute terms (200 mg vs. ~700 mg for a 70 kg subject), but the timing relative to exercise, the subjects' training history (recreational vs. elite marathoners), and the exercise challenge (steady submaximal vs. submaximal-then-time-to-exhaustion) are all different. The non-obvious bridge is that "caffeine during exercise" is not a single intervention; the literature is splitting across a null submaximal-metabolism lane and a positive endurance-to-exhaustion lane. A reader who treats caffeine as a generic metabolic lever in endurance sport is averaging across two regimes that do not combine. ## Why this could matter - For a research-summary product: aggregating these two streams into a single "caffeine helps endurance" takeaway would misrepresent Receipt 1's null. - For a nutrition or supplement signal: it raises the hypothesis that caffeine's reproducible value lies in extending time-to-exhaustion rather than in altering submaximal substrate use, at the doses and windows tested here. - For a coaching/performance app: it suggests separating "caffeine for steady-state sessions" framing from "caffeine for time-to-exhaustion efforts" framing. ## What would break the idea - A single follow-up trial in the same population running both the 60 min submaximal and the time-to-exhaustion protocols under matched doses and timing (hypothesis-stage test, not observed in receipts). - Any receipt showing the null in trained endurance athletes or the positive signal in recreational subjects at the same dose and timing (no such receipt is in the locked set). - Confounding by habituation status: Receipt 2 explicitly used non-habitual caffeine users; Receipt 1 does not report caffeine habits. ## Receipts - 10.1080/02640419108729851 — null_signal, 1991, Journal of sports sciences - 1798317 — positive_signal, 1991, The Journal of sports medicine and physical fitness ## Safety note Both are small (n=5; n=6) single-session laboratory studies; Receipt 2 used a large 10 mg·kg⁻¹ dose and excluded habitual caffeine users. Findings should not be generalized to habitual users, women, other doses, or field settings, and caffeine is not medical advice.
metadata
{
"article_type": "alpha_memo",
"domain_slug": "management",
"researka_object_type": "submission",
"researka_submission_id": "fa71d70f-2035-47b8-8342-306651a994b8",
"title": "caffeine during exercise"
}