SYNTH-100 · Guide

Smoking, heated tobacco, vaping, hookah and nicotine

Smoke right before a session costs oxygen and time, a hookah can reach the next morning, heated tobacco and vapes add less CO and nothing shown buys speed; say it once, read heart rate and HRV in that light; race week is a poor first day without nicotine, but wanting to stop always wins; hour windows and that rule are practice

Main caveat: Transfer. Every smoking, hookah and vaping number is from people not described as trained endurance athletes.

limited, mixed evidenceMostly from recreational to highly trained athletes

The question it answers

An athlete uses cigarettes, heated tobacco, a vape, a hookah or another nicotine product, or asks about them. What does each cost a session, a race and months of training; what do the hours between use and the session change; how are heart rate and HRV read; and what does the assistant say, once?

Short answer: ask what and when; smoke costs the session in front of it and a hookah can reach the next morning; heated tobacco and vapes add less CO than a cigarette and nothing has been shown to make the athlete faster; the windows are practice; numbers are read in that light; race week is a poor first day without nicotine (practice), yet wanting to stop now always wins; and whoever wants to stop is pointed to proven help.

What this guide owns and what it leaves

Owns (decided here)	Leaves to
What each product costs a session, a race and a season; the hours table; what the assistant says	Heart-rate anchors → SYNTH-38; the warm-up test → SYNTH-41; which device number to trust → SYNTH-91; the low-readiness ladder → SYNTH-30
Reading heart rate and HRV after smoke, nicotine or a hookah	Alcohol on the same evening → SYNTH-77; sleep and caffeine timing → SYNTH-07; supplements and caffeine dose → SYNTH-67
Nicotine in the heat and on race morning, as a caution	Heat acclimation and hot-race planning → SYNTH-04; illness, chest symptoms and the return → SYNTH-36
The one-line pointer for anyone who wants to stop	Quitting itself → a doctor or stop-smoking service; the base holds no entry on quitting products; medications and training → SYNTH-20, which has no cessation-drug row
One line on fractures and surgery	Injury rules → SYNTH-94 and SYNTH-73; the clinician leads

Default — the decision, in order (what to prescribe first)

Not from a study; the base's own practice for the order of steps, every hour window, the race-week rule and the wording; the sources say what each step rests on:

Ask what, how much and when, then say the cost once: no smoke for about 4 h before a key session or race, no hookah the evening before, nothing during; the hours are practice from half-lives. Product and timing decide the answer, as dose does in SYNTH-77 (B). Say it plainly, do not repeat it in later replies unless asked, and never make quitting a condition of help: state the trade and let the athlete choose (SYNTH-77).

The session decides how much it matters. Easy session: go ahead, judge it by effort and do not read the numbers. Key session or test inside the window: later in the day or another day if the week allows (SYNTH-26); if it stays, expect less and do not read the result as lost fitness.

The base shows the cost at maximal work (REF-1456, B) and at the maximal lactate steady state (MLSS) with CO alone (REF-1459, B+); it has no measurement at easy intensity, and "threshold goes first" or "key sessions suffer most" was not tested.

Moving the first cigarette of the day after a key morning session is the cheapest change for a daily smoker: the night is already a long gap (practice, from half-lives; nothing measured). Rehearse it on training days first, as a caffeine plan is rehearsed (SYNTH-67, its own practice), not first on race morning.

A craving in the session: keep moving, no smoke during it. In abstaining smokers a 5-40 minute bout cut the urge by about two standard deviations against sitting, rated right after or 5 minutes after (REF-1457, A-). Nobody rated it mid-session, in hard training or in athletes, so this is the nearest evidence, not a measured mid-ride effect.

Heated tobacco or a vape instead of a cigarette: less CO is supported, free is not. Ten puffs of IQOS or JUUL did not raise exhaled CO and the cigarette did (REF-1464, B); COHb was lower after switching in trials all funded by tobacco companies (REF-1463, A-).

Nicotine's own effects stay (REF-1471, B+), airway resistance rose after a vape, by a size of unknown meaning for exercise (REF-1473, B-), and none of it was measured before exercise in athletes.

Before a race the choice is the athlete's and the base offers no product as a swap; during a race, none: nothing was measured, no gain was found (REF-1461, B) and heat strain rose in non-users (REF-1462, B). Between stages use the hours table.

A hookah is the large CO dose. Not the evening before a key session or race; no session of any kind in the first hours after one, whatever step 2 says of easy sessions; the morning after is easy, or the key session goes later or a day on (practice, on REF-1458, B-, REF-1460, B, and half-lives). Headache, dizziness or nausea after a hookah is a red flag, not a session.

Read heart rate and HRV in that light. Ask about use before calling a number fatigue or lost fitness; compare only like with like, at the same time since last use (SYNTH-41, SYNTH-38); read HRV as a trend (SYNTH-91, SYNTH-30).

Smoke raised resting heart rate and lowered maximal heart rate (REF-1456), a nicotine vape raised resting heart rate (REF-1471), CO raised heart rate at MLSS (REF-1459), and heart rate per unit of oxygen rose after a hookah (REF-1468, B-). No entry measured HRV after tobacco: that part is practice, by analogy with alcohol (SYNTH-77).

Do not propose race week or race morning as a first day without nicotine (practice, not evidence); wanting to stop now always wins. It rests on the general course of withdrawal, which the base does not hold; REF-1469 (B) does not show it, because nobody exercised abstinent without snus.

It is a point about one race, not a reason to keep using: an athlete who wants to stop now is helped now (step 9) and the race comes second; one who asks when suits training hears "after the A race or in a base block, unless you would rather go sooner"; one who has already stopped is supported, never told to go back.

This is not a licence for a race dose: nicotine is never presented as a performance aid (REF-1461).

Whoever wants to stop gets a pointer, not a programme: a doctor or stop-smoking service has proven help; the assistant advises no product and no dose.

It can say what the training side has shown: 6-7 days off went with longer treadmill time and lower exercise heart rate in 11 young men, uncontrolled (REF-1467, B-), and men who stopped tracked non-smokers' fitness decline over 7.2 years (REF-1465, B+, observational). Dependence, or using to cope → the same pointer (SYNTH-77).

Injured and smoking: in mostly surgical fracture patients, current or former smokers had 2.5 times the odds of non-union, an association (REF-1470, A-); the clinician leads, and stress fractures are a transfer (no such data in that review).

The hours around a session — measured or estimate

MEASURED = a study measured this, at about this time, in the people named. ESTIMATE = nobody measured it: the base's practice from half-lives, and no cell marked ESTIMATE carries an entry's level. Half-lives: CO about 4 h at rest breathing air, nicotine about 2 h, the slow end of the 1-2 h that REF-1461's authors cite (REF-1464), so the nicotine left is an upper estimate.

These figures are common pharmacology, not measured by any entry in the base; the evidence map read them in two reviews outside it (Pan 2020, DOI 10.3390/ijerph17020528; Benowitz 2009, DOI 10.1007/978-3-540-69248-5_2; suggested level C+ for each if entered).

When	Cigarettes	Hookah	Vape / heated tobacco
Right before the session	MEASURED: smoke of 3 cigarettes, VO2max about −7%, time at VO2max −20%, resting heart rate up, maximal heart rate down, in 16 men; gap to the test not stated; one cigarette not tested (REF-1456, B, truncated abstract). CO alone: REF-1459, B+	MEASURED: within 0.5 h of 45 min, CO level 3.7 to 24.4 ppm, VO2 1.86 to 1.7 L/min, oxygen pulse 10.89 to 9.97 mL/beat, effort harder, in 24 young men (REF-1468, B-, pilot). COHb 2.0% to 17.6% after 30 min (REF-1458, B-)	MEASURED, markers only: 10 puffs, no exhaled CO rise; plasma nicotine 62% (IQOS) and 48% (JUUL) of a cigarette's, about 55% ad lib (REF-1464, B); nicotine vape, resting heart rate SMD 0.71 (REF-1471, B+). Performance right before: not measured. Nearest, ~55 min after a vape in non-smokers: VO2peak 2.3 vs 2.3 L/min (REF-1472, B)
3-4 h before	ESTIMATE: about half of the CO that smoke added and a quarter to a third of the nicotine are left. A key session can go ahead with less expected of it; longer is better. Performance not measured	ESTIMATE: half of a large dose is still large; arithmetic from REF-1458's mean gives COHb about 10%, with a wide spread. No hard session. Performance not measured	ESTIMATE: less CO to clear than after a cigarette, not none (REF-1463); a quarter to a third of the nicotine left. No CO window is set, which does not make it safe; resting heart rate may still read high. Performance not measured
A day before	ESTIMATE: by half-life arithmetic little of that use's CO and nicotine is left, though the same nicotine review reports a slow 11-h tail at low levels and build-up over a day of regular use. A daily smoker's cost comes from the next ones, not this one. Performance not measured	MEASURED, marker only: exhaled CO still raised 10 h after, size not stated, in 32 students (REF-1460, B). ESTIMATE: about a sixth of the added CO at 10 h, little by 24 h; next-morning performance not measured. Morning after: easy, or key session later	ESTIMATE: little of that use's nicotine is left by half-life arithmetic, so no timing rule; regular use is the next row. Performance not measured
Regular use vs none	MEASURED, associations: 4,358 male 16-km racers, slower with training controlled, coefficient 0.10 (REF-1466, B+); men 40-59 over 7.2 years, fitness −217 vs −86 J/kg (REF-1465, B+, abstract). 6-7 days off: longer treadmill time, lower exercise heart rate, VO2max unchanged (REF-1467, B-)	No entry in the base. ESTIMATE: repeated large CO doses, read with the cigarette column; say it is not measured here	MEASURED, vape, one-time comparison: 26 low-fit young users vs 16 non-users, VO2peak 27.9 vs 32.3 mL/kg/min, absolute 2.0 vs 2.2 L/min not different, no link with cotinine or years of use (REF-1474, B). Heated tobacco: no fitness entry; COHb lower than continued smoking, about 52% overall and about 21% at ≥ 4 weeks, our back-calculation (REF-1463, A-, industry-funded)

Reading it: the half-life arithmetic assumes rest, air and one episode.

A half-life at rest is not one during exercise or on oxygen: CO clears faster with faster breathing and far faster on oxygen, and more slowly with more haemoglobin mass (outside the base, from the evidence map: Zavorsky 2012, DOI 10.1249/MSS.0b013e3182602a00; Zavorsky 2014, DOI 10.14814/phy2.12237), so 4 h is no clock, and neither easy movement nor oxygen is offered as a way to clear a session.

The arithmetic covers CO and nicotine only, not the breathing cost the authors assign to smoke particles (REF-1456). It says nothing about how much of the session comes back at a given hour, because the base holds no COHb level for a given performance cost (REF-1459 gives none). The rows are a way to talk about timing, never a promise that a session is clear.

Red flags — when it is not a tobacco question

Chest pain, palpitations, dizziness, a resting heart rate that will not settle, or breathlessness out of proportion to the effort → stop, a doctor (PHYS-12, PHYS-15, base practice; SYNTH-36). In a smoker these are never put down to the cigarette.

Headache, dizziness, nausea, confusion or collapse after a hookah → possible CO poisoning: stop, fresh air, a doctor; collapse or confusion, emergency services. No session and no training through it (the base's own practice; REF-1458 gives the dose, not a threshold).

Wheeze, chest tightness or a recurrent cough after sessions → a clinician (PHYS-15; REF-607, C+, screens recurrent post-session cough or wheeze for exercise-induced bronchoconstriction).

Nausea and chills, or confusion, in a hot race → stop and get medical help, whatever the cause; confusion or collapse, emergency services; one man left a hot nicotine trial with nausea and chills at 39.7 °C (REF-1462, B; the stop rule is practice).

Fever or any symptom below the neck → SYNTH-36, unchanged.

Dependence, using to cope, or repeated failed attempts → a doctor or stop-smoking service, as SYNTH-77 refers alcohol dependence.

Key Findings — what the evidence shows

Smoke costs more than its CO at maximal work. VO2max fell about 7% with the smoke of 3 cigarettes and with CO to the same saturation; time at VO2max fell 20% against 10%; resting heart rate rose and maximal heart rate fell only after smoke, and peak lactate fell after smoke; the authors assign the extra loss to the breathing cost of particles, which was not measured in what the abstract reports (REF-1456, B, 16 men, 1983, truncated abstract, no COHb).

VO2max is limited mainly by oxygen delivery (PHYS-09, established), which fits the CO part.

CO alone costs high-end and threshold-type work, and fitness does not protect. Against sham (ramp tests, n = 20): VO2peak −4.2%, peak power −3.3%, respiratory compensation point −6.3%; the gas exchange threshold change, −3.3%, was not significant (P = 0.077).

At MLSS (n = 16) heart rate, ventilation, peripheral fatigue and perceptual strain were worse and lactate went from 5.5 mM at 10 min to 6.8 at 30, drifting more than 1 mmol/L in 9 of 16, the fitter ones (VO2peak 66 vs 56 mL/kg fat-free mass/min); falls correlated with fitness at r −0.45 and −0.49 (REF-1459, B+, abstract).

CO by rebreathing in people not described as smokers, COHb not given.

One hookah is a large CO dose that outlasts the evening. COHb 2.0% to 17.6% (± 8.8) and plasma nicotine 1.2 to 18.8 ng/mL after 30 min in 47 young adults; endothelial function unchanged; no cigarette arm (REF-1458, B-).

Exhaled CO about 7.5-fold that of an indoor cigarette session with equal tobacco, lower outdoors, with cotinine comparable; still raised at 10 h, size not given and not that 7.5-fold (REF-1460, B, 32 students, marker only).

Half an hour after 45 min: lower VO2 and oxygen pulse, harder effort, resting systolic pressure 118.9 to 129.2 mmHg (REF-1468, B-, 24 young men, fixed order, 10-min test).

Heated tobacco and vapes spare CO against a cigarette; "none" is not settled. Exhaled CO rose only with the cigarette, 5.2 to 8.7 ppm after 10 puffs and to 16.6 after ad lib use; IQOS and JUUL stayed flat; plasma nicotine IQOS 12.7, JUUL 9.8, cigarette 20.4 ng/mL; craving fell with all three after 10 puffs; heart rate and blood pressure were recorded and not reported (REF-1464, B, 18 smokers new to both devices).

After switching, COHb was lower than with continued smoking (log mean difference −0.74, about 52% lower; −0.24, about 21% lower, at ≥ 4 weeks; I² 96%), 9 of the review's 11 RCTs, all 11 funded by tobacco companies, six with a clinic stay; against quitting all tobacco the COHb difference is very low certainty (REF-1463, A-).

Nicotine without smoke moves the numbers at rest, not visibly at effort. Nicotine vape, before vs after: heart rate SMD 0.71, systolic 0.38, diastolic 0.52, no significant spirometry change (REF-1471, B+, abstract, 919 people). Airway resistance about 0.04 kPa/(L/s) higher after 5 min in 30 smokers (REF-1473, B-).

About 55 min after 20 inhalations in 20 non-smokers: no clear change in VO2peak or peak power (201.0 vs 204.8 W), heart rate unchanged, resting diastolic pressure 3 mmHg higher (REF-1472, B). No heart-rate difference at about 170 beats/min in a time trial (REF-1461).

No nicotine product has been shown to buy speed. Ten well-trained cyclists (VO2peak 71 mL/kg/min) rode about 1 h in 62.9 min on 2-mg gum, 62.6 on a 7-mg patch and 63.3 on placebo (P = 0.73); typical error 2.5%, so a small effect is not excluded; non-users, 18-22 °C, and the gum delivered little (REF-1461, B).

Snus-using athletes lasted 24.1 vs 20.9 min at 80% VO2max when snus followed 12 h off rather than their usual state, with snus in both trials, so neither "withdrawal costs performance" nor "nicotine is ergogenic" was tested (REF-1469, B).

Nicotine adds heat strain, in non-users. At 30 °C an overnight 7-mg patch raised core temperature 0.4 ± 0.5 °C more than placebo (0.1 ± 0.7 °C at 20 °C), skin blood flow fell progressively, and 2 of 10 trained men did not finish the hot nicotine trial; no measured effect of nicotine on time-trial power, with the handling of the non-finishers not stated (REF-1462, B, abstract).

Habitual users are untested. Heat already gives the heart a second job (PHYS-28, established).

Moving lowers the urge. Strength of desire SMD −1.91 (−2.59 to −1.22), desire to smoke −2.03 (−2.60 to −1.46), 19 randomised trials, I² 92-94%, every study in the same direction; moderate exercise did at least as well; isometric exercise did least; light cycling did not differ from sitting (REF-1457, A-). Not a quit-rate result.

Regular smoking goes with slower races and faster loss; stopping points the right way. 16-km time slower with training controlled, coefficient 0.10, 6.9% regular smokers among the racers, and in 6,592 conscripts 12-min distance was inversely related to cigarettes a day and years of smoking (coefficient for smoking −0.14), apparent even in light smokers, a finding from conscripts, not racers; both coefficients are small (REF-1466, B+, survey).

Fitness −217 vs −86 J/kg and FEV1 −271 vs −116 mL over 7.2 years; 199 men who stopped tracked non-smokers (REF-1465, B+, abstract, healthy men 40-59). Young vapers: REF-1474, B, in the table, a gap that does not show in absolute VO2peak or peak work.

Bone and wounds. Non-union OR 2.50 (1.73-3.61), deep surgical site infection OR 2.04; delayed union and time to union not significantly different on small analyses; stopping at least 4 weeks before any surgery was associated with less wound infection than continuing (OR 0.37, 0.16-0.89); no cessation study in fracture patients met the criteria, and the only bone outcome listed for stopping is one spinal-fusion study (REF-1470, A-, mostly non-randomised, patients; "smokers" includes former smokers).

It does not show: any result in trained endurance athletes who smoke; performance 3-4 h or a day after any product; what one cigarette costs; how much COHb costs how much performance; that threshold is lost before VO2max, or that key sessions suffer most; that an athlete performs worse abstinent; any effect of heated tobacco on heart rate, breathing or performance; what a hookah does to sleep, HRV or muscle recovery; whether habitual users keep the nicotine heat effect; that smoke, snus, gum or a patch helps an endurance athlete; that fractures heal slower beyond non-union; anything about stress fractures.

Conflicts and how they are resolved

Nicotine and heart rate: up at rest, flat at effort. REF-1471 pools a rise at rest; REF-1472 (about 55 min after) and REF-1461 (self-paced, about 170 beats/min) found no difference at effort. Resolved: a nicotine vape shortly before a resting reading can shift it; no evidence that smoke-free nicotine moves heart rate at effort; smoke and CO do (REF-1456, REF-1459).

Airways: no significant spirometry change, resistance up. REF-1471 found no significant spirometry change, REF-1473 a small rise in airway resistance, measured differently, in smokers with an early device, with a size of unknown meaning for exercise. Resolved: say "a measured rise of unknown meaning for exercise", not "vaping narrows your airways"; lungs mostly have reserve (PHYS-15, well supported); symptoms go to a clinician.

Heated tobacco: "no CO" or "less CO"? REF-1464: no rise after 10 puffs and 90 min, in novices, with IQOS kits bought in 2017. REF-1463: lower than smoking, the gap shrinking from about 52% to about 21% at ≥ 4 weeks, and above abstinence only at very low certainty. Why it shrinks is untested (fewer clinic days and more cigarettes is one reading). Resolved: "less CO than a cigarette", never "no CO" and never "as good as not using".

Does snus help, or does abstinence hurt? REF-1469's authors read the longer time as snus relieving withdrawal; REF-1461 found no gain in non-users. Resolved: neither is shown; no race dose, and the race-week rule stands as practice, not as this trial's finding.

Passive hookah: small or large? COHb 0.8% to 1.2% in 15 passive participants (REF-1458) against exhaled CO in the range of active cigarette smokers (REF-1460). Different markers and unknown rooms. Resolved: sitting in the room is not zero and sets no session rule.

Authors' causal wording. REF-1466 "direct" effect and REF-1474 "reduces fitness" go further than one-time comparisons, the second with no link to dose. REF-1470's Discussion says stopping helps non-union and also that it had no effect on bone healing. Resolved: associations stated as associations; the 4-week result is wound infection only.

Readiness lists named alcohol and caffeine, not tobacco. SYNTH-38, SYNTH-41, SYNTH-91 and SYNTH-30 now add it, pointing here; PHYS-12 adds small acute studies beside its guideline-only line. Folded; no rule or level changed.

Caffeine clearance. REF-446 (C+, composite, no verified source) says smoking modifies CYP1A2 activity. No new entry sources it, so it stays as it was and this guide states it only with that label.

CO and altitude. Both end in less oxygen delivered (PHYS-09, PHYS-14, established), and the base holds CO rebreathing as a measurement of haemoglobin mass (REF-135, B; REF-464, B+) and as a laboratory dose (REF-1459). Resolved: none of that makes smoke or a hookah a training stimulus; every entry here records it as a cost.

Practical Application — how the assistant says it

"I smoked half an hour before training — what does that do?" Today's session costs more. In 16 men of unstated fitness, the smoke of three cigarettes took about 7% off VO2max and 20% off time at VO2max (REF-1456, B, abstract); one cigarette was not tested. Expect a higher heart rate and a harder feel. An easy session goes ahead by effort; a key one, if the day allows, goes later or tomorrow (the base's practice).

"I crave a cigarette in the middle of a workout." Keep moving. In abstaining smokers, short walks and rides cut the urge by about two standard deviations against sitting, rated just after (REF-1457, A-); nobody asked mid-session or in athletes. A moderate walk or spin counts; it need not be hard, but the one study of light cycling did not differ from sitting. The urge is a reason to keep going, not a verdict on you.

"Heated tobacco before a race, OK?" Your call; here is the trade. It adds less CO than a cigarette: 10 puffs did not raise exhaled CO in smokers new to the device (REF-1464, B), and COHb was lower after switching, in trials all funded by tobacco companies (REF-1463, A-).Nicotine stays, about 62% of a cigarette's plasma level after 10 puffs; heart rate after IQOS itself was not reported. Nobody has tested it before a race, and nicotine did not make trained cyclists faster (REF-1461, B). If it is your routine, race morning is a poor first morning without it and the further from the start the better; try that on training days first (practice).None of this says it helps you race, or that less CO is safe.

"And during the race — feed zone, transition, between stages?" Nothing has been measured, there is no gain to set against it, and in the heat nicotine raised core temperature and 2 of 10 non-users could not finish (REF-1462, B). So none during (practice). Between stages, the hours table applies.

"Hookah last night — what about today and my recovery?" Part of today may be CO. One indoor session took COHb from 2.0% to 17.6% in young adults (REF-1458, B-), and exhaled CO was still raised 10 h later (REF-1460, B). Nobody has measured the next morning's session, or sleep, muscle recovery or HRV after a hookah.So: easy this morning, or the key session later or tomorrow (practice), and read your heart rate and HRV as hookah. Headache, dizziness or nausea: a doctor, not a session.

"How much does smoking cost my fitness and race times?" No honest figure in seconds exists. Among 4,358 male 16-km racers, smokers were slower even with their lower training controlled, a small standardised association with no time attached (REF-1466, B+, a survey, no proof of cause).Middle-aged men who kept smoking lost 217 J/kg of bicycle-test fitness against 86 in non-smokers over 7 years, and those who stopped tracked the non-smokers (REF-1465, B+). No study has tested trained athletes who smoke; these racers are the nearest.

"Is a vape cleaner than a cigarette for training?" For the CO, yes; free or safe, no, and this answers the session, not your health. Nicotine still goes with higher resting heart rate and blood pressure, in pooled before-and-after data (REF-1471, B+).Young regular vapers had lower VO2peak per kg than non-users (27.9 vs 32.3 mL/kg/min), though not in litres or watts and with no link to how much they vaped, in low-fit people (REF-1474, B): a signal, not a verdict. Heated tobacco has no fitness data in the base.

"Do pouches, snus or gum make me faster? Is nicotine banned?" Nothing shows it: gum and a patch made no clear change to a 1-hour time trial in 10 well-trained cyclists, non-users, with small effects not excluded (REF-1461, B); pouches were not tested. The authors state it was not banned and was on WADA's Monitoring Program in 2019; the base does not hold the current list, so check it.

"My resting heart rate is up and my HRV down — is it the cigarettes?" It may be. Smoke and nicotine vapes raised resting heart rate (REF-1456; REF-1471), and CO raised it at the same work (REF-1459). No study in the base measured HRV after tobacco, so reading it this way is practice, as with alcohol (SYNTH-77).Compare days at the same time since your last use and look at the 3-day trend (SYNTH-91). A morning reading many hours after the last one may show little (inference): resting heart rate did not change after a week off in 11 young men (REF-1467, B-).A resting heart rate that will not settle, or comes with fever or chest symptoms, is not a tobacco question: SYNTH-36, a doctor.

"Should I quit in race week, or skip my usual on race morning?" If you want to stop now, stop now: that outranks the race, and a doctor or stop-smoking service can help. If it is only for the race, race week is a poor first test of days without it, and a morning without it is better tried in training first.That is the base's practice, not a finding: the nearest trial never tested athletes without nicotine (REF-1469, B). And nothing here says nicotine helps you race, or is a reason to keep using.

"I want to stop. How fast does it come back?" Good; a doctor or a stop-smoking service has proven help, and I will not advise a product or a dose. On the training side, the first thing to expect is heart rate at the same work: 11 young men had lower exercise heart rate and longer treadmill time after 6-7 days, with VO2max unchanged and no control group (REF-1467, B-).I can plan your training around it, and a lower heart rate that first week is not new fitness (inference).

"Does smoking matter for my fracture?" Probably, though cause is not shown. In mostly surgical patients, current or former smokers had 2.5 times the odds of a bone not healing (REF-1470, A-), though average healing time showed no clear difference on small analyses; stress fractures were not in that review.Before planned surgery, stopping at least 4 weeks went with fewer wound infections in mixed surgery, and no study tested stopping in fracture patients: raise it with your surgeon.

"Since I stopped, coffee hits harder." Possibly. The base has one unsourced line that smoking changes the enzyme that clears caffeine (REF-446, C+). Nothing here measures it; timing stays with SYNTH-07.

Say what the base cannot judge: any hour at which a session is clear; what one cigarette costs; a hookah's effect on sleep or muscle recovery; anything in trained athletes who smoke.

What NOT to do

Moralise, repeat the warning in every reply, or make quitting the condition of help (SYNTH-77's "state the trade").

Say "one cigarette doesn't matter", or give a cost for one cigarette: three were tested (REF-1456).

Present an hour window as a finding: "clear after 4 h" was never measured.

Present any nicotine product as a performance aid, or give a race dose (REF-1461; REF-1469).

Call heated tobacco or a vape harmless, "no CO" or "as bad as a cigarette for the session" (REF-1463; REF-1464; REF-1471).

Treat a hookah as lighter than a cigarette, or quote REF-1458's ">25%" and ">40%" as COHb levels: the abstract does not say what they mean.

Suggest that CO works like altitude training or builds blood, for smoke, a hookah or anything else (PHYS-14).

Read a heart rate or HRV shifted by smoke or a hookah as fatigue or lost fitness; or say that tobacco's HRV effect is measured in the base.

Say that threshold goes first, or that key sessions suffer most: not tested (REF-1459).

Say that an abstinent athlete performs worse, or that withdrawal has a measured performance cost (REF-1469).

Propose race week or race morning as a first day without nicotine, talk anyone who wants to stop now into waiting for the race, or sell that rule as evidence.

Recommend a cessation product or dose, or run a quit programme.

Say that fractures heal slower beyond non-union, or carry that result to stress fractures without saying it is a transfer (REF-1470).

Say that exercise helps people quit: the evidence is about the urge in the minutes after a bout (REF-1457).

Train through possible CO poisoning, or put a smoker's chest pain down to the cigarette.

Evidence gaps

Athletes: no study of a cigarette, heated tobacco, a vape or a hookah before exercise in trained endurance athletes; no training-response study in smokers.

The hours: no performance or physiology measured 3-4 h or 24 h after any product; no COHb level attached to a performance cost; whether easy movement shortens the window is not in the base.

Heated tobacco and vapes: no heart-rate or breathing data for heated tobacco in the base; nothing during exercise; devices have moved on since REF-1464 and REF-1473.

Hookah: next-morning performance, sleep, HRV, muscle recovery and regular use against fitness have no entry.

Readiness: no entry on HRV or overnight resting heart rate after tobacco.

Withdrawal: no trial of athletes abstinent without nicotine; the general course of withdrawal is not in the base.

Heat: habitual users, women, pouches and vapes untested (REF-1462).

Quitting: no entry on behavioural support, medicines, nicotine replacement or e-cigarettes as a quitting route; SYNTH-20 has no row for cessation drugs. The caffeine clearance line in REF-446 has no source.

Women: most acute tobacco data are in men; half of REF-1459 and REF-1472 are women, and neither tests smoke.

Not in the base at all: pouches, second-hand smoke before a session, cannabis, stress fractures in smokers, the current WADA list. The evidence map holds further candidates (other acute cigarette and hookah studies, half-life reviews, sleep and HRV reviews) that are not entries yet.

Limitations

Transfer. Every smoking, hookah and vaping number is from people not described as trained endurance athletes; every number on trained men is from nicotine non-users or snus users. The base's heart-rate and threshold physiology is itself mostly measured in non-smokers.

Abstract-only and old. REF-1456 (truncated, 1983), REF-1458, REF-1459, REF-1460, REF-1462, REF-1465 (the paper is a page scan, not read), REF-1466 (1988), REF-1467, REF-1468, REF-1469, REF-1471 and REF-1473 are read from abstracts; REF-1457, REF-1461, REF-1463, REF-1464, REF-1470, REF-1472 and REF-1474 in full, REF-1457 and REF-1464 as accepted manuscripts.

Markers, not performance. The heated-tobacco, vape and hookah exposure entries measure COHb, exhaled CO, nicotine or resting values; only REF-1468, REF-1472 and REF-1474 include an exercise test, none at race effort.

Errors in the sources. REF-1463 prints its COHb interval two ways; REF-1458's ">25%" is unexplained and its "18-fold" does not match its means; REF-1469's +13.1% does not match its means by simple arithmetic; REF-1457's study count and its "moderate" or "large" wording differ within the paper.

Interests. All RCTs in REF-1463 were funded by tobacco companies, with its authors declaring no tobacco or e-cigarette funding, though two declare funding from Pfizer and Johnson & Johnson, makers of cessation medication; one author of REF-1464 is a paid consultant in litigation against the tobacco and e-cigarette industry; REF-1461, REF-1462 and REF-1469 have WADA funding; REF-1462's first author is at Eight Sleep Inc.

Practice, not evidence: every hour window, including "about 4 h" and the hookah morning-after rule; the half-life arithmetic in the table; the first cigarette after a key morning session; the race-week rule; "none during a race"; the red-flag list; reading HRV in this light; every reply here.

Half-lives are outside the base. The 4-h and 2-h figures are common pharmacology and resting values, not entries; the only figure inside the base is the 1-2 h for nicotine that REF-1464 quotes from REF-1461's authors, an aside and not a measurement.

Created 2026-10-30: new framework for tobacco and nicotine, the decision the owner approved on 2026-10-30 (what each product costs training and racing, what the hours around a session change, what the assistant says), built from the batch REF-1456 to REF-1474 (owner-approved; numbers as their cards state them, the cards being the corrected reading of the evidence map) with SYNTH-77 as sibling, and PHYS-09, PHYS-12, PHYS-14, PHYS-15, PHYS-28, REF-135, REF-464, REF-446, REF-607 and REF-529.Folds the same day add tobacco and nicotine to the readiness confounder lists of SYNTH-38, SYNTH-41, SYNTH-91 and SYNTH-30, and small acute studies to PHYS-12; REF-446's caffeine line stays, unsourced. 4 time rows by 3 products; level B-.

How this entry was checked and changed

Why this level

(the direction — smoke and CO cost maximal and threshold-type work on the day, a hookah is a large CO dose still measurable at 10 h, heated tobacco and vapes add less CO than a cigarette and do not remove nicotine's own effects, no nicotine product has been shown to buy speed, regular smoking goes with slower races and faster fitness loss — rests on B+ and B entries: REF-1459 (B+, abstract), REF-1456 (B, truncated abstract), REF-1465 and REF-1466 (B+, observational, abstracts), REF-1461, REF-1462 and REF-1464 (B); the A- reviews carry side questions only: craving REF-1457, heated-tobacco biomarkers in industry-funded trials REF-1463, non-union REF-1470. B-, not B, because the default's main question, the hours before a session, has no performance measurement at all; because every hour window, the morning-after rule, the race-week rule and the wording are practice; because no entry measures the half-lives it uses; and because no study measured trained endurance athletes who smoke, and the CO cost has no COHb level attached)