REF-1474 · Simovic et al., 2024 · Journal of Applied Physiology · Paper · PubMed · Free full text

Do regular vapers have lower fitness?

26 young users had lower VO2peak per kg than 16 matched non-users (27.9 vs 32.3 mL/kg/min); absolute VO2peak and peak work: no clear gap. One-time comparison, low-fit adults, no proof of cause.

Main caveat: Cross-sectional: no cause; the authors acknowledge lifestyle factors may contribute and that substance-use data were limited.
limited evidenceMeasured on non-athletes and recreational people

Simovic and colleagues (Virginia Commonwealth University) tested young regular e-cigarette users and non-users on a cycle ergometer after being asked to avoid exercise and tobacco for 12 h.

Users (13 men, 13 women; age 24 ± 3 years; about 4 years of use, every day) and non-users matched by age, sex and BMI (6 men, 10 women) were alike in body composition, resting heart rate, blood pressure, haemoglobin and activity. VO2peak was lower in users per kg body mass (27.9 ± 4.9 vs 32.3 ± 5.5 mL/kg/min), fat-free mass and lean mass (P = 0.005), and % predicted was lower.

Absolute VO2peak (2.0 vs 2.2 L/min) and peak work (165 ± 40 vs 175 ± 26 W) were not significantly different. Estimated oxygen extraction at peak was lower (53 ± 11 vs 61 ± 10%); central haemodynamics were not different.

Age-predicted maximal heart rate reached was 89 vs 92% (P = 0.043) and chronotropic index 0.81 vs 0.87 (P = 0.052); 35% vs 18% met the chronotropic-incompetence cutoff. VO2peak did not track cotinine or years of use. The authors say regular use reduces fitness.

Our reading: a gap of about 4.4 mL/kg/min in low-fit young adults, unexplained by reported activity; selection is possible, and the missing dose link does not help a causal reading.

Protocol

Participants: n = 42; 26 users (at least 3 times a week for at least 3 months; 25 of 26 sole users and never-smokers); 16 never-user, never-smoker controls matched by age, sex and BMI. Excluded: weekly or more use of cigarettes, other tobacco or illicit drugs in the past 60 days; cardiovascular, pulmonary, renal, hepatic, metabolic or cerebral disease; pregnancy.
Preparation: overnight fast of at least 8 h; asked to avoid exercise and tobacco for at least 12 h, with adherence not assured by the authors' own account.
Test: maximal Godfrey protocol on a cycle ergometer with gas exchange; 39 of 42 met maximal criteria, so values are given as peak.
Other measures: bioelectrical impedance, serum nicotine and cotinine, questionnaires on activity, diet and sleep; impedance cardiography in a subset of 33 (22 users, 11 non-users); oxygen extraction estimated from SpO2 and the Fick equation.
Funding and interests (as printed): National Institute on Drug Abuse and FDA Center for Tobacco Products (U54DA036105), American Heart Association predoctoral fellowship and DC Women's Board; no conflicts of interest declared.

Key Results

At peak exerciseUsers (n = 26)Non-users (n = 16)P
VO2 (L/min)2.0 ± 0.52.2 ± 0.50.173
VO2 (mL/kg/min)27.9 ± 4.932.3 ± 5.50.005
VO2 (mL/kg FFM/min)39.0 ± 5.143.7 ± 5.20.005
Peak work (W)165 ± 40175 ± 260.379
Ventilation (L/min)75 ± 2091 ± 210.014
Heart rate (beats/min)175 ± 12182 ± 90.976 (group by time)
Oxygen extraction ratio (%)53 ± 1161 ± 100.005
Cardiac output (L/min)18.5 ± 3.616.8 ± 3.30.090
Chronotropic response: % age-predicted maximal heart rate 89 ± 6 vs 92 ± 5 (P = 0.043); chronotropic response index 0.81 vs 0.87 (P = 0.052), so the abstract's "lower chronotropic responses" rests mainly on the first; incompetence 9 (35%) vs 3 (18%).
Dose: VO2peak was not associated with cotinine or years of use. Users' cotinine 96 ng/mL (median), non-users 0.
Activity: moderate-to-vigorous activity 113 vs 110 min/week (P = 0.917), self-reported.
Numbers that do not add up: the heart-rate P value is 0.976 in Table 3 and 0.967 in the text.

Mechanisms

Measured: lower relative VO2peak and estimated oxygen extraction with unchanged central haemodynamics.
Authors' interpretation: reduced fitness in users is driven mainly by poorer oxygen extraction and utilisation, not by haemodynamic or chronotropic responses, and regular use has adverse effects on cardiovascular health.
Inference: oxygen extraction here is calculated from non-invasive signals in a subset, so the mechanism is a hypothesis. CO is not an obvious explanation: the authors report exhaled CO was similar between groups (no values in the text read), and vapes did not raise exhaled CO in REF-1464. People who start vaping may also differ in unmeasured ways.

Practical Application

Do regular vapers have lower fitness? 26 young users had lower VO2peak per kg than 16 matched non-users (27.9 vs 32.3 mL/kg/min); absolute VO2peak and peak work: no clear gap. One-time comparison, low-fit adults, no proof of cause.
For an athlete who vapes: this is a signal to mention, not a verdict: no trained people, no before-and-after, no link with dose.
A smoker switching to a vape: this does not say whether switching helps or costs; it compared vapers with never-users, not with smokers.
What it does not show: that vaping lowers an athlete's VO2max; a cause; a dose effect; acute effects before a session (REF-1471, REF-1472).

Limitations

Cross-sectional: no cause; the authors acknowledge lifestyle factors may contribute and that substance-use data were limited.
Small, unequal groups; sex ratio differs (13/13 vs 6/10), though not significantly.
Absolute VO2peak and peak work were not significantly different, so the difference appears when scaled to body size.
No dose-response with cotinine or years.
Estimated measures: oxygen extraction and haemodynamics by impedance and pulse oximetry, in a subset.
Self-reported activity; training quality and competition not measured.
Who was measured: young, low-fit adults, not athletes.
Funding and interests: NIDA/FDA and American Heart Association; none declared.
How this entry was checked and changed
Why this level

a small cross-sectional study (rubric B); a real maximal test, but one measurement, small unequal groups, and impedance-based oxygen-extraction estimates in a subset

Full text (checked 2026-10-30)
A total of 26 regular users of e-cigarettes (ECU) and 16 demographically matched, considering age, sex, and body mass index, nonusers (NU) completed this study (full text)
Current users of e-cigarette products for ≥3 times/wk and for ≥3 mo; of 26 regular users, 25 self-identified as sole users of e-cigarettes, never smokers (full text)
V̇o2, L/min 2.0 ± 0.5 vs 2.2 ± 0.5, P 0.173; V̇o2, mL/kg/min 27.9 ± 4.9 vs 32.3 ± 5.5, P 0.005; V̇o2, mL/kg FFM/min 39.0 ± 5.1 vs 43.7 ± 5.2, P 0.005 (full text)
Peak work achieved during the exercise test was not different (ECU: 165 ± 40 vs. NU: 175 ± 26 W; P = 0.379) (full text)
Male users of e-cigarettes and nonusers are classified as "poor" cardiorespiratory fitness, whereas female participants of both groups are classified as "fair" (full text)
Peak oxygen consumption was not associated with e-cigarette nicotine usage (circulating cotinine) or length of use (full text)
ECU: 89 ± 6 vs. NU: 92 ± 5%; P = 0.043; ECU: 0.81 ± 0.9 vs. NU: 0.87 ± 0.7; P = 0.052; 9 (35%) regular users and 3 (18%) nonusers exhibiting chronotropic incompetence (full text)
O2ER, % 53 ± 11 vs 61 ± 10, P 0.005 (full text)
No conflicts of interest, financial or otherwise, are declared by the authors (full text)