REF-1467 · Hashizume et al., 2000 · Medicine & Science in Sports & Exercise · Paper · PubMed

How fast does stopping smoking pay back?

In 11 young male smokers, 6-7 days off lengthened treadmill time and lowered exercise heart rate; VO2max unchanged. No control group, no size given. From the abstract.

Main caveat: Abstract only; no sizes for the main results.
limited, mixed evidenceMeasured on non-athletes and recreational people

Hashizume and colleagues (Toyama University, Japan) tested 11 male volunteers, mean age 20.5 years, smoking 20.5 cigarettes a day for about 3.5 years. On days 1-2 they measured lung function, predicted maximal oxygen debt, resting heart rate, blood pressure, venous blood and VO2max on a treadmill; the men then abstained, and the same measurements were repeated on days 8-9.

Plasma cotinine had almost disappeared. Exercise time was significantly longer (P < 0.001) and heart rate fell at almost all treadmill stages, while maximal heart rate, VO2max, maximal ventilation and lung function did not change.

PO2, oxygen saturation, HCO3 and CO2 concentration rose, and pulse pressure rose (P < 0.05); resting heart rate, systolic and diastolic pressure did not change. The authors conclude exercise performance improved. Our reading: it points to a fast payback, in the form of lower heart rate at the same stage and longer time, with no change in VO2max.

With no control group, some of the gain could be learning the test; the abstract gives no minutes or bpm.

Protocol

Participants: n = 11 men, mean age 20.5 years, about 3.5 years of smoking, 20.5 cigarettes a day.
Measures before and after: day 1 and day 8: physical characteristics, pulmonary function, predicted maximal oxygen debt on a bicycle ergometer; day 2 and day 9: resting heart rate, blood pressure, venous blood, VO2max on a treadmill.
Abstinence: from the day-2 measurements; verified by plasma cotinine.
Control group: none.
Funding and interests: none listed in the PubMed record; no statement in the abstract.

Key Results

Outcome after 6-7 days without smokingResult
Plasma cotininealmost disappeared
Treadmill exercise timesignificantly longer (P < 0.001); size not in the abstract
Heart rate during treadmill exercisesignificantly lower at almost all stages; size not in the abstract
Maximal heart rateunchanged
VO2max, maximal ventilationunchanged
Lung functionno significant improvement
Resting heart rate, systolic and diastolic pressureno significant change
Pulse pressuresignificantly higher (P < 0.05)
PO2, O2 saturation, HCO3, CO2 concentrationsignificantly higher
Predicted maximal oxygen debtno significant change

Mechanisms

Measured: longer exercise time and lower submaximal heart rate with unchanged VO2max, along with better venous oxygen values.
Authors' interpretation: exercise performance improved with 7 days of abstinence.
Inference: less CO and nicotine would be expected to lower heart rate at the same work (PHYS-12). The abstract does not report COHb, so CO clearance is assumed here rather than measured, and test familiarity may add to the longer time.

Practical Application

How fast does stopping smoking pay back? In 11 young male smokers, 6-7 days off lengthened treadmill time and lowered exercise heart rate; VO2max unchanged. No control group, no size given. From the abstract.
What to expect first: heart rate at the same effort before any VO2max change, as this design suggests; do not promise a number.
Reading the numbers after stopping: heart rate at a fixed power may drop in the first week for this reason alone, so it is not a clean sign of new fitness (PHYS-12; inference).
Timing a quit: not from this paper; the base's own practice: plan it away from an A race, since this paper did not measure withdrawal.
What it does not show: a controlled effect; any result in trained athletes, women or heavy long-term smokers; effects beyond a week.

Limitations

Abstract only; no sizes for the main results.
Uncontrolled, same test repeated within about 9 days; learning and motivation can lengthen test time.
Small (n = 11), men only, young, short smoking history.
Who was measured: volunteers, not athletes.
Unblinded and no COHb in the abstract.
Funding and interests: none in the record.
How this entry was checked and changed
Why this level

(from the abstract) — an uncontrolled pre-post study (rubric B) with a further serious limitation: a small abstract-only study with key data missing, no size for exercise time and no control for repeating the same test