Pulmonary function testing (PFT) is a central part of diagnosis and treatment monitoring in respiratory medicine. Few studies have investigated whether repeated PFT or training can significantly influence performance.To investigate potential training effects of repeated PFT, 30 healthy volunteers underwent daily and weekly repeated PFT with spirometry over 10 weeks. The study included 22 females and 8 males with a mean age of 31.8 years ± 15 (SD), a mean weight of 66.3 kg ± 14.5 (SD) and a mean BMI of 22.4 ± 3.3 (SD). The first 5 PFTs were performed on 5 consecutive days, followed by 3 PFTs once a week on the same day of the week. Subsequently, 5 measurements were taken daily for 5 consecutive days. After these 13 appointments in 5 weeks, participants were randomly assigned to the control or incentive group, with stratification for age and gender. The incentive group had the opportunity to win money (200 €) for the highest increase in forced vital capacity (FVC). PFTs were performed once a week on the same day of the week as before for 5 more times. Motivation was assessed by a questionnaire before the 1st, 9th and 18th measure of PFT at three time points throughout the study.An increase in PFT was observed with mean increases of 473 [ml] in FVC, 395 [ml] in forced expiratory volume in 1 s (FEV1) and 1.382 [litres/second] in peak expiratory flow (PEF) after four days of daily PFT. These increases did not persist and spirometric data returned to baseline after one week. After allocation, participants in the incentive group did not increase their FVC, FEV1 or PEF compared to the control group. The incentive group showed higher motivation than the control group, even before allocation.Repeated daily PFT could induce short-term increases, but PFT does not fluctuate significantly in the long term. External influences that affect motivation could not consistently increase PFT. For clinical practice, it can be concluded that PFT does not necessarily require extended training to ensure reliability if reproducibility criteria are met.