The impact of mitogenic biomarkers on epithelial cells and their role in promoting proliferation in the bronchiolar and alveolar duct epithelium in response to regular physical activity remains indistinct. Hence, this study aims to examine the TGF-α gene expression as a biomarker for the modulation of bronchiolar and alveolar duct epithelium by HIIT exercise training. Twenty-four middle-aged men (age: 45 ± 5 years, VO2max: 34.8ml/kg/min, body fat: 26.25%) were recruited as participants for this study and were randomly assigned to either the control group (n=12) or the exercise group (n=12). Technical abbreviations such as VO2max and HR max were explained when first used. The paper adhered to conventional academic structure and formatting, and used clear and objective language without biased evaluations. All spelling, grammar and punctuation were correct. The exercise group underwent eight weeks of HIIT exercise training, three times a week, for 30 minutes per session on a treadmill, starting at 60% of their maximum heart rate during the first weeks and progressing to 90% on the last weeks. Blood samples, body composition, VO2 max, and expression of the transforming growth factor-α gene were measured 24 hours prior to and following the training program. The TGF-α gene expression was determined via the Bio Easy Master Mix Kit and real-time PCR method. Technical abbreviations are explained on first mention. Data were analyzed via independent t-test on SPSS software. The findings indicate that high-intensity interval training can alter gene expression. TGF-α gene expression was significantly reduced in the exercise group in comparison to the control group (p<0.001). Additionally, bronchiolar and alveolar duct epithelium abnormalities decreased (2-ΔΔCT = -8/2). The current study on middle-aged men supports the preventative role of exercise training on pathological and physiological alveolar duct epithelium abnormalities, achieved through the modulation of TGF-α gene expression.