Acute Responses to Walking, Stair Climbing, and Functional Circuit Exercise

• Walking Protocol (Behavioral), also known as WP: Participants performed a 20-minute walking exercise session at a target intensity of 50% heart rate reserve (HRR), maintained within ±5 beats/min of the individual target heart rate. Heart rate was continuously monitored throughout the exercise session.
• Stair Climbing Protocol (Behavioral), also known as SP: Participants performed a 20-minute stair climbing exercise session at a target intensity of 50% heart rate reserve (HRR), maintained within ±5 beats/min of the individual target heart rate. Heart rate was continuously monitored throughout the exercise session.
• Functional Circuit Protocol (Behavioral), also known as FCP: Participants performed a 20-minute functional circuit exercise session at a target intensity of 50% heart rate reserve (HRR), maintained within ±5 beats/min of the individual target heart rate. The circuit consisted of chair sit-to-stand, reverse lunges, wall push-ups, high-knee marching, and low-impact mountain climbers performed on an elevated surface. Heart rate was continuously monitored throughout the exercise session.

Primary outcomes

• Change in Forced Expiratory Volume in One Second (FEV1) [Baseline and 5 minutes after each exercise session]: Forced expiratory volume in one second (FEV1) was measured by spirometry before and 5 minutes after each exercise condition. The primary outcome was the change in FEV1 (ΔFEV1), calculated as post-exercise FEV1 minus pre-exercise FEV1 and expressed in liters (L). Measurements were obtained following standardized spirometry procedures.

Secondary outcomes

• Change in Forced Vital Capacity (FVC) [Baseline and 5 minutes after each exercise session]: Forced vital capacity (FVC) was measured by spirometry before and 5 minutes after each exercise condition. The outcome was the change in FVC (ΔFVC), calculated as post-exercise FVC minus pre-exercise FVC and expressed in liters (L).
• Change in FEV1/FVC Ratio [Baseline and 5 minutes after each exercise session]: The FEV1/FVC ratio was assessed by spirometry before and 5 minutes after each exercise condition. The outcome was the change in FEV1/FVC ratio (ΔFEV1/FVC), calculated as the post-exercise value minus the pre-exercise value.
• Change in Peak Expiratory Flow (PEF) [Baseline and 5 minutes after each exercise session]: Peak expiratory flow (PEF) was measured by spirometry before and 5 minutes after each exercise condition. The outcome was the change in PEF (ΔPEF), calculated as the post-exercise PEF minus the pre-exercise PEF and expressed in liters per second (L/s).
• Change in Blood Lactate Concentration [Baseline and 3 minutes after each exercise session]: Capillary blood lactate concentration was measured before exercise and 3 minutes after each exercise condition. The outcome was the change in blood lactate concentration (ΔLactate), calculated as the post-exercise value minus the pre-exercise value and expressed in millimoles per liter (mmol/L).
• Change in Countermovement Jump Height (CMJ) [Baseline and immediately after post-exercise spirometry initiated at 5 minutes after each exercise session]: Countermovement jump (CMJ) height was assessed before and after each exercise condition. The outcome was the change in CMJ height (ΔCMJ), calculated as the post-exercise value minus the pre-exercise value and expressed in centimeters (cm).
• Mean Heart Rate During Exercise [During each 20-minute exercise session]: Heart rate was continuously monitored throughout each exercise condition. Mean heart rate was calculated across the exercise period and expressed in beats per minute (bpm).
• Maximum Heart Rate During Exercise [During each 20-minute exercise session]: Heart rate was continuously monitored throughout each exercise condition. Maximum heart rate was defined as the highest heart rate recorded during the exercise period and expressed in beats per minute (bpm).
• Time Spent in the Target Heart Rate Range [During each 20-minute exercise session]: Heart rate was continuously monitored throughout each exercise condition. The outcome was the percentage of exercise time during which heart rate remained within ±5 beats/min of the individualized target heart rate corresponding to 50% heart rate reserve (HRR)

Sex: Male, ages: 18 Years to 30 Years, accepts healthy volunteers

Inclusion Criteria:

* Male sex.
* Aged 18-30 years.
* Classified as sedentary/insufficiently active according to the study eligibility criteria.
* Able to safely complete the exercise protocols and study assessments.
* Provided voluntary informed consent.

Exclusion Criteria:

* Current cigarette or electronic cigarette use.
* Known cardiovascular, respiratory, or metabolic disease.
* Regular medication use that could affect physiological responses to exercise.
* Acute infection within the previous 2 weeks.
* Musculoskeletal conditions that could interfere with safe participation in the exercise protocols.
* Any condition requiring medical evaluation before exercise participation.
* Inability to obtain acceptable baseline spirometry measurements according to the study procedures.