HIIT consisted of three weekly sessions, each including three blocks of five 30-second all-out punching intervals on a heavy bag, with 6-second rest between efforts and 1-minute rest between blocks.

Participants in both the experimental and control groups followed an identical boxing training program for a period of four weeks, with sessions conducted three times per week. Each session lasted 90 min and was structured in alignment with the established training principles for amateur boxing. The training began with a 15-minute general warm-up phase, including dynamic mobility drills and calisthenics, to elevate core temperature and enhance neuromuscular readiness.

The experimental group completed a 4-week HIIT-boxing protocol, in addition to regular boxing sessions. HIIT consisted of three weekly sessions, each including three blocks of five 30-second all-out punching intervals on a heavy bag, with 6-second rest between efforts and 1-minute rest between blocks. Heart rate was monitored throughout, confirming training intensities of 88-92% HRmax, consistent with high-intensity training standards in combat sports.

Pulmonary function tests were performed using a calibrated desktop spirometer (COSMED Pony FX; COSMED, Rome, Italy) to assess the key respiratory parameters. FVC was recorded to assess lung volume and respiratory strength. Participants performed a maximal inhalation followed by a forceful exhalation to expel as much air as possible.

Unit of Measure: Liters (L)

Aerobic capacity was determined using the Yo-Yo Intermittent Recovery Level 1 (Yo-Yo IR1) test, a validated method for assessing maximal aerobic capacity in intermittent sports. The participants completed repeated 20-meter shuttle runs at increasing speeds, with short recovery periods between efforts. The aerobic capacity was predicted using the established regression equations for the Yo-Yo IR1 test.

MVV was measured using a calibrated desktop spirometer (COSMED Pony FX; COSMED, Rome, Italy) to evaluate overall ventilatory capacity. Participants were instructed to breathe in and out as rapidly and deeply as possible for 12-15 seconds; the value was extrapolated to represent the maximum volume of air inhaled and exhaled in one minute (L/min).

Unit of Measure: Liters per minute (L/min)

FEV1 was measured as the volume of air forcefully exhaled in the first second of the FVC maneuver. This value reflects airway patency and expiratory power.

Unit of Measure: Liters (L)

PEF was assessed to determine the highest speed at which air can be expelled from the lungs during a forceful exhalation following full inspiration.

Unit of Measure: Liters per minute (L/min)