This study aimed to develop and evaluate a customized physical fitness assessment, known as the Physical Instrument for Asthmatics (PIA), for PATHFIT students diagnosed with asthma. Specifically, it determined pre-test and post-test performance and examined whether the intervention improved overall physical fitness. A pre-experimental one-group pre-test–post-test design was employed, involving PATHFIT 2 and PATHFIT 4 students during the second semester of the 2025–2026 academic year. Participants were selected based on a confirmed asthma diagnosis and medical clearance. The study used a modified physical fitness test comprising the six-minute walk test, wall sits, seated leg raises, 30-second walk test, vertical jump, and T-agility test. Results revealed that participants demonstrated improved performance across all fitness components following the intervention. Cardiovascular endurance increased, as evidenced by greater distances covered, while muscular strength and endurance reached higher performance classifications. Improvements were also observed in speed, power, and agility, although slight variability remained among participants. The findings suggest that structured, asthma-sensitive physical activity can enhance physical fitness without compromising safety. The study concludes that the PIA model is an effective and appropriate tool for assessing and improving students' physical fitness with asthma. It is recommended for use in inclusive physical education programs. It may serve as a basis for future research and program development.