Background: - Physical activity is a major risk factor of the disease which leads cardio respiratory problem, obesity etc. maximal (or peak) oxygen consumption (VO2max) is acknowledge as the best physiological measure of cardio respiratory fitness. Aerobic exercise is associated with improvement in maximal oxygen consumption (VO2max) and cardiovascular fitness. Objective: To determine the Efficacy of Jacobson’s Relaxation Technique in improving the aerobic fitness ((VO2max) in young adults. Participants: Total sixty subjects have been included in the study (aged 18-40 years). The subjects were randomly selected through chit method and divided into two group i.e 30 in Jacobson’s Relaxation Technique Group (A) and 30 in Aerobic Exercise (brisk walking Group (B) respectively. the pre and post intervention SPO2, Blood Pressure, Heart Rate and VO2max were noted and compared in two exercise conditions for duration of 4 weeks. The VO2max was measured for baseline and after 4 weeks intervention with the help of Rockport walking test. Result: The statistical analysis revealed significant difference in post 4 week intervention reading of maximal oxygen uptake (VO2max) (t value = 1.928, p= 0.59), but the not significant difference of SPO2 (t value = 0.929, p= 0.358), Diastolic Blood Pressure (t value = 1.307, p= 0.197) Systolic Blood Pressure (t value = 0.412, p= 0.082), Heart Rate (t value = 0.658, p= 0.513) respectively. Similarly, there were significant difference with in Jacobson relaxation exercise Group for pre and post 4 week intervention value of maximal oxygen uptake (VO2max) (t value = 6.146, p= 0.00), SPO2 (t value = 3.633, p= 0.001), Diastolic Blood Pressure (t value = 1.120, p= 0.197) Systolic Blood Pressure (t value = 2.615, p= 0.14), Heart Rate (t value = 19.630, p= 0.00) respectively. Conclusion- This study concluded that the Exercise interventions in form of Jacobson’s Relaxation Technique and Aerobic Exercise can bring improvement in maximal oxygen uptake (vo2max) in normal young adults. It is hypothetically proved that the Jacobson’s relaxation technique is more effective as compared to the aerobic exercise.