## 4 Discussion
The results of this study observed that during exercise and rest periods, the untrained group has low QIC and more significant \(p\)-values than the training group models which are more predictive as per the criteria for evaluating these models [18; 20]. The cardiorespiratory variables included in this study were RER, HR, SBP, DBP, BL, and RPE (Table 5). During moderate-intensity interval RT, not all variables have been well-studied in the previous literature for healthy populations. The RER is an indirect measure of the relative utilization of carbohydrates and lipids to overall EE during a steady-state condition. Usually, a high RER reflects carbohydrate oxidation and a low RER indicates lipid oxidation [23]. Therefore, RER during exercise and resting period increased significantly for untrained and trained groups (\(p\) = 0.000*-0.002*) for shoulder press and deadlift exercises. However, our study focused on RT protocol and did not include dietary assessment for participants, so the change in RER cannot be explained well. Interval and RT elicit a greater rise in HR. Fluctuations are seen due to the interruptions in the continuity of the workout modalities [24]. During each repetition, HR responds similarly between eccentric and concentric phases [25]. [PERSON] et al. [26] reported an increase in heart rate during a traditional resistance training exercise and recovery period as 143 \(\pm\) 8.0 and 119 \(\pm\) 12 respectively. In the present study, HR values during exercise and resting period increased in both groups, but this increase was higher for the trained (115.16 \(\pm\) 3.84 and 105.68 \(\pm\) 8.30) than the untrained group (109.52 \(\pm\) 1.13 and 97.94 \(\pm\) 8.40) for all three exercises during six RT sessions. This increase could be explained by the higher workloads of the training group, which imposed more challenges on the cardiovascular system. Based on the possible mechanisms for the change in cardiorespiratory variables during resistance training, blood pressure (BP) increases proportionally to the training load. The main reasons for the change in blood pressure are the use of the Valsalva maneuver, muscle mass activation, muscle action, and the intensity/duration of the set [25]. One study reported mean BPs of 320/250 and 345/245 mmHg during high-intensity leg press and squat in trained bodybuilders [27]. During the Valsalva maneuver, breath-holding increases intrathoracic and intra-abdominal pressure that leads to the increase in blood pressure proportionally [28; 29]. Resting blood pressure may not be affected or reduced by RT. Strength-trained athletes have resting blood pressure that is average or below average [25]. According to a meta-analysis of the RT literature, SBP and DBP may be decreased by 2-4% [30; 31]. In our study, BP was recorded only during resting periods (2-5 min after exercise) as SBP (119.37 \(\pm\) 6.28 and 138.53 \(\pm\) 7.39) and DBP (68.96 \(\pm\) 3.51 and 77.38 \(\pm\) 2.64) for untrained and training groups, respectively, which followed the same trend from previous studies but a slight increase in SBP was noted for the training group. The BL can describe the anaerobic component of the RT. It was measured before the start of exercise and 5 min after each exercise for every training session. It changed for all three dumbbell exercises significantly (\(p\) = 0.000*-0.006*) in both groups.