## 1 Introduction  
For decades, resistance training (RT) has been one of the most popular modes of exercise used by athletes and exercise populations [1]. According to the American College of Sports Medicine (ACSM), American Heart Association (AHA), and the Surgeon General's Report on Physical Activity and Health, strength training is important for better health and well-being. It improves strength, anaerobic capacity, body composition, bone density, flexibility, and physical function [1]. The recommended volume of resistance exercise as suggested by ACSM should include at least one set of 8-12 repetitions of each one of 8-10 exercises involving the major muscle groups to gain health and fitness benefits [2]. Given the rise in RT participation and the ongoing increase in the number of overweight people [1], a precise measurement of RT's energy expenditure would be beneficial. But there are several problems in measuring energy expenditure during resistance exercises including involvement of large mass (which significantly cause higher energy expenditure) [3], number of sets, rest period, number of repetitions, speed of movement, and load [4]. The greater number of variables makes it difficult to compare results with previous studies. In addition, individual factors like age, gender, body composition, and fitness level are also taken into account as possible intervening variables [4]. However, because RT causes metabolic demands in all three energy systems, indirect calorimetry cannot precisely quantify the energy utilization of moderate-to-high intensity RT [1]. Despite this, [PERSON] et al. [5] were the first to calculate the metabolic cost of RT during exercise and recovery using indirect calorimetry. With underlying limitations, indirect calorimetry is the standard clinical approach to assess the energy expenditure of healthy or diseased individuals over time [6] during physical activity. The Compendium of Physical Activities reported the metabolic equivalent (MET) as the ratio of work metabolic rate to a standard resting metabolic rate of 1.0 (4.184 kJ)/kg/h, 1 MET is considered a resting metabolic rate attained during quiet sitting. The Compendium lists activities as multiples of the resting MET level, ranging from 0.9 (sleeping) to 18 METs (running at 10.9 mph) [7] and resistance training refers to 3.5-5 METs [8]. There are many research studies conducted with variable resistance exercise parameters to derive metabolic equations. A study by [PERSON] et al. 2020 reported a regression equation for the energy cost of a single resistance training session consisting of bench press, pec deck, squat, lat pulldown, biceps curl, triceps extension, hamstring curl, and crunch in healthy males at 75% repetition maximum (RM): Y = \(-473.595+-1.211(X_1)\) + \(17.572(X_2)\) (R\({}^{2}\) = 0.61, \(p<0.05\)). In which \(X_1\) = load-volume (no. of sets x no. of repetitions) and \(X_2\) = session time (minutes) [9]. Another study predicted resting energy expenditure (REE) equations in master athletes using body weight, gender, age, height, fat-free mass (FFM), fat mass (FM), temperature, training hours, phase angle, and kind of sports (R\({}^{2}\) = 0.55-0.69). They concluded that body composition and ambient temperature are the primary variables for determining REE [10]. Up to our knowledge, no research study is found to relate MET with cardiorespiratory variables of moderate resistance exercises at 60% of 1 RM. Because it is important to determine which cardiorespiratory variable has a strong relationship in predicting MET and compare these variables for the untrained and trained participants during moderate resistance exercises. This study aimed to model METs with various cardiorespiratory variables like respiratory exchange ratio (RER), heart rate (HR), blood pressure (systolic and diastolic--SBP and DBP), blood lactate (BL), and Borg rate of perceived exertion (RPE) scale during three dumbbell resistance training exercises (shoulder press, deadlift, and squat).