High Intensity Interval Circuit Training on Resting Metabolic Rate in Overweight Adults
High Intensity Interval Circuit Training on Resting Metabolic Rate in Overweight Adults
This is the first study to examine changes in resting metabolic rate up to 72 hours following
 an exercise session, and how these changes may be affected by 12 weeks of high intensity
 interval circuit training (HIICT). Various training programs that have been implemented in
 previous studies have investigated changes in resting metabolic rate only for the first 2-8
 hours following an exercise session.

 Briefly, the results of this study will provide insight into the following:

 1. To what extent and for how long does HIICT increases the resting metabolic rate
 following an exercise session?

 2. How can this exercise program enhance metabolism without any dietary or other exercise
 intervention?

 3. What is the caloric deficit that will result from 3 months of HIICT and how to what
 extent this deficit will influence body weight reduction?
According to the World Health Organization, overweight and obesity are defined as as abnormal
 or excessive fat accumulation, that presents a risk to health. Body Mass Index (BMI) is a
 useful population-level measure of overweight and obesity in adults, defined as follows: BMI
 = [weight (kg)] / [height (m)^2]. Individuals with BMI>25 kg/m^2 are considered overweight,
 whereas individuals with BMI>30 are considered obese. The higher the BMI, the greater the
 risk of developing non-communicable diseases, such as cardiovascular disease, diabetes
 mellitus and various forms of cancer. Obesity is now the most widespread disease in the
 developed world. It has been estimated that over 1.9 billion adults (39% of the population)
 are overweight, of whom 600 million (13% of the population) are obese. These rates are
 translated into a significant economic impact on a county's health care system; therefore,
 drastic measures are needed. The major cause of obesity is an energy imbalance between
 caloric intake and energy expenditure in favor of the former. Thus, changes in lifestyle that
 affect the energy balance, such as participation in an exercise program, can reduce body
 weight and, therefore, contribute to obesity treatment.

 The recommendation of physical activity for significant weight loss involves prolonged
 exercise of moderate to high intensity that gradually increases to ~250 minutes/week.
 Resistance training is also recommended as it activates the neuromuscular system and can
 improve functional ability. On the other hand, High Intensity Interval Training (HIIT), which
 mainly involves a cardiovascular exercise strategy alternating short periods of intense
 anaerobic exercise with less intense recovery periods, are proposed because they are
 time-efficient. In addition, HIIT improves aerobic capacity and body composition, which is
 related to resting metabolic rate and mitochondrial metabolism of skeletal muscle in both
 healthy and overweight and obese adults. Changes caused by HIIT in mitochondrial function may
 explain the greater efficacy in inducing positive metabolic adaptations compared to
 traditional endurance or resistance protocols, even when not accompanied by dietary weight
 loss strategies.

 Resting metabolic rate is defined as the energy expenditure required to maintain the normal
 physiological processes of the body at rest and accounts for 60-75% of the total daily energy
 expenditure. Small increases in resting metabolic rate could long-term positive effects on
 weight management. Energy expenditure is increased not only during exercise, but also for
 some hours post-exercise. To date, it has been observed that this increase in resting
 metabolic rate can last for up to 48 hours following an exercise session, especially
 following resistance training. More specifically, in a study where 7 women (22-35 years old)
 participated in a resistance training program (100 minutes/session, 10 exercises of 5 sets
 with 10-15 repetitions per set), there was an increase in their resting metabolic rate by 13%
 at the first 3 hours and an increase by 4.2% at 16 hours following an exercise session. On
 the other hand, a 10-week (3 session/week) strength training program with an intensity of
 65-85% of the maximum heart rate based on age (gradual increase in intensity), did not appear
 to cause any changes in resting metabolic rate following an exercise session. However, in
 another study where resistance training (strength protocol of 3 sets with 10-15 repetitions
 per set at the beginning of intervention up to 4-8 repetitions at the end of the
 intervention) was combined with endurance training (65% to 85% with an intensity of 65-85% of
 the maximum heart rate based on age, of increasing intensity), it was observed that resting
 metabolic rate increased following an exercise session.

 It is important to note that, according to the available literature, it has been shown that
 training studies have been examined changes in resting metabolic rate only up to 2-8 hours
 following an exercise session. Therefore, the aim of the present study is to investigate the
 effect of a 12-week HIICT protocol with portable equipment on changes in resting metabolic
 rate 24, 48 and 72 hours following an exercise session.

 Flow of the research design:

 1. Baseline: Anthropometric and physiological measurements (including a Resting Metabolic
 Rate (RMR) measurement following an overnight fast).

 2. One-week familiarization period: Volunteers will participate in two exercise sessions in
 order to learn the right techniques. RMR will be measured 24, 48 and 72 hours following
 the last exercise session. Moreover, participants will be given instructions and then
 they will record their diet for 3 days (2 week days and one weekend day).

 3. Initiation of the 12-week HIICT program: The program will be supervised and portable
 training equipment will be used. There will be 3 exercise sessions per week
 (Monday-Wednesday-Friday). The program will be divided into 3 phases (4 weeks each
 phase), where exercise intensity will increase gradually.

 4. 1st phase: RMR will be measured 24 hours before, as well as 24, 48 and 72 hours
 following the last exercise session of the phase (e.g. at the end of the 4th week of the
 program). Anthropometric and physiological measurements will also be conducted.
 Moreover, participants will record their diet for 3 days (2 week days and one weekend
 day).

 5. 2nd phase: Exercise intensity will increase. The same measurements with phase 1 will be
 conducted.

 6. 3rd phase: Exercise intensity will increase. The same measurements with phases 1 and 2
 will be conducted.
Inclusion Criteria:

 -  Overweight or class I obesity (BMI: 25-35 kg/m^2)

 -  Sedentary lifestyle

 -  Willing to lose weight

 -  Individuals at low risk of various cardiovascular, pulmonary, renal, and metabolic
 diseases as well as other conditions (e.g., pregnancy and orthopedic injury) that
 require special attention when developing the exercise prescription (Thompson et al.,
 2013). This risk classification indicates that participants will be able to
 participate in moderate intensity exercise [40-60% oxygen uptake reserve (VO2R); 3-6
 metabolic equivalent of task (METs)] and also in vigorous intensity exercise (>60%
 VO2R; >6 METs) while medical examination, exercise test and physician supervision are
 not recommended in the preparticipation health screening process.

 Exclusion Criteria:

 -  Following a diet plan or taking dietary supplements over the last 6 months and during
 the intervention

 -  Participation in another training program over the last 6 months and during the
 intervention

 -  Family history of coronary heart disease

 -  Recent musculoskeletal injury