Abstract
nsistent practice of physical activity has well known positive e ects on general health; however, time for exercise remains one major barrier for many. An acute bout of high intensity interval resistance training (HIIRT) increases acute resting energy expenditure (REE) and decreases respiratory ratio (RR), suggesting its potential role on weight loss and increased fatty acid oxidation. The aim of this study was to test the long-term e ect of HIIRT on body composition, lipid pro le and muscle strength using a randomized parallel trial. Twenty healthy young adults (22.15 1.95 years) were randomized to perform either a HIIRT (N=11) protocol, consisting of three sets of 6 repetitions at 6 repetition maximum (RM) and then 20 seconds of rest between repetitions until exhaustion repeated for 3 times with 2 0 30 rest between sets or a traditional training (TRT, N=9) protocol of 3 sets of 15 reps with 75 sec of rest between sets. Body composition, resting energy metabolism, aerobic capacity, muscle strength and blood measurements were taken before and after 8 weeks of training. Both protocols enhanced muscle strength, but only HIIRT improved endurance strength performance (+22.07%,p<0.05) and lean body mass (+2.82%,p<0.05). REE and RR were unaltered as lipid pro le. HIIRT represents
of 15 reps with 75 sec of rest between sets. Body composition, resting energy metabolism, aerobic capacity, muscle strength and blood measurements were taken before and after 8 weeks of training. Both protocols enhanced muscle strength, but only HIIRT improved endurance strength performance (+22.07%,p<0.05) and lean body mass (+2.82%,p<0.05). REE and RR were unaltered as lipid pro le. HIIRT represents a valid training method to improve muscle strength and mass, but its role on body weight control was not con rmed. Keywords:resistance training; high intensity; recovery time; physical tness; strength 1. Introduction Resistance training (RT) is an important component of exercise protocols, mostly used to enhance muscle strength and hypertrophy. Additionally, RT can in uence resting energy expenditure (REE) and fat metabolism, assisting in weight loss process [1]. Lack of time is one of the major barriers to a constant practice of physical activity, therefore the concept of high intensity interval training (HIIT) is becoming very popular. This kind of training is principally used with aerobic exercise and allows to achieve maximal results in a relatively short time of e ort. In the past ten years, HIIT has been largely investigated and di erent protocols have been de ned, but all of them are characterized by brief repeated bouts of vigorous exercise alternated Int. J. Environ. Res. Public Health2020,17, 4093; doi:10.3390 /ijerph17114093 /journal/ijerph
Int. J. Environ. Res. Public Health2020,17, 4093 2 of 15 with periods of lower intensity exercise or recovery [24]. Because RT is composed by numerous variables (i.e., sets, repetition, load, type of contraction) [5], it is di cult to replicate this same pattern of short-term high intensity training. We have previously identi ed a variant of the rest-pause [6] or so-called cluster training technique [7], named high-intensity interval resistance training (HIIRT) [8], as a good candidate to mimic HIIT and reduce the total training time [9,10]. This technique requires to lift heavy loads with a partial recovery within a single set, promoting, on one hand, total depletion of intramuscular creatine phosphate [11] and complete exhaustion [12] after each set with a partial recovery [6], and on the other, a shorter total time to nish the exercise. We have already demonstrated that an acute bout of HIIRT increases excess post-exercise oxygen consumption (EPOC) and REE and shifts the respiratory quotient (RR) towards fatty acids utilization [13]. These ndings suggested that HIIRT has a potential in uence on weight loss and body composition. Some research speculates that hormonal mechanisms related to muscle hypertrophy and muscle damage are involved in EPOC increase, through alteration of cell homeostasis [13,14]. EPOC represents the increased consumption of oxygen (VO2) used to repay the oxygen debt contracted in the initial phase of e ort [15]. From a physiological point of view, muscle tissue is one of the main limiting factors for VO2due to the important role of its oxidative enzymes, mitochondria and capillary perfusion on aerobic capacity. However, the role of high intensity RT on aerobic capacity is still controversial, with some authors showing no changes in aerobic capacity [16,17] and others con rming its role on empowering energy metabolism [1719]. It is well established that physical activity improves lipid pro le and reduces cardiovascular risk [20]; in particular, RT plays an important role on reducing total cholesterol, LDL-cholesterol, TG and increased HDL-c [21]; however, the e ects of high intensity RT have not been completely explicated. Recently, we demonstrated that HIIRT improves lipid pro le in
empowering energy metabolism [1719]. It is well established that physical activity improves lipid pro le and reduces cardiovascular risk [20]; in particular, RT plays an important role on reducing total cholesterol, LDL-cholesterol, TG and increased HDL-c [21]; however, the e ects of high intensity RT have not been completely explicated. Recently, we demonstrated that HIIRT improves lipid pro le in healthy and obese older adults [10,22]; however, no data are available on younger adults. Thus, the purpose of this research was to evaluate the long-term e ects of HIIRT compared to a traditional resistance training (TRT) program on resting metabolism, body composition and some blood values in sedentary young people; we also wanted to verify the e ects on aerobic capacity and di erent expressions of strength. Compared to TRT, HIIRT is expected to o er a good training stimulus but with a shorter exercise time commitment. Based on our previous ndings [9,10], our hypothesis was that HIIRT would have a greater e ect on implement muscle strength and reduce fat mass compared to a traditional training protocol (TRT). In addition, because of the acute in uence of HIIRT on EPOC, we expected a reduction of respiratory quotient and an increase in aerobic capacity. 2. Materials and Methods 2.1. Subjects Twenty-one young healthy subjects (22.15 1.95 years, BMI 23.57 1.63 kg/m 2 ) were recruited from the University of Padova student community via advertisements in social media and websites. However, one participant was for nal analysis (CONSORT diagram is presented in Appendix). excluded during the nal analysis due to poor compliance with exercise protocol. Thus, twenty subjects were considered. All subjects were recreationally active and had previous experience with resistance training, but none of them practiced regularly strength training (<2 sessions/week). Eligibility was determined using clinical history and physical exam. Exclusion criteria for the study included history of chronic diseases (diabetes, cardiorespiratory or metabolic disorders) or any other condition that might have interfered with one's ability to adhere to exercise protocols. Baseline subjects' characteristics are reported in Table.
sessions/week). Eligibility was determined using clinical history and physical exam. Exclusion criteria for the study included history of chronic diseases (diabetes, cardiorespiratory or metabolic disorders) or any other condition that might have interfered with one's ability to adhere to exercise protocols. Baseline subjects' characteristics are reported in Table.
Int. J. Environ. Res. Public Health2020,17, 4093 3 of 15 Table 1.Subjects characteristics at baseline. HIIRT (N=11) TRT ( N=9) Age (years) 22.27 1.85 22.00 2.18 Height (cm) 171.36 10.34 170.78 9.76 Weight (kg) 68.76 12.06 68.60 8.39 BMI (kg/m 2 ) 23.67 2.07 23.45 0.97 Fat mass (%) 23.94 5.64 24.74 6.69 Data are mean SD. HIIRT, High Intensity Interval Training; TRT, Traditional Resistance Training; BMI, Body Mass Index. 2.2. Study Design The study was designed as a randomized parallel trial. After signing a written informed consent form, eligible subjects were randomly assigned to either a high intensity interval resistance training (HIIRT, N=11) or a traditional resistance training (TRT, N=9) protocol. The randomization list was generated using GraphPad QuickCalcs Web site (http: //www.graphpad.com/quickcalcs). Subjects came to our lab three times for screening tests and to familiarize themselves with the training protocol. The general design is depicted in Figure. The rst visit was used to obtain the subject's BMI, resting metabolism through REE and RR measurement and aerobic power (VO2max) via an incremental maximal test at the cycle-ergometer. Three days later, we obtained blood samples and body composition analysis, whilst muscle strength was assessed with a handgrip and a 5-repetition maximum (RM) test for lower and upper limb. During the third visit, 5RM test was performed to assess chest and back strength, and a squat jump test was used to test muscle power performance.Int. J. Environ. Res. Public Health 2020, 17, x FOR PEER REVIEW 3 of 16 Table 1. Subjects characteristics at baseline. HIIRT ( N = 11) TRT (N = 9) Age (years) 22.27 ± 1.85 22.00 ± 2.18 Height (cm) 171.36 ± 10.34 170.78 ± 9.76 Weight (kg) 68.76 ± 12.06 68.60 ± 8.39 BMI (kg/m 2 ) 23.67 ± 2.07 23.45 ± 0.97 Fat mass (%) 23.94 ± 5.64 24.74 ± 6.69 Data are mean ± SD. HIIRT, High Intensity Interval Training; TRT, Traditional Resistance Training; BMI, Body Mass Index. 2.2. Study Design The study was designed as a randomized parallel trial. After signing a written informed consent form, eligible subjects were randomly assigned to either
) 23.67 ± 2.07 23.45 ± 0.97 Fat mass (%) 23.94 ± 5.64 24.74 ± 6.69 Data are mean ± SD. HIIRT, High Intensity Interval Training; TRT, Traditional Resistance Training; BMI, Body Mass Index. 2.2. Study Design The study was designed as a randomized parallel trial. After signing a written informed consent form, eligible subjects were randomly assigned to either a high intensity interval resistance training (HIIRT, N = 11) or a traditional resistance training (TRT, N = 9) protocol. The randomization list was generated using GraphPad QuickCalcs Web site (http://www.graphpad.com/quickcalcs). Subjects came to our lab three times for screening tests and to familiarize themselves with the training protocol. The general design is depicted in Figure 1. The first visit was used to obtain the subject’s BMI, resting metabolism through REE and RR measurement and aerobic power (VO 2max) via an incremental maximal test at the cycle-ergometer. Three days later, we obtained blood samples and body composition analysis, whilst muscle strength was assessed with a handgrip and a 5-repetition maximum (RM) test for lower and upper limb. During the third visit, 5RM test was performed to assess chest and back strength, and a squat jump test was used to test muscle power performance. After the completion of all tests, subjects started their training protocol. All subjects underwent the same TRT training schedule for the first two weeks, and from weeks 3 to 8, they performed the assigned interventional protocol (HIIRT or TRT) three times per week. After the conclusion of the above, subjects were asked to return to the laboratory, where they repeated all tests in the same order as at the pre-training stage. Subjects were also asked to fill a food diary the week before starting and ending the study. The study was approved by the Human Ethical Commission of the Department of Biomedical Sciences (HEC-DSB 01/2015), in accordance with Helsinki’s declaration of 1995 as modified in 2000. All participants started the experimental procedures in February 2013, and study was concluded in May 2013. Figure 1.Study design. HIIRT, High Intensity Interval Training; TRT, Traditional Resistance Training; DEXA, Dual-Energy X-Ray
study. The study was approved by the Human Ethical Commission of the Department of Biomedical Sciences (HEC-DSB 01/2015), in accordance with Helsinki’s declaration of 1995 as modified in 2000. All participants started the experimental procedures in February 2013, and study was concluded in May 2013. Figure 1.Study design. HIIRT, High Intensity Interval Training; TRT, Traditional Resistance Training; DEXA, Dual-Energy X-Ray Absorptiometry; pQCT, Peripheral Quantitative Computed Tomography; RM, Repetition Maximum. After the completion of all tests, subjects started their training protocol. All subjects underwent the same TRT training schedule for the rst two weeks, and from weeks 3 to 8, they performed the assigned interventional protocol (HIIRT or TRT) three times per week. After the conclusion of the above, subjects were asked to return to the laboratory, where they repeated all tests in the same order as at the pre-training stage. Subjects were also asked to ll a food diary the week before starting and ending the study.
Int. J. Environ. Res. Public Health2020,17, 4093 4 of 15 The study was approved by the Human Ethical Commission of the Department of Biomedical Sciences (HEC-DSB 01/2015), in accordance with Helsinki's declaration of 1995 as modi ed in 2000. All participants started the experimental procedures in February 2013, and study was concluded in May 2013. 2.3. Body Composition Assessment Body mass index (BMI) was calculated in kg/m 2 : Body weight was measured using an electronic scale to the nearest 0.01 kg (Tanita BWB-800 Medical Scales, USA) and height using a portable stadiometer with a precision of 0.01 m (Holtain Ltd., UK). Total and regional lean mass and adipose tissue were analyzed by dual-energy x-ray absorptiometry (DEXA) (QDR 4500 W, Hologic Italia s.r.l, Rome, Italy) after an overnight fast. Muscle mass percentage and its ratio with lean body mass were also calculated using a skin-fold method. The formula to estimate body composition considered nine skin folds sites (triceps, biceps, chest, subscapular, iliac, abdominal, anterior and popliteal thigh), 6 bone circumferences (arm, forearm, waist, hips, thigh and calf) and 4 bone diameters (elbow, wrist, knee and ankle). Skinfolds were measured to the nearest 1 mm using a Holtain caliper (Holtain Ltd., UK). All measurements were taken by the same operator (AP) before and after the study, according to standard operating procedures [23]. Data obtained were then processed on a validated software (Fitnext ® , Caldogno, Vicenza, Italy) [24]. Distal thigh and forearm muscle section were also analyzed using a Norland/Stratec XCT-3000 Peripheral Quantitative Computed Tomography (pQCT) scanner (Stratec Medizintechnik GmbH, Pforzheim, Germany), which is a non-invasive technique normally employed to measure bone density but also useful for highlighting the transverse section of muscle belly (CSA) in mm 2 . Subjects were placed on a special stool and asked to remain as still as possible while the scanner moved around the limbs throughout their length. The obtained images were then processed using analysis software (XCT 3000-Stratec Medizintechnik GmbH, Tumeltsham, Austria) to quantify muscle and adipose tissue content. As per standard procedures, all measurements were taken and measured by the same operators (FB
placed on a special stool and asked to remain as still as possible while the scanner moved around the limbs throughout their length. The obtained images were then processed using analysis software (XCT 3000-Stratec Medizintechnik GmbH, Tumeltsham, Austria) to quantify muscle and adipose tissue content. As per standard procedures, all measurements were taken and measured by the same operators (FB and LB). 2.4. Muscle Strength and Aerobic Performance Strength tests were divided into four groups: Dynamic (1RM), two isometric handgrip strength tests (peak and endurance) and explosive strength (squat jump test). During the 6RM test, subjects were asked to reach the load with which they were able to perform a maximum of 6 repetitions. This method is particularly safe when the participant has no experience with training [25]. Maximal repetition was estimated using Brzycki's formula [26]. All muscle groups employed during training session were tested in alternate days. Isometric force was measured with the Dynatronic 100 ergometer handgrip (New Mechanics Pastorelli, Gallarate, VA, Italy), and the average of 3 performances was considered. To evaluate endurance strength, subjects were asked to maintain pressure on the dynamometer at 50% of their ceiling for the longest possible time. Time was recorded and considered as indicative of muscle endurance capacity. Finally, a squat jump test was performed according to Bosco description [27] and the best out of three performances was chosen for analysis. Subjects were asked to keep hands on their hips, and the trunk was maintained erect. Subjects started from the seated position, with 90 of knee exion, on a contact mat (ErgojumpBosco system, srl, S. Ru na di Cittaducale, Rieti, Italia). The height of jumps was calculated according to the Asmussen and BondePetersen formula [28]. Aerobic power was measured with an incremental maximal test on a ciclo-ergometer. Peak power output (PPO), VO2(L/min), VO2max (mL/kg/min), VCO2(L/min), carbon dioxide end-tidal partial pressure (PETCO2), pulmonary ventilation (VE) and RR were measured. Respiratory gases were measured via standard open-circuit calorimetry (max Encore 29 System, Vmax, Viasys Healthcare, Inc., Yorba Linda, CA, USA) on a breath-by-breath modality. The protocol included 3 min of warm up at
maximal test on a ciclo-ergometer. Peak power output (PPO), VO2(L/min), VO2max (mL/kg/min), VCO2(L/min), carbon dioxide end-tidal partial pressure (PETCO2), pulmonary ventilation (VE) and RR were measured. Respiratory gases were measured via standard open-circuit calorimetry (max Encore 29 System, Vmax, Viasys Healthcare, Inc., Yorba Linda, CA, USA) on a breath-by-breath modality. The protocol included 3 min of warm up at
Int. J. Environ. Res. Public Health2020,17, 4093 5 of 15 60 W, then 1 min at 100 W and intensity increased by 15 W every 60 s until exhaustion. Subjects were asked to keep a pedaling cycle of 60 rpm for the duration of the test; the test was interrupted by the subject due to exhaustion, or when the pedaling cycle was not maintained. 2.5. Resting Metabolism Resting energy expenditure (REE) and Oxygen uptake (VO2) were measured using the above-mentioned calorimetry system. Participants arrived after an overnight fast and rested in a comfortable supine position before beginning the test. Then, a silicone mask covered both mouth and nose was applied, and subjects were asked to stay relaxed but awake during the test. Oxygen and carbon dioxide concentrations were obtained for a total of 20 min. Only the last 10 min were used to measure the results and to calculate resting energy expenditure (REE) and respiratory ratio (RR) using the modi ed Weir equation [29]. 2.6. Blood Biochemistry Blood samples were obtained approximately at 8 A.M. at rest, and after an overnight fast, subjects were instructed to avoid any strenuous activity during the 24 h prior to the test. Total cholesterol (CHOLt), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), glucose, uric acid, creatinine and gamma-glutamyl transferase (GGT) were measured by an enzymatic colorimetric method using a Modular D2400 (Roche Diagnostics, Basel, Switzerland). Insulin was measured with a chemiluminescent immunoassay (Siemens Immulite 2000); alanine aminotransferase (ALT) and aspartate transaminase (AST) were measured by pyridoxal phosphate activation according to manufactured instruction, whilst a kinetic enzymatic method was used to detect creatine kinase (CK) and Urea. Total testosterone was determined by the immunochemiluminescent method (Roche Cobas e601, Roche Diagnostics, Mannheim, Germany), whilst free testosterone was measured with a radioimmunological manual method (Beckman Coulter). Insulin-like growth factor-1 (IGF-I) was measured using the analyzer Liaison XL (DiaSorin S.p.A, Vercelli- Italy), whilst its isoform IGFBP1 with a sandwich immunoassay based on a chemiluminescent revelation (Dia Source). 2.7. Training Protocol All subjects trained three times per week with at least one-day rest between sessions. All participants began
Description
This research compares HIIRT and traditional resistance training effects on body composition and strength.