AST Correlation

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Introduction

Metabolism is the set of all biochemical reactions which are happening in the cells of an organism that are involved in catabolism and anabolism of organic substrates. The term metabolism refers to the amount of heat generated during these processes. The mini- mal amount of energy required to sustain basic vital functions is known as the basal metabolic rate (BMR) and it accounts for 50–70% of total daily energy ex- penditure (TDEE) [1]. The largest component of

daily energy expenditure is indispensable for proc- esses such as circulation, breathing, nervous system functioning etc. The second largest component of TDEE is physical activity related energy expenditure that accounts for 15 to 30% depending on the type and intensity of physical activity (Graph 1). The last component of TDEE is the thermic effect of food (TEF), accounting for approximately 10% and it rep- resents the additional energy used for digestion and absorption of nutrients, as well as storage and syn- thesis of organic compounds [2].

Summary Introduction. The difference between 24-hour daily energy intake and total daily energy expenditure determines whether we lose or gain weight. The resting metabolic rate is the major component of daily energy expenditure, which depends on many different factors, but also on the level of physical activity. The aim of the study was to determine anthropometric and metabolic parameters of athletes engaged in different types of training, to compare obtained results and to examine whether there are statistically significant differences among them. Ma- terial and Methods. The study included a total of 42 young male athletes divided into two groups. The first group included 21 athletes who were predominantly engaged in aerobic type of training, and the other group of 21 athletes in anaerobic type of training. Anthropometric measurements were taken and resting metabolic rate was assessed using the indirect calorimetry method. The results were statistically analyzed and the differ- ences in parameters between the two groups were compared. Results. Statistically significant differences were established in total body mass, amount of fat-free mass and muscle mass, body mass index, as well as in the relative metabolic indices between two groups of subjects. Conclusion. The percentage of fat-free body mass has the greatest impact on the resting metabolic rate. The rate of metabolic activity of this body com- partment is higher in athletes engaged in aerobic than in athletes engaged in anaerobic type of training. Key words: Weight Loss; Exercise; Athletes; Anthropometry; Calorimetry, Indirect; Energy Metabolism; Basal Metabolism; Oxygen Consumption; Resistance Training; Anaerobic Threshold

Sažetak Uvod. Razlika između 24-časovnog dnevnog energetskog unosa i ukupne dnevne energetske potrošnje određuje da li će doći do porasta u telesnoj težini ili njenog smanjenja. Najveći udeo u dnev- noj potrošnji čini energetska potrošnja mirovanja koja zavisi od mnogo različitih faktora ali takođe i od nivoa fizičke aktivnosti. Cilj ovog rada bio je da se odrede vrednosti antropometrijskih i metaboličkih parametara sportista na različitom tipu treninga, uporede dobijeni rezultati i ispita da li postoje statistički značajne razlike između njih. Materijal i metode. Ispitivanje je obuhvati- lo ukupno 42 mladih sportista muškog pola podeljenih u dve grupe. Prvu grupu je činio 21 sportista pretežno na aerobnom tipu treninga, a drugu grupu je činio 21 sportista na anaerobnom tipu treninga. Svim ispitanicima su mereni antropometrijski parame- tri i energetska potrošnja mirovanja kao metabolički parametar metodom indirektne kalorimetrije. Dobijeni rezultati su statistič- ki obrađeni i upoređene su razlike u parametrima između dve grupe sportista. Rezultati. Prilikom obrade antropometrijskih i metaboličkih parametara utvrđeno je da postoje statistički zna- čajne razlike u telesnoj masi, količini bezmasne i mišićne mase, indeksu telesne mase kao i u relativnim metaboličkim pokazate- ljima dve grupe ispitanika. Zaključak. Najveći uticaj na energet- sku potrošnju mirovanja ima procenat telesne mase koji ne sadr- ži masti, tj. bezmasna masa tela. Stopa metaboličke aktivnosti ovog telesnog kompartmana je veća kod sportista na aerobnom u odnosu na sportiste na anaerobnom tipu treninga. Ključne reči: gubitak težine; vežbanje; sportisti; antropometrija; indirektna kalorimetrija; energetski metabolizam; bazalni metabo- lizam; potrošnja kiseonika; trening snage; anaerobni prag

University of Novi Sad, Faculty of Medicine Novi Sad1 Original study University of Novi Sad, Faculty of Medicine, Originalni naučni rad Department of Physiology, Novi Sad2 UDK 796.015 i Institute of Child and Youth Health Care of Vojvodina, Novi Sad3 UDK 613.72/.73:613.25 i 572.5 https://doi.org/10.2298/MPNS1910272S

EFFECTS OF DIFFERENT TYPES OF TRAINING ON WEIGHT LOSS

UTICAJ RAZLIČITIH TIPOVA TRENINGA NA GUBITAK TELESNE TEŽINE

Danijel SLAVIĆ1, 2, Dea KARABA JAKOVLJEVIĆ1, 2, Andrea ZUBNAR3, Borislav TAPAVIČKI1, Tijana ALEKSANDRIĆ1 and Miodrag DRAPŠIN1, 2

Corresponding Author: Asist. dr Danijel Slavić, Univerzitet u Novom Sadu, Medicinski fakultet, Katedra za fiziologiju, 21000 Novi Sad, Hajduk Veljkova 3, E-mail: [email protected]

Slavić D, et al. Different Types of Training and Weight Loss

Med Pregl 2019; LXXII (9-10): 272-279. Novi Sad: septembar-oktobar. 273

In scientific literature, the term resting metabolic rate (RMR) is often incorrectly used instead of basal metabolic rate (BMR), whose values are approximate to those of basal metabolism, but the method used to acquire it is less demanding and easier to perform [2]. Since the values of RMR are ~10% higher than of BMR [3], this component is certainly the largest contributor to TDEE.

Many studies have shown that the most important factor affecting the BMR (i.e. RMR) is the part of the body mass that does not include fat, that is, the fat-free mass (FFM) [4]. Considering that FFM is mainly composed of muscle mass and that it accounts a lot in the total body weight, it can be concluded that the muscles significantly account for resting energy expenditure [5, 6]. So, regardless of variations in the amount of adipose tissue in an individual, if there are no changes in FFM compartment, the RMR remains approximately the same as before and amounts to 60 - 75% of its daily calories expended (Graph 1). The RMR value is also affected by the age and gender of the individual, hormone levels, circadian rhythm, body temperature, physical activity, genetics and malnutrition. In the course of aging, RMR progres- sively diminishes, mainly due to the reduction in the amount of skeletal muscle mass and mass of internal organs, gradual decrease of metabolic activity of in- dividual organs as well as due to an increase in the proportion of fat mass which generally has a lower

metabolic rate [7]. Gender differences in RMR val- ues are also caused by a smaller amount of muscle mass and a higher amount of fat mass in women. Hormonal imbalance can also greatly affect RMR, increasing it by as much as 50 – 100% in case of thy- roid hormones and 15 – 20% in case of elevated growth hormone levels, while increased testosterone levels may increase RMR values by 10 – 15% [1]. A rise in body temperature increases RMR, while sleep lowers it, due to the reduction of skeletal muscle tone and the effects of the vegetative nervous system [8]. Also, it is established that situations with reduced energy intake lead to a decrease in RMR [9, 10].

Physical activity changes the body composition, i.e. it changes the proportion of fat and fat-free mass in overall body weight and thus brings the athlete a more favorable ratio of these two components, compared to non-athletic individuals. Body composition is impor- tant to the majority of athletes, particularly because the ratio of fat to fat-free mass affects their sports perform- ance [11, 12]. Body composition can be determined indirectly (by measuring skinfold thicknesses, bioelec- trical impedance analysis method, etc.) or directly, i.e. by directly measuring the fatty and non-fatty tissue using imaging methods (magnetic resonance imaging, computed tomography, etc.) [13, 14].

Physical activity leads to an increase in total daily energy expenditure by a triple effect: first, by energy expenditure spent during physical activity itself, second, by promoting higher excess post-ex- ercise oxygen consumption (EPOC) after physical activity and third, by long-term elevation of RMR [15]. The RMR increases by increasing fat-free mass, but also by physiological processes induced by phys- ical activity. Both of these effects can occur as a con- sequence of long-term training but also as a conse- quence of a single training session. After a single training session, there is a transient increase in RMR, which actually represents an EPOC during which the additional energy expenditure is used to replenish the anaerobic sources of energy [16]. Some studies have found that long-term training, either aerobic or anaerobic, leads to an increase in RMR, while other studies did not. In fact, in certain number of exami- nees, the RMR actually decreased after long-term training, but the cause of this effect is unknown [17, 18]. It is considered to be a result of down-regulation of uncoupling protein 3 (UCP3) whose role is to im- prove the mechanical efficiency of muscles during exercise [19]. The other possible cause of this effect could be the reaction of the organism to exposure to excessively strenuous physical activity [16]. Zurio et al. pointed out that muscle energy consumption de- pends on the type of muscle fibers [5], while the rep- resentation of certain muscle fibers is mainly deter- mined by the type of physical activity through the process of neuromuscular adaptation to training [20]. Resistance training will develop the energy capacity in the direction of anaerobic energy system, while the continuous (steady-state) training will generally develop energy capacity in the direction of aerobic energy system. Fast-twitch IIa (fast oxidative-glyco-

Abbreviations BMR – basal metabolic rate TDEE – total daily energy expenditure RMR – resting metabolic rate FFM – fat-free mass EPOC – excess post-exercise oxygen consumption UCP3 – uncoupling protein 3 BW – total body weight Ht – height Db – density of the body Σ7SKF – the sum of seven skinfolds FM – fat mass SM - skeletal muscle mass BMI - body mass index

Graph 1. Components of total daily energy expenditure (TDEE) - modified according to Hall and Katch Grafikon 1. Komponente ukupne dnevne energetske potrošnje (TDEE) – modifikovano prema Halu (Hall) [1] i Kaču (Katch) [2]

Thermic effect of food

Termogeni učinak hrane

10%

Psysical actvity Fizička

aktivnost 15-30%

BMR Bazalna

energetska potrošnja 50-70%

Arousal/ Budnost (RMR- BMR) 10%RMR

Energetska potrošnja mirovanja 60-75%

Slavić D, et al. Different Types of Training and Weight Loss274

lytic) and fast-twitch IIx (fast-glycolytic) fibers have a greater amount of myofibrils and the ability to gen- erate more adenosine triphosphate (ATP) that allows them to produce rapid and powerful muscle contrac- tions that are crucial for dominantly anaerobic sports. Slow-twitch I fibers (slow-oxidative), on the other hand, are better vascularized and contain higher amounts of mitochondria and myoglobin, thus get- ting most of their energy out of aerobic sources [21].

The aim of this study was to assess values of an- thropometric parameters and parameters of resting energy expenditure of athletes engaged in different types of training and to determine whether different types of training, practiced by athletes for at least two years back, affect RMR, as well as to determine whether the differences in RMR and anthropomet- ric parameters are statistically significant among these athletes.

Material and Methods

Participants The study included a total of 42 young, male

Caucasian athletes who were divided into two groups. The first group included 21 athletes who were engaged predominantly in aerobic training, while the second group of 21 athletes was predom- inantly engaged in anaerobic type of training. Sports were classified according to Mitchell clas- sification of sports [22]. The inclusion criteria were: athletes engaged in a certain type of training for at least two years back, three times a week, and 90 minutes per training session. Exclusion criteria were: endocrine disorders, acute infectious disease, and use of substances that could affect the level of RMR. Prior to the study, after receiving clear in- formation about the study protocol, all of the par- ticipants gave their informed consent. All of the measurements were performed at the Laboratory of Functional Diagnostics of the Department of Phys- iology, Faculty of Medicine. The research was ap- proved by the Ethics Committee for Clinical Re- search of the Faculty of Medicine.

Anthropometric measurements Anthropometric assessments included the fol-

lowing measurements: total body weight (BW), height (Ht), skinfold thicknesses, and body circum- ferences. The BW was measured on a medical beam scale (precision of 0.1 kg) with subjects lightly dressed. The Ht was measured using a stadiometer with a precision of 0.1 cm; barefoot participants were standing heels together and their heads in the Frankfurt plane. Skinfold thicknesses (pectoral, subscapular, midaxillary, biceps, triceps, abdomi- nal, mid-thigh, medial calf, suprailiac, supraspinale) were measured on the right hand side using the Harpenden caliper with the precision of 0.2 mm, while the circumferences (forearm, relaxed arm, flexed and tensed arm, chest, gluteal, mid-thigh and calf) were measured using a flexible tape measure with the precision of 1 mm, also on the right hand

side [23, 24]. Also, biepicondylar femur and hu- merus breadths were assessed using Holtain Bi- condylar Vernier caliper with a precision of 0.1 cm.

From the obtained parameters, density of the body (Db) was first calculated using the Jackson and Pol- lock equation [25] for male athletes aged ≥ 20 years:

D b =1 , 11 2 - 0 , 0 0 0 4 3 4 9 9 * ( Σ 7 S K F ) + 0,00000055*(Σ7SKF)2 – 0, 00028826*(age),

with Σ7SKF representing summed up values of pectoral, midaxillary, triceps, subscapular, abdom- inal, suprailiac and mid-thigh skinfold thickness.

Furthermore, the percentage of fat mass (FM%) out of Db was calculated using the Siri equation [26]:

FM (%) = ((4,95/Db)-4,5)*100 Based on the calculated FM (%), the absolute

value of the amount of the body FM (kg) was de- termined. Fat-free mass (FFM) was calculated by subtracting the FM (kg) from the total BW (kg) (FFM = BW - FM).

Lee et al. conducted an imaging study of 244 par- ticipants aged 20 – 81, proposing a predictive equa- tion for estimation of the total skeletal muscle mass (SM) (kg), based on anthropometric measurements (height, skinfold thickness, limb girths, sex, age and race (so called, skinfold-circumference model) [27], which we used to estimate the total SM of an athlete:

SM (kg) = Ht × (0.00744 × CAG2 + 0.00088 × CTG2 + 0.00441 × CCG2) + 2.4 × sex - 0.048 × age + race + 7.8

with: Ht - height; CAG - corrected arm girth; CTG - corrected thigh girth; CCG - corrected calf girth; sex - 1 for males and 0 for females; race - -2.0 for Asians, 1.1 for African Americans and 0 for Caucasians or Hispanics. Corrected limb girths = limb girth - (π x skinfold of proper limb).

Resting metabolic rate measurement Nowadays, indirect calorimetry is assumed to

be a gold standard for measuring RMR [28]. It is more convenient to perform compared with direct calorimetry, which measures the amount of heat generated by using much more sophisticated equip- ment. Indicators of resting energy expenditure were assessed by evaluating RMR using the FitmatePro (Cosmed, Rome) at the Laboratory of Functional

Graph 2. Differences in body composition of two ex- amined groups (* p < 0.05) Grafikon 2. Razlike u telesnom sastavu dve ispitivane grupe (* p < 0,05)

Aerobic training Aerobni trening

Anaerobic training Anaerobni trening

Body weight* Telesna masa* Fat tree

mass* Bezmasna

masa*

Skeletal muscle mass*

Skeletna mišićna masa*

Fat mass

Masna masa

Med Pregl 2019; LXXII (9-10): 272-279. Novi Sad: septembar-oktobar. 275

Diagnostics of the Department of Physiology, Fac- ulty of Medicine. The RMR was measured in the morning in a thermoneutral environment, i.e. air temperature of 22 – 25° C. The subjects were in- structed in advance about the methodology of the study and it was explained to them which conditions were necessary to avoid that might influence RMR values: recent physical activity, thermic effect of food, acute diseases or some anabolic/catabolic sub- stances. The most important criteria required ath- letes not to engage in any intense physical activity 36 hours prior to the measurement, to exclude ef- fects of excess post-exercise oxygen consumption on RMR. It was also required not to consume food, alcohol, caffeine or nicotine 12 hours before the testing. To avoid effects of recent physical activity, the participants came to the lab either by a motor vehicle or on foot, walking leisurely and slowly. The measurement was performed under the conditions of psychophysical relaxation and after the partici- pants had a good night’s sleep. Before the measure- ment was performed, the subjects had been resting in a seated position for at least 15 minutes and then they lied down for 15 minutes with a mask on their faces, through which the FitmatePro measured the oxygen consumption. From these values, the inte- grated software calculated the values of RMR.

Afterwards, relative indices of resting energy expenditure were calculated by dividing the obtained values of RMR with total BW, FFM and total SM mass (RMR/BW, RMR/FFM and RMR/SM).

The obtained results were statistically processed in Microsoft Excel 2013 and Jeffrey’s Amazing Sta- tistical Program (JASP, ver. 0.8.0.1.). Pearson’s level of correlation (r) of RMR values with different anthropometric parameters was calculated and Stu- dent’s t-test was used to determine if there were any statistically significant differences between the an- thropometric and metabolic parameters of two ex-

amined groups. The value of p < 0.05 was consid- ered as statistically significant.

Results

The mean age of the participants (n = 42) was 21.76 ± 2.32 years, mean height 182.4 ± 6.5 cm, total BW 79.98 ± 12.09 kg, body mass index (BMI) 24 ± 3.14 kg/m², body fat percentage 9.33 ± 5%, total SM percentage 44.8 ± 3.42%, and mean RMR was 2461.81 ± 394.38 kcal/24 h. No statistically signifi- cant differences were found in age, height, body fat percentage, muscle mass percentage and RMR (p > 0.05) between the two groups of athletes, while the parameters of total BW, BMI, FFM and total SM mass showed statistically significant differences between the groups (p < 0.05) (Table 1). Significantly higher values were found in the group of athletes engaged in anaerobic training in the parameters of body mass (84.52 ± 13.73 vs. 75.43 ± 8.25 kg), BMI (25.29 ± 3.64 vs. 22.71 ± 1.86 kg/m2), FFM (75.14 ± 8.95 vs. 69.06 ± 6.33 kg) and total SM mass (37.93 ± 5.08 vs. 33.36 ± 3.07 kg). These differences in body composition are presented in Graph 2.

The level of correlation between RMR and basic anthropometric parameters, skinfold thickness and body circumference was analyzed in each group as well as in all the participants (Table 2). Since the subjects in our investigation were of the same age, no statistically significant correlation regarding their age was found (p > 0.05). The statistically most signifi- cant (p < 0.001) correlation was between RMR and FFM, SM mass and total BW (r = 0.563, 0.553, and 0.542, respectively). There was also a statistically significant correlation between the BMI, Ht and FM (Table 2). In regard to skinfolds, only the suprailiac showed a statistical correlation with RMR value. In contrast, all of the body circumferences and breadths showed significant correlation with RMR, especially

Table 1. Descriptive characteristics of examined groups Tabela 1. Deskriptivne karakteristike ispitivanih grupa

Aerobic training/Aerobni trening N/br = 21

Anaerobic training/Anaerobni trening N/br = 21

Age (years)/Uzrast (godine) 22.05±2.67 21.48±1,94 Ht (cm) 182.12±6.06 182.69±7.06 BW (kg) 75.43±8.25 84.52±13.73* BMI (kg/m2) 22.71±1.86 25.29±3.64* FM (kg) 6.38±2.64 9.38±7.58 FM (%) 8.26±2.79 10.4±6.41 FFM (kg) 69.06±6.33 75.14±8.95* SM (kg) 33.36±3.07 37.93±5.08* SM (%) 44.36±2.32 45.24±4.13 RMR (kcal/24h) 2473±367 2451±429 * p<0,05; Legend: Ht – height; BW – total body weight; BMI – body mass index; FM – fat mass; FFM – fat-free mass; SM – total skeletal muscle mass; RMR – resting metabolic rate Legenda: Ht – telesna visina; BW – ukupna telesna masa; BMI – indeks telesne mase; FM – masna masa; FFM – bezmasna masa tela; SM – ukupna skeletna mišićna masa; RMR – energetska potrošnja mirovanja

276

the femur biepicondylar breadth and maximum calf girth (r = 0.535 and 0.498, respectively). Scatter plots displaying the correlation between RMR and certain parameters are shown in Graph 3.

The measured RMR values in aerobic and anaer- obic groups were similar (2472.71 ± 367.14 vs. 2450.9 ± 428.72 kcal/24 h) and there was no statis- tically significant difference between these two groups (p > 0.05). However, by calculating the rela- tive indices of resting energy expenditure, i.e. divid- ing the RMR values by total BW, FFM and total SM mass, statistically significant differences were found between the two groups, with significantly higher

values in the aerobic group (RMR/BW was 32.98 ± 4.94 vs. 29.15 ± 3.7 kcal/kg/24 h, p = 0.07; RMR/ FFM was 35.92 ± 4.98 vs. 32.58 ± 3.85 kcal/kg/24 h, p = 0.02; RMR/SM was 74.37 ± 10.45 vs. 64.63 ± 7.59 kcal/kg/24 h, p = 0.001). Graph 4 shows differ- ences in relative indices of resting energy expendi- ture between the two groups of athletes, with indi- cated level of statistical significance.

Discussion

Exercise on a regular basis is very important for both competitive and recreational athletes. Apart

Slavić D, et al. Different Types of Training and Weight Loss

Table 2. Correlation (Pearson’s r coefficient) between the resting metabolic rate and anthropometric parameters in groups engaged in different types of training and its statistical significance Tabela 2. Korelacija (Pearsonov r koeficijent) energetske potrošnje mirovanja sa antropometrijskim paramet- rima u grupama na različitom tipu treninga i njena statistička značajnost

Types of training/Tipovi treninga Aerobic/Aerobni Anaerobic/Anaerobni All/Svi r p r p r p

Ht/Telesna visina (cm) 0.163 0.479 0.509 * 0.018 0.361 * 0.019 BW/Ukupna telesna masa (kg) 0.360 0.109 0.733 *** < .001 0.542 *** < .001 BMI/Indeks telesne mase (kg/m2) 0.361 0.107 0.552 ** 0.010 0.425 ** 0.005 FM/Masna masa (kg) 0.143 0.535 0.443 * 0.044 0.329 * 0.034 FFM/Bezmasna masa tela (kg) 0.409 0.066 0.749 *** < .001 0.563 *** < .001 SM/Ukupna skeletna mišićna masa (kg) 0.406 0.068 0.789 *** < .001 0.553 *** < .001 Skinfold thicknesses/Debljina kožnih nabora Chest/Grudni* -0.103 0.656 0.302 0.183 0.191 0.225 Subscapular/Subskapularni* 0.005 0.981 0.386 0.084 0.262 0.094 Midaxillary/Srednji aksilarni* 0.205 0.373 0.264 0.248 0.207 0.189 Biceps/Biceps 0.122 0.597 0.137 0.555 0.113 0.476 Triceps/Triceps* -0.152 0.510 0.107 0.645 0.022 0.890 Abdominal/Abdominalni* 0.055 0.814 0.374 0.095 0.254 0.104 Suprailiac/Suprailijačni* 0.313 0.167 0.457 * 0.037 0.385 * 0.012 Supraspinale/Supraspinalni 0.364 0.105 0.287 0.207 0.278 0.075 Mid-thigh/Natkolenica* 0.047 0.840 0.230 0.315 0.164 0.299 Medial calf/Potkolenica 0.173 0.454 0.253 0.269 0.199 0.206 Σ 7SKF/Zbir debljina sedam(*) kožnih nabora 0.094 0.684 0.347 0.124 0.255 0.104 Body circumferences/Telesni obimi Forearm/Podlaktica 0.257 0.262 0.642 ** 0.002 0.416 ** 0.006 Relaxed upper arm/Relaksirana nadlaktica 0.264 0.248 0.658 ** 0.001 0.398 ** 0.009 Flexed upper arm/Fleksirana nadlaktica 0.262 0.251 0.677 *** < .001 0.384 * 0.012 Chest/Grudi 0.405 0.068 0.618 ** 0.003 0.462 ** 0.002 Waist/Struk 0.222 0.334 0.609 ** 0.003 0.446 ** 0.003 Hips/Kukovi 0.519 * 0.016 0.415 0.061 0.388 * 0.011 Mid-thigh/Natkolenica 0.311 0.169 0.601 0.004 0.459 ** 0.002 Calf/Potkolenica 0.372 0.097 0.650 0.001 0.498 *** < .001 Corr. arm girth/Korigovan obim nadlaktice 0.347 0.123 0.644 ** 0.002 0.411 ** 0.007 Corr. thigh girth/Korigovan obim natkolenice 0.322 0.155 0.549 ** 0.010 0.437 ** 0.004 Corr. calf girth/Korigovan obim potkolenice 0.324 0.151 0.615 ** 0.003 0.476 ** 0.001 Breadth/Debljina Femur biepicondylar/Femura 0.358 0.111 0.685 *** < .001 0.535 *** < .001 Humerus biepicondylar/Humerusa 0.333 0.141 0.404 0.069 0.368 * 0.016 * p < .05, ** p < .01, *** p < .001

from having beneficial effects on a wide array of physiological functions, physical activity also pre- vents the onset of obesity and its complications, especially in adulthood [29, 30]. The BMI is an in- dicator that can show if an individual is overweight or underweight, and being easily and widely used for calculation of overweight and obesity, BMI is frequently used as an important tool in health risk assessment. The higher the BMI, the higher is the

risk of cardiovascular disease and other associated chronic diseases [31]. Previous studies have shown that BMI is not a good indicator of the amount of fat tissue in athletes, since higher BMI may also indicate increased amount of muscle mass, not nec- essarily fat [32]. In our study, BMI values were sta- tistically significantly higher in the group engaged in anaerobic training. This result is expected, con- sidering that there was also a significant statistical difference in total BW between the two groups and BMI is a parameter derived from this value.

Our study showed a lower percentage of body fat in both groups of athletes, compared to the aver- age values in the general population. Although this percentage was slightly higher in subjects engaged in anaerobic type of training, this difference was not statistically significant. Optimal values of body fat percentage in our participants range very low and do not differ significantly between groups, so it excludes the influence of this body compartment on RMR variability. Exactly this speaks in favor of FFM in our participants, being one of the main de- terminants of body weight, and thus also RMR.

Determining the contribution of different body compartments in athletes, i.e. determining their body composition is very important in their profession be- cause the ratio of fat to FFM affects sports achieve- ment. Furthermore, knowing the metabolic param- eters, i.e. energy expenditure at rest or during physi- cal activity, completes the physiological profile of each athlete and provides directions for corrections of their training process. Many studies point towards the relationship between anthropometric and meta- bolic characteristics on one hand, and risk of cardio- vascular and metabolic diseases on the other. These are the reasons why assessment and interpretation of anthropometric and metabolic variables in sports medicine should receive special attention [33].

Numerous studies show that engaging in sports leads to an increase in the values of RMR. Such results have been obtained in the studies that are concerned with the impact of aerobic training on RMR values [34], but also in the studies concerning the impact of anaerobic training [35, 36]. Our re- search revealed somewhat higher values of RMR in athletes engaged in aerobic type of training, but this difference was not statistically significant. It should be noted that subjects in different groups did not have the same amount of FFM, which actually rep- resents the most influential factor determining the RMR of an individual, while the fat mass has a low rate of metabolic activity and thus has a small con- tribution to RMR [37].

For that reason, in our study, the ratios of resting energy expenditure per kilogram of BW, FFM and SM mass were calculated, then these newly ob- tained values were compared between two groups and statistically significant differences were ob- tained. Higher values of these relative indices of metabolic expenditure were obtained in athletes engaged in aerobic type of training and, taking into account that there were no statistically significant

Med Pregl 2019; LXXII (9-10): 272-279. Novi Sad: septembar-oktobar. 277

Graph 4. Differences in relative indices of metabolic expen- diture between two groups (values in kcal/kg/24 h) (* p < 0.05) Grafikon 4. Razlike u relativnim pokazateljima me ta- boličke potrošnje između dve grupe (vrednosti su u kcal/ kg/24 h) (* p<0,05)

RMR/BW* Energetska potrošnja

mirovanja/Telesna masa

RMR/FFM* Bezmasna masa tela

RMR/SM* Telesna

mišićna masa Aerobic training

Aerobni trening 32.98 35.92 74.37 Anaerobic training

Anaerobni trening 29.15 32.58 64.63

RMR/BW* Energetska potrošnja

mirovanja/ Telesna masa

RMR/FFM* Energetska potrošnja

mirovanja/ Bezmasna masa tela

RMR/SM* Energetska potrošnja

mirovanja/Telesna masa mišića

Graph 3. Correlation plots showing the correlation be- tween resting metabolic rate (vertical axis, values in kcal/24 h) and anthropometric parameters (horizontal axis, values in kilograms except height and biepicondy- lar femur breadth which are expressed in centimeters) Grafikon 3. Korelacioni grafikoni sa predstavljenom kore- lacijom između energetske potrošnje mirovanja (vertikalna osa, vrednosti u kcal/24 h) i antropometrijskih parametara (horizontalna osa, vrednosti u kilogramima, osim visine i debljine femura koji su izraženi u centimetrima)

Feat free mass Bezmasna masa tela

Femur breadth Debljina butine

Skelatal muscle mass Skeletna masa mišića

Height Telesna visina

Body weight Telesna masa

Feat mass Masna masa

278

differences in body fat percentages between the groups, it can be concluded that oxygen consumption per kilogram of FFM was higher in the group of ath- letes engaged in aerobic type of training. Such results can be explained by the fact that aerobic type of train- ing develops the metabolism of an individual in the direction of aerobic capacity, which due to structural differences in basal conditions requires greater amounts of oxygen than anaerobic [20, 21], that is, the SM mass, in which slow-twitch I fibers are found, predominant- ly has a higher rate of metabolic activity. The absolute amount of SM mass makes the biggest contribution to the FFM compartment and therefore represents the component with the highest influence on RMR [3] which opens opportunities for adequate weight loss training recommendations which are in line with con- temporary standpoints on which type of training is more effective against obesity [38].

This research provides potential recommenda- tions about which type of training should be applied in order to increase the RMR and thus, to achieve the desired body weight in the long run. The limita- tions of this research include a relatively small sam- ple size, young age and lean body composition of the participants, as well as the absence of EPOC meas- urements. It is necessary to increase the number of subjects with a wider range of age and nutrition. The most reliable data would be gathered if 24-hour en-

ergy expenditure was measured in metabolic cham- bers equipped with different exercise equipment. Then the impact of EPOC in total daily energy ex- penditure (which surely is not negligible) could be evaluated with a great deal of confidence.

Conclusion

Analyzing the anthropometric parameters of ath- letes engaged in two different types of training, aerobic and anaerobic, significantly higher values of body weight, body mass index, fat-free mass and skeletal muscle mass were found in subjects engaged in anaerobic type of training (p < 0.05). Although a higher percentage of body fat was measured in these subjects, this difference was not statistically sig- nificant. Absolute measured values of resting meta- bolic rate did not show significant differences be- tween the two groups, but a statistically significant difference was found when energy expenditure val- ues were expressed through relative indices, com- pared to the total, fat-free and muscle mass with significantly higher values in athletes engaged in aerobic type of training (p < 0.05). Since the resting metabolic rate mostly depends on the fat-free mass, our research speaks in favor of higher rate of meta- bolic processes in this body compartment in athletes whose training is predominantly aerobic.

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Rad je primljen 18. IX 2019. Recenziran 27. IX 2019. Prihvaćen za štampu 30. IX 2019. BIBLID.0025-8105:(2019):LXXII:9-10:272-279.

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