Comparison of MFO and FAT max levels during two types of aerobic exercise in non-athlete girls

Transcription

1 International Journal of Sport Studies. Vol., 2 (9), , 2012 Available online at ISSN VictorQuest Publications Comparison of MFO and FAT max levels during two types of aerobic exercise in non-athlete girls Koosar Forohi 1, SaeidShakerian 2 *, Masood Nikbakht 3, AbdolhamidHabibi 3, 1- MA in sport physiology, Department of physical education and sport science, Shahid Chamran University of Ahvaz, Iran 2- Assistant professor in sport physiology, Department of physical education and sport sciences, Shahid Chamran university of Ahvaz, Iran 3- Associate professor in sport physiology, Department of physical education and sport sciences, Shahid Chamran university of Ahvaz, Iran *Corresponding Author: sashakeryan@gmail.com Abstract Introduction: The present study aims to compare Fat oxidation and MFO levels and the intensity during which the FAT max occurs during two types of aerobic exercises (i.e., running on a treadmill and pedaling on a static bike). Therefore, 15 non-athlete female students with average age of ± 1.33 years, height of ± 3.15 centimeters, weight of ± 4.41, BMI of ± 1.78 and Fat percent of ± 3.98, performed the incremental activity on static bike and treadmill. Respiratory gas exchange and heart rate was recorded and levels of fat oxidation were measured using stoicheiometry equations. We used variance analysis test with repetitive measurements, t-test and Pearson correlation test to analyze the data. Results of the current study showed that maximal oxidation (0.20 ± 0.03 g/min vs ± 0.02 g/min) and maximum consumed oxygen (31.24 ± 1.95 ml/kg/min vs ± 1.52 ml/kg/min) was significantly higher during running on treadmill compared to pedaling on a static bike, respectively (P 0.05). However the level of FAT max did not show any significant difference during two types of physical activity (VO2max of ± 1.18 on treadmill vs. VO2 max of ± 1.04 on the static bike). Results of this study suggest that there is a significant difference between two types of exercise in terms of fat oxidation rate during relative intensities. Also it should be mentioned that fat oxidation during activities in which there are involved more muscular mass, is higher. Key words: FAT max, MFO, Stoicheiometry equations Introduction The amount of consumed energy during physical activity is almost provided through combination of fat metabolism and carbohydrate. Consumption of these two resources as substrates depends on food diet, muscles' reserve of glycogen, intensity and duration of activity and the type of exercise (Venables et al., 2005). Reports show that exercise intensity is one of the factors affecting consumption of substrate. Carbohydrate oxidation increases by increase of intensity of activity. However the portion of fat oxidation increases during low to middle intensities and then decreases during middle to high intensities (Achten et al., 2002; Achten et al., 2003; Friedlander et al., 1998; Gibney et al., 2003). Running and cycling are two common types of physical activity which are used mostly during leisure and rehabilitation programs (Lafortuna et al., 2008). Nonetheless, there are reported different physiologic, metabolic, cardiovascular and ergogenic responses toward running and pedaling among obese and normal individuals (Achten et al., 2002; Faulkner et al., 1971). It seems that substrate oxidations differ, during running and cycling in relative and particular intensities (Achten et al., 2002). 444

2 Some researchers have studied the maximal fat oxidation (FAT max ) (Romijn et al., 1993; Van Loon et al., 2001). The level of fat oxidation of men (Romijn et al., 1993) and women (Romijn et al., 2000) are investigated during VO 2 peak of 25, 65, 85% for time periods of 120,120 and 30 minutes on static bike. Results suggest that oxidation level in both genders during the VO 2peak of 65% is higher than other intensities. There is too little information available about the effect of exercise type on fat oxidation. Achten et al. (2003) used running and cycling in order to investigate the physiological effects of endurance exercises. It seems that substrate oxidations differ, during running and cycling in relative and particular intensities. Another study investigates the fat oxidation of athlete participants during running and cycling in several intensities (Mohebbi et al., 2009). Results of that study showed that Respiratory Exchange Ratio (RER) during running is significantly lower than cycling (Mohebbi et al., 2009). Also the study by Nieman et al. (1998) reports the fat oxidation of participants to be 16% higher during the test on treadmill, than the rate during the test on static bike (Nieman et al., 1998). However, other showed that there is no difference between participants taking test of static bike and treadmill in terms of RER or fat oxidation rates (Arkinstall et al., 2001; Houmard et al., 1991). Most of the studies about fat oxidation have been done using a single static bike or treadmill and a limited number of studies have compared fat oxidation using both static bike and treadmill; while the energy consumption and fat oxidation models during the exercise on static bike and treadmill are different. Therefore the present study aims to find and investigate the differences between these two types of aerobic exercise in terms of fat oxidation. Materials and Methods Participants of the present semi-empirical study were 15 non-athlete females (with an average age of ± 1.33 years, height of ± 3.15 centimeters, weight of ± 4.41 kgs, BMI of ± 1.78 and fat percent of ± 3.98 ) who have been selected after an announcement. They did not suffer from any particular disease at the beginning of the study. They have not been performing any regular exercise during the last 2 years. Before starting the test they all attended an introductory session and got familiar with materials and methods of measurement. Their height and weight were measured and the fat percentage was measured through bioelectrical impedance technique (Inbody 3.3). Exercise tests were taken from 8 to 12 a.m. Prior to tests they were on fast for 10 to 12 hours and they were asked not to perform any intensive physical activity at least for one day prior to the test. At the first technique participants performed one incremental running test on treadmill (Saturn model, product of HP/Cosmuse) (Venables et al., 2005). This test was so: at the very beginning the participants, after 5 minutes of warm-up, started their activity on the treadmill with a speed of 3.5 km/h and a slope of 1%. Then the speed was increased every 3 minutes by 1 km/h up to the point where the speed reached 6.5 km/h. Here the speed is stable and slope gets increased every 3 minutes by 2% up to the point where RER becomes 1. After this stage the speed was increased every 1 minute by 1 km/h, until the time when participants got exhausted. The aim of the last stage of the test was to measure the rate of VO 2 max. At the second technique we used incremental protocol of running on a static bike in order to measure the substrate oxidation of athlete participants (Achten et al., 2003). During this test, after 5 minutes of warm-up, the participants started their activity with a workload of 25 watts on static bike (Monarch Ergometer, E839E model). The workload increases by 10 watt every 3 minutes, until the point where the participant gets exhausted. The intensity of pedaling was 50 cycles per minute. The heart rate of participants was recorded regularly during the test, using a Polar electrocardiograph. The amount of consumed oxygen and exhaled carbon dioxide were measured breath to breath using a Gunshorn gas analyzer. The average consumed oxygen (VO 2 ) and produced CO2 (VCO 2 ) during the final 2 minutes of every phase of the test was measured until the point where the RER reached less than 1. Then, assuming that the amount of urinary nitrogen is negligible, we measured fat oxidation using Freyn's stoichiometry equations as follows (Freyn, 1983) VCO VO 2 = Fat oxidation rate (g/min) The average rate of VO 2 during the last 2 minutes of every phase of the test was measured and divided by VO 2max to find the intensity of that phase in VO 2 max percent. The highest amount gained 445

3 through equation 1, is maximal fat oxidation and its corresponding intensity of activity (Houmard et al., 1991). We used variance analysis test with repetitive measurements to compare the changes in fat oxidation during both types of activity. We used paired T-test to compare the average MFO and FATmax during the two types of exercise. We also used Pearson correlation coefficient in order to investigate the relationship between MFO and VO 2max. Results Table 1 shows the mean, standard deviation and physiological and anthropometric characteristics of participants. Individual details of participants Table 1: Descriptive characteristics of participants Age (years) Height (cm) Weight (kg) BMI (kg/m 2 ) BF % Mean ± ± ± ± ± 3.98 Table 2 shows the data for FAT max, VO 2max and MFO of participants. According to the data in table 2, the average VO2max of participants on a treadmill is (ml/kg/ min) and (ml/kg/ min) on the static bike. Also the maximal fat oxidation during activity on treadmill was higher than static bike; however the FAT max rate in treadmill was lower than static bike. Table 2: Mean and Standard deviation of research variables Group Treadmill Static bike Significance level (p) Variable VO 2max (ml/kg/min) ± ± FAT max (VO 2max ) ± ± MFO (g/min) 0.20 ± ± * Significance level of 0.05 The intensity of activity on treadmill during several phases is almost similar to activity on static bike. Results of statistical test showed, also, that there is no difference between intensities of both activities (P 0.05) (Table 2). The amount of MFO during activity on treadmill (0.20 ± 0.03 g/min) was significantly higher than the activity on static bike (0.14 ± 0.02 g/min) (P 0.05) Fatox (g/min) stage 1 stage 2 stage 3 stage 4 stage 5 stage 6 stage 7 treamil static bike Figure: Fat oxidation amount during exercise on treadmill and static bike 446

4 The amount of FAT max on treadmill is 42.43% and the maximal consumed oxygen on static bike is 47.47% which is not a significant difference. Results showed that there is a significant difference between the two types of exercise in terms of maximal fat oxidation (P 0.05); however there was no significant difference between them in terms of intensity when the maximal fat oxidation occurs. Also the amount of fat oxidation during several intensities in treadmill test was significantly higher than the amount on static bike test (P 0.05). Discussion and Conclusion The present study was conducted in order to compare the amount of maximal fat oxidation following one session of incremental exercise during two techniques among non-athlete female students. The ability to diagnose the point for optimum oxidation of fat resources as a fuel in exercise protocols have always been of importance and different results have been reported in different groups. Activity in several exercise programs and with variable protocols, in which fat resources will be used optimally, is very important for all communities. Therefore, the present study tried to estimate this optimum intensity in two groups of non-athletes and during two types of exercise protocol. Results of the present study showed that fat oxidation on treadmill during VO 2max of 42% reached its maximum level and more increase of the intensity led to decrease of fat oxidation. Fat oxidation on static bike during VO 2max of 47% reached its maximum level, but more increase of the intensity led to decrease of fat oxidation. The amount of fat oxidation during similar relative intensities is different among different exercise activities (running and cycling). Scientific evidences show that less muscular mass are involved during the activity on static bike compared to treadmill (Hermansen, 1969). On the other hand, there is a positive relationship between release of catecholamine during activity and active muscular mass (Davies et al., 1974). Achten et al. (2003) showed that density of catecholamines is higher during running compared to pedaling. Since the catecholamines are effective activators for lipolysis during exercise activity (Gibney et al., 2003; Romijn et al., 1993; Powers et al., 2001) and their density during running is higher than during pedaling, therefore fat oxidation during running is higher than pedaling. Another theory proposed by Achten et al., (2003) regarding the higher level of fat oxidation during running, is related to active muscular mass. Workload during activity on static bike is divided by less muscular fibers, compared to treadmill activity. Thus, since every fiber needs more energy each time, incurs more metabolic pressure and it is probable that increase of metabolic pressure and needing more energy by each fiber, can be done only by increasing the oxidation portion of carbohydrate (Achten et al., 2003). Therefore, it seems that carbohydrate oxidation is higher during activity on static bike. Knechtle et al., (2004) suggest that the reason behind higher level of fat oxidation during activity on treadmill compared to static bike is due to the fact that there is more muscular tension during activity on static bike compared to treadmill and thus the movement fibers type II are more involved during cycling. On the other hand, movement fibers types II have higher glycolytic capacity and lower oxidative capacity. Therefore, carbohydrate oxidation is higher during cycling compared to running (Knechtle et al., 2004). Scientific reports show that since more muscular mass is involved during the activity on treadmill compared to static bike, therefore VO2 max rate are 7 to 10 % higher during the activity on treadmill compared to static bike (Glass et al., 2004; Snyder et al., 1993). Therefore regarding the importance of difference of maximum consumed energy during two types of exercise (running and cycling) in studies by Houmard et al., (1991) and Arkinstall et al., (2001), activity on treadmill have been performed with higher heart rate and consumed energy compared to static bike. As the activities were done during several intensities in the present study, it is possible to compare metabolic variables during similar exercise intensities in both exercise activities (with regard to VO 2 max of each exercise activity). However, VO 2 max rate was higher on treadmill compared to static bike. In general, results of the present study showed that maximal fat oxidation, and also fat oxidation rate during several intensities on treadmill was significantly higher than static bike. Nonetheless, there was no difference between the two aerobic activities in terms of the point where maximal fat oxidation occurs. These differences might stem from physiological mechanisms caused by exercise program. However, fat oxidation level during exercise in different groups and communities, especially elders, cardiovascular patients and obese people is of importance and requires further studies to be done on fat oxidation and exercise programs. 447

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