Time-dependent effects of short-term intense interval training on dynamic oxygen uptake in girls

Master of Physical Education (Sports Physiology focus)

Abstract

Aim: The purpose of the research was to determine the time-dependent effect of short-term intense interval training on the dynamics of oxygen absorption in girls.

Methodology: For this purpose, 40 volunteer female students of Arak University were randomly selected. 25 ± 5 years, weight 54.30 ± 10.390 kg and height 162.5 ± 10.23 cm participated in this research. The research was semi-experimental with a pre-test-post-test design. The subjects of this research were randomly divided into three groups (N=30) with one training session per week, two training sessions per week, four training sessions per week and a control group (N=10). The exercises of each group consisted of three parts (warming up with a bicycle with a workload of zero watts for four minutes, pedaling a bicycle with a workload of 50 watts in each stage for four minutes and one minute of active recovery between sets, cooling down for a minute). After 3 days of completing the post-test training protocol according to the pre-test, training and control were taken from the group. The results were measured by gas analyzer by breath-by-breath method. To analyze the data, after confirming the normal distribution of the data by the Klomogrove-Smirnov test and examining the difference between the training groups (one, two and four sessions) as well as the effect of the independent variable on the dependent variables (comparison before and after the test of each group), the dependent t-test was used. Data were presented as mean standard deviation. All the statistical operations of the research were carried out by SPSS software, version nineteen, and the significance level of the tests was considered to be P < 0.05. Findings: The results showed that an intense interval training session had no effect on the improvement of oxygen dynamic factors (VO2max, oxygen fraction, and the first and second time constants) (P > 0.05). Two intense interval training sessions were effective in improving oxygen dynamic factors (VO2max, oxygen fraction and second time constant) (P<0.05), but had no effect on reducing the first time constant (P>0.05). Four sessions of intense interval training had a significant effect on the improvement of oxygen dynamic factors (VO2max, oxygen fraction and first and second time constants) (P<0.05).

Conclusion: There is a significant difference between the number of training sessions and their effect on oxygen dynamics, of which the effect of four sessions on the factors (VO2max, oxygen fraction, first and second time constants) was greater. But to improve oxygen dynamics, you can take advantage of the minimum training time, i.e. two training sessions.   Key words: oxygen dynamics, aerobic fitness, periodic intense exercise, oxygen absorption.

1 Introduction

One ??of the sciences that has been developing and evolving over time is sports science, which by passing from the industrial world to modernism and subsequently to postmodernism. And with the advancement of technology in the construction of sports equipment, laboratories, the commercialization and income generation of the role of sports, and the fact that in terms of the political aspect of a country, its athletes are considered to represent the power and civilization of their country, and this is declared as a factor for the well-being and health of humanity and the healing of many diseases. All of these things have caused sports experts to increase their knowledge day by day and increase their efforts to conduct more practical tests and researches (2). Physical inactivity is associated with an increased risk of cardiovascular diseases, diabetes, osteoporosis, obesity and mental problems. Regular physical activity leads to cardio-respiratory health and reduces the risk of cardiovascular diseases such as heart attacks (6). Physical fitness is one of the key factors in a healthy human life, which can be one of the strongest predictors of the state of health. the health of people in the future (6). So that cardio-respiratory endurance has been proposed as a basic component of physical fitness (6). Physical fitness and movement factors are important both in normal people and athletes. In everyday life, physical activity is very useful in the prevention and treatment of many common diseases, especially the cardiovascular system (70, 40). The amount of oxygen consumed as an indirect indicator of cellular respiration, energy cost and movement economy and its related variables in sports physiology and training has caused many Researchers should study the factors affecting its quantity (volume of oxygen) and quality (volume changes per unit of time) (5).Measuring the maximum oxygen consumption [1] is a simple method to determine aerobic fitness (54). Also, VO2max is the most important success factor in endurance sports (6,76). Because V02max does not provide accurate and detailed information of the aerobic test, it is used more than oxygen kinetics [2] for the accuracy of the operation. Heart failure should be used (80). Cardio-respiratory fitness, which is also called cardio-respiratory endurance and cardio-vascular fitness, is the ability of the heart to pump a large volume of oxygen-rich blood to the muscles and subsequently use as much of the muscles as possible (40). Intense and repetitive long exercises with sufficient duration lead to an increase in aerobic parameters such as V02max, movement economy, lactate threshold and oxygen absorption dynamics [62]. In this collection, the importance of the kinetics or dynamics of oxygen consumption (the pattern of sudden increase in oxygen consumption at the beginning of the activity until reaching a uniform stage) compared to other parameters of aerobic fitness in expressing the differences in sports performances, especially in postponing muscle fatigue, has been considered in recent years. Because the quick access to the oxygen consumption needed for the race, especially in endurance athletes, not only reduces the accumulation of metabolites (reducing the volume of the oxygen deficit), but because of the limited anaerobic energy for later use in the race (at the end of a sprint race), it is considered as an important factor (10). V02max is always higher in boys than in girls even before puberty, which is due to the difference in body composition and the larger size of the heart in boys compared to girls (81). On average, women have lower innate aerobic capacity and less muscular strength than men, which is a reflection of socio-cultural influences, body composition and hormonal conditions (83). Studies have shown that the sex-dependent difference in the response of the left ventricular muscle and oxygen delivery is greater in men than in women at the peak of intense physical activity (62). However, the aerobic capacity of trained women is better than sedentary men (82). Previous studies in healthy people have shown that during aerobic exercise, men absorb more oxygen than women, which is due to the difference in the size of men's hearts (54). On the other hand, maximum aerobic power decreases with increasing age, which shows a greater decrease in men than in women (93). The cardiorespiratory system in men differs from each other in some aspects, including: men's hearts are larger than women's hearts, men have 40% more blood volume, men have 11% more red blood cells than women. On average, the cardiorespiratory system in men is 39% larger than the cardiorespiratory system of women, and women's oxygen consumption is 17% less than men's. It is interesting to note that the difference in anaerobic capacity (energy production without oxygen) of men and women is insignificant (84). Similar to men, mitochondrial enzyme aerobic capacity has increased in well-trained women compared to untrained women (18). In general, in the process of growth and maturation and regardless of the size of the human body, human movement is a complex interaction of different physiological responses. Through physiological responses, the body is able to maintain homeostatic balance. This balance between the needs and the answers obtained is dependent on the performance of the cardiovascular, respiratory, muscular system and basic laboratory tests, and it provides the possibility for researchers to discover age and maturity changes in this system. Also, the dynamic responses of oxygen absorption to exercise provide information related to the response of the cardiorespiratory system following a transition from one metabolic state to another (70).  The volume of oxygen consumed is a direct measurement of cellular respiration and energy expenditure is basically a product of cardiac output and oxygen absorption at the cellular level (64). Changes in VO2 when moving from rest to exercise are defined as the dynamics of oxygen absorption (64). Dynamic responses of oxygen to exercise provide comprehensive information regarding cardiorespiratory responses following a change in metabolic status (70). Oxygen uptake dynamics measures the time required to adapt to changes in metabolic load (for example, changing from rest to maximal exercise). Also, oxygen uptake dynamics describes the amount of change in VO2 response related to exercise and is also an indicator for measuring cardiopulmonary fitness (73).