Dr.Biol., Professor R.V. Tambovtseva
Associate Professor, PhD J.L. Voytenko
Head of Laboratory O.S. Zhumaev
Master's student I.S. Walter
Russian State University of Physical Culture, Sport, Youth and Tourism (GTsOLIFK), Moscow

Keywords: aerobic capacity, caffeine, power, oxygen consumption, respiratory rate, ventilatory equivalent, respiratory quotient.

Abstract

Objective of the research was to study the effect of caffeine-sodium benzoate on aerobic capacities of elite athletes. The graded exercise test "to failure" was performed on a treadmill and a cycle ergometer. We measured working power, working time, heart rate (HR), and such respiratory function indices as oxygen consumption, respiratory rate, ventilatory equivalent, respiratory quotient, and oxygen utilization rate. According to the results of the experiment, there was no significant increase of the aerobic capacity indices; however, one can see prerequisites for the increment of the general physical working capacity indices.

Introduction. Nowadays, it becomes rather a topical issue to use ergogenic aids in sport practice [1, 2, 3, 5, 6]. The interest in caffeine as an ergogenic aid was developed owing to the research carried out by D.L. Costill [8] more than 40 years ago. Caffeine is an antagonist of adenosine receptors and a stimulant of the methylxanthine class. There are positive and negative effects of caffeine on the human body. However, most research works are for the non-specialist reader, and scientific studies give conflicting results, especially on the drug dosage [4, 7]. It is known that caffeine overdose induces various side effects. In addition, it should be noted that the doping threshold of the cardiac output is 12 mcg-dL-l and the NCAA one is 15 mcg-dL-l.

Objective of the research was to study the effect of caffeine sodium benzoate on aerobic capacities of elite athletes.

Methods and structure of the study. The experiment was carried out in the laboratory of bioenergy of muscular activity at the N.I. Volkov Sport Biochemistry and Bioenergy Department. The study was conducted at no risk for the people’s health in compliance with all the humanity and ethical provisions (2000 Helsinki Declaration, EU Directive 86/609). Subject to the study were 32 elite athletes practicing different sports who gave their informed consent on the experiment. Initially, all the subjects were tested before the preparation administration. In subsequent experiments, еру caffeine sodium benzoate preparation was taken per os as a single dose of 4 mg per 1 kg of body weight 60 minutes before the treadmill and cycloergometer graded exercise test "to failure". Before the experiment, the subjects did not take any caffeinated food and drinks during one week. Additionally we studied the placebo group (who took microcrystalline cellulose). We measured working power, working time, heart rate (HR), and such respiratory function indices as oxygen consumption, respiratory rate, ventilatory equivalent, respiratory quotient, and oxygen utilization rate. The findings were statistically processed using the Statistica 6.0 software and the built-in function of analysis using Microsoft Excel (2007).

Results and discussion. Table 1 presents the aerobic capacity indices while performing the maximal treadmill step test before and after the administration of the preparation.

Table 1. Dynamics of the aerobic capacity indices during maximal treadmill step test with caffeine (n = 16)

The data analysis reveals that the results obtained after the administration of caffeine in the dose of 4 mg/kg during the graded exercise demonstrate only an upward trend in the external load indicators such as: relative and absolute working power on the anaerobic threshold (2.2% and 1.3% respectively), an increase in running speed on the anaerobic threshold and at maximal oxygen consumption (0.5 km/h). Working power at MOC slightly changed, but herewith, working time increased by 39 seconds (however, this increase was statistically insignificant).

While studying the external respiratory indices (respiratory rate, ventilatory equivalent), we detected a statistically significant increase in the respiratory rate, both during the onset of the anaerobic threshold, and at the point of maximum effort (the indices increased by 10% and 4%, respectively).

Studies of the dynamics of changes in the indices of oxygen consumption and carbon dioxide utilization, as well as the cardiovascular system performance failed to reveal any shifts of these indices.

As follows from the data obtained, caffeine in the dose of 4 mg per 1 kg of body weight does not have a due impact on the improvement of aerobic capacities at the tissue level, and only has an excitatory influence on the respiratory center.

As seen from analysis of the data obtained under the influence of caffeine in the same dose, but on the local muscular performance during the graded exercise test, the effect of the preparation on the studied aerobic capacity indices was similar to that on the treadmill. After the administration of the preparation, working power had a tendency to increase - both the absolute power on the aerobic threshold (4%) and at MOC (4%), and the relative power values on the threshold and at MOC (3.4% and 2.8% increase, respectively). At the same time, as in the case of the treadmill test, the ventilatory equivalent indices increased significantly on the anaerobic threshold and on the onset of the maximal oxygen consumption by 6.8% and 8.5%, respectively (p<0.05). An increase was also noted in the maximal respiratory rate by 5 breathes per minute (10.6% at p<0.05). However, we detected one specific feature: when performing the cycle ergometer test, the oxygen utilization rate on the threshold and on the onset of MOC decreased, which, apparently, characterizes greater oxygen sensitivity and lower expired oxygen concentration. Yet, these changes have a tendency to the decrease only, showing no significant differences.      

Therefore, the comparison of the dynamics of the percentage changes in the aerobic capacity indices during the treadmill and cycle ergometer tests under the influence of caffeine in the dose of 4 mg per kg of body weight, allows for the conclusion on the lack of significant deviations, but the indices differing depending on the test type. Based on the analysis of the percentage changes in the indices during aerobic capacity tests of local and global muscle groups, we can state that changes in the indices are generally identical (within the permissible instrumental error), except for the index of oxygen utilization rate. We can assume that the smaller the working muscle group, the more selective the caffeine effect.

According to the findings, the aerobic capacity indices increased insignificantly; however, there are prerequisites for the increment of the general physical working capacity indices.

In the recovery period, during the treadmill workout the aerobic capacity indices changed significantly only after the 15th minute of recovery. Thus, such external respiratory indices as respiratory rate and ventilatory equivalent increased significantly by 25% and 9.5%, respectively (p<0.05), which helps compensate for the oxygen debt by means of lung hyperventilation. The analysis of the aerobic capacity indices when working on the cycle ergometer showed a more rapid recovery of the respiratory and cardiovascular systems compared to the treadmill test.

The respiratory quotient increased significantly when exercising both on a treadmill and on a cycle ergometer. In the recovery period, this index increased rapidly during the 3rd minute to 1.64±0.07 when working on the treadmill and to 1.61±0.04 when working on the cycle ergometer, both in the athletes who were taking the medication and those who were taking placebo. Meanwhile, during the 10th and 15th minutes of recovery, the respiratory quotient decreased significantly, moreover, this decrease was more intense in the athletes who were taking caffeine when working on the cycle ergometer.

Tables 2 and 3 represent the dynamics of the lactate concentration indices while working on the treadmill and cycle ergometer in the recovery period.

Table 2. Dynamics of the capillary blood lactate concentration indices during treadmill graded exercise test (n=16) before and after the preparation administration.

Table 3. Dynamics of the capillary blood lactate concentration indices during cycle ergometer graded exercise test (n=16) before and after preparation administration.

The analysis of the indices of capillary blood lactate concentration during the treadmill and cycle ergometer workouts revealed that the dynamics of the lactate indices was similar to that in the placebo group. There was just a slight upward trend when working on the cycle ergometer. However, the results were statistically insignificant.

To sum it up we can state that caffeine used in the dose of 4 mg per 1 kg of body weight is not effective as it does not cause any significant metabolic shifts at any level, there is only a slight upward trend. Probably, a higher caffeine dose can have an ergogenic effect. However, it should be noted that a safe caffeine dose is within the range from 3 to 6 mg per kg of body weight.

Conclusions:        

1. Changes in the studied indicators while testing local and global muscle groups were the same (within the permissible instrumental error), except for the indicator of oxygen utilization rate.

2. According to the findings, there was no significant increase of the aerobic capacity indices; however, there are prerequisites for the increment of the general physical working capacity indices.

3. Caffeine used in the dose of 4 mg per 1 kg of body weight is not effective as it does not provoke any significant metabolic changes at any level, there is only a slight upward trend.

References

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 Corresponding author: ritta7@mail.ru