The purpose of the study was to investigate the influence of the carbohydrate nutrient (of various absorption rates) and the protein nutrient (containing branched amino acids) in athletes on their ability to perform an exercise test at increasing intensity to the maximum. The study was carried out on 19 subjects, before and after ten-day endurance training. The athletes were randomly divided into two groups: the supplemented group and the control group. Before the training program and after its completion, a running exercise test was performed at increasing intensity until refusal. During the exercise, the maximal oxygen intake (VO₂max) was determined with the use of the CARDIO₂ computer set. At rest and after the exercise, parameters of acid-base balance were determined in the capillary blood samples with the use of AVL-995 Hb analyzer, and the lactate level was measured by Boehringer-Mannheim test. The obtained results showed that supplementation with carbohydrate and protein nutrients improved the physical capacity and tolerance of work loads, as it was indicated by prolonged duration and distance of treadmill running, in spite of major disturbances of the acid-base balance and the lactate level in the second phase of the research.

The diet of a sportsman, like of any other human being, should relate to the common rules of rational nutrition that optimally covers and regularly supplements energetic and biologically active substances. Such a diet has to be properly composed in order to supply all energy requirements as well as all nutrients that are necessary to form cellular structures, to synthesize enzymes, hormones and other substances indispensable for the organism. On the other hand, inappropriate nutrition that is not adjusted to supply all the necessary components may cause discomfort, bad mood, health deterioration as well as decrease the ability to make physical and mental efforts.

The increased physical efforts of athletes, often performed up to the endurance limits, require additional supplementation with substances that both augment effects of training and in parallel counteract excessive loads and destruction of the organism [2, 9, 13]. Supplementary nutrients play a significant role in recreational training as well. Moreover, one must keep in mind that the means and methods of reasonable training assistance constitute an efficacious way in the struggle against pharmacological doping in sport.

Exogenous components comprised in the group of dietary supplements give evidence that contemporary sport may exist without anabolic substances [5, 12]. It has been revealed that preparations that are carefully selected with respect to training requirements and feeding program, and administered in proper combinations, at proper periods, yield similar results to those obtained by means of anabolic steroids intake. However, no negative side effects are observed in such a case.

The purpose of this study was to investigate the influence of the Carbo Pur carbohydrate nutrient (with various rates of absorption) and the High Energy protein nutrient (containing branched amino acids) on the ability to perform the exercise test with intensity increasing to the maximum in athletes.

The study was performed on 19 athletes – middle- and long-distance runners – before and ten days after endurance training (at the training camp in Szklarska Poręba). The subjects were randomized into two groups: the group supplemented with the investigated nutrients (n = 10) and the control group (n = 9). Athletes from the first group consumed 70 g of the carbohydrate supplement (Carbo Pur), 45 minutes before the training, two times per day; and the protein supplement (High Energy), 1 g (1 capsule) per 10 kg of the body mass. The Carbo Pur nutrient contained in 100 g: 1 g of dextrose, 5 g of maltose, 10 g of maltotriose and 84 g of oligosaccharides. The High Energy nutrient contained the following amino acids: tyrosine, phenylalanine, methionine, alanine, valine, leucine and isoleucine. Subjects from the control groups consumed a placebo, two times per day. During the training camp, the athletes performed endurance exercises in the morning by means of 90-120 minutes of running, and in the afternoon they participated in various sport activities: team sports, strength exercises, etc.

Before the training program and after its completion the treadmill running exercise was performed with a load increasing from 10 km/h, by 2 km/h every 3 minutes, until refusal. The maximal amount of oxygen intake (VO₂max) was determined with the use of the CARDI O₂ computer set with CPX software (Medical Graphics Corporation, USA).

At rest and immediately after the exercise test, parameters of acid-base balance and the lactate level were determined in the capillary blood samples, with the AVL-995Hb analyzer and Boehringer-Manheim test, respectively.

During the whole period of the training program, athletes were subjected to a diet composed of 14% protein, 26% fat and 60% carbohydrates of the total energy intake.

The differences between mean values of the measured parameters in two terms of the study were compared with the Wilcoxon test.

The results of the study are presented in Tables 1-5. Table 1 contains a comparison of the basic characteristics of subjects from the two groups under study: the group supplemented with nutrients, and the control group taking the placebo. The mean age of athletes in these groups amounted to 16.4 c 1.13 and 16.0 1.33 years, and the mean values of the body mass index were 20.65 1.33 and 20.57 1.83 kg/m², respectively.

Table 1. Anthropometric parameters of subjects

Tables 2 and 3 show physiological parameters as well as time of the exercise test performance and the distance covered by subjects during this test, in two phases of the study. Either in the supplemented group (Table 2), or in the control group (Table 3), time course and the distance covered by athletes increased significantly after the training camp. In the supplemented group the mean time of the exercise test was prolonged by 1.46 min, from 8.78 i 0.83 to 10.24 . 0.99 min (p<0.05), while the mean distance of the run was increased by 483 m, from 1577.11 0 359.87 to 2060.20 338.32 m (p<0.01). On the other hand, in the group taking the placebo the mean time of the exercise test was longer in the second phase of the study only by 0.78 min (increase from 8.70 f 0.95 do 9.61 1.11 min, p<0.05), and the mean distance covered by subjects was increased by 358 m (from 1621.5 ± 278.614 to 1979.6 ± 366.49, p<0.01).

Table 2. Comparison of mean values of VO₂maxand work loads between the I and II terms of investigation in the supplemented group

Table 3. Comparison of mean values of VO₂max and work loads between the I and II terms of investigation in the control group

Tables 4 and 5 present a comparison of acid-base balance parameters measured in both phases of the study, at rest and after the exercise test. It is worth noticing that in both groups of athletes disturbances of homeostasis after the physical exercise were more pronounced in the second phase of the study.

Table 4. Comparison of mean values of physiological parameters between the I and II terms of investigation in the supplemented group

Table 5. Comparison of mean values of physiological parameters between the I and II terms of investigation in the control group

The results of the present study indicate that regular training evokes profitable changes in the organism, leading to an increase of physical capacity and tolerance to exercise. This improvement is expressed as the prolongation of time of the exercise performed at intensity increasing to the maximum and the prolongation of the distance covered during this exercise. In the group supplemented with nutrients, the mean time has increased by 16% and the mean distance by 30%. In the placebo group the mean values of these parameters have improved by 10 and 20%, respectively. The parameters of acid-base balance (pH and BE, Tables 4 and 5) in the second phase of the study, after the training program, became worse in comparison to the first term. However, the time results in the group taking carbohydrate and protein supplements have been better than in the control group.

All these observations point to the fact that parallel supplementation of sportsmen’s diet with the carbohydrate nutrient (with various rates of absorption) and the protein nutrient (containing branched amino acids) leads to a considerable rise in the physical capacity, which is correlated with delayed central and peripheral fatigue [8, 9, 10]. The carbohydrate nutrient examined in this study appears to bring sufficient and long-lasting energetic support to physical exercise. Moreover, it is likely that it also causes hypercompensation of glycogen and anabolism of muscular proteins [1]. The amino acids delivered with the second investigated nutrient have anabolic and anti-catabolic properties, so this supplement may considerably contribute to the improvement of nitrogen balance. Many amino acids, most of all these with branched chains (BCAA), have capabilities to inhibit exercise catabolism due to the process called repression by the catabolite [11]. Although in this study the concentration of free amino acids in the blood serum has not been established and the nitrogen balance has not been determined before and after the training camp, the results obtained for the supplemented group appear to be superior in comparison to the control group.

Other authors [3, 5] show that in sport achievement supplementation with branched amino acids is substantial. Fahey et al. [7] have revealed that during intensive training the general pool of amino acids in the blood may be reduced by 20%, with the largest decrease of glutamate and glutamine concentrations (by 37%). One should stress that amino acid supplementation may protect from free radicals generated during intensive physical exercise as well as it may secure the body from the excessive proteolysis of systemic proteins [11]. Such an increased proteolysis, after transfer of amino acids through the blood-brain barrier, causes higher secretion of somatotropin. This hormone inhibits catabolism and augments anabolism and lipolysis, thus suppressing catabolism of systemic proteins and intensifying decay of triglycerides [4]. According to Blumstrand et al. [5], an additional intake of branched-chain amino acids evokes a 180% increase of the plasma ratio of tryptophan / other multimolecular amino acids. This effect assures constant tryptophan supply to the brain tissue and the synthesis of 5-hydroxytryptamine [6].

With reference to the essential role of the above neurotransmitter in evoking fatigue, one may establish a hypothesis that its supplementation should cause fatigue delay, and in this way improve the physical capacity. Our results are in agreement with this hypothesis, which may be explained by the role of the supplements examined in this study. This profitable effect of amino acid and protein nutrients is confirmed by the prolongation of the time course and the distance covered during the exercise test, which has been considerably higher at the end of the training camp in the supplemented group of athletes.

[1] Ambroziak, S., Tomaszewski, W., Aminokwasy (Amino acids), “Medycyna Sportowa (Sport Medicine)”, 1998, 7, pp. 24-24.

[2] Asmussen, E., Muscle fatigue, “Medicine and Science in Sports and Exercise”, 1985, 11, pp. 313-321.

[3] Bigart, A., Lavier, P., Ullmann, L., Legrand, Ch.., Douce, P., Guezennec, C., Branched-chain amino-acid supplementation during repeated skiing exercise at altitude, “International Journal of Sport Nutrition”, 1996, 6, pp. 295-306.

[4] Blumstrand, E., Celsing, F., Newsholme, E., Changes in plasma concentration of aromatic and branched-chain amino acids during sustained exercise in man and their possible role in fatigue, “Acta Physiologica Scandinavica”, 1988, 133, pp. 115-121.

[5] Blomstrand, B., Hassmen, P., Ekbom, B., Newsholme, E., Administration of branched-chain amino acid during sustained exercise – effects on performance and on plasma concentration of some amino acids, “European Journal of Applied Physiology”, 1991, 63, pp. 83-88.

[6] Davis, J., Bailey, S., Woods, J., Galiano, F., Hamilton, M., Bartoli, W., Effects of carbohydrate feeding on plasma free tryptophan and branched-chain amino acids during prolonged cycling, “European Journal of Applied Physiology”, 1992, 65, pp. 513-519.

[7] Fahey, T., Biologiczne wskaźniki przetrenowania (Biological indicators of overtraining),”Medicina Sportiva”, 1997, 1, pp. 237-251.

[8] Gibson, H., Muscular exercise and fatigue, “Sports Medicine”, 1985, 2, pp. 120-132.

[9] Ivy, J., Glycogen resynthesis after exercise: Effect of carbohydrate intake, “International Journal of Sports Medicine”, 1998, 19, pp. 142-145.

[10] Jeukendrup, A., Skuteczność różnych źródeł węglowodanów w dostarczaniu energii podczas wysiłku fizycznego (Effectiveness of various sources of carbohydrates in the energetic supply during physical exercise), “Medicina Sportiva”, 2001, 5(4), pp. 247-261.

[11] Matuszkiewicz, A., Wyczynowe uprawianie sportu przy ograniczonej podaży białka w diecie a potencjalne możliwości antyoksydacyjne organizmu (Relation between sport achievements during limited protein diet and potential antioxidative capabilities of the organism), Akademia Wychowania Fizycznego, Gdańsk, 2000.

[12] Young, S., Some effects of dietary components (amino acid, carbohydrate, folic acid) on brain serotonine synthesis, mood and behaviour, “Canadian Journal of Physiology and Pharmacology”, 1991, 69, pp. 893-903.

[13] Wagenmakers, A., Beckers, E., Brouns, F. et al., Carbohydrate supplementation, glycogen depletion, and amino acid metabolism during exercise, “American Journal of Physiology”, 1991, 260(6), pp. 883-890.