Serum concentration of cobalt, molybdenum and zinc in aerobic, anaerobic and aerobic-anaerobic sportsmen

The possible ergogenic role of minerals in human performance has been studied [19] as well as the effects of physical exercise on its body concentrations. In this research, it can be observed important differences in anthropometric variables as well as serum concentrations of essential trace metals between sportsmen and control (no sportsmen) participants. This data reinforces the differences found by Maynar et al. [10] and Maynar et al. [9] in their surveys, with similar subjects and in different elements.

As indicated in Tables 1 and 2, there were important anthropometric and fitness differences between groups. These tables show, as indicated by the total weight, the sum of the skinfolds, the maximum oxygen consumption and the resting heart rate, a clear adaptive response to exercise among sportsmen as consequence of long term, continuous training. If athletes are separated by metabolic specialties, those differences are maintained, being specific to the type of training that was followed in each specialty. In all cases the differences are clear, and this fact leads us to think that the exercise-induced effects could also affect the values of the minerals studied. This idea is based on the roles of these elements in the physiological processes linked to exercise, like the adaptations in the antioxidant enzymes [20].

An important fact in the metabolic behaviour of these elements, as well as its effect on physical performance and health, is the nutritional intake [21]. Despite similar nutritional intake of minerals, it can be observed significant differences in serum concentrations of essential trace metals between sportsmen and sedentary people. However, in all cases the mineral seric concentrations were within reference values of untrained, healthy participants, being the values, in μg/L, of each element: Co 0,21–7; Mo 0,5–2; Zn 700–1600 [22].

Thus, in relation to the Co, the values were similar among athletes of the different modalities as well as among CG participants. These results are in accordance with the obtained by Bergeret al. [23] in marathon runners.

In relation to Mo, data obtained in the present research could indicate a higher production of free radicals by exercise-induced ischemia-reperfusion in the muscles. This physiological phenomenon can be induced by high intensity muscle contractions [24], a typical situation among anaerobic physical efforts and, with minor magnitude, by long-duration aerobic exercise, this hypothesis is reinforced by the obtained data, being higher the Mo values among all sportsmen (of all modalities) than among CG.

Mo participates in oxide-reduction processes as an integral part of several enzymes like xanthine dehydrogenase, an enzyme which catalyzes the hypoxanthine transformation of xanthine to uric acid [4] which is considered an antioxidant substance. This biochemical process is augmented in sportsmen metabolism, especially among anaerobic exercises. In this survey the ANEG sportsmen presented the highest concentrations of seric Mo, followed by AE-ANEG participants and, finally, by AEG (p < 0.001). As it has been previously indicated, these differences in Mo values could be linked to a higher production of free radicals by ischemia-reperfusion in the SPG. Bergeret al [23], found similar results among marathon runners, but, in their case, without the reference of a control group. Augmented Mo concentrations would ease the formation of uric acid as well as decrease the damage caused by superoxide anions generated by xanthine oxidase in the ischemia-reperfusion processes, situation induced by high intensity muscular activities [24].

In this study, similar Zn concentrations were found in CG and SPG (Table 5). However, when athletes were divided according to the type of activity performed differences can be found between sportsmen and CG participants.

Zn is part of more than 300 enzymes involved in various functions of cellular metabolism, including metabolism of lipids, proteins and carbohydrates [25]. It is distributed in all organs, fluids and secretions of the human body.

In the study of the effect of physical training in plasma values of Zn, Rodríguez-Tuya et al. [26] found, as in the present survey, that plasma Zn concentrations were significant higher in anaerobic sportsmen than in control group. However, Rodríguez-Tuya et al. [26] found that aerobic group plasma Zn concentrations were significant higher than control group values whereas in the present research AEG serum Zn concentrations are lower than CG values.

As in the present survey, Michelettiet al. [27] detected the same situation among Italian athletes. They indicated that nutritional habits of elite athletes during training and competition are quite different from the standard diets of the majority of the population.

Endurance athletes often adopt an unusual diet in an attempt to enhance performance: an excessive increase of carbohydrates in their diets and a low intake of proteins and fat may lead to suboptimal Zn intake. The finding of De Carvalhoet al. [28] reinforces this idea, due to they found Zn deficiencies in serum of elite swimmers.

The low serum concentrations among AEG participants, may be due to an exercise-induced body Zn redistribution between body stores, bloodstream and tissues. Furthermore, the increased metabolism may lead to a deficiency of Zn, requiring supplementation in order to maintain normal values and high level performance [29, 30]. Furthermore, Andrade and Marreiro [31] found that during physical exercise, Zn compartmentalization may be impaired, which means that changes in the concentrations of this element may occur in different organic compartments, and this may reflect differences in blood values. However, the mechanisms involved in the metabolism of Zn, as well as its effects in the improvement of physical performance, are not fully understood yet. In all cases, decreases in Zn concentrations can lead to a reduction in the activity of a fundamental enzyme among endurance athletes, carbonic anhydrase [32] as well as to a decrease in the antioxidant defense system and, consequently, to an increase in oxidative stress in sportsmen cells [33]. For all these reasons, and as Karaet al. [34] indicated, Zn supplementation among athletes may beneficially contribute to their health and performance. However, it is striking that Zn concentrations were significantly (p < 0.001) higher in AE-ANEG and in ANEG (p < 0.05) than in CG and very significantly (p < 0.001) higher than in AEG. These data would be in relation with the data of found by Granell [35]. This suggest that changes of seric Zn can be linked to the type of exercise performed, being the higher values in cases of intense impacts in muscular tissues.