We are interested in the entire Congolese sporting population of male and female sexes practicing endurance races and walkers practicing recreational sport. The athletes were part of the national middle-distance running (MDR) team and participated in the national and international competitions of the 2012-2016 and 2017-2021 Olympiad. The non-random method and the reasoned-choice technique allowed us to retain a sample of 64 subjects including 32 long-distance running (LDR) and middle-distance running (MDR) athletes and 32 walkers. The subjects were divided into two groups: an experimental group(EG) made up of 32 trained athletes, i.e. 22 boys and 10 girls practicing endurance races (MDR and LDR) with an average age of 26.16 ± 2.79 years, a height average of 1.69 ± 0.07 m, and an average weight of 57.28 ± 4.49 kg, and a BMI of 19.73 ± 1.49 kg/ and a control group (CG) consisting of 32 walkers, i.e. 22 boys and 10 girls with a average age of 27.44 ± 3.34 years, average height 1.66 ± 0.04 m, average weight of 63.13 ± 4.03 kg and BMI of 22.49 ± 1.50 kg/m².

All participants signed a written informed consent after explaining the objectives and interest of the study. The study was presented and validated by the ethics committee (LNSP-ILP/0122/04-2020), in accordance with the Helsinki recommendations.

The investigation took place within a week. The first two days were devoted to measuring the height, weight and collecting information related to the marital status of the athletes. Then we launched a questionnaire to the 32 athletes in their training places. The food survey containing various aspects related to food behavior was carried out using food survey sheets [29] which were filled out on site and collected by the interviewer.

Trained athletes and walkers practicing maintenance sports were received at the national laboratory for the blood sample which was taken in 4 days.

Blood samples in both groups (elite athlete’s vs maintenance walking club) were taken by qualified personnel from the National Public Health Laboratory. All these analyses were carried out via an automatic process of the biochemistry laboratory of the National Public Health Laboratory.

Biomarker examinations such as fasting blood glucose, serum creatinine, triglycerides, total cholesterol, HDL-Cholesterol (HDL-C), LDL-cholesterol (LDL-C), and Complete Blood Count (NFS) were carried out in trained athletes constituting the experimental group (EG) and walkers constituting the control group (CG) at the National Public Health Laboratory of the Republic of Congo, precisely at the Directorate of Medical Biology in Brazzaville.

These samples were taken in the morning on an empty stomach with the “vacutainer system” in the subjects of two groups. Blood was collected in dry sterile evacuated tubes bearing the subject’s name or number. The blood samples were centrifuged (3500 rpm, 15 minutes) and the collected sera were stored at −20˚C until the day of the analyses. These biochemical assessments should make it possible to diagnose some biochemical variations and suspect nutritional deficiencies [30].

Biological material: Human blood;

Laboratory equipment: sterile single-use needles (21G) for blood sampling; micro infusion sets for blood sampling, tourniquets, 90˚ alcohol, sterile gloves (single use); absorbent cotton; hemolysis tubes; sticking plaster; indelible ink markers; a red blood cell counter (PENTRA ES 60), racks for transporting the tubes, adjustable micropipettes from 10 to 100 µl and from 500 to 1,000,100 µl, tips for the serum and for the reagents, a centrifuge, a refrigerator; a freezer; an HP computer; an HP printer; a spectrophotometer for the analysis of biochemical data (KENZA MAX BioChemisTry); and BIOCHEMISTRY ABALYSTER RX and racks for tube transport).

The statistical exploitation for the food practice questionnaire was carried out with the student test. The statistics were performed using the Statistical Package of Social Science for Windows (SPSS) version 22 software. The results were presented as mean and percentage.

For the biochemical parameters, the statistical treatment was carried out using a student test, the comparison test with two independent samples.

For the biochemical parameters we used a student t test for independent groups in order to compare the means.

Regarding the availability of food, as well as its accessibility on the Congolese market, it is important to note that the accessibility of food on the market was difficult [36]. Similarly, our results indicate that quality foods were available but were very expensive on the market (70% of girls and 81.82% of boys) (Table 2).

These results agree with those of Bouhika et al. [36] which stipulate that the low local agro-pastoral and halieutic production, insufficient income, the absence of a culture of preservation, processing and storage of food and the seasonality of the supply of products would be associated with the unavailability of food in the Congo. It is clear that the availability of quality food, sold at reasonable prices, remains a very worrying situation in Congo. This would lead to resorting to inappropriate eating habits [37]. In the same perspective, the WHO/ FAO [38] indicates that access to healthy food is almost reserved for wealthy populations. Regarding the quantity of food served, the results show an insufficiency in 60% of girls and 54.55% of boys (Table 3).

From a quantitative point of view, to provide enough energy and ensure muscle glycogen reserves, a quantitative intake is necessary. In this perspective, the results of previous work report that feeding with a sufficient quantity of food is a necessity for man in order to obtain energy permanently, whether for movements, vital functions (breathing, circulation, digestion) but also for the functioning of the brain [39]. Indeed, it is estimated that more than 840 million people around the world are chronically hungry, despite record per capita food availability in most countries and globally as indicated by the WHO [40].

In our study, the deficit in food quantity could be explained by the fact that these athletes lived in the households of the parents (70% of the girls and 18.82% of the boys) without being supported by the federation. These parents certainly had unfavorable socioeconomic conditions [36] [41]. This seems to agree with what Folaranni reported [42]. Indeed, this author reported that while living under the parental roof, the consumption of the quality and quantity of food was linked to the monthly income of the parents or the head of the household.

Thus, 60% of female athletes and 63.6% of male athletes reported consuming the main course. In addition, 20% of girls and 27.27% of boys had eaten the main course plus dessert. However, very few subjects had been able to consume a starter dish, a main course accompanied by dessert respectively (10% of girls and 9.09% of boys). This was probably due to the fact that these athletes came from families with a somewhat high socio-economic level (Table 4). However, according to Fréderic Maton [43], a balanced diet must be sufficient from an energy point of view, as diversified as possible. But also guarantee a good distribution between proteins, lipids, carbohydrates and a good complementary supply of vitamins, minerals and fibers. The main food was corn porridge with donuts, rice pudding with donuts, spaghetti and CAO (legumes) plus buttered bread and a cup of milk plus peanut paste bread in breakfast and salted fish, beans, foufou, gnetum, peanut paste, palm nuts, eggplants, cassava, game meat, vegetables, pork, rice, chicken wing, chicken thigh, sorrel, smoked fish, pigeon peas, saka-saka and pork tail for lunch, and had consumed more smoked fish, gnetum, foufou, bread, spaghetti, cup of milk, bread with butter, meat from pork, beans, rice, turkey wing and cassava for dinner. This way of eating is inappropriate and does not cover the athlete’s energy needs. However, a substantial nutritional intake provides the energy to run the body. A bit like a heat engine, the muscles transform a large part of the energy consumed into heat. To regulate the resulting water losses, water inputs must therefore be taken into account with the same care as energy inputs; this, both to prevent dehydration accidents and to maintain an optimum level of performance.

Regarding biochemical parameters, it should be noted that physical exercise plays a very important role in their regulation. Indeed, physical exercise under the effect of neurobiochemical substances such as norepinephrine and adrenaline, increases glycemia in athletes by inducing hyperglycemia and hyperinsulinemia. One would expect that high blood sugar would not be seen frequently in athletes and low blood sugar would be more of a concern due to increased energy expenditure. Our results do not reveal any significant differences between the groups of subjects on the one hand (0.81 ± 0.08 vs 0.82 ± 0.20; t = −0.29; p > 0.05) (Table 5) and the sexes of the subjects on the other hand (Sum of the squares = 0.05; dof = 3; F = 0.72; p > 0.05). The reference value being 0.70 g/l to 1.10 g/l in the mixed subjects, their results were within the norms (Table 5). The study conducted by Thomas et al. [44] had shown that the only athlete who had worked out with a blood sugar level below 4.0 mmol/L, had a calorie intake considerably reduced compared to the recommended intakes.

In the field of sports medicine, serum creatinine is generally used to assess the health status of athletes, particularly in activities where hydroelectric balance is crucial. Serum creatinine is not influenced by training and competition, although a 20% increase has been reported during endurance and ultra-endurance activities [45]. It is a very stable variable in the athlete, but its concentration can vary on the one hand between the athlete and the sedentary and on the other hand between the types of activities. The reference value being 0.7 mg/dl to 1.36 mg/dl in mixed subjects, our results reveal that EG subjects had a significantly lower serum creatinine concentration compared to CG subjects (0.86 ± 0.06 mg/dl vs 1.04 ± 0.16 mg/dl; t = -5.95; p < 0.000) (Table 5). Our results are in agreement with the work of Lippi et al. (2004) and Lippi et al. (2006) [46] [47] who obtained significantly low concentrations in skiers and cyclists compared to sedentary subjects.

In the same athletes, the concentration of serum creatinine can vary according to the different stages of competition in a sports season. However, lean mass is not a good index to assess this concentration. According to Banfi and Del Fabbro (2006] [48], cyclists, characterized by a very low percentage of fat mass, had a very low serum creatinine concentration compared to rugby players who had a very high fat mass.

Our results on the comparison of biochemical parameters according to sex show that the parameters of the subjects differ significantly concerning serum creatinine (F(3.60) = 11.57; p < 0.000), total cholesterol (F(3.60) = 5.70; p < 0.000), HDL Cholesterol (F(3.60) = 19.71; p < 0.000), LDL cholesterol (F(3.60) = 6.09; p < 0.000), the LDL/HDL ratio (F(3.60) = 16.89; p < 0.000) and the total cholesterol/HDL ratio (F(3.60) = 23.44; p < 0.000). This means that the means of these five parameters differ significantly according to sex. The use of the Post Hoc LSD (or two-by-two means test) for the multiple comparison then makes it possible to detect these differences (Table 6). Similarly, our results show that CG subjects, with a significantly elevated BMI, had significantly elevated serum creatinine concentrations compared to boys (0.87 ± 0.07 mg/dl vs 1.05 ± 0.19 mg/dl; p < 0.000) and girls (0.84 ± 0.06 mg/dl vs 1.04 ± 0.07 mg/dl; p < 0.01) of the EG (Table 7). This could be related to the lack of intensive physical activity in their maintenance program. Today, it is proven that physical activity leads to biochemical changes [23]. Triglyceride (TG) metabolism in adipose tissue and its regulation have been studied in detail for many years. It has been shown that muscle TGs are consumed during submaximal exercise as an important substrate for contracting muscle and that, this intramuscular contribution is 7%, 26% and 8% during exercise performed at 25%, 65% and 85% of VO2max respectively [49].

According to numerous studies, regular participation in endurance exercise and training is associated with lower concentrations of blood TGs [50]. Our results reveal that, compared to CG, the amount of TG in EG subjects is slightly low (0.91 ± 0.32 g/l vs 1.04 ± 0.41 g/l; t = −1.97; p > 0.05) (Table 5). These results are similar to those reported by Rahanama et al. [51] who state that highly trained athletes seem to use more of their intracellular TG stores. So this decrease in TG observed in our subjects of the EG is justified by the fact that the intensity of the activity had caused a consumption of intramuscular TG. This intensity of activity was higher between boys in EG and girls in CG. This is justified by a significant drop in TG in these boys (0.87 ± 0.32 g/l vs 1.21 ± 0.51 g/l; p < 0.01) (Table 7).

Results of previous work had demonstrated a clear relationship between levels of cardiovascular disease (CVD) and total cholesterol (TC) [52] [53]. According to the study by Kelley et al. [54], aerobic exercise reduced TC and TG levels in men over 18 years of age. The reference values being 1.40 g/l to 2.70 g/l in mixed subjects, our results indicate that, compared to CG, the Total cholesterol(TC) of EG subjects is significantly low (1.66 ± 0.34 g/l vs 2.09 ± 0.50 g/l; t = −3.99; p < 0.000) (Table 5). This high intensity had also induced a decrease in TC in girls and boys in the EG compared to girls and boys in the CG (2.07 ± 0.48 g/l vs 1.72 ± 0.38 g/l; p < 0.01) in boys and 2.11 ± 0.57 g/l vs 1.53 ± 0.21 g/l; p < 0.01 in girls) (Table 7). Like TC, LDL/HDL, TC/HDL, LDL-Cholesterol (LDL-C) is a major predictor of coronary heart disease. An increase in their levels has been shown to lead to an increase in the formation of atherosclerotic plaques [55]. Indeed, it is generally accepted that the values of TC, LDL/HDL ratio, TC/HDL ratio, and LDL-C are high in sedentary subjects compared to trained subjects. Our results show that, compared to EG, the CG presents LDL-C results and LDL/HDL and CT/HDL ratios, which are significantly elevated respectively (1.27 ± 0.48 g/l vs 0.87 ± 0.33 g/l; t = −3.85; p < 0.000; 2.96 ± 1.45 g/l vs 1.08 ± 0.56 g/l; t = −6.82; p < 0.000 and 4.73 ± 1.71 g/l vs 2.06 ± 0.89 g/l; t = −7.82; p < 0.000) (Table 5). The increase in LDL-C values was observed in both CG and EG boys, but showed no significant differences. However, compared to EG boys, CG boys have significantly elevated LDL-C, LDL/HDL and CT/HDL values, respectively (0.95 ± 0.37 g/l vs 1.31 ± 0.43 g/l; p < 0.01; 0.94 ± 0.49 g/l vs 3.14 ± 1.32 g/l; p < 0.000 and 1.71 ± 0.72 g/l vs 4.84 ± 1.42 g/l; p < 0.000). Similarly, compared to the girls in the EG, the girls in the CG showed significantly elevated C-LDL, LDL/ HDL and CT/HDL values (0.71 ± 0.14 g/l vs 1.17 ± 0.59 g/l; p < 0.01; 1.39 ± 0.62 g/l vs 2.55 ± 1.70 g/l; p < 0.05 and 2.84 ± 0.76 g/l vs 4, 48 ± 2.28 g/l; p < 0.01) (Table 7). Indeed, biomarkers are associated with a diagnostic value to identify a physiopathological process or a disease (acute coronary syndrome or acute pulmonary edema for example) or prognostic value, in the short or medium term, to evaluate the effectiveness of the therapies undertaken or to allow the orientation of the patient in the structure of care most adapted to his condition. In our study, we checked Blood Glucose, Creatinemia, Triglycerides, Total Cholesterol, HDL-Cholesterol, LDL-Cholesterol, LDL/HDL and CT/HDL ratio to determine the health status of athletes.

Physical training (endurance and strength) is generally associated with the elimination of risk factors for cardiovascular disease by improving the lipid profile. Results obtained from previous studies have shown that endurance training causes effective changes in the lipid profile. Indeed, endurance training increases the body’s potential to mobilize and oxidize fatty acids. This adaptation may also influence the plasma concentration of lipids and lipoproteins [56]. According to Mazloom et al. [57], well-trained men have a lower level of total Tg, VLDL, LDL and a high level of HDL.

These results are similar to those found in our study. Indeed, compared to the CG subjects, the EG subjects had significantly elevated HDL concentrations (0.98 ± 0.49 g/l vs 0.48 ± 0.18 g/l; t = 5.34; p < 0.000) (Table 5). Looking at the HDL according to the sexes of the subjects, it appears that, compared to the boys of the CG and the girls of the experimental and control groups, the boys of the EG presented significantly elevated HDL concentrations respectively (1.15 ± 0.48 g/l vs 0.45 ± 0.13 g/l; p < 0.000; 1.15 ± 0.48 g/l vs 0.59 ± 0.23 g/l; p < 0.000 and 1.15 ± 0.48 g/l vs. 0.56 ± 0.26 g/l; p < 0.000) (Table 7). These results agree with those found by Mirghani et al. [58] and Thaveeratitham et al. [59]. Indeed, these authors had proven that low levels of TC and LDL-C as well as a high concentration of HDL-C lead to a lower risk of CVD. This is due on the one hand to the fact that exercise leads to an increase in the activity of enzymes in adipose tissue and in skeletal muscle. On the other hand, because the levels of HDL-C exhibit antioxidant properties and prevent the accumulation of LDL-C in the walls of the veins. However, compared to CG girls, the HDL-C concentrations found in EG girls show a high trend, but do not show significant differences (0.59 ± 0.23 vs 0.56 ± 0.26; p > 0.05). These results are probably justified by the regular participation in endurance activities and that the girls in the CG were probably more active than the boys (0.45 ± 0.13 vs 0.56 ± 0.26; p > 0.05) (Table 7). Although the link between physical activity and cardiovascular health has not been verified in our study, it is recognized that regular physical activity and exercise induce a myriad of physiological adaptations that directly or indirectly benefit the human cardiovascular health. Many of these benefits appear to be seen in traditional CVD risk factors, such as blood lipid and glucose levels, obesity and high blood pressure. Regular exercise induces antiatherogenic adaptations in vascular structure and function, independent of traditional cardiovascular disease risk factors. It improves cardiac parasympathetic regulation, thereby conferring protection against malignant arrhythmias, and it also provides protection to the heart against ischemia-reperfusion damage. Myokines produced and released by muscles are responsible for many of the beneficial effects of exercise, including supporting a healthy anti-inflammatory milieu.

Random errors are limited by the small size of the sample, but the unique realization of the questionnaire does not escape the variability of the parameters studied. The non-sampling of athletes’ blood after the African Games competition period for the purpose of comparing biochemical data between the two periods was a limiting aspect of our research.