Fernanda Lorenzi Lazarim

Vitamin C and E Supplementation Effects in Professional Soccer Players Under Regular Training

Exercise training is known to induce an increase in free radical production potentially leading to enhanced muscle injury. Vitamins C and E are well known antioxidants that may prevent muscle cell damage. The purpose of this study was to determine the effects of these supplemental antioxidant vitamins on markers of oxidative stress, muscle damage and performance of elite soccer players. Ten male young soccer players were divided into two groups. Supplementation group (n = 5) received vitamins C and E supplementation daily during the pre-competitive season (S group), while the placebo group (PL group, n = 5) received a pill containing maltodextrin. Both groups performed the same training load during the three-month pre-season training period. Erythrocyte antioxidant enzymes glutathione reductase, catalase and plasma carbonyl derivatives did not show any significant variation among the experimental groups. Similarly, fitness level markers did not differ among the experimental groups. However, S group demonstrated lower lipid peroxidation and muscle damage levels (p < 0.05) compared to PL group at the final phase of pre-competitive season. In conclusion, our data demonstrated that vitamin C and E supplementation in soccer players may reduce lipid peroxidation and muscle damage during high intensity efforts, but did not enhance performance.

Is lactate production related to muscular fatigue? A pedagogical proposition using empirical facts

The cause-effect relationship between lactic acid, acidosis, and muscle fatigue has been established in the literature. However, current experiments contradict this premise. Here, we describe an experiment developed by first-year university students planned to answer the following questions: 1) Which metabolic pathways of energy metabolism are responsible for meeting the high ATP demand during high-intensity intermittent exercise? 2) Which metabolic pathways are active during the pause, and how do they influence phosphocreatine synthesis? and 3) Is lactate production related to muscular fatigue? Along with these questions, students received a list of materials available for the experiment. In the classroom, they proposed two protocols of eight 30-m sprints at maximum speed, one protocol with pauses of 120 s and the other protocol with pauses of 20 s between sprints. Their performances were analyzed through the velocity registered by photocells. Blood lactate was analyzed before the first sprint and after the eighth sprint. Blood uric acid was analyzed before exercise and 15 and 60 min after exercises. When discussing the data, students concluded that phosphocreatine restoration is time dependent, and this fact influenced the steady level of performance in the protocol with pauses of 120 s compared with the performance decrease noted in the protocol with pauses of 20 s. As the blood lactate levels showed similar absolute increases after both exercises, the students concluded that lactate production is not related to the performance decrement. This activity allows students to integrate the understanding of muscular energy pathways and to reconsider a controversial concept with facts that challenge the universality of the hypothesis relating lactate production to muscular fatigue.

Glycemic Control and Muscle Damage in 3 Athletes With Type 1 Diabetes During a Successful Performance in a Relay Ultramarathon: A Case Report

Ultramarathon races are fairly demanding and impose substantial physiological stress on healthy athletes. These competitions may thus be considerably more challenging for individuals with diabetes. This case study aims to describe glycemic control, muscle damage, inflammation, and renal function in 3 athletes with type 1 diabetes during a successful performance in a relay ultramarathon. The team completed the race in 29 hours and 28 minutes, earning third place. The total distance covered by each athlete was 68.7, 84.5, and 65.1 km. Most blood glucose levels showed that athletes were in a zone where it was safe to exercise (90-250 mg/dL or 5.0-13.9 mmol/L). Creatine kinase, lactate dehydrogenase, and aspartate aminotransferase serum levels increased 1.2- to 50.7-fold prerace to postrace, and were higher than the reference ranges for all the athletes postrace. Blood leukocytes, neutrophils, and serum C-reactive protein (CRP) increased 1.6- to 52-fold prerace to postrace and were higher than the reference ranges for 2 athletes after the race. Serum creatinine increased 1.2-fold prerace to postrace for all the athletes but did not meet the risk criteria for acute kidney injury. In conclusion, our main findings show evidence of satisfactory glycemic control in athletes with type 1 diabetes during a relay ultramarathon. Moreover, elevation of muscle damage and inflammatory biomarkers occurred without affecting renal function and challenging the maintenance of blood glucose among athletes. These findings are novel and provide an initial understanding of the physiological responses in athletes with type 1 diabetes during ultramarathon races.

Applicability of the Reference Interval and Reference Change Value of Hematological and Biochemical Biomarkers to Sport Science

The training principle states that tissue adaptation depends upon overload applications. The cumulative effect of these programmed breaks in homeostasis through variations in the intensity, duration and frequency of the exercise is higher performance. However, it is important to point out that the positive adaptive response, which is reflected by increased performance, depends upon an adequate recovery time between each training session and during training sessions to result in phenotypic alterations (Hohl et al., 2009). Training sessions and nutrition are highly interrelated. Repeated training sessions typically require a diet that can sustain muscle energy stores to execute the training proposed. The phenotypic alterations that lead to increased performance result from an intense process of protein synthesis that occurs during the recovery period and can last up to 24 h after the exercise session. This process is highly influenced by food ingestion, which offers energy and nutrients that are essential to the process and to the recovery of energy reserves (Hawley et al., 2006). Recent evidence shows that some nutrients can potentiate the protein synthesis pathways that are activated by exercise, influencing the adaptive process and performance (Hawley et al., 2011). Professional athletes, for example, soccer players, are submitted to an annual training and competition routine with periods of recovery that are not always properly adjusted to the workload. The main problem is that the current championship schedule generally does not allow the teams to take the minimum time required for appropriate physical preparation because the different stages (competitions and physical, technical and tactical training) overlap. As a consequence, the athletes may suffer an imbalance between the effort put forth and the recovery time during the competitive season, which increases the likelihood that the workload will be excessive for some players. Each overload stress results in different degrees of microtrauma in the muscle, connective tissue, and/or bones and joints, which trigger an inflammatory response promoting repair

Mountain Ultramarathon Induces Early Increases of Muscle Damage, Inflammation, and Risk for Acute Renal Injury

Purpose: This study aimed to investigate changes in muscle damage during the course of a 217-km mountain ultramarathon (MUM). In an integrative perspective, inflammatory response and renal function were also studied. Methods: Six male ultra-runners were tested four times: pre-race, at 84 km, at 177 km, and immediately after the race. Blood samples were analyzed for serum muscle enzymes, acute-phase protein, cortisol, and renal function biomarkers. Results: Serum creatine kinase (CK), lactate dehydrogenase (LDH), and aspartate aminotransferase (AST) increased significantly throughout the race (P < 0.001, P < 0.001; P = 0.002, respectively), and effect size (ES) denoted a large magnitude of muscle damage. These enzymes increased from pre-race (132 ± 18, 371 ± 66, and 28 ± 3 U/L, respectively) to 84 km (30, 1.8, and 3.9-fold, respectively); further increased from 84 to 177 km (4.6, 2.9, and 6.1-fold, respectively), followed by a stable phase until the finish line. Regarding the inflammatory response, significant differences were found for C-reactive protein (CRP) (P < 0.001) and cortisol (P < 0.001). CRP increased from pre-race (0.9 ± 0.3 mg/L) to 177 km (243-fold), cortisol increased from pre-race (257 ± 30 mmol/L) to the 84 km (2.9-fold), and both remained augmented until the finish line. Significant changes were observed for creatinine (P = 0.03), urea (P = 0.001), and glomerular filtration rate (GFR) (P < 0.001), and ES confirmed a moderate magnitude of changes in renal function biomarkers. Creatinine and urea increased, and GFR decreased from pre-race (1.00 ± 0.03 mg/dL, 33 ± 6 mg/dL, and 89 ± 5 ml/min/1.73 m2, respectively) to 84 km (1.3, 3.5, and 0.7-fold, respectively), followed by a plateau phase until the finish line. Conclusion: This study shows evidence that muscle damage biomarkers presented early peak levels and they were followed by a plateau phase during the last segment of a 217-km MUM. The acute-phase response had a similar change of muscle damage. In addition, our data showed that our volunteers meet the risk criteria for acute kidney injury from 84 km until they finished the race, without demonstrating any clinical symptomatology.

Understanding the glycemic index and glycemic load and their practical applications.

We have introduced the study of synthesis pathways using two experiments: 1—the determination of the glycemic index (GI) of some foods and the effects of fiber and fat on the GI; 2—the determination of blood glucose levels after the ingestion of meals with high and low glycemic loads (GL). After a practice assembly, when the foods and meals that were eaten by the students were tallied, the students were divided into groups. At the next class, three members of each group, who had fasted for 8 hr, ingested 50 g of carbohydrate in food or a meal. After ingestion, the blood glucose was measured with a portable device every 30 min for a period of 2 hr. Discussion of the data obtained in experiment 1 allowed the students to understand the mechanism of action of insulin and to understand how the GI, as presented in the literature, is determined. The students also concluded that the addition of fiber to food reduces the glycemic response even with high GI foods, and these results could be a useful strategy for diet prescription. Discussion of experiment 2 allowed the students to understand that the amount of food intake is a determining factor for the glycemic response and subsequent release of insulin. These experimental observations allowed the students to transfer theoretical knowledge to their daily lives very easily. The students approved the classes and felt encouraged to study the synthesis pathways and metabolic integration in the fed state.

Lactate production retards, not causes, acidosis: a theoretical approach for physical education students.

The content of numerous textbooks of exercise physiology, biochemistry and even many papers in the current literature explain acidosis during intense exercise by the production of lactic acid, causing the release of a proton with lactate as the final product. However, lactate production retards not cause acidosis. To understand better the importance of training schedules features and to do a correct interpretation of blood lactate measurements during different kinds of exercise, the goal of this work is to present a practical approach carried out with physical education students that allows the discussion of these concepts with real datas, breaking the myth involving this subject. Firstly, the students were conduct to plan different exercise protocols (continuous versus intermittent) where the average speed and blood lactate were measured. After the exercise protocols done, the students did some correlation among blood lactate, fatigue index and performance datas. The results show that there is not a clear relationship between blood lactate and fatigue, independently of exercise type that is being considered. By this way, it is possible to build with the students a new view of this polemic subject (blood lactate and fatigue) through a simple practical approach, helping the students to understand better metabolic aspects involved with physical exercises.