Nutrition And Sports Practice Physical Education Essay

Nutrition is an important tool in the field of sports practice; once well oriented it may reduce fatigue, which allows the athlete to train longer or recover better between the training sessions. The aim of this study was to investigate the efficacy of a carbohydrate drink (Gatorade) on the recovery heart rate and blood lactate levels. 20 healthy men were recruited as subjects. Flavoured water or Gatorade was given randomly to the subjects 20 minutes prior to exercise. The subjects were made to exercise under Bruce treadmill protocol. The peak exercise heart rate and blood pressure were recorded, when the subjects underwent passive recovery in supine lying, and the recovery heart rate was recorded. The post exercise blood sample was analyzed for blood lactate and glucose concentrations. The same subject was followed up after 48 hours for the second trial. The findings of the study indicate statistically significant differences between Gatorade and Placebo drinks (pKey words: Gatorade, Bruce treadmill protocol, recovery heart rate, blood lactate

Introduction

Nutrition is an important tool within the sports practice; once well oriented it may reduce fatigue, which allows the athlete to train longer or recover better between the training sessions [29]. Since many food nutrients provide energy and regulate the physiological process related to exercise, it is tempting to associate the dietetic changes with the improvement of athletic performance [29]. The fastest and most widely used method of gaining increased performance is through performance enhancing substances. Previous research has consistently shown that there are many exercise occasions when a sports drink provides benefits superior to water but no athletic occasion when water is superior to a properly formulated sports drink [28]. In its simplest sense, a sports drink is a drink consumed in association with sport or exercise – either in preparation for exercise, during exercise itself or as a recovery drink after exercise [31].

The amount and types of carbohydrates used in a sports drink are critical in optimizing the potential of the drink to improve performance. Research shows that a blend of simple carbohydrates (sucrose, glucose, and fructose) is most effective in stimulating rapid absorption and enhancing carbohydrate oxidation, the two important considerations whenever athletes are training and competing [28]. In the small intestine, multiple types of carbohydrates stimulate the fastest fluid absorption and help reduce the risk of gastrointestinal distress during vigorous exercise [28]. They also help sustain important cardiovascular functions [28]. One key ingredient in Gatorade that should decrease fatigue is carbohydrates. The carbohydrates in Gatorade replenish the fuel spent by the body but the essential part of this beverage is the added electrolytes. Nerve conduction for muscle stimulation as well as any other required action potential in the process of muscle contraction expend these electrolytes and require additional electrolytes to continue functioning at peak levels [32]. A study has looked at the effects of carbohydrate-electrolyte fluid on exercise performance and determined that the added nutrients provided in sports drinks reduce the onset of fatigue and keep performance levels higher [21]. Replenishing the electrolytes gives the cells more nutrients necessary to continue driving contraction through stimulation by action potentials. Previous research has confirmed that well hydrated athletes do have generally increased performance endurance over dehydrated athletes [35]. It is well documented that carbohydrate ingestion before and during exercise is effective at maintaining or improving exercise performance [15, 16, 17, 18, 19, 20]. When taken before exercise, they have an objective to prevent or delay the homeostatic disturbances which may follow the physical activity, granting a suitable plasmatic volume from the beginning of the exercise. This also promotes a small fluids reserve in the gastrointestinal lumen, which will be absorbed during the activity.

Moreover, the consumption in the pre-exercise period can optimize the glucose concentrations in the flowing blood through the supply of carbohydrates [29, 37]. Several studies involving cycling protocols have shown that carbohydrate intake enhances performance of a high intensity exercise task of approximately one hour’s duration, compared to water or an artificially sweetened placebo [2, 3, 4, 5]. In these situations muscle glycogen stores are not considered to be limiting, especially if the athlete has “fuelled up” prior to the event [18]. Instead, a number of investigators speculate that carbohydrate intake exerts a favorable effect on sensory input to the central nervous system [3, 4]. It is well documented that when used during exercise, carbohydrates can improve the performance as shown in a study [5]. An increase in exercise intensity results in a parallel increase in carbohydrate utilization by the working muscles. Carbohydrate supplementation should therefore maintain the necessary intramuscular levels of tricarboxylic acid cycle intermediates required for the increase in energy expenditure [15]. Although the bulk of evidence suggests that the benefits of ingesting carbohydrates are limited to exercise lasting more than 90 minutes, where muscle glycogen depletion is a potential cause of fatigue [7], it is common practice for athletes performing for shorter periods to ingest commercially available carbohydrate electrolyte drinks prior to exercise. The ingestion of carbohydrates within the hour prior to exercise can cause an increase in both blood glucose and insulin concentrations. This may be detrimental to homeostasis at the onset of exercise as there is a rapid fall in blood glucose as a consequence of the combined stimulatory effects of hyperinsulinaemia and increased muscle contractile activity [17]. Notwithstanding this, the metabolic alterations associated with carbohydrate ingestion in the 30-60 minutes before exercise have the potential to improve exercise performance [13, 17, 23], and on balance there appears to be no justifiable reason as to why carbohydrate consumption should be avoided within the hour before exercise [17]. The drink used in the study – Gatorade, a Pepsi Co product – has a carbohydrate concentration of 6% (60 grams per liter or about 14 grams per 8 ounces); as research has indicated, that level appears to provide the optimal amount of carbohydrates needed for palatability, rapid gastric emptying and intestinal absorption, as well as for the enhanced carbohydrate oxidation required for improved performance.

The effect of this drink in pre exercise in relation to metabolism and performance is still questioned as it is widely used as a recovery drink and not as a pre exercise drink. Therefore, this work aims to clarify the effects of the prior consumption of Gatorade drink on blood lactate, recovery heart rate and blood glucose, etc.

MATHERIALS AND METHODS

Subjects

In order to reduce any outlying variables that could skew the data, many steps were taken to ensure their validity. Twenty healthy untrained males were chosen by their general physical fitness (age 21.37 ± 0.4 years; height 176.16 ± 1.06 cm, weight 70.48 ± 1.96 kg). They were familiarized with the experimental protocol and informed about the possible risk and benefit involved with the study both verbally and in writing before obtaining written consent. Only healthy subjects without any history of pathology or orthopedic limitation were inducted in the study. Furthermore, VO2max more than or equal to 40 mL∙kg∙min-1 was determined as minimal aerobic capacity by Queen’s College Step test in order for one to be included in the study [27]. To rule out climate variables all tests were performed in the exercise physiology laboratory which remained at the same or similar temperature, humidity, and wind speed (0 mph) during every trial [32].

Testing Protocol

The study protocol was approved by the Institutional Ethics Review Board, Guru Nanak Dev University. The study constituted a double-blind controlled, randomized cross-over design. All trials were performed at the same time of day to negate diurnal variation. For 3 days prior to the first experimental trial, all subjects were required to follow their “usual” diet, and weigh and record all foods consumed. The same diet was then consumed before the second trial as well. In order to facilitate compliance, diet sheets were given to each subject; all subjects completed two experimental trials in random order separated by a minimum of 48 hours. For each trial, the subjects consumed either a carbohydrate electrolyte solution (Gatorade) or a non-carbohydrate electrolyte placebo consisting of water, 20 minutes prior to exercise. The drinks were identical in taste, colour, temperature, and texture, and they were presented in the same coloured containers for all trials [11]. Gatorade is a lime flavoured non alcoholic, non carbonated drink containing water, 30 gm of carbohydrates (dextrose), 30 gm of sugar, citric acid, sodium citrate, monopottasium phosphate, flavoring / colouring ingredients and 225 mg sodium delivering 120 kcal of energy per 500 ml servings.

The subjects were divided into two groups. Group A were given a placebo drink 20 minutes prior to the exercise bout and the subjects in group B were given Gatorade sports drink, following a 12 hour fast. Preceding the exercise protocol, resting heart rate and blood pressure were assessed and blood lactate was measured by Analox PLM 5 lactate analyzer, while glucose was assessed using a capillary blood sample taken from the fingertip. 500 ml of drink was given to the subject randomly by the assistant blinding both the subject and the investigator about the type of drink (placebo or Gatorade).

20 minutes after the ingestion, the subjects volunteered to run on a treadmill according to Bruce protocol. Both groups underwent passive recovery, blood samples were again taken to measure post exercise blood lactate and glucose levels and the heart rate was recorded at the 1st, 2nd, 3rd, 5th, and 8th minutes after exercise.

Statistical Analysis

All data are presented as the Mean ± Standard Deviation (SD). The data were analyzed for statistical significance by using the Statistical Package for Social Sciences (SPSS 16.0) software. Paired Student’s t test and one way ANOVA were used. The level of statistically significant difference was defined with respect to 95 % likelihood, i.e., p ≤ 0.05.

RESULTS

The mean values and standard deviations of post exercise blood lactate and glucose concentration values of the placebo and Gatorade trial groups show significant differences (t = 3.04, pTable 1. Descriptive statistics of the variables studied (PLC: Placebo trial, GTR: Gatorade trial, HR: Heart rate)

Groups

PLC post lactate

GTR post lactate

PLC post glucose

GTR post glucose

PLC peak HR

GTR

peak HR

Mean±SD

7.67±2.05

5.88±2.62

69.5±8.66

78.85±11.99

185.0±43.9

175.0±64.1

t value

3.04

3.52

2.85

p value

pppANOVA for Recovery Heart Rate at 3rd, 5th and 8th minutes: One way ANOVA analysis of recovery heart rate in the 3rd, 5th and 8th minutes of recovery period reveals a statistically significant difference in the heart rate (F=4.46, pTable 2. ANOVA heart rate recovery results for 3rd, 5th and 8th minutes of recovery period

3rd minutes of recovery

Sum of Squares

df

Mean Square

F

Sig.

Between Groups

1440.00

1

1440.00

4.476

0.041

Within Groups

12223.90

38

321.68

Total

13663.90

39

5th minutes of recovery

Sum of Squares

df

Mean Square

F

Sig.

Between Groups

1729.23

1

1729.23

5.609

0.023

Within Groups

11715.75

38

308.31

Total

13444.98

39

8th minutes of recovery

Sum of Squares

df

Mean Square

F

Sig.

Between Groups

912.03

1

912.03

4.351

0.044

Within Groups

7965.95

38

209.63

Total

8877.98

39

Heart Rate and Recovery Heart Rate

Maximum post exercise heart rate for Placebo and Gatorade were 185.0±43.89 bpm and 175.0±11.99 bpm, respectively. Differences were observed between Placebo group vs. Gatorade group (p0.05) and lower in the 3rd, 5th and 8th minutes of relaxation (p

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