Effect of Post-Exercise Chocolate Milk Consumption on Subsequent Exercise Performance and Mood State

Abstract

A demand for nutritional supplements to enhance recovery after endurance training is increasing among athletes to maximize their performance. The present study was conducted to identify the effects of chocolate milk consumption on blood glucose level, hydration status and mood state of the athlete after aerobic exercise. Ten male students from the Faculty of Sport Science and Coaching, UPSI (23.7±.68 years) participated in two trials separated by 1 week. For each trial consumed either chocolate milk (CM) or glucose drink (GD) after a 60 minute run at 70% of VO2max (46.43±1.32 ml/kg/min). Blood glucose levels were determined 1 and 2 hours after post-exercise CM or GD ingestion. Urine samples were collected before and 2 hours after exercise to assess hydration status. The mood state of the subject was also measured using the BRUMS questionnaire. The data were analysed by using a paired sample t-test. The results show that blood glucose levels and the urine colour are not significantly different between CM and GD consumption after exercise. Consumption of CM and GD able to reduce the feelings of tiredness, fatigue and depression, and increase vigour. These findings indicate both drinks can be consumed as a post-exercise recovery drink for endurance athletes. Keyword: Chocolate Milk, Post-Exercise, Recovery, Blood Glucose, Urine Colour, Mood. Introduction Muscle recovery after physical activity is very significant, particularly in sports and rehabilitation. Muscle fatigue can be defined as a reduction in the ability to increase muscle strength or power regardless of whether the task is retained or is caused by the peripheral (Enika and Duchateau, 2008) or central nerves (Gandevia, 2001). Due to this matter, two important aspects need to be encountered to reduce fatigue and enhance recovery which are through peripheral mechanism consist of energy compound restoration, and central mechanism represented by stress-related brain chemical production. In specific, peripheral recovery depends on body glycogen storage (Jentjens & Jeukendrup, 2003) and rehydration (Shirreffs, Armstrong, & Cheuvront, 2004). Long-term International Journal of Academic Research in Business and Social Sciences Vol. 9 , No. 6, June, 2019, E-ISSN: 2222-6990 © 2019 HRMARS 453 deterioration may also be associated with muscle injury caused by exercise and muscle soreness (DOMS). In terms of recovery after endurance training, the main goal of dietary intervention is usually to promote the process of rebuilding the glycogen synthesis of the muscle and the recovery of liquids (Roy, 2008). The addition of proteins and carbohydrates has been shown to positively affect the rebuild of glycogen synthesis and the same durability performance when supplements occur immediately or after 2 hours of training. This might as well increase protein synthesis and reduce protein degradation, which will cause further stimulation of muscle tissue repair (Ivy, 2003). According to Valentine and team, chocolate milk has a good combination of protein, electrolytes and carbohydrates for post-exercise recovery (Valentine et al., 2008). Some studies have identified that skim milk and low-fat chocolate milk have the ability to help in resynthesizing glycogen, promoting increased lean muscle mass and assist in rehydration after exercise compared to drinking mineral water and commercial beverages (Hartman et al., 2007; Karp et al., 2006; Shirreffs, Watson, & Maughan, 2007). Dairy proteins found in liquid milk have been reported to help increase the synthesis of muscle protein and endurance (Ferguson-Stegall et al., 2011) and obstacle training as well as potentially effective in repairing muscle damage after exercise (Cockburn et al., 2008; Gilson et al., 2010; Pritchett et al., 2009). Studies also showed that the use of chocolate milk after exercise can improve the performance of subsequent endurance during repeated exercise (Ferguson-Stegall et al., 2011; Thomas, Morris, & Stevenson, 2009) and speed up recovery during intensive football training (Gilson et al., 2010; Spaccarotell & Andze, 2011). As important as enhancing recovery through increasing glycogen synthesis, emotion as one of the central mechanism element also will affect total recovery after exercise, and the intake of macro and micro-nutrient also has been said to have the ability to affect mood (Benton & Donohoe, 1999). Carbohydrate can relieve depression by triggers insulin production in the body, which will then regulate blood sugar in the cell for energy production, and simultaneously affects neurotransmitters such as serotonin in the brain (Rao et al., 2008). By containing carbohydrates and protein, chocolate milk can be hypothesized to be able to affect emotion after exercise. Although chocolate milk has been proved as a potential drink for post-exercise recovery, there several studies showed contradict findings. Consumption of chocolate milk showed no different than other recovery beverages on ratings of perceived exertion and it is also not significantly affect time to exhaustion (Ferguson-Stegall et al., 2011; Gilson et al., 2010; Spaccarotell & Andze, 2011). Several studies also showed that chocolate milk was not significantly affected muscle soreness, heart rate (Gilson et al., 2010), creatine kinase (Pritchett et al., 2009), lactate (Thomas et al., 2009), and glycogen content (Lunn et al., 2012). Due to these contradictions, this study has been designed to investigate the effect of chocolate milk consumption on subsequent exercise performance and mood state. International Journal of Academic Research in Business and Social Sciences Vol. 9 , No. 6, June, 2019, E-ISSN: 2222-6990 © 2019 HRMARS 454 Methodology Instrument Eligibility for participation in the study was determined through the maximum level of oxygen intake (VO2max). Hydration status was quantified by using the urine colour chart. Heart rate was monitored using Fitmate Pro (COSMED, Italy). Blood sugar levels were performed by glucometer. Each testing trials was conducted using a treadmill. Oxygen consumption and respiratory gas exchange were analysed using a Fitmate Pro (COSMED, Italy). The rating of perceived exertion (RPE) during the testing trials was quantified using the Cleveland 1-10 Scale. Brunel Mood Scale (BRUMS) translated into Malay language (Terry et al., 1999) were used to measure mood. The BRUMS is a 24-item mood scale that measures 6 identifiable affective states through a self-report inventory, with respondents rating a list of adjectives on a 5-point Likert scale. Participant In order to recruit subjects, a group meeting with the researcher and the potential research subject was scheduled. Potential subjects were informed of the purpose, nature and details, as well as any risks associated with participation in the study during a meeting. The subject inclusion criteria included: 10 male student of Sultan Idris Education University, specific for endurance athletes, age between 23 to 25 years old, body mass index between 18 to 22 in normal phrase, athlete must be in a good health status based on health history form, subjects should have VO2max between 45-50 ml/kg/ min and no injury or illness that would prevent the individual from completing any part of the study. Preliminary Testing Each subject performed an exercise test to exhaustion (treadmill running) to determine VO2max. Constant running speed was maintained while treadmill incline (starting at 0%) increased by 2% every 2 min. VO2max was defined as the oxygen consumption at which referring to the subject's heart rate, rating of perceived exertion (RPE) or the subject was unable to continue running. Running speed for exercise at 70% of VO2max for the final test was determined after athletes achieve the volitional fatigue. Experimental Protocol Participants performed an experimental protocol comprising of two treatments. These two treatments were separated by 1 week. Each treatment protocol consists of 60 minutes running on a treadmill at 70% of VO2max followed by a 2 hour recovery period during which subjects consumed 500 ml of each of the two experimental beverages. Both protocols were identical with the exception of the composition of the beverage consumed during recovery. Subjects randomly consumed either chocolate milk (CM) or glucose drink (GD). Blood glucose levels were determined before exercise to identify fasting glucose sugar followed by 1 and 2 hours after post-exercise consuming chocolate milk or glucose drink. Urine samples also were collected before exercise and 2 hours after exercise to assess hydration status. The participants also complete a BRUMS questionnaire to identify mood state after exercise and after consuming each drink. All baseline data is compared with the same parameter after finishing the treadmill exercise. International Journal of Academic Research in Business and Social Sciences Vol. 9 , No. 6, June, 2019, E-ISSN: 2222-6990 © 2019 HRMARS 455 Recovery Period Participants rested in the laboratory for a 2 hour recovery period. Within 30 minutes after ending the exercise, participants were provided with a recovery drink of either chocolate milk or glucose drink. Participants completed a BRUMS questionnaire throughout the recovery period to determine their mood responses to the drink provided. A set of 24 subscales of mood questions were presented in the form of 6 factors which is anger, confused, depressed, tired, fatigue and vigour. Participants were also asked to not taking any calories food or drink throughout the recovery process. Each question required the participant to mark their current perception on a Likert Scale comprising five responses such as not at all to very much so. Blood sample and urine test were taken at the end of the recovery process. Data Analysis BRUMS data, urine colour chart and blood glucose levels will be analyzed descriptively and inferred. For descriptive analysis, the data obtained will be reported using mean, standa