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JEPonline
Cashew Apple Juice Supplementation Increases Endurance and Strength Performance in Cyclists
Piyapong Prasertsri1, Terdthai Tong-un2, Thapanee Roengrit3, Yupaporn Kanpetta4,5, Junichiro Yamauchi6,7, Naruemon Leelayuwat2,5
1Faculty of Allied Health Sciences, Burapha University, Chonburi, Thailand, 2Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand, 3Faculty of Science, Prince of Songkla University, Songkhla, Thailand, 4Graduate School, Khon Kaen University, Khon Kaen, Thailand, 5Exercise and Sport Sciences Development and Research Group, Khon Kaen University, Khon Kaen, Thailand, 6Graduate School of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan, 7Future Institute for Sport Sciences, Tokyo, Japan
ABSTRACT
Prasertsri P, Tong-un T, Roengrit T, Kanpetta Y, Yamauchi J, Leelayuwat N. Cashew Apple Juice Supplementation Increases Endurance and Strength Performance in Cyclists. JEPonline 2016;19(5):59-70. The purpose of this study was to investigate the effects of cashew apple juice (CAJ) supplementation on endurance and strength performance, antioxidant, and inflammation of cyclists. This study was designed as a randomized crossover study. Eight male cyclists were randomly supplemented with either 3.5 mL·kg-1 body mass placebo (PLA) or CAJ for 4 wks with a 4-wk washout period. Endurance and strength were determined before and after the supplementations. Plasma superoxide dismutase (SOD) and serum high-sensitive C-reactive protein (hsCRP) concentrations were also determined before and after the endurance performance test. Endurance (91.26 ± 6.59 vs. 63.11 ± 7.65 min; P<0.01) and strength (52.56 ± 7.62 vs. 51.52 ± 6.72 kg; P<0.05) performance after the 4-wk CAJ supplementation were significantly higher than the PLA group. Plasma SOD concentration was greater after the CAJ supplementation than the PLA group both before (8.60 ± 0.88 vs. 5.79 ± 2.77 U·mg-1 protein; P<0.05) and after (8.53 ± 1.80 vs. 5.25 ± 1.14 U·mg-1 protein; P<0.05) the endurance test. Serum hsCRP concentration was also lower after the CAJ supplementation than the PLA group both before (0.28 ± 0.15 vs. 0.42 ± 0.21 mg·L-1; P<0.05) and after (0.41 ± 0.18 vs. 0.62 ± 0.22 mg·L-1; P<0.05) the endurance test. These results show that CAJ supplementation increased endurance and strength performance. It is likely that the results are due to increased antioxidant and reduced inflammation.
Key Words: Sports Nutrition, Physical Performance, Antioxidant, Inflammation
INTRODUCTION
Athletic endurance performance is affected by increased exercise-induced free radicals (3) through mitochondrial electron transport chain pathways in active muscles (21). These free radicals result in molecular damage including lipid, protein, and DNA, leading to suppression of mitochondrial biogenesis and increased cellular damage (16). When muscle cells are damaged, the inflammation occurs in order to repair the cell by increasing C-reactive protein (CRP) in blood circulation (22). The inflammation results in muscle soreness, leading to a reduction in physical performance (14). Also, the exercise-induced free radicals contribute to the decrease in energy production in mitochondria (13), leading to the decrease in endurance capacity. Within the muscle cells, the free radicals are scavenged by antioxidants (18) of which an increase in antioxidant activity can improve muscle inflammation and soreness while contributing energy to improving endurance performance (24). The human body has natural antioxidants, such as superoxide dismutase (SOD), catalase, and glutathione peroxidase. However, during strenuous exercise, the antioxidant defense systems in the body are overwhelmed by the increase in the level of free-radical generations. Therefore, certain nutrients from diet, such as vitamin E, vitamin C, and beta-carotene, can help to augment the body’s defense systems against free-radicals (20).
Strength performance is also important for athletes. Muscle mass synthesis is stimulated by branched chain amino acids (BCAA), leading to an increase in muscle strength. Cashew apple juice (CAJ) is made from cashew apples as a by-product of cashew nut manufacturing, and is rich in vitamin C and BCAA. Recently, we demonstrated that a 4-wk CAJ supplementation routine improved fat utilization during exercise at a rate of 75% VO2 max and increased plasma vitamin C levels after the exercise in both trained and untrained subjects with a greater change in the trained subjects (23). The CAJ-induced fat utilization and antioxidant may contribute to an increase in endurance capacity in the trained individuals during the high-intensity exercise. Moreover, BCAA, which can enhance protein synthesis, can increase strength performance.
Thus, the purpose of this study was to investigate the effects of a 4-wk CAJ supplementation on male cyclists’ endurance capacity and muscle strength. We hypothesized that CAJ supplementation would improve endurance capacity and muscle strength in male cyclists.
METHODS
Subjects
Eight male cyclists aged 20 to 41 yrs of age volunteered for this study. None was smokers, alcohol drinkers, or had cardiovascular, renal, neuromuscular, orthopedic, or liver diseases, as ascertained by health questionnaires and a medical examination. The inclusion criteria was: men aged 18 to 45 yrs with a body mass index in the range of 18.5 to 23 kg·m-2, nonsmoking, moderate caffeine intake (1 to 2 cups of coffee or equivalent per day), not attempting to lose weight, trained at least 3 to 4 d·wk-1, and involved in cycling training for at least 3 yrs prior to the study. In addition, subjects were required to have stable dietary patterns throughout the study period. The exclusion criteria included: high-level sporting activities other than cycling, having an injury within three months before this study, having diabetes, being vegetarian, having abnormal eating habits such as anorexia nervosa or bulimia, or on medications that might interfere with our tests. All subjects were informed verbally and in writing about the nature of the study, including all potential risks. Written informed consent was approved by the Human Ethical Committee of Khon Kaen University (HE521041) in accordance with the 1964 Declaration of Helsinki.
Power Calculation
The sample size of this study was calculated using the WINPEPI program according to the previous report of Fenercioglu et al. (8) in that the antioxidant supplement could prevent the increase of plasma malondialdehyde (MDA) after exercise. It also reported that leucine supplementation could increase muscle strength. The decision was made to require 80% power with a significance level of 0.05. Accordingly, the proposed size was 8 subjects per group.
Study Design
The present research used a placebo (PLA)-controlled randomized crossover investigation. The researcher who prepared both supplements was different from the researcher who gave the supplements to the subjects. Subjects were not told which composition of CAJ and PLA they were given or which supplement they were on at various times.
Procedures
Preparation of CAJ and PLA
The CAJ was provided by the Srisupphaluck Orchid Co., Ltd., Phuket, Thailand. The content of the CAJ were vitamin C (3.36 mg·100 g-1), leucine (1.64 mg·100 g-1), isoleucine (3.04 mg·100 g-1), valine (0.19 mg·100 g-1), and sugar (69.8 g·100 mL-1; 40.3 g·100 mL-1 of glucose and 29.5 g·100 mL-1 of fructose, not detected for galactose), as measured by the Central Laboratory (Thailand) Co. Ltd., Thailand. The PLA was prepared with a similar color and taste with total sugar content equal to that of the CAJ. The subjects were informed that they would be provided with two sports drinks similar in appearance, but different in composition and were unaware whether they were taking the CAJ or PLA. The drinks were kept at 4 to 8 °C.
Baseline Measurements
Before starting the experiment, all subjects received medical examinations including medical history, electrocardiogram, and blood sampling for routine blood chemistry and hematology (data not shown). Anthropometric measurements (height and body mass) were also taken. Body composition was measured in the supine position using dual emission X-ray absorptiometry (DEXA). Fat distribution was measured by the ratio of waist to hip circumference. The waist circumference was measured at the end of a normal expiration and at the mid-point between the bottom rib and the superior iliac spine. Hip circumference was measured on a horizontal plane at the site of maximum extension of the buttocks.
Study Procedure
Subjects participated in two 4-wk phases of the experiment by random supplementation of 3.5 mL·kg-1·BM·d-1 of PLA or CAJ for 4 wks with a 4-wk wash out period. Supplements were prepared by a researcher who was not involved in the subsequent study. The subjects were given each supplement for 2 times (14 bottles for every 2 wk). They were instructed to drink 1 bottle a day, and were told to divide the drinking into 2 times: after breakfast and lunch. Two to three days before finishing the last prior drink, the subjects were asked to obtain the next 14 bottles at the laboratory. The first drink of PLA or CAJ was taken the day after performance test before each phase and the final drink was taken the day before the performance test after each phase. Endurance and strengthening performances with a prior maximal oxygen consumption test (VO2 max test) (23) were determined before and after the supplementations. Immediately before and after the endurance performance test, 6 mL samples of blood were collected from the antecubital vein to measure plasma SOD and serum hsCRP concentrations. To minimize variations due to the pre-exercise glycogen stores, all the subjects fasted overnight before the test. Using a 10-point scale as a measurement of gastrointestinal discomfort, the supplements were well tolerated (data not shown).
Physical Performance Test
Time to exhaustion (TTE) was used to determine the subjects’ endurance capacity. At least 1 wk after the maximal oxygen consumption test (23), the subjects fasted overnight and then performed leg cycling at a rate of 75% VO2 max until exhaustion (having maximal symptoms of dyspnea and fatigue or the inability to maintain cycling speed at least 60 rev·min-1). They were allowed to drink not more than 250 mL·h-1 of water during the test. Endurance capacity was determined from the duration (in min) of the exercise. Each subject performed the test at the same period of time. The rating of perceived exertion was determined at the end of each test.
A handgrip test was used to determine the maximum strength. This test is a practical physical test for evaluating muscle strength (26). Previous studies showed that grip strength is correlated with the general body strength (30) and performance (9). The subjects had to squeeze the handgrip dynamometer with maximal effort twice. Maximum strength was determined from the higher value.
Blood Sampling
For each blood sampling, 6 mL of blood was taken from the antecubital vein; 3 mL into EDTA tubes and 3 mL into ACD tubes, which were immediately transferred to an ice box. Blood samples in the EDTA tube were used for determining plasma SOD concentration. Blood samples in the ACD tube were used for determining serum hsCRP concentration.
Antioxidant
The residual 3 mL blood sample in the EDTA tube was centrifuged at 4 ˚C and 3,000 g for 15 min. The upper layer was transferred to a microcentrifuge tube and stored at -80 ˚C until assay. The plasma SOD concentration was measured using the SOD determination kit-WST (Sigma-Aldrich, St. Louis, MO, USA).
Inflammation
Muscle inflammation was determined using serum hsCRP concentration. The residual 3 mL blood sample in the ACD tube was centrifuged at 4 ˚C and 3,000 g for 15 min. The upper layer was transferred to a microcentrifuge tube and stored at -80 ˚C until assay. The serum was then used to analyze serum hsCRP concentration. The assay is based on the principle of particle-enhanced immunological agglutination and was measured using Roche/Hitachi cobas c 311/511 analyzer (Roche, Basel, Switzerland) according to the standard automated laboratory methods in the Clinical Laboratory at Srinagarind Hospital, Faculty of Medicine, Khon Kaen University, Thailand.
Dietary and Physical Activity Records
To verify diet stability, the subjects were instructed to record their food intake for 3 d prior to each session. Standardization of meals was done to minimize variations in pre-exercise glycogen stores. The subjects were instructed to record their normal daily diet a week before and after the supplementations. They completed food records for 3 d before the experiment (two weekdays and one weekend day), and the records were analyzed for dietary composition using Inmucal (Mahidol University, Bangkok, Thailand). They were also instructed to keep records of physical activities for three days a week before and after the supplementations (two weekdays and one weekend day), and were analyzed for energy expenditure (1).
Statistical Analyses
Data analyses were performed using SPSS statistics. All data are expressed as mean ± SD unless otherwise stated. Analysis of covariance (ANCOVA) with adjustment for baseline values paired t test was used to evaluate the differences between and within groups, respectively. If statistical probability was P<0.05, the difference was considered to be statistically significant.
RESULTS
Table 1 shows the screening anthropometry and body composition of the subjects. Table 2 shows the maximal oxygen consumption (V̇O2 max) before CAJ or PLA supplementations of the subjects. The total energy intake and energy expenditure of the subjects during CAJ or PLA supplementation are also given in Table 3. None of them were significantly different between groups. During the supplementation periods, environmental conditions were not significantly different. The ambient temperature was 25.3 ± 0.48 and 25.8 ± 0.43 °C in the PLA and CAJ periods, respectively. The relative humidity was 48.3 ± 1.71 and 50.7 ± 1.5% in the PLA and CAJ periods, respectively.
Table 1. Screening Anthropometry and Body Composition of Subjects.
Mean ± SD / Min / MaxAge (yr) / 27 ± 6.6
63.6 ± 8.3
1.7 ± 0.01
21.3 ± 2.2
74.9 ± 6.2
90.3 ± 4.9
0.83 ± 0.01
26.0 ± 5.7
16.9 ± 5.9
46.7 ± 3.1 / 23.0 / 41.0
Body Mass (kg) / 54.0 / 81.0
Height (m) / 1.7 / 1.8
BMI (kg·m-2)
Waist Circumference (cm)
Hip Circumference (cm)
W/H Ratio
Body Fat (%)
Fat Mass (kg)
Lean Body Mass (kg) / 18.7
67.5
84.5
0.75
19.1
10.3
43.6 / 25.8
87.5
100.0
0.88
36.2
29.3
51.7
Data are expressed as mean ± SD, N = 8. Min = Minimum Value, Max = Maximum Value, BMI = Body Mass Index, W/H = Waist to Hip Circumference
Table 2. Maximal Oxygen Consumption (V̇O2 max) of Subjects before the PLA and CAJ Supplementation.