The present study set to examine the effects of different doses of caffeine on performance, rating of perceived exertion (RPE), and pain perception in female teenager athletes of karate. Ten female karate athletes (16.8±1.23 years; height 1.59±0.28 m; body-mass 57.73±8.33 kg; BMI 22.71±3.05 kg/m 2 ) participated in the study. A double-blind, randomized, and crossover counterbalanced design was used. In three sessions (with an interval of seven days'), ten female karate athletes ingested low dose (2 mg/ kg), moderate dose (5 mg/kg) caffeine, and placebo. Sixty minutes after consumption, they performed the tests as below: one repetition maximum and 60% of one repetition maximum in the leg press, explosive power test, and anaerobic RAST test. After the tests, the participants' RPE (6-20 scale) and pain perception (0-10 scale) were recorded using various categorical scales. The results showed that caffeine ingestion at moderate dose significantly reduced RPE and pain perception values compared with the placebo during muscular endurance test (P=0.0001 and P=0.039, respectively). The findings suggest that caffeine dose of 5 mg/kg body mass appears to improve RPE and pain perception in female teenager athletes of karate. The dose of 2 mg/kg body mass does not confer any additional improvement in performance.Uniterms: Caffeine/effects. Karate athletes/performance. Caffeine/rating of perceived exertion. Caffeine/ performance. Caffeine/pain perception. INTRODUCTIONCaffeine (1,3,7-trimethylxanthine) is a plant alkaloid that occurs naturally in the diet (Sökmen et al., 2008) and nearly 90% of US adults consume caffeine in forms of coffee, tea, or other caffeinated food products (8 cup of coffee may contain 50-200 mg caffeine) (Owens, 2015;Yang, Palmer, De Wit, 2010). In the U.S.A., adults ingest an average of 3 mg/kg of caffeine daily in coffee, tea, caffeinated sodas, and many other drinks and food (Sökmen et al., 2008). The popularity of caffeine as an ergogenic aide has increased dramatically over the last decade (Hendrix et al., 2010), Caffeine is the most widely consumed to improve cognitive, physical performance during exercise and has become a popular ergogenic aid among recreational and competitive athletes (Hendrix et al., 2010;Sökmen et al., 2008;Zheng et al., 2014).Caffeine is classified as part of the methylxanthine family of drugs (Cechella et al., 2014;Mohr, Nielsen, Bangsbo, 2011) and is extensively consumed by athletes as an ergogenic aid (Backhouse et al., 2011;Mohr, Nielsen, Bangsbo, 2011) since its removal from the World AntiDoping Agency (WADA) prohibited list of substances (Backhouse et al., 2011;Mohr, Nielsen, Bangsbo, 2011). According to the Medical Council of International Olympic Committee (IOC), caffeine is allowed in sports as long as its urinary excretion level is below 12 µg/mL (Bell, Jacobs, Ellerington, 2001).Taken orally, caffeine reaches a peak plasma concentration of 30-90 min after ingestion, and a halflife has been reported to be 3 to 5 hours with a modest intake of coffee (Sökmen et al.,...

Oxidative stress is the result of an imbalance between the generation of reactive oxygen species (ROS) and their elimination by antioxidant mechanisms. ROS degrade biogenic substances such as deoxyribonucleic acid, lipids, and proteins, which in turn may lead to oxidative tissue damage. One of the physiological conditions currently associated with enhanced oxidative stress is exercise. Although a period of intense training may cause oxidative damage to muscle fibers, regular exercise helps increase the cells’ ability to reduce the ROS over-accumulation. Regular moderate-intensity exercise has been shown to increase antioxidant defense. Endogenous antioxidants cannot completely prevent oxidative damage under the physiological and pathological conditions (intense exercise and exercise at altitude). These conditions may disturb the endogenous antioxidant balance and increase oxidative stress. In this case, the use of antioxidant supplements such as creatine can have positive effects on the antioxidant system. Creatine is made up of two essential amino acids, arginine and methionine, and one non-essential amino acid, glycine. The exact action mechanism of creatine as an antioxidant is not known. However, it has been shown to increase the activity of antioxidant enzymes and the capability to eliminate ROS and reactive nitrogen species (RNS). It seems that the antioxidant effects of creatine may be due to various mechanisms such as its indirect (i.e., increased or normalized cell energy status) and direct (i.e., maintaining mitochondrial integrity) mechanisms. Creatine supplement consumption may have a synergistic effect with training, but the intensity and duration of training can play an important role in the antioxidant activity. In this study, the researchers attempted to review the literature on the effects of creatine supplementation and physical exercise on oxidative stress.

No abstract

Athletes often seek to use dietary supplements to increase performance during exercise. Among various supplements, much attention has been paid to beetroot in recent years. Beetroot is a source of carbohydrates, fiber, protein, minerals, and vitamins; also, it is a natural source of nitrate and associated with improved sports performance. Nitrates can the modification of skeletal muscle contractile proteins or calcium handling after translation. The time to reach the peak plasma nitrate is between 1 and 3 h after consumption of a single dose of nitrate. Nitrate is metabolized by conversion to nitrite and subsequently nitric oxide. Beetroot can have various effects on athletic performance through nitric oxide. Nitric oxide is an intracellular and extracellular messenger for regulating certain cellular functions and causes vasodilation of blood vessels and increases blood flow. Nitric oxide seems to be effective in improving athletic performance by increasing oxygen, glucose, and other nutrients for better muscle fueling. Nitric oxide plays the main role in anabolic hormones, modulates the release of several neurotransmitters and the major mediators of stress involved in the acute hypothalamic-pituitary-adrenal response to exercise. Beetroot is an important source of compounds such as ascorbic acid, carotenoids, phenolic acids, flavonoids, betaline, and highly active phenolics and has high antioxidant properties. Beetroot supplement provides an important source of dietary polyphenols and due to the many health benefits. Phytochemicals of Beetroot through signaling pathways inhibit inflammatory diseases. In this study, the mechanisms responsible for these effects were examined and the research in this regard was reviewed.

BackgroundOsteoporosis is a skeletal metabolic disorder characterized by low bone mineral density (BMD) and reduced bone strength leading to higher bone fractures risk. The present study attempted to investigate the effects of concurrent training (aerobic-resistance) and milk consumption on some markers of BMD in women with osteoporosis.MethodsFor this purpose, forty women diagnosed with osteoporosis within an age range of 30-45 years were divided into four groups of ten including concurrent training-milk, concurrent training, milk consumption and control group. The concurrent exercises were performed in ten weeks with three sessions in each week including aerobic training (running at 55–75% of maximum heart rate) and resistance training (4 move in a circle performed two times with 10 repetition maximum (RM)). Milk consumption was two times of 250 ml per day in ten weeks. Before and after treatment, BMDs in the hip and lumbar spine area were estimated with Dual-energy X-ray absorptiometry (DEXA) device and 5 cc blood was taken from a vein in the arm to determine the blood levels of 25-hydroxyvitamin D (25OH-D) and alkaline phosphatase (ALP).ResultsBased on the results, blood levels 25OH-D and ALP significantly increased in concurrent training-milk, concurrent training and milk group with higher increase in concurrent training-milk group (P < 0.05). Furthermore, the right and left hip BMD in concurrent training-milk and concurrent training groups increased significantly with higher increase in concurrent training-milk group (p < 0.05). Also, lumbar spine BMD increased significantly in concurrent training-milk and concurrent training (p < 0.05).ConclusionsIt seems that combination of concurrent training and milk consumption has more efficient impacts on the BMD of young women diagnosed with osteoporosis compared to the milk or concurrent training groups alone. This treatment can be used as an effective way to improve BMD in young women with diagnosed osteoporosis.

No abstract

No abstract

Now, Osteoporosis (OP) is considered one of health threatening diseases in men and women. Physical activity can act critical for bone development, bone health, and fracture risk reduction. It is an effective, low cost and sound way to inhibit the progression of OP if perform regularly and have a structured base. Progression of OP is often related to either little accumulation of peak bone mass before to obtain of skeletal maturity or to excessive rate of bone loss in aging process. Given the rapid aging of societies worldwide, and the fact that no cure exists for osteoporosis, without adequate preventive strategies, the burden of these fractures is likely to grow exponentially. The purpose of this review was to convey the effects of different types of physical training on bone mineral density (BMD) principally at the hip and spine in men and women. Keywords OsteoporosisOsteoporosis (OP) is a serious skeletal disorder induced by bone mass reduction and micro-architectural deterioration of bone tissue that consequently lead to more fragility in bone and also frequent fractures [1]. This chronic disease causes 1.5 million fractures annually, 700,000 of which occur at the spine [2]. Base on the studies, it has been reported that 50% of women, and 20% of men with the age of 50 and over, will have fractures related to OP in their life time [3]. Osteoporotic fractures commonly occur at the hip, spine and wrist and of these hip fractures have the highest short-term mortality, morbidity and associated socio-economic impact [4,5]. After the age of 40, BMD declines progressively, 0.5% per year or more, especially in women. This decline approaches their mortality rate to 20% following hip fractures. Moreover, the other 2 sites are susceptible with fracture including the spine and the wrist [6]. Fractures lead to more mortality, morbidity, chronic pain, reduction in the quality of life, long-term attention, social and health care costs [7].Typically, the diagnosis of OP is based on the BMD of the lumbar spine and hip measured by dual-emission X-ray absorptiometry (DEXA). In a pre or post-menopausal woman a T-score ≤ 2.5 (at least 2.5 standard deviations below the average BMD of a young woman) defines osteoporosis according to the World Health Organization (WHO). A T-score between -1 and -2.5 signifies osteopenia [6,8,9]. DXA is defined as the "gold standard" because experts identified it as high technique with high validation biologically [10].Periods of growth are thought to be the best time to increase bone mineral content, bone area, and areal bone mineral density (aBMD) through increased loading owing to high rates of bone modeling and remodeling [11]. Bone stability links to a lot of interconnected factors, including the size and mass of bone tissue, the structural network of bone and the internal properties of the bone material (porosity, matrix mineralization, collagen traits and micro-damage) [12].The skeletal performance is presented as two functions. First related with metabolism and second is related to b...