Medicine and Sport Science

Type 2 diabetes mellitus and its precursor, insulin resistance, are metabolic disease states characterized by impaired regulation in the delivery, transport, and/or storage of energy substrates (primarily carbohydrate- and fat-based fuels). A hallmark feature of patients with type 2 diabetes is prolonged periods of hyperglycemia due to a decreased responsiveness of metabolically active peripheral tissues to the actions of insulin (i.e., metabolic inflexibility). Accordingly, efforts to modify skeletal muscle substrate handling in type 2 diabetes patients so that the capacity for fat oxidation and metabolic flexibility is improved should be a primary goal for the treatment of these disorders...

Despite ongoing improvements to regulatory and manufacturing guidelines, the potential for contaminated nutritional supplements to cause a failed doping test for an athlete remains a concern. Several surveys of supplements available through the internet and at retail have confirmed that many are contaminated with steroids and stimulants that are prohibited for use in elite sport. Suggested responses to this issue include the complete avoidance of all supplements. However, this approach seems to be unrealistic as many athletes use nutritional supplements for very different reasons...

L-Carnitine is a conditionally essential nutrient and plays an important role in mitochondrial β-oxidation. As a dietary supplement for athletes, L-carnitine has been investigated for its potential to enhance β-oxidation during exercise ultimately to improve performance. While some studies have shown a positive impact on VO(2 max) and other performance measures, other studies have found contradictory results. As such, investigations to a different mechanism by which L-carnitine supplementation could impact exercise and recovery were explored...

An optimal post-exercise nutrition regimen is fundamental for ensuring recovery. Therefore, research has aimed to examine post-exercise nutritional strategies for enhanced training stimuli. Chocolate milk has become an affordable recovery beverage for many athletes, taking the place of more expensive commercially available recovery beverages. Low-fat chocolate milk consists of a 4:1 carbohydrate:protein ratio (similar to many commercial recovery beverages) and provides fluids and sodium to aid in post-workout recovery...

Sweat is produced during exercise to help dissipate some of the extra heat produced due to an increase in metabolic rate. Inadequate drink ingestion during exercise means athletes finish exercise hypohydrated and when the time between exercise bouts is short, effective rehydration strategies will be necessary to prevent subsequent performance impairment. For complete rehydration, drink volume must be sufficient to replace sweat losses as well as the additional water losses during recovery. Once a sufficient volume of drink is ingested it is the drink composition that dictates the rehydration success of the drink...

During prolonged exercise, fluid and salt losses through sweating reduce plasma volume which leads to heart rate drift in association with hyperthermia and reductions in performance. Oral rehydration with water reduces the loss of plasma volume and lessens heart rate drift and hyperthermia. Moreover, the inclusion of sodium in the rehydration solution to levels that double those in sweat (i.e., around 90 mmol/l Na(+)) restores plasma volume when ingested during exercise, and expands plasma volume if ingested pre-exercise...

Glycerol ingestion creates an osmotic drive that enhances fluid retention. The major practical applications for athletes are to either (i) hyperhydrate before exercise so that they have more fluid to be lost as sweat during subsequent performance, thereby delaying the progression of dehydration from becoming physiologically significant, or (ii) improve both the rate of rehydration and total fluid retention following exercise. Recently we showed that rehydration may be improved further by combining glycerol with intravenous fluids...

Resistance exercise (RE) preceding the provision of high-quality dairy protein supports muscle anabolism. Milk contains bioactive components, including two high-quality protein fractions, calcium and vitamin D, each of which has been shown modulate body composition (increasing lean mass and decreasing fat mass) under energy balance and hypoenergetic conditions. These dairy nutrients are also essential for skeletal health. Acutely, no study of RE and milk/whey consumption has been undertaken exclusively in female athletes, let alone women, nevertheless, studies with both men and women show increased lean mass accretion following milk/whey compared to soy/placebo...

Strenuous physical activity increases the risk of musculoskeletal injury and can induce muscle damage resulting in acute inflammation and decreased performance. The human body's natural response to injury results in inflammation-induced pain, swelling, and erythema. Among sports medicine physicians and athletic trainers, the mainstays of urgent treatment of soft tissue injury are rest, ice, compression, and elevation (RICE). In order to reduce pain and inflammation, anti-inflammatory agents such as non-steroidal anti-inflammatory drugs (NSAIDs) act on the multiple inflammatory pathways, which, although often very effective, can have undesirable side effects such as gastric ulceration and, infrequently, myocardial infarction and stroke...

Regular consumption of fruits and vegetables (FV) is widely regarded as an important contributor to a healthy diet. Inadequate consumption of plant foods is associated with an inadequate supply of important micronutrients like vitamins, phytochemicals and minerals. In athletes a deficit of these micronutrients can lead to excessive production of reactive oxygen and nitrogen species that induce tissue damage, a higher frequency of inflammatory processes, decreased immunity, increased susceptibility to injury, and prolonged recovery...

Strenuous and/or prolonged exercise causes transient perturbations in immune function. It is well accepted that this is one mechanism contributing to the higher occurrence of infection (e.g. upper respiratory tract infection (URTI)) in athletes, especially endurance athletes. URTI or upper respiratory tract (URT) symptoms can negatively affect training and competition performance but athletes must train intensively to be successful. Therefore, interventions that can legitimately enhance immune function and reduce URTI risk can be of benefit to athletes...

Prolonged and high-intensity exercise affects immune function and leads to an increased risk of upper respiratory tract infections (URTIs) in endurance athletes. The increased incidence of URTI symptoms may negatively affect athletic performance. Various nutritional supplements have been tested in the last decade for their ability to prevent developing of URTIs or reduce their incidence. One of the most promising nutritional supplements is β-glucan, a well-known immunomodulator with positive effects on functioning of immunocompetent cells...

Athletes exposed to high-intensity exercise show an increased occurrence of gastrointestinal (GI) symptoms like cramps, diarrhea, bloating, nausea, and bleeding. These problems have been associated with alterations in intestinal permeability and decreased gut barrier function. The increased GI permeability, a so-called 'leaky gut', also leads to endotoxemia, and results in increased susceptibility to infectious and autoimmune diseases, due to absorption of pathogens/toxins into tissue and the bloodstream. Key components that determine intestinal barrier function and GI permeability are tight junctions, protein structures located in the paracellular channels between epithelial cells of the intestinal wall...

The secretion of growth hormone (GH) is regulated through a complex neuroendocrine control system, especially by the functional interplay of two hypothalamic hormones, GH-releasing hormone and somatostatin. These hormones are subject to modulation by a host of neurotransmitters and are the final mediators of endocrine and neural influences for GH secretion. Interest in the possible role of γ-aminobutyric acid (GABA) in the control of GH secretion began decades ago. However, interest in its role as an ergogenic aid is only recent...

Recent studies have investigated the influence of dietary nitrate supplementation on the physiological responses to exercise. Specifically, it has been reported that enhancing nitric oxide (NO) bioavailability through supplementation of the diet with nitrate salts or nitrate-rich beetroot juice reduces the O(2) cost of exercise and improves exercise performance. The lower O(2) cost for a given sub-maximal work rate following nitrate ingestion indicates that muscle efficiency is enhanced either as a consequence of a reduced energy cost of contraction or enhanced mitochondrial efficiency...

Dietary L-citrulline malate supplements may increase levels of nitric oxide (NO) metabolites, although this response has not been related to an improvement in athletic performance. NO plays an important role in many functions in the body regulating vasodilatation, blood flow, mitochondrial respiration and platelet function. L-Arginine is the main precursor of NO via nitric oxide synthase (NOS) activity. Additionally, L-citrulline has been indicated to be a second NO donor in the NOS-dependent pathway, since it can be converted to L-arginine...

Glycolysis involves the oxidation of two neutral hydroxyl groups on each glycosyl (or glucosyl) unit metabolised, yielding two carboxylic acid groups. During low-intensity exercise these, along with the remainder of the carbon skeleton, are further oxidised to CO(2) and water. But during high-intensity exercise a major portion (and where blood flow is impaired, then most) is accumulated as lactate anions and H(+). The accumulation of H(+) has deleterious effects on muscle function, ultimately impairing force production and contributing to fatigue...

Off-road motorsports are popular in rural and suburban areas, and allow for racing, recreation, and easy access to backcountry destinations. This chapter will review the incidence and types of injuries sustained in off-road motorsports. We completed a structured review of motocross and all-terrain vehicle (ATV) injuries, assessing for injury rates, risk factors, and mortality figures. Information for this study was obtained from a PubMed search under the terms 'motocross', 'motorcross', 'all-terrain vehicles', 'injury', 'motorcycle', 'ATV'...

The purpose of this report is to review the available literature to provide an epidemiological overview of skateboarding injuries, as well as to suggest possible areas for future research. A literature search was performed with the databases of PubMed, Sport Discus, Google and Google Scholar using the search terms 'skateboard', 'skateboarding', 'injury' and 'injuries', with all articles published in refereed journals in the English language being considered. An ancestry approach was also used. Articles from non-juried journals were also infrequently included to provide anecdotal information on the sport...

The objective of this review was to summarize the epidemiological literature for extreme hikers in volcanic environments and describe the incidence, nature and severity of injuries, the factors contributing to the injuries, and strategies for preventing injuries. Due to the relative newness of extreme hiking in volcanic environments, there are only a small handful of studies addressing the topic. Moreover, these studies are primarily focused on extreme hikers in Hawaii Volcanoes National Park. These studies found that the majority of extreme hikers in volcanic environments are inexperienced and unfamiliar with the potential hazards present in volcanic environments...