Athletes: Individuals who have developed skills, physical stamina and strength or participants in SPORTS or other physical activities.Sports: Activities or games, usually involving physical effort or skill. Reasons for engagement in sports include pleasure, competition, and/or financial reward.Athletic Injuries: Injuries incurred during participation in competitive or non-competitive sports.Track and Field: Sports performed on a track, field, or arena and including running events and other competitions, such as the pole vault, shot put, etc.Athletic Performance: Carrying out of specific physical routines or procedures by one who is trained or skilled in physical activity. Performance is influenced by a combination of physiological, psychological, and socio-cultural factors.Sports Medicine: The field of medicine concerned with physical fitness and the diagnosis and treatment of injuries sustained in exercise and sports activities.Doping in Sports: Illegitimate use of substances for a desired effect in competitive sports. It includes humans and animals.Female Athlete Triad Syndrome: A condition of competitive female athletes in which there are interrelated problems of EATING DISORDERS; AMENORRHEA; and OSTEOPOROSIS.Physical Endurance: The time span between the beginning of physical activity by an individual and the termination because of exhaustion.Running: An activity in which the body is propelled by moving the legs rapidly. Running is performed at a moderate to rapid pace and should be differentiated from JOGGING, which is performed at a much slower pace.Martial Arts: Activities in which participants learn self-defense mainly through the use of hand-to-hand combat. Judo involves throwing an opponent to the ground while karate (which includes kung fu and tae kwon do) involves kicking and punching an opponent.Brain Concussion: A nonspecific term used to describe transient alterations or loss of consciousness following closed head injuries. The duration of UNCONSCIOUSNESS generally lasts a few seconds, but may persist for several hours. Concussions may be classified as mild, intermediate, and severe. Prolonged periods of unconsciousness (often defined as greater than 6 hours in duration) may be referred to as post-traumatic coma (COMA, POST-HEAD INJURY). (From Rowland, Merritt's Textbook of Neurology, 9th ed, p418)Basketball: A competitive team sport played on a rectangular court having a raised basket at each end.Physical Education and Training: Instructional programs in the care and development of the body, often in schools. The concept does not include prescribed exercises, which is EXERCISE THERAPY.Soccer: A game in which a round inflated ball is advanced by kicking or propelling with any part of the body except the hands or arms. The object of the game is to place the ball in opposite goals.Wrestling: A sport consisting of hand-to-hand combat between two unarmed contestants seeking to pin or press each other's shoulders to the ground.Baseball: A competitive nine-member team sport including softball.Football: A competitive team sport played on a rectangular field. This is the American or Canadian version of the game and also includes the form known as rugby. It does not include non-North American football (= SOCCER).Tennis: A game played by two or four players with rackets and an elastic ball on a level court divided by a low net.Cardiomegaly, Exercise-Induced: Heart enlargement and other remodeling in cardiac morphology and electrical circutry found in individuals who participate in intense repeated exercises.Volleyball: A team sport in which two teams hit an inflated ball back and forth over a high net using their hands.Performance-Enhancing Substances: Agents that improve the ability to carry out activities such as athletics, mental endurance, work, and resistance to stress. The substances can include PRESCRIPTION DRUGS; DIETARY SUPPLEMENTS; phytochemicals; and ILLICIT DRUGS.Bicycling: The use of a bicycle for transportation or recreation. It does not include the use of a bicycle in studying the body's response to physical exertion (BICYCLE ERGOMETRY TEST see EXERCISE TEST).Amenorrhea: Absence of menstruation.Racquet Sports: Games in which players use a racquet to hit a ball or similar type object.Exercise: Physical activity which is usually regular and done with the intention of improving or maintaining PHYSICAL FITNESS or HEALTH. Contrast with PHYSICAL EXERTION which is concerned largely with the physiologic and metabolic response to energy expenditure.Fractures, Stress: Fractures due to the strain caused by repetitive exercise. They are thought to arise from a combination of MUSCLE FATIGUE and bone failure, and occur in situations where BONE REMODELING predominates over repair. The most common sites of stress fractures are the METATARSUS; FIBULA; TIBIA; and FEMORAL NECK.Knee Injuries: Injuries to the knee or the knee joint.Anabolic Agents: These compounds stimulate anabolism and inhibit catabolism. They stimulate the development of muscle mass, strength, and power.Cumulative Trauma Disorders: Harmful and painful condition caused by overuse or overexertion of some part of the musculoskeletal system, often resulting from work-related physical activities. It is characterized by inflammation, pain, or dysfunction of the involved joints, bones, ligaments, and nerves.Skiing: A snow sport which uses skis to glide over the snow. It does not include water-skiing.Anterior Cruciate Ligament: A strong ligament of the knee that originates from the posteromedial portion of the lateral condyle of the femur, passes anteriorly and inferiorly between the condyles, and attaches to the depression in front of the intercondylar eminence of the tibia.Sports Equipment: Equipment required for engaging in a sport (such as balls, bats, rackets, skis, skates, ropes, weights) and devices for the protection of athletes during their performance (such as masks, gloves, mouth pieces).Sprains and Strains: A collective term for muscle and ligament injuries without dislocation or fracture. A sprain is a joint injury in which some of the fibers of a supporting ligament are ruptured but the continuity of the ligament remains intact. A strain is an overstretching or overexertion of some part of the musculature.Death, Sudden, Cardiac: Unexpected rapid natural death due to cardiovascular collapse within one hour of initial symptoms. It is usually caused by the worsening of existing heart diseases. The sudden onset of symptoms, such as CHEST PAIN and CARDIAC ARRHYTHMIAS, particularly VENTRICULAR TACHYCARDIA, can lead to the loss of consciousness and cardiac arrest followed by biological death. (from Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005)Epitestosterone: The 17-alpha isomer of TESTOSTERONE, derived from PREGNENOLONE via the delta5-steroid pathway, and via 5-androstene-3-beta,17-alpha-diol. Epitestosterone acts as an antiandrogen in various target tissues. The ratio between testosterone/epitestosterone is used to monitor anabolic drug abuse.Physical Fitness: The ability to carry out daily tasks and perform physical activities in a highly functional state, often as a result of physical conditioning.Asthma, Exercise-Induced: Asthma attacks following a period of exercise. Usually the induced attack is short-lived and regresses spontaneously. The magnitude of postexertional airway obstruction is strongly influenced by the environment in which exercise is performed (i.e. inhalation of cold air during physical exertion markedly augments the severity of the airway obstruction; conversely, warm humid air blunts or abolishes it).Weight Lifting: A sport in which weights are lifted competitively or as an exercise.Ankle Injuries: Harm or hurt to the ankle or ankle joint usually inflicted by an external source.Physical Exertion: Expenditure of energy during PHYSICAL ACTIVITY. Intensity of exertion may be measured by rate of OXYGEN CONSUMPTION; HEAT produced, or HEART RATE. Perceived exertion, a psychological measure of exertion, is included.Skating: Using ice skates, roller skates, or skateboards in racing or other competition or for recreation.Leg Injuries: General or unspecified injuries involving the leg.Universities: Educational institutions providing facilities for teaching and research and authorized to grant academic degrees.Exercise Test: Controlled physical activity which is performed in order to allow assessment of physiological functions, particularly cardiovascular and pulmonary, but also aerobic capacity. Maximal (most intense) exercise is usually required but submaximal exercise is also used.Spondylolysis: Deficient development or degeneration of a portion of the VERTEBRA, usually in the pars interarticularis (the bone bridge between the superior and inferior facet joints of the LUMBAR VERTEBRAE) leading to SPONDYLOLISTHESIS.Swimming: An activity in which the body is propelled through water by specific movement of the arms and/or the legs. Swimming as propulsion through water by the movement of limbs, tail, or fins of animals is often studied as a form of PHYSICAL EXERTION or endurance.Tendinopathy: Clinical syndrome describing overuse tendon injuries characterized by a combination of PAIN, diffuse or localized swelling, and impaired performance. Distinguishing tendinosis from tendinitis is clinically difficult and can be made only after histopathological examination.Altitude: A vertical distance measured from a known level on the surface of a planet or other celestial body.Cardiomyopathy, Hypertrophic: A form of CARDIAC MUSCLE disease, characterized by left and/or right ventricular hypertrophy (HYPERTROPHY, LEFT VENTRICULAR; HYPERTROPHY, RIGHT VENTRICULAR), frequent asymmetrical involvement of the HEART SEPTUM, and normal or reduced left ventricular volume. Risk factors include HYPERTENSION; AORTIC STENOSIS; and gene MUTATION; (FAMILIAL HYPERTROPHIC CARDIOMYOPATHY).Oxygen Consumption: The rate at which oxygen is used by a tissue; microliters of oxygen STPD used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (Stedman, 25th ed, p346)Wheelchairs: Chairs mounted on wheels and designed to be propelled by the occupant.Hockey: A game in which two parties of players provided with curved or hooked sticks seek to drive a ball or puck through opposite goals. This applies to either ice hockey or field hockey.Foot Injuries: General or unspecified injuries involving the foot.Patellofemoral Pain Syndrome: A syndrome characterized by retropatellar or peripatellar PAIN resulting from physical and biochemical changes in the patellofemoral joint. The pain is most prominent when ascending or descending stairs, squatting, or sitting with flexed knees. There is a lack of consensus on the etiology and treatment. The syndrome is often confused with (or accompanied by) CHONDROMALACIA PATELLAE, the latter describing a pathological condition of the CARTILAGE and not a syndrome.Biomechanical Phenomena: The properties, processes, and behavior of biological systems under the action of mechanical forces.Competitive Behavior: The direct struggle between individuals for environmental necessities or for a common goal.Students: Individuals enrolled in a school or formal educational program.Adaptation, Physiological: The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT.Muscle, Skeletal: A subtype of striated muscle, attached by TENDONS to the SKELETON. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles.Electrocardiography: Recording of the moment-to-moment electromotive forces of the HEART as projected onto various sites on the body's surface, delineated as a scalar function of time. The recording is monitored by a tracing on slow moving chart paper or by observing it on a cardioscope, which is a CATHODE RAY TUBE DISPLAY.Hip Injuries: General or unspecified injuries involving the hip.Arthroscopy: Endoscopic examination, therapy and surgery of the joint.Physical Examination: Systematic and thorough inspection of the patient for physical signs of disease or abnormality.Groin: The external junctural region between the lower part of the abdomen and the thigh.Back Injuries: General or unspecified injuries to the posterior part of the trunk. It includes injuries to the muscles of the back.Menstruation Disturbances: Variations of menstruation which may be indicative of disease.Substance Abuse Detection: Detection of drugs that have been abused, overused, or misused, including legal and illegal drugs. Urine screening is the usual method of detection.Tendon Injuries: Injuries to the fibrous cords of connective tissue which attach muscles to bones or other structures.Shoulder Joint: The articulation between the head of the HUMERUS and the glenoid cavity of the SCAPULA.Joint Instability: Lack of stability of a joint or joint prosthesis. Factors involved are intra-articular disease and integrity of extra-articular structures such as joint capsule, ligaments, and muscles.Echocardiography: Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic.Anaerobic Threshold: The oxygen consumption level above which aerobic energy production is supplemented by anaerobic mechanisms during exercise, resulting in a sustained increase in lactate concentration and metabolic acidosis. The anaerobic threshold is affected by factors that modify oxygen delivery to the tissues; it is low in patients with heart disease. Methods of measurement include direct measure of lactate concentration, direct measurement of bicarbonate concentration, and gas exchange measurements.Mouth Protectors: Devices or pieces of equipment placed in or around the mouth or attached to instruments to protect the external or internal tissues of the mouth and the teeth.Tooth Injuries: Traumatic or other damage to teeth including fractures (TOOTH FRACTURES) or displacements (TOOTH LUXATION).Hypertrophy, Left Ventricular: Enlargement of the LEFT VENTRICLE of the heart. This increase in ventricular mass is attributed to sustained abnormal pressure or volume loads and is a contributor to cardiovascular morbidity and mortality.Arm Injuries: General or unspecified injuries involving the arm.Eating Disorders: A group of disorders characterized by physiological and psychological disturbances in appetite or food intake.Rest: Freedom from activity.Cardiovascular Deconditioning: A change in cardiovascular function resulting in a reduction in BLOOD VOLUME, and reflex DIURESIS. It occurs frequently after actual or simulated WEIGHTLESSNESS.Anterior Cruciate Ligament Reconstruction: Rebuilding of the ANTERIOR CRUCIATE LIGAMENT to restore functional stability of the knee. AUTOGRAFTING or ALLOGRAFTING of tissues is often used.Boxing: A two-person sport in which the fists are skillfully used to attack and defend.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Osteochondrosis: Any of a group of bone disorders involving one or more ossification centers (EPIPHYSES). It is characterized by degeneration or NECROSIS followed by revascularization and reossification. Osteochondrosis often occurs in children causing varying degrees of discomfort or pain. There are many eponymic types for specific affected areas, such as tarsal navicular (Kohler disease) and tibial tuberosity (Osgood-Schlatter disease).Heart Rate: The number of times the HEART VENTRICLES contract per unit of time, usually per minute.Rupture: Forcible or traumatic tear or break of an organ or other soft part of the body.Range of Motion, Articular: The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate MUSCLE STRETCHING EXERCISES.Patellar Ligament: A band of fibrous tissue that attaches the apex of the PATELLA to the lower part of the tubercle of the TIBIA. The ligament is actually the caudal continuation of the common tendon of the QUADRICEPS FEMORIS. The patella is embedded in that tendon. As such, the patellar ligament can be thought of as connecting the quadriceps femoris tendon to the tibia, and therefore it is sometimes called the patellar tendon.