Strength is defined as the ability of a muscle to exert force against resistance, such as weights or your own bodyweight. Strength training involves exercises that increase muscle size, improve balance, and prevent injuries. It can also help you manage your weight, and strengthen bones and joints.
Most sports trainers will tell you that increasing your physical strength will make you faster, jump higher, and hit harder. But they will rarely give a clear definition of what constitutes true physical strength.
It is important to distinguish strength training from sports conditioning. Conditioning typically involves a higher heart rate (up to around 80% of maximum) and more repetitions than strength training.
Flexibility is the ability of muscles, joints and connective tissues to move through a full range of motion without restriction. Flexibility exercises (stretches) can be performed by people of any age and can increase flexibility over time.
Flexibility varies from person to person and is highly specific to the individual joint of the body. For example, the hip joint is different from the shoulder. This makes it difficult to link flexibility and one or more health outcomes like back pain or injury prevention.
The most commonly used field test to assess flexibility is the sit-and-reach test in which the person seated with legs a certain distance apart stretches to touch their toes.
Aggression is a behavior that involves threatening or attacking another person. It can be either physical or verbal.
Differential reproductive success is a major driving force of natural selection for aggression. It allows individuals to compete for resources such as territory, mates, food and water.
Biological causes of aggression include genetics, brain structures, medical and psychiatric diseases, neurotransmitters, hormones, and drugs of abuse. Psychologically, numerous Diagnostic and Statistical Manual of Mental Disorders (DSM-5) diagnoses are associated with aggressive behaviors, including bipolar affective disorder, schizophrenia, the dementia group, and some personality disorders.
Frustration is one of the main psychological causes of aggression. A frustration aggression theory suggests that the amount of aggression increases when a person is prevented from achieving an important goal.