Regular exercise increases vigor and promotes a general sense of well-being. If done in moderation, it can help relieve the effects of stress and has been linked to a decrease in psychological depression.

Regular exercise produces positive physical results like increased muscular strength and endurance, more efficient heart and respiratory functioning, and greater flexibility.

These positive physical changes occur as the body gradually adapts to the greater demands put on it by regular exercise. The body improves its functioning to meet the challenges placed on it.

Conditioning involves three steps or phases:

• Tearing Down Phase when one pushes the physical limits
• Recovery Phase - Important for the rebuilding phase and to obtain the full benefits of a conditioning program, and 
• Buildup Phase - when the system adapts to the new demands placed on it.

The 'tearing down' phase of the adaptation process often involves stiffness and soreness, especially when the amount of movement is significantly increased from what the body has been used to in the past.

Delayed muscle soreness (24-48 hours after exercise) may be caused by any of a number of different factors. Some possible causes are minor muscle or connective tissue damage, local muscle spasms that reduce blood flow, or a build-up of waste products (metabolites) from energy production.

Trigger points or stress points may also cause muscle soreness and decreased flexibility. These points are specific spots in muscle and tendons which cause pain when pressed, and which may radiate pain to a larger area. They are not bruises but are thought by some to be small areas of spasm. Trigger points may be caused by sudden trauma (like falling or being hit) or may develop over time from the stress and strain of heavy physical exertion or from repeated use of a particular muscle.

Heavily exercised muscles may also lose their capacity to relax, causing chronically tight (hypertonic) muscles, and loss of flexibility. Lack of flexibility is often linked to muscle soreness, and predisposes you to injuries, especially muscle pulls and tears. Blood flow through tight muscles is poor (ischemia), which also causes pain.