Rest and recovery are essential to a weightlifter. However, prolonged periods of insufficient training stimulus causes muscle detraining. About three weeks of inactivity may decrease capillary density. Decreased capillary density decreases the oxygen transport to your muscles, diminishing your ability to perform an intense exercise such as lifting weights. Your strength performance can be maintained up to four weeks of inactivity -- however, sport-specific power and eccentric force declines significantly, according to the American College of Sports Medicine.
Bones are adaptable, their shapes and strength reflect the forces applied to them. Weight lifting places stress on your bones; this stress facilitates stronger bones. The remodeling of the bone helps to meet the new stress imposed at the site of the tendon and muscular attachment. Therefore, regular exercise is important in maintaining bone structure. This makes exercise, specifically weight lifting, important for preventing degenerative changes in the skeleton that occur with prolonged inactivity.
Weight lifting stimulates muscle hypertrophy, or growth, with proper nutrition and repeated stimulation to near-maximal tension. When your skeletal muscle is not repeatedly stimulated -- or you've become sedentary -- your muscle loses mass. Your muscle fiber become smaller and weaker. This process is known as atrophy. Those who actively engage in weight training for years can maintain their fitness level for several weeks; however, further sedentary can result in rapid atrophy. "Human Anatomy," notes even a temporary reduction in muscle use can lead to muscular atrophy; this loss of size is seen when comparing limb muscles before and after a cast has been worn.
Regular weight lifting and exercise demonstrate not only muscle hypertrophy, but physiological and physical benefits too. Benefits include enhanced heart function, improved balance, healthier body composition -- meaning more muscle mass, less body fat -- better sleep habits, and reduced injury to tendons and muscles. Regular physical activity also positively affects blood pressure, blood glucose regulation, immune function, and blood cholesterol levels. A sedentary lifestyle robs you of all the benefits of regular exercise and weight lifting.