Resistance training is defined as any exercise that involves muscles contracting against an external resistance or weight. These types of exercises increase muscle strength, tone, mass (size), and/or endurance (stamina). As a process, resistance exercises first break down or injure muscle cells (catabolism) and then repair, rebuild, and strengthen muscle cells (anabolism).
The “external resistance” in resistance training can be rubber resistance bands, dumbbells, weighted bars, kettlebells, water bottles, cans of vegetables, or your own body weight.
Depending on your goals, resistance training can be utilized for muscle definition—a tighter, more sculpted, and physically fit appearance. To “bulk up,” more resistance or greater weight can be used. By increasing muscle mass, you’ll increase your metabolism and burn more calories at rest; assuming that you don’t eat any extra calories, you will lose fat mass. Your body weight may stay the same or go up slightly due to the extra muscle mass, but you’ll notice a difference in how much better your clothes fit you.
After age 30, otherwise healthy individuals begin losing muscle mass—as much as 3 to 5% per decade thereafter. Many chronic diseases, including diabetes and obesity, are believed to accelerate the decline of both muscle mass and strength, thereby increasing the risk of sarcopenia and physical disability and decreasing health span4.
