Weight-training programs often focus on increases in three related muscular attributes: strength, stamina and endurance. Though related, these three are distinct concepts as they relate to your physical abilities. Because increases in each bring different benefits, design your exercise program to target muscular strength, stamina or endurance, depending on your needs.
The concept of muscular strength is best understood as the maximum amount of weight that a given muscle or group of muscles can withstand. Exercises that target strength focus on increases in the amount that a group of muscles can lift for a single repetition. An example of a strength-based athlete is an Olympic weightlifter; a single lift of a maximum amount of weight is the focus of her sport.
Related to strength, stamina is best understood as the amount of time that a given muscle or group of muscles can perform at maximum capacity. If you can perform a single bicep curl of 60 lbs., you may have stronger bicep muscles than someone whose maximal bicep curl is 50 lbs., but the other person can be said to have greater bicep stamina if he can perform more repetitions at this maximum weight. An example of an athlete who may benefit from increased stamina is a sprinter, who must run at maximum speed for an extended period.
Endurance is best understood in relation to time. While stamina is defined as the amount of time that a given group of muscles can perform at or near maximum capacity, endurance is defined as the maximum amount of time that a given group of muscles can perform a certain action. So the difference between stamina and endurance is one of focus: while stamina is limited to performing at maximum capacity, the focus of endurance is on maximizing time regardless of the capacity at which a given group of muscles is performing.
For example, while a sprinter may focus on stamina and running as fast as possible over a given distance, a long-distance runner may be more interested in endurance: he runs as far as possible with speed a secondary concern.
The effects of exercise programs specifically targeting strength, endurance and stamina spill over to affect all three. For example, while strength training can be used to increase both strength and endurance, endurance training is effective at increasing stamina, strength and endurance.
Health Risks and Benefits
Endurance training has significant cardiovascular health benefits over resistance -- or strength -- training. Though both increase your maximum oxygen uptake, the increases from strength training are less. Also, though endurance training leads to decreases in resting heart rate and in systolic and diastolic blood pressure, strength training has little effect on them. Both may be incorporated into treatment and prevention programs for diabetes, and both may be used to increase metabolism and reduce weight.
Despite such benefits of strength training, the sharp increase in blood pressure after single-repetition exercises may be dangerous if you have a cardiovascular condition. Consult your doctor before taking on a strength or endurance training program.