Weight-training programs often focus on three related muscular attributes: strength, stamina and endurance. Though these are all related, they are distinct concepts as related to your physical abilities.
The concept of muscular strength seems difficult, but it's actually quite simple. It's 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. For example, an Olympic weightlifter is a strength-based athlete, and 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 pounds, you might have stronger bicep muscles than someone whose maximal bicep curl is 50 pounds.
However, 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.
Unlike strength, but like stamina, endurance is related 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.
Therefore, 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.
Which is Most Important?
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 can 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.