Muscular fitness is when a group of muscles are able to contract continuously without beginning to fatigue. On the other hand, cardiovascular fitness focuses on the levels of oxygen that the muscles receive and use.
The main difference between muscular and cardiovascular fitness is that a limitation of oxygen being supplied to the muscles will occur in cardiovascular fitness. In muscular fitness, the oxygen to the muscles is not being decreased, but the muscles are simply not able to continue contracting. The more times a muscle is able to contract without becoming fatigued, the better the muscular fitness is. Muscular fitness is nearly as important as cardiovascular fitness to ensure that the muscles are able to endure long periods of contractions.
Many people who participate in field sports may not practice regimens focused on muscular fitness because of the need to focus on cardiovascular fitness. Muscular fitness is still important for athletes who have a cardiovascular focus because it allows the muscles to execute running, jumping, and kicking over longer periods of time without fatigue. In particular, rowers and athletes who engage in repetitive muscle movements can greatly benefit from fitness routines that focus on strength.