Swimming offers a relatively low-intensity pec workout.
Swimming isn't just a way to blow off steam during a hot summer day. It also offers cardiovascular exercise that can range from moderate to intense. Swimming works your pectoral muscles, but because the resistance is minimal, swimming is unlikely to yield very large, very hard pecs. If you want to dramatically shape your pecs, you'll need to incorporate other workouts instead.
How Swimming Engages Your Pecs
The primary job of the pecs is to move your shoulders, and almost all swimming styles rely heavily on shoulder movement. As you lift your arms up, your pecs aid in rotating and flexing your shoulders, and when your arms hit the water and push back toward your body, your pecs help to push your shoulders back down.
Limitations of Swimming
When you swim, two forces act on your pecs: the force of your body weight and the force of the water. In most cases, these forces don't provide enough resistance to give you a truly intense pectoral workout. Instead, swimming offers moderate exercise that can keep your pecs toned but is unlikely to add significant bulk.
Swimming for Weight Loss
Because swimming is a form of cardiovascular exercise, it can help you burn calories. Over time, this can lead to a reduction in body fat. As your body sheds fat, the muscle tissue becomes more visible. This means that, in addition to building muscles, swimming can also help your pecs look more defined simply by burning excess fat.
Other Pectoral Exercises
If you want to sculpt strong, large pecs, incorporate weightlifting into your exercise routine. The bench press strengthens your chest, shoulders and back, while the chest dip acts on your chest, shoulders and arms. Other good chest exercises include pushups, chest presses, flies and pullovers. The more weight you add, the more muscle you'll build, but focus on adding weight slowly and steadily rather than overloading your body, as this strategy can cause painful injuries.