It is a common belief that muscles only grow when they are sore, but this is not necessarily true. While it is true that muscles will experience the most growth when they are taxed and pushed to their limits, they can still continue to grow even when they are not sore. This is because muscle growth is a result of microtrauma to the muscle fibers. When these fibers are repaired, they come back stronger and larger than before. So, while you may not see as much visible growth if you are not experiencing post-workout soreness, your muscles can still be growing on the inside.