Imaging your muscle looks like a raw chicken breast! Within that chicken breast (muscle) you will see lots of lines, these are muscle fibres. These fibres need to contract and relax to make the muscle work. When a muscle gets tight these fibres stay contracted, and instead of lying flat get twisted and tangled which reduces blood flow. At this point you start to notice your muscle feel tight and uncomfortable. Most of the time the muscle will relax by resting it, however if you overload a muscle constantly (usually work related), it will become increasingly tight tangled and rigid, needing some manipulation to get it back to its normal state. Massage works by lengthening and straightening the fibres, increasing blood flow, and relaxing the muscle back to its normal state.