Gaining some serious muscle (as in Hulk-like proportions) will definitely stretch your skin, but it usually won't stretch a tattoo enough to warp its appearance. Even if you lift heavy and often, the bulking up typically won't happen fast enough to impact the appearance of a tattoo.

If there is weight gain, there's a chance your tattoo will stretch out along with your skin. This can cause colors and lines to fade. In this case a 'touch-up' can be a solution. This also depends on the size and location of your tattoo.

The rate and speed of muscle growth will determine how much it will stretch the tattoo. If muscles are to grow steady and slow, it might not make the tattoo stretch that much, but if the muscle growth is rapid and sudden, it is more likely to make a noticeable difference in the tattoo.

As we age, our skin naturally loses elasticity. This can cause tattoos to appear more blurred or stretched out over time. Also, aging skin tends to wrinkle and sag, which can distort the image of the tattoo.