You can’t know for sure who is currently using Performance Enhancing Drugs (PEDs), or who has used them in the recent or distant past. This is because there are different types of PEDs, different frequency of use, different body types, and different sports or workouts to go with them. Some people take them once in their life, and they reap the benefits of enhanced performance for decades to come; and they call themselves “natural”, when they are really not.
However, there are signs that someone is using or has used performance enhancing drugs:
Trapezius muscle disproportionally bigger than any other muscle group. Traps have a larger concentration of androgen receptors, so they grow disproportionally faster with PEDs.
Acme on the back, and acme in general that should not be natural in adults.
Bloated belly, even when having very low body fat percentage.
Very fast progressions in strength, mass and performance.
Receding hairline in women.
Deep distorted voice in women, high-pitched voice in men.
Disproportionally big hands, ears and nose are tell-tale signs of growth hormone use.
Erratic aggressive behavior while on a PED cycle, and weakness/docility while off the cycle.
Ability to work out in high intensity and volume without rest periods. PEDs shorten recovery periods, so it’s possible to put in more work without overtraining. This is the main advantage of PEDs.
Gynecomastia in men, despite being lean everywhere else.
Breast atrophy in women.
Unnatural hair growth in women (on belly, chest, arms and face).
Menstrual irregularities or complete inability to menstruate in women.
Erectile dysfunction in men during off periods. Unnaturally high sex drive during on periods, for both sexes.
Enlarged clitoris in women. Shrinking of testicles in men.
There is also synthetic oil (synthol) or injectable silicone with which some people inject their muscles to make them seem larger. You can tell this fake pump when the apparent “muscle” is exaggerated, disproportional, and completely out of place, like a Picasso painting. The muscle doesn’t seem to behave like it’s flexing or relaxing, or changing its shape according to body movement; it’s just a lifeless mass.
