Even if he tested clean from now till the fight date, he's already reaped the benefits of it. It would aide in increase aerobic capacity, increased endurance, increased stress tolerance, burned fat (weight reduction), increased mass and skeletal muscle through the early part of camp. Many of which can be mostly maintained/preserved through natural training till the fight. which is why people don't juice during fights anymore, they juice in camp and then cycle off so they can test clean for the fight. Half or 3/4 of the performance enhancement is better than none.
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