Cheapest priced copy (Odyssey): $0.35 at Card Kingdom, near mint, their price list as of .
Muscle Burst 
Instant · Common · Odyssey · #252
Target creature gets +X/+X until end of turn, where X is 3 plus the number of cards named Muscle Burst in all graveyards.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern