Boxing (and kickboxing) are among the most cardiovascularly intensive sports in which one can participate. Have you ever seen a fat boxer? Kidding. Of course you have. But they are a rarity, as even the most rudimentary training for the sport focuses on endurance and consequently, muscle toning. A full boxing regimen includes strength training, various bag and pad training, and enough cardio to leave all but the fittest men gasping for air.