Bodybuilders in Arnold’s day rarely did any cardio, for fear of burning up muscle mass. But track athletes—especially sprinters—and wrestlers have proven for years that you can build muscle while burning fat with calorie-incinerating exercise that’s far removed from the weight room. In fact, sometimes sprinters and wrestlers can be so ripped that they can pass for bodybuilders or powerlifters (Google Alexander Karelin, three-time gold medalist in wrestling for Russia—he was jacked and cut beyond reason). What’s their secret? Their sport training is essentially high-intensity interval training (HIIT), which is nothing more than brief bouts of extreme effort followed by periods of lighter activity or rest.

For three weeks, we’re combining old-fashioned bodybuilding training—which puts muscle on like nothing else—with HIIT, which burns fat and increases endurance without risking your gains. Follow the workout modeled by Team Scivation athlete Sam Okunola. Combine it with the right supplementation, and you’ll be well on your way to a perfectly sculpted physique inside of a month.

Recovery must be a priority, as the intensity is high and frequent. For that reason, we recommend you supplement with branched-chain amino acids, citrulline malate, and electrolytes, which support muscle growth and normal muscle functions. A newcomer to the game is PeakO2, a potent compound that in a 21-day study was shown to improve power, endurance, and oxygen uptake in as few as seven days. The drastic improvements are what fueled our 21-Day Challenge.

Bodybuilders in Arnold’s day rarely did any cardio, for fear of burning up muscle mass. But track athletes—especially sprinters—and wrestlers have proven for years that you can build muscle while burning fat with calorie-incinerating exercise that’s far removed from the weight room. In fact, sometimes sprinters and wrestlers can be so ripped that they can pass for bodybuilders or powerlifters (Google Alexander Karelin, three-time gold medalist in wrestling for Russia—he was jacked and cut beyond reason). What’s their secret? Their sport training is essentially high-intensity interval training (HIIT), which is nothing more than brief bouts of extreme effort followed by periods of lighter activity or rest.

For three weeks, we’re combining old-fashioned bodybuilding training—which puts muscle on like nothing else—with HIIT, which burns fat and increases endurance without risking your gains. Follow the workout modeled by Team Scivation athlete Sam Okunola. Combine it with the right supplementation, and you’ll be well on your way to a perfectly sculpted physique inside of a month.

Recovery must be a priority, as the intensity is high and frequent. For that reason, we recommend you supplement with branched-chain amino acids, citrulline malate, and electrolytes, which support muscle growth and normal muscle functions. A newcomer to the game is PeakO2, a potent compound that in a 21-day study was shown to improve power, endurance, and oxygen uptake in as few as seven days. The drastic improvements are what fueled our 21-Day Challenge.