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If you're aiming to build muscle or improve your one-rep max in the gym, activating your fast twitch muscle fibers could be a game-changer. Your muscles are made up of both fast and slow twitch fibers. Fast twitch fibers are engaged during explosive movements, while slow twitch fibers come into play during sustained, slower actions. By adjusting your workout routine, you can target these fast twitch fibers more effectively. Keep reading to learn how your muscles work and how you can train your fast twitch fibers to perform even better!
Steps
What are fast twitch muscle fibers?
Each muscle contains a mix of fast and slow twitch fibers. There’s no muscle that consists entirely of either fast or slow twitch fibers. Inside every muscle, there are thousands of individual fibers that contract and relax to facilitate different movements. Fast twitch fibers are responsible for quick, explosive actions, while slow twitch fibers support slower, endurance-based movements.
- Fast twitch muscles are also called type 2 (or glycolytic) fibers, whereas slow twitch muscles are type 1 (or oxidative) fibers.
- Both fast and slow twitch fibers are found in skeletal muscles—the ones we typically think of when referring to muscle. These include muscles like the biceps, abs, and calves, but not the heart or the smooth muscles found in your organs.
Can fast twitch muscle fibers be developed?
Fast twitch fibers can be strengthened, but you can’t increase their number. Your genetic makeup determines how many fast twitch fibers you have in each muscle, but their size and strength depend on your workout routine. Although you can adjust your training to better target these fibers, it’s important to note that slow twitch fibers cannot be converted into fast twitch fibers, and vice versa.
- Fast twitch fibers are geared for rapid, explosive movements, which causes them to become bulkier when trained. On the other hand, slow twitch fibers are designed for endurance, leading to a leaner physique. This is why bodybuilders tend to be bulkier, while marathon runners are leaner. Both can be fit and strong, but their workouts engage different muscle fibers.
What exercises activate fast twitch fibers?
Heavy weightlifting and sprinting are the most effective ways. Essentially, the quicker your muscles fatigue, the harder your fast twitch fibers are being activated. For example, if your one-rep max on the bench press is 200 pounds (91 kg), doing 4 reps at 180 pounds (82 kg) will stimulate your fast twitch fibers much more than performing 20 reps at 80 pounds (36 kg). Similarly, sprinting full-force for 30 seconds will engage your fast twitch fibers, whereas a slow jog for 20 minutes will target your slow twitch fibers.
- Any exercise that involves lifting heavy weights or requires short bursts of energy will help strengthen your fast twitch fibers. Bicep curls, box jumps, kettlebell swings, wind sprints, deadlifts, and barbell squats are all excellent for developing these fibers.
- As a general rule, if you can only complete 7 reps or fewer at a given weight, you’re primarily working your fast twitch fibers.
How can you tell if you have fast twitch fibers?
Everyone has fast twitch fibers! Unfortunately, without undergoing a muscle biopsy, it’s impossible to determine exactly how many fast twitch fibers you have. The ratio of fast twitch to slow twitch fibers is largely determined by your genetics. But don’t let this concern you—your athletic ability and strength aren’t set in stone by your genes. Anyone can improve and develop their fast twitch fibers through the right kind of exercise.
- Generally, the bulkier you are, the more developed your fast twitch fibers are. But keep in mind, this reflects the kind of exercise you do, not a measure of health or strength. Even lean athletes with stronger slow twitch fibers can be incredibly fit and powerful.
Can you lose fast twitch muscle fibers?
They can weaken and shrink, but you can maintain them with exercise. If you live a mostly sedentary lifestyle, your fast twitch fibers will become less active over time. However, by committing to a regular workout routine that includes explosive calisthenics, short sprints, and resistance training, you can revitalize those fibers!
- It’s natural to lose muscle fibers as you age, but strength training 2-3 times a week can help preserve your fast twitch fibers, even as you grow older.
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Different muscles have different roles, which means some muscles naturally contain more fast twitch or slow twitch fibers. For example, your soleus muscle in the lower leg is primarily responsible for maintaining posture and sitting, activities that require endurance rather than speed. Consequently, it doesn’t have a large number of fast twitch fibers. However, this doesn’t impact your exercise regimen in any significant way.
