Muscle Fiber Types
- support16578
- May 16
- 5 min read
The Upper Body is mostly composed of fast twitch fibers or white fibers (Type IIB). These respond to low reps/high weight. The most extreme example of this is the triceps which are 67% white fiber. The chest is close to 60% and the Lats are about 50%. Delts being a support muscle are more closely 45% white fibers.
Since the white fibers are strength and size fibers, using more weight or using a weight with more force (faster) results in these fibers swelling and the muscle becoming bigger. So using more weight and doing partial reps in the middle 50% of your range of motion is ideal for many upper body muscles, particularly pressing. This is because the middle 50% of the range of motion is the strongest portion and if you stick to this portion you can use more weight.
Thus if you're a woman or a ‘man’ who doesn't want bigger muscles you could train outside this rep range, using lighter weight for more reps...like a girl ‘toning’. Basically ‘toning’ is just repping out with light weights ineffectively so you're burning fat with your weights but not stimulating anything to grow. Like Crossfit.
Type I - Red
The lower body muscles have more red fibers or slow twitch muscle fibers (Type I). These fibers only get worked with high reps and the “burn”. Likewise since these fibers are not strength fibers and don't respond to heavy ass weight like the upper body muscles do for lower body your better off with a reasonable range of motion for the muscles you're trying to work. If you're just targeting quads a front squat to parallel is great, if it's glutes and hams it better be a back squat with a duck stance and LOW AS FUCK.
The glutes like the back are a pretty even split of white and red fibers, with the hamstrings mostly white fiber and quads being complex; some heads are more red than others. The calves are almost all red fibers. The gastroc is more white than the soleus but it’s 60% and like 85% red fibers respectively.
So How Many Reps Should I Do To Grow?
Assuming that the back is the middle of the road at 50% white fiber/ 50% red fibers then whatever number of reps are perfect for the back are the midline for other body parts.
Simply: if 50% is 10-12 reps then every 5% up or down from that is 2 reps:
Body Part | % of fibers that are white | # of Reps for optimal growth |
Lats | 50 | 10-12 |
Hamstrings | 55 | 8-10 |
Glutes | 50 | 10-12 |
Quads | 50 (Rectus femoris is 60%) | 8-15 |
Soleus | 15 | 20+ |
Gastroc | 50 | 10-12 |
Pecs | 60 | 6-8 |
Triceps | 65 | 4-6 |
Biceps | 55 | 8-10 |
Delts | 45 | 12-15 |
Here is the reference for the most complete analysis of fiber types per body part
Information like this can be very helpful. For instance since the rectus femoris is clearly more white than the other quad muscles, big compound lifts could be done 8-10 reps, which is great for hamstrings, glutes and rectus femoris, then do leg extensions for the other 3 quadriceps heads with 12-15 reps.
Likewise close grip bench which is more triceps than flat could be done with a decline to allow even more weight to be used for reps of 6, getting both chest and triceps perfect, but for incline bench you would want to use less weight since the delts are your main limiting muscle and is way more red fibers thus increasing the reps to 12-15.
Thus 2 great supersets would be squats heavy, leg extensions light, then 6-8 reps close grip decline superset with military press 12-15 reps. Both will hit the quads and triceps with low and high reps but are optimally geared for the fiber types of all the other muscles involved.
It also seems that since all the posterior chain are of like % that a range of 8-12 reps is perfect for deadlifts. In fact, no lower body compound NEEDS to be done for more than 12 reps. Only calves and quad extensions are 15+ reps. For upper body the range is lower for pressing than extensions and pulling, so pressing is 4-8 and pulling is 10-12 with the exception of overhead pressing which has to be lighter the more incline the angle provides as it recruits more delts and thus is weaker.
Fiber Type Specific Workout
Hit lower, upper, rest, lower, upper, rest for 12 iterations or 36 days
As usual all sets to failure, if you can get even one more rep your set doesn't count. So if you fail at 12 on set 1 you're probably don't need to increase the weight to fail at 10 reps on set 2, that would happen normally if you're really failing on the 12 rep set. The Lee Haney and Dorian Yates method is to not take any set to failure until the last set, then the last set is BEYOND failure. This isn’t that, these are straight sets to failure. In many of the exercises the first set is clearly too many reps for that body part. That's a warm up set. Warm up sets are not to failure. But you don't count them as real sets either.
Lower Body
Stairs 10 minutes at 65% maximum heart rate.
Seated Calves
4 x (10,10,10,10) triple drop sets
Drink half of your Half-time
Lying Leg Curl
12, 10, 8, 8
Pointing toes until failure, then curling them to finish the set. Use stripping method or rest pause to finish the set if you fail prematurely.
Straight Leg Deads with Dumbbells
12, 10, 8, 8
This is important to get the stretch and of course, perfect spinal alignment.
Leg Press
20, 15, 12, 10, 8
Deep! But don't let your butt roll up.
Hack Squat
12, 10, 8
Keep heels down.
Squat
12, 10, 8
Below parallel or just quit, there is no room in this world for shallow squatters. Whine about your “knee pain” to someone who has a box of tampons for you, I don't want to hear it.
Drink the rest of your Half-Time
Lunges
12 steps per leg
Long strides, drive through the heel.
Leg Extensions FST-7
7 x 12-15 reps 30 second rest
Squeeze every reps at the top for 2 seconds.
5 minutes bike to wash acid out of your legs
Upper Body
10 minutes stairs to warm up.
Bent Rows
SS
Rack Pulls
10, 8, 7, 6
Use the same weight or the rack pulls as the bent rows, just complete the set with the second exercise. Since its a super set the total reps with the weight is 20 the first set; 10 with bent row and 10 with rack pulls. This is a warm up. The final set has to be to failure and its 6 and 6 reps for 12 reps.
Pull Ups
SS
Behind The Neck Press
4 x 12
Upright Rows
SS
Shrugs
12,10, 8, 8
Incline DB Bench
SS
Pec Deck
10, 8, 6, 6
Decline Close Grip Bench
SS
Tricep Pressdown
10, 8, 6, 4 SS with 12-15 reps on press downs
Lateral raise
SS
Arnold press
10, 8, 6
You shouldn't have to change weights, use rest pause to get all your reps in
BB Curl
12, 10, 8, 8
Hammer Curl
10, 8, 8, 8
Disclaimer
Nothing in this article or on this site should be considered medical advice or as an endorsement to violate any law of the country in which you reside. The information given is for fun and entertainment purposes only. All claims are 100% dependent upon proper diet and exercise. Please consult a medical practitioner prior to any diet and exercise program.
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