The info below is complied from a couple of articles on http://www.abcbodybuilding.com/ . It lists average muscle fibre compositions and I think might be a useful guide for designing routines to maximise hypertrophy by varying the set/rep schemes per bodypart according to muscle specific fiber variations.
Below the list is a part of an article suggesting how to go about such a approach. The full articles and list of fiber ratios can be found in the physiology section of the site above. Enjoy, fellow hypertrophy/physiology nerds!
Fiber types are shown as percentages with slow twitch before the slash and fast twitch after - eg, 42.3/57.7 = 42% slow twitch type I fibers and 57.7% type IIa and type IIb/IIx combined. In some cases, where either slow or fast fiber ratios are overwhelmingly dominant, no percentage is given just the dominant catagory of fiber.
Chest
Pectoralis major (clavicular head) 42.3/57.7
Pectoralis major (sternal head) 43.1/56.9
Back
Latissimus dorsi 50.5/49.5
Infraspinatus 45.3/54.7
Teres major & teres minor: slow twitch dominant
Trapezius: 53.7/46.2
Neck & shoulders
Sternocleidomastoid: 35.2/64.8
Deltoid – all heads, surface muscle: 53.3/46.7
Deltoid – all heads, deep muscle: 61/39
Upper arms
Triceps – all heads: 32.5/67.5
Biceps – both heads, surface muscle: 42.3/57.7
Biceps – both heads, deep muscle: 50.5/49.5
Brachioradialis: 39.8/60.2
Forearms
Flexor carpi ulnaris, extensor pollicius brevis, extensor carpi ulnaris, extensor digitorum, extensor carpi radialis brevis, palmaris longus, felxor carpi radialis, abductor pollicius longus: all slow twitch dominant
Thighs
Rectus femoris: 35.4/65.6
Vastus medialis – internus, surface muscle: 43.7/56.3
Vastus medialis – internus, deep muscle: 61.5/38.5
Vastus lateralis – externus, surface muscle:37.8/62.2
Vastus lateralis – internus, deep muscle: 46.9/53.1
Biceps femoris – both heads: fast twitch dominant
Gluteus maximus: 52.4/47.6
Gluteus medius: slow
Semitendinosus, semimembranosus: fast twitch dominant
Illacus: 49.6/50.4
Psoas: 49.2/50.8
Pectineus: slow twitch dominant
Adductor longus: 58/42
Adductor magnus: 58/42
Gracilis: fast twitch dominant
Lower legs
Gastrocnemius – medial head: 51/49
Gastrocnemius- lateral head: 46.5/53.5
Soleus: 89/11
Flexor digitorum longus: slow twitch dominant
Peroneus longus: 62.5/37.5
Tibialis anterior: 73.4/26.6
Abdominals
Rectus abdominus: 46.1/53.9
External oblique: fast twitch dominant
Serratus: 46.9/53.1
Various Training Methodologies Between Various Regions of The Body
Knowing how to stimulate hypertrophy in type I, IIA and IIB fibers is half the battle. The other half is understanding how to apply these concepts to each individual body part. An understanding of the fact that each muscle group is made up of specific fiber compositions will augment this process. For example, if a muscle is 86 percent fast twitch, working the slow twitch fibers to a heightened extent would undermine the participants training efficiency. Further, if a muscle is predominantly slow twitch and the participant ignores this make up, then hypertrophy will be hindered. The following will provide a guide on how to target various musculature:
1. Always hit the fast twitch cells, even if the muscle group is pre-dominantly slow twitch. The reason is due to the relatively larger size of this particular fiber. What will not occur is an overly dominant fast twitch workout.
2. If a muscle group is dominated by a slow twitch makeup, the participant will need to dedicate significant time to stimulating growth in these cells. A recommendation would include a few medium range sets to target the small percentage of fast twitch fibers, followed by a regimen, which blasts the higher percentage cells to bits for the majority of the workout by using a higher repetition scheme.
3. If a muscle group has an even makeup, the majority of time should be spent working the fast twitch fibers due to their size. However, time should still be delineated to the slow twitch fibers. You should switch around the ratios as well. Let’s say a muscle group is 50 / 50. Then spend 60-70 percent of the time on fast twitch with the remainder of time on the remaining fibres. Occasionally for a burst of growth, emphasize the type I cells 50-80 percent of the time. This should be used sparingly, but certainly of prime importance.
4. If a muscle group such as the hamstrings are dominantly fast twitch (70-80 percent) then spend about 80-90 percent of the time on fast twitch fibers, and 10-20 percent of the time on the slower fibers. Perhaps just one burn out / high repetition set at the end of the workout.
Jacob Wilson BSc/MSc
Rep ranges and muscle fiber hypertrophy potential and associated strength gain potential
Repetition Range / Type I / Type IIA / Type IIB / Strength Gains
1-2 repetitions / Very Low / Low / Low / Excellent
3-5 repetitions / Very Low / Low / Decent to Good / Excellent
6-8 repetitions / Very Low / Good / Excellent / Good
9-12 repetitions / Low / Excellent / Very Good / Good
13-15 repetitions / Decent / Very Good / Decent to Good / Endurance
16-25 repetitions / Very Good / Diminishing / Low / Endurance
25-50 repetitions / Excellent / Low / Very Low / Endurance
as I know of one you can do in the gym, one you can do any where with space to jump and a friend and then the biopsy oach!