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Are the Hamstrings Really Primarily Fast-Twitch?

By September 25, 2014January 2nd, 2017Hamstrings, Sports Science Topics

For the past 20 years or so, I’ve been reading strength & conditioning articles claiming that the hamstrings are primarily composed of fast-twitch fibers. I can recall repeating this same information to lifting partners way back in the day. In ten minutes, with a quick Google search, I found articles from plenty of well respected individuals in the strength training community claiming that hamstrings are mostly fast-twitch (hundreds of other articles claiming the same exist, but I chose to link authors or sites I’m familiar with), including:

Bret Contreras

12 Hamstrings Exercises for Hardasses

Charles Poliquin (and Staff)

Hamstrings Times Two

Ten Ways to Prevent Hamstring Pulls

Hamstring Paradigm

Fast Track to Bulging Hamstrings

Technique Tips for Powerful Hamstrings

The Structural Balance Factor

Improving Your Glute Ham Raise

Vern Gambetta

Hamstring Injuries: A Problem With a Clear Solution

Men’s Fitness

Romanian Deadlifts: Unlock Your Leg Muscles

Muscle & Fitness

Muscle in Minutes: Legs

Iron Mag

Body Conquest: Troubleshooting Q&A

Josh Bryant

Workout of the Week: Build Strength and Size in Your Legs

John Davies

Hamstring Development for Athletes

Christian Thibaudeau

The Lost Art of Hamstring Training

Kelly Baggett

How to Create a Speed Machine Using the Weight Room

Rob King

6 Tips to Better Hamstrings

Lee Boyce

Three Ways You’re Messing Up Your Romanian Deadlifts

Menno Henselmans

Muscle Specific Hypertrophy: Biceps, Back, and Lower Body

This claim even went unquestioned in a peer-reviewed journal article: see HERE.

But are they really? Where did this claim first come from? Did the originator of this claim just read one study, or did he examine the entire body of evidence? Did we all just follow the leader and repeat his claims without doing our due diligence? I know I did. 


Today my colleague Chris Beardsley summarized the research on muscle fiber types. Click below to access the article:

What is the fiber type of different muscle groups?

As you’ll see, there are six studies that have examined the fiber type composition of the hamstrings. You can click on the link to explore these studies, but one study shows 67% fast twitch composition, while the other five show 55%, 51%, 50%, 44-54%, and 43%. Based on this data, at this point in time we cannot say that the hamstrings are primarily fast twitch. They appear to be an even mix between fast and slow twitch.

I’ve yet to see any studies exploring the hamstring and gluteal fiber type composition in sprinters; it is quite possible that they could have higher percentages than typical individuals, and maybe this is what helps give them an edge. However, this is yet to be examined.

bodybuildersSo what does this mean? Should our training be different if we want to maximize hamstring development? Maybe. While there are plenty of great hamstrings exercises, including deadlift variations, back extensions, good mornings, glute ham raises, reverse hypers, and kettlebell swings, let’s consider what bodybuilders do for their hamstring development.

Bodybuilders have the biggest hamstrings out of all athletes, and they will typically perform 3-4 sets of 3-4 different hamstring exercises. Usually one is a hip extension exercise that stretches the hamstrings such as a stiff legged deadlift, and 2-3 of them are different types of leg curls (lying, seated, standing one leg). They typically perform their leg curl variations for medium to high reps (8-15) with around a minute in between sets. This equates to somewhere between 72 and 240 reps of knee flexion exercise (probably around 120 reps is reasonable).

This added volume has to add up and make a difference. Leg curls activate the lower hamstrings to a greater degree than deadlifts, they induce high levels of metabolic stress, and they don’t beat up the CNS like deadlifts do. As an industry, we were wrong about the fast twitch predominance, and our training recommendations were suboptimal for lifters seeking hamstring hypertrophy. Now, there is evidence that sprinters’ hamstrings contract faster than those of sedentary individuals, perhaps due to fiber type shifting, so sprinters need to go heavy and be explosive in their training. But if you’re seeking gains in hamstring muscularity, don’t be afraid to perform high volume leg curl workouts. Just make sure you’re performing a hip extension movement too (deadlifts are always a good choice).


  • Peter says:


    interesting article, but as I know the slow twitch – fast twitch ratio depends on genetics and other factors.
    Why is it important to determine an accurate ratio, when it is different in every person?


  • Mark says:

    On the contrary, I’ve been under the impression that the hamstrings are primarily slow-twitch, based on the 1973 study Data on the Distribution of Fibre Types in 36 Human Muscles. All six male subjects had a majority of slow twitch fibres in the biceps femoris, ranging from 54 to 80 percent. I’m not sure if that study is still relevant but it did lead me to believe that a bit of additional higher rep training for the hamstrings wouldn’t hurt.

  • Mark says:

    I just made the connection that the study I referenced is the first listed in Chris’s review. I’m surprised to see that it’s such a dramatic outlier.

  • Steve says:

    Another Poliquin myth busted….thanks Bret

  • Andrew Dixon says:

    I’m experimenting with this lately and I’m finding it best to do 2 hip hinges and 2-3 knee flex. Deadlifts are great, but the offer no resistance in the extended/shortened position. So including some 45 or 99 degree hip/back extensions can help hit the full spectrum of the strength curve.

  • Maurizio Paolini says:

    I remember my first mentor Filippo Massaroni ( Phd in Articular Biomechanics and former NABBA Mr Universe ) told me that the question of muscle fibers make-up is a genetic thing so bodybuilders dont really have to change their rep range on the basis of what fast twitch percentage they have…..but this was 25 years ago…..:-)

  • Dave Johnston says:

    Interesting post Bret. As I work in a rehab setting, the majority of people I see (especially those with lower back pain) have ‘hyperactive’ & short hammies in conjunction with gluteal amnesia & atrophy. It makes sense to me that in a dysfunctional population the fibre distribution would be predominately slow twitch. Do you know if any research has been conducted on a clinical population in this respect? Cheers!

  • Annabelle says:

    Hi Brett, love your blog. You’re one of the smartest trainer out there. I have a question for you:

    I’m a female hockey players and I’d like to get more developement for my hamstrings and glutes. Which exercises should I do ? I’m lucky since I can contract my glutes very easily but my hamstrings are lacking since I can’t seem to ”feel” them when I’m trying to work them.

    I can already go pretty heavy on my barbell deadlift (my bodyweight). So how can I target my hamstrings more agressively (swings, other type of deadlifts, seated curls ……????)

    Thank you

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