Muscle hypertrophy: hamstrings

MrRippedZilla

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A couple of pieces of training data for today, just the sort of mood I'm in :)


Changes in the medial-lateral hamstring activation ratio with foot rotation during lower limb exercise

https://www.ncbi.nlm.nih.gov/pubmed/18331800 (pm me for the full paper)

Abstract
This paper investigated whether the ratio of medial-lateral hamstring muscular activation could be altered with changes in foot rotation position (both internal and external rotation) during three standard lower limb exercises.
It has been suggested that those with medial compartment knee OA activate the lateral hamstrings more than the medial to help unload the diseased compartment; therefore, preferential activation of this muscle during lower limb exercise may help to further decrease the stresses on the articular cartilage and be an effective intervention for knee OA and lateral hamstring injury.
Thirteen healthy young adult subjects were tested and average medial and lateral hamstring EMG data during the full exercise, as well as the concentric and eccentric phases, were used to calculate the medial-lateral (M-L) hamstring activation ratio for each exercise and foot position.
Results suggest that internal foot rotation increases the M-L hamstring activation ratio while external foot rotation decreases this ratio. Therefore, altering the position of the foot during standard lower limb exercise can help selectively activate the medial or lateral hamstring muscle groups. This selective activation may have implication in treating symptoms of knee osteoarthritis and hamstring injury; but, longitudinal intervention studies would be needed to determine clinical utility.


What they did...

They took 13 individuals (6 men, 7 women) and had the perform 3 movements - lying leg curl, 1 leg glute bridge and 1 legged deadlifts.

During all 3 movements they experimented with foot rotation (straight, external, internal) to see if it had an impact on what part of the hamstring was more/less activated. They were looking at the medial (middle) and lateral (side) portions of the hamstrings specifically.

Electromyography (EMG) was used to assess the level of muscle activation. EMG data has its own issues that I won't go into here but suffice to say that the numbers should be interpreted with caution and not be seen as a universal, guaranteed, thing.


What they found...

Feet straight = insignificantly favoring the lateral hamstrings on leg curls & glute bridges while significantly favoring medial hamstrings on deadlifts.
Feet turned out = significantly favors lateral hamstrings for all 3 movements.
Feet turned in = significantly favors medial hamstrings for all 3 movements.

For single leg DLs in particular, unless you actively externally rotate, its pretty clear that the focus will be on the medial hamstrings.


Take home points

Something as simple as foot positioning can influence what part of a specific muscle group is activated - something the advanced bodybuilders should probably be aware of.

To gain more mass on your lateral hams, focus on external rotation for most movements while keeping an eye on exercise selection (DL variations are probably not going to be enough).
To gain more mass on your medial (middle-ish) hams, focus on internal rotation and DL variations should probably be your main focus.
 
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MrRippedZilla

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Can you do one on calves? Asking for a friend...

I've written like 4 variations IIRC of calf articles for a bunch of different people so its not exactly a foreign concept to me.

Short answer: if your...friend...has small ankles and high calf insertions, he's ****ed. They will never, ever, look big enough to him.
 

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