EMG Placement Tutorial

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A tutorial to

EMG placement on the lower

extremity muscles

Moein Nazifi

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1. Introduction

In this article, a basic method for EMG placement will be provided. Since our targets in the synergy

studies are the lower extremity muscles which play a major role in gait, this article only aimed a

limited number of leg muscles. These muscles are the tibialis anterior (TA), soleus (SL), medial

gastrocnemius (MG), vastus medialis (VM), rectus femoris (RF), medial hamstrings (MH), lateral

hamstrings (LH) and gluteus medius (GM).

Along the same line, a brief introduction to each muscle will be provided and then the

recommendations for EMG electrode placement and the necessary landmarks on the body will be

provided. At last, a clinical test will be introduced. This test is of importance since it mainly

activates the target muscle and one can easily check the EMG activation levels to double check

the correctness of the EMG placement.

Figure 1 Target muscles in this study with their approximate place

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2. EMG placement 2.1. Tibialis anterior

This muscle is responsible for dorsiflexion of the ankle joint and assistance in inversion of the foot. Fig.2

shows its location within the body.

Recommended sensor placement procedure

Starting

posture

Supine or sitting.

Electrode size Maximum size in the direction of the muscle fibers: 10 mm.

Electrode

distance

20 mm.

- location The electrodes need to be placed at 1/3 on the line between the tip of the

fibula and the tip of the medial malleolus.

- orientation In the direction of the line between the tip of the fibula* and the tip of the

medial malleolus**.

- fixation on

the skin

(Double sided) tape / rings or elastic band.

Figure 2 Location of tibialis anterior

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- reference

electrode

On / around the ankle or the proc. spin. of C7.

Clinical test Support the leg just above the ankle joint with the ankle joint in dorsiflexion

and the foot in inversion without extension of the great toe. Apply pressure

against the medial side, dorsal surface of the foot in the direction of plantar

flexion of the ankle joint and eversion of the foot.

*The fibula or calf bone is a leg bone located on the lateral side of the tibia, with which it is connected above and

below. It is the smaller of the two bones in the shank.

Figure 3 Location of EMG electrode (yellow cross) and the tip of the fibula (blue circle)

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** Malleolus is the bony prominence on each side of the ankle. The medial malleolus is the prominence on the inner

side of the ankle.

Figure 4 Fibula bone

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2.2. Soleus

The action of the calf muscles, including the soleus, is plantar flexion of the foot. They are

powerful muscles and are vital in walking, running, and dancing. The soleus specifically plays an

important role in maintaining standing posture; if not for its constant pull, the body would fall

forward. Fig. 5 show its place in the body.

Figure 5 Soleus muscle.

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Starting

posture

Sitting with the knee approximately 90 degrees flexed and the heel / foot of

the investigated leg on the floor.

Electrode size Maximum size in the direction of muscle fibers: 10 mm.

Electrode

distance

20 mm.

- location The electrodes need to be placed at 2/3 of the line between the medial condyle

of the femur* to the medial malleolus.

- orientation In the direction of the line between the medial condyle to the medial

malleolus.

- fixation on

the skin


- reference

electrode


Clinical test Put a hand on the knee and keep / push the knee downward while asking the

subject / patient to lift the heel from the floor.

Figure 6 Location of medial malleolus (lower blue circle), medial

condyle of the femur (upper blue circle), and EMG location (yellow

cross)

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* The medial condyle is one of the two projections on the lower extremity of femur (the bone in the thigh), the other being the lateral condyle.

Figure 7 Position of the condyle in the knee

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2.3. Medial gastrocnemius

Gastrocnemius is a very powerful superficial muscle that is in the back part of the lower leg. It

runs from its two heads just above the knee to the heel. The gastrocnemius is primarily involved

in running, jumping and other "fast" movements of leg. Its function is plantar flexing the foot at

the ankle joint and flexing the leg at the knee joint.


Starting

posture

Lying on the belly with the face down, the knee extended and the foot

projecting over the end of the table.


Electrode

distance

20 mm.

- location Electrodes need to be placed on the most prominent bulge of the muscle.

- orientation In the direction of the leg (see picture).

Figure 8 Gastrocnemius muscle

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- fixation on

the skin


- reference

electrode


Clinical test Plantar flexion of the foot with emphasis on pulling the heel upward more

than pushing the forefoot downward. For maximum pressure in this position it

is necessary to apply pressure against the forefoot as well as against the

calcaneus.

Figure 9 EMG location for the medial

gastrocnemius

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2.4. Vastus medialis

The vastus medialis is a muscle located medially in the thigh that extends the knee. The vastus

medialis is part of the quadriceps muscle.


Starting

posture

Sitting on a table with the knees in slight flexion and the upper body slightly

bend backward.


Electrode

distance

20 mm.

- location Electrodes need to be placed at 80% on the line between the anterior superior

iliac spine and the joint space in front of the anterior border of the medial

ligament.

- orientation Almost perpendicular to the line between the anterior superior iliac spine*

and the joint space in front of the anterior border of the medial ligament**.

- fixation on

the skin


- reference

electrode


Clinical test Extend the knee without rotating the thigh while applying pressure against the

leg above the ankle in the direction of flexion.

*The anterior superior iliac spine refers to the anterior extremity of the iliac crest of the pelvis.

Figure 10 Anterior superior iliac spine labeled second to bottom

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**The medial collateral ligament is one of the four major ligaments of the knee. It is on the medial (inner) side of

the knee joint.

Figure 11 Right knee, bones and ligaments

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Figure 12 EMG placement for the vastus medialis

Figure 13 the vastus medialis, rectus

femoris, and the vastus lateralis (from

right to left, respectively)

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2.5. Rectus femoris

The rectus femoris is situated in the middle of the front of the thigh. Its function is extension of

the knee joint and flexion of the hip joint. Refer to Fig.13.


Starting

posture

Sitting on a table with the knees in slight flexion and the upper body slightly

bend backward.


Electrode

distance

20 mm.

- location The electrodes need to be placed at 50% on the line from the anterior superior

iliac spine to the superior part of the patella*

- orientation In the direction of the line from the anterior superior iliac spine to the superior

part of the patella.

- fixation on

the skin


- reference

electrode


Clinical test Extend the knee without rotating the thigh while applying pressure against the

leg above the ankle in the direction of flexion.

* The patella also known as the kneecap or kneepan, is a thick, circular-triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. Refer to Fig.11.

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Figure 14 EMG placement for rectus femoris

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2.6. Medial hamstrings

This muscle is responsible for flexion and medial rotation of the knee joint. It also extends and assists

in medial rotation of the hip joint.


Starting

posture

Lying on the belly with the face down and the thigh held down on the table, in

medial rotation, and the leg medially rotated with respect to the thigh. The

knee needs to be flexed to less than 90 degrees.


Electrode

distance

20 mm.

- location Electrodes need to be placed at 50% on the line between the tuberosity of the

ischium and the medial condyle of the tibia.

- orientation In the direction of the line between the tuberosity of the ischium* and the

medial condyle of the tibia**.

- fixation on

the skin


- reference

electrode


Clinical test Press against the leg proximal to the ankle in the direction of knee extension.

*The tuberosity of the ischium marks the lateral boundary of the pelvic outlet.

** The condyle is the portion of the upper extremity of tibia. Fig.11.

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Figure 15 The tuberosity of the ischium

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Figure 17 EMG placement for medial hamstring

Figure 16 Lateral and medial

hamstring (right to left, respectively) in

posterior view

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2.7. Lateral hamstrings

This muscle is responsible for flexion and lateral rotation of the knee joint. The long head also extends

and assists in lateral rotation of the hip joint. Refer to Fig.16.


Starting

posture

Lying on the belly with the face down with the thigh down on the table and

the knees flexed (to less than 90 degrees) with the thigh in slight lateral

rotation and the leg in slight lateral rotation with respect to the thigh.


Electrode

distance

20 mm.

Electrode

placement

- location The electrodes need to be placed at 50% on the line between the tuberosity of

the ischium and the lateral condyle of the tibia.

- orientation In the direction of the line between the tuberosity of the ischium and the

lateral condyle of the tibia.

- fixation on

the skin


- reference

electrode


Clinical test Press against the leg proximal to the ankle in the direction of knee extension.

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Figure 18 EMG placement for lateral hamstring

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2.8. Gluteus medius

This muscle abduction of the hip joint. The anterior fibers medially rotate and may assist in flexion of

the hip joint; the posterior fibers laterally rotate and may assist in extension.


Starting

posture

Lying on the side on a table.


Electrode

distance

20 mm.

Electrode

placement

- location Electrodes need to be placed at 50% on the line from the iliac crest* to the

trochanter**.

- orientation In the direction of the line from the iliac crest to the trochanter.

- fixation on

the skin


- reference

electrode

On the proc. spin. of C7 or on / around the wrist or on / around the ankle.

Figure 19 Gluteus medius

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Clinical test Lying on the side with the legs spread against manual resistance (holding the

ankles)

* Iliac crest is the superior border of the wing of ilium and the superolateral margin of the greater pelvis.

** The trochanter is an anatomical part of the femur connecting to the hip bone.

Figure 21 The head of trochanter shown

Figure 20 Iliac crest

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Figure 22 EMG placement for gluteus medius

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3. References 1. Neptune R., et al, Modular control of human walking: A simulation study, Journal of

biomechanics, Vol 42, 1282-1287, 2009.

2. http://seniam.org/

3. https://www.wikipedia.org/

EMG Placement Tutorial

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