A motor neuron is a neuron that terminates in a muscle fiber. Because of the properties of excitation and excitation-contraction coupling, a neural signal can be sent from the brain and converted to an electrical potential. These steps include: (1) signal arrives in motor end-plate, (2) Ach (acetylcholine) is released into the synaptic cleft, (3) Ach binds to receptors on the sarcolemma, (4) Ligand-regulated ion gates open and create an end-plate potential. From this action potential, a voltage is perpetuated down the t-tubules, causing the release of Ca2+ ions and subsequent contraction of the muscle fiber(s) (Saladin). The amount of electrical activity in a muscle is directly proportional to the strength of that muscle. The Electromyogram (EMG) measures the amount of electrical signal running through a muscle and therefore can provide data for the activity of the muscle.
Muscle Activation Technique (MAT) is a type of therapy based on the physiology and biomechanics of muscle contraction:
When looking at the physiology of a muscle contraction, as the muscle (extrafusal fibers) is placed under a stretch, the muscle spindle (intrafusal fibers) sense tension as they are also placed under a stretch. The sensory receptors that encompass the intrafusal fibers send information back to the CNS, stimulating the alpha motor neurons, which in turn, send feedback back to the muscle telling it to contract in order to resist the tension. This is a normal response to a muscle when placed on a stretch. In comparison, if the extrafusal fibers of a muscle shorten due to contraction, the muscle spindle or intrafusal fiber would also shorten and be placed on a slack. This in turn would make the muscle incapable of regulating the load being placed on the muscle (Roskopf).
When a muscle is injured or traumatized in some way, there is negative feedback from the nervous system (neurologically and biomechanically). This causes a reduced capability for the muscle to contract as it moves into the shortened position. When muscle tightness is expressed, the underlying cause is muscle weakness (Roskopf). The MAT therapist will first diagnose a weakness through isometric exercises based on the action of the given muscle. If that muscle performs poorly, there are two options for treatment. The first is a manual therapy that involves pressing on the origin(s) and insertion(s) of the muscle. The second type of treatment is by isometric exercises. Once treated, the MAT therapist re-tests the muscle with the same, initial test to see if proprioceptive input to the muscle is restored. I will be testing the electrical component of these techniques. My hypothesis is that the EMG will show greater muscle activity on the same muscle after manual treatment and isometric exercises.
Brad Carlson (certified MAT therapist) and Dana Lyon (world class athlete in the Javelin) made this lab possible. Eight weeks ago, Dana had knee surgery on her left knee. Because of this surgery, it was probable that the Rectus Femoris would be weaker on her left leg. The Rectus Femoris is a great muscle to test because it is large and superficial. With these two traits, I can confidently say “noise” from other muscles was minimal. After the EMG equipment and LabScribe 2 was set up, I connected the electrodes to the Rectus Femoris on both legs. The green electrode was grounded on her Patella, while the red and black electrodes were attached to the bulk of the Rectus Femoris (about mid and top thigh). The initial test showed a base-line muscle activity for her left (injured leg) Rectus Femoris. During the test, her left leg proceeded to muscle failure, so Brad proceeded to manually treat the left Rectus Femoris by pressing on the origin (Anterior Inferior Iliac Spine) and insertions (Patella and Tibial Tuberosity). We tested the left Rectus Femoris after treatment and found an increase in electrical activity and a visible increase in strength as the muscle did not fail. Next, we tested muscle activity after active-stretching (flexing the opposite muscle causing the Rectus Femoris to extend) and passive stretching (forcibly extending the Rectus Femoris). The passive stretch test showed a decrease in muscle activity on the EMG and proceeded to failure. Brad manually treated it in the same manner as before and we retested the muscle after treatment. Next, we tested the muscle prior to (in a traumatized state) and after isometric exercises. Lying on her back, Dana flexed her hip to 90º, pressed her hand against her knee and resisted six times, holding for six seconds each time. We retested the muscle after this isometric exercise.
The data from each of these tests is quite fascinating. As displayed in Table 1, the greatest muscle activity was during the initial, manual post-treatment, post-active stretch and second, manual post-treatment after the passive stretch. This absolute area average was 0.321u. The weakest muscle activity was recorded during the initial, pre-treatment test, post-passive stretch and pre-isometric tests. Their average absolute area was 0.76u. The percent change for muscle activity after the manual therapy was 275.38% increase (Figure 1). The percent change after isometric treatment was an astounding 609.90% increase in muscle activity (Figure 2). The greatest muscle activity max (2.161) was recorded in the same Rectus Femoris after treatment showing that greatest muscle activity can be achieved through this treatment. In terms of muscle activity, active stretching was more beneficial than not stretching and exponentially more beneficial than passive stretching. After Brad treated the passively stretched muscle, it showed a recovered state of activity.
With regards to stretching, active stretching recorded the second greatest EMG activity and isolated max. By utilizing dynamic (or active) stretching, the integrity of the muscle’s ability to contract is preserved. Passive (or static) stretching recorded the second lowest EMG activity and isolated max—only second to the initial pre-treatment test.
Rectus Femoris Muscle Activity in Order of Procedure
Rectus Femoris T2-T1 (s) Absolute Area (du/dt) Max (u) Mean (u)
Pre-treatment 1.750 0.668 1.515 0.011
Post-treatment 1.752 0.831 1.755 0.011
Post- active stretch 1.752 0.784 2.203 0.020
Post- passive stretch 1.752 0.195 1.610 0.005
Post-treatment 1.751 0.732 2.158 0.004
Pre- isometrics 1.751 0.101 1.862 0.006
Post- isometrics 1.752 0.717 2.228 0.008
Through the data achieved from this lab, evidence suggests that MAT increased muscle activity (which is positively correlated to muscle strength). By pressing on the origin(s) and insertion(s) of a weakened muscle or performing isometric exercises, the proprioceptive sensitivity of the muscle spindles in the weakened muscle can be restored (BioConstructs). With regards to stretching, the evidence suggests that passive stretching is extremely detrimental to muscle activity whereas active stretching is greatly beneficial to muscle activity. Knowing that passive stretching decreases a muscle’s ability to contract efficiently, it can be coupled with MAT isometrics to restore a muscular function to an optimal level. I accept my hypothesis that both manual and isometric MAT treatment increase muscle activity to weakened or injured muscles.
“Muscle Activation Techniques”. biocontructs.com. 11 Nov. 2010.
Roskopf, G. “The Science Behind MAT”. muscleactivation.com. 11 Nov. 2010.
Muscle Activation Technician: Brad Carlson
Athlete: Dana Lyon
This report was reviewed by Lt. Col. Bishop
Melissa A. Beerse
Department of Biology, U.S. Air Force Academy, Colorado 80840
Go to the video section to SEE what passive stretching does!