Sample Protocol for Testing of Muscle Injury or Muscle Imbalance

The following protocol describes a procedure for assessing the muscle health of the knee extensors during or following anterior cruciate ligament (ACL) surgery rehabilitation.

Resting Muscle Tone: The athlete is positioned in a supine position with legs extended or flexed over the edge of the treatment table. Myotonometric measurements are then taken of the desired muscles for each leg (legs must be positioned similarly). The Myotonometer probe is pressed onto the muscle perpendicularly until an audible tone is heard. The probe is then lifted off the muscle and re-positioned to take the next measurement. Five probe measurements are suggested. This requires less than one minute for data acquisition. For knee extensors the rectus femoris, vastus lateralis and vastus medialis can be measured separately. The athlete can then be asked to move into a prone position with legs extended and the biceps femoris tested if desired.

Muscle Strength: Muscle strength is assessed using a maximal voluntary isometric contraction. The athlete does not have to be in the same position during assessment of muscle strength as they were for resting muscle tone. For instance, the athlete can be sitting at the edge of the treatment table with knees flexed or they can be positioned in isokinetic dynamometer equipment. The athlete is asked to maximally contract against an immovable force (e.g. cable attached to treatment table, examiner’s resistance etc.). The examiner asks the athlete to maximally contract the muscle to be tested. While the athlete contracts the muscle, the examiner presses the Myotonometer probe perpendicularly onto the muscle. A hand-held or computerized dynamometer can be used to ensure consistency of effort between trials if this is an issue. Dynamometry will measure total joint torque production but not provide information about individual muscles. Myotonometric measurements will provide information about individual muscle contribution to torque output.

Analysis: Several types of analyses are possible following the above outlined testing protocol. Resting muscle tone of the various muscles can be compared between the right and left legs. The resting tone should be the same. Stiffness of different muscles of the same leg should not be expected to be identical. Muscle stiffness during muscle contraction should show a significant difference from resting tone. In addition, muscle stiffness during contraction should be symmetrical between both legs. If myotonometric measurements were taken pre-injury or pre-surgery, they can be used to assess the rehabilitation and progress of specific muscles.

The following graph was generated by Myotonometer computational software and depicts data collected from the vastus medialis of an athlete three years following ACL surgery. The athlete tested normal during computerized isokinetic testing.

Myotonometer measurements of vastus medialis (VMO) of an athlete who had ACL surgery three years prior. Red line shows resting muscle tone. The green line shows the stiffness obtained from the non-surgical leg during a maximal voluntary contraction. The blue line shows the stiffness of the surgical leg during a maximal voluntary contraction.

The small difference between stiffness of the surgical VMO during contraction (blue line) from resting stiffness indicates weakness of this muscle (despite the fact that computerized isokinetic dynamometry indicated equal strength of both legs). This assessment of weakness is further verified by the inability of the surgical VMO to generate as much stiffness during contraction as the nonsurgical VMO (green line).

(Note that the legend [generated from the computer’s clock] indicates that all data were acquired in less than two minutes).

Sample Protocol for Testing Spastic Paresis