A common question that occupational therapists ask is if you can perform manual muscle testing (MMT) on a patient who has increased tone (hypertonicity) or rigidity (e.g., Parkinson’s Disease).
“Manual muscle testing usually is not appropriate for clients who exhibit moderate to severe hypertonicity or rigidity” – Pedretti1
When occupational therapists perform MMT, the client is positioned in a way that allows for optimal muscle engagement and joint alignment. This often involves placing the client in a seated or supine position, depending on the muscle group being tested. The therapist ensures proper stabilization to isolate the muscle or muscle group being tested. This involves stabilizing the adjacent joints and structures to prevent unwanted movements and ensure that the force applied during the test is focused on the target muscle. Then the OT provides manual resistance to the client’s movement as they perform a specific muscle action. The resistance is applied in the opposite direction of the muscle’s contraction to challenge its strength. The therapist’s force should be gradual and steady to allow the client to exert maximal effort.
Hypertonicity and Rigidity
However, in clients with moderate to severe hypertonicity or rigidity, the muscle tone and strength are altered due to neurological or neuromuscular conditions. Hypertonicity refers to increased muscle tone, often associated with conditions such as cerebral palsy or stroke. Rigidity, on the other hand, refers to increased resistance to passive movement and is commonly observed in conditions like Parkinson’s disease.
In these cases, the altered muscle tone and lack of voluntary or selective movement make it challenging to obtain accurate results through manual muscle testing. The rigidity or hypertonicity may cause the muscles to be stiff and unyielding, leading to limited range of motion and difficulties in performing isolated movements. This can interfere with the accuracy and interpretation of the muscle testing results.
- Lack of voluntary control: Increased muscle tone often leads to a loss of voluntary control over the affected muscles. The ability to initiate and sustain a muscle contraction voluntarily may be compromised. This makes it challenging for the client to actively engage and produce a controlled muscle contraction during MMT.
- Impaired selective movement: Hypertonicity or rigidity can result in difficulties with selective movement. Selective movement refers to the ability to isolate and contract specific muscles while keeping other muscles relaxed. The increased muscle tone can cause co-contraction or involuntary activation of adjacent muscles, making it difficult to assess the strength of individual muscles accurately.
- Altered muscle length-tension relationship: Increased muscle tone can affect the normal length-tension relationship of muscles. Hypertonicity often results in a state of increased muscle tension or tightness, which can limit the muscle’s ability to generate force. This altered muscle length-tension relationship can affect the results of MMT, making it difficult to differentiate between true weakness and the effects of increased tone.
- Resistance to passive movement: In cases of rigidity, there is increased resistance to passive movement, making it challenging to assess muscle strength using manual resistance. The resistance encountered during passive movement may be constant (lead pipe rigidity) or exhibit a ratchet-like or cogwheel quality (cogwheel rigidity). This resistance can interfere with the accuracy of MMT and may not provide a reliable measure of true muscle strength.
What to Document for MMT
- Instead of focusing solely on the strength of the muscles, document your observations regarding the client’s muscle tone, movement patterns, and any compensatory strategies used.
- Note any specific characteristics or abnormalities related to the increased muscle tone, such as hypertonicity, rigidity, or involuntary movements.
- Acknowledge the limitations of MMT due to the client’s increased muscle tone or rigidity.
- Discuss the functional impact of the increased muscle tone on the client’s activities of daily living, mobility, and overall functional abilities.
- Document any specific difficulties or limitations encountered.
- If alternative assessments were used to evaluate muscle function or movement patterns, document those findings as well.
- Observation of functional movements and engagement in occupations – highlight the value of OT.
- Evaluation of overall motor control and coordination.
- Use of spasticity outcome measures such as the Modified Ashworth Scale or the Tardieu Scale for spasticity.
- For rigidity, clinical measurement seems to be more difficult and instead can be achieved with equipment such as sensors (which we don’t have access to as OTs).2
Measuring Outcomes and Goals
- Focus on functional assessments that evaluate the client’s ability to perform specific tasks or activities related to their daily life. This can include assessments of mobility, transfers, self-care tasks, fine motor skills, or other functional activities that are relevant to the client’s goals. Use standardized functional assessment tools or develop functional tasks specific to the client’s needs.
- Document and track the client’s range of motion in affected joints. Use goniometry or other measurement tools to quantify changes in joint range over time. This can help monitor improvements or identify limitations in joint mobility associated with hypertonicity or rigidity.
- Conduct systematic observations of the client’s movement patterns, posture, and overall motor control during functional activities. Note any improvements or changes in movement quality, efficiency, or compensatory strategies used by the client.
- Utilize patient-reported outcome measures to gather subjective information directly from the client regarding their perceived functional abilities, quality of life, pain levels, or other relevant aspects, e.g., COPM.
- Engage in collaborative goal-setting with the client, focusing on functional goals that are meaningful and relevant to their daily life.
- Develop or utilize task-specific assessments that evaluate the client’s performance in activities requiring muscle strength, coordination, or motor control. These assessments can be designed to target specific movements or functional tasks affected by hypertonicity or rigidity.
The primary goal of MMT and its documentation is to accurately represent the client’s presentation and provide a comprehensive understanding of their condition. It is crucial to individualize the measurement of outcomes and goal-setting based on the client’s specific needs and functional limitations. Regular reassessment and collaboration with the client are essential to monitor progress, make adjustments, and ensure that goals remain relevant and achievable throughout the therapeutic process.
Including the limitations and nuances of MMT in the context of increased muscle tone or rigidity can help inform the overall evaluation and guide appropriate interventions. The big mistake to avoid is performing and documenting MMT and not mentioning anything such as these two symptoms as if they were otherwise ‘normal’.
- Schultz-Krohn, W., Pendleton, H. M. (2017). Pedretti’s Occupational Therapy – E-Book: Practice Skills for Physical Dysfunction. United States: Elsevier Health Sciences.
- Ferreira-Sánchez MDR, Moreno-Verdú M, Cano-de-la-Cuerda R. Quantitative Measurement of Rigidity in Parkinson´s Disease: A Systematic Review. Sensors (Basel). 2020 Feb 6;20(3):880. doi: 10.3390/s20030880. PMID: 32041374; PMCID: PMC7038663.