Coactivation During Dynamometry Testing in Adolescents With Spastic Cerebral Palsy

Area of Science:

• Biomechanics
• Neurology
• Rehabilitation Science

Background:

• Dynamometry is widely used to assess knee extensor strength in individuals with cerebral palsy (CP).
• Increased muscle coactivation during testing can lead to inaccurate strength measurements and reduced validity.
• The extent of coactivation and its influencing factors in CP during dynamometry remain unclear.

Purpose of the Study:

• To investigate coactivation in adolescents with and without CP during dynamometer tests.
• To determine the impact of Gross Motor Function Classification System (GMFCS) level, load, and muscle fatigue on coactivation.

Main Methods:

• Cross-sectional observational study involving adolescents with and without CP.
• Maximal voluntary torque (MVT) and submaximal dynamic contractions at varying loads were performed.
• Surface electromyography measured coactivation between quadriceps and hamstring muscles, calculating a coactivation index (CAI).

Main Results:

• Adolescents with CP (GMFCS level II) exhibited significantly higher CAI values than those with CP (GMFCS level I) and typically developing (TD) individuals.
• Coactivation levels were consistent across different load levels and during fatigue for most groups.
• TD adolescents showed a decrease in CAI at low-load conditions during fatigue.

Conclusions:

• Higher coactivation in adolescents with CP (GMFCS level II) can lead to underestimation of agonist muscle strength.
• Coactivation during dynamometry is independent of load and fatigue within the tested groups.
• Results emphasize the need to consider coactivation when interpreting strength measurements in individuals with CP.