Knee muscle strength at varying angular velocities and associations with gross motor function in ambulatory children with cerebral palsy.
Kids with CP show knee flexor weakness tied to gross motor delays; test at varied speeds and target those muscles in treatment.
01Research in Context
What this study did
Hong et al. (2012) tested knee strength in kids with cerebral palsy who can walk.
They checked how strong the knee muscles were at slow, medium, and fast speeds.
Then they looked at how those scores matched scores on a gross-motor test.
What they found
The kids had the weakest knee flexors, the muscles that bend the knee.
Lower flexor strength and a low hamstring-to-quad ratio went hand-in-hand with lower motor scores.
Testing at different speeds showed deficits that single-speed tests missed.
How this fits with other research
Park et al. (2014) pooled many trials and found three 45-min strength sessions a week give big gains in CP.
Riches et al. (2016) add that these gains come with real muscle growth, even though only six small studies exist.
Meyns et al. (2012) and Iosa et al. (2012) show gait is shaky in CP; Wei-Hsien links that shakiness to weak knee flexors, giving a clear target for the strengthening programs the meta-analysis supports.
Why it matters
You now know weak knee flexors are a motor roadblock, not just a sidebar.
Add slow, medium, and fast speed tests to your eval so you do not miss the deficit.
Program knee flexor work at multiple speeds, aim for three sessions a week, and track both strength and gait harmony to see if the training carries over to smoother walking.
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02At a glance
03Original abstract
The aim of this study was to evaluate the relationships of muscle strength at different angular velocities and gross motor functions in ambulatory children with cerebral palsy (CP). This study included 33 ambulatory children with spastic CP aged 6-15 years and 15 children with normal development. Children with CP were categorized into level I (n=17) or level II (n=16) according to Gross Motor Function Classification System (GMFCS) levels. All children underwent curl-up test and isokinetic tests of the knee extensor and flexor muscle. Children with CP underwent the gross motor function assessments, including the Gross Motor Function Measure (GMFM-66) and the gross motor subtests of Bruininks-Oseretsky Test of Motor Proficiency (BOTMP). The hamstring-quadriceps ratio (HQ ratio) was calculated as 100%×(isokinetic peak torque of hamstring (knee flexor)/isokinetic peak torque of quadriceps (knee extensor)). Children with GMFCS level II had lower BOTMP and GMFM-66 scores, curl-up scores, HQ ratio, and knee muscle strength, especially knee flexor, compared to those with GMFCS level I. The regression analysis showed that knee flexor torques at 60 and 90°/s are mainly related to balance (r(2)=0.167, p=0.011) and strength (r(2)=0.243, p=0.002) while knee flexor torques at 120°/s mainly contribute to running speed and agility (r(2)=0.372, p<0.001). These findings suggest that children with CP had knee strength deficits, especially knee flexor. Postural muscle (knee flexor) strength dominated gross motor function than antigravity muscle strength (knee extensor). The knee flexor strength at different angular velocities was associated with various gross motor tasks. The HQ ratio may be used as a potential biomarker to probe the therapeutic effectiveness for muscle strengthening in these children. These data may allow clinician for formulating effective muscle strengthening strategies for these children.
Research in developmental disabilities, 2012 · doi:10.1016/j.ridd.2012.07.010