Exercise as it relates to Disease/The functional impacts of strength training in cerebral palsy

Paper reviewed:Functional Outcomes of Strength Training in Spastic Cerebral Palsy By Diane L Damino and Mark F. Abel

Background
Physical weakness is a recognized clinical characteristic of spastic cerebral palsy. Despite this, such symptoms are rarely addressed therapeutically. With increasing rates of diagnosis (2-3% per 1000 births), the pre-existing prejudice towards utilizing strength training programs as a treatment initiative for children with cerebral palsy has been overlooked as researchers become more interested in the concept.

Where is the research from?
Diane L. Damiano and Mark F. Abel, two researchers from a cerebral palsy clinic in Virginia proposed the foundations for the investigation. The study was commenced in 1998 through the partnership of: The American Congress of Rehabilitation and Medicine as well as The American Academy of Physical Medicine and Rehabilitation. The research was carried out in a paediatric rehabilitation centre using facilities from a tertiary hospital.

What did the research involve?
Cerebral palsy patients can be divided into several clinical subgroups, for this study two diagnosed populations were involved: spastic hemiplegia and patients with moderate-severe spastic diplemia. A more severe diagnosis class was selected for the diplemia group, to allow researchers to observe and compare the impacts training may have on a spectrum of diagnosed individuals.

11 participants met the pre-requisite conditions and were approved for the study. Finding appropriate subjects was difficult, many eligible candidates had additional underlying medical conditions.

The 11 chosen subjects were aged between 8-14. All participants demonstrated less than 50% of normal muscular strength. The research involved trials that compared the strength of 8 muscle groups before and after the introduction of the strength training. The training program lasted for 6 weeks and included 3 sessions per week. Numerous tests were used to evaluate the results including: hand-held dynamometers, gait analysis, gross motor function measure and energy expenditure. The intensity of each individuals program was specific to their age and functional capabilities.

What kind of research was this?
The investigation design was a prospective before and after trial. During both trials the isometric strength of 8 muscle groups located in the upper and lower extremities were evaluated by measuring strength output, range of motion and general functionality. Functional measurements including gait velocity were utilized to investigate the impacts of the training on general mobility.

The variety in diagnosis amongst the participants is an advantage of this study. Comparing the subjects allowed for conclusions to be denoted in relation to potential limitations and advantages of the strength training. Having two different subgroups represented, along with varying symptom severity, provided an insight into how this treatment could benefit all subgroups.

A weakness of the study was the small subject base; due to the availability of appropriate subjects. Not limiting the participants to particular clinical subgroups would allow researchers to compare how different diagnostic symptoms are affected by strength training. Administering tailored programs derived from the individual’s subgroup would allow more physically capable individuals to excel and complete advanced testing procedures. Extending the duration of the training program would improve the prospective results and created more reliable data.

Basic results?
Both groups displayed significant strength gains in the targeted muscles. The overall cohort experienced: an increase in gait velocity and cadence, an improved gross motor function measure and no change in energy expenditure. The hemiplegia patients previously displayed astonishing strength differences (asymmetry) between the two sides of their body. The average improvement in strength asymmetry imbalance was 21%. The typical absolute strength gain across all muscle groups was 22.7N. The diplemia group experienced an average bilateral strength increase of 39%. However, this improvement only totalled their accumulated muscle strength to 51% of normal body strength. The average absolute strength gain across all muscles was 34.5N.

How did the researchers interpret the results?
The results revealed all participants experienced an increase in gait velocity and no change in energy expenditure. Subjects who displayed greater improvements in velocity tended to experience a worsening in gait efficiency. This was caused by the body’s delayed adaptive response to the strength gains. Subjects who excelled at a rapid pace had much higher heart rates during exercise, indicating their body hadn’t accommodated for the new level of intensity. Subjects who demonstrated smaller, more gradual improvements increased their gait velocity and efficiency simultaneously. From these observations researchers considered the opportunity for further improvements in cadence and velocity with a continuation of the strength training. Increases in strength resulting from the program had a strong correlation to an improvement in gross motor function measure. Improvements were primarily due to the frequent utilization of the lower extremities. The extent of improvement in other body regions was difficult to assess due to the participants limited motor capabilities.

Conclusions and implications
During the investigation no participants experienced a deterioration in functionality. The short term strength program demonstrated positive outcomes for all participants, regardless of diagnostic subgroup. To improve the results of similar investigations more physically challenging assessments should be introduced for individuals who have more advanced motor capabilities, this would encourage continuous improvement. The hemiplegia group experienced improvements in strength asymmetry; the average strength difference was reduced to 20%. However, by clinical diagnosis a strength difference greater than 10% is considered significant.

From the results, it was proposed that implicating strength asymmetry correction treatment prior to the commencement of strength training could prove beneficial. As a result of this investigation several related studies have been completed. Including: Early deep tissue treatment in cerebral palsy youths, alternatives to surgical correction in cerebral palsy and improvements in muscle symmetry in children using hippotherapy. More research focussing on the potential of extended resistance and strength training regimes has been conducted. In addition, other clinical symptoms of cerebral palsy are being addressed therapeutically, including muscle shortening and spasticity. Different therapy methods are been trialled including hydrotherapy, hippotherapy (horse riding), postural correction and new medications. With further research it’s possible that early strength training will become a prominent treatment initiative for cerebral palsy patients.