Strength has been found to be the most predictive factor of gross motor function in children with cerebral palsy (CP); however, more traditional and clinically applicable methods used to measure strength in this population are often unreliable and do not directly relate to changes in function or participation.1,2 Investigations of interventions addressing impairments in muscular strength to reduce or eliminate ambulation deficits in youth with CP have been weakened by poor methodology, intervention design, and variable protocol application.3 Concerns with the research have limited the ability to reach definitive conclusions regarding the effectiveness of strength training to improve functional movement for individuals with CP. No randomized, controlled trials consisting solely of progressive resistance exercise (PRE) have found improvements in gait after intervention.4–8 Interventions consisting of mixed neuromuscular training and focused PRE have shown both strength and functional improvements.9–11
Manual measurement of strength in individuals with CP has variable reliability (ie, reported intraclass correlation coefficient: −0.04 to 0.92) and limited usefulness as an outcome measure, whereas alternative measures of strength using functional movement patterns have shown excellent reliability and good validity.2 Evaluation of strength gains with these measures after PRE has primarily been limited to individual outcomes after group fitness courses or individuals demonstrating higher levels of independence on the Gross Motor Functional Classification System (GMFCS).11,12 A previous case report detailed the use of these measures to monitor change during physical therapy (PT) intervention with success.11 However, the use of these outcome measures to assess change in individuals with more significant functional limitations is still unknown.
This case report describes the design and outcome of a short and distinct episode of PT for a male in late adolescence with spastic diplegic CP ambulating at a GMFCS Level II with functional limitations and participation restrictions related to strength, endurance, and agility. Intervention consisted of the use of PRE to increase strength and specific functional training for improved and more efficient performance of functional activities to improve school and community access and performance during physical education classes.
DESCRIPTION OF THE CASE
History and Systems Review
E.K. was an 18-year-old, white male adult with spastic diplegic CP who received PT at a private, outpatient pediatric PT clinic since the age of 9 months. He lived in a single-level Cape Cod-style home with his mother, father, and younger brother. E.K. was a senior at a nearby high school with plans to attend either a community college or 4-year institution after graduation, but he had no specific area of study or career direction identified. He had an individualized education plan at his high school that provided for the services of an instructional aide during study halls and additional time to take examinations. He had received school-based PT services in the past, but direct PT services at school had been discontinued 7 years prior to this episode of care. He participated in the general education curriculum, including physical education, and was involved in extracurricular activities as a manager of his high school football team and a member of chorus. He enjoyed hunting with his father and had an active interest in learning about World War II history and collecting artifacts from that time period. E.K. received psychological care to address anxiety at the ages of 3 and 6 years and began taking Prozac at the age of 18 years because of a recent recurrence of symptoms of unknown origin but possibly attributed to multiple factors including his approaching high school graduation and uncertain plans. Surgical history included multiple heel cord, hamstring, adductor, and right rectus femoris lengthening procedures occurring at the ages of 3, 7, and 15 years. Each surgery significantly improved functional mobility and ROM according to a review of previous medical records and parent report. His primary goals for seeking PT at this time were to improve his ability to keep up with his peers in physical education classes and to decrease the use of single point canes (SPCs) in school, outdoors, and in the community.
Regular standardized assessment of gross motor development was completed periodically throughout the years of treatment E.K. received at this clinic. E.K.'s most recent scores on the Gross Motor Functional Measure–88 had plateaued and were recorded for standing (D) and walking/running/jumping (E) as 82% and 75%, respectively, at the age of 15 years, and 85% and 78%, respectively at the age of 17 years. E.K. began the use of bilateral Ultraflex Adjustable Dynamic Response ankle-foot orthoses (AFOs) (Ultraflex Systems, Inc., Pottstown, Pennsylvania) at the age of 15 years, resulting in increased independence with ambulation, reduced need for assistive devices, and improved gait efficiency. E.K.'s functional mobility was rated at Level II on the GMFCS because of the use of a rail to negotiate stairs and use of 2 SPCs for ambulation at school or when running, jumping, or navigating uneven terrain.13 He also had emerging skills classified at a GMFCS Level I (independent curb negotiation).13 He had a history of falls at home, school, and in the community when choosing not to use SPCs but did not fall when using hand-held assistive devices. E.K.'s history of CP, plateaued Gross Motor Functional Measure–88 scores, and desire to increase independence in the community and improve performance in physical activities with his peers provided the impetus for him to proceed with another episode of PT.
Based on a review of systems, further examination of E.K.'s musculoskeletal, neurological, and cardiopulmonary systems was deemed necessary. Bilateral AFO use and presence of multiple surgical scars warranted visual monitoring of E.K.'s integumentary system. He was being treated by a psychiatrist for psychosocial/emotional issues. Mild impairments of his cognitive/communication systems were being monitored by his school team. No impairments were reported in the endocrine, genitourinary, or gastrointestinal systems and required no further screening, testing, or referral.
Functional Movement Observation
Gait and functional movement observation without the use of SPCs or AFOs revealed a crouched pattern with inconsistent heel first contact and limited hip extension in terminal stance bilaterally. He ambulated with decreased left step length and upper extremities held in a medium guard position. Half-kneel to stand transitions were completed with the use of both upper extremities to push up from the floor and recovery steps to maintain balance after standing. E.K. ascended a 6-inch curb from standing with recovery steps (to regain balance) but required close supervision to minimum assistance to maintain balance while descending. He displayed less stability when leading with the right lower extremity for both half-kneel to stand transitions and curb negotiation.
Examination/Tests and Measures
Goniometry and the Modified Tardieu Scale were employed to quantify limitations in lower extremity movement. Manual muscle testing (MMT) was used to assess the strength of lower extremity musculature and observe compensatory movement patterns. The 6-Minute Walk Test (6MWT) and Timed Up and Go test (TUG) were used to measure cardiovascular endurance and agility.14,15 The 6MWT was conducted using a protocol previously described by Maher and colleagues14 by collecting total distance, resting and final heart rate, and rate of perceived exertion. In addition, a battery of tests with normative data available and validated for youth with CP was conducted. The tests quantify strength through 30-second maximum repetitions of select functional movements, agility, and anaerobic power, including the muscle power sprint test (MPST), 10×5-m sprint test (ST), lateral-step test (LST), sit-to-stand test (STS), and half-kneel-to-stand test (KST). The MPST and ST have excellent reliability and good construct validity with previously reported minimal detectable change (MDC).16,17 The LST, STS, and KST have good construct validity, previously reported MDCs and acceptable to excellent reliability, exceeding the reliability of hand-held dynamometry when used either by themselves or as side-to-side total.2 The testing was conducted with E.K. using bilateral AFOs and without SPCs.
Results of the examination process revealed significant ROM deficits, mild spasticity, and marked lower extremity weakness, especially in gluteal and plantar flexor muscles (Tables 1–3). Impairments in neuromuscular control were manifest through observation of difficulty isolating individual muscle groups during resisted knee and hip extension, dorsiflexion with knee extended, and functional movement. In addition, 30-second maximum repetition functional movement and performance measures revealed significant deficits in cardiovascular endurance, agility, and power generation (Table 4). Compared with other adolescents ambulating at GMFCS Level II, E.K. performed in the lower portion of the 25th percentile on MPSTMean and ST.17 He had 69% to 78% deficits on the LST, and 60% to 100% deficits on the KST, dependent on the side tested.2 His TUG performance was 4% better than that reported for a group of children and adolescents with CP ambulating at GMFCS Levels I to III, but a 19% deficit was measured when compared with peers ambulating at GMFCS Level II.15 Performance on the 6MWT showed a 13% deficit when compared with adolescents ambulating at GMFCS Level II.14 Using the process described by Atkinson and Nixon-Cave,18 the relationships between body structure/function impairments, functional activity limitations, and participation restrictions are summarized in Figure 1.
Short-term prognosis was determined to be good. Adolescents receiving PT with a focus on function and resistance training have been shown to demonstrate improved functional performance, gait mechanics/efficiency, and increased muscle power generation.19,20 These increased activity levels are also related to improved walking economy and improved quality of life. E.K.'s age and high activity/motivation levels, when combined with focused functional strengthening and cardiovascular training, provided him with the opportunity to improve functional ability and participation levels.
Long-term prognosis was guarded primarily as a result of his transition from adolescence into adulthood. Adults with CP receive less health care services than age-matched peers, experience activity limiting orthopedic pain secondary to overuse injury, have decreased ambulatory ability, increased fatigue with activity, and decreased activity with age.19,20 Fatigue, pain, and subsequent decreased activity levels can lead to systemic disease, psychological disorders, and decreased quality of life.20 However, adults with CP who have higher functional mobility are more active and have fewer adverse health events than peers with more limited mobility.21 E.K. was expected to experience age-related reductions in ambulatory ability and functional mobility because of decreased activity and overuse-related orthopedic pain as he aged. However, his motivation to exercise and to participate in school and community activities was anticipated to limit these negative effects. Short- (6-week) and long-term (12-week) goals for this episode of care are detailed in Table 5. Goals were formulated using previously reported or calculated values of MDC in performance measures.
Description of Intervention
The intervention took place during two 1-hour PT sessions per week complemented by a home exercise program (HEP) over a 12-week period. Positive changes in neuromuscular performance and muscle strength have been measured in patients with CP participating in resistance exercise programs with aerobic training in 8 to 12 weeks.9–11 Single-point canes were not used during PT sessions, but bilateral Ultraflex Adjustable Dynamic Response AFOs were worn in all PT sessions to assist in standing, transitional movement, and ambulation emphasizing the goal of increased independence.
Interventions were developed to (1) remediate strength deficits, (2) provide opportunities to train at higher cardiovascular intensity levels, and (3) use new strength and endurance gains to perform novel or difficult functional tasks through neuromuscular facilitation. A circuit-training format was used to reduce the amount of time spent resting between activities with the intent of maximizing cardiovascular response. Training consisted of a combination of PRE, body weight–supported treadmill training, and focused functional training with neuromuscular facilitation. Interventions are summarized in Table 6. American College of Sports Medicine criteria for strength training were met for intervention design and implementation.22 Strengthening interventions focused on hip abductor, knee extensor, and hip extensor groups because of E.K.'s specific strength impairments and the positive relationships between strength of these muscle groups and ambulatory ability in individuals with CP. Treadmill training was used as the mode of aerobic training, although treadmill speed was unable to be advanced to achieve the desired training level of 70% of maximum heart rate due to postural instability and safety concerns. Instead, focus for treadmill training was changed to maintaining postural stability at increasing speeds, regardless of heart rate achieved. Joint mobility and prevention of contractures were accomplished through a combination of weekly manual therapy administered by a physical therapist and a daily self-administered home stretching program. Functional training activities were selected on the basis of patient goals to improve athletic participation and independent mobility in the community.
Description of Outcomes
E.K. achieved all short-term goals and 1 long-term goal established for this episode of intervention. E.K. negotiated a 6-inch curb safely without physical assistance or assistive devices and completed half-kneel to stand transitions without the use of his upper extremities or assistance for the first time in his life. Most importantly, E.K. reported improvements in participation during physical education classes and community events, began taking a more active role managing his high school football team, and began participating in community-based PT services without the use of SPCs after this episode of care. These improvements were attributed to increased confidence in his dynamic balance, ability to negotiate obstacles, decreased incidence of falls when choosing not to use SPCs, and ability to complete floor-to-stand transitions without support.
Lower extremity ROM did not change significantly in any joints measured (Table 1). Similarly, spasticity, as quantified by angle of catch, and amount of resistance generated in response to high velocity movement on the Modified Tardieu Scale did not change significantly (Table 2). As expected from the results of other investigations, spasticity and ROM did not change as a result of resistance training.7
Strength of key lower extremity muscle groups increased as measured through MMT, though not to the degree set in long-term goals (Tables 3 and 5). Importantly, bilateral dorsiflexor strength improved 1 grade and variable improvements in gluteus maximus and gluteus medius strength were measured (Table 3). In addition, improvements in movement quality used to maintain MMT positions were observed, especially during gluteal strength testing. Results of the MPST, ST, functional strength tests (KTS, STS, and LST), 6MWT, and TUG with MDCs for each test are summarized in Table 4. Minimal detectable changes for MPST, ST, and functional strength tests were calculated from the results of investigations of children rated at GMFCS Levels I and II; however, 6MWT and TUG MDCs included children rated at GMFCS Levels I to III.2,14–16 Sit-to-Stand repetitions increased by more than the MDC, but LST, KST, and combined left- and right-sided functional strength tests (ie, right KTS repetitions + right LST repetitions + STS repetitions) did not increase (Table 4). Anecdotally, E.K. achieved greater percentages of success in task completion that could be interpreted as demonstration of improved motor planning.
Tests of aerobic and anaerobic capacity and agility had mixed results. Anaerobic power, measured with the MPST, and agility, measured with the ST, improved; however, changes failed to reach MDC.16 Distance on the 6MWT at final measurement increased by 13.35 m from baseline testing, but this difference did not reach MDC.14 An improved level of fitness was demonstrated by similar exertion reports on the Borg Rate of Perceived Exertion (6/10) and a decreased heart rate at final testing compared with initial testing (from 136 beats per minute to 128 beats per minute). The TUG time decreased by 2 seconds and was greater than the MDC calculated from data for children and adolescents with CP ambulating at GMFCS Levels I to III.15
E.K. achieved personal functional goals related to mobility at school and in the community. Several causes may have contributed to not meeting all long-term goals set for the episode of care. First, lack of patient adherence with the HEP, limited length of the course of treatment, and alteration of original treatment plan regarding treadmill training may have had an effect. Second, while evidence regarding the effectiveness of increasing strength in children and adolescents with CP is established, the carryover of increased strength to improved function is unclear. Third, some of the selected tests and measures may not have been reliable or sufficiently sensitive (MMT) or specific enough to a given system (6MWT) to measure the desired effects of the intervention plan in the given time frame. Finally, MDC values used for goal formation may not have been accurately applied to E.K.'s functional status and GMFCS level. Each of these causes deserves to be clarified further.
Despite E.K.'s full effort in completing activities during twice-weekly PT sessions, he reported noncompliance in routinely completing portions of his HEP due to competing extracurricular commitments. Although American College of Sports Medicine guidelines for resistance training were met during PT sessions, expectations for improvement reflected in the initial treatment goals may have been overly optimistic. Given the relatively short time period for this episode of PT intervention and E.K.'s impairments and limitations, a more cautious estimation of expected change may have been appropriate.5 Sustained cardiovascular training was challenging to achieve because of postural instability and safety concerns when attempting to reach treadmill or overground speeds at sufficient levels of speed and incline despite the use of a body-weight support system. In response, the intervention plan was adjusted during the episode of care by focusing on maintenance of upright posture at increasing speeds in an effort to improve gait mechanics and efficiency rather than maximizing speed to achieve desired cardiovascular parameters. This change may have increased ambulatory efficiency by improving gait mechanics as measured by increased 6MWT distance. However, this change did not meet the MDC and could potentially be attributed to test-retest variability.14
The evidence regarding effectiveness of affecting the functional status of youth with CP using strength training programs is unclear.3 Combined PRE and functional movement interventions informed by current exercise progression guidelines have shown success in improving strength and functional performance in children and adolescents with CP.7 However, in a recent systematic review and meta-analysis, Scianni and colleagues6 concluded that strength training programs are ineffective in improving strength and function in children and adolescents with CP, differing from conclusions reported in previous systematic reviews.7,8 Unfortunately, Scianni and colleagues considered interventions of questionable efficacy or exercise prescriptions, including neuromuscular electrical stimulation.6 A randomized, controlled trial using a group exercise format following current strength training guidelines found moderate increases in strength, but no functional improvements, in school-aged children (6-13 years) with CP.12,23 Application of these findings to individualized PT treatment is limited, however, because children in that trial did not receive intervention targeted to specific individual impairments and limitations.12,23 In addition, a recent randomized trial comparing traditional strength training and velocity training of the quadriceps found significant improvement in functional measures of gait for the velocity training group.24 Greater improvements in functional performance might have occurred if resistance training was applied to address specific strength impairments and if strength training specifically addressed muscle power generation.
Use of MMT and hand-held dynamometry in children/youth with CP has been shown to be unreliable (intraclass correlation coefficients: −0.04 to 0.92),2 and usefulness of measuring and monitoring strength changes that result from intervention is limited because of poor reliability. However, MMT did provide clinically useful information about E.K.'s ability to isolate activation of individual muscle groups. Functional strength tests and movement observation provided a greater understanding of measured MMT results and the influence of increases in strength on functional movement including curb negotiation, half-kneel transitions, and ambulation.
The TUG and 6MWT have been considered to more accurately reflect the agility of individuals with CP under different task constraints due to the large number of 180° turns involved in the testing protocols.14,15 The degree of change of E.K.'s improved TUG time contrasts with the results of the 6MWT and another measure of agility, the ST. The faster speed and larger number of directional changes required during the ST (ie, ten 180° directional changes) or 6MWT (ie, 32-39, 180° directional changes) when compared with the TUG likely explain these contrasting results. The 6MWT has excellent intra- and interrater reliability when used with children and adolescents with CP, but coefficients of variation indicate high variability in individual performance that complicate its use to measure meaningful changes in individual performance clinically.14 Verschuren and colleagues25 have shown excellent reliability and validity for a shuttle-run test that may be more clinically applicable. The results of the TUG, 6MWT, and ST indicate that E.K. may not have developed enough strength or endurance in his gluteal muscles for a sustained, high-speed effort as required in the ST and 6MWT.
Clinically applicable statistics for the MPST, ST, KST, STS, and LST may not accurately reflect detectable change for individuals whose mobility is classified as a high GMFCS Level I or a low GMFCS Level II. In studies by Verschuren and colleagues,2,16 the GMFCS criteria for the 6- to 12-year-old strata were used to classify study subjects, regardless of age. In addition, performance results of children and adolescents in GMFCS Levels I and II were combined to report data.2,16,17,26 Reporting of combined data may make the use of these tests difficult to interpret clinically when using standard calculations of detectable change for individuals at the top or bottom of their functional movement classification.
While the utility of these tests is clear—changes in E.K.'s ability to move in a functional and efficient manner were easily and reliably measured—use of these MDC levels for E.K.'s goal formation may have been overly optimistic given the severity of his mobility limitations. Reaching personal functional goals and therapeutic 6-week goals by the end of the 3-month episode indicates that a longer episode of care may have been necessary to demonstrate differentiated change.
E.K. experienced improvements in strength, agility, and self-rated function and participation as a result of this episode of care, but additional time to demonstrate statistically measureable changes using the selected outcome measures may have been required. This case report provides support for the use of functional strength testing as a clinically meaningful outcome measure for an adolescent or young adult rated at GMFCS Level I or II in the 6- to 12-year age strata, but suggests the need for additional knowledge regarding levels of detectable change more specific to a patient's functional ability.
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