Functionally relevant physical exercises as an objective measure of clinical improvement in pediatric chronic pain

Abbreviations

IIPT Intensive Interdisciplinary Pain Treatment

LEFS Lower Extremity Functional Scale

UEFI Upper Extremity Functional Index

FRPE Functionally Relevant Physical Exercise

1 Introduction

Chronic pain is defined as persistent or recurring pain lasting longer than three months. Although most children who report chronic pain can perform day-to-day activities, it has been found that 3–5% [1–3] experience severe functional impairments, such as inability to attend school, decreased socialization, avoidance of physical activity, and subsequent deconditioning. Due to prolonged deficits across multiple domains of functioning, children with chronic pain and associated dysfunction often require intensive inpatient pain treatment (IIPT) to regain age-appropriate functioning. These interventions have been replicated across treatment sites to support their efficacy [1, 4–6]. Physical and occupational therapies play a critical role in children’s consistent physical functioning, as there is consistent evidence that exercise has a clinically relevant effect on pain when compared to no intervention or conservative therapies [7]. Despite reported positive outcomes of IIPT programs, many do not report objective physical functioning data as part of peer-reviewed outcomes [8, 9].

As one example, physical self-report measures [10–12] have helped to demonstrate subjective changes in independent functioning and assess perceived functional gains in pediatric pain rehabilitation [13–15]. While these tools have proven useful as outcome measures, subjective reports are limited by potentially confounding psychological factors, such as perceived self-efficacy, a global sense of impairment, and/or poor insight [16, 17]. Objective measurement isolates the child’s actual physical performance (e.g., posture, balance, joint mobility, motor function, muscle strength, gait) from psychological constructs or self-perception. Therefore, including objective tools in clinical assessment helps to create a holistic assessment of physical functioning and identify clinical therapy targets for treatment and monitoring of progress.

The complicating factor in objective assessment involves the selection, application, and scoring of functioning, particularly in an intensive program with varied pain conditions and restricted time, space, and staffing. Due to extreme differences in age, diagnosis, and levels of physical functioning at the time of admission, it is challenging to find a single set of established objective measures to support chronic pain rehabilitation. Also, children with chronic pain, regardless of diagnosis, often demonstrate limited or inconsistent deficits in several areas, particularly in day-to-day functional domains. For example, a child may demonstrate appropriate strength via manual muscle testing yet struggle with the functional application during sit-to-stand or floor-to-stand transitions. While research on objective physical functioning/impairment is on the rise, it can be difficult to quantify [1, 18] in a way that is clinically meaningful and practically applicable in IIPT.

Existing standardized objective tools present several limitations for use with children with chronic pain. As one example, the Bruininks-Oseretsky Test of Motor Proficiency (BOT-2) [19] can gather valuable information related to fine and gross motor skills and coordination; however, it involves a lengthy assessment and scoring period and strict assessment protocol, and it does not directly reflect common gross motor skills used in daily physical functioning. Anecdotal evidence suggests that children in chronic pain do not tolerate long structured assessments, nor do they present with sufficient energy or stamina to complete them, leading to an artificial floor effect. It is also argued that psychosocial variables (e.g., self-efficacy, fear of pain, low motivation) show greater potential influence in assessments requiring sustained effort.

This aim of this study was to demonstrate the application of functionally relevant physical exercises (FRPEs) as a potential enhancement to evaluate functional strength, endurance, and mobility for children with chronic pain. The practical benefit of FRPEs as applied in this clinical population were: 1) easy to administer in variable settings, 2) well-tolerated by children with chronic pain upon evaluation, 3) relevant to day-to-day function, and 4) sensitive to measuring change across three weeks of intensive rehabilitation. It was hypothesized that children’s objective physical functioning using FRPEs would be similar but distinct from subjective measures of functioning, yielding weak to moderate correlations between subjective and objective measures. It was also hypothesized that FRPEs would capture clinical improvement in physical functioning following IIPT, similar to prior reports of clinical improvement using subjective measures.

2 Methods

3 Results

4 Discussion

Children with chronic pain can suffer from severe impairments impacting age-appropriate functioning and day-to-day tasks. The primary goal of pediatric chronic pain rehabilitation is to improve daily functioning for these children, often over the course of intensive interdisciplinary pain treatment programs. While studies demonstrate overall improvement following IIPT programs [1, 29], reported outcomes do not typically isolate objective physical functioning from subjective assessment methods. More recently, there has been an attempt to increase the resources available to collect and monitor physical functioning more objectively [14, 18].

A primary aim of this study was to enhance clinical assessment and monitoring of children with chronic pain by providing practically measurable and clinically relevant objective data of physical functioning (i.e., strength, endurance, and mobility) using FRPEs. The FRPEs used in this study were readily administered, easily interpreted, and relevant to treatment planning and clinical monitoring. They also did not present with floor effect and demonstrated a range of performance across children assessed. As hypothesized, FRPEs functioned in a similar manner to subjective measures of functioning: all captured clinical improvements following intensive rehabilitation treatments. In addition, FRPEs yielded weak (r’s 0.3 to 0.5) to moderate (r’s 0.5 to 0.7) correlations with subjective measures at both admission and discharge, suggesting that objective measurement captures a related but distinct aspect of physical functioning. This aligns with previously reported limitations of subjective measurement, which may be confounded by psychosocial factors such as self-efficacy, a global sense of impairment, and/or poor insight. This study highlights the possibility, and potential benefit, of isolating objective performance from subjective assessment.

This study adds to existing research by examining and reporting objective FRPEs as a practical method to enhance assessment and goal setting for chronic pain. FRPEs were designed to be easily administered in variable settings, seemingly well tolerated by children with chronic pain when initiating treatment, relevant to day-to-day function, and sensitive to measuring change over three weeks. FRPEs provided a meaningful observation of the child’s functioning by closely resembling functional tasks, offering increased perception of physical functioning and improved understanding of functional gains in rehabilitation. These FRPEs also seemed to be the appropriate challenge level, as more than 91% children could complete at least one repetition of the exercise during the initial evaluation. Finally, the FRPEs demonstrated practical benefits of using several single-item FRPEs instead of a lengthy standardized method (e.g., BOT-2), as FRPEs could be completed as separate tests, allowing rest breaks or other modifications that naturally occur during a busy pediatric rehabilitation environment. As a set, these exercises objectively captured both existing deconditioning at admission and functional gains at discharge.

Other points of discussion were observed in the data. First, correlations were strongest between FRPEs and the LEFS, which intuitively makes sense, as most functional exercises involved lower body strength and mobility. Further, correlations between subjective measures of functioning were very strong, suggesting that both capture a larger general construct of functional impairment. In addition, correlations were relatively weaker at discharge, suggesting that subjective perceptions may not change at the same rate or in the same manner as objective functioning. For example, a child with chronic pain may struggle to lift a gallon of milk prior to rehabilitation; after rehabilitation, this same child may clearly increase their ability to lift a gallon of milk but may or may not subjectively report improved functioning on the UEFI. These subjective measures with embedded psychosocial constructs are still important as indicators of improvement. In sum, both subjective and objective measures uniquely contribute to clinical assessment and monitoring of clinical improvement.

While not directly related to the hypothesis, it is often helpful to monitor self-reported pain in conjunction with other study variables in studies of chronic pain in children. A substantial change in self-reported pain severity was not observed over the three weeks of IIPT. Given that intervention occurred over only three weeks and that the therapy focus was to initially improve functioning across multiple domains for sustained gains after discharge, it was not common to see large decreases in pain level during the program. However, post hoc analyses showed that subjective report of pain was more highly correlated with subjective measures of functioning.

Further research in this area could expand the understanding and utility of FRPEs. As one example, in this study, children demonstrated clinically meaningful increases in subjective assessment of lower and upper extremity functioning. They also demonstrated an approximately 50% increase on all objective tools except for the six-minute walk (35%). As with studies on the LEFS and UEFI, future research could examine what amount of gain on FRPEs is not just statistically significant but shows clinically meaningful change. Additional research could isolate measures of strength and mobility from measures of endurance (e.g., six-minute walk) to clarify their independent role in measuring improvement. It is likely that strength and mobility gains occur before (and possibly influence) later gains in endurance. Further development of FRPEs may include simple versus complex movement-based tasks to better see variability in the level of impairment. In addition, other established functional exercises such as the two-minute step test, two-minute walk test, 10-meter walk test, stair climb test, chair stand test, and timed up and go test could be studied in the future [30–32].

5 Conclusion

Children with chronic pain often have impaired physical abilities. Current subjective measures of functioning do not isolate objective performance, and some objective measures have practical limitations. The use of FRPEs provides objective data reflecting strength, endurance, and mobility that is practical to administer, easy to score, and clinically meaningful as an addition to chronic pain rehabilitation programming. FRPEs add to clinical care by isolating objective measures of performance from perceptions or self-reports, appropriately capturing functional deconditioning at admission and functional gains at discharge. Pairing subjective self-report measures with FRPEs provides a pragmatic and meaningful way to assess overall physical functioning and track progress in chronic pain rehabilitation. The use of these function-based physical exercises may improve therapists’ understanding of functional strength and how it may facilitate or limit overall outcomes. In addition, objective measurement using these exercises allows clinicians to easily monitor a child’s progress, bringing attention to the importance of day-to-day tasks. Future research on FRPEs in pediatric chronic pain will further strengthen the understanding of these conditions and children’s response to rehabilitation. In sum, objective FRPEs offer a practical and meaningful addition to the assessment and treatment of childhood chronic pain.