Investigation of Physical Fitness in Children and Adolescents with Juvenile Idiopathic Arthritis: A Case–Control Study

Abstract

Objective:

Swelling, effusion, tenderness, and pain seen in the joints of juvenile idiopathic arthritis (JIA). This disease may cause limitation in joint movements, muscle weakness, atrophy, balance, and gait disorders. Physical fitness is accepted as an important determinant of health in both childhood and adolescence. The aim was to evaluate the physical fitness of children/adolescents with JIA and compare it with healthy peers.

Materials and Methods:

Seventy children/adolescents were included (35 JIA and 35 healthy). The Childhood Health Assessment Questionnaire (CHAQ) and the Brockport physical fitness test battery were used for evaluation. The Brockport physical fitness test battery consists of dominant handgrip strength, curl-up, push-up, trunk lift, shoulder stretch, sit and reach tests, skinfold thickness (calf/triceps/subscapular) measurements, and PACER 20 m test.

Results:

A significant difference was found in all sub-parameters of CHAQ (P < .05) and dominant hand grip strength (P = .037), curl-up test (P < .001), trunk lift test (P = .018), shoulder stretch (P < .001) and PACER 20 m test (P < .001) tests in favor of the healthy group.

Conclusion:

Children/adolescents with JIA demonstrated lower performance compared to their healthy peers in muscular and cardiovascular capacity tests (curl-up test, PACER 20 m test, trunk lift test, dominant hand grip strength test, and shoulder stretch test). Their functional abilities are more impaired, and they experience higher levels of pain and lower levels of general well-being compared to healthy peers.

What is already known on this topic?

• Many studies in the literature demonstrate that children with JIA have lower physical fitness levels compared to healthy children. However, among these studies, only 1 evaluated physical fitness levels using a standard test battery, which assesses only strength and flexibility.

What this study adds on this topic?

• To evaluate physical fitness in this study, the Brockport physical fitness test battery was preferred for its comprehensive subtests. This allowed for a detailed evaluation not only of strength and flexibility across multiple regions but also of fat and aerobic capacity. Consequently, children and adolescents with JIA demonstrated lower performance than their healthy peers in tests assessing muscular and cardiovascular capacity (curl-up test, PACER 20 m test, trunk lift test, dominant hand grip strength test, and shoulder stretch test), while their performance in the push-up test, skinfold thickness, and flexibility assessments was similar to that of their healthy peers.

Introduction

Juvenile idiopathic arthritis (JIA) stands as the most prevalent rheumatic disease among children.¹ Swelling, effusion, tenderness, and pain are seen in the joints in JIA. It may cause limitations in joint movements, muscle weakness, atrophy, and balance and gait disorders.² Even though the daily energy expenditure in children with JIA appears comparable to that of healthy children, their participation in vigorous physical activities and sports is quite low.^3,4

Physical fitness is accepted as an important determinant of health in both childhood and adolescence and is divided into 2 categories: health-related physical fitness (cardiorespiratory fitness, flexibility, muscular fitness, body composition, and neuromuscular relaxation) and performance-related physical fitness (speed, agility, reaction time, balance, strength, and coordination).⁵ During these periods, inadequate physical fitness has been associated with a range of problems (cardiovascular diseases, anxiety, depression, obesity, musculoskeletal disorders, and reduced quality of life).^6,7

The physical fitness tests ensure a health fitness standard that prevents chronic diseases associated with a sedentary lifestyle. Additionally, intermittent assessments provide information to the researcher or clinician about the course of the disease.^8-10 Therefore, it is important to evaluate all parameters of health-related physical fitness in a cost-effective and practical manner. Based on this idea, we chose the Brockport Physical Fitness Test battery. The Brockport Physical Fitness Test Battery was designed for both children with and without disabilities. This battery offers a detailed assessment with comprehensive subtests that evaluate strength, flexibility, fat, and aerobic capacity across multiple regions.¹¹ Through a comprehensive evaluation of patients with JIA, the physical manifestations of the disease could be assessed in detail for the first time. There is only 1 study by Patti et al¹² that evaluates physical fitness in patients with JIA using a standard test battery, which focuses solely on strength and flexibility. The aim of the present study was to evaluate the physical fitness (physical level, strength, flexibility, fat measurement, and cardiovascular capacity) of children/adolescents with JIA and compare it with healthy peers.

Materials and Methods

Study Design

This study was designed as a 2-group, case–control study. The JIA group was compared with the healthy group.

Recruitment

An enrollment period was from January 2020 to July 2020.

Participants

Thirty-five children/adolescents with JIA and 35 healthy children/adolescents with similar demographic characteristics to JIA were included. The JIA group was selected from patients fulfilling ILAR diagnostic criteria and attending regular follow-up at pediatric rheumatology. After excluding other causes of chronic arthritis such as malignancy, infections, systemic inflammatory, and metabolic diseases, these patients were accepted as having JIA at the time of diagnosis. The healthy group comprised children and adolescents who were accompanying individuals visiting the university hospital.

Inclusion criteria for the JIA group were: (a) diagnosed with JIA based on International League of Associations for Rheumatology diagnostic criteria¹³ by a pediatric rheumatologist, (b) aged between 10 and 17 years old, (c) consenting to participate in the study. Exclusion criteria were: (a) difficulty in cooperation, (b) presence of neurological, pulmonary, orthopedic, and cardiovascular problems that affect the physical condition, (c) not having undergone any surgery in the last 6 months, (d) concomitant autoimmune or inflammatory disease.

Inclusion criteria for the healthy group were: (a) aged between 10 and 17 years old, (c) consenting to participate in the study. Exclusion criteria were: (a) difficulty in cooperation, (b) presence of cardiovascular, pulmonary, orthopedic, and neurological problems that affect physical condition, (c) not having undergone any surgery in the last 6 months, and (d) having any rheumatic disease.

Ethics

The ethics committee of non-interventional clinical research of Pamukkale University approved that there was no ethical problem in conducting this study at the meeting number of 60116787-020/92287 dated December 24, 2019. Participants were given verbal information about the study and signed written consent.

Measures

All evaluations were conducted by the same researcher under consistent test conditions. All participants’ demographic data, as well as disease-related information for JIA, were recorded. The functionality level was evaluated with the Childhood Health Assessment Questionnaire, and physical fitness level with the Brockport Physical Fitness Test Battery. The evaluations were conducted in a single session using face-to-face interviews, each lasting approximately 45 minutes.

Childhood Health Assessment Questionnaire (CHAQ)

Childhood Health Assessment Questionnaire is developed to evaluate functional abilities in children. It consists of 30 questions with 8 subsections (dressing, eating, reaching, arising, walking, grip, hygiene, activity). The scale also includes assistive device use, device use, pain, and general well-being. The original CHAQ showed excellent internal reliability (Cronbach’s alpha = 0.94), with a mean inter-item correlation of 0.6. The test–retest reliability, studied at a 2-week interval, revealed virtually identical scores measured on the 2 occasions (0.96 versus 0.96; P > .9 by paired t-test).¹⁴ The Cronbach’s alpha value of the Turkish version of the CHAQ was 0.7 for 6/8 (75%) domains of the CHAQ, excluding getting up (0.67) and eating (0.66). The intra-class correlation coefficients for the 8 CHAQ domains showed poor reproducibility with a median of 0.04 (range −0.5 to −0.4).¹⁵

Brockport Physical Fitness Test Battery

Brockport Physical Fitness Test contains 27 different tests. These tests evaluate the individual’s health-related physical fitness. It is possible to create a personalized test battery from these tests according to the individual’s disabilities and/or age groups among children and adolescents aged 10-17, both with and without disabilities.¹¹ The test battery created for this study includes the following tests: (a) skinfold thickness measurement (calf, triceps, subscapular), (b) dominant hand grip strength, (c) push-up test, (d) sit and reach test, (e) trunk lift test, (f) shoulder stretch test, (g) curl-up test, (h) PACER 20 m test.

Sample Size

The G Power V.3.1.9.4 (University of Kiel, Kiel, Germany) was used to determine the appropriate sample size. In the power analysis performed based on the “General health” subsection score of the Child Health Questionnaire in the reference article,¹⁶ the effect size was found to be high (d = .757). Through power analysis, it was calculated that 58 participants enrolled in this study (29 children/adolescents with JIA, 29 healthy children/adolescents) would provide a 95% confidence interval and 80% power.

Statistical Analysis

Statistical Package for the Social Sciences version 22.0 for Windows (IBM Corp., Armonk, NY, USA) was used in data analysis. Continuous variables were stated as mean ± standard deviation and median (minimum–maximum) values, categorical variables as n (%). The suitability of the variables for normal distribution was evaluated with the Shapiro–Wilk test. Independent samples t-test and Mann–Whitney U test were used to compare independent group differences. Chi-square and Fisher exact tests were performed to examine differences between categorical variables. In the statistical test results, the significance level was P < .05.

Results

Participant Flow

A total of 125 people, 84 with JIA and 41 healthy children/adolescents, were invited to this study. In the JIA group, 26 patients did not agree to participate in the study, and 23 patients could not be reached. In the healthy group, 6 people did not want to participate in the study. No injuries were reported during the evaluations.

Consequently, the study was completed with 35 children/adolescents with JIA (mean age 13.40 ± 2.31 years) and 35 healthy controls (mean age 12.94 ± 2.31 years).

Baseline Data

The mean height of the participants with JIA was 156.82 ± 11.66 cm, the mean body weight was 51.15 ± 14.45 kg, and the mean body mass index was 20.48 ± 4.26 kg/m². The mean height of healthy participants was 153.42 ± 13.83 cm, the mean body weight was 49.31 ± 13.00 kg, and the mean body mass index was 20.61 ± 3.22 kg/m². The groups were similar to each other in demographic data (P > .05, Table 1).

Table 1.

Demographic Characteristics of the Participants

Variables	JIA Group (n = 35)	Healthy Group (n = 35)	P
	Mean ± SD	Mean ± SD
Age (years)	13.40 ± 2.31	12.94 ± 2.31	.403**
Height (cm)	156.82 ± 11.66	153.42 ± 13.83	.411**
Body weight (kg)	51.15 ± 14.45	49.31 ± 13.00	.577*
Body mass index (kg/m2)	20.48 ± 4.26	20.61 ± 3.22	.886*
	n (%)	n (%)
Sex (female/male)	19(54.3)/16 (45.7)	21 (60)/14 (40)	.629***
Dominant hand (right/left)	35 (100)/0 (0)	34 (97.1)/1 (2.9)	1.000£

*Independent samples test.

**Mann–Whitney U-test.

***Chi-square test.

^£Fisher exact test.

JIA, juvenile idiopathic arthritis.

Disease-related data of children/adolescents with JIA are shown in Table 2. According to their diagnoses, the distribution of children/adolescents with JIA participating in the study is as follows: 17 were oligoarticular, 4 were RF+ polyarthritis, 5 were systemic JIA, and 9 were enthesitis-related arthritis (Table 2).

Table 2.

Disease-Related Data of Children/Adolescents With Juvenile Idiopathic Arthritis

Variables	JIA Group (n = 35)
	n	%
Family history  Yes  No	23 12	65.7 34.3
Medicine  No  NSAII  Methotrexate  Biological therapy	7 5 18 5	20 14.3 51.4 14.3
First symptom  Swelling in joints  Pain in joints  High fever + rash  Uveitis  Difficulty walking  Morning stiffness  Bruising on hand	9 1 5 2 2 5 1 1	25.7 42.9 5.7 5.7 14.3 2.9 2.9
First joint involvement  No involvement  Bilateral knee  Unilateral knee  Bilateral ankle  Unilateral ankle  Bilateral wrist  Unilateral wrist  Unilateral hip  Lumbar  Unilateral PIP	2 1 1 8 3 3 1 2 2 1 2	5.7 31.4 22.9 8.6 8.6 2.9 5.7 5.7 2.9 5.7
Morning stiffness  Yes  No	11 24	31.4 68.6
Consanguineous marriage  Yes  No	5 30	14.3 85.7
Type of JIA  Oligoarthritis  RF+ polyarthritis  Systemic JIA  Enthesitis related arthritis	17 4 5 9	48.6 11.4 14.3 25.7

n, number of cases; %, percent; PIP, proximal interphalangeal joint.

Intergroup Comparison Results

As a result of the comparative analysis, there was a statistical difference in dressing (P = .008), eating (P = .011), reaching (P = .001), arising (P = .001), walking (P = .001), grip (P = .016), hygiene (P = .011), activity (P < .001) subsections and total score (P < .001), pain (P < .001) and general well-being (P < .001) of CHAQ and dominant hand grip strength (P = .037), trunk lift test (P = .018), curl-up (P < .001), PACER 20 m test (P < .001), and shoulder stretch (P < .001) tests of the Brockport physical fitness test battery in favor of healthy children/adolescents (Table 3).

Table 3.

Comparison Results of Functionality and Physical Fitness Levels of Children/Adolescents with JIA and Healthy Controls

Variables	JIA Group (n = 35)		Healthy Group (n = 35)		P
	Median (Min/Max)	Mean ± SD	Median (Min/Max)	Mean ± SD
Skinfold thickness -right triceps	14.0 (6.5/28)	14.21 ± 5.99	15.0 (3/27)	14.82 ± 4.74	.465**
-Left triceps	14.0 (5/31)	14.14 ± 5.75	15.0 (4/24)	14.65 ± 4.21	.671*
-Right subscapular	10.0 (5/20)	10.59 ± 4.39	10.0 (5/25)	10.91 ± 4.25	.675**
-Left subscapular	10.0 (5/22)	10.82 ± 4.53	11.0 (5/24)	11.54 ± 4.34	.377**
-Right calf	15.0 (4/31)	16.30 ± 6.81	14.0 (4/24)	13.77 ± 4.29	.068*
-left calf	15.0 (4/33)	16.50 ± 7.63	14.0 (2/24)	13.95 ± 4.41	.093*
Curl-up test	12.0 (0/26)	13.80 ± 6.77	21.0 (0/100)	26.68 ± 17.40	<.001**
Push-up test	4.0 (0/20)	5.11 ± 5.73	3.0 (0/40)	5.68 ± 8.58	.611**
Dominant hand grip strength	15.6 (6.8/33.86)	17.09 ± 8.18	19.8 (10.93/43.7)	21.25 ± 8.53	.037**
Trunk lift	24.0 (9/35)	24.47 ± 6.25	27.0 (14/38)	27.77 ± 5.02	.018*
PACER test (20 m)	9.0 (0/22)	9.77 ± 5.20	32.0 (8/88)	33.34 ± 18.94	<.001**
Sit-and-reach test (right)	124.0 (90/140)	121.60 ± 10.71	125.0 (112.5/140)	125.45 ± 5.99	.158**
Sit-and-reach test (left)	123.5 (90/138.5)	120.93 ± 10.82	124.5 (99/141)	124.50 ± 7.40	.160**
		n (%)		n (%)
Shoulder stretch -Pass -Fail		17 (%48.6) 18 (%51.4)		33 (%94.3) 2 (%5.7)	<.001***
CHAQ-Dressing	0 (0/3)	0.62 ± 1.08	0 (0/1)	0.05 ± 0.23	.008**
Eating	0 (0/3)	0.31 ± 0.75	0 (0/0)	0.00 ± 0.00	.011**
Reaching	0 (0/3)	0.48 ± 0.88	0 (0/0)	0.00 ± 0.00	.001**
Arising	0 (0/3)	0.37 ± 0.73	0 (0/0)	0.00 ± 0.00	.001**
Walking	0 (0/2)	0.40 ± 0.69	0 (0/0)	0.00 ± 0.00	.001**
Grip	0 (0/3)	0.54 ± 0.95	0 (0/2)	0.11 ± 0.40	.016**
Hygiene	0 (0/3)	0.31 ± 0.75	0 (0/0)	0.00 ± 0.00	.011**
Activity	0 (0/3)	0.71 ± 1.12	0 (0/0)	0.00 ± 0.00	<.001**
Total score	0.25 (0/2.88)	0.47 ± 0.67	0 (0/0.25)	0.02 ± 0.05	<.001**
Pain	20 (0/100)	31.17 ± 26.77	0 (0/0)	0.00 ± 0.00	<.001**
General well-being	20 (0/100)	31.17 ± 26.56	0 (0/0)	0.00 ± 0.00	<.001**

CHAQ, Childhood Health Assessment Questionnaire; JIA, juvenile adiopathic arthritis; Min, Minimum; Max, Maximum.

*Independent samples t-test.

**Mann–Whitney U test.

***Chi-square test.

Discussion

In the present study, children/adolescents with JIA demonstrated lower performance compared to their healthy peers in muscular and cardiovascular capacity tests (curl-up test, PACER 20 m test, trunk lift test, dominant hand grip strength test, and shoulder stretch test). However, they were at similar levels to healthy peers in push-up test, skinfold thickness, and lower extremity flexibility. Their functional abilities are more impaired, and they experience higher levels of pain and lower levels of general well-being compared to their healthy peers.

Children with JIA show lower participation in both daily living activities and physical activities compared to their peers, starting from a young age. These children may often fail to participate in recreational sports and daily physical activities because they do not have sufficient muscle strength, flexibility, aerobic capacity, endurance, or physical fitness levels.⁴

In the literature, many researchers have assessed the physical fitness levels of children and adolescents with JIA using various tests. These studies have highlighted that using a standardized assessment battery is crucial and suitable for evaluating the physical fitness of this population and also underlined that the results should be supported by other studies involving larger participant groups.^9,12,17 When reviewing the literature, we observed that studies frequently assess physical fitness levels primarily with aerobic capacity. In our current study, we utilized the Brockport Physical Fitness Test battery, a standardized tool that comprehensively evaluates physical fitness across multiple dimensions, including muscular endurance, flexibility, aerobic capacity, and subcutaneous fat thickness.

Takken et al,¹⁷ in their review, reported that the VO₂ peak levels of JIA were 21.8% lower compared to healthy individuals. Kwon et al⁸ found significant differences between the healthy group and JIA in muscle strength (back muscle strength, grasping power), muscle endurance (sit-ups), lung capacity, body composition, and functional ability. Children with JIA demonstrated lower physical capabilities. Risum et al⁹ showed that children with JIA had lower muscle strength (hand grip evaluations, isometric and isokinetic knee) and lower bone mineral density compared to their healthy peers. There was no significant relationship between cardiorespiratory fitness and body composition. Nesbitt et al¹⁰ revealed that children with JIA engaged in lower levels of daily moderate physical activity compared to healthy controls. The researchers also noted that peak VO2 values decreased with age and tended to be lower in females. They recommended considering age and sex factors when assessing children with JIA. In parallel with the literature, children with JIA had lower physical fitness compared to healthy individuals in the present study. Growth delays and reduced physical activity levels in JIA contribute to decreased muscle strength.⁸ The activity level of children with JIA is influenced by several factors, including disease severity, the child’s motivation, family expectations, and disease management. Overprotectiveness from families, overly restrictive attitudes toward childhood activities, and excessive support in daily activities may have a negative effect on the development of children’s gross motor skills.¹⁸ These children may engage in less physical activity compared to their healthy peers. Therefore, we hypothesize that the physical fitness of children with JIA is diminished relative to their peers, and their endurance in trunk flexor/extensor muscles is likely lower. However, upon examining the results of the push-up test, both groups had very low numbers of repetitions. This finding led us to consider that the push-up test might be challenging for this age group. Therefore, both groups struggled to complete the test, resulting in similar outcomes.

Patti et al¹² studied a total of 56 children, including 39 healthy and 17 JIA. They evaluated physical fitness using a fitness test battery that included assessments such as the finger touch test, Abalakov test, sitting test, hand grip strength test, and sit-and-reach test. Consistent with our study, they found no difference between healthy children and those with JIA in the sit-and-reach test. It’s common for children with JIA to experience symptoms such as pain, joint involvement, and morning stiffness.¹⁹ For this reason, we anticipated that the flexibility of these children would be lower compared to their peers, but the results did not align with our expectations. This outcome may be attributed to the inherent flexibility typically observed in children, regardless of whether they are healthy or have a chronic disease. Patti et al¹² observed differences in right and left-hand grip strength between children with JIA and healthy children. Similarly, our study found significant differences in favor of the healthy group when comparing dominant hand grip strengths. A pilot study suggested that this difference might be linked to the pain levels experienced by children with JIA.²⁰ The lack of investigation into the reasons behind the decrease in grip strength can be viewed as a limitation of our study. In the present study, we observed that the aerobic fitness of children with JIA was poorer compared to healthy controls. Many studies have consistently reported lower aerobic fitness levels in children with JIA compared to their healthy peers, which supports our findings.^17,21,22

Body composition is influenced not only by daily energy expenditure but also by individuals’ eating habits.²³ In our study, we did not observe differences in skinfold thickness between the groups. We attribute this finding to the decreased physical activity during the pandemic period and changes in eating habits. Studies emphasize the importance of creating exercise opportunities to enhance physical fitness in children with JIA.^24,25 Given the adverse effects of the pandemic, we advocate directing healthy children towards exercise to improve their physical fitness levels.

CHAQ scale is developed to evaluate functional abilities in children.¹⁴ Based on the academic search engine Scopus recommended by Pediatric Rheumatology International Trials Organization, the CHAQ is used in nearly 2000 studies related to JIA.²⁶ Therefore, we utilized the CHAQ scale in the current study. None of the participants were using assistive devices. Upon examining the functional level evaluations of children/adolescents with JIA and healthy controls, we found significant differences in all sub-parameters favoring the healthy group. This result indicates that the functional levels of children/adolescents with JIA were poorer than those of healthy children. Oliveira et al²⁷ conducted a comprehensive study involving a total of 6639 participants, including 3315 healthy and 3324 JIA, from various countries. They found that the CHAQ scores were low in healthy participants. Our study’s findings are consistent with the results of this large population study.

In JIA, existing literature examines various aspects of physical fitness, with a predominant focus on aerobic capacity. In contrast, the present study distinguishes itself by comprehensively incorporating all parameters of physical fitness testing, including flexibility, muscle strength, aerobic capacity, and body composition. This comprehensive approach is a strength of the present study. However, there are some limitations in the present study. The first of these is that no information was obtained about the participants’ physical activities and regular exercise habits. Secondly, the study includes patients from all 4 subtypes of JIA. This may have influenced the results. If patients with a single type of JIA had been included, more accurate and specific data related to that JIA type could have been provided with a more homogeneous group. Thirdly, the total participation rate for the study was 41.7% in JIA patients and 85.4% in healthy controls. Since the patients were attending school, they did not want to spend time on evaluation in order not to miss more classes. We think that this rate is higher in children/adolescents with JIA because they miss more classes due to their disease than healthy individuals. This situation may cause underestimation or overestimation of the results.

Given the current condition of children with JIA, we emphasize the importance of a comprehensive assessment of their physical fitness across all parameters. We recommend using JIA-specific test batteries tailored to the disease and its subtypes. We advocate for the development of specific physical fitness assessments for JIA and its various subtypes in future studies.

Conclusion

In the present study, children/adolescents with JIA demonstrated lower performance compared to their healthy peers in muscular and cardiovascular capacity tests (curl-up test, PACER 20 m test, trunk lift test, dominant hand grip strength test, and shoulder stretch test). Their functional abilities are more impaired and they experience higher levels of pain and lower levels of general well-being compared to healthy peers.

Funding Statement

This study was supported by Pamukkale University Scientific Research Projects Coordination Unit through Project numbers 2020SABE015.