Exercise response in children with and without juvenile rheumatoid arthritis: a case-comparison study.

The primary purpose of the study was to compare the response to bicycle ergometer exercise in children with and without juvenile rheumatoid arthritis (JRA). Heart rate, exercise duration, highest work load completed, and peak oxygen consumption (peak [Vo.sub.2]) were compared. A secondary purpose of the study was to determine the relationship between peak [Vo.sub.2] and articular disease severity. Thirty children with JRA and 30 controls matched for age, sex, and body surface area (BSA) were the subjects. Peak [Vo.sub.2] was determined by an open-circuit computerized gas analysis system. Peak [Vo.sub.2], highest work load completed, exercise duration, and peak heart rate were significantly lower among the children with JRA than their respective controls. Submaximal heart rate was significantly higher for tbh children with JRA. There was no difference in resting heart rate between the two groups. There was no relationship between peak [Vo.sub.2] and articular disease severity among the children with JRA. The results suggest that aerobic conditioning programs may be indicated soon after diagnosis for patients with JRA, regardless of the severity of their articular disease. One subject with JRA and 2 control subjects reported light-headedness and dizziness, and 1 subject with JRA complained of increased knee swelling. We recommend that physical therapists monitor patients for signs of exercise intolerance and joint symptoms during exercise training sessions. [Jasso Giannini M, Protas EJ. Exercise response in children with and without juvenile rheumatoid arthritis: a case-comparison study. Phys Ther. 1992;72:365-372.]

Juvenile rheumatoid arthritis (JRA) is the most common of the pediatric rheumatic diseases, with an annual incidence of approximately 1.4 cases per 10,000 children and a prevalence of 0.5 to 1 case per 1,000 in the United States.[1-3] Chronic pain, synovitis, deformity, and growth disturbances are common manifestations of the disease.[4,5] It has been documented in the literature that children with a chronic illness are unable to tolerate as much exercise as their "healthy" peers.[6,7] Bar-Or[6,7] hypothesizes that this lower tolerance is a result of hypoactivity, which leads to deconditioning, and specific pathophysiologic factors that limit one or more exercise-related functions.

We have previously shown that peak oxygen consumption [Vo.sub.2] is significantly lower in children with JRA than in children without JRA.[8] Physical therapists prescribe exercise programs for children with JRA routinely. These exercise programs are aimed at improving range of motion (ROM), muscle strength, and cardiovascular endurance. There is, however, little quantitative information on cardiovascular response to exercise for this group of children. Characterization of exercise response in this pediatric population and comparison with a control group are essential for identification of functional exercise deficits in children with JRA. Heart rate, exercise duration, and work load are clinical variables that can then be monitored easily, to provide the clinician with useful information about the patient's functional exercise tolerance.

The primary purpose of this investigation was to characterize the exercise response of a group of patients with JRA and compare this exercise response with that of a group of healthy controls matched for age, sex. and body surface area (BSA). The variables examined were (1) heart rate (resting, submaximal, and peak), (2) peak [Vo.sub.2], (3) highest work load completed, and (4) exercise duration. We hypothesized that heart rate would be of greater magnitude in the children with JRA and that they would not be able to exercise as long as their matched controls. Additionally, we expected that our earlier findings of lower aerobic capacity and lower work load completed[8] would be confirmed in a separate and larger sample of subjects. A secondary purpose of this study was to determine the relationship between peak [Vo.sub.2], the "gold standard" for measuring aerobic conditioning, and two commonly used measures of articular disease severity. We hypothesized that a strong, inverse correlation exists between peak [Vo.sub.2] and articular disease severity. That is, a patient with more severe joint disease will be more hypoactive and thus will become deconditioned to a greater extent than a patient with less severe joint disease.

Although our previous research[8] did not support this hypothesis, we believed that the small sample size warranted further testing of our hypothesis.

Method

Our data were obtained as part of a larger study that compared exercise response and muscle performance in children with JRA and in matched controls. All data for an individual subject were collected during a single day.

Subjects

The subjects were 30 patients with JRA and 30 controls with no history of an acute or chronic illness matched by age, sex, and BSA. All patients were within 1 year of age of their respective controls (mean difference = 0.29 year); all subjects were between 7 and 17 years of age. Additionally, all patients had a BSA within 0.4 [m.sup.2] of their respective controls (mean difference = 0.04 [m.sup.2]). The patient population was recruited from the Pediatric Rheumatology Center, Texas Children's Hospital (Houston, Tex), and all patients fulfilled the 1977 revised American Rheumatism Association criteria for a diagnosis of JRA.[9]

Patients who, in the opinion of the examining physician, required a change in their current medical therapy were excluded from the study. Additional exclusion criteria were (1) insufficient lower-extremity ROM to pedal a bicycle, (2) insufficient mouth-opening capability (for the mouthpiece) attributable to temporomandibular joint involvement, (3) bilateral knee pain on resisted extension (for purposes of muscle performance testing, and (4) lower-extremity surgery in the previous 6 months. Subjects with contraindications to or special precautions for exercise, as established by the Ad Hoc Committee on Exercise Testing in the Pediatric Age Group,[l0] were also excluded. Consecutive patients (and their parents) who were scheduled to be seen by the pediatric rheumatologist and who met the criteria for diagnosis, age, and stable medical status (ie, required no change in their current medical therapy) were informed about the study and asked to participate. The controls were recruited through professional colleagues from The Texas Medical Center (Houston, Tex).

No attempt was made to control the antirheumatic drug therapy of the patients. Many of the patients were taking a combination of nonsteroidal anti-inflammatory drugs and disease-modifying antirheumatic drugs. Twenty-three patients were taking a variety of nonsteroidal anti-inflammatory agents, 8 were taking oral gold, 3 were taking injectable gold, 2 were taking low-dose prednisone, 3 were taking low-dose methotrexate, and I was taking hydroxychloroquine. Three patients were not receiving medication at the time of testing. Written informed consent was obtained from the children and their parents. Verbal assent was also obtained from the children.

Assessment of

Articular Disease Activity

A joint evaluation was performed by the same physical therapist (MJG) for all patients. Two measures of articular disease severity commonly used by clinicians and researchers were derived from the joint evaluation: (1) the number of joints with active arthritis and (2) the articular disease severity score. The joint evaluation and the articular disease severity grading were performed according to the standardized methodology used by the Pediatric Rheumatology Collaborative Study Group.11 Four clinical indexes of articular inflammation were assessed: swelling, pain on passive motion (POM), tenderness to palpation, and passive limitation of motion (LOM). A joint with active arthritis is defined as a joint with swelling or, if no swelling is present, a joint with passive LOM accompanied by either heat, pain, or tenderness. Severity of joint involvement is graded on a four-point scale (ie, 0-3) for swelling, POM, and tenderness to palpation. Swelling is graded as follows: O=no swelling, 1 = mild swelling (definite swelling, but with no loss of bony contour), 2=moderate swelling (loss of distinctiveness of bony contour), and 3=marked swelling (bulging synovial proliferation with cystic characteristics or effusion). Pain on motion and tenderness to palpation are graded as follows: O=no POM or tenderness. I = mild POM or tenderness patient complains of pain or tenderness), 2=moderate POM or tenderness (patient withdraws or changes facial expression upon joint motion c)r palpation), and 3=severe POM or tenderness (patient responds markedly to joint motion or palpation). Passive LOM was graded on the following scale: 0 = full ROM, 1 = I % to 25% LOM, 2=26% to 50% LOM, 3=51% to 75% LOM, and 4=76% to 100% LOM fibrous or bony ankylosis). The articular disease severity score is calculated by summing all the scores.

Instrumentation

An open-circuit computerized gas analysis system(*) was used to measure [Vo.sub.2]. The system consists of a 10-L spirometer that measures gas volume, an oxygen analyzer that measures oxygen concentration, and a carbon dioxide analyzer that measures carbon dioxide concentration. The air-collection equipment consisted of a two-way respiratory valve that collects the expired air, a rubber mouthpiece, a noseclip, and a flexible connecting hose to the gas analyzers (Fig. 1). Before testing a subject, the spirometer and gas analyzers were calibrated with known air volumes and gas concentrations according to the manufacturer's specifications. A Monark bicycle ergometer[dagger] was used to measure work load. The ergometer was calibrated prior to the beginning of the study and checked weekly throughout the study. Heart rate was monitored with a Narco Physiograph CMP-4A[double dagger] using a CM5 chest lead configuration.

Bicycle Ergometer Protocol

We chose cycling as an exercise in order to avoid weight-bearing stress to arthritic joints. A continuous graded bicycle ergometer exercise protocol was used, modified from the continuous graded exercise test used by James et al.12 The exercise protocol involved increasing the work load by 25-W increments every 2 minutes while pedaling at a constant rate of 60 rpm. The work loads were increased until voluntary exhaustion or until the child was no longer able to pedal at a constant rate. The starting work load was determined by the BSA of the child. The BSA was calculated from the Du Bois nomogram, using height and weight according to the following formula: Children with a BSA of less than 1.2 [m.sup.2] started at 25 W; those with a BSA greater than 1.2 [m.sup.2] started at 50 W. Each subject was given a chance to establish the pedaling rate with verbal cues from the investigator before beginning the exercise test. The investigator monitored pedaling rate with a stopwatch and verbally cued each subject periodically during the test. The seat of the bicycle was adjusted so that the subject's knee was in 15 degrees of flexion when the pedal was in the down position. The children were encouraged verbally to continue throughout the exercise procedure. During the first 2 minutes after stopping exercise, the subjects continued to pedal slowly at 20 rpm to prevent blood pooling, Heat-t rate was recorded with subjects in the seated position at 1-minute intervals at rest, during exercise, and during recovery for 10 minutes. Oxygen consumption was recorded every 20 seconds during exercise and recovery. Blood pressure was measured manually with a mercury sphygmomanometer[subsection] to monitor clinical response to exercise.

Peak [Vo.sub.2] was defined as the highest rate of [Vo.sub.2] achieved in any 20-second period. The highest work load completed was the highest rate of work that was reached and maintained for the 2-minute duration of each stage of exercise. Peak heart rate was determined for the final minute of exercise of the highest work load. Submaximal heart rate was recorded at the end of the second stage of exercise.

Reliability Testing

The test-retest reliability for the open-circuit method of determining maximal oxygen consumption ([Vo.sub.2]max) has yielded a Pearson product-moment correlation coefficient (r) of .95 with a standard error of 0.84 [mL-kg.sup.-1].min.sup.-1.[13] When the computerized gas analysis system used in our study is compared with the [Vo.sub.2]max values of a referee system Applied Electrochemistry oxygen analyzer(~~) Beckman LB-2 carbon dioxide analyzer(#) and Parkinson-Cowan CD4 gasometer(*), a Pearson correlation coefficient of .989 and a standard error of 1.1 [mL.kg.sup.-l.min.sup.-1] result, demonstrating concurrent validity.[14] This finding demonstrates that the gas analysis system used in our study yields reliable and valid measurements during maximum exercise of nondisabled adults.

The reliability of peak [Vo.sub.2] measurements in the JRA population using the computerized gas analysis system was determined in a separate group of patients performing the exercise protocol described earlier. Peak 902 Was recorded during three test trials within a 3-week period in 10 children with JRA. The mean age for this group was 10.9 year,s (SD=2.4, range=8.3-14.8). The mean disease duration was 5.5 years (SD=3.7, range=1.4-11.4), and the mean age at disease onset was 5.6 years (SD=2.5, range=1.1-8.9). The mean number of active joints was 13 (SD=12, range=0-35), and the mean articular disease severity score was 35 (SD=33, range=2-95). The means, standard deviations, and coefficients of variation of the three test trials were calculated for each subject to determine the within-subject variability and are presented in Table 1. The coefficient of variation for the group was 12.8%, and the standard error for the group was 3.4. Rothstein[15] notes that the coefficient of variation can be used to estimate the percentage of variation that can be expected in a measurement solely because of measurement error when no intersubject variability is expected and is a useful way to analyze the reliability of instrument-based measurements.

Table 1. Weans,- Standard
Deviations, and Coefficients of Variation
for Peak Oxygen Consumption" in
Patients with Juvenile Rheumatoid
Arthritis (N=10)
Patient
No.            X          SD           CV(c)
1              52.0       2.3           4.5
2              30 4       8.7          28.5
3              39.2      11.9          30.5
4              24.8       1.3           5.2
5              37.3       2.6           6.9
6              33.5       2.6           7.7
7              30.1       0.4           1.3
8              24.8       5.8          23.2
9              37.4       4.8          12.8
1 0            32.8       2.6           7.9

(a) Mean of three trials (b) Measured in mL [O.sub.2.kg.sup.-1.min.sup.-1]. (c) Coefficient of variation expressed as a percentage

The reliability Of @02 measurements in nondisabled children has been investigated using the bicycle ergometer; the mean coefficients of variation between tests ranged from 2% to 5.3%.[16,17] Cumming et[16] reported a mean coefficient of variation of 4.5% (range=2%-9%) for children exercising to exhaustion on 12 different occasions (over a 6-day period) on the bicycle ergometer. Subjects exercised 6 minutes at a submaximal work load, immediately followed by a maximal work load. Boileau et[17] reported a group mean coefficient of variation of 5.3% for the bicycle ergometer when two tests were administered within a 2-week period. Subjects were 21 boys with a mean age of 12.8 years. The bicycle test began at an initial load of 1.5 kilopond-meters, and the resistance thereafter was increased by 0.5 kilopond-meter every 3 minutes until voluntary exhaustion or until the subject could not maintain a pedaling rate of 60 rpm.

The intrasubject variability of children with chronic disease can be higher than that of children without chronic disease.[18] Measurements obtained from seven of our subjects had a mean coefficient of variation of 6.6%, which is within the range of children without chronic disease. Three subjects had variations on the order of 23% to 30% between trials. We believe that this finding may reflect variations in their articular disease during the 3-week testing period. Our data did not show any trend for trial. We chose to limit our measures to a single testing day for any one subject in order to limit intrasubject variability.

The reliability of our measurements of maximal heart rate was established in a previous study of 15 adults aged 20 to 30 years.[19] These subjects underwent maximal exercise tests once a week for a 3-week period, Heart rates were monitored continuously during the tests. Peak heart rates were calculated for the final minute of the last work load completed. The means and standard deviations of peak heart rates for each testing session were calculated. A one-way analysis of variance (ANOVA) for repeated measures on heart rate was used to compare the means, and an intraclass correlation coefficient (ICC[1,1]) was performed to determine the strength of the relationship between the three grand means of heart rate.19 The means and standard deviations for the three test sessions were 193 [+ or -] 7.2, 194 [+ or -] 9.9, and 194 [+ or -] 9.9. There were no significant differences between the means (F=0.10, df=2). Using an upper limit of + 1.00 and a lower limit of - 0.50, the ICC was -.43, indicating a very strong correlation of peak heart rates for the three test sessions. Our method for measuring heart rate yields reliable measurements.

Data Analysis

Differences in peak [Vo.sub.2], exercise duration, and heart rate (resting, peak, and submaximal) between the patients and their respective controls were tested for statistical significance using a Student's paired t test for one-tailed comparison. The distribution of paired differences was tested for normality by the Anderson-darling test prior to conducting statistical procedures that require a Gaussian distribution (as performed by the PC!INFO Retriever Data Systems version 3.0 computer program(**). The Wilcoxon matched-pairs signed-rank test was used to test for paired differences in the highest work load completed. The alpha, or Type I error, level was set at .05.

Pearson's product-moment correlation (r) was used to determine the relationship between peak [Vo.sub.2] and the number of joints with active arthritis. Spearman rank-order correlation was used to describe the relationship between peak [Vo.sub.2] and the severity score.

Results

There were no significant differences in mean age or BSA between the two groups (Tab. 2). The clinical characteristics of the patients with JRA are shown in Table 3. Three distinct types of JRA are recognized: systemic JRA, which is characterized by intermittent fever (>39.4 [degrees] C), rheumatoid rash, and arthritis; polyarticular JRA, in which five or more joints are affected with arthritis without systemic manifestations; and pauciarticular JRA, in which arthritis alone is present in four or fewer joints.[4,9] Seventeen children had polyarticular JRA, 11 children had pauciarticular JRA, and 2 children had systemic JRA with polyarnicular manifestations. The distribution of the joints with active arthritis is shown in Table 4.

Table 2. Comparison of matching
Variables Between Patients with Juvenile
Rheumatoid Arthritis (JRA) and Their
Matched Controls
                  JRA           Control
                  Group         Group
Variable          (n=30)        (n=30)        t(a)
Age (y)
   X               11.4          11.1          0.3)
   SD              2.7           2.8
   Range           7.2-17.3      7-17.4
BSA(c) (m.sup.2)
   X               1.23          1.27          0.3(b)
   SD              0.26          0.29
   Range           0.85-1.74     0.78-1.72
(a) One-tailed t test.
(b) Not significant.
(c) Body surface area.
Table 3. Clinical Characteristics Among Patients with Juvenile Rheumatoid Arthri
tis
(n =30)
                   Age at     Number of      Articular
        Disease    Disease    Joints with    Disease
        Duration   Onset      Active         Severity
        y)         y)         Arthritis      Score
X       5.3        6.1        16             48
SD      3.3        4.4        19             56
Range   0.3-13.2   0.9-15.6    0-60           0-181
Table 4. Frequency of Joints in
Patients with Active Juvenile Rheumatoid
Arthritis (n =30)
                                Percentage
Joint                           of Patients
Temporomandibular joint          6.7
Shoulder                         3.3
Elbow                           23.3
Wrist                           60.0
Fingers                         56.6
Hip                             13.3
Knee                            66.7
Ankle                           50.0
Toes                            53.3
Cervical spine                   6.7
Sacroiliac joint                 3.3

Comparisons of heart rates between the two groups are shown in Table 5. Peak heart rate attained by the patients was significantly lower than that achieved by the controls. In the patient group, peak heart rate averaged 185 bpm (SD=16, range=170-210) versus 195 bpm (SD=10, range=132-208) for the controls. The patients exercised at a significantly higher percentage of their maximal heart rate than did the controls during submaximal exercise. Submaximal heart rate in the patients averaged 176 bpm (SD=17, range=132-199) and 163 bpm (SD=16, range=135-195) in the controls. There was no difference in the resting heart rate between the two groups.

Table 5. Comparison of Heart Rate(a) (HR) Between Patients with Juvenile
Rheumatoid Arthritis (JRA) and Their Matcbed Controls
                  JRA Group     Control Group
                  (n=30)        (n=30)
Variable          X      SD      X       SD     [t.sup.b]
Resting HR        85     14      84      12     1.51
Peak HR          185     16     195      10   - 2.645(c)
Submaximal HR    176     17     163      16     3.528(c)
(a) Measured in beats per minute.
(b) Paired one-tailed t test, df=29.
(c) P < 05.

The patients achieved significantly lower peak [Vo.sub.2] than their respective controls (Tab. 6). The patients failed to exercise as long as their respective controls. The control group exercised for an average of 7.1 minutes (SD=1.4, range=4.8-10), as compared with 5.4 minutes (SD=1.6, range=2.3-9.3) for the patients.

Table 6. Comparison of Peak Oxygen Consumption [(VO.sub.2)](a) and Exercise Dura
tion(b)
Between Patients with Juvenile Rheumatoid Arthritis (JRA) and Their Matched Cont
rols
                        JRA Group       Control Group
                        (n=30)          (n=30)
Variable                X        SD     X        SD   [t.sup.c]
Peak[VO.sub.2]          32.0     8.8    36.9    6.5   -3.573(d)
Exercise duration        5.4     1.6     7.1    1.4   -4.957(d)
(a) Measured in mL [O.sub.2.kg.sup.-1.min.sup.-1.
(b) Measured in minutes.
(c) Paired, one-tailed t test, df=29.
(d) P<.05.

There was no significant correlation between peak [Vo.sub.2] measurements and (1) the number of joints with active arthritis (r= -.33) and (2) the articular disease severity score (r= -.29) among the children with JRA.

The controls were usually able to complete higher work loads compared with the children with JRA. Three patients completed higher work loads than did their respective controls, 4 patients completed the same work loads as their respective controls, and 23 patients completed lower work loads than did their respective controls (Fig. 2).

Discussion

The literature on cardiovascular response to exercise in both healthy and sick children is limited. A majority of the reported studies were conducted outside the United States, and the subjects were often athletic or their level of physical activity was often greater than that of most American children. Variation in equipment, data-collection methods, and exercise protocols as well as regional and sample differences made comparison of published normative values with values obtained from our patient sample difficult. Thus, a control group was essential in our study. The control group was not a random sample and thus may not be representative of the general population for socioeconomic status. Matching, however, was performed on the basis of age, gender, and BSA, the variables known to exert the greatest influence on exercise performance in children.[20-24]

Because of the small sample size, individual exercise variables were not compared statistically with regard to gender, age, and BSA. The mean peak heart rate for the control group, however, was consistent with heart rates previously reported by other investigators using a bicycle ergometer protocol.[12,25] The lower peak heart rate achieved in the JRA group, in combination with a lower work load achieved and shorter duration of exercise, may suggest deconditioning. Because the patient group exercised at a significantly higher percentage of their peak heart rate than did the control group while performing submaximal work, they appear to be at a lower level of conditioning. Initiation of conditioning programs for children with JRA soon after their diagnosis may, prevent the cycle of hypoactivity and deconditioning often experienced by individuals with a chronic illness.[7]

We reported, in our earlier study,[8] mean peak [Vo.sub.2] values of 33 and 47 mL [O.sub.2.kg.sup.-1.min.sup.-1] for children with and without JRA, respectiveiv. It is unclear why our two control groups achieved different mean peak [Vo.sub.2], levels. Both samples were recruited from the same geographical area, and identical protocols and equipment were used by the same observers. A possible explanation for the difference in peak [Vo.sub.2] achieved by the two control groups is sampling. It is noteworthy, however, that the conclusions of both studies were similar-the patients with JRA had significantly lower peak [Vo.sub.2] levels than did their matched controls.

The values for peak [Vo.sub.2] obtained for both groups in this study are lower than those reported in the literature for healthy children. In a recent study of aerobic and anaerobic characteristics of North American children, Washington et al[20] found mean [Vo.sub.2] values of 41 to 47 [mL.kg.sup.-1.min.sup.-1] in healthy children aged 7 to 12 years. Maximum heart rates reported by Washington et al were 191 to 196 bpm, similar to the control group heart rates in our study. Possible reasons for the differences in [Vo.sub.2] values obtained in these two studies include the use of different bicycle ergometer protocols, gas analysis equipment, and sample characteristics.

We agree with Bar-Or's[6,7] hypothesis that the lower aerobic capacity often seen in children with chronic illnesses is due to both hypoactivity and specific pathophysiological factors. Bar-Or postulates that deficient oxygen extraction from the exercising muscle or low blood flow to the exercising muscle results in a high mixed venous oxygen content and subsequently a lower aerobic capacity. This is thought to occur in conditions such as arthritis, spina bifida, and poliomyelitis, in which the skeletal muscles are atrophied.[7] No data are available for children with these conditions to confirm this hypothesis. Further research involving the assessment of metabolic variables is needed.

We did not evaluate the difference in submaximal work efficiency between the two groups; however, comparison of [Vo.sub.2] values obtained during submaximal exercise was possible in 18 pairs of subjects. In 10 pairs of subjects, the [Vo.sub.2] values were higher for the children with JRA than for the control subjects, indicating that efficiency was lower for the subjects with JRA. In 2 pairs of subjects, submaximal [V.sub.2] values were essentially the same. In the remaining 6 pairs of subjects, the [Vo.sub.2] values obtained during submaximal exercise were higher for the controls than for the children with JRA. Further study is needed during submaximal work to determine whether a difference in exercise efficiency exists between the two groups.

Low muscle force production and endurance may contribute to the low aerobic capacity observed in children with JRA.[6] Additionally, clinical observations suggest that children with JRA mav have poor mechanical efficiency attributable to joint deformity, resulting in a high metabolic cost in performing submaximal activities. We hypothesize that the child with arthritis will have to work at a higher percentage of her or his aerobic capacity than a child without arthritis during functional activities.

The use of the joint evaluation for reliable measurement of articular disease severity is supported by the literature, provided the same clinician performs the evaluation on all subjects.[11,26-28] Although the validity of the joint evaluation has not been demonstrated conclusively by scientific study, this tool is used by researchers and clinicians alike to measure and monitor ariicular disease severity.[11,26-28]

Articular disease severity does not appear to be useful for predicting peak [Vo.sub.2]. Similar to our previous study,[8] no significant correlation was found between peak [Vo.sub.2] and measures of articular disease severity. Because of the small sample size, we did not examine the relationship between lower-extremity joint involvement and peak [Vo.sub.2]. Results of this study indicate that deconditioning occurs in the patient with JRA regardless of the severity of the articular disease. Thus, intervention should occur soon after diagnosis to prevent the cycle of hypoactivity and deconditioning.

During recovery, two control subjects and one subject with JRA complained of dizziness, nausea, and light-headedness. The subjects were assisted to the supine position, and their systolic blood pressure values were found to be between 80 and 90 mm Hg. The symptoms occurred during recovery while the subjects were performing slow cycling. Blood pressure, heart rate, and signs and symptoms were monitored for 20 minutes, and all three subjects recovered within a 5- to 10-minute period. One subject with JRA reported increased knee swelling, which resolved within 24 hours. The exercise protocol involved exercising to voluntary exhaustion; thus, all subjects were monitored closely for exercise intolerance. Although exercise training sessions may be of lesser intensity than an exercise test to voluntary exhaustion, the clinical implications are that patients with JRA should be monitored closely for signs and symptoms of exercise intolerance and joint symptoms.

Conclusions

This study documented differences in exercise responses between children with and without JRA. Peak [Vo.sub.2], highest work load completed, exercise duration, and peak heart rate were significantly lower in the children with JRA than in their matched controls. Submaximal heart rates were also higher for the children with JRA. These findings suggest a lower aerobic capacity in children with JRA. The decreased aerobic capacity was unrelated to the severity, of the articular disease. This is in contrast to the commonly held belief that a patient with more severe articular disease will be more hypoactive and will become more deconditioned than a patient with less severe joint disease. Results of this study indicate that deconditioning occurs in children with JRA regardless of the severity of the articular disease. The clinical implications are that aerobic conditioning programs may be indicated for children with JRA in order to improve their exercise capacity. Intervention should occur soon after diagnosis to prevent the cycle of hypoactivity and deconditioning that commonly occurs in individuals with a chronic illness.

(*) Sensormedics Manufacturing Co, 1630 S State College Blvd, Anaheim, CA 92806. (dagger) Monark Model 5134530, Quinton Instruments Co, 3051 44th Ave W, Seattle, WA 98199. (double dagger) Narco Biosystems, PO Box 12511, Houston, TX 77061. (subsection) Baunmamometer Standley Model, WA Baum Co, Copiaque, NY 11726. (~~) Applied Electrochemistry, 735 N Pastoria Ave, Sunnyvale, CA 94086. (#) Beckman Instruments Inc, 2500 Harbor Blvd, Fullerton, CA 92634. (**) PC!INFO Retriever Data Systems, 1102 33rd Ave S, Seattle, WA 98144.

References

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M Jasso Giannini, PhD, PT, was a doctoral student, School of Physical Theraphy, Texas Woman's University, 1130 MD Anderson Blvd, Houston, TX 77030-2897, when this study was completed in partial fulfillment of her degree requirements. Address all correspondence to Ms Jasso Giannini at 3513 Telford St, Cincinnati, OH 45220 (USA). Ej Protas, PhD, PT, is Professor and Assistant Dean, School of Physical Therapy, Texas Woman's University.