Journal of Pain and Symptom Management
Volume 36, Issue 1 , Pages 46-53, July 2008

Physical Activity Behaviors in Individuals with Multiple Sclerosis: Roles of Overall and Specific Symptoms, and Self-Efficacy

  • Erin M. Snook, MS
    • ,
  • Robert W. Motl, PhD

      Affiliations

    • Corresponding Author InformationAddress correspondence to: Robert W. Motl, PhD, Department of Kinesiology and Community Health, University of Illinois, 350 Freer Hall, 906 South Goodwin Avenue, Urbana, IL 61801, USA.

Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA

Accepted 18 September 2007. published online 25 March 2008.

Article Outline

Abstract 

Multiple sclerosis (MS) is associated with a large reduction in physical activity behavior, and emerging evidence indicates that this reduction might be correlated with symptoms and self-efficacy. The present study examined the nature of the associations among MS-related symptoms, exercise self-efficacy, and physical activity behavior in 80 individuals with a definite diagnosis of MS. Participants completed a measure of MS-related symptoms and self-efficacy and then wore an accelerometer for seven days. Both the frequency of overall symptoms and the frequency of motor symptoms had significant moderate inverse relationships with physical activity behavior (r=−0.47, P<0.0001 and r=−0.49, P<0.0001, respectively). Additionally, exercise self-efficacy was significantly and moderately correlated with physical activity (r=0.39, P<0.0001) and had significant and moderate inverse relationships with overall symptom frequency (r=−0.40, P<0.0001) and motor symptom frequency (r=−0.30, P=0.008). Path analysis demonstrated that both overall symptoms and motor symptoms had direct effects on physical activity as well as indirect effects on physical activity by way of self-efficacy. Such results suggest that the management and monitoring of MS-related symptoms may play an important role in encouraging physical activity adoption and maintenance in individuals with MS.

Key Words: Multiple sclerosis, symptoms, self-efficacy, exercise

 

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Introduction 

Multiple sclerosis (MS) is a chronic and progressive demyelinating disease of the central nervous system that affects an estimated 400,000 adults in the United States.1 The pathophysiology of MS involves demyelination and a variable degree of injury to axons in the brain, spinal cord, and optic nerve. This impedes the conduction of electrical potentials in the central nervous system and manifests as diverse motor, somatosensory, brainstem, visual, cerebellar, cognitive, and affective symptoms.2

Several theories of the symptom experience have identified symptoms as direct and indirect influences on performance and behavioral outcomes in persons with chronic diseases.3, 4, 5, 6, 7 Indeed, symptoms have been inversely associated with activities of daily living (e.g., work, personal care, and social interaction) in individuals with MS.8, 9, 10, 11, 12, 13 For example, motor symptoms (e.g., arm and leg weakness, spasms, and balance problems) were moderately and inversely correlated with activities of daily living associated with fine and gross motor tasks (e.g., eating, dressing, bathing, and walking) in individuals with MS.10 Secondary analysis of data from 686 persons with MS indicated that emotional symptoms exhibited a moderate and inverse relationship with overall activities of daily living, and the effect was partially mediated by personal attributes and social support.12

Another behavioral outcome of the symptoms of MS might be physical inactivity. Physical activity levels are exceedingly low among individuals with MS14 and some researchers have noted that MS-associated symptoms might directly or indirectly influence physical activity behavior.15 We are aware of two studies that have explicitly examined symptoms as correlates of physical activity in MS. The first study adopted social-cognitive theory16, 17 as a guiding framework and examined the associations among symptoms, self-efficacy, and physical activity in a sample of 196 individuals with MS.18 The primary findings were that individuals with MS who reported a greater number of symptoms during the past 30 days engaged in lower amounts of physical activity. This relationship was partially accounted for by self-efficacy, consistent with social cognitive theory whereby symptoms act as physiological and affective sources of efficacy information.16, 17 The second study examined the relationship between worsening of symptoms and physical activity in a sample of 51 individuals with MS.19 The primary findings were that the worsening of symptoms across a three to five-year period of time was associated with lower levels of physical activity; this relationship was not accounted for by depression, disability status, or MS disease course.

Importantly, there were two major limitations of those previous investigations. The first limitation was the measurement of symptoms using either a poorly defined scale18 or a dichotomous outcome variable,19 rather than using a well-established scale for measuring symptoms such as the MS-Related Symptom Scale (MS-RS10). The second limitation was the global examination of symptoms rather than consideration of specific types of symptoms (e.g., motor, sensory, and emotional symptoms) as correlates of physical activity.

The present study is novel in that it addressed limitations of previous research that examined the relationships among symptoms, self-efficacy, and physical activity in individuals with MS. Two novel features are that we used a well-established measure of symptoms (i.e., MS-RS10) and examined the frequency of both overall and specific types of symptoms as correlates of physical activity. An additional novel feature was that we examined the possibility that both overall and specific symptoms would exhibit indirect associations with physical activity by way of self-efficacy. We expected that overall symptoms and motor symptoms, in particular, would exhibit the strongest inverse relationships with physical activity, and that self-efficacy would partially account for any relationship between symptoms and physical activity.

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Methods 

Participants 

Participants (n=80) were recruited through support group meetings of the Greater Illinois and Indiana State Chapters of the National Multiple Sclerosis Society (NMSS). The inclusion criteria included self-reported diagnosis of MS, being relapse free during the past 30 days, and ability to ambulate with minimal assistance (i.e., those who walk with or without a cane). The mean age of the sample was 49.0 years (SD=11.4) and the sample was primarily female (n=65, 81%), Caucasian (n=76, 95%), employed (n=47, 59%), married (n=50, 63%), and well educated (some college education n=21, 26%; college graduate n=38, 48%). The mean duration since MS diagnosis was 10.1 years (SD=7.9) and the mean Expanded Disability Status Scale score was 3.9 (SD=1.8). The sample consisted of 62 individuals with a self-reported diagnosis of relapsing-remitting MS, 15 individuals with a self-reported diagnosis of secondary progressive MS, one individual with a self-reported diagnosis of primary progressive MS, and two individuals with a self-reported diagnosis of benign MS.

Measures 

Symptoms. Symptoms were measured using the MS-RS.10 The MS-RS assesses the frequency of occurrence of 26 symptoms (e.g., fatigue, blurred vision, numbness) during the previous four weeks. The items are rated on a six-point Likert-type scale, where 0=“never,” 1=“almost never,” 2=“occasionally,” 3=“usually,” 4=“almost always,” and 5=“always.” The MS-RS items yield five subscales of Motor (e.g., “balance problems”), Brainstem (e.g., “double vision”), Sensory (e.g., “numbness”), Mental/Emotional (e.g., “anxiety”), and Elimination (e.g., “increased urinary frequency [day]”) symptoms. The MS-RS items further yield an overall or composite symptom score. The overall and subscale scores are interpreted such that higher scores represent more frequent symptoms experienced during the past four weeks. There is evidence for the reliability and validity of the composite and subscale scores on the MS-RS.10, 20 Within the current study the internal consistency estimate for the MS-RS subscales ranged from 0.54 (Brainstem subscale) to 0.89 (Mental/Emotional subscale) and the internal consistency estimate was 0.90 for the MS-RS total score.

Self-Efficacy. Self-Efficacy was measured using the Exercise Self-Efficacy (EXSE) scale.21 The EXSE scale contains six items measuring self-efficacy for continued physical activity participation over incremental periods of time using a 10-point scale ranging from 0% (not at all confident) to 100% (highly confident). The first item states “I am able to participate in physical activity three times per week at a moderate intensity, for 20+ minutes without quitting for the NEXT MONTH.” Each of the next items asks the same question with a one-month increase (i.e., two to six months) per item. Scores from the EXSE provide a reliable and valid measure of self-efficacy for continued physical activity participation21, 22 and this scale has been previously used in persons with MS.18 The internal consistency estimate was 0.99 for the EXSE scale in this study.

Physical Activity. We measured physical activity using the ActiGraph single-axis accelerometer (model 7164 version, Health One Technology, Fort Walton Beach, FL). This accelerometer is a small (2.0×1.6×0.6 inches) and lightweight (1.5 ounces) device that provides an objective, valid, and reliable measure of physical activity for individuals with MS.23, 24 The Actigraph is powered by a 2430 lithium coin cell battery and contains a single, vertical axis piezoelectric bender element that generates an electrical signal proportional to the force acting on it. Acceleration detection ranges in magnitude from 0.05 to 3.2Gs and the frequency response ranges from 0.25 to 2.5Hz. Motion outside normal human movements is rejected by a band-pass filter. The acceleration/deceleration signal is digitized by an analog-to-digital converter and numerically integrated over a preprogrammed epoch interval. At the end of each data collection interval, the integrated value of movement counts is stored in RAM and the integrator is reset. The monitor is programmed for start time and data collection interval and data retrieved for analysis via a PC interface and software provided with the accelerometers. The movement counts are a summation of positive and negative accelerations measured during a cycle period that is established along with start time during an initialization phase. The counts represent a quantitative measure of activity over time and are linearly related to the intensity of a participant's physical activity during a cycle period. The epoch in this study was one minute. Downloaded data were entered into Microsoft Excel for data processing. The activity counts were summed across each day and the counts from the seven days were then averaged, yielding accelerometer data in total daily movement counts. Within the current study the intraclass correlation was 0.94 for the seven days of accelerometer data.

Procedure 

The procedure was approved by the University of Illinois Urbana-Champaign Institutional Review Board. All participants provided written informed consent and then completed the MS-RS and EXSE and wore an accelerometer for seven consecutive days. Participants received $10 remuneration for completing the study.

Data Analysis 

The data were analyzed using SPSS 15.0 and AMOS 7.0. We initially conducted a Pearson product–moment correlation analysis of composite and subscale scores of the MS-RS, EXSE scale scores, and accelerometer counts using SPSS. The guidelines of Cohen25 of 0.1, 0.3, and 0.5 were used for judging the magnitude of the correlations as small, moderate, and large, respectively. After establishing bivariate associations, we conducted multiple linear regression analysis in SPSS for examining the independent contribution of the MS-RS subscales for explaining variation in accelerometer counts and conducting mediator analyses. The initial standard multiple regression analysis of the independent contribution of the MS-RS subscales involved regressing accelerometer counts on scores from all five MS-RS subscales using a direct entry. The next multiple regression analysis of possible mediator effects involved regressing accelerometer counts on composite and specific subscale scores of the MS-RS in Step 1 and then entering EXSE scores in Step 2. The reduction in the magnitude of the beta-coefficient between symptoms and physical activity from Step 1 to Step 2 provided an indication of mediation such that a nonsignificant coefficient that approached zero indicated full mediation. We conducted path analysis in AMOS 7.0 as a further examination of EXSE scores as a possible mediator of the relationships between composite and subscale scores of the MSSR and accelerometer counts.

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Results 

Descriptive Statistics 

Mean scores and standard deviations of the measures included in the study are presented in Table 1. We initially compared the mean accelerometer counts in this study with previous research that had a demographically similar sample of individuals with MS.26 Participants in the current study accumulated fewer activity counts (d=−0.26) than reported in that previous research. We further compared EXSE scores between the two studies, and the participants in this study had similar self-efficacy scores compared with previous research (d=−0.04). One last comparison of the MS-RS total score in the current study with that of previous research10 indicated minimal differences in overall symptoms scores (d=0.05).

Table 1. Means, Standard Deviations, and Ranges of the Study Measures
MeasureMSDRangeComparison: M(SD)
MS-RS1.70.70–51.7 (0.7)10
MS-RSM1.80.90–52.4 (1.0)11
MS-RSB1.30.70–51.4 (l.l)11
MS-RSS2.21.20–51.8 (1.2)11
MS-RSME1.51.20–51.6 (1.0)11
MS-RSE1.61.10–51.9 (1.2)11
EXSE65.837.00–10064.4 (36.0)18
ACCEL194,940107,82239,993–691,233223,489 (114,543)18

MS-RS=MS Related-Symptom Scale (26 items); MS-RSM=Motor subscale (seven items); MS-RSS=Brainstem subscale (four items); MS-RSS=Sensory subscale (four items); MS-RSME=Mental/Emotions subscale (three items); MS-RSE=Elimination subscale (four items); EXSE=Exercise Self-Efficacy Scale; ACCEL=Daily Accelerometer Activity Count.

Bivariate Correlation Analysis 

Table 2 contains the Pearson product–moment correlations among composite and subscale scores of the MS-RS, EXSE scores, and accelerometer counts. The MS-RS total score and the Motor subscale of the MS-RS exhibited statistically significant and strong correlations with activity counts (r=−0.47, P<0.0001 and r=−0.49, P<0.0001, respectively). The other five subscales of the MS-RS exhibited statistically significant, but moderate relationships with daily accelerometer activity counts (r=−0.23, P=0.04 to r=−0.36, P=0.001). We further note that EXSE scores were significantly and moderately correlated with daily accelerometer counts (r=0.39, P<0.0001), the MS-RS total score (r=−0.40, P<0.0001), and the MS-RS Motor (r=−0.30, P=0.008), Brainstem (r=−0.23, P=0.04), Sensory (r=−0.26, P=0.02), and Mental/Emotions (r=−0.34, P=0.002) subscale scores.

Table 2. Correlations Among the Study Variables
Variables12345678
l. MS-RS
2. MS-RSM0.836b
3. MS-RSB0.610b0.419b
4. MS-RSS0.790b0.558b0.478b
5. MS-RSME0.560b0.366b0.322b0.297b
6. MS-RSE0.663b0.437b0.232a0.464b0.113
7. EXSE−0.398b−0.299b−0.232a−0.258a−0.341b−0.202
8. ACCEL−0.473b−0.490b−0.248a−0.361b−0.234b−0.275a0.385b

MS-RS=MS Related-Symptom Scale; MS-RSM=Motor subscale (7 items); MS-RSS=Brainstem subscale (4 items); MS-RSS=Sensory subscale (4 items); MS-RSME=Mental/Emotions subscale (3 items); MS-RSE=Elimination subscale (4 items); EXSE=Exercise Self-Efficacy Scale; ACCEL=Daily Accelerometer Activity Count.

a=Correlation significant at 0.05 level;

b=Correlation significant at 0.01 level.

Multiple Regression Analysis: Types of Symptoms and Physical Activity 

We conducted a multiple regression analysis whereby accelerometer counts were regressed on scores from all five MS-RS subscales using a standard direct entry, and the overall regression model was statistically significant, F(5,74)=5.07, P<0.0001. The adjusted R2 indicated that the MS-RS subscales accounted for 21% of the variance in accelerometer counts. Inspection of the regression coefficients indicated that only the Motor subscale was a statistically significant predictor of accelerometer counts (β=−0.39, P=0.004); the regression coefficients were small in magnitude and not statistically significant for the Brainstem (β=−0.01, P=0.94), Sensory (β=−0.10, P=0.45), Mental/Emotions (β=−0.05, P=0.63), and Elimination (β=−0.05, P=0.67) subscales.

Multiple Regression Analysis: Mediation Analyses 

The multiple regression analysis involved regressing accelerometer counts on the composite score of the MS-RS in Step 1 and then entering EXSE scores in Step 2. The results are reported in the top portion of Table 3. MS-RS scores explained significant variation in accelerometer counts in Step 1 (β=−0.47). Both MS-RS (β=−0.38) and EXSE (β=0.23) scores explained variation in accelerometer counts in Step 2. The magnitude of the regression coefficient for MS-RS was attenuated, but still statistically significant when accounting for EXSE in Step 2. Those variables explained 27% of variation in accelerometer counts.

Table 3. Summary of Regression Analysis for Overall Symptoms and Exercise Self-Efficacy Predicting Accelerometer Counts (n=80)
Step VariableBSE BβR2R2 ChangeF Change
Overall symptoms
Step 1 0.220.2222.23b
MS-RS−2,852.24605.02−0.47a
Step 2 0.270.054.79a
MS-RS−2,292.23643.77−0.38a
EXSE6,856.553,134.580.23b

Motor symptoms
Step l 0.240.2424.39a
MS-RSM−8,782.341,778.20−0.49a
Step 2 0.300.066.81b
MS-RSM−7,382.821,796.62−0.41a
EXSE7,683.122,933.410.26b

B=Unstandardized coefficient; SE B=Standard error of unstandardized coefficient; β=Standardized coefficient; MS-RS=MS-Related Symptom Scale composite score; MS-RSM=MS-Related Symptom Scale Motor score; EXSE=Exercise Self-Efficacy Scale.

aP<0.05.

bP<0.001.

The next multiple regression analysis involved regressing accelerometer counts on the Motor subscale score of the MS-RS in Step 1 and then entering EXSE scores in Step 2. The results are provided in the lower portion of Table 3. MS-RS Motor subscale scores explained significant variation in accelerometer counts in Step 1 (β=−0.49). Both MS-RS Motor subscale (β=−0.41) and EXSE (β=0.26) scores explained variation in accelerometer counts in Step 2 and the magnitude of the regression coefficient for the MS-RS Motor subscale was attenuated, but still statistically significant when accounting for EXSE in Step 2. Those variables explained 30% of variation in accelerometer counts.

Path Analysis 

Path analysis was undertaken for further examining the direct and indirect associations of the MS-RS composite score and the MS-RS Motor subscale score with accelerometer counts by way of self-efficacy. The top model presented in Fig. 1 demonstrated that the MS-RS total score had a direct effect on self-efficacy (γ=−0.40) and physical activity (γ=−0.38), and there was a direct effect of self-efficacy on physical activity (β=0.23). The indirect effect of overall symptoms on accelerometer counts via self-efficacy was −0.09. The bottom model in Fig. 1 illustrated that the MS-RS Motor subscale had a direct effect on self-efficacy (γ=−0.30) and physical activity (γ=−0.41), and there was a direct effect of self-efficacy on physical activity (β=0.26). The indirect effect of Motor symptoms on accelerometer counts via self-efficacy was −0.08. Accordingly, the path analysis further indicated that self-efficacy only partially accounted for the relationships between overall and motor symptoms with accelerometer counts.

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Discussion 

This study examined the frequency of overall and types of symptoms as direct and indirect correlates of physical activity in individuals with MS. There were strong negative relationships between the frequency of overall symptoms and motor symptoms with physical activity, indicating that more frequent overall and specific motor symptoms were associated with reduced physical activity levels. Those relationships were partially accounted for by self-efficacy, indicating that overall and motor symptoms may be indirectly associated with physical activity behavior by operating as a source of efficacy information in those with MS.

This is the first study that directly examined the relationships of both overall and specific types of symptoms (i.e., motor, brainstem) with an objective measure of physical activity behavior in individuals with MS. Using a reliable and valid measure of symptoms, namely the MS-RS,10 we reported that more frequent overall symptoms and symptoms associated with motor function (i.e., weakness, balance problems) were negatively correlated with physical activity behavior in persons with MS. Our findings are consistent with previous research where individuals reporting a greater number of MS symptoms during the past 30 days18 or a worsening of symptoms over a three to five-year period19 engaged in lower amounts of physical activity. Novel features of the current study include the use of an accepted measure of symptoms that enabled a focus on overall and specific symptoms as correlates of physical activity. Therefore, the present study has advanced the understanding of symptoms as a correlate of physical activity behavior in persons with MS.

The negative relationships between overall and motor symptoms with physical activity were only partially explained by self-efficacy. That is, more frequently occurring overall and motor symptoms were associated with lower self-efficacy, and lower self-efficacy was directly associated with lower levels of physical activity behavior. Those relationships are consistent with previous research18 and social cognitive theory.17 Based on social cognitive theory,17 symptoms are likely informing one's self-efficacy by providing information based on the physiological and affective nature of MS-related symptoms. This suggests that MS-related symptoms may, in part, explain the significantly lower levels of physical activity among those with MS by way of reduced self-efficacy for physical activity.

There is evidence that physical activity and exercise are associated with improvements in MS-related symptoms such as fatigue,27, 28, 29 spasticity,30 muscle weakness,29, 31 and mobility limitations.32, 33, 34 Physical activity is often suggested as a method of managing symptoms35, 36 and may provide an important alternative or adjuvant for pharmacological treatment. Based on our previous research18, 19 and results of the present study, we believe that symptoms might play an equally important and significant role in the adoption and maintenance of physical activity and exercise behavior in persons with MS. Effective symptom management and appropriate titration of physical activity based on changes in symptoms would seem to be important for initiating and maintaining participation in physical activity among those with MS. We emphasize that individuals with MS are largely inactive,14 and the initiating and maintenance of physical activity in persons with MS is in line with primary goals of improving quality of life, maintaining mobility, and forestalling functional limitations and disability associated with the progression of MS.1

This study is not without limitations. The cross-sectional design does not allow for inferences about the temporal relationship between symptoms and physical activity. The convenience sample did not fully reflect the demographics of MS, as this sample primarily consisted of Caucasian women. Another limitation is that the participants were recruited through MS support group meetings and this introduces a treatment variable that might be eliminated in future studies by recruiting individuals through the same physician or MS center. One final limitation is that we did not collect information about the use of disease-modifying drugs, steroids, and symptomatic medications that might influence motor function and physical activity behavior.

We believe that our results have important implications for future research. One area of future research involves examining the relationship between symptoms and physical activity using a longitudinal design that would facilitate the study of temporal dynamics of symptoms as an antecedent and consequence of physical activity. An additional area of future inquiry of the relationship between MS-related symptoms and physical activity could be achieved by focusing on more than one component of the symptom experience (i.e., intensity, timing, level of perceived distress, and quality3, 6). For example, one would expect that taking into account the potential multiplicative nature of symptom frequency and intensity would result in a better understanding of the relationship between symptoms and physical activity as compared to looking at frequency or intensity in isolation. The role of symptoms in physical activity behavior of individuals with MS is an area of burgeoning research potential with implications for promoting physical activity and thereby enhancing the lives of persons with MS.

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PII: S0885-3924(08)00097-3

doi:10.1016/j.jpainsymman.2007.09.007

Journal of Pain and Symptom Management
Volume 36, Issue 1 , Pages 46-53, July 2008

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