The 12-week program, designed to help minimally active adults with FM increase their physical activity by working toward accumulating at least 30 minutes of self-selected moderate-intensity physical activity most days of the week, produced a 54% increase in the average number of steps taken per day. Compared to the FME control group, LPA participants significantly reduced their perceived functional deficits (that is, FIQ score) and pain. Moreover, compared to FME, the LPA participants had a greater improvement on the six-minute walk (expressed as gait speed), although this difference failed to reach statistical significance. The magnitude of the post-intervention differences, expressed as percent change from LPA to FME groups, were 18% for the FIQ score and 35% for the pain VAS score. When expressed as Cohen's d
effect sizes these are indicative of medium-sized effects. Moreover, the change on the FIQ score exceeds the minimally clinically important difference of 14% recently identified [20
], suggesting that increasing physical activity via LPA produces changes on perceived physical function that are of a relevant magnitude. On the other hand, the effect of LPA on the six-minute walk test was not statistically significant (although it produced a Cohen's d
of .53). It is important to note that there was a smaller sample size available for this analysis which reduced statistical power.
In general our results are in accord with studies investigating the effects of exercise on people with FM [7
]. Specifically, the majority of studies suggest that exercise can produce mild-to-moderate benefits on aerobic endurance, strength, functional status, and quality of life [7
]. However, because the exercise interventions investigated vary so markedly in type (for example, water aerobics, traditional aerobics, T'ai Chi, strength training), frequency, intensity, and duration it is difficult to compare results across studies.
One thing seems clear from the FM exercise literature, people with FM have difficulty adhering to exercise. Indeed, in FM clinical exercise trials drop-out rates often nearly exceed 30% [for example, [8
]] suggesting that developing exercise interventions that can be sustained is perhaps as important a goal as finding the particular interventions that produce optimal benefits.
The magnitude of the effects of LPA observed in this study on perceived physical function and pain were similar to those obtained in our smaller pilot study [12
]. These effects were also generally consistent with other protocols that involve low-to-moderate intensity exercise, interventions that appear to produce the greatest level of compliance in people with FM [for example, [7
It is important to note that even though the LPA group increased their mean daily steps by 54%, it only moved them, as defined by the pedometer-determined physical activity classifications developed by Tudor-Locke and colleagues [25
], from the sedentary (<5,000 steps/day) to the low active (5,000 to 7,499 steps/day) category. Indeed, the mean steps per day at post-testing among the LPA participants were comparable to the mean daily steps observed in patients with progressive neuromuscular disease, and are significantly lower than other special populations such as diabetics, patients undergoing breast cancer treatment, and those with joint replacements [26
]. This suggests that, even with the initiation of LPA, people with FM progress only to a relatively low level of physical activity. It is important to note, however, that the trajectory of the mean step count continued to rise over the 12 weeks suggesting that, had the trial continued, their physical activity may have continued to increase. It may be that people with FM require more time to eventually reach physical activity recommendations compared to persons with other chronic conditions.
This study has limitations and strengths. First, to minimize attrition and control for the effects of increased attention, participants randomized to the FME group did receive a minimal intervention. Thus, we cannot determine how LPA compares with a traditional no treatment control group. Second, with the exception of BMI, the tender point count and six-minute walk test, the outcomes described herein were derived from self-report and may be influenced by a variety of factors, including those associated with enrollment in a clinical trial. Third, using pedometers to assess LPA is relatively crude and does not quantify other sorts of physical activities that participants may have engaged in such as cycling or water exercise. Fourth, we did not measure muscle strength during the trial so we are unable to determine whether LPA influences strength. Finally, we excluded persons with FM who had other co-morbid conditions such as uncontrolled hypertension or arthritis which may limit the generalizability of our findings. Strengths of this study include the randomized design, a relatively small drop-out rate (13%), the LPA group's adherence to standardized intervention protocol, and the relatively high rates of attendance to the group sessions.