Physical fitness is a marker of health and is associated with health-related quality of life (HRQoL). Identifying which components of physical fitness are associated with HRQoL in people with fibromyalgia may contribute to the development of more specific therapeutic strategies.
The 2 aims of this study were to examine the association of different components of physical fitness (ie, flexibility, muscle strength, speed and agility, and cardiorespiratory fitness) with HRQoL and to determine the extent to which any association between the components of physical fitness and HRQoL were of clinical relevance to women with fibromyalgia.
A cross-sectional design was used.
This study included 466 women with fibromyalgia from southern Spain (Andalusia). The Senior Fitness Test battery and the handgrip test were used to assess physical fitness, and the 36-Item Short-Form Health Survey (SF-36) was used to assess HRQoL. Tender points, cognitive impairment, anthropometric measurements, and medication usage were also measured. First, multivariate linear regression was used to assess the individual relationship of each physical fitness test with the 8 dimensions of the SF-36. Second, a standardized composite score was computed for each component of physical fitness (flexibility, muscle strength, speed and agility, and cardiorespiratory fitness). A 1-way analysis of covariance to assess the differences in each of the 8 dimensions of the SF-36 across each physical fitness composite score was conducted. Forward stepwise regression was performed to analyze which components of physical fitness were independently associated with the SF-36 physical and mental component scales.
Overall, higher levels of physical fitness were associated with higher levels of HRQoL (regardless of the SF-36 subscale evaluated). The effect sizes for HRQoL between participants with the lowest and the highest physical fitness levels ranged from moderate to large (Cohen d = 0.53-0.90). The muscle strength composite score was independently associated with the SF-36 physical component scale, whereas the flexibility composite score and cardiorespiratory fitness were independently associated with the SF-36 mental component scale.
A limitation was that the cross-sectional design precluded the establishment of causality. Additionally, only women were included in the study, because fibromyalgia predominantly affects women.
High levels of physical fitness were consistently associated with better HRQoL in women with fibromyalgia; clinically relevant differences were demonstrated between those at extreme physical fitness levels. Muscle strength, flexibility, and cardiorespiratory fitness were independent indicators of HRQoL. These results warrant further prospective research on the potential of fitness to predict HRQoL in this population.