To analyze 1) the independent association of physical fitness, positive affect, and negative affect with the different dimensions of fatigue (general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue) and 2) whether the interactions of physical fitness, positive affect, and negative affect were associated with fatigue over and above the independent association.
Cross-sectional study in 420 women with fibromyalgia.
Fibromyalgia associations from southern Spain.
Physical fitness was measured by performance-based tests, and questionnaires were used to measure positive affect, negative affect, and different dimensions of fatigue (general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue). Age, body mass index, and current pain level were included as potential confounders in all analyses.
Physical fitness was independently associated with general fatigue, physical fatigue, and reduced activity (all P ≤ 0.02). Positive affect was independently associated with all fatigue dimensions (all P < 0.001). Negative affect was independently associated with general fatigue, physical fatigue, reduced motivation, and mental fatigue (all P ≤ 0.04). The interaction of overall physical fitness and positive affect was related to general fatigue and physical fatigue (all P ≤ 0.02). Women with fibromyalgia with higher levels of overall physical fitness and positive affect showed the lowest general fatigue and physical fatigue.
In women with fibromyalgia, positive affect was independently and consistently associated with all dimensions of fatigue. The combination of higher levels of overall physical fitness and positive affect might serve as a buffer against general and physical fatigue in women with fibromyalgia.