ASSOCIATION OF SEDENTARY TIME AND PHYSICAL ACTIVITY WITH PHYSICAL FITNESS IN WOMEN WITH FIBROMIALGIA: AN ISOTEMPORAL SUBSTITUTION APPROACH

Background Behaviours of people with fibromyalgia may impact their levels of physical fitness, which is a marker of physical and psychological health1,2,3. However, scarce research has studied the association of sedentary time (ST) and physical activity (PA) with physical fitness. Interestingly, increasing time in one behaviour requires decreasing time in another. Thus, it is also of interest to understand what is the theoretical impact of replacing sedentary time (ST, e.g., sitting) by light or moderate PA (LPA and MPA, respectively) as well as replacing LPA by MPA on physical fitness in fibromyalgia. Objectives To assess the association of replacing ST for different physical activity levels (i.e., ST by LPA or MPA) as well as of LPA by MPA with physical fitness in women with fibromyalgia. Methods A total of 407 women with fibromyalgia (51.87 ± 8.01 years old) participated in this cross-sectional study. ST, LPA and MPA were objectively measured with triaxial accelerometer for 7 consecutive days. Vigorous physical activity was not analysed as this is a very uncommon behaviour in the population. Physical fitness was assessed through the Senior Fitness Test Battery plus the handgrip strength test. The associations between the replacement of 30 min/day of ST with an equivalent time of LPA or MPA were tested by isotemporal substitution analyses. Body mass index and age were included as covariates. Results Replacing 30 minutes of ST with LPA was associated with better strength in upper limb (B=0.19), handgrip strength (B=0.02) and aerobic fitness (B=2.29); all p<0.03 Replacing 30 minutes of ST with MPA was related to better strength and flexibility in lower and upper limb (B ranging from 0.43 to 1.97; all p<0.02). Finally, replacing 30 minutes of LPA with MPA was associated with better strength and flexibility in lower and upper limb, aerobic fitness and balance (B ranging from 0.15 to 8.54; all p<0.04). Conclusion Replacing short time periods (30 min) of ST by PA (especially of moderate intensity) was related to better physical fitness. Moreover, to replace 30 min of LPA by MPA was related to better physical fitness. Our findings support the implementation of experimental research to better understand the extent to which replacing sedentary time (by LPA or MPA) or replacing LPA (by MPA) might enhance increase different components of physical fitness in fibromyalgia. Such findings would have direct clinical implications. References [1] Estévez-López, et al. Disabil Rehabil. 2018 Feb;40(3):329-337. DOI: 10.1080/09638288.2016 [2] Gavilán-Carrera B., et al. Arthritis Care Res. 2018 Jul. DOI: 10.1002/acr.23717 [3] Estévez-López, et al. Rheumatology (Oxford). 2017 Nov 1;56(11):2015-2024. DOI: 10.1093/rheumatology/kex302 Acknowledgement This study was supported by the Universidad Politécnica de Madrid and the Spanish Ministry of Economy and Competitiveness (I+D+i DEP2010-15639; I+D+I DEP2013-40908-R, BES-2011-047133; BES-2014 067612) and of Education (FPU 15/00002, FPU 15/00002). Disclosure of Interests None declared