Background and Objective: Osteoporosis is widely recognized as a prevalent skeletal condition among women after menopause, resulting in reduced bone mineral density and a heightened risk of fractures, and reduced quality of life. Impaired back extensor muscle function can exacerbate postural deformities, pain, functional limitations, and reduced social participation. Despite growing evidence on muscle function, the specific roles of back extensor muscle strength and endurance in different quality of life domains remain unclear. This study aimed to investigate the associations between back extensor muscle strength and endurance and multiple domains of quality of life in postmenopausal women with osteoporosis.
Methods: In this cross-sectional study, 56 postmenopausal women aged 50–70 years with osteoporosis (T-score ≤ -2.5) were recruited via convenience sampling from an outpatient osteoporosis clinic. Back extensor muscle strength was measured using a back–leg–chest dynamometer, and endurance was assessed with the Timed Loaded Standing Test. Quality of life was evaluated using the QUALEFFO-41 questionnaire covering pain, physical function, social function, general health, and mental health. Descriptive statistics (mean ± SD) summarized demographic and clinical characteristics. Pearson’s correlation coefficients (PCC) were used to examine relationships between muscle function and quality of life domains, with significance set at p < 0.05.
Results: Participants had a mean age of 64.09 ± 6.42 years and a mean BMI of 26.34 ± 12.3 kg/m². Muscle endurance showed significant negative correlations with pain (PCC = -0.622, p < 0.001), physical function (PCC = -0.501, p < 0.001), social function (PCC = -0.409, p = 0.007), mental health (PCC = -0.441, p = 0.003), and total quality of life score (PCC = -0.628, p < 0.001). Muscle strength had weaker negative correlations with pain (PCC = -0.350, p = 0.023), physical function (PCC = -0.452, p = 0.003), and total quality of life (PCC = -0.351, p = 0.023), and was not significantly associated with other domains. Neither strength nor endurance showed significant associations with general health (p > 0.05).
Conclusion: Back extensor muscle endurance is more strongly and broadly associated with multiple quality of life domains than muscle strength in postmenopausal women with osteoporosis. These findings highlight the importance of prioritizing endurance training in rehabilitation programs to enhance physical, psychological, and social well-being and to promote functional independence in this population.