Avaliação da força, resistência e flexibilidade de tronco em mulheres praticantes de corrida de rua com e sem dor lombar crônica: estudo observacional transversal

Abstract

Background: Street running is one of the most practiced physical activities worldwide. With the increase in training volume and intensity, it can lead to greater mechanical overload on the lumbar spine, favoring the development of chronic low back pain (CLBP), which has a prevalence of 22.57% in runners. CLBP may be associated with reduced strength, endurance, range of motion, and flexibility of the trunk and lower limbs. Objective: This study aimed to evaluate and compare trunk strength, endurance, and flexibility in female runners with and without CLBP, as well as to investigate the association of these variables with the presence of low back pain. Methods: An analytical cross-sectional observational study was conducted with female runners aged 20 to 50 years, participating in 5 km, 10 km, or 21 km races in Curitiba-PR (2024– 2025). Participants were divided into two groups: Chronic low back paingroup (CLBPG) and a group without CLBP (WCLBPG). They underwent ultrasound assessment of muscle thickness for the rectus abdominis (RA), external oblique (EO), internal oblique (IO), transversus abdominis (TrA), and lumbar multifidus (LM) ; isometric strength of trunk flexors and extensors via handheld dynamometry ; trunk flexor and extensor endurance through specific tests ; and lumbar spine and lower limb range of motion (ROM) and flexibility using a fleximeter, the Schober test, and the sit-and-reach test. Data were analyzed in SPSS Statistics® using the Kolmogorov-Smirnov test (5% significance level), Student t test signed-rank and Student t test independent Wilcoxon signed-rank test, and Mann-Whitney U test, in addition to network analysis to evaluate centrality and inter-relations with pain. Results: Eighty-four runners (38.52±6.78 years) were evaluated; the CLBPG was characterized by a mean pain score of 6 ± 2.35 on the Numerical Rating Scale (NRS). Groups were homogeneous regarding age, anthropometric characteristics, and training volume (p > 0.05). Significant intergroup differences were found only in the RA thickness (CLBPG: 1,06±0,13; WCLBPG: 0,98±0,17; t = 2,250; p = 0,027). Deficits were observed in flexion torque (CLBPG: 57.15 ± 21.54 N·m; WCLBPG: 59.58 ± 19.14 N·m), extension torque (CLBPG: 69.28 ± 23.43 N·m; WCLBPG: 66.53 ± 20.81 N·m), and dynamic endurance, which was lower in the CLBPG (22.83 ± 7.81 vs. 27.17 ± 7.68; p = 0.013). Lumbar extension ROM was reduced in both groups (CLBPG: 31.56 ± 9.72°; WCLBPG: 35.61 ± 19.26°). In the network analysis, flexion torque showed the highest centrality (EI = 2.156), while pain was negatively associated with the multifidus (EI = –1.641) and dynamic endurance (EI = –0.544). Conclusion: Integrated findings suggest that CLBP in female runners ismore closely related to extensor strength deficits, reduced extension mobility, and alterations in deep stabilizing muscle function than to extrinsic training factors, pointing toward possible motor control impairment in the presence of CLBP.