Association Between Resting Metabolic Rate And Aerobic Capacity With Low-back-pain In Post-bariatric Surgery Patients

Low back pain (LBP) is a multifactorial complex condition that contributes significantly to disability. Obesity is a significant risk factor for LBP. Bariatric surgery (BS) is highly effective for the treatment of obesity but its effects on LBP and mechanical hyperalgesia remain unclear. PURPOSE: To determine the contributing factors associated with LBP in post-BS patients. METHODS: Post-BS patients (n = 28; 18-24 months after surgery) were divided in 2 cohorts (with LBP n = 20; 50.5 ± 5y, without LBP n = 8; 52.3 ± 7y) and examined for low back pain intensity (numeric pain rating scale), and mechanical Pressure Pain Threshold (PPT; algometer) at the lumbar region. Body mass index (BMI), body composition (DXA), resting metabolic rate (RMR; indirect calorimetry), and maximal O2 consumption (VO2peak; CPET with indirect calorimetry) were also measured. Group comparisons were performed by independent t-test, and Pearson correlation for linear relationship. To predict the effect of the independent variables on pain intensity and PPT, a linear regression was performed adjusted for age, sex, BMI, lean mass, and fat mass. RESULTS: Differences were observed for pain intensity, PPT, waist/hip ratio, lean body mass (LBM), and RMR between groups (p < 0.05). There were no statistically significant differences in age, BMI, fat mass or VO2peak between groups (p > 0.05). Low back pain intensity was negatively correlated with RMR (r = -0.49, p = 0.02), and VO2peak, (r = -0.47, p = 0.02). PPT and VO2peak (r = 0.43, p = 0.04) were positively correlated. Linear regression analysis revealed that high RMR (β = -0.57, p < 0.001) and VO2peak (β = -0.37, p = 0.02) leads to decrease in LBP intensity, accounting for 48.8% of its variance. In contrast, higher VO2peak (β = 0.47, p = 0.01) leads to an increase in PPT, accounting for 22% of its variance. CONCLUSION: Results indicate that in post-BS patients, LBP intensity is influenced by RMR and aerobic capacity while mechanical PPT is associated with aerobic capacity. - Characteristics of Post-bariatric surgery patients With LBP (n = 20) Mean (std) Without LBP(n = 8) Mean (std) P-value Age (years) 50.5(4.94) 52.3(6.84) 0.44 NPRS 4.9(1.41) 0.0(0.0) <0.001 Waist/Hip ratio 0.84(.09) 0.93(0.09) 0.023 BMI (Kg.m-2) 32.59(3.79) 32.05(2.03) 0.705 FM (kg) 31.77(8.1) 27.42(4.06) 0.07 LM (Kg) 51.25(7.1) 60.28(10.1) 0.01 RMR (Kcal.24 hr-1) 1794.9(204.04) 2042.5(127.98) 0.004 Relative Vo2peak 25.62(5.96) 28.97(6.26) 0.196 PPT (kg.cm-2) 4.49(2.97) 7.34(3.56) 0.04 This study is part of an ongoing trial-registered study and PhD thesis at the University of Porto supported by the FCT, CIAFEL(UIDB\00617\2020), ITR(LA/P/0064/2020), and S. João Academic Hospital Center (HSJ), Portugal.