Relationship Between Cardiorespiratory Fitness And Glycemic Control In Individuals With Chronic Spinal Cord Injury

Abstract

Exercise is recommended for the management of cardiometabolic disease risks in individuals with spinal cord injury (SCI). However, the independent associations between cardiorespiratory fitness and glycemic control have not been established in this population. PURPOSE:To examine associations between cardiorespiratory fitness (VO2peak) and biomarkers of fasting and postprandial glucose control in individuals with chronic SCI. METHODS: Thirty-four males with SCI performed a graded exercise test on an arm crank ergometer to assess VO2peak. On a non-consecutive day, participants completed a fasted (>8-h) oral glucose tolerance test (OGTT). Serial measurements of systemic glucose and insulin concentrations at baseline and in response to the OGTT were converted into simple summary statistics: Insulin Resistance (HOMA2IR); whole body insulin sensitivity (ISIMatsuda) and glucose and insulin area under the curve (AUC). Pearson correlations were used to determine the relationship between biomarkers of glycemic control and VO2peak. Multiple linear regression was used to determine the independent relationships between these variables, using BMI as a covariate. RESULTS: The mean ± SD VO2peak was 19.3 ± 6.6 ml/kg/min and BMI was 25.6 ± 4.8 kg/m2, respectively. Seven (21%) of the participants had fasting glucose values ≥5.6 mmol/L and considered pre-diabetic. Seven (21%) of the participants had HOMA2IR values that were indicative of clinical insulin resistance (>1.8) and 21 (62%) of the participants had ISIMatsuda values indicative of impaired insulin sensitivity (<4.3). There were significant correlations between VO2peak with fasting insulin (r = -0.55, p < 0.001), HOMA2IR (r = -0.55, < 0.001), insulin AUC (r = -0.44, p = 0.009), glucose AUC (r = -0.45, p = 0.007), and ISIMatsuda (r = 0.50, p = 0.003). Correlation coefficients from multiple linear regressions indicated that 32% of variance in ISIMatsuda and 43% in HOMA2-IR can be accounted for by the combination of BMI and VO2peak, although VO2peak accounted for 25% and 30% of the variance, respectively. CONCLUSIONS: Higher cardiorespiratory fitness is associated with improved glycemic control. This finding reinforces the need for more extensive use of exercise conditioning as a tool to mitigate glycemic dysregulation and accompanying risk in individuals with SCI.