Background: Low cardiorespiratory fitness (CRF) is a risk factor for many chronic diseases. This study aimed to evaluate the CRF of a sample of adults with different glucose tolerance statuses to explore its relationship with early abnormal glucose metabolism according to sex.
Methods: A total of 93 participants were assigned to three groups, i.e. the normal glucose tolerance (NGT) group, impaired glucose regulation (IGR) group and new-onset type 2 diabetes mellitus (T2DM) group, through an oral glucose tolerance test. Cardiopulmonary exercise testing was performed to evaluate the participants' CRF. The physical measurements (including height, weight, systolic blood pressure [SBP] and diastolic blood pressure) and laboratory test results (including fasting plasma glucose and two-hour plasma glucose [2h-PG]) of all participants were collected. Partial correlation, multiple linear regression (stepwise method) and logistic regression were used to analyse the data.
Results: Compared to the males with NGT, those with T2DM or IGR had a lower exercise time (P = 0.044), anaerobic threshold (AT) oxygen uptake (VO2) (P = 0.009), maximum VO2/kg (P = 0.041) and oxygen uptake efficiency slope (P = 0.002). The male participants with T2DM had lower AT power (P = 0.001) than those with IGR or NGT. Compared to the females with NGT, the AT heart rate (HR) (P = 0.003), AT SBP (P = 0.002) and maximum VO2/kg (P = 0.039) were lower in the female T2DM and IGR groups. The multiple linear regression (stepwise method) analyses showed that the maximum VO2/kg (β = -0.268, p = 0.026) and one-minute HR recovery (β = -0.239, p = 0.039) of the females improved the prediction of the 2h-PG when entered in the model. The logistic analysis results indicated that the VO2 max of the male participants was related to pre-diabetes (β = -0.003, p = 0.024) and that their AT power was associated with new-onset diabetes (β = -0.053, p = 0.010). Meanwhile, the AT SBP of the female participants was related to pre-diabetes (β = 0.120, p = 0.019), and their AT HR was related to new-onset diabetes (β = -0.102, p = 0.014).
Conclusions: Low CRF is associated with abnormal glucose metabolism. The CRF is closely associated with the 2h-PG after glucose load and is an important risk factor for pre-diabetes and new-onset diabetes.