Characteristics of cardiopulmonary exercise capacity in adults with different degrees of obesity.

Objective: To explore the characteristics of cardiopulmonary exercise capacity in adults with different degrees of obesity through cardiopulmonary exercise test (CPET).

Methods: From September 2019 to January 2024, the data of patients undergoing CPET in the Rehabilitation Department of the Affiliated Wuxi People's Hospital of Nanjing Medical University were analyzed retrospectively. A total of 231 cases were included. They were categorized into five groups based on their body mass index (BMI): the control group (18.5 ≤ BMI < 24 kg/m², n = 28), the overweight group (24.0 ≤ BMI < 28 kg/m², n = 48), the mild obesity group (28 ≤ BMI < 35 kg/m², n = 75), the moderate obesity group (35.0 ≤ BMI < 40 kg/m², n = 47), and the severe obesity group (BMI ≥ 40 kg/m², n = 33). Collected informations on the age, gender, height, and weight of five groups of participants. The VO₂ at anaerobic threshold (VO_2AT), percentage of predicted VO_2AT (VO_2AT% Pred), peak oxygen consumption (VO_2peak), percentage of predicted VO_2peak (VO_2peak% Pred), peak kilogram oxygen consumption (VO_2peak/kg), maximum exercise power (WR_max), breathing reserve (BR), maximum heart rate (HR_max), percentage of predicted HR_max (HR_max% Pred), maximum O₂ pulse (VO₂/HR_max), percentage of predicted maximum O₂ pulse (VO₂/HR_max%Pred), maximum relative O₂ pulse (VO₂/HR_max/kg),heart rate response (HRr), forced vital capacity (FVC), ratio of forced expiratory volume to vital capacity in 1 s (FEV1/FVC), percentage of predicted forced vital capacity (FVC% Pred), percentage of predicted forced expiratory volume ratio of 1 s (FEV1% Pred), peak expiratory flow rate (PEF), maximum exercise ventilation (VE_max), maximum voluntary ventilation (MVV) and other indicators during the CPET were collected. Single factor analysis of variance was used to compare the mean of each index between groups. Spearman correlation analysis was used to analyze the correlation between BMI and various indicators.

Results: There was no statistical significance in gender composition, age, height, and exercise habit of the five groups of participants (P > 0.05). The body mass and BMI of the five groups had significant differences (P < 0.001). In terms of cardiopulmonary exercise capacity, there were statistical differences among the five groups in the overall distribution of VO_2AT (H = 37.370,P < 0.001), VO_2AT/kg (H = 34.747, P < 0.001), VO_2peak (H = 23.018,P< 0.001), VO_2peak/kg (H = 66.606, P < 0.001) and WR_max%Pred (H = 45.136, P < 0.001). There was no significant difference among the five groups in the overall distribution of VO_2AT%Pred, VO_2peak%Pred and WR_max. There were statistical significant difference among the five groups in HR_max (F = 2.443, P = 0.048), HR_max%Pred (F = 6.920, P < 0.001), VO₂/HR_max (F = 8.803, P < 0.001), VO₂/HR_max%Pred (F = 11.354, P < 0.001), VO2/HRmax/kg (F = 18.688, P < 0.001) and BR (F = 6.147, P < 0.001) and HRr (F = 9.467, P < 0.001). There were no significant differences among the five groups in RER_max (F = 0.336, P > 0.05). In terms of static pulmonary function, there were significant differences among the five groups in FVC%Pred (F = 4.577, P = 0.001), FEV1%Pred (F = 3.681, P = 0.006) and FEV1/FVC (F = 3.344, P = 0.011). There was no differences among the five groups in MVV(P> 0.05), and there were significant differences among the five groups in VE_max (P = 0.005) In terms of correlation analysis, BMI was positively correlated with VO_2AT,VO_2peak, VE_max and VO₂/HR_max, and negatively correlated with VO_2AT/kg, VO_2peak/kg,WR_max%Pred, HR_max%Pred, VO₂/HR_max%Pred, VO₂/HR_max/kg,BR and HRr. In terms of static pulmonary function, BMI was negatively correlated with FVC%Pred, FEV1%Pred.

Conclusion: With the aggravation of obesity, the maximum exercise ability of adults decreases, VO_2peak/kg and VO₂/HR_max%Pred decreases, and the breathing reserve decreases.