Table 4.

Main outcomes of the included studies.

Author	Main outcomes
Borges et al.[13], 2016	Functional capacity was maintained in the intervention group. A significant difference in functional capacity was also found in intergroup analyses at hospital discharge.
Cacau et al.[7], 2013	Intervention group showed lower reduction in functional performance, decreased pain score, higher energy level, shorter hospital length of stay, and higher 6MWT distance.
Herdy et al.[14], 2008	Intervention group had shorter time to endotracheal extubation, decreased incidence of pleural effusion, atelectasis, pneumonia, and atrial fibrillation or flutter, and reduced hospital length of stay.
Hirschhorn et al.[15], 2007	Intervention group had significantly higher 6MWT distance at hospital discharge.
Hojskov et al.[16], 2019	No significant differences between groups in 6MWT. Anxiety and depression were decreased in intervention group.
Lordello et al.[9], 2020	No significant difference was found in the total number of steps between the groups. However, self-reports indicated better motivation in the intervention group.
Mendes et al.[17], 2010	Intervention group presented significantly higher parasympathetic HRV values, global power, non-linear HRV indexes and mean RR. Higher values of mean HR, LF (sympathetic activity), and the LF/HF (global sympathovagal balance) were found in control group.
Pantoni et al.[14], 2016	Intervention group had increased exercise time, better thoracoabdominal coordination, increased ventilation during walking, increased SpO2 values at the end of walking, and reduced dyspnea rate.
Silva et al.[15], 2017	Reduction of MIP in both groups, while the maximum expiratory pressure did not reduce in the intervention group. There was no change in the MRC and decrease in spirometry values in both groups at hospital discharge.
Stein et al.[16], 2009	Intervention group maintained MIP measured at 7 and 30 days postoperatively, while it was significantly reduced in the control group. 6MWT distance was higher 7 days after cardiac surgery in intervention group. VO2 peak at day 30 was also higher in the intervention group.
Tariq et al.[17], 2017	In the intervention group, there was an improvement in dyspnea, respiratory rate, and oxygen saturation.
Ximenes et al.[2], 2015	Intervention group maintained functional capacity at hospital discharge measured by 6MWT, while control group had a significant decrease.
Windmoller et al.[23], 2020	Functional capacity decreased in both groups, without significant difference in the intervention group. ICU length of stay was lower in the intervention group. In both groups there was a decrease in maximal inspiratory and expiratory pressures, as well as in the 1-min sit-to-stand test on the fourth postoperative day compared to the preoperative period.
Zanini et al.[22], 2019	The 6MWT distance on the sixth postoperative day was significantly higher in groups which included early ambulation and upper and lower limbs exercise, remaining higher at 30 days post-discharge. Peak VO2 on day 30 was also higher in in the same groups. All groups achieved similar recovery of lung function

6MWT=6-minute walk test; HF=high frequency; HR=heart rate; HRV=heart rate variability; ICU=intensive care unit; LF=low frequency; MIP=maximal inspiratory pressure; MRC=Medical Research Council; RR=R-R intervals; SpO2=saturation of peripheral oxygen; VO2=oxygen uptake