The aim of this study was to investigate whether post exercise carbohydrate intake improves training effect in the first postoperative days, in patients who have had a primary total knee or hip arthroplasty. Subjects were primary total hip (THA) (n=18), and total knee arthroplasties (TKA)(n=25) patients randomized to consume 30 g maltodextrin or placebo within 15 minutes after each training session as a supplement to the standard diet. The outcome measures were six minute walk test (6-MWT), number of completed training sessions, training intensity, and duration. There was no difference in the 6-MWT, number of completed training sessions, training intensity and duration between the intervention vs control group. When stratified for operation procedure, THA patients in the intervention group trained longer (26.7 ± 5.8 vs 15.2 ± 4.1 min, P = 0.017), and at an overall higher intensity (scale 1-5) (2.4 ± 1.0 vs 1.75 ± 0.8, P = 0.021) and during the training sessions with the physiotherapist (2.5 ± 1.1 vs and 1.8 ± 0.9, P = 0.044) compared with controls. In contrary, the duration of self-training was longer in the TKA control group compared with the intervention group (19.7 ± 7.0 vs 13.8 ± 3.3 min, P = 0.021). In conclusion, minor positive effects of maltodextrin were observed after hip arthroplasties, while minor negative effects of maltodextrin were observed after knee arthroplasties. It is unknown whether these findings are due to the low dose of maltodextrin, small number of study participants, differences in overall nutritional status, or lack of effect.