Objective: To compare physical therapy strategies involving abdominal muscle stabilization, with and without upper limb movement, in patients with sternal instability after heart surgery and during in-hospital care.Methods: This prospective, longitudinal, randomized, and comparative clinical study included 20 patients, which were divided into two groups: ARM, the arm group (n=10), and LEG, the leg group (n=10). The study involved the evaluation of scores of visual analog scales for sternal instability, pain, discomfort, functional impairment, lung function, and maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) before and after the interventions. Two protocols consisting of abdominal exercises in both groups with upper limb movements (ARM) and just abdominal activation with leg movements (LEG) were used for three weeks.Results: There were statistically significant (P≤0.01) improvements in pain, discomfort, and functional impairment scores, and in MIP (P=0.04) and MEP (P≤0.01) after intervention in both groups and just LEG showed improvement in forced vital capacity (P=0.043) and forced expiratory volume in one second (P=0.011).Conclusion: Both strategies promoted improvement in pain, discomfort, and functional impairment scores and in the values of inspiratory and expiratory pressures. Perhaps they were influenced by the time and resolution of the infection process, although exercises with upper limb movements seem to be safe in this population. The activation of the infra-abdominal muscles through leg movements seems to bring more benefits to lung function.