Objective: To investigate the cardiorespiratory strain experienced by patients over a day and during different types of rehabilitation therapies during a clinical rehabilitation programme. In addition, to investigate the use of the Borg scale as an instrument to monitor exercise intensity. Design: An observational, cross-sectional study. Setting: Rehabilitation centre in the Netherlands. Participants: Eleven people after stroke (age range 20-71 years), 9 people with a lower limb amputation (age range 21-66 years) and 11 people with a spinal cord injury (age range 28-65 years). All participants were inpatients undergoing clinical rehabilitation. Main outcome measures: Frequency distribution of percentage heart rate reserve (%HRR) and length of time heart rate (HR) > 40%HRR over one day, and mean %HRR, length of time HR > 40%HRR and HR > 70%HRR during different types of rehabilitation therapies were compared with the American College of Sports Medicine guidelines for achieving an aerobic training effect. The correlation coefficient between the Borg scale score and %HRR was assessed. Results: Patients' mean HR was 114 min/day (standard deviation 92) > 40%HRR, of which 1 h was spent in therapy. In 5 out of 10 rehabilitation therapies (fitness, hydrotherapy, walking group, wheelchair group and cycling/handbike group) a mean HR > 40%HRR was reached and more than half of the time was spent > 40%HRR. A moderate correlation (R = 0.56) was found between Borg scale score and %HRR. All outcome measures showed large variation between and within patients. Conclusion: In general, patients in a clinical rehabilitation programme experience adequate cardiorespiratory strain to potentially induce an aerobic training effect. The large variation in cardiorespiratory strain, however, necessitates individual monitoring to ensure proper exercise intensity. The Borg scale was shown to be of limited value for this monitoring, and therefore the use of HR monitors during rehabilitation should be considered. © 2013 The Authors.