Abstract
BACKGROUND: The efficacy of exercise training for patients with cardiovascular disease is well established. Given recent changes in reimbursement patterns for cardiac rehabilitation and therefore a greater need for self-monitoring, home programs, and the like, a need exists to determine the capability of patients to regulate their own exercise intensity and assess the efficacy of self-regulated exercise. This study assessed the training responses of a group instructed to train at an intensity they perceived as "somewhat hard," and compared their responses to standardized methods of exercise prescription.
METHODS: A total of 78 patients (86% male; mean age, 56 +/- 10 years; mean ejection fraction, 64% +/- 12%) referred to a residential rehabilitation program after myocardial infarction or bypass surgery were randomized to three different groups, for which exercise intensity was prescribed using different methods. For group 1, 70% of heart rate reserve was maintained using precise, continuous electronic heart rate-controlled resistance on a cycle ergometer. Group 2 gauged their own exercise intensity according to a level they perceived as "somewhat hard" (13 on the Borg scale) and were given no feedback in terms of heart rate or work rate. For group 3, exercise intensity was determined using both objective (heart rate reserve and work rate targeted to 60% to 80% of maximal exercise) and subjective (Borg scale 12 to 14) indices. The subjects exercised daily for 1 month. Training frequency, duration, and mode were equivalent between the groups.
RESULTS: The exercise capacity of the three groups was increased significantly after the training period: 33.7% in group 1, 22.9% in group 2, and 31.2% in group 3 (P < .005 for all). Other measures of the training response also were similar between the groups, including a significant increase in work rate at a perceived exertion of 13 and maximal watts achieved. The magnitude of the training response was not different between the groups. There were no complications during training.
CONCLUSIONS: The training response was similar between the three methods used to monitor exercise intensity. Thus, patients are able to gauge their own exercise intensity reasonably when instructed to exercise at a perceived exertion of 13. This suggests that close heart rate monitoring may not always be necessary for many stable patients with cardiovascular disease to achieve the benefits of a rehabilitation program.
The benefits of exercise training for patients who have sustained a myocardial infarction (MI) and those who have undergone coronary artery bypass surgery (CABS) are well established. 1 The foundation of exercise training in cardiac rehabilitation is the exercise prescription: the mode, intensity, duration, and frequency of exercise. By convention, one of several methods is used to prescribe training intensity such that the patient's heart rate falls within a target range. Historically, it was thought that maintaining an exercise intensity within a specific heart rate range provides a training effect that is optimal, individualized, and safe. A large empirical body of literature has demonstrated the effectiveness of this approach over several decades. During this time, cardiac rehabilitation has become established as an effective therapeutic modality after an MI or CABS. 2
Despite the benefits associated with cardiac rehabilitation, however, formal programs remain elusive for most patients. 1,3 Between 80% and 90% of eligible US patients do not receive formal cardiac rehabilitation services. Furthermore, because of changes in reimbursement patterns, many patients do not get cardiac rehabilitation or receive only brief recommendations on home exercise after discharge. Moreover, an increasing number of patients are referred to cardiac rehabilitation without entry exercise testing, 4 making heart rate-based exercise prescription difficult. Studies also have shown that dropout rates for exercise programs range from 25% to 50%, 5,6 with excessive exertion demands and lack of confidence cited as two of the most important deterrents to a sustained exercise program. Finally, from a public health perspective, the emphasis has shifted recently from exercise "intensity" to "physical activity."7 This view has evolved in part from an awareness that a specific intensity is less important during an exercise program than the development of habits and a knowledge base that lead to a more physically active lifestyle in the long term. 7,8
For these reasons, there exists a need to determine exercise intensity, safety, and training efficacy on the basis of a patient's self-regulated effort in the absence of close surveillance or equipment. The current study specifically investigated whether patients enrolled in a rehabilitation program achieve training benefits when asked to exercise at an intensity commensurate with what they perceive as "somewhat hard."9 This group was provided no feedback in terms of heart rate or work load, and was compared with groups that trained within strict heart rate ranges, including one that used continuous electronic heart rate-controlled resistance on a cycle ergometer. The study objective was to determine whether a self-regulated program would yield training benefits similar to those of more traditional, heart rate-based approaches.