The present results showed that 3-month detraining almost completely reversed the improvement in physical fitness (2 mL × kg− 1 × min− 1 measured as maximum work load) that had been achieved through 12 weeks of PT-X. Furthermore, the PT-X group exhibited impaired HR-QoL, with decreased scores on all SF-36 dimensions, a moderate decrease in Role Emotional (− 13 points), as well as clinically and socially significant decreases (− 5 to − 6 points) in Role Physical, Vitality, and Social Functioning. These findings indicate that both physical fitness and HR-QoL deteriorate if PT-X-induced improvements are not preserved. In the PAP group, detraining did not affect physical fitness, but had contrasting effects on Role Emotional (improved by 6 points) and Role Physical (deteriorated by − 5 points).
Several studies among patients with cardiovascular diseases other than AF show that patients have difficulty continuing exercise and maintaining a sufficient physical activity level after finishing exercise-based cardiac rehabilitation(19, 20). We previously found that elderly patients, with permanent AF and several co-morbidities, could achieve significant improvements in physical fitness. However, our present results demonstrated that these improvements disappeared after 3 months of detraining, with the additional cost of impaired HR-QoL. Although a 3-month period of PT-X improves physical fitness in older patients with permanent AF(7). and it has been shown that older adults require a longer time to retrain physical fitness lost after detraining(21), it is rare for patients with AF to have access PT-X(22, 23). How to best maintain improvement in physical fitness is an active field of research and development(6).
Previous investigations have shown that detraining causes central and peripheral alterations in athletes and recently trained healthy individuals(24–26). These alterations are multifactorial, and include a reduced VO2max due to reduced blood volume and higher heart rate response, which reduce stroke volume and affect cardiac output(26). The peripheral alterations include reduced muscular capillarisation and oxidative enzyme activities, and a decreased arterial-venous oxygen difference and reduced oxygen delivery to the cells, which affect mitochondrial ATP production(24). Our present findings also revealed significant loss of muscular endurance, in line with previously reported results of detraining in patients with and without cardio vascular disease(27–29). Our results were comparable to those of Volaklis et al (28) and Ratel et al(29), which revealed that detraining led to reversal of improvements of VO2peak and muscular strength among patients with cardio vascular disease and in older adults(24, 25, 27–29). Our study showed that detraining had similar effects in patients with permanent AF.
Compared to after the intervention, patients in the PT-X group showed reduced HR-QoL after detraining, according to the scores on all dimensions of SF-36. In some dimensions, the post-detraining scores were lower than the scores before PT-X. In three of these dimensions, the SF-36 scores exhibited a reduction of at least 5 points, which is considered a clinically and socially relevant difference. Notably, the PT-X group showed a 13-point deterioration in the Role Emotional dimension, which is considered a moderate change(30), and which was significantly larger compared to the change seen in the PAP group.
Risom et al (6) found no evidence that PT-X improved HR-QoL. This was also our finding in our main study, in which the patients self-rated scores were similar to in the normative Swedish population of the same age range(31) Teixeira-Salmela et al (27) reported that HR-QoL increased with exercise training in the elderly population, and this increase persisted during detraining. They proposed that patients felt better about their physical abilities and, therefore, adopted a more active lifestyle. That situation differs from the situation in our present study, in which patients were asked to avoid structured exercise. Clearly, adherence to these instructions led to a reduction of HR-QoL in the PT-X group. Our results are congruent with the findings of an observational study, in which elderly individuals (> 65 years of age) participated in a detraining period after a period of structured exercise(32). The participants received instructions similar to those given in the present study, and the results revealed significant deterioration of all dimensions of the HR-QoL as measured by SF-36, as in our study(32). These findings clearly confirm that after cessation of PT-X, it is crucial to support patients to maintain their physical fitness and HR-QoL.
Our results also showed that participating in PT-X was the most important factor for improved physical fitness, and that the detraining-induced decline in physical fitness in the PT-X group can partly explain the deterioration of physical scores on SF-36. However, the PT-X group participants also exhibited declines of scores related to mental well-being and social life(33). This may indicate the importance of PT-X participation for elderly patients with permanent AF. Although the intervention part of our study confirms a benefit of PT-X among elderly patients with permanent AF and co-morbidities, the overall evidence supporting PT-X is low(6). This extended study contributes additional knowledge, and corroborates that patients require support to preserve the improvements achieved through a period of PT-X.
Methodological aspects and limitations
In this study, we investigated the impact of detraining among patients with permanent AF after a period of PT-X or PAP. Allowing patients to participate in detraining may be ethically questionable due to the high evidence of benefits from improved physical fitness. However, it is well known that it is difficult to maintain good exercise habits, and the need for support in lifestyle changes is an important issue. The present findings provide solid evidence supporting the need to continue exercising after a period of successful PT-X, and can thus serve to motivate patients to pursue this goal.