When her brother received a heart bypass at the age of only four, Linda Park saw up close for the first time just how fragile, yet resilient, the human heart is. That family shock introduced her to the world of cardiology long before she enrolled in college, and would later define her career as a cardiac nurse and scientist.

Years later, working as a cardiac nurse practitioner, Park constantly saw the same pattern in the clinic. A patient would undergo major heart surgery or a procedure like stent implantation, doctors would refer them to cardiac rehabilitation, and they would either completely give up on the program or quit after a few weeks. At check-ups, the same problems returned: lack of physical activity, weight gain, poor blood pressure regulation, fatigue, and a drop in motivation.

"It hurt me the most to see that many patients simply didn't have the tools to manage their symptoms and disease progression themselves," describes Park regarding her early experience. "When they came to rehabilitation regularly, they physically blossomed. But as soon as they stopped exercising and returned to a sedentary lifestyle, the old risks returned. It became clear that we had to find a way to keep them active outside hospital gyms as well."

Why cardiac rehabilitation is crucial, especially for the elderly

Cardiac rehabilitation is today the standard recommended for all patients after suffering a heart attack, bypass surgery, stent implantation, heart valve replacement, and other complex cardiovascular procedures. It is a structured program that most often lasts about 12 weeks and includes supervised physical activity, education on nutrition and lifestyle changes, and psychosocial support.

It is particularly important for older patients, who often feel fear of exertion and insecurity during daily activities after hospitalization. In the supervised environment of the rehabilitation center, they exercise with light weights, participate in aerobic training adapted to their capabilities, and perform targeted stretching and balance exercises. Medical staff continuously monitor blood pressure, heart rhythm, and general condition, which increases the patient's sense of security.

A well-structured rehabilitation program can improve gait, endurance, and muscle strength, and reduce the number of falls and fractures. Patients move more easily around the house and outside, use stairs more safely, walk longer without shortness of breath, and resume roles in the family and community. On the other hand, those who do not include rehabilitation in their recovery have a higher risk of recurrent cardiovascular events, faster loss of physical function, but also the development of depression and feelings of helplessness.

The gap between recommendations and reality

Despite strong professional recommendations, data show that only a minority of patients even start a cardiac rehabilitation program. In large analyses covering elderly patients, participation hovers around one-quarter of the total number of those eligible for the program, and among those enrolled, only every fourth or fifth makes it to the completion of all scheduled weeks.

The reasons are manifold and usually overlap. Many are still professionally active and find it difficult to coordinate exercise times with work. Others care for grandchildren or older family members and have no one to entrust with care. Some patients live far from the rehabilitation center, so traveling every second or third day is a logistical and financial burden. There are also psychological barriers – from shame about one's own physical fitness to the belief that "the surgery already solved the problem" and that additional exercise is unnecessary.

For the healthcare system, this is a huge missed potential. Studies show that regular participation in cardiac rehabilitation reduces the risk of readmission and cardiovascular death, improves quality of life, and reduces long-term treatment costs. However, the benefits of the program cannot be realized if patients give up as soon as they leave the hospital or after completing only a part of the planned exercises.

Digital technologies as a bridge between hospital and home

In search of new ways to motivate, Park began to wonder if technology that has already become part of everyday life – smartphones, smartwatches, fitness trackers, and home blood pressure monitors – could help patients stay active in the long term. At the same time, the development of wearable devices and remote health monitoring has made a big leap: today it is possible to monitor heart rate, rhythm, step count, calories burned, and even sleep quality in real time.

Digital monitoring has two key advantages. The first is the objective recording of activity and vital signs, without relying on the patient's memory or subjective impression. The second is the possibility of almost instantaneous feedback – whether through an application that displays graphs and warnings, or through automated SMS messages and reminders that encourage the patient to move or remind them of goals agreed with the medical team.

Park wanted to know if such digital tools could become an extension of cardiac rehabilitation even after the patient stops coming to the gym. Could a simple pedometer, a mobile application, and personalized text messages motivate people not to give up moving as soon as they face the first obstacles in everyday life?

NIH study: pedometer, app, and messages as additional motivation

To answer these questions, in 2021 she launched a randomized study with the support of the National Institutes of Health. The study included sixty women and men with an average age of 68, all with a recent cardiac diagnosis or procedure. All participants were encouraged to participate in a standard cardiac rehabilitation program, and in addition, they received pedometers to track their step count.

Patients were randomly assigned to two groups. The first, the control group, received a pedometer and occasional educational SMS messages reminding them of the importance of increasing daily steps and regular activity. The second, the intervention group, received access to a mobile fitness application and additional motivational and educational messages for two months after the end of formal rehabilitation, in addition to the same base.

Of the 60 included patients, 51 completed all 12 weeks of cardiac rehabilitation. The analysis showed that precisely the group with the mobile application and enhanced digital support was physically more active even after the end of the official program. On average, they recorded 8,860 steps per day, while the control group recorded 6,633 steps. In other words, the digital intervention resulted in roughly a quarter more steps compared to usual support.

"Our study confirmed that a digital intervention combining a wearable device and an application on a mobile phone can increase the level of physical activity after cardiac rehabilitation," Park pointed out after the results were published. Steps are not viewed just as a number on a screen – they are a simple indicator, understandable to patients, of how much they really move from day to day.

What more steps mean for the heart and daily life

Increasing the average number of steps by a thousand or two a day might not sound spectacular at first glance, but in cardiology, such changes make a big difference in the long run. Regular walking contributes to improving cardiorespiratory fitness, lowering blood pressure, and better blood lipid levels. It also helps better regulate sugar in people with diabetes, which is extremely important because diabetes often occurs together with cardiovascular diseases.

For older patients, every additional step often means greater independence too. More movement is associated with better balance and a lower risk of falls, and the ability to independently go shopping, walk in the park, or visit friends has a direct positive effect on mental health. Many report fewer symptoms of depression and anxiety when they feel more capable and when they resume the role of an active family and community member.

Digital tools have another advantage here: they can make progress visible to patients. Charts, goals, and reminders in the app help recognize and reward even small improvements, which further encourages persistence. Instead of perceiving exercise as an abstract recommendation, patients see concrete figures changing from day to day.

From individual study to broader digital strategy

Encouraged by the results, Park continued to expand her research. In newer, multicenter projects, she compares patients from urban areas with those from rural environments to better understand how the availability of the internet, smartphones, and rehabilitation centers affects the success of digital interventions. She pays special attention to how to adapt the content of messages, applications, and virtual programs to people who may not have grown up with technology and who initially feel insecure in a digital environment.

One of the approaches she relies on is group online exercise, such as virtual yoga or joint stretching sessions. Such activities not only provide patients with guided exercise in their own homes but also alleviate social isolation, common among people who have survived severe heart events. A sense of belonging to a group, even via a screen, helps many stay motivated and persist in lifestyle changes.

The role of digital technologies does not end there with motivation for movement. In an ideal scenario, data from glucometers, blood pressure monitors, heart rate monitors, and other home devices would be automatically sent to the patient's electronic health record. Doctors and nurses would have insight into parameters almost in real time and could spot a worsening of the condition earlier – for example, a gradual weight gain in patients with heart failure or more frequent episodes of arrhythmia.

Such a more complete picture would allow for more precise and timely therapy adjustments, a reduction in the number of emergency admissions, and a better sense of security for patients. Although not all healthcare systems are technically and organizationally ready for the full integration of home measurement devices with hospital systems yet, this is precisely the standard that researchers like Park strive for.

Broader trend: from hospital program to hybrid care

The research led by Park fits into a broader global trend of digitalization of cardiac rehabilitation. Across the world, there are more and more programs combining classic, gym-led exercises with home exercise supported by apps, video calls, and smart devices. Such hybrid models strive to bridge typical obstacles – distance to the center, lack of time, health crises like pandemics – while maintaining a high level of safety and expert supervision.

Numerous recent studies show that digital interventions, including wearable devices, activity tracking apps, and telehealth platforms, can increase the number of completed rehabilitation sessions and improve adherence to recommended exercises. Many analyses also record a drop in readmissions and a better subjective experience of quality of life in patients who use such technologies compared to those who rely exclusively on classic outpatient check-ups.

Digital solutions simultaneously raise questions of equitable access to care. Not all patients participate equally in digital programs – differences in age, education, income, digital literacy, and internet availability can create a new gap in health outcomes. Therefore, an increasing number of professional guidelines emphasize that digital cardiac rehabilitation must be a supplement, not a replacement for physically accessible programs, and that active work must be done to remove digital barriers.

What these findings mean for patients and the healthcare system

The story of Linda Park and her studies is at first a story about technology, but at its core, it remains a story about human motivation. Patients who feel included, informed, and supported – whether through a conversation with a nurse in the gym or through a message arriving on a mobile phone screen – are more likely to keep healthy habits even after immediate supervision stops.

For healthcare systems, including the Croatian one, the experiences of such research represent a valuable source of inspiration. Introducing pedometers, fitness apps, and structured SMS reminders into existing cardiac rehabilitation programs could relatively simply extend the "reach" of hospital teams to the patient's home. This could especially help those living far from large centers or having limited travel options.

Park believes that right now is an extremely exciting time for digital health. Technology is advanced enough to enable continuity of care, but it is also widespread enough that most patients have at least some device that can be included in the program – a smartphone, a watch, or a simple wristband that counts steps. It is crucial, however, that digital solutions are not perceived as a gimmick, but as a serious addition to standard care, designed in collaboration with cardiologists, nurses, physical therapists, and the patients themselves.

If such an approach is consistently implemented, the future of cardiac rehabilitation could look significantly more flexible than today: part of the exercises will take place in the hospital gym, part in the living room guided by an instructor on a screen, and part through independent walks in the neighborhood with a discreet but constant digital reminder that every step is important for heart health.