How to Measure Physical Activity in Children with Chronic Illness: A Researcher’s Guide

1. Introduction

Physical activity plays a critical role in the health and well-being of children with chronic illnesses, influencing everything from cardiovascular fitness to mental health and overall quality of life. While movement is important for all children, it is particularly relevant for those managing long-term medical conditions, as it can support muscle strength, mobility, metabolic function, and recovery from treatments. However, accurately measuring physical activity in this population presents unique challenges.

Children with chronic illnesses often experience fatigue, pain, or mobility restrictions that affect their movement patterns. Additionally, wearable devices must be comfortable, minimally disruptive, and compatible with medical equipment. Researchers must select the right tools and methods to ensure accurate, meaningful data collection while considering ethical concerns and participant burden.

This guide outlines best practices for measuring physical activity in pediatric patients, covering device selection, data collection strategies, and interpretation methods to enhance research reliability and impact.

2. Key Considerations for Measuring Physical Activity in Pediatric Patients

Unlike healthy children, those with chronic illnesses may exhibit high variability in activity levels due to symptoms, treatment schedules, and individual energy reserves. Researchers must account for these differences when designing studies and selecting measurement tools.

• Variability in physical activity levels
  • Movement patterns can fluctuate daily based on disease progression, pain levels, or medication side effects.
  • Some children experience fatigue-related activity reduction, requiring adjusted movement thresholds.
• Differences between disease types
  • Conditions that restrict mobility (e.g., cerebral palsy, muscular dystrophy) may require specialized movement classification techniques.
  • Conditions with fluctuating energy levels (e.g., cystic fibrosis, juvenile arthritis) may need adaptive activity monitoring strategies.
  • Cardiovascular or metabolic conditions (e.g., congenital heart disease, type 1 diabetes) benefit from combined activity and physiological tracking.
• Ethical considerations in pediatric medical research
  • Researchers must obtain informed consent from parents and assent from children, ensuring they understand the study’s purpose.
  • Study protocols should minimize participant burden, particularly for children already undergoing frequent medical evaluations.

Accounting for these factors ensures that physical activity measurement aligns with the child’s health condition and daily reality, improving data reliability and clinical relevance.

3. Choosing the Right Measurement Tools

Selecting the right wearable devices or alternative tracking methods depends on the child’s medical condition, mobility level, and ability to comply with wearing a device consistently. Some tools are more suitable than others for measuring low-intensity movement, sedentary behavior, or high-energy activities.

Accelerometers

Accelerometers are the most commonly used devices for objective movement tracking, offering real-time data on activity levels and sedentary time. They are useful for children with mobility impairments, as well as those with fluctuating energy levels.

• Best for tracking general movement patterns and sedentary behavior trends.
• Device placement matters—wrist-worn devices offer better compliance but may overestimate activity, while thigh- or waist-worn devices provide more accurate posture classification.
• Limitations: May not fully capture non-ambulatory movements (e.g., upper-body activity in wheelchair users).

Heart Rate Monitors (ECG vs. PPG)

Heart rate monitoring can provide valuable insight into exertion levels and fatigue, especially in children with cardiovascular or metabolic conditions.

• ECG-based chest monitors offer high accuracy but may be uncomfortable for long-term wear.
• PPG-based wrist sensors are more convenient but susceptible to movement artifacts, especially in young children.

Multi-Sensor Wearables

Some devices combine accelerometry, heart rate, skin temperature, and electrodermal activity, providing a broader picture of physiological responses to movement.

• Useful for tracking autonomic nervous system responses to activity.
• May help detect fatigue-related activity changes in chronic conditions like fibromyalgia or mitochondrial disorders.

Alternative Methods for Measuring Physical Activity

In cases where wearable devices are not feasible, researchers may use alternative approaches to monitor activity levels.

• Observation-based activity scoring—trained observers assess activity participation levels in clinical or school settings.
• Parent-reported activity diaries—caregivers log daily movement patterns at home, useful when device compliance is low.

By selecting the most appropriate measurement tool for the child’s condition and daily routine, researchers can ensure accurate, meaningful data collection while minimizing participant burden.

4. Best Practices for Data Collection and Compliance

Ensuring high-quality data collection in children with chronic illnesses requires careful planning. Unlike healthy children, pediatric patients may experience fatigue, discomfort, or medical limitations that affect their ability to consistently wear activity trackers. Researchers must implement strategies to maximize compliance while minimizing participant burden.

Minimizing Participant Burden

Devices should be comfortable, lightweight, and easy to wear for children with sensitivity to external stimuli or mobility impairments. Complex or intrusive devices may lead to early removal, incomplete data, or low study adherence.

• Soft, adjustable straps prevent skin irritation, especially for children with fragile skin conditions.
• Long battery life and automatic data upload reduce the need for frequent charging, which can be challenging for families managing a child’s medical care.
• Non-intrusive placement options (e.g., wrist or thigh) accommodate children with IV lines, feeding tubes, or post-surgical dressings.

Ensuring Compliance in Clinical and Home Settings

Compliance can vary depending on whether data collection occurs in a hospital, rehabilitation center, or home environment. Engaging caregivers and clinicians improves device wear time and data reliability.

• Educating parents and caregivers about the study’s importance increases motivation to ensure device adherence.
• Providing reminder tools such as text messages, study apps, or printed calendars improves compliance.
• Working with clinicians and therapists allows integration of activity monitoring into routine medical visits.

Addressing Medical Equipment Interference

Children with chronic illnesses may rely on medical devices such as insulin pumps, pacemakers, or oxygen monitors. Researchers must ensure compatibility between wearables and medical equipment.

• Choosing devices with minimal electromagnetic interference reduces the risk of disrupting medical treatments.
• Adjusting placement locations prevents overlapping sensors from affecting accuracy (e.g., using a waist-worn accelerometer instead of wrist-worn near an IV site).

By proactively addressing barriers to compliance and medical compatibility, researchers can improve data completeness and study validity in pediatric populations.

5. Interpreting Physical Activity Data in Children with Chronic Illness

Analyzing activity data in children with chronic illnesses requires adjusting for unique movement patterns, symptom fluctuations, and potential data gaps. Unlike healthy children, pediatric patients may have lower activity baselines, intermittent mobility, or fatigue-related movement reductions.

Adjusting Activity Thresholds for Pediatric Patients

Traditional physical activity guidelines may not apply to children with chronic illnesses. Researchers must define customized activity thresholds based on condition-specific movement expectations.

• Setting lower intensity cut-offs accounts for limited mobility or slower movement patterns.
• Identifying rest periods vs. inactivity prevents misclassification of fatigue-related stillness as sedentary behavior.
• Using condition-specific reference data ensures activity comparisons are clinically meaningful.

Comparing Activity Levels to Disease Progression

Tracking movement patterns over time can help monitor health trends and treatment responses in children with chronic conditions.

• Increased activity levels may indicate improved energy levels and functional recovery.
• Sudden declines in movement could signal worsening symptoms, medication side effects, or disease progression.
• Linking physical activity to symptom logs allows correlation between movement reductions and flare-ups.

Handling Missing or Incomplete Data

Missing data is common in pediatric patient studies due to device removal, medical treatments, or fatigue-related inactivity. Researchers should implement data cleaning strategies to minimize bias and improve accuracy.

• Accounting for non-wear periods by using validated algorithms to detect device removal.
• Using statistical imputation methods to estimate missing data points without overestimating activity levels.
• Comparing recorded activity levels to caregiver reports for validation when compliance is inconsistent.

By refining data analysis techniques, researchers can ensure that activity tracking provides clinically useful insights for children with chronic illnesses.

6. Designing Physical Activity Interventions for Children with Chronic Illness

Beyond measurement, wearable devices can support tailored physical activity interventions for children managing chronic conditions. Increasing movement can help improve strength, mobility, and overall well-being, but interventions must be designed to fit within medical limitations.

Modifying Activity Recommendations Based on Health Status

Unlike standard exercise guidelines, pediatric activity interventions must be individualized based on each child’s condition and functional capacity.

• Low-impact movement strategies (e.g., stretching, seated exercises) work well for children with muscle weakness or joint pain.
• Shorter, more frequent activity breaks accommodate children with limited energy reserves.
• Personalized step count goals help incrementally increase movement without overexertion.

Personalized Goal Setting for Children and Families

Setting realistic, achievable activity goals encourages long-term engagement and motivation.

• Daily or weekly activity targets should be adjusted based on symptom levels.
• Encouraging family-based activities (e.g., short walks, gentle yoga) makes movement a shared, supportive experience.
• Providing digital feedback (e.g., via an app or printed reports) reinforces positive activity behaviors.

Adapting Interventions for Clinical and Home Settings

Physical activity interventions can be implemented in hospital, rehabilitation, or home settings, depending on the child’s medical needs.

• Hospital-based interventions focus on preserving mobility during treatment and recovery.
• At-home movement programs integrate structured but flexible activities that align with daily energy fluctuations.
• School-based adaptations allow children to participate in modified PE activities or classroom movement breaks.

By designing individualized, adaptable interventions, researchers and healthcare providers can support safe, beneficial physical activity participation for children with chronic illnesses.

7. Conclusion and Recommendations

Measuring physical activity in children with chronic illnesses requires a balanced approach that considers medical limitations, participant burden, and data accuracy. Unlike healthy children, pediatric patients may have reduced mobility, variable energy levels, and medical equipment constraints, making traditional activity tracking methods less effective. By selecting appropriate wearable devices, ensuring high compliance, and tailoring data interpretation strategies, researchers can generate meaningful insights into movement patterns and health outcomes.

Key takeaways include:

• Choose the right measurement tool based on the child’s condition. Accelerometers provide objective movement tracking, while heart rate monitors help assess exertion levels.
• Account for variability in physical activity by using customized movement thresholds that reflect disease-related limitations.
• Improve compliance by minimizing participant burden—devices should be lightweight, easy to wear, and require minimal maintenance.
• Engage parents, caregivers, and clinicians to support consistent wear time and integrate activity tracking into medical care routines.
• Interpret data carefully, distinguishing between true sedentary behavior and fatigue-related inactivity to avoid misclassification.
• Design personalized physical activity interventions that fit each child’s medical status, energy levels, and daily routines.

By integrating wearable technology with clinical expertise, researchers can better understand how physical activity impacts the health and well-being of children with chronic illnesses. These insights can inform treatment plans, guide rehabilitation programs, and support long-term health improvements in pediatric patients.

Call to Action

For more guidance on selecting the best device for your study, explore Fibion’s solutions for sedentary behaviors and physical activity research.

You may also book a video call with our expert or ask for a quote.