Using Single Case Experimental Designs to Tailor Physiotherapy Treatment

Physiotherapists working with complex patient presentations often face a dilemma: how to determine which intervention will yield optimal outcomes for an individual. The widespread use of population-level research evidence to guide clinical practice often falls short in addressing individual cases, as individual patient responses to physiotherapy treatments can vary significantly. The structured and rigorous approach of Single Case Experimental Designs offers a valuable pathway to refining clinical decision-making and management. This article will deconstruct Single Case Experimental Designs in the context of physiotherapy, explore their benefits, examine case studies, identify ways to overcome challenges, and consider their future applications in the field.

What is a Single Case Experimental Design?

Single Case Experimental Designs (SCED) focus on systematically evaluating the effectiveness of an intervention within a single patient, employing rigorous methodological principles such as frequent outcome measurements, randomisation and blinding (where possible) to reduce bias. This ensures that the results are more reliable and valid, minimising the influence of subjective factors or external variables on the outcomes. By alternating between baseline and active treatment  conditions, for example ABACA, physiotherapists can compare the effects of the two interventions. In addition, multiple baseline designs, where treatment is introduced at different time points across behaviours, settings, or individuals, allow physiotherapists to demonstrate intervention effects while controlling for time-related changes, making them particularly useful when treatment withdrawal is impractical or unethical.

Consider a patient with chronic shoulder pain who is unresponsive to standard protocols. A physiotherapist might compare the effectiveness of two targeted interventions for this patient. For instance, manual therapy versus exercise therapy delivered to the patient over distinct timeframes, with outcome measures of pain or function recorded daily or weekly. Data analysis would reveal whether one of the interventions outperforms the other, or if a combination of the two (if tested) is more effective. Critically, physiotherapists must identify appropriate clinical endpoints and outcome measures for use in a SCED. Pain intensity scores, range of motion, strength gains, or functional capacity measures may serve as quantifiable markers. High-frequency data collection ensures variability and trends are captured accurately, providing a granular understanding of intervention effectiveness.

Benefits of SCEDs in Physiotherapy

SCEDs offer a powerful framework for evaluating and refining individual treatment plans in physiotherapy. Their structured yet flexible nature makes them especially well suited to clinical contexts where responses to treatment vary across patients and where personalised care is essential. The following outlines key advantages of SCEDs in physiotherapy practice.

Personalised intervention plans: One of the most significant advantages of SCEDs is the ability to create highly personalised intervention plans. By focusing on the individual’s response to different interventions, physiotherapists can fine-tune their approach to maximise effectiveness.

Data-driven decisions: SCEDs provide concrete data on how a patient responds to various interventions. This evidence-based approach allows physiotherapists to make informed decisions and reduce reliance on trial-and-error methods, which can be subject to observer bias from both patient and physiotherapist.

Enhanced patient engagement: Patients involved in SCEDs often report feeling more engaged and invested in their treatment, largely because these designs offer the potential to determine with greater certainty whether a specific intervention is effective for them. This heightened sense of personal relevance can improve adherence to therapy protocols and contribute to more meaningful clinical outcomes.

Longitudinal monitoring for chronic conditions: SCEDs are especially well suited to managing chronic conditions that require sustained, adaptive care. Their structured, ongoing assessment framework allows physiotherapists to track progress over time and make continuous, evidence-based adjustments in response to the patient’s evolving needs. By incorporating real-time feedback across extended periods, SCEDs help ensure that interventions remain targeted, effective, and aligned with the patient’s current functional status.

SCEDs in Physiotherapy for Musculoskeletal Conditions

A systematic review of N of 1 Trials and SCEDs in physiotherapy research highlighted their potential for evaluating interventions for musculoskeletal conditions.(Nikles et. al. 2022)   The review included 19 Single Case Experimental Designs (SCEDs) with 92 participants, and revealed that 95% of participants responded favourably to the tested interventions. However, the review also noted high risk of bias in the studies, particularly regarding limited randomisation and blinding. For example, to mitigate these risks, following SCED guidelines and employing robust methodologies is essential. Multiple baseline designs, where interventions are introduced at staggered time points across behaviours, settings, or participants, can also strengthen causal inference while maintaining ethical and practical feasibility. Despite these challenges, the findings underscore the promise of SCEDs in physiotherapy research. While SCEDs have shown promise in musculoskeletal conditions, their application can extend to other areas of physiotherapy. Conditions such as neurological disorders and respiratory issues, can also benefit from personalised clinical trial approaches.

Overcoming Challenges in Physiotherapy SCEDs

While SCEDs offer considerable advantages for personalised physiotherapy, their successful implementation requires careful planning and methodological rigour. This section outlines common challenges, such as managing bias, ensuring patient compliance, and handling complex data, and provides practical strategies for overcoming them. By anticipating these issues and applying established solutions, physiotherapists can strengthen the validity of their findings and enhance the clinical utility of SCEDs in real-world practice.

Addressing bias: To ensure the reliability and validity of SCEDs, addressing potential biases is essential. While full blinding may not always be feasible, partial blinding such as masking the treatment conditions from those analysing the data, if possible, can reduce bias. Consistency in treatment delivery is also critical; ensuring that in-clinic interventions are administered in a standardised manner (usually by the same physiotherapist) can further reduce bias.

Ensuring patient compliance: Patient compliance is vital for the success of SCEDs, especially given the structured nature of these trials. Clear and transparent communication at the outset can set realistic expectations for the patient. Explaining the purpose of the trial, the expected commitment, and how it will benefit the patient personally can help increase their engagement. Regular follow-ups and progress checks throughout the trial can not only maintain compliance but also foster a sense of partnership in the treatment process. Engaging patients in the decision-making about which treatment worked best, allowing them to provide feedback on their experience and preferences, can further enhance adherence to the chosen treatment regime.

Collecting and analysing data: The use of digital tools and structured templates for data collection such as in Google Forms and smartphone apps can streamline the process, ensuring that data is both accurate and accessible for analysis. This could potentially become overwhelming for practitioners not experienced in handling data. However, the right training and the right tools can set things up. To effectively process this data, physiotherapists should utilise appropriate statistical tools and software designed for SCEDs.

Graphical representation of trends, such as progress over time or comparing pre- and post-intervention metrics, can provide a clear and accessible way to evaluate treatment effectiveness. A range of software packages for analysing single case data are available. These packages support a variety of statistical techniques, such as calculating sample sizes, effect sizes, autocorrelation adjustments, interrupted time series analysis, randomisation tests, and other types of statistical analyses. 

Suitability for Physiotherapy 

SCEDs are gaining recognition as a critical methodology in rehabilitation research, as highlighted by Machalicek et al. (2024). These designs address the challenge of heterogeneity in patient populations by enabling the rigorous evaluation of interventions at the individual level. Unlike traditional group designs, SCEDs allow for repeated measurement of outcomes, providing high-resolution data to rigorously evaluate treatment effects. This methodology is particularly valuable in physiotherapy, where patient responses to interventions like exercise regimens or manual therapies can vary widely. By utilising SCEDs, physiotherapists can contribute to evidence generation while simultaneously enhancing clinical decision-making through personalised care strategies. The ongoing methodological advancements discussed at the 5th Cochrane Rehabilitation Methodological Meeting underscore the potential of SCEDs to bridge the gap between research and practice, promoting evidence-based, individualised rehabilitation.

Future Directions

As the demand for personalised care continues to grow, SCEDs are increasingly recognised as a valuable tool in physiotherapy. Their ability to capture individual treatment responses with methodological rigour makes them particularly well suited to the field, where patient variability is high and tailored interventions are essential. Advances in design standards and analytic techniques are helping to strengthen the evidence base for SCEDs, while shifts toward more flexible, patient-centred models of care create new opportunities for implementation in everyday practice.

Emerging technologies further enhance the potential of SCEDs by improving both data quality and accessibility. Wearable devices and mobile health applications can automate outcome tracking, allowing for continuous, real-time monitoring of patient progress. These tools reduce the burden of manual data collection and provide high-resolution insights into intervention effects. In parallel, the rise of telehealth enables SCEDs to be conducted remotely, making it easier for patients to engage in personalised trials from home. Together, these innovations can streamline SCED delivery, increase scalability, and support more adaptive, responsive models of physiotherapy care.

Ready to Get Started?

If you're a physiotherapist looking to apply SCEDs in your practice and deliver personalised, evidence-based care, N of 1 Hub offers specialised training and consulting. Our services are designed to equip you with the skills and confidence to design, conduct, and analyse these trials effectively. With hands-on guidance from our expert team, you'll be able to implement SCEDs and optimise your treatment plans for each patient.

Book a free consultation call with our team today to discover how personalised approaches can elevate your physiotherapy practice to the next level.