Introduction

Standing up from a chair is so routine that we rarely think about it—yet it’s a fundamental movement that provides important insights into our mobility and musculoskeletal health . The sit-to-stand (STS) test is widely used by clinicians and researchers to evaluate how easily someone can perform this everyday action. In this article, we’ll take a closer look at the biomechanics behind the STS test and introduce MAI Motion ’s innovative markerless motion capture technology, which makes analyzing this movement easier and more accessible for both professionals and patients. By streamlining the assessment process, MAI Motion is helping healthcare providers gain a clearer understanding of human movement.

The Biomechanics Behind Standing Up

While standing up may feel effortless, it actually requires a coordinated series of movements. First, there’s the flexion momentum phase, where you lean forward to shift your weight over your feet—essential for preparing your body to rise. Next is the momentum transfer phase, as your hips and knees begin to straighten, powering your body upwards. The extension phase follows, when your legs fully extend, and finally, stabilization occurs as you regain balance in a standing position.

Throughout each phase, your hip, knee, and ankle joints play key roles. The way you bend and straighten these joints—smoothly and in control—helps keep you balanced and generates the strength you need to stand. Researchers often measure how much these joint angles change, as well as how consistent each repetition is. Variability in these movements, measured by something called the coefficient of variation (CV), can reveal subtle issues such as muscle weakness, joint pain, or compensatory habits. That’s why the STS test is such a valuable tool for identifying movement impairments and guiding treatment.

Streamlining the Test: Why Fewer Repetitions Can Be Better

Traditionally, the STS test asks participants to stand up and sit down five times in a row. However, new research shows that doing just three repetitions can deliver nearly the same quality of information.

Recent studies have demonstrated that the three-repetition protocol (3x) is just as reliable as the traditional five-repetition version (5x) for evaluating joint movement and variation. With fewer repetitions, the process is less tiring—especially important for older adults or people with mobility challenges. This streamlined approach makes the assessment quicker and more comfortable, but still provides clinicians with accurate, meaningful insights into a person’s movement patterns.

Thanks to advances like MAI Motion’s solution, these shorter, easier tests can now be done without any loss in data quality. It’s a win-win: patients experience less fatigue and are more likely to participate fully, while clinicians save time and still get the detailed information they need.

Clinical Benefits and Future Potential

The sit-to-stand test is used across a variety of healthcare settings, from orthopedic clinics to rehab centers. MAI Motion’s markerless motion capture technology brings this assessment into the modern era, using video from standard cameras to capture detailed 3D data on how a person moves. There’s no need for special markers or bulky equipment, making the process easier on patients and more practical in clinics.

With this technology, clinicians can accurately identify movement difficulties, track recovery progress, and tailor treatment plans—all with greater precision and convenience. The simplified three-repetition STS protocol further encourages participation by making the test less physically demanding, without sacrificing the depth of data collected. Looking ahead, markerless motion capture promises to personalize rehabilitation , provide real-time feedback, and improve treatment outcomes by closely tracking individual movement patterns.

Conclusion

Standing up from a chair may seem ordinary, but it offers a revealing look at our strength, balance, and mobility. MAI Motion’s markerless motion capture system has opened up new possibilities for analyzing this simple action—making movement assessment faster, easier, and more patient-friendly than ever before.

The three-repetition sit-to-stand test , now validated as an efficient alternative to traditional longer protocols, reduces strain on participants while maintaining the high-quality data clinicians depend on. Together, these innovations are helping healthcare professionals perform more insightful assessments and deliver more personalized, effective care. As markerless motion capture technology continues to improve, it will become an essential tool for understanding and supporting better human movement.