Fall injuries in older adults are a major global health problem. A large percentage of falls occur during the sit-to-stand transition. This transfer is a challenge to movement control if performed for subsequent walking towards a goal, as occurs during everyday tasks. Using objective methods to analyze the sit-to-walk transition could lead to better approaches in fall prevention interventions. This study aimed to develop an analysis system to detect and electromyographically examine the sit-to-walk transition in older people when it occurs within a free movement as part of an everyday activity. A 67-year-old participant remained in a free seated position, stood up, and walked towards a target a few meters away. Throughout the task, muscle activity of the biceps brachii, gluteus medius, vastus lateralis, and tibialis anterior was recorded bilaterally by surface electromyography. The data obtained were bounded between the beginning and end of the sit-to-walk transition, and the muscle activity during this period was explored. The analysis system used in this study is useful for detecting the transition from sit-to-stand when the transition continues with walking. This analysis method will make it possible to explore muscle function easily and to detect dysfunctionalities in everyday tasks that can be addressed to prevent falls in older people.