The abdominal drawing-in maneuver (ADIM) is a core stability exercise in which the abdominal walls are pulled inwards to increase abdominal pressure(1, 2). The ADIM can provide lumbar stability by activating transversus abdominis and internal abdominal oblique (TrA/IO)(3). This exercise has been recommended to improve lumbar stability for preventing or reducing the risk of injury to the lumbar spine (4). However, controlling and performing consistent intensity of muscle activity of TrA/IO was difficult, especially when combined with other exercises that require motor control(2, 5). Therefore, it has been suggested to use some tools for providing feedback to participants when performing ADIM(2, 6).
Real-time visual biofeedback (RVBF) has been proposed as an effective tool for motor control and learning(7). RVBF can provide feedback through the visual input that is demonstrated on the screen during exercise(7, 8). Thus, participants can either increase motor control when performing the difficult task or decrease the time required to learn the new task(8, 9). Recently, electromyography-based (EMG-based) RVBF has the potential to be used in monitoring muscle activity(8, 9). The EMG-based RVBF was used to consistently control muscle activity during exercise(8, 9). Hence, EMG-based RVBF has been recommended for use to control the consistency of muscle activity(7–9).
Muscle activity is a result of the force generated in a muscle to stabilize posture or move the body(10). Muscle activity is recruited increasingly when people do physical activities such as exercise(11). During exercise, the muscle activities of agonist and antagonist muscles have to work together in coordination, known as muscle co-activation(10, 12). For instance, it has been found that the back and hip muscles are co-activated with the TrA/IO(6). Therefore, an increase in muscle activity of TrA/IO increases back and hip muscle activity(6). Muscle co-activation is usually found when people are kept in an upright position, such as standing, or performing exercises(13–16). Consequently, studies on muscle activity have become important to determine how people’s muscles are activated during exercise(17, 18).
The lunge position is a functional exercise that is commonly used to strengthen the hip and knee muscles(17, 19). Functional exercise is important in the rehabilitation field for improving the functional activities of daily life(18, 20). To challenge participants, the lunge position has been widely combined with other exercises to increase hip and knee muscle activity(15, 16). For example, the resistance exercise, holding a dumbbell, was combined with the lunge position(15, 16). Hip and knee muscle activities were increased in the lunge position with resistance exercise more than in the lunge position alone(15, 16). Thus, the lunge position has been recommended to be combined with other exercises to provide additional benefits.
To our knowledge, EMG-based biofeedback has the potential to be used in monitoring muscle activity(9). Hence, our study was to use EMG-based RVBF to monitor muscle activity of TrA/IO and guide participants while performing the ADIM. Furthermore, the ADIM with RVBF has not been investigated in the upright position, standing position, functional position, or lunge position, which are common starting positions for exercise. Therefore, the purpose of this study was to investigate the effect of ADIM with RVBF on back and hip muscle activities in the standing and lunge positions. We hypothesized that the ADIM would improve the muscle activity of the back and hip during holding in the positions. Our findings might provide beneficial information about the use of ADIM with RVBF for improving back and hip muscle activation during exercise.