The “In and Outs” exercise is a dynamic, bodyweight movement designed to build strength and endurance in the abdominal muscles. This movement requires coordinated effort from the core and hip flexors to execute a controlled, repetitive motion. This article details the mechanics, proper execution, engaged muscle groups, and strategies for modifying the intensity.
Core Mechanics of In and Outs
The name “In and Outs” describes the fundamental mechanism of the exercise: alternating between a compact, flexed position and an elongated, extended position. The movement is performed while balancing on the glutes, requiring continuous abdominal engagement to maintain stability. This need for balance elevates the challenge beyond traditional floor exercises.
The “In” phase involves powerful hip flexion, pulling the knees toward the chest while the torso performs a slight crunch forward. The “Out” phase requires extending the legs straight out while leaning the torso back, creating a long lever. This alternating action imposes a significant, fluctuating load on the abdominal muscles, particularly the lower rectus abdominis. Using the legs as a long lever increases the demand for spinal stabilization throughout the entire range of motion.
Step-by-Step Execution Guide
Begin by sitting on the floor with your knees bent and your torso slightly reclined, balancing on the sit bones. For initial support, you may place your hands on the floor behind your hips. For a greater challenge, lift your hands and extend them forward. Lift your feet off the floor, drawing your knees toward your chest to establish the compact starting position.
To move to the “Out” position, simultaneously extend both legs straight outward while leaning your torso further back. Create a long, straight line from your shoulders to your heels without allowing your lower back to round or your feet to touch the ground. Inhale as you transition into this extended position to prepare for the subsequent contraction.
The return to the starting position constitutes the “In” phase, which is the most intense part of the movement. Exhale forcefully as you simultaneously pull your knees back toward your chest and bring your torso upright. A common error is allowing the lower back to excessively round or using momentum to swing the legs, so maintain a controlled, steady tempo throughout the entire repetition. Focus on initiating the movement from your core.
Primary and Secondary Muscles Activated
The “In and Outs” exercise primarily targets the Rectus Abdominis, the muscle responsible for spinal flexion. This muscle works intensely to pull the torso forward during the “In” phase and prevent hyperextension when the body leans back during the “Out” phase. The Iliopsoas, a powerful group of hip flexors, also acts as a primary mover, responsible for lifting and drawing the legs toward the torso.
The exercise recruits several secondary muscle groups that function mainly as stabilizers. The Transversus Abdominis, the deepest layer of the core, contracts to increase intra-abdominal pressure and stabilize the spine during dynamic leg movements. The Obliques (internal and external) are engaged to prevent rotation and maintain the lateral stability of the torso. The Rectus Femoris, part of the quadriceps group, also assists in leg extension and control.
Scaling the Movement
The intensity of the “In and Outs” can be easily modified to suit different fitness levels. For individuals new to the exercise, greater stability is achieved by keeping the hands placed firmly on the floor behind the body for support. Another modification is to reduce the range of motion by not fully straightening the legs during the “Out” phase, which shortens the lever and decreases the load on the core.
More advanced users can increase the demand by completely removing hand support, extending the arms overhead or across the chest. To further intensify the exercise, incorporate external resistance by holding a dumbbell between the feet or wearing ankle weights. Progression often involves transitioning to a full V-up, where the body is fully extended and then simultaneously crunched into a tight V-shape, which is a more challenging variation.