Hip pain following an abdominal workout is a common occurrence that often confuses people targeting their core muscles. This discomfort is typically not a sign of a successful ab session. Instead, it indicates that the body is using muscles other than the abdominal wall to perform the movement. Understanding the underlying anatomy and mechanics reveals why exercises intended for the midsection often lead to strain in the hips. This article explores the root causes of this pain and offers practical adjustments for a more effective and comfortable workout.
The Core Culprit: Overworked Hip Flexors
The primary reason for hip pain after core work lies with a powerful muscle group known as the hip flexors, which are composed mainly of the iliopsoas. This group includes the psoas major and the iliacus, which work together to connect the lower body to the upper body. The psoas major is especially significant because it originates from the lower spine (lumbar vertebrae) and runs down to attach to the femur (thigh bone).
The main function of the iliopsoas is hip flexion, which involves lifting the leg toward the torso or pulling the torso toward the leg, as seen in movements like marching or climbing stairs. When performing common abdominal exercises such as sit-ups, leg raises, or V-ups, the movement of lifting the legs or the torso heavily recruits these hip flexors. In fact, exercises like straight leg raises are known to be superior for activating the hip flexors compared to the abdominal muscles.
If the abdominal muscles, like the rectus abdominis or the deep core stabilizers, are not strong enough to handle the workload, the body naturally shifts the burden to the stronger hip flexors. This is especially true during high-repetition or prolonged core work. The resulting strain, soreness, or tightness felt in the front of the hip is a direct consequence of the hip flexors taking over the movement meant for the core. This overuse can lead to muscle fatigue and contribute to an anterior pelvic tilt, which further exacerbates tightness and discomfort.
Understanding Compensation and Improper Form
The mechanism that forces the hip flexors to take over is known as muscular compensation, which occurs when a secondary, stronger muscle group performs the work intended for a weaker, primary group. When the deep core muscles fatigue, the hip flexors step in to complete the exercise, limiting true core engagement. This is a common issue in exercises where the feet are fixed or the legs are moved, such as traditional sit-ups and leg lowers.
One of the most frequent forms of compensation is the arching of the lower back, or excessive lumbar extension, particularly during leg lowering exercises. When the abdominal muscles fail to stabilize the pelvis, the psoas major, due to its attachment on the lumbar spine, pulls on the lower back, causing it to lift off the floor. This arching movement places unhealthy stress on the lumbar spine and shifts the work entirely away from the abdominals.
Another mechanical error involves using momentum to power through repetitions, rather than controlled muscle contraction. For example, pulling on the neck during sit-ups or quickly swinging the legs during leg raises reduces the time the abdominal muscles are under tension. These actions allow the powerful hip flexors to dominate the movement, which increases their strain and drastically reduces the effectiveness of the exercise for the core. Proper technique requires a slow, controlled pace that forces the target abdominal muscles to initiate and manage the entire range of motion.
Relief Strategies and Exercise Adjustments
Immediate Relief
Immediate relief for hip flexor soreness involves gentle stretching and rest to calm the overworked muscles. A half-kneeling hip flexor stretch is highly effective: kneel on one knee and gently shift the hips forward while tucking the pelvis to lengthen the strained muscle in the front of the hip. Holding this stretch helps restore mobility and reduce acute tightness. Applying heat to the area can also help increase blood flow and relax the tight muscle tissue.
Long-Term Prevention
For long-term prevention, modifying exercise form is the most effective adjustment. Before beginning any floor-based core exercise, focus on maintaining a posterior pelvic tilt by pressing the lower back firmly into the floor. This small adjustment helps to stabilize the pelvis and encourages the abdominal muscles to engage first, which limits the hip flexors’ ability to take over.
Substituting high hip-flexor exercises with alternatives that focus on core stabilization can also prevent future pain. Exercises like planks, side planks, and dead bugs challenge the core’s ability to resist movement without the heavy involvement of the iliopsoas. For those who prefer lying movements, traditional crunches can be performed with the feet off the floor in a tabletop position to help deactivate the hip flexors.
Balancing Muscle Strength
Finally, a balanced approach to strength training should include strengthening the opposing muscles, namely the glutes and hamstrings. Exercises like glute bridges and clamshells help to stabilize the hips and pelvis. Focusing on this balance helps ensure that the core, not the hips, performs the work during abdominal training by counteracting the strength imbalance that often causes hip flexor overuse.