Medicine Ball Leg Crunch
The Medicine Ball Leg Crunch is a dynamic core exercise that targets the lower abdominals by adding resistance to a traditional knee tuck or reverse crunch. By squeezing a medicine ball between your ankles or knees, you engage the adductors and deep core muscles for a more intense abdominal workout.
Since this movement relies heavily on hip flexor strength and lower back stability, your AI coach analyzes your recent training load from activities like running or squatting to ensure you aren't overworking these areas. By integrating your daily HRV and sleep data via HealthKit, the app optimizes your rep targets and weight selection based on your current recovery status. Additionally, if you consistently report lower back sensitivity, the AI learns to automatically substitute this with spine-neutral alternatives.
Form Cues
- Squeeze the medicine ball firmly between your shins or ankles
- Press your lower back aggressively into the floor
- Exhale sharply as you bring your knees and chest together
- Control the lowering phase with a slow tempo
- Keep your chin tucked slightly to protect your neck
- Don't allow your lower back to arch off the floor
- Don't pull on your head or neck with your hands
- Don't use momentum or swing your legs to initiate the movement
- Don't let the medicine ball slip or wobble
- Don't hold your breath during the exertion
Common Mistakes
- Arching the lumbar spine
- Yanking the neck forward
- Using momentum instead of muscle
- Relaxing the adductor squeeze
- Lowering the legs too quickly
Muscles Worked
This exercise primarily targets the lower region of the rectus abdominis by utilizing the weight of your legs and the medicine ball as resistance against gravity. It secondarily works the hip flexors and upper abs, while the inner thigh muscles (adductors) are recruited isometrically to keep the medicine ball secure.
Primary
Secondary
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