The most common error made in roll-up or trunk-curl general instruction is not matching the client’s strength level with the appropriate level of demand. This should be a reminder that disciplines such as yoga and Pilates require personalized instruction and attention to detail. This type of abdominal strengthening is most successful in small groups or one-on-one. When performing a trunk curl/sit-up (legs bent or extended) with a client, check the following criteria:
1. Know the Client’s Passive Spinal Flexibility. Some clients have limited lumbar mobility (stiff spines) and this will limit their ability to perform the trunk curl to a point that the sit-up portion is safe. To measure this, passively raise the client into a trunk curl and assess trunk flexion.
2. Look for Tight Hip Flexors. If a client has hip flexor tightness he will be unable to hold the pelvis in a posterior tilt to safely perform the sit-up phase. The client should be able to flatten the lumbar spine onto the floor in supine position with the legs extended. If he is unable to perform this maneuver, place a roll under his knees to reduce hip-flexor pull.
3. Watch for a Posterior Pelvic Tilt. When the client initiates the trunk-curl, the pelvis should tilt posteriorly. If the client is using her hip flexors for the motion the pelvis will tilt anteriorly.
4. Observe the Neck Position. The chin should be brought to the Adam’s apple, not to the chest. The neck should not extend either, which is the movement that occurs when the client’s face is to the ceiling.
5. Does the Client Have a Thoracic Kyphosis? This exercise will contribute to the problem.
6. Can the Client Curl to the Limit of his Spinal Flexibility? This should be attainable with the shortest lever of the exercise (arms reaching in front). If the degree of difficulty is increased with lever (arms on chest or behind head), does the client still perform the same amount of lumbar flexion (trunk-curl)? If the trunk-curl diminishes, the client is not ready to progress to the more challenging exercise.
7. Does the Client Maintain the Lumbar Curl at the Initiation of the Sit-up Phase? If not, the abdominals are too weak and there is anterior shear stress on the lumbar spine.
8. During the Trunk-curl Phase the Heels Should Stay in Contact with the Floor. If the feet come up, it is safe to hold them down if attention is focused on whether the trunk maintains the curl. For best results hold the feet only during the sit-up phase. If the feet are held down before the sit-up phase, it will cause the hip flexors to contract, initiating the trunk to rise. It is especially dangerous to hold the feet while your client is performing a high number of repetitions. The onset of abdominal fatigue in this instance would allow the less fatigable hip flexors to dominate the movement.