Thomas C. Purvis, PT, CPT, CSCS

Introduction

As a physical therapist I have been intrigued by the vast array of abdominal training devices that have become so popular in the last year.  Having been bombarded with questions from my patients regarding the effectiveness of these products, I decided to conduct an informal biomechanical analysis. I then utilized, during various phases of rehab, the unit which I found to be biomechanically most beneficial.

I chose the Ab Trainer™CLUB PRO (manufactured by Precise Exercise Equipment, Inc.) for a trial use in my clinic.  The Club Pro appears to have been intentionally over-engineered.  The extra thick steel tubing and high tech molded foam cushions seem perfect for taking the beating associated with high traffic settings like fitness centers and busier rehab clinics.  This particular model is available in tow sizes; standard and small (for people 5’3” and smaller).

Biomechanical Analysis

The purpose of the Ab Trainer is to provide cervical support during the performance of the trunk curl exercise.  But correctly producing that support is the challenge.  If the head does not move in exact unison with spinal motion, we can do more harm than good.  This, of course, is the difficulty associated with simply cradling the head with the hands, or with a towel supported by the hands, during a trunk curl.

In my opinion, the Ab Trainer’s curved steel frame does an excellent job of accurately simulating spinal motion during the trunk curl.  Functionally, as the various points of is curved frame contact the floor, the subtlety or severity of the curve effectively alters the degree of spinal flexion.  The cervical support provided by the Ab Trainer is also excellent.  This is accomplished with a contoured, padded headrest (much like a standard cervical pillow) attached to the unit via a “swinging” crossarm.  This design allows the headrest to move in concert with the frame throughout the exercise so proper alignment is maintained.

Clinincal Observations

After receiving my Ab Trainers, one of each size, I then questioned its role in a spinal strengthening / stabilization program as well as how biomechanically viable the trunk curl is in general.  Many therapists argue over the value of various treatment methods (Mackenzie Extension vs. Williams Flexion).  It is probably most helpful to realize that no single method or exercise is appropriate in every case.  Each becomes a valuable tool, however, when we endeavor to understand where and when they are most appropriately utilized. The trunk curl can be a valuable part of a total trunk strengthening program for a majority of the population.  In rehab, its use will depend upon the diagnosis and the point within the progression at which it is introduced.

Unless contraindicated, I found the trunk curl was best introduced after successful progression through some degree of isometric and dynamic stabilization training.  In other words, the patient should be able to control the stabilizing musculature well enough to maintain neutral alignment in the seated and standing positions.  The trunk curl should be introduced as a neuromuscular control” exercise rather than an all out attempt to “crunch.”  It is important that the patient eliminate the “more-is-better” sit-up exercise from his or her mind and replace it with concept of degrees leading up to movement.

By taking the time to teach and encourage progressive contractile control over the abdominals prior to the actual production of movement, spinal motion can be introduced with greater awareness and greater control.  If the amount of spinal flexion needs to be restricted, either by prescription or due to discomfort, the patient will be able to better utilize and benefit from even the smallest degree of available motion by making that limited movement relatively intense.  In my experience, the Ab Trainer provided numerous advantages over the traditional trunk curl.

1. The learning curve was virtually eliminated.

1. The limitations brought about by cervical fatigue were eliminated.  This allowed the patient to continue progressing in abdominal strength, while we worked on cervical strength separately, rather than being forced to wait for adequate cervical strength before further abdominal exercise.  In the this way, the Ab Trainer is like “training wheels.”

1. The need to use the hands, a towel, etc. to support the head was eliminated. Using these things commonly leads to “pulling” on the neck rather than support.

1. Performing the correct motion improved the intensity in the appropriate musculature even in patients that I had considered already well-versed in trunk curls.

1. The ability to safely and easily add resistance was key to actually improving strength, not just endurance.

1. Cervical patients could do trunk curls for the first time.

1. The ability to more accurately reproduce a prescribed range of motion was enhanced.  The vertical hand placement lends itself as a visual “gauge” of motion for those patients requiring a shortened range to decrease the disproportionate compressive forces associated with a full trunk curl.  This also provided awareness of smaller increments of motion allowing more accurate manipulation of ROM as a factor for progression.

1. For those who used the Ab Trainer at home, patient compliance improved.  To me, this was ultimately the most important factor.  Ab Trainer makes home abdominal exercise more user-friendly and the variations, as well as incremental weights, make progression at home easier to implement

Conclusion

In conclusion, whenever trunk curls are deemed appropriate, Ab Trainer is the most biomechanically sound tool of its kind.  Ab Trainer acts as both “training wheels” and muscle “intensifier,” making progression easier.  And if patient compliance improves post rehab, ultimately, the prognosis will be improved, as well.

Thomas C. Purvis, PT, CPT, CSCS is owner of Focus On Fitness Rehiblitation and Conditioning in Oklahoma City, Oklahoma.  He lectures nationally and internationally on the biomechanics of resistance training and is the head for the National Academy of Sports Medicine.