PT on the Net Research

Torso Twist Machine


Question:

There is a dinosaur torso twist machine at my gym that is chronically broken down. I have never liked to train clients on this machine, or variations of it, at other clubs in the past. I would like to get rid of the piece, which may result in a witch hunt (the piece is VERY popular). What do the experts have to say on this exercise? Is there any real benefit that would ever outweigh the risks? What are the body weight, free weight and free motion alternatives?

Answer:

First of all, and this probably goes without saying, any piece of equipment (i.e., free weights, dumbbells, tubing, balance devices) can be harmful if used improperly. Often times, a particular piece or brand gets a bad review in one of the various fitness magazines out there, for various reasons, and the next thing you know, you're told it's bad for you or you'll get hurt if you use it. The question we should be asking is, "What's the goal?" Many statements made by professionals today get put through the telephone game and then get blown completely out of context. To prevent this, we as fitness professionals must work hard to become "masters" of the sciences of our craft (i.e., biomechanics, functional anatomy, etc.), so we are able to make our own decisions based upon the science.

That being said, I'm going to identify some of the positives, negatives and alternatives to using this type of machine.

When training in an isolated, uniplanar, artificially stabilized environment the kinetic chain in not being prepared to deal with imposed demands of normal daily activities (walking up/down stairs, getting groceries out of the trunk, etc.). Training integrated, functional movement patterns targets synergistic muscles to produce force, reduce force and dynamically stabilize in all three planes of motion. This creates maximal motor unit recruitment, which facilitates a greater overall training response.

What this means in this situation is that in real life, the trunk does not rotate in isolation and certainly not in separation from the lower/upper extremities (depending on which model of torso rotation you use). Therefore, the strength you've created on this machine will administer virtually no functional carry over to your real world/performance environment. (Although, you will most certainly become stronger at machine torso rotation!).

Spinal rotation is quite often times restricted with the average club member. The lower extremity-mobile version of these machines may take the average unaware user into extreme eccentric passive ROMs. This repetitive stress to the facet joints of the spine will certainly not aid the client/member in gaining strength.

Maintaining neutral spine while loading rotating is critical. A deviation out of neutral (particularly into lumbar flexion), due to poor core strength in combination with repetitive loading over time could prove disastrous.

The posterior lateral aspect of the disk is described as structurally the weakest. For this reason the most vulnerable position for the disks can often be that of flexion combined with rotation. Flexion of the spine in standing has been said to decrease disk integrity by 50 percent. Adding rotation to flexion decreases disk integrity by another 25 percent. This is a total of 75 percent reduction of disk integrity during combined flexion and rotation. A seated position places 30 to 40 percent more pressure on the intervertebral disk than a comparable standing position.

This is not suggesting that we never train in flexion/rotation OR seated for that matter. (If this was the case, how would anyone ever function, let alone "work out?") It does suggest that we treat these situations/positions as load specific and that we as professionals know our clients capabilities through proper assessment.

ALTERNATIVES

To effectively train the core in the transverse plane, one may need to begin with more static transverse plane stability and be progressed to more transitional dynamic rotational exercises. Here are a few examples of progressions:

Remember, keep everything in context! 

REFERENCES:

  1. Purvis, Tom (2000). Resistance Training Specialist Manual