Neoprene wraps (Birmingham et al, 1998)

In this installment of “Neoprene wraps”, I’ll be looking at the study done by Birmingham et al. in 1998–of the earlier studies done on neoprene wraps and proprioception. Unfortunately, I haven’t got electronic access to an even earlier one in 1995–but maybe I’ll trek over to the bricks-and-mortar library to pick it up some time.

Effect of a neoprene sleeve on knee joint position sense during sitting open kinetic chain and supine closed kinetic chain tests
Birmingham, TB, Framer, JF, Inglis, JT, Mooney, CA, Murray, LJ, Fowler, PJ, Kirkley, S
American Journal of Sports Medicine, 26(4): 562-566, 1998.

The purpose of this study was to look at the effects on proprioception (i.e. position sense) of a neoprene knee sleeve during open kinetic chain (i.e. where the foot is free to move) and during closed kinetic chain (i.e. where the foot is fixed and knee moves in space) tests.

The reasoning behind this study was to follow up on studies that had both shown improvements in proprioception during open-chain tests and other studies that had shown different joint forces between open and closed chain tests, but had not investigated proprioception. The theory put forward by these authors was that:

“Proprioceptive sensations arise through simultaneous activity in various types of sensory receptors located in the akin, muscle and joint tissues. The relative contribution of each of these sensory channels depends on the load imposed on the different tissues. Accordingly, it has been suggested that during conditions of closed kinetic chain exercise, further proprioceptive input, not available during open kinetic chain tests, may make the additional input when elastic knee supports are worn less important.”

Basically these authors are suggesting that previous research has suggested that there are sensory inputs during closed chain exercises that are not available during open chain exercises (for instance, the contribution of ankle proprioception as a component of detection of knee position); and that given these extra sensory inputs, that a knee sleeve may not make proprioception any better.

So, why is this paper relevant to weight lifters?

Short of the leg extension and leg curl (and their variants, like GH raises on glute-ham raise machines), most individuals training with weights rely primarily on squats, deadlifts, leg press, lunges and closed chain kinetic lifts. If there is no additional proprioceptive benefit conferred to the lifter by knee sleeves, then one has to debate the utility of using them.

Methods

The researchers recruited 36 subjects to do one open kinetic chain and one closed kinetic chain test within one week. Eighteen of these were men, eighteen were women. They were tested for both tests with and without the neoprene sleeve. The order of these tests was random.

Subjects were asked to extend the knee (quadriceps use primarily) from 90 degrees to one of five randomly selected angle targets (somewhere between 65 and 35 degrees, which is the midrange of knee range of motion). The were held at that angle for 3 seconds while they were told to remember the position so that they could replicate it.

To make sure subjects didn’t use timing (like counting how many seconds it took to get to a position) or displacement cues (like how the pad felt against their leg), the knee was returned to a different random starting place–between 10 and 15 degrees from the original starting place. After 5 seconds rest, the subjects were asked to put their knee into the place it was before.

Subjects got to practice a bit before the formal testing started–two practice runs so they would know what was expected of them.

Every subject did 5 trials with 30 seconds between efforts. All subjects were blindfolded.

Calculations

The absolute difference between the target and reproduced angles was averaged over the 5 attempts for both sleeve and non-sleeve attempts (so, if you were -5, 5, -5, 5, and 5 degrees off the target, your average difference would have been 5).

The “sleeve effect” was also calculated by subtracting the absolute average difference (AAD) of the sleeve test from the non-sleeve test.

The primary comparison was done between the “sleeve effect” of the open chain tests and the “sleeve effect” of the closed chain test. They also looked at whether there were differences between open and closed chain effects with respect to the AAD, with and without sleeves; as well as the relationship between subjects’ no-sleeve AAD score and sleeved AAD score; and also whether the number of days per week subjects participated in physical activity helped to predict their AAD scores for both open and closed chain test with no sleeve.

Results

For the primary test, “Is there a difference between open and closed kinetic chain tests when it comes to ‘sleeve effect’?” It was found that the “sleeve effect” was significantly less in the closed chain kinetic test than in the open chain test. This difference persisted even after adjusting for gender (i.e. whether you were male or female did not alter this result).

It seems that there was a positive relationship between the “sleeve effect” and subjects’ non-sleeved AAD. That is, if you did well without the sleeve, your “sleeve effect” was less. There was, however, no relationship between the number of days subjects’ days of activity and “sleeve effect”. That is, just because you were more active, the “sleeve effect” was the same as those who weren’t as active as you.

Perhaps the most interesting result to note in this study is that 72% of subjects felt that the sleeve improved their performance in being able to replicate joint angles, but that performance on the replication tests did not correlate with how subjects felt about whether the sleeve made them better or not.

My concerns (for the geeks)

My biggest concerns with this study have to do with the statistics. Looking at their results, there are often cases where the reported means and standard deviations reflect a sample distribution that was probably not normally distributed. This makes the validity of statistical testing difficult because the authors used statistical tests that make the assumption that the distribution is, indeed, normal. The only saving grace of this mistake is that the tests they chose to use are also quite robust against violations of the normal distribution assumption–i.e. if the data are not normally distributed, you still end up with the same result you would if you had used the appropriate test. So, while I’m not happy that they’re messing around with statistics they don’t fully understand, I don’t get the impression (both because t-tests are robust against violations of the assumption of normality; and also from looking at the actual data tables) that their final conclusion is all that off.

The bottom line

This study shows that wearing a sleeve during open kinetic chain movements probably does improve proprioception quite a bit; but that during closed chain movements, the improvement in proprioception is negligible (the sleeve effect on average was 0.3–that is the sleeve improved people’s position sense by 0.3 degrees). It also showed that there is likely an inherent proprioceptive ability that isn’t affected by general training (physical activity)–though it’s not possible to really comment about specific proprioception training).