Proprioception and Balance Training?

[Guest guest]

The modern conditioning and therapeutic market abounds with a host of ideas,

programs and devices intended to enhance proprioception in athletes and

recovering patients. The 'victims' (I mean " clients " !) of these methods are

required to stand, sit, lie and execute many different drills on wobble

boards, physio balls, sponge rollers and a multitude of miscellaneous weird

and wonderful objects. Does all of this help or if it does help, has it more

to do with something other than the balancing drills? The following

scientific article (extracts provided) addresses this issue at length.

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Proprioceptive Measures warrant Scrutiny

Conventional assessment measures may not reflect correct neurological

pathways.

By Danny M. Pincivero, PhD, and Alan J. Coelho, EdD

<http://www.biomech.com/db_area/archives/2001/0103function.bio.html>

Performance of athletic skills and physical fitness activities requires

normal and adequate function of the knee joint. Such function depends on many

factors including neuromuscular integrity, muscle strength, and flexibility.

Also critical to normal knee function are the sensory signals emanating from

the limb itself. Functioning through various reflex pathways, these sensory

signals provide us with a conscious awareness of the internal and external

environments about the lower limb, which in turn provides an indication of

limb position and movement.

This physiological entity was originally described in 1908 by Sir

Sherrington as " proprioception, " and has since been the focus of numerous

investigations.1 Proprioception, which has been classified as a sensory

submodality of touch,2 is hypothesized to be related to knee injury

predisposition, particularly in female athletes, and successful exercise

rehabilitation. Unfortunately, very little scientific evidence has supported

such claims. Furthermore, because the knee joint is a common site of injury

resulting in disability, the need for evidence-based conclusions concerning

the functional role of proprioception in injury occurrence and management is

paramount.

What is Proprioception?

Proprioception is defined as the conscious awareness of limb movement and

position. The term proprioception has also been linked to a number of

subconscious neurological and neuromuscular mechanisms that are vital to

human function and locomotion. Various physiological signals that are

initiated in peripheral muscles give rise to spinal pattern generators

producing smooth rhythmical movements, as well as contributing to the

maintenance of muscle tone. These resulting actions of the central nervous

system (CNS) are largely mediated by spinal level reflexes (stretch reflex,

cross-extensor reflex) and cerebellar preprogrammed impulses for corrective

locomotor maneuvers and the maintenance of posture. As many studies have

operationalized " proprioception " into a consciously mediated mechanism, a

well-known and distinct neurophysiological pathway has been described to

explain such events........

This pathway of conscious knee joint position and movement awareness is

primarily involved in most tests of proprioception in many studies, but its

functional implication

remains clouded and speculative in these investigations.........

A number of key questions surrounding these methods continue to persist,

without clarification at present. Hogervorst and Brand, in a wide-ranging

review, postulated that position and movement awareness tests do not

differentiate between mechanoreceptors arising from the anterior cruciate

ligament and those of any other structure around the knee. The functional

utility of joint replication tests or movement threshold tests at very slow

velocities also remains in doubt. Although some studies suggest low to

moderate correlations between these methods and various clinical and

functional tests, the consensus in the literature is that there are no

functional causal relationships. Another issue relates to the test-retest

reliability of these methods. An adequate approach necessitates

well-controlled reevaluation procedures and full presentation of reliability

estimates (i.e., intra-class correlation coefficients, standard errors of

measurement, coefficients of variation, and 95% confidence intervals).

Unfortunately, most studies that suggest " good " reliability of incorporated

methodology present very little data to support it. The nature of the

proprioception testing procedures also renders evaluation of their validity

difficult.

If one accepts the general premise that performing such tests at very slow

velocities selectively activates articular mechanoreceptors, then it should

be assumed that our conscious perception of limb movement arises from such an

origin. In fact, it is well known that numerous different afferent receptors

give rise to proprioception and that the relative weighting or distribution

of this input will likely be task specific. As these assumptions start to

come up against issues of functionality or applicability, we are prompted to

revisit the intent of the testing mechanisms, as well as the

neurophysiological pathways under question ...........

Although it is tempting to suggest that surgical intervention has a positive

restorative effect on proprioception, such a suggestion is highly speculative

as preoperative proprioceptive " deficits, " measured through joint motion and

replication tests, are clearly inconclusive.

Furthermore, the notion that the ability to consciously appreciate joint motion

and position is mediated by

the ACL is unsubstantiated. Hogervorst and Brand specifically stated that

" Studies of proprioception after a rupture or reconstruction of the ligament

should be interpreted in the broader context of whether mechanoreceptors of

the joint or muscles play the primary role in proprioception. " Based on the

known neurophysiological pathways involved in joint position and motion

awareness, assessment techniques should be further refined to better reflect

such pathways.

Exercise Training/Rehabilitation

After knee joint injury and/or surgery, restoring function clearly depends on

tissue healing and the enhancement of muscle strength, endurance, and

flexibility. From a practical perspective, exercises aimed at improving

proprioception in addition to activities that are mediated largely by

proprioception, such as balance and posture, have been well incorporated into

clinical practice...... A rehabilitation program augmented with

perturbation training appeared to reduce the number of episodes of the

affected knee giving way during activity.

This pattern, however, doesn't seem to hold true for joint-angle replication

tests of proprioception. Following a four-week period of rehabilitation in 50

ACL-deficient patients, et al showed no improvements in joint position

sense, despite significant improvements in functional testing and isokinetic

quadriceps strength. In light of the results from these few studies, it

quickly becomes apparent that measures of muscle strength and functional

activities can effectively be improved with the inclusion of exercises aimed

at enhancing neuromuscular control.........

Gender Differences and Functional Relationships

The issue of a proprioceptive gender difference has largely been driven by

relatively larger rates of knee injuries in female athletes than in their

male counterparts. Although experts have hypothesized that proprioceptive

acuity is a potential predisposing factor for this injury rate pattern,

conclusive evidence has not justified this claim. Furthermore, little resea

rch has addressed gender-specific patterns of sensation, afferent neural

transmission, or perception. The force-generating capacity of large muscle

groups such as the quadriceps femoris muscle has been shown to be

significantly higher in males than females when normalized for body mass.

Furthermore, males have also demonstrated a significantly greater rate of

fatigue than females, which may largely be due to males' greater proportion

of type II muscle fibers.

Unfortunately, these experimental findings have been unable to lend insight

into a gender-dependent pattern of joint movement sense. Specific to this

issue, Birmingham et al recently showed that the ability to actively and

passively replicate previously positioned knee joint angles in weight-bearing

and nonweight-bearing conditions did not differ between males and females.

They observed that the range of values representing error in joint

replication (in degrees), ranged across the various conditions from 2.45° to

3.08° in females (n = 39) and 2.35° to 3.19° in males (n = 20).

In a study examining proprioception differences between male (n = 17) and

female (n = 17) athletes, movement detection of the dominant knee was

evaluated at a starting angle of 15° of flexion, while moving into either

flexion or extension at a constant rate of 0.5° /sec.38 Interestingly,

significant gender differences were detected while moving into extension, but

not into flexion. However, the calculated mean difference between males and

females for the statistically significant effect (movement into extension)

was 0.84° , while the nonsignificant difference (moving into flexion) was

0.92° ; a higher mean value. This outcome not only underscores the importance

of interpreting " statistically significant " effects, but questions the

" functional significance " of such testing procedures.

Beynnon et al demonstrated no significant relationships between the ability

to detect passive knee movement at 0.1° /sec, and clinical tests of knee

stability in 20 ACL-deficient patients. Such findings have also been

documented by et al who demonstrated no significant correlation

between joint position sense and functional activity tasks (i.e., hopping and

figure-8 runs), functional activity as measured by a questionnaire, and

measures of isokinetic strength in 50 unilateral ACL-deficient patients. In

a study of 26 ACL-deficient and -reconstructed patients, Mac et al

observed no significant relationships between the threshold to perception of

passive motion at 0.5° /sec, time from injury to followup or surgery, KT-1000

arthrometer results, and patient satisfaction.

These results are, however, contrary to those of Barrack et al, who showed a

moderate correlation (r = 0.465) between knee laxity and the threshold to

knee motion in 11 ACL-deficient patients. Borsa et al demonstrated

significant correlation between passive knee movement into extension at 0.5°

/sec, and the single-leg hop test (r = -0.46 to r = -0.56). Although this

result may statistically suggest that individuals with the ability to

perceive knee movement sooner would hop a farther distance, there is little

basic scientific evidence linking the static assessment of proprioception

with a ballistic activity such as hopping.

Furthermore, there does not appear to be a sound physiological rationale to

justify using these extremely slow rates of knee displacement (0.1° to 0.5°

/sec), as the detection of movement at these rates may not truly assess

proprioception as it relates to its functional role. It is compelling to

suggest that joint replication tests may provide a better evaluation of

proprioception. In proposing this, however, researchers must reexamine the

relationship between the neural pathways of interest and those that actually

mediate proprioception.

Conclusions and Future Directions

Proprioception is a complex neurophysiological mechanism driven by input from

specialized receptors in the limbs that provide humans with a perception of

joint position and movement. There has been much speculation on the influence

of factors such as muscle fatigue, joint injury and surgery, and gender on

proprioception. But the scientific literature has yet to arrive at a

consensus regarding some of these factors.

Although many studies have been published to date, many more questions have

been raised than answered as a result of these investigations: What is the

precise role of proprioception, defined as conscious joint awareness, during

activities of daily living or athletic endeavor? Must improvements in

proprioception occur for postinjury or postsurgery rehabilitation to be

successful? Perhaps the most compelling question is, do presently used

methods to assess proprioception accurately depict the neurological pathways

that are known to be vital for coordinated inter-limb dynamics and

neuromuscular control? These questions and others are sure to stimulate new

avenues for proprioception research in the future.

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Dr Mel C Siff

Denver, USA

Supertraining/