If Proprioception Is Relevant to Locomotion, then Why Test It

Standing Still?

Mervyn Travers

, James Debenham

, William Gibson

, Amity Campbell

and Garry Allison

School of Physiotherapy and Exercise Science, Curtin University, GPO box 1987, WA 6845, Bentley Australia

University of Notre Dame, School of Physiotherapy, 19 Mouat Street, Fremantle, WA 6959, Australia

Keywords: Proprioception, Stretch-shortening Cycle, Minimal Perceptible Difference.

Abstract: Traditionally, proprioception research has utilised passive position or movement detection and repositioning

tasks. Current evidence suggests proprioception represents a complex synergy of sensory inputs that may be

more appropriately assessed during more functional tasks. This study investigated the Minimal Perceptible

Difference (MPD) test - a novel assessment of participants’ ability to perceive floor height changes whilst

hopping. Sixteen healthy volunteers performed multiple hopping trials on a custom-built sleigh apparatus

that permitted a floor height change (range 3mm to 48mm). The MPD in floor height was recorded for 8

different hopping conditions (Factors - Technique: alternate / bilateral hopping; Side: dominant / non

dominant; Direction of change: up / down) over two separate testing occasions. Within and between-day

reliability were assessed using ICC and 95% confidence intervals. Hopping technique was the only factor

which significantly influenced participants’sensitivity to detect changes in floor height. The mean MPD was

significantly lower (p<.0001) for bilateral hopping (15.65mm) when compared to alternate hopping

(26.59mm). Bilateral hopping yielded strong ICC for within and between day reliability. We propose the

bilateral hopping MPD assessment is a reliable, functional assessment of proprioception sensitivity that may

better reflect human gait than established static assessments.

1 INTRODUCTION

Proprioception is defined as “afferent information

from proprioceptors located in the proprioceptive

fields that contribute to conscious sensations

(muscle sense), total posture (postural equilibrium)

and segmental posture (joint stability)” (Sherrington,

1906). It is a concept with particular relevance to

clinicians and researchers with respect to

performance, injury and rehabilitation (Brumagne et

al., 2004); (Cameron et al., 2008); (Fu and Hui-

Chan, 2007); (Herrington et al., 2008); (Lephart and

Jari, 2002); (Vuillerme and Boisgontier, 2008). Most

methodologies examine proprioceptive acuity using

passive position detection (Down et al., 2007),

passive movement detection (Salles et al., 2011) and

active repositioning tasks (Ribeiro et al., 2007).

However, recent evidence suggests proprioception is

a much more complex concept than just joint

position sense and kinaesthesia, incorporating the

integration of the body schema (Ivanenko et al.,

2011) and its continous refinement being expanded

to a concept called “somatopercepetion” (Longo et

al., 2010). Of particular note is that current testing

methods may represent convenient research

methods, but may not reflect the dynamic function

of the lower limb – to perform repeated Stretch

Shortening Cycles (SSC) (Proske et al., 2000).

The authors utilised a sub-maximal sleigh

hopping model to replicate the normal function of

the limbs via repeated SSC. This model has been

applied to develop the Minimal Perceptible

Difference (MPD) test – a novel research tool which

examines individuals’ ability to detect changes in

floor surface height during the repeated SSC. This

study aimed to investigate the reliability of the MPD

test on a within and between day basis. We also

aimed to quantify the MPD in floor surface height

for a healhy population.

2 METHODS

The MPD test examined the sensitivity of healthy

participants to perceive changes in floor surface

height whilst hopping on a custom built apparatus

Travers M., Debenham J., Gibson W., Campbell A. and Allison G..

If Proprioception Is Relevant to Locomotion, then Why Test It Standing Still?.

 2013 SCITEPRESS (Science and Technology Publications, Lda.)

(Figure 1) with an adjustable floor (Figure 2).

Figure 1: The custom built sleigh apparatus.

Figure 2: The Sliding Floor Mechanism illustrating a

36mm reduction in floor height under the right foot.

Sixteen healthy participants performed multiple

trials of 5 consecutive hops on a custom built sleigh

apparatus that permitted the testers to change the

floor height (range 3mm to 48mm) during each trial,

as dictated by a structured searching algorithm.

MPD in floor height was recorded for 8 different

hopping conditions (Factors - Technique: alternate /

bilateral hopping; Side: dominant / non dominant;

Direction of change: up / down) over two testing

occasions spaced one week apart. Participants

performed a mean of 117 trials on Day 1 and 120

trials on Day2.

3 RESULTS

Intra-class Correlation Coefficients (ICC) and 95%

Confidence Intervals (CI) were derived to examine

within and between day reliability of the MPD test.

All bilateral hopping techniques yielded moderate to

high ICC values for both within (0.60 to 0.79) and

between day (0.67 to 0.88) reliability.

The only factor which significantly influenced

the sensitivity of subjects to detect changes in floor

height was the hopping technique (bilateral or

alternate, p < 0.05). Comparing across hopping

techniques, the mean MPD was significantly lower

(p<.001) for bilateral hopping than alternate hopping

as per table 1:

Table 1: Result of Linear Mixed Model Analysis of

Between Days MPD Scores (in mm).

MPDmean

Bilateral Hopping

MPDmean

Alternate Hopping

Significance

15.65 26.59 p<.001

4 DISCUSSION

We propose the MPD test is a novel, reliable and

functionally relevant research tool. Furthermore, the

MPD represents a change in the research paradigm

from testing detection of passive, position matching

and force matching of isolated joints (Down et al.,

2007); (Jong et al., 2005); (Lowrey et al., 2010);

(Matre et al., 2002). Instead we examined

proprioception during repeated SSC which may

better represent human gait as it considers an

expected interaction with a non-homogenous

interface between the foot and ground.

For bilateral hopping, ICC values for within and

between day comparisons all exceeded proposed

ICC of 0.6 that has been recommended for any

measure to have clinical utility (Chinn, 1991). This

indicates that the MPD test using bilateral hopping

may have application in the research setting on

single and multiple test occasions.

The increased sensitivity to floor height change

detection during bilateral hopping is an interesting

observation. Our findings are consistent with

previous findings which suggest that gating and

utility of sensory information may be strategy

dependant (Ivanenko et al., 2000).

It may be hypothesised that the bilateral tasks

represent upright stance where we need sensitive and

constant feedback to maintain posture and to safely

initiate movement. Continuous weight bearing

feedback during bipedal stance may be provided via

continuous bilateral comparison of both limbs

contributing to the postural schema.

Conversely, reduced sensitivity to floor height

change detection during alternate hopping suggest

that bipedal gait may allow humans progress their

centre of mass with sufficient proprioceptive

redundancy to overcome large variations in the

interface between the foot and the ground surface

without cognitive perception of the challenge.

5 FUTURE RESEARCH

We have observed a significant difference in

sensitivity to detect floor height changes between

alternating and bilateral SSC. An area for future

research is to investigate whether this difference in

detection is attributable to neurological or

biomechanical factors. Furthermore, given these

observations more research is required to determine

if current “static tests” are valid correlates to

dynamic activities such as gait.

6 CONCLUSIONS

The MPD test has been presented and represents a

change in research focus towards investigating

proprioception using repeated stretch shortening

cycle to model normal lower limb dynamic function.

Development of this tool may allow for further

investigation of functional proprioceptive ability

injured/pathological samples. The MPD test has

been demonstrated as reliable over time and is

therefore an acceptable research tool for use within

and across test occasions.

We observed greater sensitivity of the MPD test

in the bilateral hopping technique. This may reflect

specific sensory requirements for upright stance,

whereas (bipedal) gait may have its own specific

redundancies.

ACKNOWLEDGEMENTS

This research was partly supported by a research

grant from the Neurotrauma Research Program –

WA.

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