Presented at 2008 ACSM Annual Meeting
People with Peripheral
Neuropathy Have Normal
Motor Control Capacity
Shinichi Amano, B.S.
Nikita Shah, B.S.
Richard Magill, Ph.D.
Jan M. Hondzinski, Ph.D.
Li Li, Ph.D., FACSM
Peripheral Neuropathy (PN)
• Progressive degeneration of peripheral
nerves
(Lacomis, 2002)
• High prevalence
• 14.8% of the U.S. population aged over 40
(Gregg et al, 2004)
• Increased risk of falling
– 15 times more likely to suffer a fall
(Cavanagh et al, 1992)
Balance and Peripheral Neuropathy
• Increased sway (Kavounoudias et al, 2001)
• Higher ankle inversion / eversion proprioceptive
threshold
– 5 × higher than people without PN
(Van Den Bosch et al, 1995)
• Reduced ankle strength
(Gutierrez et al, 2001)
However…
• Most studies focused on sensory problems
• Motor deficits in people with PN is still not clear.
Purposes and Hypotheses
Primary Purpose
To examine the effect of aging and PN on
individual’s balance control capacity
Primary Hypotheses
1.People with PN have the same level of motor
control capacity for balance, compared to the
age-matched counterparts.
2.The young can control balance more efficiently than
people with PN and the elderly.
Purposes and Hypotheses
Secondary Purpose
To examine if aging and PN affects
individual’s ability to learn a task of
controlling their center of pressure (COP)
Secondary Hypothesis
Aging nor PN does not affect the ability to
learn the task of controlling their COP.
Methods – Participants • 3 Groups:
Table 1. Group Characteristics
Group
PN
HO
HY
n
10
10
10
Mean Age
66.8
(±12.7)
71.8
(±5.7)
21.4
(±0.9)
Mean height
(m)
1.70
(±0.14)
1.69
(±0.13)
1.71
(±0.08)
Mean weight
(kg)
80.5
(±24.7)
75.7
(±21.6)
64.4
(±11.4)
1. Peripheral
Neuropathy group
(PN)
2. Age-matched
Healthy elderly
group (HO)
3. Healthy young group
(HY)
Active Target
(at 60% of BOS)
Base of Support
(BOS)
Real-time
COP cursor
Monitor
(17-inch)
AMTI
Force Platform
(50Hz)
AMTI Balance Trainer
(COP feedback Software)
Fig. 1 Experimental Set up (Medio-lateral Direction)
Methods - Protocols • Sway movement test with real-time feedback of
center of pressure (COP) location
 Two target locations: Must move COP cursor to the active
target to activate the other target on the opposite side
 Must reach the target 5 times for each side
 Measured the average of 10 reaching times (RT)
 Mediolateral (M/L) and
Anteroposterior (A/P)
direction
 Measured 20 trials
Methods
-Motor Performance Curve ModelingAverage Reaching Time (sec)
2.5
RT = a + b*e – i / τ
2.0
( i; Trial #, τ; Time constant )
1.5
1.0
0.5
Average RT in each trial
0.0
0
5
10
15
20
Trials
Fig. 2 Representative example of motor performance curve
25
Methods
-Motor Performance Curve ModelingAverage Reaching Time (sec)
2.5
RT = a + b*e –i / τ
2.0
1.5
Increased a
1.0
0.5
Decreased a
0.0
0
5
10
15
20
Trials
Fig. 3 Effect of constant “a” on motor performance curve
25
Methods
-Motor Performance Curve ModelingAverage Reaching Time (sec)
2.5
RT = a + b*e –i / τ
2.0
Increased τ
1.5
1.0
Decreased τ
0.5
0.0
0
5
10
15
20
Trials
Fig. 4 Effect of time constant on motor performance curve
25
Methods
- Statistical Analysis  the dependent variables:
1. Simulated RTini ( = a + b*e - 1 / τ )
2. Simulated RTfin ( = a + b*e – 20 / τ )
3. 
 3 (groups) × 2 (directions) two-way ANOVA
 Post-hoc test: Tukey’s HSD test
 α level: 0.05
Results
Simulated Initial Reaching Time
(RTini = a + b*e -1 / τ )
• HY << HO
• No significant
difference b/w PN and
either HY or HO
* p < 0.05
Results
Simulated Final Reaching Time
(RTfin = a + b*e – 20 / τ )
• No significant
difference b/w PN
and HO
• HY << HO & PN
* p < 0.05
Results
Time Constant ( τ )
(RTfin = a + b*e (- i / τ) )
• No significant
difference among
groups
Discussions
•
•
Significantly shorter RTfin in HY, compared to PN &
HO
No significant difference in RTfin between PN and
the age-matched control.
People with PN had same level of motor
control capacity for balance, as the agematched control.
•
No significant difference in τ among three groups
Neither aging nor PN affect the ability to
learn the task of controlling COP with visual
feedback.
Conclusions
• People with PN could control their COP, with
the help of visual feedback, as well as their
age-matched counterparts.
• This study suggests that people affected by
PN do not lose motor control required for
balance. Balance problems in people with PN
are probably more affected by their sensory
loss.
Methods
-Balance Test-
Fig. 2 Experimental Set up (Balance Test)
Methods
- Statistical Analysis  the dependent variables:
1. Average Velocity (cm/sec)
2. Area 95 (cm2)
 3 (groups) × 3 (conditions)
two-way ANOVA with repeated measures
 Post-hoc test: Tukey’s HSD test
 α level: 0.05
With Target
Eyes Open
Eyes Closed
20.00
15.00
10.00
5.00
0.00
PN
HY
HO
Supplemental materials
Base of Support
(BOS)
Real-time
COP cursor
Active Target
(Diameter: 5% of BOS)
Monitor
(17-inch)
AMTI
Force Platform
(50Hz)
AMTI Balance Trainer
(COP feedback Software)
Fig. 2 Experimental Set up (Balance Test)
Inclusion Criteria
• PN Group
– Physician-diagnosed peripheral neuropathy
– Absence of any other disease or injury that may
affect balance
– No vision problems
• Control Group (HY & HO)
– No PN or any other disease or injury that may
affect balance