Submitted to the 2008 Annual Meeting of the American
College of Sports Medicine for presentation
People
with Peripheral Neuropathy Have Normal Motor Control Capacity
Shinichi Amano, Nikita
Shah, Richard Magill, Jan M. Hondzinski, Li Li, FACSM
Peripheral
Neuropathy (PN) causes loss of coordination, balance, and gait impairments. Postural
balance is a severe problem among people with PN. However, the motor and/or
sensory contribution to balance impairment is not clear. Purpose: This study was designed to examine whether impaired
balance control in people with PN is due to motor impairments. Method: We recruited 10 people in each subject
group: PN, healthy age-matched (HO) and young (HY). An IRB approved informed
consent was obtained prior to data collection. While standing on a force
platform with visual feedback of the center of pressure (COP), subjects were
instructed to move their COP in either an anteroposterior
or mediolateral direction in order to move the real-time
visual COP cursor to two target locations on opposite sides of a computer
monitor. Target locations were within 60% of the subject¡¯s base of support. A target
appeared at one location, disappeared once ¡°reached¡±
with the cursor, then reappeared at the opposing location. Subjects had to
reach target locations 5 times each within a trial. The averaged reach time (seconds)
was measured. The subjects performed 20 trials with at least 2 minutes rest
between trials. Twenty reaching times were modeled using an exponential
function (RT = a + b*e(-i/tao)) with an optimization
process, where a, b, and tao were adjusted (i=1-20). Simulated initial (RTini, i=1) and
final (RTfin, i=20)
reaching times were calculated and used in final results. ANOVA and Tukey¡¯s HSD were used for analysis. Result: Although there was a significant difference in RTini
between the HY and HO groups (1.81¡À.16, 4.07¡À.64), the PN group (2.93¡À.42) did not
significantly differ from either the HY or HO group. At the end of the
training, HY (.63¡À.04) achieved significantly (P < .02) shorter
RTfin
than both HO and PN (1.03¡À.10, 1.0¡À.1) with no difference between the latter
two. We observed no differences in the time constant (tao) among the three groups (HY = 3.7¡À.6, HO = 2.5¡À0.4, PN
= 2.7¡À.4). Conclusion: As indicated
by time spent using COP to reach set target locations and the characteristics
of learning this novel task, 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 muscle control required for balance. Balance
problems in people with PN are mostly affected by their sensory loss.