Article

We investigated the effects of four weeks of training using a knee extension with
hip adduction (KEWHA) exercise in asymptomatic participants. In addition, we
compared different methods of electromyographic (EMG) onset-time detection.
Eighteen participants who achieved earlier activation of the vastus lateralis
(VL) muscle compared to that of the vastus medialis obliquus (VMO) muscle
performed the isometric KEWHA exercise in the sitting position for four weeks. A 15 degrees hip adduction was added to the existing knee extension in the KEWHA
exercise. EMG onset times were detected using a computer-analyzed system and
evaluated using two methods in which the thresholds for activity onset were set
at two and three standard deviations (SDs) of the mean baseline activity. No
significant difference in the EMG onset-time for the VMO muscle was observed
compared to that of the VL muscle between the pre- and post-tests (p>0.05) when
data at 2SDs of the mean baseline activity were analyzed. However, a significant
difference in the onset times for the VMO muscle and VL muscle was found between
the pre- and post-tests (p<0.05) when data at 3SDs of the mean baseline activity
were analyzed. In addition, less variation was observed in data analyzed at 3SDs
compared to that of the data at 2SDs. The normalized VMO:VL muscle ratio was not
significantly different between the pre- and post-tests. These findings show that
the KEWHA exercise may decrease the difference between the onset times of VMO and
VL muscles. In addition, we suggest that task-specific EMG onset-time detection
methods are required to minimize variations in the data obtained during the
recording of muscle activation.
CI - Copyright A(c) 2011 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS