Content area
Full Text
ABSTRACT. Stoutenberg, M., A. P. Pluchino, F. Ma, J. E. Hoctor, and J.F. Signorile. The impact of foot position on electromyographical activity of the superficial quadriceps muscles during leg extension. J. Strength Cond. Res. 19(4)931-938. 2005.-This study investigated variations in electromyographic (EMG) responses of the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) due to foot position during leg extension. Twenty-four men and women (23.67 ± 4.02 years) performed 8 repetitions at 70% of 8 repetition maximum with their leg medially rotated, laterally rotated, and neutral. Repeated-measures analyses of variance indicated that the highest normalized root mean square (NrmsEMG) for the VM and VL occurred with medial rotation, and the highest NrmsEMG for the RF occurred with lateral rotation. Significant NrmsEMG increases and median power frequency decreases occurred across repetitions regardless of foot position. Therefore, medial rotation produced the greatest muscle activation for the VL and VM, whereas lateral rotation produced the greatest activation in the RF. These findings are applicable to athletes or bodybuilders who are seeking to selectively increase either the size or performance of a specific muscle of the quadriceps group.
KEY WORDS. vastus medialis, vastus lateralis, rectus femoris, constant load resistance exercise, muscle utilization pattern, fatigue
INTRODUCTION
Lifters have long believed that changes in limb positions or joint angles during the performance of a particular exercise can maximize the effects of that exercise on specific muscles. Among the most common muscles targeted are those of the quadriceps group as lifters attempt to increase the peak or outward sweep of the vastus lateralis (VL) or the teardrop appearance of the vastus medialis (VM). Additionally, specific quadriceps muscles may be targeted because of their importance in a particular sport. For example, the rectus femoris (RF) is an important hip flexor used during cycling (5), whereas both the VL and the VM are important power producers during speed skating (13).
One of the most common dynamic, constant-resistance exercises used to target the quadriceps is the bilateral leg extension using either weight-stack or plate-loaded machines. It is commonly believed that changing the foot position during this open-chain leg exercise allows the lifter to emphasize the use of one quadriceps muscle over the others. Proponents of adjusting the foot position during leg extensions...