Combining isometric knee extension exercises with hip adduction or abduction does not increase quadriceps EMG activity

Abstract

Objective: To determine if the combined isometric contractions of knee extension/hip adduction and knee extension/hip abduction will elicit a different quadriceps and gluteus medius electromyographic (EMG) pattern as compared to isometric contraction of a uniplanar knee extension exercise. Methods: Eight healthy young adult volunteers without history of knee or quadriceps injury participated. Surface EMG data were collected from the vastus medialis oblique (VMO), vastus lateralis (VL), and gluteus medius (Gmed) muscles of the dominant leg of each subject during three single leg, weight bearing, isometric exercises (uniplanar knee extension, knee extension/hip adduction, knee extension/hip abduction). All exercises were performed at a position of 60˚knee flexion. Three trials lasting 5 s each were performed for each of the three exercises. EMG data from each muscle were integrated and the maximum root mean square activity over a 0.5 s window for each trial was averaged. Analyses of variance were performed with exercise (straight extension, extension/adduction, extension/abduction) as the independent variable and VMO, VL, and Gmed activity and VMO:VL ratio as dependent variables. Results: A significant main effect for exercise was found for the VMO (p = 0.006) and VL (p = 0.02), but not the Gmed (p = 0.25) or the VMO:VL ratio (p = 0.13). For the VMO and VL, the uniplanar knee extension task produced significantly more EMG activity than the extension/adduction or extension/abduction tasks. Conclusions: Uniplanar knee extension exercises may be more appropriate than combining isometric knee extension exercises with hip adduction or abduction when eliciting maximal VMO and VL contractions.

Joint stabilisers or moment actuators: The role of knee joint muscles while weight-bearing

“…Their symmetrical activation patterns suggest that they stabilise against hip adduction and hip extension loads that would, respectively, cause valgus alignment and posterior femoral translation. This observation is supported by Earl et al (2001) and Hertel et al (2004) who found that vastii activation levels did not differ when hip adduction or abduction components were added to a squatting exercise.…”

Ativação muscular estabilizadora da patela e do quadril durante exercícios de agachamento em indivíduos saudáveis

“…The contraction of GMed in these situations is due, probably, to its function as pelvic stabilizer and to the control of the internal rotation of the femur [24][25][26] . These data agree with the findings of Hertel et al 5 that found that the addition of isometric contraction of hip adduction and abduction to unipodal squat have no effect on the electrical activity of GMed. However, despite the similarities of the result, the experimental conditions of the studies were different since in the present study volunteers kept both feet on the ground, had the back supported by a ball and had an added load of 25% of the body weight.…”

Does level of load affect relative activation levels of vastus medialis oblique and vastus laterialis?

“…As no previous study has attempted this type of investigation it is difficult to qualify these findings. A number of studies have found a similar VMO:VL ratio during maximal contraction [10,16,23,31]. Worrell et al [31] found a ratio of 0.94 at 60% MIVC which is in line with the current study, though Souza and Gross [27] found it to be 0.96 for 25% MIVC.…”