TPT
07-27-2009, 10:51 PM
why the heck do we have asymmetrical muscular development of our legs or simply one side of the body compared to the other. well their are many reasons likely neurological and orthopaedic. the following study by flanagan and salem (2007) provided some insight to what might be occuring as we train.
Bilateral Differences in the Net Joint Torques During the Squat Exercis (http://forums.rxmuscle.com/nsca-jscr/Abstract/2007/11000/Bilateral_Differences_in_the_Net_Joint_Torques.41. aspx)
FLANAGAN, SEAN P.; SALEM, GEORGE J.
The Journal of Strength & Conditioning Research. 21(4):1220-1226, November 2007.
BILATERAL DIFFERENCES IN THE NET JOINT TORQUES DURING THE SQUAT EXERCIS. that there are no b...
Abstract:
Bilateral movements are common in human movement, both as exercises and as daily activities. Because the movement patterns are similar, it is often assumed that there are no bilateral differences (BDs; differences between the left and right sides) in the joint torques that are producing these movements. The aim of this investigation was to test the assumption that the joint torques are equal between the left and right lower extremities by quantifying BDs during the barbell squat. Eighteen recreationally trained men (n = 9) and women (n = 9) completed 3 sets of 3 repetitions of the squat exercise, under 4 loading conditions: 25, 50, 75, and 100% of their 3 repetition maximum, while instrumented for biomechanical analysis. The average net joint moment (ANJM) and maximum flexion angle (MFA) for the hip, knee, and ankle as well as the average vertical ground reaction force (AVGRF) and the average distance from the ankle joint center to the center of pressure (ADCOP) were calculated. Group mean and individual data were analyzed ([alpha] = 0.05). At each joint, there was a significant main effect for side and load, no main effect for gender, with few significant interactions. The hip ANJM was 12.4% larger on the left side, the knee ANJM was 13.2% larger on the right side, and the ankle ANJM was 16.8% larger on the left side. Differences in MFAs between sides were less than 2 degrees for all 3 joints (all p >= 0.20 except for the knee at 75% [p = 0.024] and 100% [p = 0.025]), but the AVGRF and the ADCOP were 6% and 11% larger on the left side. Few subjects exhibited the pattern identified with the group mean data, and no subject exhibited nonsignificant BDs for all 3 joints. These findings suggest that joint torques should not be assumed to be equal during the squat and that few individual subjects follow the pattern exhibited by group mean data.
(C) 2007 National Strength and Conditioning Association
Go to Full Text of this (http://forums.rxmuscle.com/nsca-jscr/Abstract/2007/11000/Bilateral_Differences_in_the_Net_Joint_Torques.41. aspx)
the experimenters tested whether the joint torques of the right and left legs were the same or different.
interestingly, weight of the barbel did not effect the asymmetry in kinematics. we might have thought that as the load increased, more compensations or changes in mechanics would occur. well that didnt happen. if you had a left sided preference, that is what occured no matter how much you lifted.
these data provide us with empirical support to joint mechanical differences of the right and left legs during squats. a strong assumption is that we have bilateral differences in joint movements during most bilateral exercises including presses and pulls.
might this be why many of us have one leg smaller than the other?
Bilateral Differences in the Net Joint Torques During the Squat Exercis (http://forums.rxmuscle.com/nsca-jscr/Abstract/2007/11000/Bilateral_Differences_in_the_Net_Joint_Torques.41. aspx)
FLANAGAN, SEAN P.; SALEM, GEORGE J.
The Journal of Strength & Conditioning Research. 21(4):1220-1226, November 2007.
BILATERAL DIFFERENCES IN THE NET JOINT TORQUES DURING THE SQUAT EXERCIS. that there are no b...
Abstract:
Bilateral movements are common in human movement, both as exercises and as daily activities. Because the movement patterns are similar, it is often assumed that there are no bilateral differences (BDs; differences between the left and right sides) in the joint torques that are producing these movements. The aim of this investigation was to test the assumption that the joint torques are equal between the left and right lower extremities by quantifying BDs during the barbell squat. Eighteen recreationally trained men (n = 9) and women (n = 9) completed 3 sets of 3 repetitions of the squat exercise, under 4 loading conditions: 25, 50, 75, and 100% of their 3 repetition maximum, while instrumented for biomechanical analysis. The average net joint moment (ANJM) and maximum flexion angle (MFA) for the hip, knee, and ankle as well as the average vertical ground reaction force (AVGRF) and the average distance from the ankle joint center to the center of pressure (ADCOP) were calculated. Group mean and individual data were analyzed ([alpha] = 0.05). At each joint, there was a significant main effect for side and load, no main effect for gender, with few significant interactions. The hip ANJM was 12.4% larger on the left side, the knee ANJM was 13.2% larger on the right side, and the ankle ANJM was 16.8% larger on the left side. Differences in MFAs between sides were less than 2 degrees for all 3 joints (all p >= 0.20 except for the knee at 75% [p = 0.024] and 100% [p = 0.025]), but the AVGRF and the ADCOP were 6% and 11% larger on the left side. Few subjects exhibited the pattern identified with the group mean data, and no subject exhibited nonsignificant BDs for all 3 joints. These findings suggest that joint torques should not be assumed to be equal during the squat and that few individual subjects follow the pattern exhibited by group mean data.
(C) 2007 National Strength and Conditioning Association
Go to Full Text of this (http://forums.rxmuscle.com/nsca-jscr/Abstract/2007/11000/Bilateral_Differences_in_the_Net_Joint_Torques.41. aspx)
the experimenters tested whether the joint torques of the right and left legs were the same or different.
interestingly, weight of the barbel did not effect the asymmetry in kinematics. we might have thought that as the load increased, more compensations or changes in mechanics would occur. well that didnt happen. if you had a left sided preference, that is what occured no matter how much you lifted.
these data provide us with empirical support to joint mechanical differences of the right and left legs during squats. a strong assumption is that we have bilateral differences in joint movements during most bilateral exercises including presses and pulls.
might this be why many of us have one leg smaller than the other?