Here are a few extracts from another interesting article from the latest NSCA
Journal on the effect of a weightlifting belt on squatting mechanics and
performance, which should make those aligned against belt usage rethink some
of their somewaht rigid opinions. Note especially that this research
suggests that the use of a weight belt may improve a lifter's explosive power
by increasing the speed of the movement without compromising the joint range
of motion or overall lifting technique.
This calibre of information is another good reason for joining the NSCA.
------------------------------------------------
Zink AJ, Whiting WC, Vincent WJ, & Alice J. Mclaine The Effects of a
Weight Belt on Trunk and Leg Muscle Activity and Joint Kinematics During the
Squat Exercise J of Strength & Conditioning Research: Vol. 15, No. 2, pp.
235–240.
ABSTRACT
Fourteen healthy men participated in a study designed to examine the effects
of weight-belt use on trunk- and leg-muscle myoelectric activity (EMG) and
joint kinematics during the squat exercise. Each subject performed the
parallel back squat exercise at a self-selected speed according to his own
technique with 90% of his 1RM both without a weight belt (NWB) and with a
weight belt (WB). Myoelectric activity of the right vastus lateralis, biceps
femoris, adductor magnus, gluteus maximus, and erector spinae was recorded
using surface electrodes. Subjects were videotaped from a sagittal plane view
while standing on a force plate. WB trials were completed significantly
faster (p < 0.05) than NWB trials over the entire movement and in both the
downward phase (DP) and upward phase (UP). No significant differences in EMG
were detected between conditions for any of the muscle groups or for any
joint angular kinematic variables during either phase of the lift. The total
distance traveled by the barbell both anteriorly and vertically was
significantly greater (p < 0.01) in the WB condition than the NWB condition.
The velocity of the barbell was significantly greater (p < 0.01) both
vertically and horizontally during both the DP and UP in the WB condition as
compared with the NWB condition. These data suggest that the use of a weight
belt during the squat exercise may affect the path of the barbell and speed
of the lift without altering myoelectric activity. This suggests that the use
of a weight belt may improve a lifter's explosive power by increasing the
speed of the movement without compromising the joint range of motion or
overall lifting technique.
DISCUSSION
The increase in anterior displacement of the barbell in the bottom position
decreases the moment arm and the torque generated about the knee while
increasing the moment arm and the torque generated about the hip. Although
less force would be needed to counter the torque at the knee, a greater
counter-torque would need to be generated by the back and hip extensors to
compensate for the increased moment arm at the hip. However, there was a
trend toward decreased myoelectric activity of the GM and ES. Perhaps the
weight belt served to partially support the load even with the increased
barbell anterior displacement and subsequent torque generated about the hip.
This difference in bar position induced by weight-belt use may indicate a
subtle change in squat technique that results in different muscle recruitment
with the GM and ES recruited less and the BF and AM recruited more. Further
study is needed to resolve these issues.
The lack of significant differences in EMG between conditions may be
attributed to the lack of large differences in mEMG and the high SDs in the
mEMG data. This may be due in part to subject variability in squat techniques
related to their different sport backgrounds and training regimens. The
high-bar squat technique employed by weightlifters has been reported to
differ from the low-bar squat technique employed by powerlifters in both
joint angles and joint moments for the hip and knee (7) . Differences in
squat technique such as those exhibited between low-bar and high-bar
squatters may have existed between subjects in this study, and therefore may
be partially responsible for the high variability in EMG.
The use of a weight belt during the squat exercise does not appear to affect
the myoelectric activity of the leg or back extensor muscles. Similarly,
individual angular and linear joint kinematics were not significantly changed
with the use of a weight belt. However, the total distance that the barbell
traveled anteriorly and vertically was greater and the lifts were performed
at a faster rate during both phases of the lift when a weight belt was worn.
This suggests that weight-belt use during the squat exercise can alter the
speed of the lift, the path the barbell travels, and the position of the
barbell at the end of the downward phase without significantly altering the
overall muscle activity.........
PRACTICAL APPLICATIONS
One of the best ways to improve performance and reduce the risk of injury
during heavy lifts is to maintain proper lifting technique. Comprehensive
assessment of lifting technique must consider anatomical, mechanical, and
physiological aspects of the lift.
This study showed that at near-maximal loads, lifters using a weight belt
maintain a horizontal barbell position closer to the knee and farther from
the hip at the bottom of the lift. This bar position would result in greater
torques about the hip and lesser torques at the knee. In addition, the fact
that belted lifts showed more vertical bar displacement over a shorter time
interval, when compared to non-belted lifts, suggests that lifters wearing a
weight belt perform more mechanical work and generate more power. Further
study is needed to confirm these observations and determine whether these
kinetic differences are of practical relevance.
The experienced lifters in this study showed biomechanical differences
between the WB and NWB conditions. From a performance perspective, the faster
lifting associated with weight-belt use may provide a slight positive benefit
in terms of increased power output. In contrast, an argument can be made that
the slower and more controlled movements without belt use may be preferred in
terms of reducing risk of injury. Use of this study's results should be made
with care. Interpretation and application of the data may differ depending on
the target population (e.g., athletes in general, powerlifters) and training
goals (e.g., general fitness, increased power output)...........
--------------------------
Dr Mel C Siff
Denver, USA
http://groups.yahoo.com/group/Supertraining/
|
