Adarq.org
Performance Area => Article & Video Discussion => Topic started by: Raptor on September 24, 2012, 04:46:20 pm
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http://www.strengthandconditioningresearch.com/2012/09/11/bilateral-deficit/
I found this very interesting:
Ground reaction forces during jumping
The researchers reported that the peak vertical ground force of the right leg attained in the simulated two-leg jump was 15.6 ± 1. N/kg while the left leg was 14.2 ± 1.2N/kg), because of right-leg dominance in this group of subjects.
However, in the simulated one-leg jump, the force was 19.6 ± 2.2N/kg. So the right leg during the two-legged jump only produced 79% of the force that was produced by the same leg during the one-legged jump.
Basically saying that you need to really be rested (have close to 100% "battery" or CNS) if you really want to perform off one leg, whereas bilateral stuff requires less peak intensity but more overall CNS burn.
Even more, since we're trying to improve the neural drive and "explosiveness" during our plyo workouts, it should make more sense to use unilateral plyometric exercises since the most neural drive occurs during these movements.
Anyway,
What did the researchers conclude?
The researchers concluded that the ground reactions force produced by each leg during the two-legged jump were less than that produced during the one-leg jump. This was caused by lower joint moments.
The researchers concluded that while it is possible that the lower joint moments in the two-leg jump were smaller than those in the one-leg jump because of reduced neural drive, peak EMG levels in the two-leg jump were only slightly lower than those in the one-legged jump. They therefore suggest that a reduction in neural drive is unlikely to be the cause of the reduced moments.
Rather, the researchers suggest that because some of the muscles must have shortened at higher velocities in the two-legged jump, this caused them to produce lower forces because of the force-velocity relationship. They note that this was the result produced by their computer simulation, as enforcing the same muscle-shortening velocities in both jump variations eliminated 75% of the difference in jump height.
The study, summarized
Humans jump higher using two legs than with one leg. However, they cannot jump twice as high with two legs as with one leg. This concept is called the “bilateral deficit”.
This study shows that 75% of the bilateral deficit can be explained by the fact that one-legged jumping is characterized by longer ground contact times, and the muscles therefore have greater time to produce force (as dictated by the force-velocity relationship).
The remaining 25% of the bilateral deficit can be explained by the fact that during a one-legged jump, the muscles are activated to a greater degree right off the bat because one leg is supporting the body, compared to two legs supporting bodyweight in the case of a bilateral jump.
Finally, this study refutes previous research showing that reduced muscle EMG explains the bilateral deficit. In this study, peak muscle activity during a bilateral jump was generally only reduced by around 5% compared to a one-legged jump.
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http://www.strengthandconditioningresearch.com/2012/09/11/bilateral-deficit/
I found this very interesting:
Ground reaction forces during jumping
The researchers reported that the peak vertical ground force of the right leg attained in the simulated two-leg jump was 15.6 ± 1. N/kg while the left leg was 14.2 ± 1.2N/kg), because of right-leg dominance in this group of subjects.
However, in the simulated one-leg jump, the force was 19.6 ± 2.2N/kg. So the right leg during the two-legged jump only produced 79% of the force that was produced by the same leg during the one-legged jump.
Basically saying that you need to really be rested (have close to 100% "battery" or CNS) if you really want to perform off one leg, whereas bilateral stuff requires less peak intensity but more overall CNS burn.
Even more, since we're trying to improve the neural drive and "explosiveness" during our plyo workouts, it should make more sense to use unilateral plyometric exercises since the most neural drive occurs during these movements.
Anyway,
What did the researchers conclude?
The researchers concluded that the ground reactions force produced by each leg during the two-legged jump were less than that produced during the one-leg jump. This was caused by lower joint moments.
The researchers concluded that while it is possible that the lower joint moments in the two-leg jump were smaller than those in the one-leg jump because of reduced neural drive, peak EMG levels in the two-leg jump were only slightly lower than those in the one-legged jump. They therefore suggest that a reduction in neural drive is unlikely to be the cause of the reduced moments.
Rather, the researchers suggest that because some of the muscles must have shortened at higher velocities in the two-legged jump, this caused them to produce lower forces because of the force-velocity relationship. They note that this was the result produced by their computer simulation, as enforcing the same muscle-shortening velocities in both jump variations eliminated 75% of the difference in jump height.
The study, summarized
Humans jump higher using two legs than with one leg. However, they cannot jump twice as high with two legs as with one leg. This concept is called the “bilateral deficit”.
This study shows that 75% of the bilateral deficit can be explained by the fact that one-legged jumping is characterized by longer ground contact times, and the muscles therefore have greater time to produce force (as dictated by the force-velocity relationship).
The remaining 25% of the bilateral deficit can be explained by the fact that during a one-legged jump, the muscles are activated to a greater degree right off the bat because one leg is supporting the body, compared to two legs supporting bodyweight in the case of a bilateral jump.
Finally, this study refutes previous research showing that reduced muscle EMG explains the bilateral deficit. In this study, peak muscle activity during a bilateral jump was generally only reduced by around 5% compared to a one-legged jump.
Regarding plyos:
I would imagine, from experience and observation, that single leg plyos (max effort consecutive leg bounds) yields greater permanent improvements in strength + hypertrophy than double leg bounds/depth jumps.
Regarding double leg bounds / MR tucks, I think I should have focused more on forcing myself to land lower, closer to half squat.. I spent too much time at the shorter range of movement, even though I really felt forcing depth on those was pretty beneficial.
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Somewhat related articles:
http://www.ncbi.nlm.nih.gov/pubmed/15705051
http://www.ncbi.nlm.nih.gov/pubmed/22222320