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| Effect of elastic energy and myoelectrical
potentiation of triceps surae during stretch-shortening cycle
exercise. |
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| Bosco C, Tarkka I, Komi PV |
| 1982 |
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| NCBI |
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Stretching of an activated muscle prior to its shortening enhances
its performance during the concentric contraction. This phenomenon
has been interpreted to be primarily due to the utilization of elastic
energy stored in the series elastic elements of the muscle during
the stretch. However, reflex potential has also been suggested as
an additional cause for performance increase. To examine this hypothesis
five subjects performed maximal vertical jumps on a force platform
from two different starting positions: (a) maximal plantar flexion
from a static position (SJ) (pure concentric contraction), (b) a toe-standing
position with preliminary counter-movement (CMJ). In this condition
the calf muscles were actively stretched before concentric work. In
both conditions the knee and hip joints were fixed. The results indicated
that the utilization of the stretch-shortening cycle enhanced the
performance over that of the pure concentric contraction (P less than
0.001). Similarly, the EMG recording demonstrated that in all five
subjects the myoelectrical activity of the calf muscles (mm. gastrocnemius
and soleus) was potentiated during the concentric phase in CMJ when
compared to SJ (P less than 0.001). Therefore, the increase in performance
was attributed to a combination of utilization of elastic energy and
myoelectrical potentiation of muscle activation. |
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