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document
Isometric contractions reduce plantar flexor moment , Achilles tendon stiffness , and neuromuscular activity but remove the subsequent effects of stretch . The effects of isometric contractions and passive stretching on muscle-tendon mechanics and muscle activity were studied in 16 healthy human volunteers . First , peak concentric and passive ankle joint moment data were recorded on an isokinetic dynamometer with electromyographic monitoring of the triceps surae ; real-time motion analysis of the lower leg and ultrasound imaging of the Achilles-medial gastrocnemius muscle-tendon junction were simultaneously conducted . Second , the subjects performed six 8-s maximal voluntary isometric contractions ( MVICs ) before repeating the passive and active trials . Although there was no decrease in isometric joint moment after MVICs , peak concentric moment was significantly reduced ( 11.5 % , P < 0.01 ) . This was accompanied by , and correlated with ( r = 0.90 , P < 0.01 ) , significant reductions in peak triceps surae electromyographic amplitude ( 21.0 % , P < 0.01 ) . Achilles tendon stiffness ( 10.9 % , P < 0.01 ) and passive joint moment ( 4.9 % , P < 0.01 ) were also significantly reduced . Third , the subjects performed three 60-s static plantar flexor stretches before being retested 2 and 30 min after stretch . The stretch protocol caused no significant change in any measure . At 30 min after stretching , significant recovery in concentric moment and muscle activity was detected at dorsiflexed joint angles , while Achilles tendon stiffness and passive joint moment remained significantly reduced . These data show that the performance of MVICs interrupts the normal stretch-induced losses in active and passive plantar flexor joint moment and neuromuscular activity , largely because concentric strength and tendon properties were already affected . Importantly , the decrease in Achilles tendon stiffness remained 30 min later , which may be an important etiological factor for muscle-tendon strain injury risk .
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Intervention_Physical
Isometric contractions
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Intervention_Physical
isometric contractions
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Intervention_Physical
passive stretching
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Intervention_Control
on muscle-tendon mechanics and muscle activity
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Intervention_Physical
maximal voluntary isometric contractions ( MVICs
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Intervention_Physical
static plantar flexor stretches
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Outcome_Physical
plantar flexor moment , Achilles tendon stiffness , and neuromuscular activity
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Outcome_Physical
isometric joint moment
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Outcome_Physical
peak concentric moment
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Outcome_Physical
peak triceps surae electromyographic amplitude
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Outcome_Physical
Achilles tendon stiffness
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Outcome_Physical
passive joint moment
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Outcome_Physical
concentric moment and muscle activity
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Outcome_Physical
Achilles tendon stiffness
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Outcome_Physical
passive joint moment
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Outcome_Physical
Achilles tendon stiffness
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Participant_Condition
16 healthy human volunteers .