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  • Title: Normalized lengthening peak torque is associated with temporal twitch characteristics in elderly women but not young women.
    Author: Cannon J, Kay D, Tarpenning KM, Marino FE.
    Journal: Acta Physiol (Oxf); 2006 Sep; 188(1):53-62. PubMed ID: 16911253.
    Abstract:
    AIM: To determine if greater normalized torque during maximal effort lengthening actions in elderly women compared with young women is related to age-associated adjustments in neural activation and/or contractile function. METHODS: The right knee extensors of 14 young women (21-30 years) and 12 elderly women (65-78 years) were assessed for isometric, shortening and lengthening peak torque, electromyography (EMG) activity, and isometric twitch contractile properties. Knee extensor contractile tissue volume was determined using magnetic resonance imaging. RESULTS: Normalized torque was determined as peak torque per unit of knee extensor contractile tissue volume. Normalized torque during the isometric and shortening actions was similar between age groups (P > 0.05); however, lengthening normalized torque was significantly higher for the elderly women (P < 0.05). In the young women, a significant relationship existed between normalized torque and EMG for all muscle actions (P < 0.05), while no association was found between normalized torque and temporal twitch characteristics for any muscle action (P > 0.05). In the elderly women, a significant relationship existed between normalized torque and EMG for the isometric and shortening muscle actions (P < 0.05), but not for lengthening normalized torque and EMG (P > 0.05). Furthermore, no association existed between isometric and shortening normalized torque, and temporal twitch characteristics in the elderly women (P > 0.05); however, a significant relationship existed between lengthening normalized torque, and the rate of relaxation and contraction duration (P < 0.05). CONCLUSIONS: The greater capacity to develop lengthening peak torque relative to contractile tissue volume in the elderly women appeared to be associated with age-related adjustments in the temporal twitch characteristics rather than neural activation.
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