Received April 7, 2004
Revised July 2, 2004
Accepted after revision August 13, 2004

¹ Manchester Metropolitan University

^* To whom correspondence should be addressed. E-mail: n.reeves{at}mmu.ac.uk.

	Abstract

This study investigated changes in elderly muscle joint torque-angle relation induced by resistance training. Older adults were assigned to training (n = 9, age 74.3 [3.5] years; mean [SD]) and control (n = 9, age 67.1 [2] years) groups. Leg-extension and leg-press exercises were performed 3 times per week for 14 weeks. Maximal isometric knee extension torque was measured across the knee joint angle range of movement. Vastus lateralis muscle architecture was examined in vivo using ultrasonography. The vastus lateralis muscle fascicle force was estimated from the measured joint torque, enabling construction of the fascicle force-length relation. Electromyographic (EMG) activity was measured from representative agonist and antagonist muscles. Training altered the torque-angle relation a) displacing it by 9-31% towards higher torque values (P < 0.05) and b) shifting the optimal angle from 70 deg (121.4 [61] Nm) before to 60 deg (134.2 [57.2] Nm; P < 0.05) after training. Training also altered the fascicle force-length relation a) displacing it by 11-35% towards higher force values and b) shifting the optimal fascicle length from 83.7 [8] mm (847.9 [365.3] N) before to 93.2 [12.5] mm (939.3 [347.8] N; P < 0.01) after training. The upward displacement of the torque-angle relation was mainly due to a training-induced increase in agonist activation, whilst the shift in the optimal angle was associated with changes in muscle-tendon properties.

Key Words: Exercise, Muscle, Muscle contraction

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