title: Isokinetic eccentric exercise can induce skeletal muscle injury within the physiologic excursion of muscle-tendon unit: a rabbit model.
abstract: OBJECTIVE
  Intensive eccentric exercise can cause muscle damage. We simulated an animal model of isokinetic eccentric exercise by repetitively stretching stimulated triceps surae muscle-tendon units to determine if such exercise affects the mechanical properties of the unit within its physiologic excursion.
  
  
  METHODS
  Biomechanical parameters of the muscle-tendon unit were monitored during isokinetic eccentric loading in 12 rabbits. In each animal, one limb (control group) was stretched until failure. The other limb (study group) was first subjected to isokinetic and eccentric cyclic loading at the rate of 10.0 cm/min to 112% (group I) or 120% (group II) of its initial length for 1 hour and then stretched to failure. Load-deformation curves and biomechanical parameters were compared between the study and control groups.
  
  
  RESULTS
  When the muscle-tendon unit received eccentric cyclic loading to 112%, changes in all biomechanical parameters - except for the slope of the load-deformation curve - were not significant. In contrast, most parameters, including the slope of the load-deformation curve, peak load, deformation at peak load, total energy absorption, and energy absorption before peak load, significantly decreased after isokinetic eccentric cyclic loading to 120%.
  
  
  CONCLUSIONS
  We found a threshold for eccentrically induced injury of the rabbit triceps surae muscle at between 12% and 20% strain, which is within the physiologic excursion of the muscle-tendon units. Our study provided evidence that eccentric exercise may induce changes in the biomechanical properties of skeletal muscles, even within the physiologic range of the excursion of the muscle-tendon unit.
authors: Department of Orthopedic Surgery, Taipei City Hospital, Taipei, Taiwan. DAJ23@tpech.gov.tw
authors: Yang-Hwei
authors: YH
authors: Tsuang
authors: Shui-Ling
authors: SL
authors: Lam
authors: Lien-Chen
authors: LC
authors: Wu
authors: Chang-Jung
authors: CJ
authors: Chiang
authors: Li-Ting
authors: LT
authors: Chen
authors: Pei-Yu
authors: PY
authors: Chen
authors: Jui-Sheng
authors: JS
authors: Sun
authors: Chien-Che
authors: CC
authors: Wang
references: Am J Physiol. 1998 May;274(5):R1300-8
references: 9644043
references: Clin Biomech (Bristol, Avon). 1996 Jan;11(1):46-50
references: 11415598
references: Am J Sports Med. 1981 Mar-Apr;9(2):103-6
references: 7223918
references: Am J Sports Med. 1983 Jul-Aug;11(4):249-52
references: 6614296
references: Eur J Appl Physiol Occup Physiol. 1999 Sep;80(4):386-93
references: 10483811
references: Am J Sports Med. 1995 Jan-Feb;23(1):65-73
references: 7726353
references: Clin Biomech (Bristol, Avon). 1996 Sep;11(6):343-347
references: 11415643
references: Phys Sportsmed. 1982 Nov;10(11):81-86
references: 29291315
references: J Appl Physiol (1985). 1996 Mar;80(3):1006-13
references: 8964718
references: Skeletal Radiol. 1996 Jan;25(1):3-11
references: 8717112
references: Clin Sci (Lond). 1983 Jan;64(1):55-62
references: 6822050
references: Am J Sports Med. 1988 Mar-Apr;16(2):123-9
references: 3377095
references: Pain. 1987 Aug;30(2):233-242
references: 3670875
references: J Appl Physiol (1985). 1986 Nov;61(5):1864-8
references: 3491061
references: Clin Sports Med. 1997 Jul;16(3):419-34
references: 9209819
references: Med Sci Sports Exerc. 2000 Feb;32(2):370-8
references: 10694119
references: J Morphol. 1984 Oct;182(1):95-113
references: 6492171
references: Med Sci Sports Exerc. 2000 Apr;32(4):820-9
references: 10776902
references: J Muscle Res Cell Motil. 1998 Apr;19(3):237-45
references: 9583364
references: J Appl Physiol (1985). 1987 Oct;63(4):1381-6
references: 3693172
references: Clin Biomech (Bristol, Avon). 1994 Sep;9(5):310-4
references: 23916300
references: J Appl Physiol (1985). 1993 Feb;74(2):520-6
references: 8458765
references: J Appl Physiol (1985). 1986 Jul;61(1):293-9
references: 3733615
references: Am J Sports Med. 1993 Jul-Aug;21(4):517-22
references: 8368411
references: Int J Sports Med. 1983 Aug;4(3):170-6
references: 6629599
references: Med Sci Sports Exerc. 1995 Oct;27(10):1378-84
references: 8531608
references: J Biomech. 1989;22(8-9):943-8
references: 2613728
references: Sports Med. 1999 Mar;27(3):157-70
references: 10222539
references: Sports Med. 1995 Mar;19(3):202-22
references: 7784759
references: Med Sci Sports Exerc. 1990 Aug;22(4):436-43
references: 2205779
references: Int J Sports Med. 1997 Oct;18 Suppl 4:S314-7
references: 9391847
references: Am J Sports Med. 1996;24(6 Suppl):S2-8
references: 8947416
references: Clin Biomech (Bristol, Avon). 1998 Jan;13(1):48-53
references: 11415770
references: J Formos Med Assoc. 1994 Jan;93(1):51-5
references: 7915582
references: J Physiol. 1989 May;412:415-27
references: 2600839
references: J Physiol. 1978 Mar;276:449-65
references: 306433