Repeated electrical stimulated isometric muscle contractions induced sarcomere-level damage, evidenced by z-line disruption and increased creatine kinase activity (P<0.05).
Does repeated electrically stimulated isometric contraction induce muscle damage at the level of the sarcomere in young healthy men?
Repeated electrically stimulated isometric muscle contractions can induce muscle damage at the myofiber and sarcomere levels without lengthening contractions.
p-value: p=<0.05
It is unknown whether muscle damage at the level of the sarcomere can be induced without lengthening contractions. To investigate this, we designed a study where seven young, healthy men underwent 30 min of repeated electrical stimulated contraction of m. gastrocnemius medialis, with the ankle and leg locked in a fixed position. Two muscle biopsies were collected 48 h later: one from the stimulated muscle and one from the contralateral leg as a control. The biopsies were analyzed immunohistochemically for inflammatory cell infiltration and intermediate filament disruption. Ultrastructural changes at the level of the z-lines were investigated by transmission electron microscopy. Blood samples were collected for measurement of creatine kinase activity, and muscle soreness was assessed in the days following stimulation. The biopsies from the stimulated muscle revealed macrophage infiltration and desmin-negative staining in a small percentage of myofibers in five and four individuals, respectively. z-Line disruption was evident at varying magnitudes in all subjects and displayed a trend toward a positive correlation (r = 0.73, P = 0.0663) with the force produced by stimulation. Increased muscle soreness in all subjects, combined with a significant increase in creatine kinase activity (P < 0.05), is indirectly suggestive of muscle damage, and the novel findings of the present study, i.e., 1) macrophages infiltration, 2) lack of desmin staining, and 3) z-line disruption, provide direct evidence of damage at the myofiber and sarcomere levels. These data support the hypothesis that muscle damage at the level of the sarcomere can be induced without lengthening muscle contractions.
Mackey et al. (Fri,) conducted a other in Healthy (n=7). Repeated electrical stimulated isometric muscle contractions vs. Contralateral leg was evaluated on Muscle damage (macrophage infiltration, intermediate filament disruption, z-line disruption, and creatine kinase activity) (p=<0.05). Repeated electrical stimulated isometric muscle contractions induced sarcomere-level damage, evidenced by z-line disruption and increased creatine kinase activity (P<0.05).
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