Abstract
Contraction-induced injury occurs when a muscle is stretched while activated (lengthening contraction). Exposure to a bout of lengthening contractions results in protection from subsequent lengthening contraction-induced injury as well as an elevation in phosphorylated Akt and p70S6K. Whether Akt or p70S6K is involved in the protection from contraction-induced injury is unclear. To test for a specific role of Akt and/or p70S6K to induce protective adaptations, we used a conditioning protocol of passive stretches that reduces contraction-induced injury with minimal involvement of other cellular responses that have been associated with the Akt signaling pathway, such as increased metabolism, cell growth, and cell death. Purpose: To determine whether activation of Akt or p70S6K is necessary to induce protective adaptations. Methods: Extensor digitorum longus muscles of anesthetized mice were administered 75 lengthening contractions in situ with or without previous exposure to 75 passive stretches 1 h, 24 h, 3 d, or 14 d prior to lengthening contractions. Results: Compared with unconditioned muscles, the deficit in isometric force and number of injured fibers 3 d following lengthening contractions were smaller by half for passive-stretch-conditioned muscles from all time points. Phosphorylation of Akt and p70S6K were analyzed by Western blot 0 or 3 h following either lengthening contractions or passive stretches. Whereas lengthening contractions increased phosphorylation of Akt at 0 h and p70S6K at 3 h, passive stretches did not at any time increase phosphorylation of Akt or p70S6K despite reducing contraction-induced injury. Conclusion: Activation of neither Akt nor p70S6K is necessary to induce adaptations that reduce the severity of contraction-induced injury.
Original language | English (US) |
---|---|
Pages (from-to) | 1058-1064 |
Number of pages | 7 |
Journal | Medicine and Science in Sports and Exercise |
Volume | 38 |
Issue number | 6 |
DOIs | |
State | Published - Jun 2006 |
Externally published | Yes |
Keywords
- Adaptation
- Conditioning
- Damage
- Passive stretching
ASJC Scopus subject areas
- Public Health, Environmental and Occupational Health
- Physical Therapy, Sports Therapy and Rehabilitation
- Orthopedics and Sports Medicine