Paper sheds light on conditioning/deconditioning
In a quest to break my plateau, I’ve been searching the web for insight and found this article.
The article deals with tendons and ligaments and their responses to exercise, immobilization, and remobilization. This is relevant to us because
1) we want to stretch our ligaments and tunica;
2) gains often slow because our tissues are thought to become “overconditioned;” and
3) many have proposed taking “deconditioning breaks” to allow tissues to weaken before PE is resumed.
Be sure to take a good look at Fig. 5. The figure shows how a ligament’s strength decreases with time after immobilization, and then recovers once exercise is resumed.
Strength appears to decrease to nearly 1/5 its initial value after only 3 months of immobilization. However, full strength is restored after only 2 months of remobilization.
This suggests that deconditioning periods of a couple of months should significantly reduce tissue strength, and that there is a fairly narrow window of time during which the tissues remain weakened after PE is resumed.
Here are some good nuggets from the article:
In mature animals, immobilization causes a drastic decrease in the loading, and consequently the strain stimulus, experienced by a tendon or ligament. The reduced strain stimulus leads to a rapid loss of cross-sectional area, modulus, and strength. When loading is restored through remobilization, the strain stimulus is elevated and the properties rapidly recover as the immobilization effects are reversed. Exercise can also increase the strain stimulus, leading to increases in the geometric and material properties. Similar changes occur in immature animals, and the difference between immature and mature animals can be attributed to baseline biological growth that occurs independently from mechanical loading. Strains are therefore a likely stimulus for controlling tendon and ligament adaptation both before and after maturity.
The mechanical properties of tendons and ligaments are determined by microstructural parameters including collagen fiber content, fiber orientations, and cross-link density (35). Fibroblasts change these parameters through altered biosynthetic activity stimulated by mechanical loading. Cyclic tensile strains stimulate an up-regulation of type I collagen production (36) and alignment of the collagen fibers in directions of principle tensile strain (37, 38). Removal of loading leads to degradation of the extra-cellular matrix (39) and disruption of collagen fiber alignment (22) and cross-linking (18).
In mature animals, immobilization does not lead to changes in the weight or collagen content of tendons and ligaments (15,17,19,20) despite increased collagen turnover (18,20,21). Cross-sectional area may decrease (21), as do modulus, strength, and stiffness (16,19,20). With remobilization, tendons and ligaments recover their structural and material properties (21,22).
Exercise leads to a moderate increase in the stiffness and failure force. Immobilization leads to a significant decrease in these properties, which rapidly return to normal with remobilization.
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