Table 2.

Effect of age on fiber-type composition in equine skeletal muscle

Horse Breed	Age	Muscle	Methodology	Effect of Age	Ref. No.
SB	2 mo to 28 yr	Gm, Tb	Histochemistry	Gm: type I, IIA ↑, type IIB ↓; Tb: type I ↔, type IIA ↑, type IIB ↓	20
AL, A	2–3 yr vs. 10–24 yr	Gm	Histochemistry	%type I, IIA ↑; %type IIB ↓	74
SB	4–8 yr vs. 20+ yr	Gm	SDS-PAGE & Coomassie blue staining	%type I, IIA ↓, %type IIX ↑	53
TB, SB, QH, CB	2 yr to 30 yr	S	SDS-PAGE & Coomassie blue staining	%type I ↓, type IIA, IIB ↔	43

Horse breeds are as follows: TB, Thoroughbred; SB, Standardbred; QH, American Quarter Horse; CB, crossbred; AL, Andalusian; A, Arabian. Muscles investigated are as follows: Gm, gluteus medius; Tb, triceps brachii; S, semimembranosus. Arrows indicate increased, decreased, or unchanged percentage of fiber type.