Since hypertrophy of muscle fiber has been found to be a far more reliable index of increased muscular capability than gross anatomical measurements, it stands to reason that intracellular changes both anatomical and biochemical should also be related to increased performance, Edward E. Gordon, MD, told conference participants.
The director of the Division of Physical Medicine and Rehabilitation at Chicago's Michael Reese Hospital found that in rats the functional constituents of muscle may be selectively increased or hypertrophied as an adaptation either to endurance-stimulating or strength-stimulating exercises.
The sarcoplasmic protein rose in the fluid phase of the cell with prolonged, repetitive types of exercise, while strength-provoking, forceful effort developed more contractile protein per unit of muscle fiber.
He said: "We may talk of adaptation of muscle on the one hand toward a sarcoplasmic protein (enzymes) hypertrophy, and on the other, toward a contractile protein (actomyosin) hypertrophy. Prolonged activity requires local