C. A. Prietto

Skeletal muscle rofiles amon elite long, middle, and short distance swimmers

Skeletal muscle profiles of fiber composition and leg power and strength were obtained in 30 national caliber swimmers (20 males, 10 females). Subjects were clas sified into three groups based upon the distance of their primary events [long distance (LDS), middle dis tance (MDS), and short distance (SDS) swimmers]. Intergroup analyses showed that the LDS group had the highest values of percent Type I muscle fiber com position (percent Type I and percent Type I area), and the lowest values of leg power and strength values (vertical jump and torque-velocity relationships). In ad dition, when grouped by Type I fiber composition, sub jects having ≥50% Type I tibers had significantly lower vertical jump and torque values than those having <50% Type I fibers. Overall, the compositional and functional measurements were consistent with the spe cific metabolic and contractile demands of the different swim groups.

Alterations in the in vivo torque-velocity relationship after Achilles tendon rupture. Further evidence of speed-specific impairment.

The torque-velocity relationship of the ankle plantar flexors was determined in 31 patients recovering from Achilles tendon rupture. Isokinetic torque measurements were made at speeds of 0 to 240 degrees.s-1 at 24 degrees.s-1 intervals. Measurements of instantaneous torque were made at joint angles corresponding to neutral and 10 degrees plantar flexion. In 17 patients treated surgically, there was little difference between the injured and the uninjured leg. In contrast, patients who were treated by casting exhibited major differences between the injured and uninjured legs. This difference became amplified when torque values at 10 degrees plantar flexion were compared. Additionally, the differences between the injured and uninjured legs were not uniform. The differences in torque were greatest at slow test speeds and least at fast test speeds. Comparisons of the injured surgical and injured nonsurgical legs demonstrated that the surgical group had significantly greater torque. This difference was also speed specific. These findings demonstrate that both groups exhibited speed-specific impairment with the loss of muscle strength being greatest at slow speeds. Also, the degree of impairment was dependent on the ankle position at which torque was measured. Surgical treatment provides better functional results as observed by the torque-velocity relationship.

Skeletal muscle profiles in elite springboard and platform divers

This investigation determined the vastus lateralis mus cle fiber composition, as well as leg power and strength, in a group of 10 world class divers. Male divers had a low mean percentage of Type I fibers (36%), which was consistent with the functional demands of their sport, whereas females had a mean value of 61 %. The ratio of Type I/Type II cross-sectional fiber area was 0.95 in females and 0.82 in males. Angle-specific torque-veloc ity relationships, derived from Cybex testing of the knee extensors, revealed high torque values in males but not in females. The observed male-female differences have no clear explanation, unless muscle fiber composition has greater importance in the more difficult dives exe cuted by men.

Histochemical properties of muscle allografts enhanced via cyclosporine.

Until recently, the transplantation of skeletal muscle across a major histocompatibility barrier has proved difficult. However, with the advent of cyclosporine (CsA), it has become possible to achieve extended survival across such histocompatibility barriers. To date, very little is known about the histochemical, biochemical, immunological or contractile properties of long-term-surviving muscle allografts. Consequently, it was the focus of this study to histochemically examine muscle allografts prolonged with CsA and determine the cross-sectional area of fast glycolytic muscle fibers. Measurements of cross-sectional area were made because they are an important correlate to the amount of tension a muscle can generate. Animals were assigned randomly to one of three groups: control (normal) (n = 5), syngeneic (n = 4), and allogeneic (n = 4). Muscle allografts were performed by transplanting the gastrocnemius of an ACI rat (RT1a) hindlimb into the hindlimb of a Lewis rat (LEW;RT1(1]. The syngeneic model consisted of an ACI-to-ACI transplant. Animals in the allograft group were given CsA (8 mg/kg/day) until the time of sacrifice. At approximately 100 days following transplantation, both syngeneic and allogeneic muscles were removed from the recipient, and quickly frozen in isopentane cooled by liquid nitrogen. Muscle fibers were classified as slow-oxidative (SO), fast-oxidative-glycolytic (FOG), or fast-glycolytic (FG) based upon their staining for myofibrillar ATPase and NADH-dehydrogenase. From each muscle, the cross-sectional area of approximately 175 FG muscle fibers was determined. The fast-glycolytic muscle fibers of both the syngeneic and allogeneic grafts demonstrated a substantial decrease in cross-sectional area. The mean value (+/- SD) for the fibers of the allografted muscle was 1165 +/- 533 microns 2. The mean (+/- SD) fiber cross-sectional area for the fibers of the syngeneic muscle was 973 +/- 421 microns 2. These values contrast with a mean (+/- SD) value of 3552 +/- 601 microns 2 for fibers from age-matched control animals. The differences between the syngeneic and allogeneic muscles were not significant (P greater than 0.05). However, both exhibited significant (P less than 0.01) atrophy compared with the control muscle.