Thigh Volume Research Articles

Relationship between muscle QO2 and fatigue during repeated isokinetic contractions.

The percent slow-twitch fibers (%ST) of the vastus lateralis muscle and selected indicators of maximum aerobic power (QO2, VO2 max, and leg extensor VO2 max) were compared with the rate of fatigue development during 45 s of repeated maximum isokinetic leg extension-flexion contractions (180 degrees/s) on 13 males. Subjects with muscle respiratory capacities (QO2) above the mean (2,472 microliter O2 X h-1 X g-1) displayed a significantly slower rate of fatigue development than those subjects with QO2 values below the mean. In addition, indicators of maximum aerobic power were correlated with the percent of maximum power and power/ml fat-free thigh volume at 5, 15, 30, and 45 s during the fatigue test. The correlations increased progressively during the fatigue test and became significant at 45 s. This trend was not observed when the %ST fibers were compared with the percent of maximum power and power/ml fat-free thigh volume at these time intervals. These data suggest that 1) the muscle tissue's capacity for aerobic metabolism influences the rate of fatigue development even during a strenuous short-term isokinetic exercise task, and 2) factors other than fiber type may interact to confound the prediction of fiber type by noninvasive means.

Isokinetic contractile properties of the quadriceps with relation to fiber type.

Fifteen subjects were assigned to three groups on the basis of the proportion of fast-twitch fibers (% FT) in their vastus lateralis muscles. Torque production per unit of fat free thigh volume was then determined during knee extension on an isokinetic dynamometer at 60, 120, 180, 240, and 300 degrees . s-1. Maximal isometric force was also obtained at 65 degrees from horizontal. Subjects with predominantly fast twitch muscle fibers demonstrated significantly greater peak power, rate of power production and work than subjects with predominantly slow twitch fibers at all but the lowest velocity of 60 degrees . s-1. Mean peak power for all subjects occurred at approximately 30% of maximal knee extension velocity (210 degrees x s-1) and 34% of maximal voluntary isometric contraction. When work, peak power and rate of power production were correlated with % FT fibers, then the highest correlations of 0.69, 0.57, and 0.73 respectively, all occurred at 180 degrees . s-1. These observations suggest that: 1) the torque-velocity, power-velocity relationship of the quadriceps is similar to the force-velocity, power-velocity relation found for excised muscle, 2) when using the knee extension exercise for the prediction of muscle fiber composition of the quadriceps the most appropriate speed for testing appears to be 80 degrees . s-1.

Measurement of quadriceps muscle wasting by ultrasonography.

Grey-scale ultrasonography can produce an image of the quadriceps muscle from which it is possible to measure its cross-sectional area (CSA). The between-days coefficient of variation for quadriceps CSA (at mid-thigh) in 14 legs of seven subjects each scanned on four days was reduced to 4.0% by averaging four scans on each day. Bilateral scans (at the mid-thigh level) were used to measure the severity of quadriceps wasting in 21 otherwise healthy adult patients with a difference in thigh circumference following unilateral knee immobilization or injury. Quadriceps wasting as demonstrated by the scans was consistently more severe than the disparity in whole thigh cross-sectional area at the same level or the disparity in anthropometric estimates of fat-free thigh volume. Investigations concerned with changes in quadriceps muscle bulk must therefore use a technique (such as ultrasonography) which allows measurement of the quadriceps itself.

Factors relating to the strength of male adolescents.

Factors relating to the strength of 53 postpubertal adolescent males have been examined. A strength index, composed of left and right handgrip and back strengths, was related to the following: anthropometric measurements and their derivatives; level of habitual activity; body shape as characterized by Heath-Carter and Sheldonian somatotype ratings; and anthropometric ratios. Strength was found to be positively related to all anthropometric measurements with the exception of skinfold thicknesses. When body weight was held constant, strength was positively related to arm circumference, bicondylar diameters of the humerus and femur, thigh volume, and biacromial diameter, and negatively related to percentage of fat. Strength was not related to the level of habitual activity. The relative contributions of overall body size and body shape to predictions of strength are approximately 57 and 47%. Measures of overall size appear to make no independent contribution to strength, beyond that contributed by limb segment volumes, or a combination of linear limb dimensions and measures of body shape.