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Biomedical subjects

A L Dickinson

Publications and source records attributed to A L Dickinson.

9 recordsLinked to original sources
PubMed1998

Sample size required for the accurate determination of fiber area and capillarity of human skeletal muscle.

This study aimed to determine the skeletal muscle fiber sample size required for a reliable, valid representation of an individual's average fiber area and capillary contacts (CC) per fiber. Biopsies were obtained from the biceps brachii of 11 college-age, recreational resistance-trained men in conjunction with a study investigating how muscle morphology changed after 12 weeks of resistance training. The effect of additional measurements on the rolling cumulative means for fiber area and CC per fiber was evaluated using sequential estimation analysis. Results showed that group cumulative mean and standard deviation had stabilized by 50 fiber measurements per individual for type I and II fibers and CC per fiber. Significant correlations (.96-.99; p < .05) existed between the 50th and 95th/100th cumulative individual means. These results indicate that a typical skeletal muscle needle biopsy would be sufficient to characterize type I and II fiber areas and CC per fiber of an individual in most subject populations, although the required sample size for characterizing fiber subtypes might be different.

Adult↗
PubMed1990

Skeletal muscle fiber area alterations in two opposing modes of resistance-exercise training in the same individual.

The purpose of this study was to observe fiber area changes that might occur in the same subject from two opposing resistance-exercise training regimes isolating the quadriceps muscle group. Twelve college-age men divided into two groups participated in each of two 7.5-week regimens; one performed a muscular strength program (high-resistance, low-repetition) 4 days a week on a resistance-exercise apparatus, while the other performed a muscular endurance (low-resistance, high-repetition) program. After a 5.5-week hiatus, the groups changed regimens for the second 7.5 weeks. Closed-needle biopsies of the dominant vastus lateralis and isokinetic dynamometer evaluations were made before and at the end of each training period. The muscle samples were analyzed for area changes. In both groups the initial exercise stimulus, whether for strength or endurance, increased the area of fibers of all three major types (I, IIA, and IIB). Subjects doing strength exercises as their second treatment showed a further increase in the area of type I and IIB fibers, whereas those doing endurance exercises showed a decrease in all fiber types. From the first to the last biopsy all fiber areas were decreased (P less than 0.05) in the control-strength-endurance group and increased (P less than 0.05) in the control-endurance-strength group. These results suggested that endurance exercise preceding strength exercise in an isolated muscle group maximized fiber area adaptations to exercise stress. Consideration should thus be given in exercise and rehabilitation programs to the muscle cellular adaptations evidenced in different orders of training, particularly if muscular strength is considered important.

Adenosine Triphosphatases↗
PubMed1989

Endurance training for elderly women: moderate vs low intensity.

This investigation evaluated the efficacy of training at moderate-60% Maximal Heart Rate Reserve, HRRmax, (MOD) and low-40% HRRmax (LOW) intensities in a population of older American women (N = 16, mean age = 78.4 years). Prior to and immediately following a 10-week training program consisting of exercising at the prescribed heart-rate intensity with a caloric expenditure of 100 calories, the following measurements were performed: Maximal oxygen consumption (VO2max), Maximal Lactate Production (HLAmax), Maximal Heart Rate (HRmax), Maximal Workstage (WSmax), Total Cholesterol (TOTC), High Density Lipoprotein Cholesterol (HDLC), and Rate Pressure Product Max (RPPmax). Significant differences, p less than .05, were noted pre- to post-training for measures of VO2max, whether expressed in 1.min-1 or ml.kg-1.min-1, and WSmax. No statistical differences existed between the groups pre- or post-training for these measures. The results suggest that the low-intensity exercise prescription provides an adequate training stimulus for older women who have been sedentary and who might be at higher risk for cardiac or musculoskeletal injury, particularly at the initiation of an exercise program.

Aged↗
PubMed1987

Effect of training/detraining on submaximal exercise responses in humans.

Human subjects participated in a training/detraining paradigm which consisted of 7 wk of intense endurance training followed by 3 wk of inactivity. In previously sedentary subjects, training produced a 23.9 +/- 7.2% increase in maximal aerobic power (V02max) (group S). Detraining did not affect group S V02max. In previously trained subjects (group T), the training/detraining paradigm did not affect V02max. In group S, training produced an increase in vastus lateralis muscle citrate synthase (CS) activities (nmol.mg protein-1. min-1) from 67.1 +/- 14.5 to 106.9 +/- 22.0. Detraining produced a decrease in CS activity to 80 +/- 14.6. In group T, pretraining CS activity (139.5 +/- 14.9) did not change in response to training. Detraining, however, produced a decrease in CS activity (121.5 +/- 7.8 to 66.8 +/- 5.9). Group S respiratory exchange ratios obtained during submaximal exercise at 60% V02max (R60) decreased in response to training (1.00 +/- 0.02 to 0.87 +/- 0.02) and increased (0.96 +/- 0.02) after detraining. Group T R60 (0.91 +/- 0.01) was not affected by training but increased (0.89 +/- 0.02 to 0.95 +/- 0.02) after detraining. R60 was correlated to changes in CS activity but was unrelated to changes in V02max. These data support the hypothesis that the mitochondrial content of working skeletal muscle is an important determinant of substrate utilization during submaximal exercise.

Adult↗
PubMed1986

The reproducibility of VO2max, ventilatory, and lactate thresholds in elderly women.

The reproducibility of VO2max, ventilatory, and lactate thresholds in elderly women. Med. Sci. Sports Exerc., Vol. 18, No. 4, pp. 425-430, 1986. This investigation examined the reproducibility of maximal (VO2max) and submaximal measures of fitness for elderly women. Eight subjects [age (yr): mean = 80.6 +/- 3.7; range = 73-86] volunteered to repeat three continuous, incremental maximal effort treadmill tests. Blood lactate determinations were made for each increment from blood samples taken from an indwelling venous catheter located in the back of the hand. Average VO2max values (ml X min-1 X kg X l-1) were 13.21 + 1.95 for test 1, 13.44 +/- 1.83 for test 2, and 13.62 + 2.95 for test 3. In all but one subject, a threshold was not definable by either ventilatory or lactate measurements. Maximal lactate values were low, with the average values for tests 1, 2, and 3 being 1.89, 1.46, and 1.86 mmol X l-1, respectively. The data demonstrates that VO2max is reproducible for older women and can, therefore, be used for fitness assessment and exercise prescription. The use of ventilatory or lactate thresholds as submaximal measures of fitness or as minimal intensities for exercise prescription was determined not to be applicable for women in the eighth and ninth decades of life.

Aged↗
PubMed1982

Effects of wind on the thermal and metabolic responses to exercise in the cold.

The thermal and metabolic responses to exercise were studied in a cold environment with and without a wind. Six men and two women rode a cycle ergometer for 90 min at 55-60% VO2max in a -20 degrees C environment. Subjects were exposed to a 4.1 m . s-1 wind on two of the four exposures. The subjects wore regulation cross-country ski uniforms. An additional vest was worn on 2 d, 1 d with the wind and 1 d without the wind. Total insulation for the ski uniform (Icl+a) was 1.59 clo and 1.77 clo with the vest. Final Tre, Tsk, and Tb were significantly lower, and radiative and convective heat loss, heat loss from body storage, and tissue insulation (It) were significantly greater when exercising in the wind. The addition of the vest increased only Tsk. Both metabolic rate and heart rate increased significantly during exercise, but no significant differences were observed between wind and no-wind conditions. The subjects responded to the increased cooling effect of the wind by increasing It, however, this response was not sufficient to prevent loss of stored heat and Tre from falling. It was concluded that the exercise intensity must be 10 METS or greater to maintain thermal balance when exercising in a -20 degrees C environment with a 4.1 m . s-1 wind if Icl+a = 1.59 clo.

Air Movements↗
PubMed1980

Characteristics of elite male and female ski racers.

Fifty-four members of the U.S. Ski Team who competed in the alpine, cross-country, or Nordic combined events were studied to learn more about the characteristics of elite ski racers in each of the events. Variables examined were percent body fatness, maximal oxygen uptake, maximal ventilation, isometric knee extension strength, power, agility, balance, and response time. In addition, isokinetic knee extension strength and endurance were measured on the alpine skiers. Cross-country skiers had higher Vo2max adjusted for weight or lean body weight than alpine skiers of the same sex. Male skiers had larger VO2max with or without adjustments for weight or lean body weight than female skiers in the same events. Alpine skiers had significantly more isometric knee extension strength (males = 3078 N, females = 2194 N) and power during the Margaria-Kalamen stair run (males = 1791 W, females = 1131 W) than cross-country skiers of the same sex. Differences in isokinetic knee extension strength at slow rates of contraction (30 degrees/s) between male and female alpine skiers were not significant when strength was expressed as strength x kg LBW-1. Male alpine skiers produced more power and had more isokinetic leg strength x kg LBW-1 at high contraction rates (180 degrees/s) than female alpine skiers.

Adipose Tissue↗