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Biomedical subjects

G Grimby

Publications and source records attributed to G Grimby.

At least 19 recordsLinked to original sources
PubMed1992

Compensatory muscle fiber hypertrophy in elderly men.

Muscle strength and muscle morphology have been studied three times during a period of 11 yr in nine elderly men. On the last occasion the average age was 80.4 (range 79-82) yr. Body cell mass decreased by 6% and muscle strength for knee extension, measured by means of isometric and concentric isokinetic (30-60 degrees/s) recordings, declined by 25-35% over the 11-yr period. Between 76 and 80 yr of age only the isokinetic strength for 30 degrees/s decreased significantly. Muscle fiber composition in the vastus lateralis did not change between 69 and 76 yr of age, but there was a significant reduction in the proportion of type IIb fibers from 76 to 80 yr. The decrease in type II fiber areas was not significant between 69 and 76 yr of age (as in a larger sample from the same population), but a significant increase in both type I and type II fiber areas was recorded from 76 to 80 yr of age and biceps brachii showed similar tendencies. In the same period, the enzymatic activities of myokinase and lactate dehydrogenase subsided in the vastus lateralis, but there was no change for triose phosphate dehydrogenase, 3-hydroxy-CoA-dehydrogenase, and citrate synthase. The muscle fiber hypertrophy in this group of elderly men with maintained physical activity between 76 and 80 yr of age is interpreted as a compensatory adaptation for the loss of motor units. In addition, the adaptation with respect to oxidative capacities seems to be maintained at this age.

Adaptation, Physiological↗
PubMed1992

Training can improve muscle strength and endurance in 78- to 84-yr-old men.

Nine men, 78-84 yr of age, participated in a dynamometer training program 2-3 times/wk, totaling 25 sessions, using voluntary maximal isometric, concentric, and eccentric right knee-extension actions (30 and 180 degrees/s). Measurements of muscle strength with a Kin-Com dynamometer and simultaneous electromyograms (EMG) were performed of both sides before and after the training period. Muscle biopsies were taken from the right vastus lateralis muscle. The total quadriceps cross-sectional area was measured with computerized tomography. Training led to an increase in maximal torque for concentric (10% at 30 degrees/s) and eccentric (13-19%) actions in the trained leg. The EMG activity increased at maximal eccentric activities. The total cross-sectional quadriceps area of the trained leg increased by 3%, but no changes were recorded in muscle fiber areas in these subjects, who already had large mean fiber areas (5.15 microns 2 x 10(3)). The fatigue index measured from 50 consecutive concentric contractions at 180 degrees/s decreased and the citrate synthase activity increased in all but one subject. The results demonstrate that increased neural activation accompanies an increase in muscle strength at least during eccentric action in already rather active elderly men and that muscle endurance may also be improved with training.

Aged↗
PubMed1979

Perception of effort in isometric and dynamic muscular contraction.

The perception of muscular effort was studied using estimation and production methods in the adductor pollicis and quadriceps. A psychometric scale (percentage magnitude) was used. Static contractions were studied in the adductor pollicis, and both dynamic (isokinetic) and static contractions were studied in quadriceps. Linear and logarithmic equations were fitted for the perceived effort as a percentage of the maximum in relation to the produced percentage maximal force or torque. The logarithmic exponent was around or above 1.0. No significant difference was found between mean exponent and intercept values for the adductor pollicis and the quadriceps, or when estimated or produced values for the two muscles were compared. There was no difference in the same subjects between the equations for static and dynamic contractions with low angular velocity of the quadriceps.

Adult↗
PubMed1979

The effect of unilateral isokinetic strength training on local adipose and muscle tissue morphology, thickness, and enzymes.

One-leg exercise of 5 weeks duration in 10 healthy middleaged women resulted in a significant increment of muscle force in the exercising leg and in a less, but at some angular velocities also significant, increase in the nonexercising leg. The thickness of subcutaneous tissue measured by ultrasound and skinfold caliper decreased, while muscle thickness increased in the exercising leg only. The increased thickness of muscle tissue was associated with an increase in the relative number and relative fiber area of type II fibers in the exercising leg. The mean fiber area of type IIB fibers increased significantly as well as the activity of lactate dehydrogenase and myokinase. The decrease of thickness of subcutaneous adipose tissue was not associated with a significant decrease in fat cell size and was probably due to geometrical factors secondary to hypertrophy of the underlying muscle. It is concluded that the relationship between lean and fat components of the human thigh is significantly influenced by changes in the activity of the thigh skeletal muscles, but a local dynamic strength training program can hardly be used for local emptying of the fat depot over the exercising muscles.

Adenosine Triphosphatases↗
PubMed1979

Muscle strength and speed of movement in relation to age and muscle morphology.

Maximum values for isometric strength, dynamic strength, and speed of movement (MEV) in the quadriceps muscle were measured in 114 male subjects who were between 11 and 70 yr. Biopsy samples were taken from the quadriceps muscle in 51 of the subjects (22-65 yr. old). Isometric and dynamic strength increased up to the third decade, remained almost constant to the fifth decade, and then decreased with increasing age. However, no measurable external atrophy of the quadriceps muscle, explaining the decline in strength, could be seen in old age. Histochemical changes in the muscle tissue such as decreased proportion of type II fibers and a selective atrophy of type II fibers, were seen with increasing age. The strength decline in old age was also observed to correlate significantly with the type II fiber area. Multiple regression analyses indicated, however, that mechanisms other than the type II fiber atrophy might be responsible for the decline in strength performance during aging. The implications of these findings are discussed.

Adolescent↗
PubMed1978

Maximal work performance test in middle-aged women: results from a population study.

Based on sampling from official census lists a sample of middle-aged women was obtained in five different age strata; 38, 46, 50, 54 and 60 years. Based on date of birth a sub-set was sampled for maximal exercise testing. The participation rate was 81% and 194 women underwent the test. In sixteen women the test was interrupted due to poor cooperation or clinical contra-indications against continued loading. 54% of the women considered the maximal load to be at least very straining according to a standardized scale for perceived exertion. The average maximal load decreased from 113 to 98 W with advancing age. In the highest age group only 16% exceeded 130 W compared to 43% in the youngest group. Maximum heart rate decreased with age but maximum respiratory frequency and perceived exertion did not. Systolic blood pressure 2 min after maximal work increased with age. Minnesota Code items 4:1-3 and 5:1-3 were demonstrated in 30% of the women, mainly in the older age strata. Other ECG-abnormalities were uncommon. Despite the widely differing incidence of myocardial infarction these ischaemic ECG-abnormalities were as common in women as in a comparative sample of men. This observation questions the traditional interpretation of the exercise induced ECG response in women.

Adult↗
PubMed1977

Work capacity in women in relation to age as judged from a maximal work performance test.

Work performance test could be carried out on a population sample of women aged 38-60 years without complications. The work capacity decreased with increasing age and at the same time the maximal heart rate during work decreased with increasing age. Blood pressure increased with age and these differences between the various ages were about the same as at rest. Respiratory frequency and perceived exertion on maximal work were similar in the ages studied. ECG changes were common and were found to be as common as in men who had been studied with the same technique and in the same ages. As ECG changes were very common and as myocardial infraction is very seldom in women of these ages, ECG changes during and after work did not seem to be a good discriminator of women subjected to myocardial infraction.

Adult↗