ISSN:0025-7990    

出版商:OVID    

年代:1975

数据来源: OVID

ISSN:0025-7990    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Skeletal muscle can undergo rapid growth in response to a sudden increase in work load. For example, the rat soleus muscle increases in weight by 40% within six days after the tendon of the synergistic gastrocnemius is sectioned. Such growth of the overworked muscle involves an enlargement of muscle fillers and occasional longitudinal splitting. Hypertrophy leads to greater maximal tension development, although decreased contraction time and reduced contractility have also been reported. Unlike normal developmental growth, work-induced hypertrophy can be induced in hypophysectoniized or diabetic animals. This process thus appears independent of growth hormone and insulin as well as testosterone and thyroid hormones. Hypertrophy of the soleus can also be induced in fasting animals, in which there is a generalized muscle wasting. Thus muscular activity takes precedence over endocrine influences on muscle size. The increase in muscle weight reflects an increase in protein, especially sarcoplasmic protein, and results from greater protein synthesis and reduced protein breakdown. Within several hours after operation, the hypertrophying soleus shows more rapid uptake of certain amino acids and synthesis of phosphatidylinositol. By 8 hours, protein synthesis is enhanced. RNA synthesis also increases, and hypertrophy can be prevented with actinomycin D. Nuclear DNA synthesis also increases on the second day after operation and leads to a greater DNA content. The significance of the increased RNA and DNA synthesis is not clear, since most of it occurs in interstitial and satellite cells. The proliferation of the non-muscle cells seems linked to the growth of the muscle fibers; in addition, factors causing muscle atrophy (e.g. denervation) decrease DNA synthesis by such cells. In order to define more precisely the early events in hypertrophy, the effects of contractile activity were studied in rat musclesin vitro.Electrical stimulation enhanced active transport of certain amino acids within an hour, and the magnitude of this effect depended on the amount of contractile activity. Stimulation or passive stretch of the soleus or diaphragm also retarded protein degradation. Presumably these effects, of mechanical activity contribute to the changes occuring during hypertrophyin vivo. However, under the same conditions, or even after more prolonged stimulation, no change in rates of protein synthesis was detected. These findings with passive tensionin vitroare particularly interesting, since passive stretch has been reported to retard atrophy or to induce hypertrophy of denervated musclein vivo.It is suggested that increased tension development (either passive or active) is the critical event in initiating compensatory growth.

ISSN:0025-7990    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The differences in changes in strength, body composition, anthropometric measurements and selected motor performance tasks, between groups trained isotonically and isokinetically were compared. Thirty-six male volunteers were randomly assigned to one of four groups: isotonic; isokinetic low speed contraction; isokinetic high speed contraction; and control. Strength training was conducted three days per week, 40 minutes per day for eight weeks. The results demonstrated a clear superiority of the isokinetic training procedures over the isotonic procedures relative to strength, anthropometric, measures and motor performance tasks. The three training groups exhibited similar changes in body composition. The isokinetic high speed group demonstrated the greatest gains overall. The significance of these results is discussed.

ISSN:0025-7990    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Respiratory and metabolic functions were studied at rest and during exercise in 13 Olympic oarsmen at peak of training at sea level and after one month's residence at 2350 m. At sea level each subject completed two severe five minute treadmill runs at 5 mph on a 20% incline inspiring 21% O2for one run and 16% O2for the other. Two more runs at the same speed and incline were carried out at altitude with F102's of 21% and 28%. Pulmonary function tests were carried out at sea level and altitude and steady state diffusion capacity was determined during rest and exercise while breathing 21% O2. Heart rates were monitored by direct electrocardiography. At altitude significant increases were found in MVV (10%), FEV1(6%), MMEF (15%) and PF (9%) hut not in VC. A rise of the DLCOduring exercise from 64.8 to 75.4 ml/min/mm Hg was largely the result of increased ventilation. The response to acute hypoxia (16% O2) and to chronic hypoxia were as follows: VE from 113 to 135/122 1/min; VE/O2from 2.55 to 3.14/3.08 1/100ml; and Petco2 from 40 to 36/34 min Hg. The effect of chronic hypoxia could be abolished by acute normoxia (28% O2) within five minutes; Ve: returned to 99 l/min, Ve/VO2to 2.46 1/100 ml, and PETCO2to 40 mm Hg. VO2for the standard exercise (5 mph − 20% grade) for normoxic and acute hypoxic conditions were similar; 4421 and 4301 ml/min, but this variable decreased significantly upon chronic altitude exposure; 3966 ml/min. This decrement in Vo2was attributed in part to a lower work of breathing.

ISSN:0025-7990    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The significance of isometric muscle strength for rowing performance was studied. The questions investigated were: A) Is the isometric rowing strength (IRS) of oarsmen which is two to three times the dynamic force applied on the oar at maximal power rowing, a ratio which is equivalent to the maximal efficiency of Hill's force/velocity relationship? B) Is IRS higher among successful oarsmen than among those less so? C) Is isometric strength of individual muscle groups correlated to IRS? From measurements on 40 oarsmen the results showed: a) IRS among the most successful oarsmen was 2.6 times the dynamic force indicated in literature; b) IRS was 21 kp higher in the 7 international competitive oarsmen than in 22 national oarsmen, and 42 kp higher than IRS of 11 club oarsmen; and c) of eight other strength determinations only hand grip strength was correlated to IRS. It is suggested that IRS, but not isometric strength of individual muscle groups limits rowing performance.

ISSN:0025-7990    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The use of androgenic-anabolic steroids in the therapeutic dose range by strength athletes is well documented. The benign side effects of these drugs are well known but more disturbing are the increasingly frequent reports of potentially fatal diseases in association with the therapeutic use of these agents. A review is made of the clinical evidence indicating a direct association between androgenic steroids and peliosis hepatis, heptocellular carcinoma and acute myelogenous leukemia, all potentially fatal disorders.

ISSN:0025-7990    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The effect of anabolic steriod treatment on maximum oxygen intake, mile run time, skin fold thickness, body weight, and elbow flexion and knee extension strength was studied. Twenty-one male college students, ages 19–33, engaged in an interval running program six days a week over a three week period. Each subject supplemented their diets with one half gram/kilogram of body weight of 90% protein powder. A double blind design was used for the administration of the steroid treatment with each of the subjects in the treatment group receiving six mg of stanozolol per day. Pre and post treatment tests were administered for each of the dependent variables. There was improvement at the .05 level in the oxygen uptake of both treatment and control groups. For the other dependent variables, the differences between pre-treatment and post-treatment values were not statistically significant. Differences between the steroid and the control groups were not statistically significant for any of the dependent variables. When young male adults are engaged in an endurance training program, steroid treatment does not appear to have any effect on the development of endurance or strength, or on the percent of body fat.

ISSN:0025-7990    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

The validity of the gamma mass scanner in predicting center of mass and moment of inertia of biological tissue was tested using legs of lamb. The reaction board, immersion and pendulum methods were used to obtain one or both the center of mass and moment of inertia of the legs. The results from these methods were compared with those obtained from the scanner. Results indicated that the gamma mass scanner consistently predicted the mass of the legs to within a 1% error, the center of gravity within 2.1% and moment of inertia to within 4.8%. Within the limits of this investigation it was concluded that the gamma mass scanner shows promise as a valid and exact method for determining the center of gravity and moment of inertia of biological tissue.

ISSN:0025-7990    

出版商:OVID    

年代:1975

数据来源: OVID

摘要:

Comparing results of various training studies is often confounded by use of different indices of exercise intensity. Two frequently used indices are: 1) the % HR max method (exercise at a HR corresponding to a chosen percentage of maximal HR), and 2) the Karvonen method (KM) which corrects the % HR max method for resting HR. In this study, % net VO2max was employed as the criterion measure of exercise intensity and a comparison was made between the prediction of % net Vo2max by the above two methods. Experiments were performed on nine males (M ± SD age = 23.7 ± 2.6 yrs) and consisted of double determinations of resting VO2and multiple measurements of resting HR under five different conditions. Duplicate determinations of maximal VO2and HR preceded a third treadmill test consisting of four, 5-minute workloads representing approx 25,45, 65, and 85% net VO2max. The results demonstrated that the KM's prediction of exercise intensity was not significantly different (P> 0.05) from measured intensity at any of the four workloads. Additionally, the % HR max procedure yielded large, significant overpredictions of exercise intensity (29, 22, 16, and 8% overpredictions for the four submaximal intensities, respectively). These results suggest that the KM yields a training HR that reflects exercise intensity within reasonable limits of accuracy.

ISSN:0025-7990    

出版商:OVID    

年代:1975

数据来源: OVID