Human Skeletal Muscle Phosphorylase Activities with Exercise and Training

1972 ◽  
Vol 50 (11) ◽  
pp. 1038-1042 ◽  
Author(s):  
A. W. Taylor ◽  
M. A. Booth ◽  
S. Rao
Keyword(s):  
Skeletal Muscle ◽  
Work Load ◽  
Bicycle Ergometer ◽  
Healthy Male ◽  
Maximal Aerobic Capacity ◽  
Work Time ◽  
Muscle Phosphorylase ◽  
Male Subjects ◽  
Exercise And Training ◽  
And Training

Fifteen healthy male subjects classified as sedentary (7) or active (8), exercised to exhaustion on a bicycle ergometer at a work load requiring 70% of their maximal aerobic capacity. Biopsy samples of the vastus lateral is muscle were taken at rest, at the time of fatigue, and after a 10 min recovery. Training increased [Formula: see text], [Formula: see text], work time to fatigue, skeletal muscle glycogen levels, and phosphorylase a activity (P < 0.01). An exhaustive submaximal exercise reduced the glycogen levels of the trained group to values similar to the fatigue levels of the nontrained subjects: the higher the initial glycogen levels, the longer the subjects were able to exercise before the onset of fatigue. Skeletal muscle phosphorylase a activities decreased with exercise to fatigue in all groups whereas phosphorylase b activities were maintained. Training had no effect on resting phosphorylase b activity.

Muscle morphology heterogeneity: control, significance for performance and responses to training

2004 ◽  
Vol 32 ◽  
pp. 11-25
Author(s):  
J L L Rivero
Keyword(s):  
Skeletal Muscle ◽  
Muscle Blood Flow ◽  
Adaptive Plasticity ◽  
Muscle Fibres ◽  
The Past ◽  
Skeletal Musculature ◽  
Skeletal Muscle Fibres ◽  
Exercise And Training ◽  
And Training ◽  
Total Muscle

The skeletal musculature of the horse is highly developed and adapted to match the animal's athletic potential. More than half of a mature horse's body weight comprises skeletal muscle and the total muscle blood flow during maximal exercise represents 78% of total cardiac output. Exercise requires the co–ordinated application of many different body systems under the control of the nervous systems. Metabolites and oxygen reach skeletal muscle fibres via the respiratory, cardiovascular and haematological systems. The muscle fibres produce energy in the form of ATP that, via the contractile machinery, is converted into mechanical work. The structural arrangements of the musculoskeletal system provides the means with which to harness this energy to move the horse's limbs in a characteristic rhythmical pattern that is well established for each gait.Equine skeletal muscle is considerably heterogeneous and this diversity reflects functional specialisation and is the basis of its adaptive plasticity. Cellular and molecular diversity of equine muscle and the response of this tissue to exercise and training have been studied extensively over the past 30 years.

Fibrinolytic and hemostatic changes during and after maximal exercise in males

1976 ◽  
Vol 40 (3) ◽  
pp. 287-292 ◽  
Author(s):  
G. L. Davis ◽  
C. F. Abildgaard ◽  
E. M. Bernauer ◽  
M. Britton
Keyword(s):  
Heart Rate ◽  
Factor Viii ◽  
Fibrinolytic Activity ◽  
Work Load ◽  
Bicycle Ergometer ◽  
Maximal Heart Rate ◽  
Relative Level ◽  
Maximum Exercise ◽  
Activity Factor ◽  
Male Subjects

To evaluate changes in fibrinolytic activity, factor VIII and other hematological variables during and after a progressive step increment in work load, 10 healthy male subjects (22–27 yr of age) were exercised to exhaustion on an electromagnetic bicycle ergometer. Blood samples were drawn serially throughout the experiment. Little change in fibrinolytic activity was observed before 70–80% maximum heart rate (MHR) was achieved. Major changes occurred after 80% MHR. Peak values coincided with maximum exercise. In contrast major changes in factor VIII were observed between 95 and 100% MHR with peak values occurring 5–10 min postexercise. An increase in white blood cell count, platelet count, and retention was observed at maximum exercise. One individual failed to demonstrate an increase in either fibrinolytic or factor VIII activity. Relating the data to either the percent maximal oxygen uptake or percent maximal heart rate demonstrates the importance of the exercise protocol and exerting all subjects to the same relative level of physiological work.

Maximal heart rate during work in older men

1959 ◽  
Vol 14 (4) ◽  
pp. 562-566 ◽  
Author(s):  
Irma Åstrand ◽  
Per-Olof Åstrand ◽  
Kaare Rodahl
Keyword(s):  
Heart Rate ◽  
Ambient Air ◽  
Work Load ◽  
Work Capacity ◽  
Bicycle Ergometer ◽  
Maximal Heart Rate ◽  
Average Maximum ◽  
Work Up ◽  
Aerobic Work Capacity ◽  
Male Subjects

Nine 56–68-year-old male subjects performed muscular work up to maximal loads on a bicycle ergometer while breathing both ambient air and oxygen. Heart rate increased to an average maximum of 163/min. The maximal O2 intake averaged 2.24 l/min. and the blood lactic acid concentration 85 mg/100 ml. In no case was the maximal heart rate higher when breathing O2 than when breathing air. This low maximal heart rate in older people probably limits the capacity for O2 intake. Four subjects were able to work for about 1 hour without any sign of exhaustion on a work load requiring an O2 consumption of about 50% of their maximal aerobic work capacity. Submitted on October 3, 1958

Effect of exercise on epinephrine turnover in trained and untrained male subjects

1985 ◽  
Vol 59 (4) ◽  
pp. 1061-1067 ◽  
Author(s):  
M. Kjaer ◽  
N. J. Christensen ◽  
B. Sonne ◽  
E. A. Richter ◽  
H. Galbo
Keyword(s):  
Work Load ◽  
Hot Water ◽  
Plasma Epinephrine ◽  
Work Intensity ◽  
O2 Uptake ◽  
Vo2 Max ◽  
Work Time ◽  
Arterial Blood ◽  
Male Subjects ◽  
Secretory Capacity

The kinetics underlying plasma epinephrine concentrations were studied. Six athletes (T) and six sedentary males (C) were given intravenous infusions of 3H-labeled epinephrine, after which arterial blood was drawn. They rested sitting and bicycled continuously to exhaustion (60 min at 125 W, 60 min at 160 W, 40 min at 200 W, and 240 W to the end). Work time was 154 +/- 13 (SE) (T) and 75 +/- 6 (C) min. At rest, epinephrine clearance was identical [28.4 +/- 1.3 (T) vs. 29.2 +/- 1.8 (C) ml . kg-1 . min-1], but plasma concentration [1.42 +/- 0.27 (T) vs. 0.71 +/- 0.16 (C) nmol . l-1] and, accordingly, secretion [2.9 +/- 0.7 vs. 1.5 +/- 0.4 nmol . min-1] were higher (P less than 0.05) in T than C subjects. Epinephrine clearance was closely related to relative work load, decreasing from 15% above the basal level at 30% of maximal O2 uptake (VO2 max) to 22% below at 76% of VO2 max. Epinephrine concentrations increased much more with work intensity than could be accounted for by changes in clearance and were, at exhaustion, higher (P less than 0.05) in T (7.2 +/- 1.6) than in C (2.5 +/- 0.7 nmol . l-1) subjects despite similar glucose, heart rate, and hematocrit values. At a given load, epinephrine clearance rapidly became constant, whereas concentration increased continuously. Forearm extraction of epinephrine invalidated use of blood from a cubital vein or a hand vein arterialized by hot water in turnover measurements. During exercise, changes in epinephrine concentrations reflect changes in secretion rather than in clearance. Training may increase adrenal medullary secretory capacity.

Metabolic, cardiovascular, and respiratory factors in the development of fatigue in lifting tasks

1978 ◽  
Vol 45 (1) ◽  
pp. 64-68 ◽  
Author(s):  
J. S. Petrofsky ◽  
A. R. Lind
Keyword(s):  
Oxygen Uptake ◽  
Maximal Oxygen Uptake ◽  
Work Load ◽  
Specific Weight ◽  
Bicycle Ergometer ◽  
Isometric Contractions ◽  
Bicycle Ergometry ◽  
Physiological Capacity ◽  
Male Subjects ◽  
Extended Work

Three well-trained male subjects served as volunteers in these experiments to examine the physiological capacity for extended work during lifting tasks. The maximal oxygen uptake (VO2max) during lifting was always lower than work on the bicycle ergometer. However, the work load during lifting which could be maintained for 1--4 h was 50% of the VO2max for lifting each specific weight of box; the limit for lifting light boxes without fatigue was at an oxygen uptake of about 25% of the VO2max obtained from bicycle ergometry. Significant fatigue in the forearm muscles was found during prolonged lifting as assessed from the endurance of isometric contractions and from the surface electromyogram (EMG), and was more pronounced as the weight of the box increased.

Human Skeletal Muscle Glycogen Synthetase Activities with Exercise and Training

1972 ◽  
Vol 50 (5) ◽  
pp. 411-415 ◽  
Author(s):  
A. W. Taylor ◽  
R. Thayer ◽  
S. Rao
Keyword(s):  
Skeletal Muscle ◽  
Muscle Glycogen ◽  
Human Skeletal Muscle ◽  
Human Subjects ◽  
Fitness Level ◽  
Glycogen Synthetase ◽  
Skeletal Muscle Glycogen ◽  
Level Of Activity ◽  
Exercise And Training ◽  
And Training

A 5 month training program increased skeletal muscle glycogen synthetase activities of both the 'I' and 'D' forms in human subjects. The level of activity of the enzyme appears to be directly related to the physical fitness level of the subjects tested.

Cardiorespiratory responses during prolonged exercise

1961 ◽  
Vol 16 (6) ◽  
pp. 997-1000 ◽  
Author(s):  
Ernest D. Michael ◽  
Kenneth E. Hutton ◽  
Steven M. Horvath
Keyword(s):  
Heart Rate ◽  
Oxygen Uptake ◽  
Energy Cost ◽  
Prolonged Exercise ◽  
Bicycle Ergometer ◽  
Maximum Oxygen Uptake ◽  
Healthy Male ◽  
Heart Rates ◽  
Cardiorespiratory Responses ◽  
Male Subjects

Three healthy male subjects 20 years of age were exercised for 2—8 hr riding a bicycle ergometer or walking on a treadmill. Higher heart rates were found with the bicycle rides than with the walking exercises with equivalent oxygen uptakes. The subjects could not work on the bicycle ergometer at oxygen uptakes of 1.8 liters/min for more than 4 hr but could with this uptake walk 8 hr. The results indicated that an 8-hr period of exercise could be completed without undue fatigue whenever the energy cost did not exceed 35% of the maximum oxygen uptake where heart rates, oxygen uptakes, and rectal temperatures remained below 120 beats/min, 1.4 liters/min, and 38 C, respectively. The heart rate appeared to be the important factor for estimating 8-hr work endurance. A rate of 140 beats/min could not be maintained for more than 4 hr or a rate of 160 beats/min for more than 2 hr without extreme fatigue. Submitted on October 26, 1960

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