Showing papers on "Exercise physiology published in 1978"

Physical exercise and fuel homeostasis in diabetes mellitus.

Abstract: During the initial phase of physical exercise muscle glycogen is the primary source of fuel for contracting muscle in normal man. When exercise continues beyond the first 5–10 min blood glucose and free fatty acids (FFA) become increasingly important substrates. Glucose utilization may account for 25–35% of the total substrate supply during mild to moderately heavy exercise. The augmented glucose utilization by working muscle is balanced by a rise in hepatic glucose production. The latter is achieved primarily by hepatic glycogenolysis during brief work, but during prolonged exercise gluconeogenesis may account for as much as 40–50% of the hepatic glucose output. Muscle uptake of FFA is determined primarily by its availability to the working muscle, and it may account for 30–60% of the total fuel supply. Ketone bodies are not utilized by working muscle in normal man. In patients with diabetes mellitus the metabolic effects of physical exercise are to a large extent determined by the time interval between insulin administration and the onset of exercise. Thus, in insulin treated patients with mild hyperglycaemia and no or minimal ketonaemia the utilization of glycogen, blood glucose and FFA by working muscle is similar to that of healthy subjects, and exercise is accompanied by a fall in blood glucose levels. In contrast, patients with more marked hyperglycaemia and hyperketonaemia may respond to exercise with a further rise in both blood glucose and ketone body levels, reflecting augmented rates of hepatic gluconeogenesis as well as ketogenesis. The repletion of muscle and liver glycogen, which takes place for 24–48 h after exercise, requires — besides carbohydrate feeding — a minimum concentration of insulin. Glycogen resynthesis probably accounts for a major part of the empirically well established beneficial effect of physical exercise in diabetic patients. The above considerations underscore the importance of adequate insulin administration in connection with exercise in diabetic patients.

Synthesis of muscle glycogen during recovery after prolonged severe exercise in diabetic subjects. Effect of insulin deprivation.

Abstract: The effect of insulin deprivation on muscle glycogen resynthesis during 12 h of resting recovery after exhaustive exercise was studied in five young juvenile diabetic subjects. The subjects were gi...

Phosphorylase a in human skeletal muscle during exercise and electrical stimulation.

Abstract: Experiments were conducted to examine the conversions of phosphorylase b to phosphorylase a in human skeletal muscle during bicycle exercise or isometric contractions. Muscle biopsies were obtained from the vastus lateralis with the needle technique at rest and either during or immediately after activity and frozen in liquid nitrogen within 2--4 s. Total phosphorylase and phosphorylase a activities were differentiated by measurement in the presence and absence of AMP, respectively. At rest 8.5% of the total phosphorylase activity existed in the a form. Little or no change in the percent of phosphorylase in the a form occurred during voluntary dynamic or static muscular activity that produced muscle lactate concentrations in excess of 18 mmol.kg-1 wet muscle. Electrical stimulation of the vastus lateralis muscle also failed to produce an increase in the percentage of phosphorylase a. These data suggest that during exercise the conversion of phosphorylase to the a form is of minor importance. An increased activity of phosphorylase b due to changes in muscle concentrations of ATP, AMP, and inorganic phosphate may regulate glycogenolysis during voluntary exercise in man.

Calcium uptake in skeletal muscle mitochondria. II. The effects of long-term chronic and acute exercise.

Abstract: In order to ascertain the effects of long-term exercise training and long-term exhaustive exercise on mitochondrial 45Ca2+ uptake and related variables in rat skeletal muscle, female rats were randomly divided into three groups: sedentary-rested (SR), trained-rested (TR), and trained-exhausted (TE). The trained groups were exercised five times per week on a treadmill for 22 weeks. At the conclusion of the training period, the TE group was exercised to exhaustion following their daily 1 h run. The 45Ca2+ uptake and endogenous mitochodrial Ca2+ content of skeletal muscle followed stepwise increases of approximately 25% and 50%, respectively, across the groups, suggesting that long-term exercise induces the mitochondria to play an important role as a Ca2+ uptake buffer. A 75--83% reduction in 45Ca2+ binding in the TE group suggests a selective loss and partial saturation of membrane phospholipids with exhaustive exercise. The TE group had a two-fold greater content of mitochondrial Mg2+ than did the rested groups. It is speculated that the mitochondria accumulate Mg2+ during acute exercise to maintain the functional integrity of the membrane, thus offsetting the deleterious effects of excessive Ca2+ uptake

Anthropometric and Densitometric Responses of Women to Specific and General Exercise

Abstract: The viability of the “spot reduction” hypothesis was evaluated by investigating the anthropometric and densitometric effects of two types of exercise programs in a 10-week study using 56 college women. The 27 women assigned to the localized exercise regimen performed calisthenic-type activities concentrated on the abdomen, hips, and thighs while the generalized exercise group (n = 29) participated in a variety of typical aerobic activities. Exercise sessions for both groups were conducted 3 days per week for 30 minutes. The intensity of exercise was equated on the basis of exercise pulse rates. A total of 12 skinfold, girth, densitometric, and derived variables were assessed before and after the experimental period. Application of multivariate and univariate ANOV As revealed significant pre- to posttest changes; however, there was not a significant difference between groups. Therefore, the results indicate that although either general aerobic or localized exercises are effective in altering the a...

Comparison of exercise responses of males and females during acute exposure to hypobaria.

Abstract: : This study was designed to investigate the effects of acute altitude exposure on selected pulmonary, cardiovascular, and metabolic variables in men and women during submax and max work. All testing was conducted in a hypobaric chamber with each subject being tested initially at the terrestrial altitude of 1576 m to which they were acclimated. Subsequent tests were conducted at simulated altitudes of 2743 m and 3962 m. During the recovery period, heart rate was recorded during submax and max exercise as well as recovery. Minute ventilation, breathing frequency, and oxygen pulse were calculated for submax and max exercise. Mean arterial blood pressure was recorded for submax exercise only. Oxygen consumption, respiratory exchange ratio, and ventilation equivalent for oxygen were calculated for max exercise only. Females tolerated hypoxia better during submax work than did men. During maximal work, the men apparently had a better tolerance for hypoxia than did the women.

The role of contraction duration in muscular fatigue.

Abstract: Subjects (N = 19) were college-aged males who engaged in a task that consisted of repetitively contracting the hand-gripping muscles maximally for a 5-minute exercise period so that the intercontraction rest interval was constant at 1 second, and the contraction duration varied on successive randomized occasions between 1, 2, 3, and 4 seconds. Each exercise condition resulted in an exponential fatigue pattern with the main rate constant varying by 22%. The slowest fatigue occurred at a contraction duration of 1 second, and the most rapid occurred at 4 seconds. The values for steady state at the end of exercise decreased as an inverse function of duration of contraction, and the means were significantly different by the end of 5 minutes. Initial strength was not significantly different, but absolute and relative work varied significantly among conditions. The decline in the level of strength by the end of the exercise was a linear function of contraction duration. It is concluded that greater cont...

Active vs. passive recovery from short-term supramaximal exercise.

Abstract: The relative merits of active (zero-load cycling, 50 rpm) vs. passive (quiet sitting) recovery was studied in 14 male subjects following supramaximal exercise (34 kp · rev−1) of short duration (60 seconds). Analyses of the exercise data revealed no statistical differences between 6-second by 6-second or cumulative work-output and oxygen uptake for the two criterion exercise tasks, thereby justifying comparison of the recovery data. Analyses of the gross [Vdot]O2 and HR recovery data for the active and passive conditions revealed statistically significant differences, with the active recovery scores being greater, but the magnitude of these differences between conditions was attributable solely to the ‘cost’ of the extra work of the active recovery.

Swimming--a method to study the physiologic response of the horse to exercise.

Abstract: The literature on exercise physiology in the horse with special reference to swimming is briefly reviewed. The use of a pool for swimming horses is described and a technique discussed for the collection of haematologic and haemodynamic data using this form of exercise.

Changes in 40K Counts with Exercise

Abstract: (1978). Changes in 40K Counts with Exercise. Research Quarterly. American Alliance for Health, Physical Education and Recreation: Vol. 49, No. 1, pp. 95-100.

Glycogen resynthesis in the rat muscle and liver after physical exercise.

Abstract: Glycogen resynthesis was studied in muscles and liver of Wistar rats after a single bout of physical exercise, which included 30 min of enforced swimming in water at 32 degrees C. The experiment was carried out on untrained rats which rested after the exercise from 30 min to 24 h, receiving food ad libitum. During the postexercise restitution a rise was observed in the glycogen content of both tissues. This rise was more rapid in the muscles than in the liver. During the first 9 hours of rest the muscle glycogen content reached 92.6% of the initial value, and after 24 hours it exceeded this value by 20%. On the other hand, the resynthesis of hepatic glycogen was 67% of the initial value after 9 hours, and after 24 hours the liver glycogen content reached only 76.5% of this value. It has been pointed out also that the restitution of glycogen in the muscles occurs in two steps of the intensive increase, while in the liver it is more steady.

Submaximal Exercise Testing Treadmill and Floor Walking.

Abstract: : Exercise testing has been used as the basis for exercise prescriptions for a variety of patients. Exercise tests are performed using standardized ergometers such as a treadmill, bicycle, or steps. There have been, however, several drawbacks to these ergometers which limit their clinical utility. Tests performed on the treadmill have been equated to floor walking, although this has not been conclusively proven. The purposes of this study, therefore, were to examine the validity of using level walking as a submaximal exercise test, and to compare the energy cost of level treadmill and floor walking. Thirty male subjects walked over three modes of level walking. Oxygen uptake and heart rate values were determined at each walking velocity for each mode. Multiple regression analysis of MAP versus the heart rates associated with the walking velocities demonstrated a reasonably accurate method of predicting MAP. Level walking, therefore, may have possibilities as a submaximal exercise test. Analysis of variance of the linear regression of oxygen uptake versus the square of the walking velocity demonstrated similar slopes and intercepts for circular and treadmill walking, but a significant difference between these two modes and segmental walking.

The Acute Effect of Aerobic Exercise on Measures of Stress.

Abstract: The immediate response of stress to aerobic exercise was measured by utilizing the Palmar Sweat Index (PSI) and the State-Trait Anxiety Inventory (STAI). Forty subjects (20 male and 20 ,female) from the ages of 18-30 sustained q single bout of aerobic activity for 30 minutes at 60 percent of their maximum heart rate. Pre-treatment procedureS included administration of the STAI and obtaining a finger print for determining enumeration of open sweat pores. Each subject's resting heart rate was then determined so that the treadmill could be adjusted until the target heart rate was reached. After the half-hour exercise period, the STAI was readministered to each subject, and a second fingerprint was taken to meas,ure the number of open sweat pores. Results shcoved a significant decrease in both psychological stress as measured by the STAI and in physiological stress as measured by the PSI, (JM) ***********************1.*****k***************************************** Reproductions supplied by EDRS are the best that can be made from the original document. *********************************************************************** THE ACUTE EFFECT OF AEROftIC EXERCISE ON MEASURES OF STRESS Inza L.,Fort Center for Interactive Technolov University of ArKansas Fayetteville' ArKansas U.S. DEPARTMENT OF EDUCATION NATIONAL INSTITUTE OF EDUCATION [ARICA TIONAL RE SOURCES INFORMATION (11ti1 ER (ERIC) tiOn,Intlellf ke, been iItels the pet,. ist t,ftlaettsitl(Ift ffi riqmatIrlq0 Athriorthdrule,fiav,heenMAth,Ionmprow, rIwntdonifiriency.rdy,,spresmfoti,GONA "PERMISSION TO REPRODUCE THIS MATERIAL HAS BEEN GRANTED BY -Iz.i L . FOY+ TO THE EDUCATIONAL RESOURCES INFORMATION CENTER (ERIC)."