31P MRS measurement of mitochondrial function in skeletal muscle: reliability, force-level sensitivity and relation to whole body maximal oxygen uptake

1995 ◽  
Vol 13 (1) ◽  
pp. 14
Author(s):  
D. Enette Larson-Meyer ◽  
Bradley R. Newcomer ◽  
Gary R. Hunter ◽  
Hoby P. Hetherington ◽  
Roland L. Weinsier
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Uptake ◽  
Mitochondrial Function ◽  
Maximal Oxygen Uptake ◽  
Whole Body ◽  
Force Level ◽  
31P Mrs

MUSCLE OXIDATIVE PHOSPHORYLATION BY 31P-MRS: RELIABILITY, FORCE LEVEL SENSITIVITY, AND RELATION TO WHOLE BODY OXYGEN UPTAKE

1999 ◽  
Vol 31 (Supplement) ◽  
pp. S280 ◽  
Author(s):  
K A Landers ◽  
D E Larson ◽  
B R Newcomer ◽  
G R Hunter ◽  
H P Hetherington ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Oxidative Phosphorylation ◽  
Whole Body ◽  
Force Level ◽  
31P Mrs

scholarly journals Malleability of the system in overcoming limitations: functional elements

1985 ◽  
Vol 115 (1) ◽  
pp. 345-354
Author(s):  
B. Saltin
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Uptake ◽  
Maximal Oxygen Uptake ◽  
Mean Transit Time ◽  
The Body ◽  
Whole Body ◽  
Limiting Factor ◽  
Primary Role ◽  
Pump Function ◽  
Cardiac Pump Function

Three different views can be found in the literature concerning the classical question in exercise physiology: what limits maximal oxygen uptake in man? Some authors believe that the limitation is the maximal rate of oxygen delivery by the cardiovascular system. Others argue that oxygen uptake is limited by the capillary bed or metabolic capacity of skeletal muscle, and the third line of thought is that no single factor can be found to be directly limiting as all links in the oxygen transport are so closely matched. The stand taken in this paper is that the skeletal muscle of man can be excluded as a limiting factor for maximal oxygen uptake in whole body exercise. It can be shown, by direct measurements, that in sedentary and in trained man maximal perfusion and oxygen utilization of skeletal muscle is so high that if all muscles in the body were engaged in intense exercise, the cardiac pump function would have to be 2–3 fold larger than it is. What happens in whole body exercise is that each muscle group receives only a fraction of the blood it can accommodate. The primary role for a larger capillary network observed in trained muscles is to keep or extend mean transit time. Elevated mitochondrial enzyme activities affect the metabolic response (i.e. lipid oxidation is elevated in trained muscles). However, these adaptations are not necessary for increasing the maximal oxygen uptake of man, as the capacity of the heart is limiting. Improved training techniques (which induce even larger improvements in cardiac pump function) may reveal that pulmonary diffusion capacity is the limiting factor.

Effect of aging on response to exercise training in humans: skeletal muscle GLUT-4 and insulin sensitivity

1999 ◽  
Vol 86 (6) ◽  
pp. 2019-2025 ◽  
Author(s):  
Julie H. Cox ◽  
Ronald N. Cortright ◽  
G. Lynis Dohm ◽  
Joseph A. Houmard
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Exercise Training ◽  
Oxygen Uptake ◽  
Maximal Oxygen Uptake ◽  
Insulin Action ◽  
Whole Body ◽  
Sensitivity Index ◽  
Intravenous Glucose ◽  
Glut 4

The purpose of this study was to compare the effects of short-term exercise training on insulin-responsive glucose transporter (GLUT-4) concentration and insulin sensitivity in young and older individuals. Young and older women [22.4 ± 0.8 (SE) yr, n = 9; and 60.9 ± 1.0 yr, n = 10] and men (20.9 ± 0.9, n = 9; 56.5 ± 1.9 yr, n = 8), respectively, were studied before and after 7 consecutive days of exercise training (1 h/day, ≈75% maximal oxygen uptake). The older groups had more adipose tissue, increased central adiposity, and a lower maximal oxygen uptake. Despite these differences, increases in whole body insulin action (insulin sensitivity index, determined with an intravenous glucose tolerance test and minimal-model analysis) with training were similar regardless of age, in both the women and men (mean increase of 2.2 ± 0.3-fold). This was accompanied by similar relative increases in muscle (vastus lateralis) GLUT-4 protein concentration, irrespective of age (mean increase of 3.1 ± 0.7-fold). Body mass did not change with training in any of the groups. These data suggest that older human skeletal muscle retains the ability to rapidly increase muscle GLUT-4 and improve insulin action with endurance training.

Thermogenic response to epinephrine in the forearm and abdominal subcutaneous adipose tissue

1992 ◽  
Vol 263 (5) ◽  
pp. E850-E855 ◽  
Author(s):  
L. Simonsen ◽  
J. Bulow ◽  
J. Madsen ◽  
N. J. Christensen
Keyword(s):  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Energy Expenditure ◽  
Oxygen Uptake ◽  
Glucose Uptake ◽  
Subcutaneous Adipose Tissue ◽  
Whole Body ◽  
Epinephrine Infusion ◽  
Basal Period ◽  
Subcutaneous Adipose

Whole body energy expenditure, thermogenic and metabolic changes in the forearm, and intercellular glucose concentrations in subcutaneous adipose tissue on the abdomen determined by microdialysis were measured during epinephrine infusion in healthy subjects. After a control period, epinephrine was infused at rates of 0.2 and 0.4 nmol.kg-1 x min-1. Whole body resting energy expenditure was 4.36 +/- 0.56 (SD) kJ/min. Energy expenditure increased to 5.14 +/- 0.74 and 5.46 +/- 0.79 kJ/min, respectively (P < 0.001), during the epinephrine infusions. Respiratory exchange ratio was 0.80 +/- 0.04 in the resting state and did not change. Local forearm oxygen uptake was 3.9 +/- 1.3 mumol.100 g-1 x min-1 in the basal period. During epinephrine infusion, it increased to 5.8 +/- 2.1 (P < 0.03) and 7.5 +/- 2.3 mumol.100 g-1 x min-1 (P < 0.001). Local forearm glucose uptake was 0.160 +/- 0.105 mumol.100 g-1 x min-1 and increased to 0.586 +/- 0.445 and 0.760 +/- 0.534 mumol.100 g-1 x min-1 (P < 0.025). The intercellular glucose concentration in the subcutaneous adipose tissue on the abdomen was equal to the arterial concentration in the basal period but did not increase as much during infusion of epinephrine, indicating glucose uptake in adipose tissue in this condition. If it is assumed that forearm skeletal muscle is representative for the average skeletal muscle, it can be calculated that on average 40% of the enhanced whole body oxygen uptake induced by infusion of epinephrine is taking place in skeletal muscle. It is proposed that adipose tissue may contribute to epinephrine-induced thermogenesis.

Mean myoglobin oxygen tension during exercise at maximal oxygen uptake

1975 ◽  
Vol 39 (1) ◽  
pp. 135-144 ◽  
Author(s):  
B. J. Clark ◽  
R. F. Coburn
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Uptake ◽  
Aerobic Capacity ◽  
Maximal Oxygen Uptake ◽  
Bicycle Ergometer ◽  
Limiting Factors ◽  
Considerable Variability ◽  
Vo2 Max ◽  
The Subject ◽  
Total Body

Changes in intracellular Po2 in myoglobin containing skeletal muscle during exercise were estimated in normal nonathlete subjects from measurements of shifts of CO between blood and muscle under conditions where the total body CO stores remained constant. Exercise was performed on a bicycle ergometer. In 1.5–2 and 6–7 min runs at Vo2 max with the subject breathing 21% O2, mean MbCO/HbCO increased 146 +/- 7 and 163 +/- 11% of resting values, respectively (P less than 0.05). With the subjects breathing 13–14% O2, in 1.5–2 and 6–7 min runs, Vo2 max fell an average of 4.3 +/- 5.1% and 12.0 +/- 5.2%, respectively, and mean MbCO/HbCO increased to 233 +/- 18% and 210 +/- 52% of resting value, respectively (P less than 0.05). These findings suggest that mean myoglobin Po2 fell during exercise at Vo2 max, with the subjects breathing 21% O2 and the decrease in mean myoglobin Po2 was greater with the subject breathing 13–14% O2. There was considerable variability in different subjects and in some, the data were not consistent with intracellular O2 availability limiting aerobic metabolism. The data support a postulate that there are several limiting factors for the aerobic capacity, including intracellular O2 availability.

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