Training-induced skeletal muscle adaptations are independent of systemic adaptations

1990 ◽  
Vol 68 (1) ◽  
pp. 289-294 ◽  
Author(s):  
J. R. Minotti ◽  
E. C. Johnson ◽  
T. L. Hudson ◽  
G. Zuroske ◽  
E. Fukushima ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Magnetic Resonance ◽  
Muscle Mass ◽  
Normal Subjects ◽  
Oxidative Capacity ◽  
Venous Occlusion ◽  
Resonance Spectroscopy ◽  
Wrist Flexion ◽  
Vo2 Max

To isolate the peripheral adaptations to training, five normal subjects exercised the nondominant (ND) wrist flexors for 41 +/- 11 days, maintaining an exercise intensity below the threshold required for cardiovascular adaptations. Before and after training, intracellular pH and the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) were measured by 31P magnetic resonance spectroscopy. Also maximal O2 consumption (VO2 max), muscle mass, and forearm blood flow were determined by graded systemic exercise, magnetic resonance imaging, and venous occlusion plethysmography, respectively. Blood flow, Pi/PCr, and pH were measured in both forearms at rest and during submaximal wrist flexion at 5, 23, and 46 J/min. Training did not affect VO2 max, exercise blood flow, or muscle mass. Resting pH, Pi/PCr, and blood flow were also unchanged. After training, the ND forearm demonstrated significantly lower Pi/PCr at 23 and 46 J/min. Endurance, measured as the number of contractions to exhaustion, also was increased significantly (63%) after training in the ND forearm. We conclude that 1) forearm training results in a lower Pi/PCr at identical submaximal work loads; 2) this improvement is independent of changes in VO2 max, muscle mass, or limb blood flow; and 3) these differences are associated with improved endurance and may reflect improved oxidative capacity of skeletal muscle.

Forearm metabolic asymmetry detected by 31P-NMR during submaximal exercise

1989 ◽  
Vol 67 (1) ◽  
pp. 324-329 ◽  
Author(s):  
J. R. Minotti ◽  
E. C. Johnson ◽  
T. L. Hudson ◽  
R. R. Sibbitt ◽  
L. E. Wise ◽  
...  
Keyword(s):  
Blood Flow ◽  
Energy Metabolism ◽  
Magnetic Resonance ◽  
Muscle Mass ◽  
Forearm Blood Flow ◽  
Training Stimulus ◽  
Normal Subjects ◽  
Submaximal Exercise ◽  
Resonance Spectroscopy ◽  
Wrist Flexion

This study evaluated the relationship of skeletal muscle energy metabolism to forearm blood flow and muscle mass in the dominant (D) and nondominant (ND) forearms of normal subjects. 31P-Magnetic resonance spectroscopy was used to determine intracellular pH and the ratio of inorganic phosphate to phosphocreatine (Pi/PCr), an index of energy metabolism. Forearm blood flow and muscle mass were measured by venous occlusion plethysmography and magnetic resonance imaging, respectively. Metabolic measurements and flow were determined at rest and during submaximal exercise in both forearms. After a warm-up period, six normal right-handed male subjects performed 7.5 min of wrist flexion exercise in the magnet (1 contraction every 5 s), first with the ND forearm and then with the D forearm, at 23, 46, and 69 J/min. At rest, there were no differences between forearms in Pi/PCr or pH. However, at each work load the D forearm demonstrated significantly lower Pi/PCr and higher pH than the ND forearm. Blood flow was not significantly different between the forearms at rest or during exercise. Because these subjects were not engaged in unilateral arm training, we conclude that 1) Pi/PCr is lower and pH is higher in the D compared with the ND forearm in normal subjects during submaximal exercise, 2) these differences are independent of muscle mass and blood flow, and 3) the cumulative effect of long-term, low-level daily activity provides an adequate training stimulus for muscular metabolic adaptations.

Contribution of prostaglandins to exercise-induced vasodilation in humans

1993 ◽  
Vol 265 (1) ◽  
pp. H171-H175 ◽  
Author(s):  
J. R. Wilson ◽  
S. C. Kapoor
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Forearm Blood Flow ◽  
Venous Catheter ◽  
Normal Subjects ◽  
Wrist Flexion ◽  
Arterial Infusion ◽  
Prostaglandin Release ◽  
Exercise Induced ◽  
Arteriolar Vasodilation

It has been postulated that endothelial release of prostaglandins contributes to exercise-induced vasodilation of skeletal muscle arterioles. To test this hypothesis, 12 normal subjects underwent brachial arterial and venous catheter insertion and instrumentation of their forearm to measure plethysmographic forearm blood flow. Forearm blood flow and arterial and venous 6-ketoprostaglandin F1 alpha (PGF1 alpha) and prostaglandin E2 (PGE2) were then measured during two levels of wrist flexion exercise (0.2 and 0.4 W). In nine of the subjects, exercise was repeated after intra-arterial infusion of indomethacin (0.3 mg/100 ml forearm vol). Exercise increased forearm blood flow (2.0 +/- 0.2 to 12.1 +/- 1.1 ml.min-1.100 ml-1) and forearm release of PGF1 alpha (162 +/- 28 to 766 +/- 193 pg.min-1.100 ml-1) and PGE2 (26 +/- 6 to 125 +/- 46 pg.min-1.100 ml-1) (all P < 0.05). Indomethacin virtually abolished forearm prostaglandin release and reduced forearm blood flow at rest (2.2 +/- 0.2 to 1.7 +/- 0.2 ml.min-1.100 ml-1), at 0.2 W (6.3 +/- 0.7 to 5.4 +/- 0.7 ml.min-1.100 ml-1), and at 0.4 W (12.2 +/- 1.5 to 10.3 +/- 1.3 ml.min-1.100 ml-1) (all P < 0.02). These data suggest that release of vasodilatory prostaglandins contributes to exercise-induced arteriolar vasodilation and hyperemia in skeletal muscle.

Contribution of endothelium-derived relaxing factor to exercise-induced vasodilation in humans

1993 ◽  
Vol 75 (6) ◽  
pp. 2740-2744 ◽  
Author(s):  
J. R. Wilson ◽  
S. Kapoor
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Vascular Endothelium ◽  
Forearm Blood Flow ◽  
Specific Inhibitor ◽  
Normal Subjects ◽  
Wrist Flexion ◽  
Relaxing Factor ◽  
Endothelium Derived Relaxing Factor ◽  
Arteriolar Vasodilation

Release of endothelium-derived relaxing factor (EDRF) from the vascular endothelium may contribute to skeletal muscle arteriolar vasodilation during exercise. The present study was undertaken to test this hypothesis. Ten normal subjects underwent brachial arterial catheter insertion and instrumentation of their forearm to measure plethysmographic forearm blood flow. Forearm blood flow was then measured at rest, during two levels of wrist flexion exercise (0.2 and 0.4 W), and during 0.4-W exercise with concurrent infusion of norepinephrine (100 ng.min-1 x 100 ml forearm volume-1). Measurements were made with and without infusion of N-monomethyl-L-arginine (L-NMMA) (0.1–0.2 mg.min-1 x 100 ml forearm volume-1), a specific inhibitor of EDRF synthesis. Infusion of L-NMMA reduced resting forearm blood flow (control: 2.5 +/- 0.4 vs. L-NMMA: 1.5 +/- 0.1 ml.min-1 x 100 ml-1) and markedly reduced forearm blood flow response to acetylcholine (5 micrograms.min-1 x 100 ml forearm volume-1) (control: 20.2 +/- 2.9 vs L-NMMA: 4.0 +/- 1.0 ml.min-1 x 100 ml-1; both P < 0.01). However, L-NMMA had no significant effect on flow responses to exercise (0.2 W: 8.3 +/- 1.1 vs. 8.3 +/- 1.2; 0.4 W: 13.8 +/- 1.7 vs. 13.5 +/- 1.7; 0.4 W + norepinephrine: 10.3 +/- 2.4 vs. 9.4 +/- 2.6 ml.min-1 x 100 ml-1; all P = NS). These findings suggest that release of EDRF from the vascular endothelium contributes to skeletal muscle arteriolar vasodilation at rest but does not contribute to the arteriolar vasodilation produced by exercise.

Endurance-Trained and Untrained Skeletal Muscle Bioenergetics Observed With Magnetic Resonance Spectroscopy

1996 ◽  
Vol 21 (4) ◽  
pp. 251-263 ◽  
Author(s):  
Bart M. Guthrie ◽  
Simon P. Frostick ◽  
David J. Mikulis ◽  
K. Wayne Marshall ◽  
Jack Goodman ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Intracellular Ph ◽  
Adenosine Triphosphate ◽  
Inorganic Phosphate ◽  
Isometric Exercise ◽  
Oxidative Capacity ◽  
Resonance Spectroscopy ◽  
Trained Subjects

Resting and submaximal isometric exercise 31P magnetic resonance spectroscopy (MRS) was carried out on 7 endurance-trained males (26.0 ± 3 yrs) and 7 sedentary males (27.0 ± 4 yrs). Spectral analysis provided peak areas of phosphocreatine (PCr), inorganic phosphate (Pi), adenosine triphosphate (ATP), and the chemical shift of Pi relative to PCr. The ratio of PCr/Pi was moderately lower during rest (preexercise p =.13, postexercise p =.18), and significantly higher during exercise (p < .05) in the trained subjects. Intracellular pH patterns were the same for both groups; a transient alkalosis was observed at the onset of exercise with a return to resting levels after 2 min. Differences suggest improved ATP resynthesis rate in the trained subjects during exercise. Intracellular pH changes can be attributed to the utilization of hydrogen ions that accompany PCr hydrolysis during work. The findings are congruent with previous reports indicating a superior oxidative capacity in trained skeletal muscle. Key words: 31P MRS, isometric exercise, phosphocreatine, inorganic phosphate, adenosine triphosphate, intracellular pH

Skeletal Muscle Metabolism in Heart Failure: A 31P Nuclear Magnetic Resonance Spectroscopy Study of Leg Muscle

1990 ◽  
Vol 79 (6) ◽  
pp. 583-589 ◽  
Author(s):  
Leonard Arnolda ◽  
Michael Conway ◽  
Michael Dolecki ◽  
Hasanat Sharif ◽  
Bheeshma Rajagopalan ◽  
...  
Keyword(s):  
Heart Failure ◽  
Skeletal Muscle ◽  
Nuclear Magnetic Resonance ◽  
Blood Flow ◽  
Magnetic Resonance ◽  
Inorganic Phosphate ◽  
Gastrocnemius Muscle ◽  
Resonance Spectroscopy ◽  
Control Subjects ◽  
Patients With Heart Failure

1. The gastrocnemius muscle of seven patients with mild to moderate chronic heart failure and of five healthy control subjects was studied using 31P nuclear magnetic resonance spectroscopy. Spectra were collected at rest and during an incremental, symptom-limited, exercise protocol. Blood flow was measured in the same study during brief interruptions to exercise. 2. The phosphocreatine/(phosphocreatine plus inorganic phosphate) ratio was lower in patients with heart failure than in control subjects at an exercise rate of 1.5 W, although intracellular pH and blood flow were similar. 3. The cytosolic free adenosine 5′-diphosphate concentration was markedly increased in patients with heart failure exercising at 1.5 W compared with control subjects exercising at the same workload. 4. Although the maximum workload achieved by patients with heart failure was less than half of that reached by control subjects, the pH and the phospho-creatine/(phosphocreatine plus inorganic phosphate) ratio were lower in patients with heart failure at maximal load. Blood flow was less at maximal exercise in patients with heart failure than in control subjects in keeping with the reduced work load. 5. The phosphocreatine depletion induced in the gastrocnemius muscle by exercise was more severe than previously described in the forearm of patients with heart failure. 6. Metabolic abnormalities in skeletal muscle may contribute to exercise intolerance in heart failure, particularly during submaximal exercise.

Muscle metabolism during exercise in young and older untrained and endurance-trained men

1993 ◽  
Vol 75 (5) ◽  
pp. 2125-2133 ◽  
Author(s):  
A. R. Coggan ◽  
A. M. Abduljalil ◽  
S. C. Swanson ◽  
M. S. Earle ◽  
J. W. Farris ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Muscle Mass ◽  
Citrate Synthase ◽  
Metabolic Response ◽  
Plantar Flexion ◽  
Muscle Metabolism ◽  
Resonance Spectroscopy ◽  
Age Related ◽  
Rate Of Increase ◽  
Response To Exercise

To examine effects of aging and endurance training on human muscle metabolism during exercise, 31P magnetic resonance spectroscopy was used to study the metabolic response to exercise in young (21–33 yr) and older (58–68 yr) untrained and endurance-trained men (n = 6/group). Subjects performed graded plantar flexion exercise with the right leg, with metabolic responses measured using a 31P surface coil placed over the lateral head of the gastrocnemius muscle. Muscle biopsy samples were also obtained for determination of citrate synthase activity. Rate of increase in P(i)-to-phosphocreatine ratio with increasing power output was greater (P < 0.01) in older untrained [0.058 +/- 0.022 (SD) W-1] and trained men (0.042 +/- 0.010 W-1) than in young untrained (0.038 +/- 0.017 W-1) and trained men (0.024 +/- 0.010 W-1). Plantar flexor muscle cross-sectional area and volume (determined using 1H magnetic resonance imaging) were 11–12% (P < 0.05) and 16–18% (P < 0.01) smaller, respectively, in older men. When corrected for this difference in muscle mass, age-related differences in metabolic response to exercise were reduced by approximately 50% but remained significant (P < 0.05). Citrate synthase activity was approximately 20% lower (P < 0.001) in older untrained and trained men than in corresponding young groups and was inversely related to P(i)-phosphocreatine slope (r = -0.63, P < 0.001). Age-related reductions in exercise capacity were associated with an altered muscle metabolic response to exercise, which appeared to be due to smaller muscle mass and lower muscle respiratory capacity of older subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

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