Thyroid Hormone Concentrations and Muscle Metabolism in Amenorrheic and Eumenorrheic Athletes

1998 ◽  
Vol 23 (3) ◽  
pp. 293-306 ◽  
Author(s):  
Vicki J. Harber ◽  
Stewart R. Petersen ◽  
Philip D. Chilibeck
Keyword(s):  
Thyroid Hormone ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Inorganic Phosphate ◽  
Plantar Flexion ◽  
Muscle Metabolism ◽  
Resonance Spectroscopy ◽  
Recovery Rates ◽  
Exercise Muscle ◽  
The Relationship

The relationship between resting thyroid hormone concentrations and exercise muscle metabolism was examined among eumenorrheic endurance-trained (n = 11), amenorrheic endurance-trained (n = 8), and eumenorrheic nonathletic (n = 13) subjects. Muscle metabolism was assessed with 31Phosphorous magnetic resonance spectroscopy by measuring changes in phosphocreatine (PCr), inorganic phosphate (Pi), and pH during plantar flexion exercise and recovery. All groups had similar Pi/PCr ratios and pH changes during exercise. Eumenorrheic endurance-trained subjects had faster recovery rates for PCr and Pi/PCr following exercise compared to the nonathletes (p < .05) and faster recovery rates for PCr compared to amenorrheic subjects (p < .05). Thyroxine (T4) and triiodothyronine (T3) levels were significantly lower in amenorrheic subjects compared to both eumenorrheic groups (p < .05). It was concluded that routine training enhances muscle metabolism, as measured by phosphate recovery kinetics. This enhancement was not evident in amenorrheic athletes with reduced T3 and T4 concentrations. Key words:31Phosphorous magnetic resonance spectroscopy, phosphocreatine, inorganic phosphate, T3, T4, females

Muscle metabolism in older subjects using 31P magnetic resonance spectroscopy

1991 ◽  
Vol 69 (5) ◽  
pp. 576-580 ◽  
Author(s):  
Kevin K. McCully ◽  
Mary Ann Forciea ◽  
Laurita M. Hack ◽  
Eileen Donlon ◽  
Roger W. Wheatley ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Time Constant ◽  
Plantar Flexion ◽  
Muscle Metabolism ◽  
The Elderly ◽  
Elderly Subjects ◽  
Resonance Spectroscopy ◽  
Medical Problems ◽  
Age Related

We used phosphorus magnetic resonance spectroscopy to study the calf muscles of elderly normal (mean ± SD) (80.0 ± 5.12 years), elderly impaired (80.7 ± 0.58 years), old normal (66.8 ± 1.92 years), and young normal people (24.6 ± 4.72 years). Relative levels of inorganic phosphate (Pi), phosphocreatine (PCr), and adenosine triphosphate were measured with a 1.9-tesla, 30-cm bore magnet at rest and following plantra flexon exercise. No differences were found at rest or during recovery from exercise in the elderly normal subjects with respect to gender or the presence of stable medical problems treated with medication. At rest there was an age-related decrease in the ratio of PCr/Pi. After exercise, the time constant of PCr recovery increased with age. A mild 7-week exercise regimen consisting of plantar flexion had no effect on time constant of PCr recovery in the elderly subjects. Four elderly impaired subjects had lower PCr/Pi ratios at rest and slower time constant of PCr recovery after exercise than normal elderly subjects. We conclude that gender and the presence of stable medical problems had no effect on muscle metabolism in the elderly and that the elderly recovered slower than young controls. This slower recovery was not corrected with a mild exercise program.Key words: human muscle, aging, exercise, nuclear magnetic resonance, gastrocnemius.

Muscle metabolism in track athletes, using 31P magnetic resonance spectroscopy

1992 ◽  
Vol 70 (10) ◽  
pp. 1353-1359 ◽  
Author(s):  
Kevin K. McCully ◽  
Krista Vandenborne ◽  
Kenny DeMeirleir ◽  
Joel D. Posner ◽  
John S. Leigh Jr.
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Plantar Flexion ◽  
Muscle Metabolism ◽  
Oxidative Capacity ◽  
Resonance Spectroscopy ◽  
Distance Runners ◽  
Long Distance ◽  
Muscle Weight ◽  
Track Athletes

We tested whether preferred running event in track athletes would correlate with the initial rate of phosphocreatine (PCr) resynthesis following submaximal exercise. PCr recovery was measured in the calf muscles of 16 male track athletes and 7 male control subjects following 5 min of repeated plantar flexion against resistance. Pi, PCr, and pH were measured using phosphorus magnetic resonance spectroscopy (31P MRS) with an 8-cm surface coil in a 1.8-T magnet. During exercise, work levels were gradually increased to deplete PCr to 50–60% of the initial value. No drop in pH was seen in any of the subjects during this exercise. The areas of the PCr peaks following exercise were fit to monoexponential curves. Two or three tests were performed on each subject and the results averaged. Athletes were divided into three groups based on their primary event: sprinters running 400 m or less, middle-distance athletes running 400–1500 m, and long-distance athletes running farther than 1500 m. The maximal rates of PCr resynthesis (mmol∙min−1∙kg−1 muscle weight) were 64.8 ± 8.6, for long-distance runners; 41.4 ± 11, for middle-distance runners; 32.0 ± 7.0, for sprinters; and 38.6 ± 10, for controls (mean ± SE). The faster PCr recovery rates seen in long-distance runners compared with sprinters indicate greater oxidative capacity, which is consistent with the known differences between athletes in these events.Key words: exercise recovery, human, phosphocreatine.

Biochemical adaptations to training: implications for resisting muscle fatigue

1991 ◽  
Vol 69 (2) ◽  
pp. 274-278 ◽  
Author(s):  
Kevin K. McCully ◽  
B. J. Clark ◽  
Jane A. Kent ◽  
John Wilson ◽  
Britton Chance
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Muscle Fatigue ◽  
Endurance Training ◽  
Inorganic Phosphate ◽  
Muscle Metabolism ◽  
Resonance Spectroscopy ◽  
Effect Of Ph ◽  
Force Development ◽  
Generating Capacity

Skeletal muscle activity is invariably associated with a decline in force-generating capacity (fatigue). The build-up of metabolic by-products such as intracellular H+ and inorganic phosphate (Pi) has been shown to be one of the potential mechanisms of muscle fatigue. The use of phosphorus magnetic resonance spectroscopy is a repeatable and useful tool to study the effect of pH and Pi on force development. When maximal exercise is preceded by submaximal exercise to reduce the starting muscle pH and increase Pi; the degree of muscle fatigue correlates more strongly with [Formula: see text] than pH or R alone. However, other studies in humans have found that [Formula: see text] does not always correlate well with fatigue. The use of ramp exercise protocols allow repeatable and sensitive measurement of changes in muscle metabolism in response to endurance training. Chronic electrical stimulation in dogs and endurance training in humans results in reduced pH and Pi changes at the same exercise intensities. This means that the effect of pH and Pi in depressing force development is reduced, which could partially explain the increased fatigue resistance seen following endurance training.Key words: magnetic resonance spectroscopy (31P-MRS), muscle metabolism, exercise, inorganic phosphate, pH.

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)

Simultaneous in vivo measurements of HbO2 saturation and PCr kinetics after exercise in normal humans

1994 ◽  
Vol 77 (1) ◽  
pp. 5-10 ◽  
Author(s):  
K. K. McCully ◽  
S. Iotti ◽  
K. Kendrick ◽  
Z. Wang ◽  
J. D. Posner ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Time Constant ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Plantar Flexion ◽  
Resonance Spectroscopy ◽  
Ph Values

Simultaneous measurements of phosphocreatine (PCr) and oxyhemoglobin (HbO2) saturation were made during recovery from exercise in calf muscles of five male subjects. PCr was measured using magnetic resonance spectroscopy in a 2.0-T 78-cm-bore magnet with a 9-cm-diam surface coil. Relative HbO2 saturation was measured as the difference in absorption of 750- and 850-nm light with use of near-infrared spectroscopy. The light source and detectors were 3 cm apart. Exercise consisted of isokinetic plantar flexion in a supine position. Two 5-min submaximal protocols were performed with PCr depletion to 60% of resting values and with pH values of > 7.0. Then two 1-min protocols of rapid plantar flexion were performed to deplete PCr values to 5–20% of resting values with pH values of < 6.8. Areas of PCr peaks (every 8 s) and HbO2 saturation (every 1 s) were fit to a monoexponential function, and a time constant was calculated. The PCr time constant was larger after maximal exercise (68.3 +/- 10.5 s) than after submaximal exercise (36.0 +/- 6.5 s), which is consistent with the effects of low pH on PCr recovery. HbO2 resaturation approximated submaximal PCr recovery and was not different between maximal (29.4 +/- 5.5 s) and submaximal (27.6 +/- 6.0 s) exercise. We conclude that magnetic resonance spectroscopy measurements of PCr recovery and near-infrared spectroscopy measurements of recovery of HbO2 saturation provide similar information as long as muscle pH remains near 7.0.

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