Changes in muscle proton transverse relaxation times and acidosis during exercise and recovery
| Autor: | J. P. Letellier, Luke J. Haseler, Robert A. Robergs, Arvind Caprihan, Milton V. Icenogle, H. A. Cheng |
|---|---|
| Rok vydání: | 1995 |
| Předmět: |
Adult
Male Magnetic Resonance Spectroscopy Proton Physiology Physical exercise Spin–spin relaxation Nuclear magnetic resonance Physiology (medical) Image Processing Computer-Assisted medicine Humans Muscle Skeletal Exercise Acidosis Fourier Analysis Muscle fatigue medicine.diagnostic_test Chemistry Magnetic resonance imaging Hydrogen-Ion Concentration Magnetic Resonance Imaging Forearm Muscle relaxation Female medicine.symptom Muscle Contraction Muscle contraction |
| Zdroj: | Journal of Applied Physiology. 79:1370-1378 |
| ISSN: | 1522-1601 8750-7587 |
| DOI: | 10.1152/jappl.1995.79.4.1370 |
| Popis: | We studied changes in muscle proton (1H) transverse relaxation times (T2) by magnetic resonance imaging during exercise and compared these changes with alterations in muscle metabolism measured by phosphorus-31 magnetic resonance spectroscopy (31P-MRS). Eleven subjects completed two trials of intermittent incremental forearm wrist flexion exercise requiring 30 contractions/min for 5 min, 7 min of recovery between stages, and 5-N load increments/stage. Between stages of the first trial, T2 images of muscle 1H were obtained. Muscle T2 increased from 27.3 +/- 1.1 (SD) ms at rest to 35.8 +/- 3.6 ms after volitional fatigue (P < 0.05), whereas less active wrist extensor muscle T2 remained unchanged (26.8 +/- 0.9 to 28.8 +/- 1.6 ms; P > 0.05). After localizing the predominant muscle recruited from the T2 images, subjects completed an identical trial at least 1 wk later but involving surface coil 31P-MRS of the T2-enhanced muscle to measure the H+ concentration ([H+]). Intramuscular [H+] of T2-enhancing muscle increased from 1.1 +/- 0.1 x 10(-7) M at rest to 4.1 +/- 2.0 x 10(-7) M after volitional fatigue. Both muscle T2 and intramuscular [H+] increased in a bimodal manner, with T2 increasing before muscle [H+] (P < 0.05). The correlation coefficient between the percent change in T2 and muscle [H+] during exercise was +0.74 (range 0.48–0.98; P < 0.05) and +0.47 during recovery. After 12 min of recovery, muscle [H+] decreased to 1.4 +/- 0.3 x 10(-7) M (P < 0.05), and T2 remained close to postexercise values (32.2 +/- 3.1 ms, P > 0.05). The data indicate that 1) the T2 increases during increases in exercise intensity are nonlinear, 2) the T2 increases during exercise are significantly correlated with increases in [H+], and 3) the slow recovery of T2 compared with [H+] indicates that [H+] has a minor contribution to the recovery in T2. |
| Databáze: | OpenAIRE |
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