Skeletal muscle metabolism and work capacity: a 31P-NMR study of Andean natives and lowlanders

Matheson, Gordon O.; Allen, Peter S.; Ellinger, D. C.; Hanstock, Christopher C.; Gheorghiu, D.; McKenzie, D. C.; Stanley, C.; Parkhouse, W. S.; Hochachka, P. W.

doi:10.1152/jappl.1991.70.5.1963

Cited by 78 publications

(46 citation statements)

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“…These results are in agreement with the reduced lactate concentration commonly observed in endurance-trained subject during a submaximal exercise (Gollnick et al 1986) and with the lower Pi/PCr ratio recorded in endurance-trained subjects for a given work-rate (Laurent et al 1992;Matheson et al 1991) considering that the reduced ratio illustrates a higher mitochondrial capacity (Chance et al 1986). Such a reduced Pi/PCr ratio has also been reported in longitudinal studies aiming at investigating the metabolic effects of training (Kent-Braun et al 1990;Minotti et al 1990) and in chronically electrically stimulated muscle (Clark et al 1988).…”

Section: Discussionsupporting

confidence: 89%

Does oxidative capacity affect energy cost? An in vivo MR investigation of skeletal muscle energetics

Layec

Bringard²,

Vilmen

et al. 2009

Eur J Appl Physiol

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Investigations of training effects on exercise energy cost have yielded conflicting results. The purpose of the present study was to compare quadriceps energy cost and oxidative capacity between endurance-trained and sedentary subjects during a heavy dynamic knee extension exercise. We quantified the rates of ATP turnover from oxidative and anaerobic pathways with (31)P-MRS, and we measured simultaneously pulmonary oxygen uptake in order to assess both total ATP production [i.e., energy cost (EC)] and O(2) consumption (O(2) cost) scaled to power output. Seven sedentary (SED) and seven endurance-trained (TRA) subjects performed a dynamic standardized rest-exercise-recovery protocol at an exercise intensity corresponding to 35% of maximal voluntary contraction. We showed that during a dynamic heavy exercise, the O(2) cost and EC were similar in the SED and endurance-trained groups. For a given EC, endurance-trained subjects exhibited a higher relative mitochondrial contribution to ATP production at the muscle level (84 +/- 12% in TRA and 57 +/- 12% in SED; P < 0.01) whereas the anaerobic contribution was reduced (18 +/- 12% in TRA and 44 +/- 11% in SED; P < 0.01). Our results obtained in vivo illustrate that on the one hand the beneficial effects of endurance training are not related to any reduction in EC or O(2) cost and on the other hand that this similar EC was linked to a change regarding the contribution of anaerobic and oxidative processes to energy production, i.e., a greater aerobic energy contribution associated with a concomitant reduction of the anaerobic energy supply.

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Section: Discussionsupporting

confidence: 89%

Does oxidative capacity affect energy cost? An in vivo MR investigation of skeletal muscle energetics

Layec

Bringard²,

Vilmen

et al. 2009

Eur J Appl Physiol

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“…Enhanced ATP demand/coupling during hibernation and arousal is another possible explanation for unexpectedly stable arterial blood lactate levels during arousal (36) and is consistent with evidence showing that energy balance is maintained during arousal from hibernation (32). In contrast to the absence of a reliable lactate response during arousal, exposure of euthermic AGS to 8% O 2 increases arterial blood lactate concentrations threefold or more (Ma YL, Cozad KD, Rivera PM, Zhao, HW, and Drew KL, unpublished observations).…”

Section: Discussionsupporting

confidence: 86%

Absence of cellular stress in brain after hypoxia induced by arousal from hibernation in Arctic ground squirrels

Liu

Zhu²,

Rivera

et al. 2005

American Journal of Physiology-Regulatory, Integrative and Comp

117

133

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Although hypoxia tolerance in heterothermic mammals is well established, it is unclear whether the adaptive significance stems from hypoxia or other cellular challenge associated with euthermy, hibernation, or arousal. In the present study, blood gases, hemoglobin O 2 saturation (SO2), and indexes of cellular and physiological stress were measured during hibernation and euthermy and after arousal thermogenesis. Results show that arterial O 2 tension (PaO 2 ) and SO2 are severely diminished during arousal and that hypoxia-inducible factor (HIF)-1␣ accumulates in brain. Despite evidence of hypoxia, neither cellular nor oxidative stress, as indicated by inducible nitric oxide synthase (iNOS) levels and oxidative modification of biomolecules, was observed during late arousal from hibernation. Compared with rats, hibernating Arctic ground squirrels (Spermophilus parryii) are well oxygenated with no evidence of cellular stress, inflammatory response, neuronal pathology, or oxidative modification following the period of high metabolic demand necessary for arousal. In contrast, euthermic Arctic ground squirrels experience mild, chronic hypoxia with low SO 2 and accumulation of HIF-1␣ and iNOS and demonstrate the greatest degree of cellular stress in brain. These results suggest that Arctic ground squirrels experience and tolerate endogenous hypoxia during euthermy and arousal.torpor; ischemia; stroke; Spermophilus parryii; reperfusion; inflammation; oxidative stress HIBERNATION IS A UNIQUE PHYSIOLOGICAL STATE of prolonged periods of low body temperature, metabolism, blood flow, and other physiological processes that are disrupted by brief periodic arousal episodes when animals rewarm and reperfuse metabolically active tissues (7). During arousal thermogenesis, blood flow returns to brain and other organs in a reperfusionlike manner at a time of maximal oxygen demand (42, 58). Preservation of neuronal and other cellular morphology during low cerebral blood flow demonstrates that hibernating mammals tolerate pronounced fluctuations in blood flow (16,61). Physiological and cellular stress experienced during euthermy, hibernation, and arousal is less well characterized.Arterial oxygen tension (Pa O 2 ) and tissue lactate measurements show that hibernating ground squirrels are well oxygenated (16,20), sometimes exceeding values in the euthermic state (15). In contrast, oxygen supply may become limiting during arousal thermogenesis. Increases in brain tissue lactate levels during peak oxygen consumption during arousal from hibernation in bats suggest these animals experience oxygen deficiency during arousal and reperfusion (30). However, because tissue lactate was not reported for euthermic bats, it is unclear how brain tissue hypoxia experienced during arousal compares to the euthermic state. Moreover, Pa O 2 was not measured to address the relationship between blood and tissue oxygenation during euthermy, hibernation, and arousal. To characterize physiological challenges associated with arousal thermogenesis, we evaluated b...

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“…PCr and Pi concentration changes in the gastrocnemius were similar to many earlier data (17) for exercising muscles (Figure 1), i.e., declining PCr during exercise with a concomitant rise in Pi, followed by rapid recoveries during each subsequent rest interval. The chemical shift for Pi also showed a modest adjustment, indicating a modest change in the equilibrium between diprotonated and monoprotonated phosphate.…”

Section: Regulation Of Human Muscle Metabolism During Worksupporting

confidence: 87%

Two research paths for probing the roles of oxygen in metabolic regulation

Hochachka

1999

Braz J Med Biol Res

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Tissues such as skeletal and cardiac muscles must sustain very largescale changes in ATP turnover rate during equally large changes in work. In many skeletal muscles these changes can exceed 100-fold. Examination of a number of cell and whole-organism level systems identifies ATP concentration as a key parameter of the interior milieu that is nearly universally homeostatic ; it is common to observe no change in ATP concentration even while change in its turnover rate can increase or decrease by two orders of magnitude or more. A large number of other intermediates of cellular metabolism are also regulated within narrow concentration ranges, but none seemingly as precisely as is [ATP]. In fact, the only other metabolite in aerobic energy metabolism that is seemingly as homeostatic is oxygen -at least in working muscles where myoglobin serves to buffer oxygen concentrations at stable and constant values at work rates up to the aerobic maximum. In contrast to intracellular oxygen concentration, a 1:1 relationship between oxygen delivery and metabolic rate is observed over biologically realistic and large-magnitude changes in work. The central regulatory question is how the oxygen delivery signal is transmitted to the intracellular metabolic machinery. Traditional explanations assume diffusion as the dominant mechanism, while proponents of an ultrastructurally dominated view of the cell assume an intracellular perfusion system to account for the data which have been most perplexing to metabolic biochemistry so far: the striking lack of correlation between changes in pathway reaction rates and changes in concentrations of pathway substrates, including oxygen and pathway intermediates.

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Skeletal muscle metabolism and work capacity: a 31P-NMR study of Andean natives and lowlanders

Cited by 78 publications

References 0 publications

Does oxidative capacity affect energy cost? An in vivo MR investigation of skeletal muscle energetics

Does oxidative capacity affect energy cost? An in vivo MR investigation of skeletal muscle energetics

Absence of cellular stress in brain after hypoxia induced by arousal from hibernation in Arctic ground squirrels

Two research paths for probing the roles of oxygen in metabolic regulation

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