Muscle metabolic status and acid-base balance during 10-s work:5-s recovery intermittent and continuous exercise

2012 ◽  
Vol 113 (3) ◽  
pp. 410-417 ◽  
Author(s):  
Glen R. Belfry ◽  
Graydon H. Raymer ◽  
Gregory D. Marsh ◽  
Donald H. Paterson ◽  
R. Terry Thompson ◽  
...  
Keyword(s):  
Power Output ◽  
Plantar Flexion ◽  
Average Power ◽  
Rest Period ◽  
Exercise Bout ◽  
Peak Exercise ◽  
Resonance Spectroscopy ◽  
Intracellular Acidosis ◽  
Acid Base Balance ◽  
Base Balance

Gastrocnemius muscle phosphocreatine ([PCr]) and hydrogen ion ([H+]) were measured using 31P-magnetic resonance spectroscopy during repeated bouts of 10-s heavy-intensity (HI) exercise and 5-s rest compared with continuous (CONT) HI exercise. Recreationally active male subjects ( n = 7; 28 yr ± 9 yr) performed on separate occasions 12 min of isotonic plantar flexion (0.75 Hz) CONT and intermittent (INT; 10-s exercise, 5-s rest) exercise. The HI power output in both CONT and INT was set at 50% of the difference between the power output associated with the onset of intracellular acidosis and peak exercise determined from a prior incremental plantar flexion protocol. Intracellular concentrations of [PCr] and [H+] were calculated at 4 s and 9 s of the work period and at 4 s of the rest period in INT and during CONT exercise. [PCr] and [H+] (mean ± SE) were greater at 4 s of the rest periods vs. 9 s of exercise over the course of the INT exercise bout: [PCr] (20.7 mM ± 0.6 vs. 18.7 mM ± 0.5; P < 0.01); [H+] (370 nM ± 13.50 vs. 284 nM ± 13.6; P < 0.05). Average [H+] was similar for CONT vs. INT. We therefore suggest that there is a glycolytic contribution to ATP recovery during the very short rest period (<5 s) of INT and that the greater average power output of CONT did not manifest in greater [H+] and greater glycolytic contribution compared with INT exercise.

scholarly journals Human muscle performance and PCr hydrolysis with varied inspired oxygen fractions: a31P-MRS study

1999 ◽  
Vol 86 (4) ◽  
pp. 1367-1373 ◽  
Author(s):  
Michael C. Hogan ◽  
Russell S. Richardson ◽  
Luke J. Haseler
Keyword(s):  
Plantar Flexion ◽  
Exercise Bout ◽  
Work Rate ◽  
Muscle Performance ◽  
Time To Exhaustion ◽  
Resonance Spectroscopy ◽  
Intracellular Acidosis ◽  
Inspired Oxygen ◽  
Plantar Flexion Exercise ◽  
Text Condition

The purpose of this study was to use31P-magnetic resonance spectroscopy to examine the relationships among muscle PCr hydrolysis, intracellular H+ concentration accumulation, and muscle performance during incremental exercise during the inspiration of gas mixtures containing different fractions of inspired O2([Formula: see text]). We hypothesized that lower [Formula: see text]would result in a greater disruption of intracellular homeostasis at submaximal workloads and thereby initiate an earlier onset of fatigue. Six subjects performed plantar flexion exercise on three separate occasions with the only variable altered for each exercise bout being the [Formula: see text] (either 0.1, 0.21, or 1.00 O2 in balance N2). Work rate was increased (1-W increments starting at 0 W) every 2 min until exhaustion. Time to exhaustion (and thereby workload achieved) was significantly ( P < 0.05) greater as[Formula: see text] was increased. Muscle phosphocreatine (PCr) concentration, Pi concentration, and pH at exhaustion were not significantly different among the three[Formula: see text] conditions. However, muscle PCr concentration and pH were significantly reduced at identical submaximal workloads (and thereby equivalent rates of respiration) above 4–5 W during the lowest[Formula: see text] condition compared with the other two [Formula: see text]conditions. These results demonstrate that exhaustion during all[Formula: see text] occurred when a particular intracellular environment was acheived and suggest that during the lowest [Formula: see text]condition, the greater PCr hydrolysis and intracellular acidosis at submaximal workloads may have contributed to the significantly earlier time to exhaustion.

scholarly journals Normalized metabolic stress for31P-MR spectroscopy studies of human skeletal muscle: MVC vs. muscle volume

1997 ◽  
Vol 83 (3) ◽  
pp. 875-883 ◽  
Author(s):  
M. D. Fowler ◽  
T. W. Ryschon ◽  
R. E. Wysong ◽  
C. A. Combs ◽  
R. S. Balaban
Keyword(s):  
Skeletal Muscle ◽  
Power Output ◽  
Mr Spectroscopy ◽  
Human Skeletal Muscle ◽  
Plantar Flexion ◽  
Metabolic Stress ◽  
Muscle Volume ◽  
Resonance Spectroscopy ◽  
Plantar Flexor ◽  
Spectroscopy Studies

Fowler, M. D., T. W. Ryschon, R. E. Wysong, C. A. Combs, and R. S. Balaban. Normalized metabolic stress for31P-MR spectroscopy studies of human skeletal muscle: MVC vs. muscle volume. J. Appl. Physiol. 83(3): 875–883, 1997.—A critical requirement of submaximal exercise tests is the comparability of workload and associated metabolic stress between subjects. In this study, 31P-magnetic resonance spectroscopy was used to estimate metabolic strain in the soleus muscle during dynamic, submaximal plantar flexion in which target torque was 10 and 15% of a maximal voluntary contraction (MVC). In 10 healthy, normally active adults, (PCr + Pi)/PCr, where PCr is phosphocreatine, was highly correlated with power output normalized to the volume of muscle in the plantar flexor compartment ( r = 0.89, P < 0.001). The same variable was also correlated, although less strongly ( r = 0.78, P < 0.001), with power normalized to plantar flexor cross-sectional area. These findings suggest that comparable levels of metabolic strain can be obtained in subjects of different size when the power output, or stress, for dynamic plantar flexion is selected as a function of plantar flexor muscle volume. In contrast, selecting power output as a function of MVC resulted in a positive linear relationship between (PCr + Pi)/PCr and the torque produced, indicating that metabolic strain was increasing rather than achieving constancy as a function of MVC. These findings provide new insight into the design of dynamic muscle contraction protocols aimed at detecting metabolic differences between subjects of different body size but having similar blood flow capacity and mitochondrial volume per unit of muscle.

Metabolic Adaptations to Endurance Training in Older Individuals

1993 ◽  
Vol 18 (4) ◽  
pp. 366-378 ◽  
Author(s):  
Gregory D. Marsh ◽  
Donald H. Paterson ◽  
R. Terry Thompson ◽  
Po Kee Cheung ◽  
J. Malcolm O. Arnold ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Blood Flow ◽  
Magnetic Resonance ◽  
Exercise Training ◽  
Magnetic Resonance Spectroscopy ◽  
Power Output ◽  
Resonance Spectroscopy ◽  
Older Individuals ◽  
Intracellular Acidosis ◽  
Progressive Exercise

The purpose of this study was to describe the effects of moderate intensity exercise training on the muscle energy utilization, blood flow, and exercise performance of four sedentary older individuals (58 ± 4 yrs). Subjects trained the dominant forearm each day for 12 weeks. The nondominant arm was not trained and served as a within-subject control. 31P nuclear magnetic resonance spectroscopy (31P NMRS) was used to identify the power output in watts (W) at the onset, or threshold, of intracellular acidosis (IT) in the exercising muscle during progressive exercise tests to fatigue. After 6 weeks of training, power output at the IT increased by 14% (p < 0.05) in the dominant arm; however, an additional 6 weeks of the same exercise program failed to produce a further increase in IT power. IT power of the nondominant forearm was not changed. In the dominant forearm, endurance time for a submaximal wrist flexion test was increased 34% and 58% at 6 and 12 weeks, respectively. Maximal voluntary strength was not affected by training, nor was resting or exercising blood flow. The training program delayed the onset of intracellular acidosis during progressive exercise and increased the capacity for submaximal work. These effects did not appear to depend on an increase in muscle blood flow. Key words: 31P nuclear magnetic resonance spectroscopy, muscle metabolism, exercise training

scholarly journals Use of Intravenous Sodium Bicarbonate in Neonatal Intensive Care Units in Italy: A Nationwide Survey

2020 ◽  
Author(s):  
Luca Massenzi ◽  
Roberto Aufieri ◽  
Silvia Donno ◽  
Rocco Agostino ◽  
Andrea Dotta
Keyword(s):  
Sodium Bicarbonate ◽  
Neonatal Intensive Care ◽  
Current Knowledge ◽  
Nationwide Survey ◽  
Intracellular Acidosis ◽  
Acid Base Balance ◽  
Metabolic Disturbances ◽  
Attitudes And Practices ◽  
Base Balance ◽  
Intravenous Sodium

Abstract Background Metabolic Acidosis (MA) is a disturbance of the acid-base balance that can occur in preterm and critically ill term neonates due to different etiologies. Intravenous sodium bicarbonate (SB) has been traditionally used to correct such unbalance, despite the lack of evidence about its safety and efficacy. In literature, reported undesirable effects of treatment with SB in neonates include worsening of intracellular acidosis, impairment of myocardial function, cerebral blood flow fluctuations and intracranial hemorrhage. A national survey was conducted by the Neonatal Pharmacotherapy Study Group of the Italian Society of Neonatology with the aim to assess and describe attitudes and practices concerning the use of SB, particularly for the treatment of MA in Italian NICUs. Methods A questionnaire regarding treatment of MA and SB prescription habits was sent to the directors of 120 Italian NICUs from June 2017 to March 2018. Results The survey response rate was 97.5% (117/120 centers). Findings showed that in 55% of the surveyed NICUs (64/117 units) it is common practice to correct MA with intravenous SB. On the other hand, the remaining 45% of the units try to solve the metabolic disturbances adopting different approaches (improving perfusion, adjusting ventilation parameters or increasing blood volume). Moreover, to prevent the occurrence of MA, 37.6% of the NICUs (44/117) include buffer salts (lactate, acetate or both) in parenteral nutrition prescriptions. SB is also used as a treatment for other conditions, mainly pathologies with bicarbonate loss and tubular acidosis (respectively in 53.8% and 32.5% of the NICUs). Conclusion This survey showed how SB is a commonly used treatment for MA in more than half of Italian NICUs, with indications and prescription criteria that significantly vary across centers. Based on current knowledge, it is reasonable to suggest that the management of neonatal MA should be firstly directed to identify the underlying disorders. Thus, the use of SB should be reserved only for selected cases, also considering the severity of SB adverse effects and the lack of evidence about its efficacy. Guidance for the management of MA is required to harmonize practices and reduce the use of potentially inappropriate and unsafe treatments.

The Effect of Superoxygenated Water on Blood Gases, Lactate, and Aerobic Cycling Performance

2007 ◽  
Vol 2 (4) ◽  
pp. 377-385 ◽  
Author(s):  
Lars R. McNaughton ◽  
Steve Kenney ◽  
Jason Siegler ◽  
Adrian W. Midgley ◽  
Ric J. Lovell ◽  
...  
Keyword(s):  
Exercise Test ◽  
Power Output ◽  
Average Power ◽  
Rest Period ◽  
Cycling Performance ◽  
Exercise Tests ◽  
Double Blind ◽  
Maximal Power Output ◽  
Physiological Variables ◽  
Average Power Output

Context:Recently, superoxygenated-water beverages have emerged as a new purported ergogenic substance.Purpose:This study aimed to determine the effects of superoxygenated water on submaximal endurance performance.Methods:Eleven active male subjects, VO2max 52.6 ± 4.8 mL · kg−1 · min−1, height 180.0 ± 2.0 cm, weight 76.0 ± 7.0 kg, age 24 ± 1.0 y (mean ± SD), completed a 45-min cycle-ergometry exercise test at 70% of their previously predicted maximal power output with a 10-min rest period, followed by a 15-min time trial (TT). Thirty minutes before the exercise test subjects consumed 15 mL of either superoxygenated water (E) or placebo (P; water mixed with low-chlorine solution). Subjects then completed the test again a week later for the other condition (double-blind, randomized). The physiological variables measured during exercise were VO2, VCO2, respiratory-exchange ratio (RER), VE, PO2, PCO2, blood lactate (bLa–), and heart rate (HR). Mean distance covered and the average power output for the 15-min TT were also measured as performance indicators.Results:There were no significant differences in VO2, VCO2, RER, VE, bLa−, PO2, and HR (P > .05) during the exercise tests. Neither were there any significant improvements in the total distance covered (P 9.01 ± 0.74 km vs E 8.96 ± 0.68 km, P > .05) or the average power output (P 186.7 ± 35.8 W vs E 179.0 ± 25.9 W, P > .05) during the 15-min TT.Conclusion:Based on these results the authors conclude that consuming 15 mL of superoxygenated water does not enhance submaximal or maximal TT cycling performance.

scholarly journals Cerebral 31P Magnetic Resonance Spectroscopy and Systemic Acid-Base Balance during Hypoxia in Fetal Sheep

2003 ◽  
Vol 54 (5) ◽  
pp. 747-752 ◽  
Author(s):  
Anne-Marie van Cappellen van Walsum ◽  
Mark Rijpkema ◽  
Arend Heerschap ◽  
Berend Oeseburg ◽  
Jan G Nijhuis ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Acid Base Balance ◽  
Acid Base ◽  
Fetal Sheep ◽  
31P Magnetic Resonance Spectroscopy ◽  
Base Balance

The effect of acid–base balance on fatigue of skeletal muscle

1985 ◽  
Vol 63 (5) ◽  
pp. 403-416 ◽  
Author(s):  
G. W. Mainwood ◽  
J. M. Renaud
Keyword(s):  
Direct Effect ◽  
Isometric Force ◽  
Intracellular Acidosis ◽  
Acid Base Balance ◽  
Slow Recovery ◽  
Tension Development ◽  
Change Of State ◽  
Base Balance ◽  
Proton Load ◽  
External Ph

H+ ions are generated rapidly when muscles are maximally activated. This results in an intracellular proton load. Typical proton loads in active muscles reach a level of 20–25 μmol∙g−1, resulting in a fall in intracellular pH of 0.3–0.5 units in mammalian muscle and 0.6–0.8 units in frog muscle. In isolated frog muscles stimulated to fatigue a proton load of this magnitude is developed, and at the same time maximum isometric force is suppressed by 70–80%. Proton loss is slowed when external pH is kept low. This is paralleled by a slow recovery of contractile tension and seems to support the idea that suppression results from intracellular acidosis. Nonfatigued muscles subjected to similar intracellular proton loads by high CO2 levels show a suppression of maximal tension by only about 30%. This indicates that only a part of the suppression during fatigue is normally due to the direct effect of intracellular acidosis. Further evidence for a component of fatigue that is not due to intracellular acidosis is provided by the fact that some muscle preparations (rat diaphragm) can be fatigued with very little lactate accumulation and very low proton loads. Even under these conditions, a low external pH (6.2) can slow recovery of tension development 10-fold compared with normal pH (7.4). We must conclude that there are at least two components to fatigue. One, due to a direct effect of intracellular acidosis, acting directly on the myofibrils, accounts for a part of the suppression of contractile force. A second, which in many cases may be the major component, is not dependent on intracellular acidosis. This component seems to be due to a change of state in one or more of the steps of the excitation–contraction coupling process. Reversal of this state is sensitive to external pH which suggests that this component is accessible from the outside of the cell.

scholarly journals Use of intravenous sodium bicarbonate in neonatal intensive care units in Italy: a nationwide survey

2021 ◽  
Vol 47 (1) ◽  
Author(s):  
Luca Massenzi ◽  
◽  
Roberto Aufieri ◽  
Silvia Donno ◽  
Rocco Agostino ◽  
...  
Keyword(s):  
Sodium Bicarbonate ◽  
Neonatal Intensive Care ◽  
Current Knowledge ◽  
Nationwide Survey ◽  
Intracellular Acidosis ◽  
Acid Base Balance ◽  
Metabolic Disturbances ◽  
Attitudes And Practices ◽  
Base Balance ◽  
Intravenous Sodium

Abstract Background Metabolic Acidosis (MA) is a disturbance of the acid-base balance that can occur in preterm and critically ill term neonates due to different etiologies. Intravenous sodium bicarbonate (SB) has been traditionally used to correct such unbalance, despite the lack of evidence about its safety and efficacy. In literature, reported undesirable effects of treatment with SB in neonates include worsening of intracellular acidosis, impairment of myocardial function, cerebral blood flow fluctuations and intracranial hemorrhage. A national survey was conducted by the Neonatal Pharmacotherapy Study Group of the Italian Society of Neonatology with the aim to assess and describe attitudes and practices concerning the use of SB, particularly for the treatment of MA in Italian NICUs. Methods A questionnaire regarding treatment of MA and SB prescription habits was sent to the directors of 120 Italian NICUs from June 2017 to March 2018. Results The survey response rate was 97.5% (117/120 centers). Findings showed that in 55% of the surveyed NICUs (64/117 units) it is common practice to correct MA with intravenous SB. On the other hand, the remaining 45% of the units try to solve the metabolic disturbances adopting different approaches (improving perfusion, adjusting ventilation parameters or increasing blood volume). Moreover, to prevent the occurrence of MA, 37.6% of the NICUs (44/117) include buffer salts (lactate, acetate or both) in parenteral nutrition prescriptions. SB is also used as a treatment for other conditions, mainly pathologies with bicarbonate loss and tubular acidosis (respectively in 53.8 and 32.5% of the NICUs). Conclusion This survey showed how SB is a commonly used treatment for MA in more than half of Italian NICUs, with indications and prescription criteria that significantly vary across centers. Based on current knowledge, it is reasonable to suggest that the management of neonatal MA should be firstly directed to identify the underlying disorders. Thus, the use of SB should be reserved only for selected cases, also considering the severity of SB adverse effects and the lack of evidence about its efficacy. Guidance for the management of MA is required to harmonize practices and reduce the use of potentially inappropriate and unsafe treatments.

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