Muscle ATP turnover rate during isometric contraction in humans

1986 ◽  
Vol 60 (6) ◽  
pp. 1839-1842 ◽  
Author(s):  
A. Katz ◽  
K. Sahlin ◽  
J. Henriksson
Keyword(s):  
Isometric Contraction ◽  
Turnover Rate ◽  
Knee Extensor ◽  
High Energy ◽  
High Energy Phosphates ◽  
Atp Turnover ◽  
Contraction Duration ◽  
Extensor Muscles ◽  
Before And After ◽  
Fast Twitch

ATP turnover and glycolytic rates during isometric contraction in humans have been investigated. Subjects contracted the knee extensor muscles at two-thirds maximal voluntary force to fatigue (mean +/- SE, 53 +/- 4 s). Biopsies were obtained before and after exercise and analyzed for high-energy phosphates and glycogenolytic-glycolytic intermediates. Total ATP turnover was 190 +/- 7 mmol/kg dry muscle, whereas the average turnover rate was 3.7 +/- 0.2 mmol . kg dry muscle-1 . S-1. The average ATP turnover rate was positively correlated with the percentage of fast-twitch fibers in the postexercise biopsy (r = 0.71; P less than 0.05) and negatively correlated with contraction duration to fatigue (r = -0.88; P less than 0.05). At fatigue, phosphocreatine ranged from 1 to 11 mmol/kg dry muscle (86–99% depletion of value at rest), whereas lactate ranged from 59 to 101. The mean glycolytic rate was 0.83 +/- 0.05 mmol . kg dry muscle-1 . S-1 and was positively correlated with the rate of glucose 6-phosphate accumulation (r = 0.83; P less than 0.05). It is concluded that a major determinant of the ATP turnover rate is the muscle fiber composition, which is probably explained by a higher turnover rate in fast-twitch fibers; fatigue is more closely related to a low phosphocreatine content than to a high lactate content; and the increase in prephosphofructokinase intermediates is important for stimulating glycolysis during contraction.

Epinephrine inhibits insulin-mediated glycogenesis but enhances glycolysis in human skeletal muscle

1991 ◽  
Vol 260 (3) ◽  
pp. E430-E435 ◽  
Author(s):  
I. Raz ◽  
A. Katz ◽  
M. K. Spencer
Keyword(s):  
Glycogen Synthase ◽  
Glucose Production ◽  
High Energy ◽  
Endogenous Glucose Production ◽  
Fat Free Mass ◽  
Glucose Disposal ◽  
High Energy Phosphates ◽  
Before And After ◽  
Glucose Tolerant ◽  
Femoris Muscle

The effect of epinephrine (E) infusion on insulin-mediated glucose metabolism in humans has been studied. Eight glucose-tolerant men were studied on two separate occasions: 1) during 120 min of euglycemic hyperinsulinemia (UH, approximately 5 mM; 40 mU.m-2.min-1); and 2) during UH while E was infused (UHE, 0.05 microgram.kg-1.min-1). Biopsies were taken from the quadriceps femoris muscle before and after each clamp. Glucose disposal, correcting for endogenous glucose production, was 36 +/- 3 and 18 +/- 2 (SE) mumol.kg fat-free mass (FFM)-1.min-1 during the last 40 min of UH and UHE, respectively (P less than 0.001). Nonoxidative glucose disposal (presumably glycogenesis) averaged 23.0 +/- 3.0 and 4.0 +/- 1.1 (P less than 0.001), whereas carbohydrate oxidation (which is proportional to glycolysis) averaged 13.1 +/- 1.4 and 15.3 +/- 1.1 mumol.kg FFM-1.min-1 (P less than 0.05) during UH and UHE, respectively. UHE resulted in significantly higher contents of UDP-glucose, hexose monophosphates, postphosphofructokinase intermediates, and glucose 1,6-bisphosphate (G-1,6-P2) in muscle (P less than 0.05-0.001), but there were no significant differences in high-energy phosphates or fructose 2,6-bisphosphate (F-2,6-P2) between treatments. Fractional activities of phosphorylase increased (P less than 0.01), and glycogen synthase decreased (P less than 0.001) during UHE. It is concluded that E inhibits insulin-mediated glycogenesis because of an inactivation of glycogen synthase and an activation of glycogenolysis. E also appears to inhibit insulin-mediated glucose utilization, at least partly, because of an increase in G-6-phosphate (which inhibits hexokinase) and enhances glycolysis by G-1,6-P2-, fructose 6-phosphate-, and F-1,6-P2-mediated activation of PFK.

scholarly journals Noninvasive Monitoring of Training Induced Muscle Adaptation with -MRS: Fibre Type Shifts Correlate with Metabolic Changes

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Eike Hoff ◽  
Lars Brechtel ◽  
Patrick Strube ◽  
Paul Konstanczak ◽  
Gisela Stoltenburg-Didinger ◽  
...  
Keyword(s):  
Fibre Type ◽  
Gastrocnemius Muscle ◽  
Noninvasive Monitoring ◽  
High Energy ◽  
Metabolic Changes ◽  
Resonance Spectroscopy ◽  
High Energy Phosphates ◽  
Type Ii ◽  
Fibre Type Composition ◽  
Fast Twitch

Purpose. To evaluate training induced metabolic changes noninvasively with magnetic resonance spectroscopy (-MRS) for measuring muscle fibre type adaptation.Methods. Eleven volunteers underwent a 24-week training, consisting of speed-strength, endurance, and detraining (each 8 weeks). Prior to and following each training period, needle biopsies and -MRS of the resting gastrocnemius muscle were performed. Fibre type distribution was analyzed histologically and tested for correlation with the ratios of high energy phosphates ([PCr]/[], [PCr]/[βATP] and [PCr + ]/[βATP]). The correlation between the changes of the -MRS parameters during training and the resulting changes in fibre composition were also analysed.Results. We observed an increased type-II-fibre proportion after speed-strength and detraining. After endurance training the percentage of fast-twitch fibres was reduced. The progression of the [PCr]/[]-ratio was similar to that of the fast-twitch fibres during the training. We found a correlation between the type-II-fibre proportion and [PCr]/[] (, ) or [PCr]/[βATP] (, ); the correlations between its changes (delta) and the fibre-shift were significant as well (delta[PCr]/[] , delta[PCr]/[βATP] , ).Conclusion. Shifts in fibre type composition and high energy phosphate metabolite content covary in human gastrocnemius muscle. Therefore -MRS might be a feasible method for noninvasive monitoring of exercise-induced fibre type transformation.

Arm cycling increases short-latency reflex from ankle dorsiflexor afferents to knee extensor muscles

2020 ◽  
Author(s):  
Syusaku SASADA ◽  
Toshiki Tazoe ◽  
Tsuyoshi Nakajima ◽  
Shigeki Omori ◽  
Genki Futatsubashi ◽  
...  
Keyword(s):  
Isometric Contraction ◽  
Knee Extensor ◽  
Short Latency ◽  
Reflex Response ◽  
Heel Strike ◽  
Reflex Modulation ◽  
Arm Cycling ◽  
Extensor Muscles ◽  
Neural Coupling ◽  
Knee Extensor Muscles

Low-intensity electrical stimulation of the common peroneal nerve (CPN) evokes a short latency reflex in the heteronymous knee extensor muscles (referred to as CPN-reflex). The CPN-reflex is facilitated at a heel strike during walking, contributing to body weight support. However, the origin of the CPN-reflex increase during walking remains unclear. We speculate that this increase originates from multiple sources due to a body of evidence suggesting the presence of neural coupling between the arms and legs. Therefore, we investigated the extent to which the CPN-reflex is modulated during rhythmic arm cycling. Twenty-eight subjects sat in an armchair and were asked to perform arm cycling at a moderate cadence using a stationary ergometer while performing isometric contraction of the knee extensors, such that the CPN-reflex was evoked. CPN-reflex was evoked by stimulating the CPN (0.9-2.0 × the motor threshold [MT] in the tibialis anterior muscle) at the level of the neck of the fibula. The CPN-reflex amplitude was measured from the vastus lateralis (VL). The biphasic reflex response in the VL was evoked within 27-45 ms following CPN stimulation. The amplitude of the CPN-reflex increased during arm cycling compared with that before cycling. The modulation of the CPN-reflex during arm cycling was detected only for CPN stimulation intensity around 1.2 × MT. Furthermore, CPN-reflex modulation was not observed during the isometric contraction of the arm or passive arm cycling. Our results suggest the presence of neural coupling between the CPN-reflex pathways and neural systems generating locomotive arm movement.

ATP utilization and provision in fast-twitch skeletal muscle during tetanic contractions

1989 ◽  
Vol 257 (4) ◽  
pp. E595-E605 ◽  
Author(s):  
L. L. Spriet
Keyword(s):  
Average Energy ◽  
High Energy ◽  
Energy Costs ◽  
High Energy Phosphates ◽  
Phosphorylase Activity ◽  
Train Duration ◽  
Fast Twitch Muscle ◽  
Fast Twitch

Rat fast-twitch muscles were tetanically stimulated in situ with an occluded circulation to examine ATP utilization and provision during isometric tension production. Plantaris (PL) and gastrocnemius (G) muscles were stimulated for 60 s in four conditions: A) 1.0-Hz train rate, 200-ms train duration at 80 Hz, B) 1.0 Hz (100 ms, 80 Hz), C) 0.5 Hz (100 ms, 80 Hz), and D) 1.0 Hz (200 ms, 40 Hz). Muscles were sampled pre- and post-stimulation for pH, high-energy phosphates, and glycolytic intermediates. Contributions to total ATP utilization (all muscles and conditions) were 64-67% glycolysis, 24-28% phosphocreatine, and 8-9% endogenous ATP. Glycogenolysis and glycolysis were greatest in white G (WG), 40% lower in red G (RG), and intermediate in PL muscles. Average energy costs in conditions A and D were approximately 0.60 mumol ATP/(N.s). Decreasing the train duration to 100 ms in B and the number of tetani to 30 in C increased energy costs to 0.93 +/- 0.05 and 1.26 +/- 0.07 mumol ATP/(N.s). Despite a lower pH, WG glycogenolytic (phosphorylase) activity was constant during condition A, whereas RG activity decreased in the final 30 contractions. Larger accumulations of Pi and inosine monophosphate may account for the maintained phosphorylase activity. Glycolytic (phosphofructokinase, PFK) activity was highest in WG and associated with higher fructose 6-phosphate concentration, greater depletion of ATP and, in later contractions, a higher NH4+ concentration. During tetanic in situ stimulation of fast-twitch muscle, the H+ profiles of phosphorylase and PFK are extended beyond in vitro predictions via the accumulation of positive modulators. This permits significant anaerobic ATP production via the glycolytic pathway despite increasing [H+]. The findings also suggest that lengthening the duration of tetani, generating lower peak tensions, and prolonging relaxation time all contribute to lower energy costs in fast-twitch muscle.

G-1,6-P2 in human skeletal muscle after isometric contraction

1988 ◽  
Vol 255 (2) ◽  
pp. C145-C148 ◽  
Author(s):  
A. Katz ◽  
A. D. Lee
Keyword(s):  
Skeletal Muscle ◽  
Isometric Contraction ◽  
Knee Extensor ◽  
Side Reactions ◽  
Debranching Enzyme ◽  
Extensor Muscles ◽  
Rate Limiting ◽  
Glycolytic Rate ◽  
Knee Extensor Muscles

The content of glucose 1,6-bisphosphate (G-1,6-P2), an in vitro activator of phosphofructokinase (a rate-limiting enzyme for glycolysis), and the glycolytic rate in skeletal muscle during isometric contraction have been determined. Subjects contracted the knee extensor muscles at two-thirds maximal voluntary force to fatigue. Biopsies from the quadriceps femoris muscle were obtained before and immediately after contraction. G-1,6-P2 increased in all subjects from a mean of 101 +/- 15 (SE) mumol/kg dry wt at rest to 128 +/- 24 at fatigue (P less than 0.05). Muscle glucose did not change significantly, whereas hexosemonophosphates were significantly increased after contraction. The glycogenolytic and glycolytic rate averaged 70.0 +/- 13.8 and 47.3 +/- 6.7 mmol.kg dry wt-1.min-1, respectively, and the glycolytic rate was positively correlated with the accumulation rates of fructose 6-phosphate (F-6-P) (r = 0.95, P less than 0.01) and G-6-P (r = 0.96, P less than 0.01). Phosphocreatine and ATP decreased by 87 and 17%, respectively, whereas ADP increased by 31% after contraction. These data demonstrate that intense, short-term isometric contraction results in an elevation of the muscle content of G-1,6-P2. The increase in G-1,6-P2 could not be accounted for by the side reactions of phosphoglucomutase or phosphofructokinase. It remains to be determined whether the observed increase in G-1,6-P2 is sufficient to account for the high glycolytic rate during intense exercise. The lack of increase in muscle glucose while G-6-P increased (which will inhibit hexokinase) suggests that the debranching enzyme complex was not active during contraction.

Skeletal muscle ammonia production and repeated, intense exercise in humans

1993 ◽  
Vol 71 (7) ◽  
pp. 484-490 ◽  
Author(s):  
T. Graham ◽  
J. Bangsbo ◽  
B. Saltin
Keyword(s):  
Muscle Glycogen ◽  
Intermittent Exercise ◽  
Lactate Production ◽  
Knee Extensor ◽  
Creatine Phosphate ◽  
High Energy ◽  
High Energy Phosphates ◽  
Wet Weight ◽  
Exercise Fatigue ◽  
The Impact

We investigated the impact of repeated, high-intensity exercise on NH3 metabolism using the single-leg knee extensor model. The muscle glycogen level would be lowered by the initial exercise and low glycogen may stimulate NH3 production independent of any other effects of previous exercise. Therefore a high muscle glycogen condition was included in the protocol so that the pre-exercise glycogen concentration would be at least at a normal resting level for the second exercise. The subjects (n = 6) used previous exercise and (or) diet to begin the exercise with either normal (87.0 ± 14.4 mmol/kg wet weight) or high (176.8 ± 22.9 mmol/kg wet weight) glycogen (C and HG, respectively) in the quadriceps. They exercised (Ex1) one leg to exhaustion (140% leg [Formula: see text]), rested 1 h, repeated the exercise (Ex2), and then repeated the protocol with the opposite leg. The exercise durations of Ex1 and Ex2, respectively, for C were 2.82 ± 0.51 and 2.47 ± 0.47 min (p < 0.05) and for HG were 2.92 ± 0.57 and 2.77 ± 0.50 min. The NH3 efflux was reduced (p < 0.05) from Ex1 to Ex2 in both C (516 ± 159 and 250 ± 69 μmol, respectively) and HG (618 ± 233 and 275 ± 124 μmol, respectively). While NH3 efflux was virtually identical between C and HG in both Ex1 and Ex 2, HG consistently had a greater arterial NH3 concentration (p < 0.05). The decreased efflux in Ex2 compared with Ex1 was not due to greater accumulation of muscle NH3. The changes in creatine phosphate and ATP were very similar in all four exercises; however, the reduced NH3 response in Ex2 was associated with less net lactate production and presumably less muscle acidosis.Key words: AMP deaminase, lactate, purine nucleotide cycle, high energy phosphates, intermittent exercise, fatigue, glycogen.

scholarly journals Observation of intramyocellular lipids by means of 1H magnetic resonance spectroscopy

1999 ◽  
Vol 58 (4) ◽  
pp. 841-850 ◽  
Author(s):  
Chris Boesch ◽  
Jacques Décombaz ◽  
Johannes Slotboom ◽  
Roland Kreis
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
High Energy ◽  
Muscle Physiology ◽  
High Temporal Resolution ◽  
Resonance Spectroscopy ◽  
High Energy Phosphates ◽  
Intramyocellular Lipids ◽  
Before And After ◽  
Recovery Protocols

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) are being increasingly used for investigations of human muscle physiology. While MRI reveals the morphology of muscles in great detail (e.g. for the determination of muscle volumes), MRS provides information on the chemical composition of the tissue. Depending on the observed nucleus, MRS allows the monitoring of high-energy phosphates (31P MRS), glycogen (13C MRS), or intramyocellular lipids (1H MRS), to give only a few examples. The observation of intramyocellular lipids (IMCL) by means of 1H MRS is non-invasive and, therefore, can be repeated many times and with a high temporal resolution. MRS has the potential to replace the biopsy for the monitoring of IMCL levels; however, the biopsy still has the advantage that other methods such as those used in molecular biology can be applied to the sample. The present study describes variations in the IMCL levels (expressed in mmol/kg wet weight and ml/100 ml) in three different muscles before and after (0, 1, 2, and 5 d) marathon runs for a well-trained individual who followed two different recovery protocols varying mainly in the diet. It was shown that the repletion of IMCL levels is strongly dependent on the diet post exercise. The monitoring of IMCL levels by means of 1H MRS is extremely promising, but several methodological limitations and pitfalls need to be considered, and these are addressed in the present review.

Force-velocity relations and fiber composition in human knee extensor muscles

1976 ◽  
Vol 40 (1) ◽  
pp. 12-16 ◽  
Author(s):  
A. Thorstensson ◽  
G. Grimby ◽  
J. Karlsson
Keyword(s):  
Skeletal Muscle ◽  
Knee Extensor ◽  
Dynamic Strength ◽  
Peak Torque ◽  
Human Knee ◽  
Isokinetic Contractions ◽  
Extensor Muscles ◽  
Angular Velocities ◽  
Force Velocity ◽  
Fast Twitch

Standardized measurements of dynamic strength of the kneee extensor muscles were performed in 25 healthy male subjects (17–37 yr) by means of isokinetic contractions, i.e., knee extensions with constant angular velocities. Overall variation between double determinations of maximal torque throughout the 90 degrees arc of motion (0 degrees = fully extended leg) averaged 10% for the different constant velocities chosen. At any given angle of the knee the torque produced was higher for isometric than for dynamic contractions. Dynamic torque decreased gradually with increased speed of shortening. Peak dynamic torque was reached at knee angles in the range: 55–66 degrees, with a displacement toward smaller knee angles with higher angular velocities. Correlations were demonstrated between peak torque produced at the highest speed of muscle shortening and percent as well as relative area of fast twitch fibers in the contracting muscle. In addition muscles with a high percentage of fast twitch fibers had the highest maximal contraction speeds. These observations on intact human skeletal muscle are consistent with earlier findings in animal skeletal muscle preparations.

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