Muscle IMP accumulation during fatiguing submaximal exercise in endurance trained and untrained men

1999 ◽  
Vol 277 (1) ◽  
pp. R295-R300 ◽  
Author(s):  
Jacinta Baldwin ◽  
Rodney J. Snow ◽  
Michael F. Carey ◽  
Mark A. Febbraio
Keyword(s):  
Oxygen Uptake ◽  
Glycogen Content ◽  
Supply And Demand ◽  
Muscle Metabolism ◽  
Peak Oxygen Uptake ◽  
Submaximal Exercise ◽  
Work Rate ◽  
Time To Exhaustion ◽  
Training Status ◽  
Atp Supply

To examine the effect of training status on muscle metabolism during exercise, seven endurance-trained [peak oxygen uptake (V˙o2 peak) = 65.8 ± 2.4 ml ⋅ kg−1⋅ min−1] and six untrained (V˙o2 peak= 46.2 ± 1.9 ml ⋅ kg−1⋅ min−1) men cycled to fatigue at a work rate calculated to require 70%V˙o2 peak. Time to exhaustion was 36% longer ( P < 0.01) in trained (TR) compared with untrained (UT) men (148 ± 11 vs. 95 ± 8 min). Although intramuscular glycogen content was reduced ( P < 0.05) in both TR and UT at fatigue, IMP, a marker of a mismatch between ATP supply and demand, was only elevated ( P < 0.01) in UT muscle at fatigue and was approximately fourfold higher at this point in UT compared with TR. These data demonstrate that fatiguing submaximal exercise was associated with a similar low level of intramuscular glycogen in both TR and UT men, but a mismatch between ATP supply and demand only occurred in UT individuals.

scholarly journals Physiological responses and cycle characteristics during double-poling versus diagonal-stride roller-skiing in junior cross-country skiers

2021 ◽  
Author(s):  
Erik P. Andersson ◽  
Irina Hämberg ◽  
Paulo Cesar Do Nascimento Salvador ◽  
Kerry McGawley
Keyword(s):  
Oxygen Uptake ◽  
Perceived Exertion ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Peak Oxygen Uptake ◽  
Submaximal Exercise ◽  
Rating Of Perceived Exertion ◽  
Time To Exhaustion ◽  
Double Poling ◽  
Cross Country

Abstract Purpose This study aimed to compare physiological factors and cycle characteristics during cross-country (XC) roller-skiing at matched inclines and speeds using the double-poling (DP) and diagonal-stride (DS) sub-techniques in junior female and male XC skiers. Methods Twenty-three well-trained junior XC skiers (11 women, 12 men; age 18.2 ± 1.2 yr.) completed two treadmill roller-skiing tests in a randomized order using either DP or DS. The exercise protocols were identical and included a 5 min warm-up, 4 × 5 min submaximal stages, and an incremental test to exhaustion, all performed at a 5° incline. Results No significant three-way interactions were observed between sex, submaximal exercise intensity, and sub-technique. For the pooled sample, higher values were observed for DP versus DS during submaximal exercise for the mean oxygen uptake kinetics response time (33%), energy cost (18%), heart rate (HR) (9%), blood lactate concentration (5.1 versus 2.1 mmol·L−1), rating of perceived exertion (12%), and cycle rate (25%), while cycle length was lower (19%) (all P < 0.001). During the time-to-exhaustion (TTE) test, peak oxygen uptake ($$\dot{V}$$ V ˙ O2peak), peak HR, and peak oxygen pulse were 8%, 2%, and 6% lower, respectively, for DP than DS, with a 29% shorter TTE during DP (pooled data, all P < 0.001). Conclusion In well-trained junior XC skiers, DP was found to exert a greater physiological load than DS during uphill XC roller-skiing at submaximal intensities. During the TTE test, both female and male athletes were able to ski for longer and reached markedly higher $$\dot{V}$$ V ˙ O2peak values when using DS compared to DP.

Effect of carbohydrate ingestion on glucose kinetics and muscle metabolism during intense endurance exercise

2000 ◽  
Vol 89 (5) ◽  
pp. 1690-1698 ◽  
Author(s):  
Glenn K. McConell ◽  
Benedict J. Canny ◽  
Marcus C. Daddo ◽  
Marcus J. Nance ◽  
Rodney J. Snow
Keyword(s):  
Oxygen Uptake ◽  
Muscle Metabolism ◽  
Glucose Production ◽  
Peripheral Circulation ◽  
Peak Oxygen Uptake ◽  
Endogenous Glucose Production ◽  
Time To Exhaustion ◽  
Glucose Kinetics ◽  
Carbohydrate Ingestion ◽  
Endogenous Glucose

There has been recent interest in the potential performance and metabolic effects of carbohydrate ingestion during exercise lasting ∼1 h. In this study, 13 well-trained men ingested in randomized order either a 6% glucose solution (CHO trial) or a placebo (Con trial) during exercise to exhaustion at 83 ± 1% peak oxygen uptake. In six subjects, vastus lateralis muscle was sampled at rest, at 32 min, and at exhaustion, and in six subjects, glucose kinetics was determined by infusion of [6,6-2H]glucose in both trials and ingestion of [6-3H]glucose in the CHO trial. Of the 84 g of glucose ingested during exercise in the CHO trial, only 22 g appeared in the peripheral circulation. This resulted in a small (12 g) but significant ( P < 0.05) increase in glucose uptake without influencing carbohydrate oxidation, muscle glycogen use, or time to exhaustion (CHO: 68.1 ± 4.1 min; Con: 69.6 ± 5.5 min). Decreases in muscle phosphocreatine content and increases in muscle inosine monophosphate and lactate content during exercise were similar in the two trials. Although endogenous glucose production during exercise was partially suppressed in the CHO trial, it remained significantly above preexercise levels throughout exercise. In conclusion, only 26% of the ingested glucose appeared in the peripheral circulation. Glucose ingestion increased glucose uptake and partially reduced endogenous glucose production but had no effect on carbohydrate oxidation, muscle metabolism, or time to exhaustion during exercise at 83% peak oxygen uptake.

Metabolic Profiles of the 30-15 Intermittent Fitness Test and the Corresponding Continuous Version in Team-Sport Athletes—Elucidating the Role of Inter-Effort Recovery

2020 ◽  
pp. 1-6
Author(s):  
Sebastian Kaufmann ◽  
Ralph Beneke ◽  
Richard Latzel ◽  
Hanna Pfister ◽  
Olaf Hoos
Keyword(s):  
Oxygen Uptake ◽  
State Level ◽  
Peak Oxygen Uptake ◽  
Metabolic Energy ◽  
Time To Exhaustion ◽  
Metabolic Profiles ◽  
Energy Contribution ◽  
Continuous Version ◽  
Fitness Test

Purpose: To elucidate the role of inter-effort recovery in shuttle running by comparing the metabolic profiles of the 30-15 Intermittent Fitness Test (30-15IFT) and the corresponding continuous version (30-15IFT-CONT). Methods: Sixteen state-level handball players (age = 23 [3] y, height = 185 [7] cm, weight = 85 [14] kg) completed the 30-15IFT and 30-15IFT-CONT, and speed at the last completed stage (in kilometers per hour) and time to exhaustion (in seconds) were assessed. Furthermore, oxygen uptake (in milliliters per kilogram per minute) and blood lactate were obtained preexercise, during exercise, and until 15 minutes postexercise. Metabolic energy (in kilojoules), metabolic power (in Watts per kilogram), and relative (in percentage) energy contribution of the aerobic (WAER, WAERint), anaerobic lactic (WBLC, WBLCint), and anaerobic alactic (WPCr, WPCrint) systems were calculated by PCr-La-O2 method for 30-15IFT-CONT and 30-15IFT. Results: No difference in peak oxygen uptake was found between 30-15IFT and 30-15IFT-CONT (60.6 [6.6] vs 60.5 [5.1] mL·kg−1·min−1, P = .165, d = 0.20), whereas speed at the last completed stage was higher in 30-15IFT (18.3 [1.4] vs 16.1 [1.0] km·h−1, P < .001, d = 1.17). Metabolic energy was also higher in 30-15IFT (1224.2 [269.6] vs 772.8 [63.1] kJ, P < .001, d = 5.60), and metabolic profiles differed substantially for aerobic (30-15IFT = 67.2 [5.2] vs 30-15IFT-CONT = 85.2% [2.5%], P < .001, d = −4.01), anaerobic lactic (30-15IFT = 4.4 [1.4] vs 30-15IFT-CONT = 6.2% [1.8%], P < .001, d = −1.04), and anaerobic alactic (30-15IFT = 28.4 [4.7] vs 30-15IFT-CONT = 8.6% [2.1%], P < .001, d = 5.43) components. Conclusions: Both 30-15IFT and 30-15IFT-CONT are mainly fueled by aerobic energy, but their metabolic profiles differ substantially in both aerobic and anaerobic alactic energy contribution. Due to the presence of inter-effort recovery, intermittent shuttle runs rely to a higher extent on anaerobic alactic energy and a fast, aerobic replenishment of PCr during the short breaks between shuttles.

Effect of a precooling maneuver on body temperature and exercise performance

1981 ◽  
Vol 50 (4) ◽  
pp. 772-778 ◽  
Author(s):  
V. Schmidt ◽  
K. Bruck
Keyword(s):  
Heart Rate ◽  
Body Temperature ◽  
Peak Oxygen Uptake ◽  
Work Rate ◽  
Time To Exhaustion ◽  
Total Work ◽  
Mean Body Temperature ◽  
Deep Body Temperature ◽  
Sweat Secretion ◽  
Maximum Work

Twelve subjects exercised to exhaustion at an ambient temperature of 18 degrees C on a bicycle ergometer with the load being stepwise increased. On one day, exercise was preceded by a precooling maneuver. In the precooling tests, deep body temperature attained values of about 1 degree C lower than in the control tests. There was no indication of metabolic cold defense reactions being evoked throughout the exercise period. In the precooling tests, heart rate was significantly lower than in the controls, but the mean maximum work rate, peak oxygen uptake (VO2), time to exhaustion, and total work were not reduced, i.e., work rate and VO2 were increased for a given heart rate. In the three subjects with the lowest maximum work rates, total work and exhaustion time and, in two cases, maximum work rate were increased after precooling. The onset of sweating occurred at higher work rates but at lower core, mean skin, and mean body temperature after precooling. However, the accumulated sweat secretion was considerably smaller after precooling, indicating less thermoregulatory effort.

scholarly journals Predicting Peak Oxygen Uptake From Submaximal Exercise After Spinal Cord Injury

2016 ◽  
Vol 48 ◽  
pp. 343
Author(s):  
Julia O. Totosy de Zepetnek ◽  
Jason S. Au ◽  
Adrienne L. Hol ◽  
Janice J. Eng ◽  
Maureen J. MacDonald
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Oxygen Uptake ◽  
Peak Oxygen Uptake ◽  
Submaximal Exercise ◽  
Cord Injury

Gender differences in substrate utilization during submaximal exercise in endurance-trained subjects

2002 ◽  
Vol 282 (2) ◽  
pp. E435-E447 ◽  
Author(s):  
Carsten Roepstorff ◽  
Charlotte H. Steffensen ◽  
Marianne Madsen ◽  
Bente Stallknecht ◽  
Inge-Lis Kanstrup ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Energy Content ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Substrate Utilization ◽  
Peak Oxygen Uptake ◽  
Submaximal Exercise ◽  
Activity Level ◽  
Relative Contribution ◽  
History Of

Substrate utilization across the leg during 90 min of bicycle exercise at 58% of peak oxygen uptake (V˙o 2 peak) was studied in seven endurance-trained males and seven endurance-trained, eumenorrheic females by applying arteriovenous catheterization, stable isotopes, and muscle biopsies. The female and male groups were matched according toV˙o 2 peak per kilogram of lean body mass, physical activity level, and training history of the subjects. All subjects consumed the same diet, well controlled in terms of nutrient composition as well as energy content, for 8 days preceding the experiment, and all females were tested in the midfollicular phase of the menstrual cycle. During exercise, respiratory exchange ratio (RER) and leg respiratory quotient (RQ) were similar in females and males. Myocellular triacylglycerol (TG) degradation was negligible in males but amounted to 12.4 ± 3.2 mmol/kg dry wt in females and corresponded to 25.0 ± 6.0 and 5.0 ± 7.3% of total oxygen uptake in females and males, respectively ( P < 0.05). Utilization of plasma fatty acids (12.0 ± 2.5 and 9.6 ± 1.5%), blood glucose (13.6 ± 1.5 and 14.3 ± 1.5%), and glycogen (48.5 ± 4.9 and 42.8 ± 2.1%) were similar in females and males. Thus, in females, measured substrate oxidation accounted for 99% of the leg oxygen uptake, whereas in males 28% of leg oxygen uptake was unaccounted for in terms of measured oxidized lipid substrates. These findings may indicate that males utilized additional lipid sources, presumably very low density lipoprotein-TG or TG located between muscle fibers. On the basis of RER and leg RQ, it is concluded that no gender difference existed in the relative contribution from carbohydrate and lipids to the oxidative metabolism across the leg during submaximal exercise at the same relative workload. However, an effect of gender appears to occur in the utilization of the different lipid sources.

Voluntary fluid intake, hydration status, and aerobic performance of adolescent athletes in the heat

2010 ◽  
Vol 35 (6) ◽  
pp. 834-841 ◽  
Author(s):  
Boguslaw Wilk ◽  
Brian W. Timmons ◽  
Oded Bar-Or
Keyword(s):  
Body Weight ◽  
Oxygen Uptake ◽  
Exercise Performance ◽  
Fluid Intake ◽  
Tap Water ◽  
Peak Oxygen Uptake ◽  
Adolescent Male ◽  
Aerobic Performance ◽  
Hydration Status ◽  
Time To Exhaustion

We determined whether beverage flavoring and composition would stimulate voluntary drink intake, prevent dehydration, and maintain exercise performance in heat-acclimated adolescent males running in the heat. Eight adolescent (age, 13.7 ± 1.1 years) runners (peak oxygen uptake, 59.5 ± 4.0 mL·kg–1·min–1) underwent at least four 80-min exercise heat-acclimation sessions before completing 3 experimental sessions. All sessions were performed at 30 °C and 60%–65% relative humidity. Each experimental session consisted of five 15-min treadmill runs at a speed eliciting 65% peak oxygen uptake, with a 5 min rest prior to each run. Ten minutes after the final run, a time to exhaustion test was performed at a speed eliciting 90% peak oxygen uptake. Counterbalanced experimental sessions were identical, except for fluid intake, which consisted of tap water (W), flavored water (FW), and FW with 6% carbohydrate and 18 mmol·L–1 NaCl (CNa) consumed ad libitum. Fluid intake and body weight were monitored to calculate dehydration. Voluntary fluid intake was similar to fluid losses in W (1032 ± 130 vs. 1340 ± 246 g), FW (1086 ± 86 vs. 1451 ± 253 g), and CNa (1259 ± 119 vs. 1358 ± 234 g). As a result, significant dehydration was avoided in all trials (–0.45% ± 0.68% body weight in W, –0.66% ± 0.50% body weight in FW, and –0.13% ± 0.71% body weight in CNa). Core temperature increased by ~1 °C during exercise, but was not different between trials. Time to exhaustion was not different between trials and averaged 8.8 ± 1.7 min. Under exercise conditions more closely reflecting real-life situations, heat-acclimatized adolescent male runners can appropriately gauge fluid intake regardless of the type of beverage made available, resulting in consistency in exercise performance.

Regulation of glucose production during exercise at 80% of VO2peak in untrained humans

1997 ◽  
Vol 273 (2) ◽  
pp. E348-E354 ◽  
Author(s):  
A. R. Coggan ◽  
C. A. Raguso ◽  
A. Gastaldelli ◽  
B. D. Williams ◽  
R. R. Wolfe
Keyword(s):  
Oxygen Uptake ◽  
Continuous Infusion ◽  
Glucose Production ◽  
Glucagon Secretion ◽  
Peak Oxygen Uptake ◽  
Submaximal Exercise ◽  
Intense Exercise ◽  
Glucose Kinetics ◽  
Insulin And Glucagon Secretion ◽  
Glucagon Concentration

To determine whether alterations in insulin and/or glucagon secretion play an important role in stimulating glucose production (Ra) during intense but submaximal exercise, we studied six untrained subjects during 30 min of cycling at 80% of peak oxygen uptake on two occasions: once under control conditions and once when alterations in insulin and glucagon secretion were prevented with the use of the pancreatic islet clamp technique. In the latter experiments, glucose was infused during exercise to match glycemia with control levels. Glucose kinetics were measured in both trials using a primed, continuous infusion of [6,6-2H]glucose. In the control trial, glucose Ra rose from 11.9 +/- 0.8 mumol.min-1.kg-1 at rest to 42.5 +/- 4.3 mumol.min-1.kg-1 by the end of exercise. A similar increment was observed in the islet clamp experiments, with endogenous Ra peaking at 37.2 +/- 7.9 mumol.min-1.kg-1. This was true even through glucagon concentration did not change from basal and insulin concentration actually rose (the latter apparently due to a decrease in insulin clearance during intense exercise). Thus neither decrements in insulin or increments in glucagon are apparently required to stimulate glucose Ra under the present conditions. Because epinephrine levels rose only slightly, it appears that either neurally released norepinephrine or some other, as yet unidentified, factor is responsible for stimulating glucose Ra during intense but submaximal exercise.

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