Dietary carbohydrate, muscle glycogen, and power output during rowing training

The belief that high-carbohydrate diets enhance training capacity (mean power output) has been extrapolated from studies that have varied dietary carbohydrate over a few days and measured muscle glycogen but did not assess power output during training. We hypothesized that a high-carbohydrate (HI) diet (10 g.kg body mass-1.day-1) would promote greater muscle glycogen content and greater mean power output during training than a moderate-carbohydrate (MOD) diet (5 g.kg body mass-1.day-1) over 4 wk of intense twice-daily rowing training. Dietary protein intake was 2 g.kg body mass-1.day-1, and fat intake was adjusted to maintain body mass. Twelve male and 10 female collegiate rowers were randomly assigned to the treatment groups. Training was 40 min at 70% peak O2 consumption (VO2) (A.M.) and either three 2,500-m time trials to assess power output or interval training at 70-90% peak VO2 (P.M.). Mean daily training was 65 min at 70% peak VO2 and 38 min at greater than or equal to 90% peak VO2. Mean muscle glycogen content increased 65% in the HI group (P less than 0.05) but remained constant at 119 mmol/kg in the MOD group over the 4 wk. Mean power output in time trials increased 10.7 and 1.6% after 4 wk in the HI and MOD groups, respectively (P less than 0.05). We conclude that a diet with 10 g carbohydrate.kg body mass-1.day-1 promotes greater muscle glycogen content and greater power output during training than a diet containing 5 g carbohydrate.kg body mass-1.day-1 over 4 wk of intense twice-daily rowing training.(ABSTRACT TRUNCATED AT 250 WORDS)

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The Effects of Carbohydrate Loading on Muscle Glycogen Content and Cycling Performance

International Journal of Sport Nutrition ◽

10.1123/ijsn.5.1.25 ◽

1995 ◽

Vol 5 (1) ◽

pp. 25-36 ◽

Cited By ~ 39

Author(s):

Laurie H.G. Rauch ◽

Ian Rodger ◽

Gary R. Wilson ◽

Judy D. Belonje ◽

Steven C. Dennis ◽

...

Keyword(s):

Body Mass ◽

Muscle Glycogen ◽

Power Output ◽

Glycogen Content ◽

Potato Starch ◽

Random Order ◽

Cycling Performance ◽

Muscle Glycogen Content ◽

Glycogen Utilization ◽

And Performance

This study compared the effects of supplementing the normal diets of 8 endurance-trained cyclists with additional carbohydrate (CHO), in the form of potato starch, for 3 days on muscle glycogen utilization and performance during a 3-hr cycle ride. On two occasions prior to the trial, the subjects ingested in random order either their normal CHO intake of 6.15 ± 0.23 g/kg body mass/day or a high-CHO diet of 10.52 ± 0.57 g/kg body mass/day. The trial consisted of 2 hr of cycling at ~75% ofwith five 60-s sprints at 100%at 20-min intervals, followed by a 60-min performance ride. Increasing CHO intake by 72 ± 9% for 3 days prior to the trial elevated preexercise muscle glycogen contents, improved power output, and extended the distance covered in 1 hr. Muscle glycogen contents were similar at the end of the 3-hr trial, indicating a greater utilization of glycogen when subjects were CHO loaded, which may have been responsible for their improved cycling performance.

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Carbohydrate loading failed to improve 100-km cycling performance in a placebo-controlled trial

Journal of Applied Physiology ◽

10.1152/jappl.2000.88.4.1284 ◽

2000 ◽

Vol 88 (4) ◽

pp. 1284-1290 ◽

Cited By ~ 42

Author(s):

Louise M. Burke ◽

John A. Hawley ◽

Elske J. Schabort ◽

Alan St Clair Gibson ◽

Iñigo Mujika ◽

...

Keyword(s):

Body Mass ◽

Muscle Glycogen ◽

Blood Glucose Concentration ◽

Controlled Trial ◽

Liver Glycogen ◽

Cycling Performance ◽

Controlled Study ◽

Mean Power ◽

Road Racing ◽

Mean Power Output

We evaluated the effect of carbohydrate (CHO) loading on cycling performance that was designed to be similar to the demands of competitive road racing. Seven well-trained cyclists performed two 100-km time trials (TTs) on separate occasions, 3 days after either a CHO-loading (9 g CHO ⋅ kg body mass− 1 ⋅ day− 1) or placebo-controlled moderate-CHO diet (6 g CHO ⋅ kg body mass− 1 ⋅ day− 1). A CHO breakfast (2 g CHO/kg body mass) was consumed 2 h before each TT, and a CHO drink (1 g CHO ⋅ kg.body mass− 1 ⋅ h− 1) was consumed during the TTs to optimize CHO availability. The 100-km TT was interspersed with four 4-km and five 1-km sprints. CHO loading significantly increased muscle glycogen concentrations (572 ± 107 vs. 485 ± 128 mmol/kg dry wt for CHO loading and placebo, respectively; P < 0.05). Total muscle glycogen utilization did not differ between trials, nor did time to complete the TTs (147.5 ± 10.0 and 149.1 ± 11.0 min; P = 0.4) or the mean power output during the TTs (259 ± 40 and 253 ± 40 W, P = 0.4). This placebo-controlled study shows that CHO loading did not improve performance of a 100-km cycling TT during which CHO was consumed. By preventing any fall in blood glucose concentration, CHO ingestion during exercise may offset any detrimental effects on performance of lower preexercise muscle and liver glycogen concentrations. Alternatively, part of the reported benefit of CHO loading on subsequent athletic performance could have resulted from a placebo effect.

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Variability in Power Output During Cycling in International Olympic-Distance Triathlon

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2013-0303 ◽

2014 ◽

Vol 9 (4) ◽

pp. 732-734 ◽

Cited By ~ 5

Author(s):

Naroa Etxebarria ◽

Shaun D’Auria ◽

Judith M. Anson ◽

David B. Pyne ◽

Richard A. Ferguson

Keyword(s):

Body Mass ◽

Power Output ◽

Coefficient Of Variation ◽

Aerobic Power ◽

Maximal Aerobic Power ◽

Mean Power ◽

Large Power ◽

Elite Level ◽

The Mean ◽

Mean Power Output

Purpose:The patterns of power output in the ~1-h cycle section of Olympic-distance triathlon races are not well documented. Here the authors establish a typical cycling-race profile derived from several International Triathlon Union elite-level draftinglegal triathlon races.Methods:The authors collated 12 different race power profiles from elite male triathletes (N = 5, age 25 ± 5 y, body mass 65.5 ± 5.6 kg; mean ± SD) during 7 international races. Power output was recorded using SRM cranks and analyzed with proprietary software.Results:The mean power output was 252 ± 33 W, or 3.9 ± 0.5 W/kg in relative terms, with a coefficient of variation of 71% ± 13%. Normalized power (power output an athlete could sustain if intensity were maintained constant without any variability) for the entire cycle section was 291 ± 29 W, or 40 ± 13 W higher than the actual mean power output. There were 34 ± 14 peaks of power output above 600 W and ~18% time spent at >100% of maximal aerobic power.Conclusion:Cycling during Olympic-distance triathlon, characterized by frequent and large power variations including repeat supramaximal efforts, equates to a higher workload than cycling at constant power.

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Muscle Regenerative Capacity May Be Reduced When Aerobic Exercise Is Initiated with Low Glycogen Content

Current Developments in Nutrition ◽

10.1093/cdn/nzaa049_037 ◽

2020 ◽

Vol 4 (Supplement_2) ◽

pp. 644-644

Author(s):

Lee Margolis ◽

Marques Wilson ◽

Claire Whitney ◽

Christopher Carrigan ◽

Nancy Murphy ◽

...

Keyword(s):

Aerobic Exercise ◽

Muscle Glycogen ◽

Glycogen Content ◽

Cycle Ergometry ◽

Glycogen Depletion ◽

High Fat ◽

Carbohydrate Ingestion ◽

Muscle Glycogen Content ◽

High Carbohydrate ◽

Insulin Dependent

Abstract Objectives Maintaining low muscle glycogen content during recovery from aerobic exercise with low carbohydrate, high fat feeding has been shown to reduce insulin-mediated anabolic signaling compared to high carbohydrate feeding. The effects of low muscle glycogen content on intracellular regulators of muscle mass before and after aerobic exercise with carbohydrate ingestion is unclear. This study examined the effect of initiating aerobic exercise with low muscle glycogen content on postprandial insulin-dependent muscle anabolic signaling and myogenesis. Methods Twelve men (mean ± SD, age: 21 ± 4 y; body mass: 83 ± 11 kg; VO2peak: 44 ± 3 mL/kg/min) completed 2 cycle ergometry glycogen depletion trials separated by 7 d, followed by a 24-h period of isocaloric high fat (1.5 g/kg carbohydrate, 3.0 g/kg fat) or high carbohydrate (6.0 g/kg carbohydrate, 1.0 g/kg fat) refeeding to elicit low (LOW; 217 ± 103 mmol/kg dry wt) or adequate (AD; 396 ± 70 mmol/kg dry wt) glycogen content in randomized order. Participants then performed 80 min of cycle ergometry (64 ± 3% VO2peak) while ingesting 146 g of carbohydrate. Protein signaling (Western blotting) and gene transcription (RT-qPCR) were determined from vastus lateralis biopsies obtained before glycogen depletion (baseline, BASE), and before (PRE) and after (POST) exercise. Data presented as fold change relative to BASE for LOW and AD. Results Independent of time, carbohydrate sensing p-AMPKThr172 was higher (P < 0.05) in LOW compared to AD, while p-p38MAPKThr180/Tyr182 was higher (P < 0.05) in LOW at POST, but not different PRE. Insulin sensitive p-AKTThr473 was higher (P < 0.05) in AD compared to LOW, regardless of time. Anabolic regulators, p-mTORC1Ser2448, p-p70S6KSer424/421, and p-rpS6Ser235/236 were higher (P < 0.05) POST compared to PRE and BASE, independent of group. Regulators of myogenesis, MYOD and MYOGENIN were lower (P < 0.05) in LOW compared to AD, regardless of time, while PAX7 was lower (P < 0.05) in LOW compared to AD at PRE, but not different POST. Conclusions Initiating aerobic exercise with low muscle glycogen content does not appear to affect downstream insulin-dependent anabolic signaling, yet reductions in myogenic regulator factors suggest muscle repair and remodeling in recovery from exercise may be impaired. Funding Sources Work supported by DHP JPC-5/MOMRP; authors’ views not official U.S. Army or DoD policy.

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Effects of Acute Caffeine Intake on Power Output and Movement Velocity During a Multiple-Set Bench Press Exercise Among Mild Caffeine Users

Journal of Human Kinetics ◽

10.2478/hukin-2021-0044 ◽

2021 ◽

Vol 78 (1) ◽

pp. 219-228

Author(s):

Aleksandra Filip-Stachnik ◽

Michal Krzysztofik ◽

Magdalena Kaszuba ◽

Katarzyna Leznicka ◽

Maciej Kostrzewa ◽

...

Keyword(s):

Body Mass ◽

Power Output ◽

Bench Press ◽

Peak Power Output ◽

Caffeine Intake ◽

Mean Power ◽

Acute Dose ◽

Main Effect ◽

Bar Velocity ◽

Mean Power Output

Abstract The main goal of this study was to evaluate the effectiveness of an acute dose of caffeine (6 mg/kg body mass (b.m.)) on power output and bar velocity during a bench press multiple-set resistance training session in participants with mild daily caffeine consumption (in the range of 1 to 3 mg/kg/b.m). Thirteen recreationally active male participants (age: 21.9 ± 1.2 years, body mass: 74.4 ± 5.3 kg, body mass index: 23.1 ± 1.6 kg/m2, bench press onerepetition maximum (1RM): 79.2 ± 14.9 kg), with daily caffeine ingestion of 1.56 ± 0.56 mg/kg/b.m., participated in the study with a randomized double-blind experimental design. Each participant performed two identical experimental sessions, 60 min after the intake of a placebo (PLAC) or 6 mg/kg/b.m. of caffeine (CAF-6). In each experimental session, participants performed 5 sets of 5 repetitions of the bench press exercise with a load equivalent to 70% 1RM. The eccentric and concentric phases of the bench press exercise were performed at maximal possible velocity in each repetition. Bar velocity was recorded with a linear position transducer and power output was calculated using velocity and load data. A two-way repeated measures ANOVA indicated no significant substance x set interaction for mean power output (MP), mean bar velocity (MV), peak power output (PP) and peak bar velocity (PV). However, there was a significant main effect of substance on MP (p < 0.01; η2 = 0.47) and MV (p < 0.01; η2 =0.45). Post hoc analysis for main effect revealed that MP and MV values in the CAF-6 group were higher than in the PLAC group in all 5 sets of the exercise (p < 0.05). In conclusion, this study demonstrated that an acute dose of caffeine before resistance exercise increased mean power output and mean bar velocity during a multiple-set bench press exercise protocol among mild caffeine users.

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Dietary carbohydrate, muscle glycogen content, and endurance performance in well-trained women

Journal of Applied Physiology ◽

10.1152/jappl.2000.88.6.2151 ◽

2000 ◽

Vol 88 (6) ◽

pp. 2151-2158 ◽

Cited By ~ 41

Author(s):

J. Lynne Walker ◽

George J. F. Heigenhauser ◽

Eric Hultman ◽

Lawrence L. Spriet

Keyword(s):

Menstrual Cycle ◽

Muscle Glycogen ◽

Luteal Phase ◽

Glycogen Content ◽

Vastus Lateralis ◽

Endurance Performance ◽

Liver Glycogen ◽

Dietary Carbohydrate ◽

Carbohydrate Diet ◽

Muscle Glycogen Content

This study examined the ability of well-trained eumenorrheic women to increase muscle glycogen content and endurance performance in response to a high-carbohydrate diet (HCD; ∼78% carbohydrate) compared with a moderate-carbohydrate diet (MD; ∼48% carbohydrate) when tested during the luteal phase of the menstrual cycle. Six women cycled to exhaustion at ∼80% maximal oxygen uptake (V˙o 2 max) after each of the randomly assigned diet and exercise-tapering regimens. A biopsy was taken from the vastus lateralis before and after exercise in each trial. Preexercise muscle glycogen content was high after the MD (625.2 ± 50.1 mmol/kg dry muscle) and 13% greater after the HCD (709.0 ± 44.8 mmol/kg dry muscle). Postexercise muscle glycogen was low after both trials (MD, 91.4 ± 34.5; HCD, 80.3 ± 19.5 mmol/kg dry muscle), and net glycogen utilization during exercise was greater after the HCD. The subjects also cycled longer at ∼80%V˙o 2 max after the HCD vs. MD (115:31 ± 10:47 vs. 106:35 ± 8:36 min:s, respectively). In conclusion, aerobically trained women increased muscle glycogen content in response to a high-dietary carbohydrate intake during the luteal phase of the menstrual cycle, but the magnitude was smaller than previously observed in men. The increase in muscle glycogen, and possibly liver glycogen, after the HCD was associated with increased cycling performance to volitional exhaustion at ∼80%V˙o 2 max.

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