Improvements in exercise performance: effects of carbohydrate feedings and diet

1987 ◽  
Vol 62 (3) ◽  
pp. 983-988 ◽  
Author(s):  
P. D. Neufer ◽  
D. L. Costill ◽  
M. G. Flynn ◽  
J. P. Kirwan ◽  
J. B. Mitchell ◽  
...  
Keyword(s):  
Muscle Glycogen ◽  
Exercise Performance ◽  
Cycle Ergometer ◽  
Serum Glucose ◽  
O2 Consumption ◽  
Total Work ◽  
Vo2 Max ◽  
Fed State ◽  
Performance Effects ◽  
Muscle Glycogen Concentration

In an effort to determine the effects of carbohydrate (CHO) feedings immediately before exercise in both the fasted and fed state, 10 well-trained male cyclists [maximum O2 consumption (VO2 max), 4.35 +/- 0.11 l/min)] performed 45 min of cycling at 77% VO2 max followed by a 15-min performance ride on an isokinetic cycle ergometer. After a 12-h fast, subjects ingested 45 g of liquid carbohydrate (LCHO), solid carbohydrate confectionery bar (SCHO), or placebo (P) 5 min before exercise. An additional trial was performed in which a high-CHO meal (200 g) taken 4 h before exercise was combined with a confectionery bar feeding (M + SCHO) immediately before the activity. At 10 min of exercise, serum glucose values were elevated by 18 and 24% during SCHO and LCHO, respectively, compared with P. At 0 and 45 min no significant differences were observed in muscle glycogen concentration or total use between the four trials. Total work produced during the final 15 min of exercise was significantly greater (P less than 0.05) during M + SCHO (194,735 +/- 9,448 N X m), compared with all other trials and significantly greater (P less than 0.05) during LCHO and SCHO (175,204 +/- 11,780 and 176,013 +/- 10,465 N X m, respectively) than trial P (159,143 +/- 11,407 N X m). These results suggest that, under conditions when CHO stores are less than optimal, exercise performance is enhanced with the ingestion of 45 g of CHO 5 min before 1 h of intense cycling.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate feedings and exercise performance: effect of initial muscle glycogen concentration

1993 ◽  
Vol 74 (6) ◽  
pp. 2998-3005 ◽  
Author(s):  
J. J. Widrick ◽  
D. L. Costill ◽  
W. J. Fink ◽  
M. S. Hickey ◽  
G. K. McConell ◽  
...  
Keyword(s):  
Muscle Glycogen ◽  
Exercise Performance ◽  
Power Output ◽  
Time Trial ◽  
Serum Glucose ◽  
O2 Consumption ◽  
Performance Effect ◽  
Glycogen Concentration ◽  
Performance Times ◽  
Muscle Glycogen Concentration

To determine whether the ergogenic benefits of carbohydrate (CHO) feedings are affected by preexercise muscle glycogen levels, eight cyclists performed four self-paced time trials on an isokinetic ergometer over a simulated distance of 70 km. Trials were performed under the following preexercise muscle glycogen and beverage conditions: 1) high glycogen (180.2 +/- 9.7 mmol/kg wet wt) with a CHO beverage (HG-CHO), 2) high glycogen (170.2 +/- 10.4 mmol/kg wet wt) with a non-CHO beverage (HG-NCHO), 3) low glycogen (99.8 +/- 6.0 mmol/kg wet wt) with a CHO beverage (LG-CHO), and 4) low glycogen (109.7 +/- 5.3 mmol/kg wet wt) with a non-CHO beverage (LG-NCHO). The CHO drink (ingested at the onset of exercise and every 10 km thereafter) provided 116 +/- 6 g CHO/trial and prevented the decline in serum glucose observed during both NCHO trials. Performance times ranged from 117.93 +/- 1.44 (HG-CHO) to 122.91 +/- 2.46 min (LG-NCHO). No intertrial differences (P > 0.05) were observed for O2 consumption (75% of maximal O2 consumption), power output (237 W), or self-selected pace (8.44 min/5 km) during the initial 71–79% of exercise. Over the final 14% of the time trial, power output and pace (231 W and 8.62 min/5 km) were similar for the HG-CHO, HG-NCHO, and LG-CHO conditions, but both variables were significantly lower during the LG-NCHO trial (198 W and 9.67 min/5 km, P < 0.05 vs. all other trials).(ABSTRACT TRUNCATED AT 250 WORDS)

Niacin supplementation impairs exercise performance

2021 ◽  
Author(s):  
Greggory R. Davis ◽  
Arnold G. Nelson
Keyword(s):  
Body Weight ◽  
Resistance Exercise ◽  
Aerobic Exercise ◽  
Exercise Performance ◽  
Respiratory Exchange Ratio ◽  
Time To Exhaustion ◽  
Total Work ◽  
Cycling Exercise ◽  
Exercise Time ◽  
Performance Effects

Abstract. Several pre-workout supplements contain niacin, although the exercise performance effects of niacin are poorly understood. The purpose of the present study was to examine the performance effects of niacin versus caffeine as a pre-workout supplement. Twenty-five untrained males were recruited to complete three identical ramped aerobic cycling exercise trials. Participants were administered caffeine (CA) at 5 mg/kg body weight, 1000 mg niacin (NI), or a methylcelluloce placebo (PL) supplement prior to each trial. NI treatment induced significantly higher respiratory exchange ratio (RER) during exercise compared to the CA treatment, but not the PL treatment (PL=0.87±0.08, NI=0.91±0.08, CA=0.87±0.08; p=0.02). Similarly, exercise time to exhaustion (in minutes) was significantly different between the NI treatment and the CA treatment, but not the PL treatment (PL=27.45±4.47, NI=26.30±4.91, CA=28.76±4.86; p<0.01). Habitual caffeine use (p=0.16), habitual aerobic exercise (p=0.60), and habitual resistance exercise (p=0.10) did not significantly affect RER. Similarly, habitual caffeine use (p=0.72), habitual aerobic exercise (p=0.08), and habitual resistance exercise (p=0.39) did not significantly affect total work performed. The elevated RER and decreased time to exhaustion in the NI treatment suggests limited lipid availability during exercise and impaired exercise performance.

Carbohydrate loading and metabolism during exercise in men and women

1995 ◽  
Vol 78 (4) ◽  
pp. 1360-1368 ◽  
Author(s):  
M. A. Tarnopolsky ◽  
S. A. Atkinson ◽  
S. M. Phillips ◽  
J. D. MacDougall
Keyword(s):  
Endurance Exercise ◽  
Muscle Glycogen ◽  
Protein Oxidation ◽  
Endurance Athletes ◽  
O2 Consumption ◽  
Glycogen Concentration ◽  
Performance Time ◽  
Carbohydrate Loading ◽  
Endurance Cycling ◽  
Muscle Glycogen Concentration

During endurance exercise at approximately 65% maximal O2 consumption, women oxidize more lipids, and therefore decrease carbohydrate and protein oxidation, compared with men (L.J. Tarnopolsky, M.A. Tarnopolsky, S.A. Atkinson, and J.D. MacDougall. J. Appl. Physiol. 68: 302–308, 1990; S.M. Phillips, S.A. Atkinson, M.A. Tarnopolsky, and J.D. MacDougall. J. Appl. Physiol. 75: 2134–2141, 1993). The main purpose of this study was to examine the ability of similarly trained male (n = 7) and female (n = 8) endurance athletes to increase muscle glycogen concentrations in response to an increase in dietary carbohydrate from 55–60 to 75% of energy intake for a period of 4 days (carbohydrate loading). In addition, we sought to examine whether gender differences existed in metabolism during submaximal endurance cycling at 75% peak O2 consumption (VO2 peak) for 60 min. The men increased muscle glycogen concentration by 41% in response to the dietary manipulation and had a corresponding increase in performance time during an 85% VO2 peak trial (45%), whereas the women did not increase glycogen concentration (0%) or performance time (5%). The women oxidized significantly more lipid and less carbohydrate and protein compared with the men during exercise at 75% VO2-peak. We conclude that women did not increase muscle glycogen in response to the 4-day regimen of carbohydrate loading described. In addition, these data support previous observations of greater lipid and lower carbohydrate and protein oxidation by women vs. men during submaximal endurance exercise.

Blood Glucose and Glucoregulatory Hormone Responses to Solid and Liquid Carbohydrate Ingestion During Exercise

1998 ◽  
Vol 8 (1) ◽  
pp. 70-83 ◽  
Author(s):  
Robert A. Robergs ◽  
Susie B. McMinn ◽  
Cristine Mermier ◽  
Guy Leadbetter ◽  
Brent Ruby ◽  
...  
Keyword(s):  
Blood Glucose ◽  
Plasma Glucose ◽  
Exercise Performance ◽  
Serum Glucose ◽  
Solid Food ◽  
Total Work ◽  
Carbohydrate Ingestion ◽  
Added Water ◽  
Hormone Responses ◽  
Ad Libitum

This study was conducted to compare blood glucose and glucoregulatory hormone responses to the ingestion of solid and liquid carbohydrate (CHO) during prolonged cycling, followed by 30 min of isokinetic cycling. Eight male cyclists randomly completed three cycling trials (LC = liquid CHO, SCE = solid CHO with water equal to LC, SCA = solid CHO + ad libitum water). Each subject cycled for 120 min at 65% of VO2max with CHO ingestion (0.6 g CHO/kg/hr) at 0, 30, 60, 90, and 120 min. Subjects then completed a 30-min maximal isokinetic ride at 90 rpm. There was no significant (p < .05) difference between the trials for plasma glucose, insulin, glucagon, glycerol, lactate, RER, HR, VO2 RPE, and total work performed during the isokinetic ride. However, serum glucose was significantly lower in the SCE and SCA trials compared to LC at 80 min. The ingestion of a solid food containing CHO. protein, and fat with added water produced similar blood glucose, metabolic, glucoregulatory hormone, and exercise performance responses to those seen with the ingestion of liquid CHO.

Muscle metabolites and performance during high-intensity, intermittent exercise

1998 ◽  
Vol 84 (5) ◽  
pp. 1687-1691 ◽  
Author(s):  
Mark Hargreaves ◽  
Michael J. McKenna ◽  
David G. Jenkins ◽  
Stuart A. Warmington ◽  
Jia L. Li ◽  
...  
Keyword(s):  
Exercise Performance ◽  
Peak Power ◽  
Intermittent Exercise ◽  
Exercise Bout ◽  
Creatine Phosphate ◽  
Cycle Ergometer ◽  
Total Work ◽  
Muscle Lactate ◽  
The Third ◽  
And Performance

Six men were studied during four 30-s “all-out” exercise bouts on an air-braked cycle ergometer. The first three exercise bouts were separated by 4 min of passive recovery; after the third bout, subjects rested for 4 min, exercised for 30 min at 30–35% peak O2 consumption, and rested for a further 60 min before completing the fourth exercise bout. Peak power and total work were reduced ( P < 0.05) during bout 3 [765 ± 60 (SE) W; 15.8 ± 1.0 kJ] compared with bout 1 (1,168 ± 55 W, 23.8 ± 1.2 kJ), but no difference in exercise performance was observed between bouts 1 and 4 (1,094 ± 64 W, 23.2 ± 1.4 kJ). Before bout 3, muscle ATP, creatine phosphate (CP), glycogen, pH, and sarcoplasmic reticulum (SR) Ca2+ uptake were reduced, while muscle lactate and inosine 5′-monophosphate were increased. Muscle ATP and glycogen before bout 4 remained lower than values before bout 1( P < 0.05), but there were no differences in muscle inosine 5′-monophosphate, lactate, pH, and SR Ca2+ uptake. Muscle CP levels before bout 4 had increased above resting levels. Consistent with the decline in muscle ATP were increases in hypoxanthine and inosine before bouts 3 and 4. The decline in exercise performance does not appear to be related to a reduction in muscle glycogen. Instead, it may be caused by reduced CP availability, increased H+ concentration, impairment in SR function, or some other fatigue-inducing agent.

Influence of carbohydrate dosage on exercise performance and glycogen metabolism

1989 ◽  
Vol 67 (5) ◽  
pp. 1843-1849 ◽  
Author(s):  
J. B. Mitchell ◽  
D. L. Costill ◽  
J. A. Houmard ◽  
W. J. Fink ◽  
D. D. Pascoe ◽  
...  
Keyword(s):  
Blood Glucose ◽  
Vastus Lateralis ◽  
Venous Blood ◽  
Glycogen Metabolism ◽  
Cycle Ergometer ◽  
Work Output ◽  
O2 Consumption ◽  
Total Work ◽  
Blood Samples ◽  
Muscle Biopsies

This study was undertaken to examine the effects of ingestion of carbohydrate (CHO) solutions of 0 (WP), 6 (CHO-6), 12 (CHO-12), and 18 g CHO/100 ml (CHO-18) on performance and muscle glycogen use. Ten trained cyclists performed five 120-min cycling trials. The first 105 min of each trial was at 70% of maximal O2 consumption (VO2max), and the final 15 min was an all-out performance ride on an isokinetic cycle ergometer equipped to measure total work output. In one of the trials (CHO-12I) the submaximal portion of the ride consisted of seven 15-min rides at 70% of VO2max with a 3-min rest between each ride. Every 15 min the men consumed 8.5 ml.kg-1.h-1 (approximately 150 ml) of one of the four test solutions. Venous blood samples were obtained every 15 min for glucose and insulin. Muscle biopsies were obtained from the vastus lateralis at 0 and 105 min in the WP and the CHO-12 continuous and intermittent trials. Biopsy samples were assayed for glycogen and sectioned and stained for myosin adenosinetriphosphatase and glycogen for single fiber depletion measurements. There were no differences in glycogen use (86.7 +/- 6.0, 75.5 +/- 7.9, and 83.5 +/- 5.5 mmol/kg for the WP, CHO-12C, and CHO-12I, respectively) or depletion patterns between the WP and the two CHO-12 trials. Blood glucose was significantly elevated in both the CHO-12 trials and in the CHO-18 trial compared with the WP trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate Ingestion during Exercise: Effects on Muscle Glycogen Resynthesis after Exercise

1993 ◽  
Vol 3 (4) ◽  
pp. 418-430 ◽  
Author(s):  
Jeffrey J. Zachwieja ◽  
David L. Costill ◽  
William J. Fink
Keyword(s):  
Muscle Glycogen ◽  
Vastus Lateralis ◽  
Cycle Ergometer ◽  
Serum Glucose ◽  
Carbohydrate Ingestion ◽  
Glycogen Resynthesis ◽  
Carbohydrate Feeding ◽  
Muscle Biopsies ◽  
Carbohydrate Solution ◽  
Carbohydrate Supplement

To determine the effect of carbohydrate feeding on muscle glycogen resynthesis, 8 male cyclists pedaled for 2 hrs on a cycle ergometer at 70% of VO2max while consuming either a 10% carbohydrate solution (CHO) or a nonnutritive sweet placebo (No CHO). Muscle biopsies were obtained from the vastus lateralis prior to, immediately postexercise, and at 2,4, and 24 hrs of recovery. Blood samples were taken before and at the end of exercise, and at specified times during recovery. During both trials food intake was withheld for the first 2 hrs of recovery, but at 2 hrs postexercise a 24% carbohydrate solution was ingested. The rate of muscle glycogen resynthesis during the first 2 hrs of recovery was similar for the CHO and No CHO trials. Following ingestion of the 24% carbohydrate supplement, the rates of muscle glycogen resynthesis increased similarly in both trials. These similar rates of resynthesis following ingestion of the carbohydrate supplement were obtained despite significantly greater serum glucose and insulin levels during the No CHO trial. The results indicate that the carbohydrate feedings taken during exercise had little effect on postexercise muscle glycogen resynthesis.

Effects of postexercise carbohydrate-protein feedings on muscle glycogen restoration

2000 ◽  
Vol 88 (6) ◽  
pp. 1976-1982 ◽  
Author(s):  
John A. Carrithers ◽  
David L. Williamson ◽  
Philip M. Gallagher ◽  
Michael P. Godard ◽  
Kimberley E. Schulze ◽  
...  
Keyword(s):  
Muscle Glycogen ◽  
Exercise Bout ◽  
Peak Oxygen Uptake ◽  
Cycle Ergometer ◽  
Serum Glucose ◽  
Cycle Exercise ◽  
Blood Samples ◽  
Ergometer Exercise ◽  
Insulin Responses ◽  
Muscle Biopsies

The purpose of this investigation was to determine the effects of postexercise eucaloric carbohydrate-protein feedings on muscle glycogen restoration after an exhaustive cycle ergometer exercise bout. Seven male collegiate cyclists [age = 25.6 ± 1.3 yr, height = 180.9 ± 3.2 cm, wt = 75.4 ± 4.0 kg, peak oxygen uptake (V˙o 2 peak) = 4.20 ± 0.2 l/min] performed three trials, each separated by 1 wk: 1) 100% α-d-glucose [carbohydrate (CHO)], 2) 70% carbohydrate-20% protein (PRO)-10% fat, and 3) 86% carbohydrate-14% amino acid (AA). All feedings were eucaloric, based on 1.0 g ⋅ kg body wt− 1 ⋅ h− 1of CHO, and administered every 30 min during a 4-h muscle glycogen restoration period in an 18% wt/vol solution. Muscle biopsies were obtained immediately and 4 h after exercise. Blood samples were drawn immediately after the exercise bout and every 0.5 h for 4 h during the restoration period. Increases in muscle glycogen concentrations for the three feedings (CHO, CHO-PRO, CHO-AA) were 118 mmol/kg dry wt; however, no differences among the feedings were apparent. The serum glucose and insulin responses did not differ throughout the restoration period among the three feedings. These results suggest that muscle glycogen restoration does not appear to be enhanced with the addition of proteins or amino acids to an eucaloric CHO feeding after exhaustive cycle exercise.

Physiological effects of tapering in highly trained athletes

1992 ◽  
Vol 72 (2) ◽  
pp. 706-711 ◽  
Author(s):  
B. Shepley ◽  
J. D. MacDougall ◽  
N. Cipriano ◽  
J. R. Sutton ◽  
M. A. Tarnopolsky ◽  
...  
Keyword(s):  
Muscle Glycogen ◽  
Citrate Synthase ◽  
Distance Runners ◽  
Total Blood ◽  
Glycogen Concentration ◽  
Performance Effects ◽  
Before And After ◽  
Moderate Volume ◽  
And Performance ◽  
Muscle Glycogen Concentration

This study examined some of the physiological and performance effects of three different tapers in highly trained athletes. After 8 wk of training, nine male middle-distance runners were randomly assigned to one of three different 7-day tapers: a high-intensity low-volume taper (HIT), a low-intensity moderate-volume taper (LIT), or a rest-only taper (ROT). After the first taper, subjects resumed training for 4 wk and performed a second taper and then resumed training for 4 wk and completed the remaining taper, so that each subject underwent all three tapers. Performance was measured before and after each taper by a treadmill run to fatigue at a velocity equivalent each subject's best 1,500-m time. Voluntary isometric strength and evoked contractile properties of the quadriceps were measured before and after each taper, as were muscle glycogen concentration and citrate synthase activity (from needle biopsies) and total blood and red cell volume by 125I and 51Cr tagging. Maximal O2 consumption was unaffected by all three tapers, but running time to fatigue increased significantly after HIT (+22%). It was unaffected by LIT (+6%) and ROT (-3%) procedure. Citrate synthase activity increased significantly with HIT and decreased significantly with ROT. Muscle glycogen concentration increased significantly after ROT and HIT, and strength increased after all three tapers. Total blood volume increased significantly after HIT and decreased after ROT.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Enhanced ventilatory and exercise performance in athletes with slight expiratory resistive loading

1997 ◽  
Vol 83 (2) ◽  
pp. 503-510 ◽  
Author(s):  
Lawrence L. Fee ◽  
Richard M. Smith ◽  
Michael B. English
Keyword(s):  
Blood Flow ◽  
Lung Volume ◽  
Exercise Performance ◽  
Minute Ventilation ◽  
Cycle Ergometer ◽  
Strenuous Exercise ◽  
Intensity Level ◽  
Resistive Loading ◽  
Performance Effects ◽  
And Performance

Fee, Lawrence L., Richard M. Smith, and Michael B. English.Enhanced ventilatory and exercise performance in athletes with slight expiratory resistive loading. J. Appl. Physiol. 83(2): 503–510, 1997.—We determined the cardiorespiratory and performance effects of slight (1.5–3.0 cmH2O) expiratory resistive loading (ERL). Twenty-eight highly fit [peak O2 uptake (V˙o 2 peak) = 63.6 ± 1.3 ml ⋅ kg−1 ⋅ min−1] athletes (age = 33.5 ± 1.3 yr) performed pairedV˙o 2 peak cycle ergometer tests (control vs. ERL). End-expiratory lung volume was separately determined in a subset of subjects ( n = 12) at steady-state 75% maximum power output (POmax) and was found to increase (0.67 ± 0.29 liter) with ERL. In theV˙o 2 peaktests, peak expiratory pressure at the mouth, mean inspiratory flow, minute ventilation, and O2 pulse were greater with ERL at every intensity level (i.e., 75, 80, 85, and 90% POmax). Increased minute ventilation was largely due to a trend toward increased tidal volume ( P < 0.05 at 80% POmax). O2 uptake was greater at 90% POmax with ERL. Increased O2 pulse with ERL at comparative workloads suggests that stroke volume was augmented with ERL. Also, with ERL, athletes attained higherV˙o 2 peak (63.0 ± 1.4 vs. 60.1 ± 1.3 ml ⋅ kg−1 ⋅ min−1) and greater POmax (352.0 ± 9.9 vs. 345.7 ± 9.5 W). We conclude that elevated end-expiratory lung volume in response to slight ERL during strenuous exercise served to attenuate both airflow and blood flow limitations, which enhanced exercise capacity.

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