Glycogen depletion sprints

Glycogenin is the self-glycosylating protein primer that initiates glycogen granule formation. To examine the role of this protein during glycogen resynthesis, eight male subjects exercised to exhaustion on a cycle ergometer at 75% Vo2 max followed by five 30-s sprints at maximal capacity to further deplete glycogen stores. During recovery, carbohydrate (75 g/h) was supplied to promote rapid glycogen repletion, and muscle biopsies were obtained from the vastus lateralis at 0, 30, 120, and 300 min postexercise...

Supercompensated muscle glycogen can be achieved by using several carbohydrate (CHO)-loading protocols. This study compared the effectiveness of two "modified" CHO-loading protocols. Additionally, we determined the effect of light cycle training on muscle glycogen. Subjects completed a depletion (D, n = 15) or nondepletion (ND, n = 10) CHO-loading protocol. After a 2-day adaptation period in a metabolic ward, the D group performed a 120-min cycle exercise at 65% peak oxygen uptake (VO2 peak) followed by 1-min sprints at 120% VO2 peak to exhaustion...

This study examined fuel depletion in white muscle of juvenile rainbow trout sprinted to fatigue to determine whether the onset of fatigue is associated with a measurable metabolic change within the muscle and whether muscle glycogen levels influence endurance. In this study, "fuels" refer to any energy-supplying compounds and include glycogen, phosphocreatine (PCr), and ATP. Fuel depletion in white muscle was estimated by the calculation of the anaerobic energy expenditure (AEE; in micromol ATP equivalents g(-1)) from the reduction of PCr and ATP and the accumulation of lactate...

The hyperoxia-improved tolerance to maximal aerobic performance was studied in relation to exercising muscle metabolic state. Five students were submitted to four different tests on a cycle ergometer, each being conducted under normoxia and hyperoxia (60% FiO2) on separate days: Test 1, a progressive exercise until exhaustion to determine the maximal work load (Wmax) which was unchanged by hyperoxia; Test 2, an exercise at Wmax (287 +/- 12 W) until exhaustion to determine the performance time (texh) which was elevated by 38% under hyperoxia but exhaustion occurred at the same arterial proton and lactate concentrations; Test 3 (S-Exercise test) consisted of cycling at Wmax for 90% normoxic-texh (4...

The purpose of this study was to develop a model of muscle glycogen depletion and to study the effect of this model on aerobic and anaerobic capacity of horses. The maximal rate of oxygen consumption (VO2max), maximal accumulated oxygen deficit (MAOD), muscle glycogen concentration and blood lactate concentration of 6 fit Standardbred horses were measured on 3 occasions 7 days apart (Trials 1, 2 and 3). Between Trials 2 and 3, strenuous exercise intended to deplete muscle glycogen was performed by exercising horses on the treadmill on 3 consecutive days...

Several carbohydrate (CHO)-loading protocols have been used to achieve muscle glycogen supercompensation and prolong endurance performance. This study assessed the persistence of muscle glycogen supercompensation over the 3 days after the supercompensation protocol. Trained male athletes completed a 6-day CHO-loading protocol that included cycle ergometer exercise and dietary manipulations. The 3-day depletion phase began with 115 min of cycling at 75% peak oxygen uptake followed by 3 x 60-s sprints and included the subjects consuming a low-CHO/high-protein/high-fat (10:41:49%) diet...

We reported previously that intake of carbohydrate foods with a high glycemic index (GI) produced greater glycogen storage and greater postprandial glucose and insulin responses during 24 h of postexercise recovery than did intake of low-GI carbohydrate foods. In the present study we examined the importance of the greater incremental glucose and insulin concentrations on glycogen repletion by comparing intake of large carbohydrate meals ("gorging") with a pattern of frequent, small, carbohydrate snacks ("nibbling"), which simulates the flattened glucose and insulin responses after low-GI carbohydrate meals...

The effect of the glycemic index (GI) of postexercise carbohydrate intake on muscle glycogen storage was investigated. Five well-trained cyclists undertook an exercise trial to deplete muscle glycogen (2 h at 75% of maximal O2 uptake followed by four 30-s sprints) on two occasions, 1 wk apart. For 24 h after each trial, subjects rested and consumed a diet composed exclusively of high-carbohydrate foods, with one trial providing foods with a high GI (HI GI) and the other providing foods with a low GI (LO GI)...

To examine the effect of exercise on sarcoplasmic reticulum function in muscle tissue of different fibre composition, adult male Wistar rats weighing 388 +/- 23 g (x +/- SE) ran intermittently on a treadmill until fatigue. Fatigue was induced by 15-20 min of running performed at 52 m/min on an 8 degrees incline in periods of 2.5 min of exercise separated by 2 min of recovery. Analysis of sarcoplasmic reticulum Ca2+ ATPase activity determined in homogenates indicated no difference (p > 0.05) between age-matched control and exercised tissue for the soleus (SOL; 0...

Two groups of male subjects were studied to examine the effects of different exercise protocols on performance of an isokinetic, short-time strength test, the performance of which is related to fast twitch (FT) muscle fiber recruitment. The laboratory group (LG) (n = 10) cycled (30 min, 70% VO2 max), ran (75 min), and performed repeated bouts of "sprint" cycling and rapid, maximal contractions of the quadriceps. The marathon group (MG) (n = 7) participated in and completed Stockholm's Marathon 1979...

Ten men were studied during 4 h of cycling to determine the effect of solid carbohydrate (CHO) feedings on muscle glycogen utilization and exercise performance. In the experimental trial (E) the subjects ingested 43 g of sucrose in solid form along with 400 ml of water at 0, 1, 2 and 3 h of exercise. During the control trial (C) they received 400 ml of an artificially sweetened drink without solid CHO. No differences in VO2, heart rate, or total energy expenditure were observed between trials; however, respiratory exchange ratios were significantly (P less than 0...

The purpose of this study was to determine whether or not trained athletes have the same capacity for supercompensation of muscle glycogen as untrained subjects. Muscle glycogen was measured in 4 highly trained cyclists and 4 untrained controls over a 6 day period of exercise and dietary manipulation. During the week prior to the investigation the trained group tapered their training load but maintained a high carbohydrate intake as they would in preparation for a major competition. Needle biopsies were taken from the vastus lateralis before and after exhaustive cycle ergometry at 73% VO2 max followed by several sprint intervals, after 3 days on a carbohydrate-restricted diet and after 2 and 3 days on a high carbohydrate diet...

In the process of defining the recruitment of fuel and pathway selection in rainbow trout fast-twitch white skeletal muscle, it was clear that the near-maximal myosin adenosinetriphosphatase activity during a 10-s sprint was supported solely by phosphocreatine hydrolysis. A conservative estimate of the ATP turnover was 188 mumol X g wet wt-1 X min-1. It was not until the rate and force of contraction decreased that the relative contribution of anaerobic glycogenolysis became increasingly important. Over a 10-min period of burst swimming at approximately 120% of maximum aerobic steady-state swimming velocity of trout determined in a Brett-type swim tunnel, fatigue was associated with the near-depletion of glycogen in white muscle...

The vastus lateralis muscles of eleven male elite sprinters (17-28 years) were investigated in order to examine the impact of high tension anaerobic muscular work on muscle fibre fine structure. In an attempt to reproduce the training regimen six subjects ran 20 repetitions of 25 s on a treadmill with 2 min 35 s in between, at a speed corresponding to 86% of their personal best 200 m time. PAS-stained sections of biopsies taken approximately 2 h after training generally indicated glycogen depletion in type 1 and type 2B fibres...

Soccer is a game that demands a combination of repeated maximal sprinting wit with 10 to 11km of moderate running, sometimes performed under extremely warm conditions. Over the course of a match, there is partial to near complete depletion of glycogen reserves in the leg muscles (depending on the extent of initial reserves and the level of competition), with a resultant decrease in physical performance. Blood glucose levels also fall, sometimes to values likely to cause a deterioration of both tactical thinking and cooperation between players (3...

The fine structural pattern of glycogen storage in resting and sprint-exercised human vastus lateralis muscle fibres of different types was analysed using ultrahistochemical methods. Three male subjects (31-36 years) performed 60 consecutive, supramaximal bouts of bicycle exercise, each starting every 1 min and having a duration of 8 s (including approximately 3 s of acceleration). The load was estimated to correspond to 200% of VO2-max. Five other subjects (22-27 years) constituted controls. Ultrathin sections stained with periodic acid-thiosemicarbazide-silver proteinate (PA-TSC-SP) clearly revealed a compartmental distribution of glycogen...

Skeletal muscle adapts to the stress of endurance and sprint exercise and training. There are 2 main types of skeletal muscle fibre--slow twitch (ST) and fast twitch (FTa, FTb, FTc). Exercise may produce transitions between FT and ST fibres. Sprint training has decreased the proportion of ST fibres and significantly increased the proportion of FTa fibres, while endurance training may convert FTb to FTa fibres, and increase the proportion of ST fibres (i.e. FTb----FTa----FTc----ST). However, the high proportion of ST fibres documented for elite endurance athletes may be simply the result of natural selection...

In an effort to determine what effect the degree of muscle glycogen depletion has on the rate of resynthesis, six male cyclists completed an exercise protocol that involved both one- and two-legged cycling. One leg completed 30 min of single-leg cycling, ten one-min sprints, and 30 min cycling with both legs. This resulted in a large degree of depletion (LD). The contralateral leg completed only 30 min of double-leg cycling and experienced a small amount of depletion (SD). Following the exercise, the subjects rested quietly for 6 h and were fed a 24% carbohydrate (CHO) solution every 20 min in order to achieve a CHO intake of 0...