Short-term Intense Exercise Research Articles

Caffeine and Performance

Caffeine ingestion (3-9 mg/kg body weight) prior to exercise increases performance during prolonged endurance exercise and short-term intense exercise lasting approximately 5 min in the laboratory. These results are generally reported in well-trained elite or recreational subjects. However, there is a lack of well-controlled field studies to determine the applicability of laboratory results to the athletic world. Caffeine does not appear to enhance performance during incremental exercise tests lasting 8-20 min and during sprinting lasting less than 90 s, although research examining sprinting is rare. In addition, the mechanisms responsible for any improvement in endurance and short-term exercise have not been clearly established. The ergogenic effects of caffeine are present with urinary caffeine levels that are below the limit of 12 micrograms/ml allowed by the International Olympic Committee, which raises serious ethical issues regarding the use of caffeine to improve athletic performance. One solution would be to add caffeine to the list of banned substances, thereby requiring athletes to abstain from caffeine ingestion 48-72 hr prior to competition.

The effect of high-intensity training on purine metabolism in man.

The effect of intermittent high-intensity training on the activity of enzymes involved in purine metabolism and on the concentration of plasma purines following acute short-term intense exercise was investigated. Eleven subjects performed sprint training three times per week for 6 weeks. Muscle biopsies for determination of enzyme activities were obtained prior to and 24 h after the training period. After training, the activity of adenosine 5'-phosphate (AMP) deaminase was lower (P < 0.001) whereas the activities of hypoxanthine phosphoribosyl transferase (HPRT) and phosphofructokinase were significantly higher compared with pre-training levels. The higher activity of HPRT with training suggests an improved potential for rephosphorylation of intracellular hypoxanthine to inosine monophosphate (IMP) in the trained muscle. Before and after the training period the subjects performed four independent 2-min tests at intensities from a mean of 106 to 135% of VO2max. Venous blood was drawn prior to and after each test. The accumulation of plasma hypoxanthine following the four tests was lower following training compared with prior to training (P < 0.05). The accumulation of uric acid was significantly lower (46% of pre-training value) after the test performed at 135% of VO2max (P < 0.05). Based on the observed alterations in muscle enzyme activities and plasma purine accumulation, it is suggested that high intensity intermittent training leads to a lower release of purines from muscle to plasma following intense exercise and, thus, a reduced loss of muscle nucleotides.

Investigation of metabolic myopathies by P-31 MRS using a standardized rest-exercise-recovery protocol: a survey of 800 explorations

A standardized P-31 magnetic resonance spectroscopy (MRS) protocol for the exploration of muscle metabolism by P-31 MRS in trained and untrained subjects as well as in patients with intolerance to exercise has been developed to meet the specific requirements of a clinical environment. This protocol is based on a short-term intense exercise which is very informative and well accepted by volunteers and patients. Invariant metabolic parameters have been established to characterize the normal metabolic response to the protocol. As a matter of fact, the comparative analysis of normal and diseased muscle remains a major requirement to further define metabolic events surrounding muscle contraction and the metabolic anomalies underlying diseases. Deviations from normality can be directly interpreted in terms of specific pathologies in some favourable cases. In most cases, P-31 MRS provides valuable information which has to be processed in conjunction with traditional invasive biochemical, electrophysiological and histoenzymological tests. For malignant and exertional hyperthermias, P-31 MRS constitutes a diagnostic tool with 100% sensitivity, as compared to contracture tests. P-31 MRS has proved particularly useful in the therapeutic follow-up of palliative therapies (coenzyme Q treatment of mitochondriopathies) and in family investigations. It is now an accepted diagnostic tool in the array of tests which are used to characterize muscle disorders in clinical routine. This procedure is already approved for reimbursement in the public hospital system in Marseille, France.

Glycolysis and Swimming Performance in Juvenile American Alligators

Glycolysis and Swimming Performance in Juvenile American Alligators

Carbohydrate metabolism in skeletal muscle: an update of current concepts.

We have reviewed carbohydrate metabolism in skeletal muscle with an emphasis on recent information. In this review a significant number of points have been made. These are summarized below. 1. CP and glycogen are concomitantly metabolized during short-term (less than or equal to 10 s) intense exercise. 2. Both epinephrine and contractile activity regulate glycogen use in muscle. 3. Glycogen sparing during exercise is promoted by fatty acids and probably glucose. 4. Glycogenesis increases during exercise in exercising muscle. 5. Ingested glucose is easily metabolized during exercise. 6. The heterogeneity in glucose uptake among muscles at rest and during exercise is likely not caused by blood flow differences per se. 7. Insulin binding, glucose transporters, glucose uptake, and glycogenesis are greater in ST than in FT muscles. 8. Acute changes in glucose metabolism are not always attributable to concomitant changes in insulin binding to its receptor. 9. Contractile activity alone will increase glucose uptake in muscle, and insulin is not required. 10. Insulin and contractile effects on glucose uptake are additive, suggesting that these stimuli mobilize different pools of glucose transporters. 11. Glycogen loss occurs in exercising and non-exercising muscle; therefore this substrate is not an appropriate index of muscle contractile activity. 12. Carbohydrate mobilization does not appear to be strictly determined by need for this substrate nor by the rate of muscle metabolism. 13. Glyconeogenesis from lactate occurs in ST and FT muscles and is regulated by pH.

Circadian variation in blood pressure responses to muscular exercise.

Abstract The physiological responses to strenuous steady-rate exercise are known to vary with time of day. Less well understood are the acute reactions to abrupt short-term all-out muscular efforts. This study examined circadian variation in blood pressure responses to short-term intense exercise. Twelve males participated in an experiment that involved performance of maximal muscular efforts at six times of the day. The time points were equally spaced throughout the day and for each subject the tests were conducted within a 2-week period. Systolic and diastolic blood pressures were measured pre-exercise using sphygmomanometry and body temperature was recorded with a rectal probe. Muscle function tests consisted of (1) three slow and three fast isokinetic movements, knee extensions performed under both concentric and eccentric conditions; (2) a 20s maximal isometric contraction, and (3) a 60s fatigue loading with concentric and eccentric contractions. Blood pressures were again measured immediately after ...

Relationships between muscle lactate accumulation and surface EMG activities during isokinetic contractions in man.

In order to investigate the relationship between metabolic state and myoelectrical activity in working muscle during short term intense exercise, eleven healthy males performed isokinetic knee extensions at an angular velocity of 180 deg X sec-1 for 30 and 60 s. The median frequency (MF) of the surface electromyogram (EMG) recorded from vastus lateralis was decreased while the time lag of torque production after the onset of electrical activity (EMD) was increased during exercise. These changes (MF and EMD) corresponded well to muscle lactate accumulation in the same muscle. Over the exercise period, the integrated EMG/knee extension peak torque ratio (E/T ratio) was increased, which indicated a decrease in the efficiency of electrical activity. It was concluded that the changes in the frequency components of the EMG and in the contractile property of the muscle during short term intense exercise correlated with lactate accumulation in the identical muscle, and that the decrease in efficiency of the electrical activity in the muscle suggested peripheral fatigue.

Decreased hypothalamic gonadotropin-releasing hormone secretion in male marathon runners.

Hypogonadotropic hypogonadism due to a deficiency in hypothalamic gonadotropin-releasing hormone is common in female athletes ("hypothalamic amenorrhea"). It is not known, however, whether a similar phenomenon occurs in male athletes. We investigated the integrity of the hypothalamic-pituitary-gonadal axis in six highly trained male marathon runners (who were running 125 to 200 km per week). The mean (+/- SEM) frequency of spontaneous luteinizing hormone pulses was diminished in the runners, as compared with healthy controls (2.2 +/- 0.48 vs. 3.6 +/- 0.24 pulses per eight hours, P less than 0.05). The amplitude of the pulses was also low in the runners (0.9 +/- 0.24 vs. 1.6 +/- 0.15 mlU per milliliter; P less than 0.05), and the responses of luteinizing hormone to gradually increasing doses of exogenous gonadotropin-releasing hormone were decreased. Plasma testosterone levels were similar in the two groups and increased equally in response to an intramuscular injection of 2000 units of human chorionic gonadotropin. During short-term intense physical exercise (a treadmill run at 72 percent of maximal oxygen consumption for two hours), the plasma gonadotropin levels in the athletes remained stable, but significant elevations in plasma levels of cortisol, prolactin, and testosterone occurred. We conclude that highly trained male athletes, like their female counterparts, may have a deficiency of hypothalamic gonadotropin-releasing hormone. This condition may be caused by the prolonged, repetitive elevations of gonadal steroids and other hormones known to suppress gonadotropin-releasing hormone secretion that are elicited by their daily exercise.

Effects of exogenous catecholamines and exercise on plasma magnesium concentrations.

Catecholamines and physical exercise are known to influence the metabolism of several minerals in man, but the effects on magnesium (Mg) have been scarcely investigated. In the present study, infusion of adrenaline (5 micrograms/min for 30 min followed by 10 micrograms/min for 30 minutes) significantly reduced the plasma Mg levels in healthy males. This effect was abolished by simultaneous infusion of propranolol. Noradrenaline had no such effect. In order to stimulate endogenous catecholamine release healthy males carried out physical exercise in four different ways: ergometer bicycling at maximum load until exhaustion with and without oral beta-blockade, ergometer bicycling with stepwise increasing load until exhaustion, isokinetic maximal exercise with one leg, with blood sampling both from the venous effluent of the exercising leg and the opposite resting arm and long-term (60 min) steady state ergometer bicycling at approximately 65% of estimated maximum capacity. During short-term (less than 20 min) intense exercise (i.e. experiments 1-3) the plasma Mg concentrations were increased. This was probably due to a reduction of plasma volume and to an influx of Mg to the vascular pool. During long-term steady state exercise (experiment 4) the Mg levels were not significantly affected but decreased during the first hour of recovery. These results suggest that both the beta-adrenergic system and muscular activity by itself affect Mg homeostasis.

NADH in human skeletal muscle during short-term intense exercise.

The influence of high-intensity bicycle exercise on the redox level and lactate accumulation in skeletal muscle (m. quadriceps femoris) of man has been investigated. Six subjects exercised to exhaustion at a load corresponding to 100% VO2max. Muscle content of NADH, determined by the bioluminescence technique, increased from (means +/- SEM) 0.089 +/- 0.007 mmol/kg dry wt. at rest to 0.190 +/- 0.031 after 2 min of exercise (P less than 0.05) and to 0.213 +/- 0.021 at exhaustion (P less than 0.05). Values after 2 min exercise and at exhaustion were not statistically different (P greater than 0.05). Muscle lactate was increased 13-fold after 2 min of exercise and 22-fold at exhaustion as compared to the resting value. After 10 min recovery NADH was restored back to the pre-exercise level whereas muscle lactate was still elevated. The increase of muscle NADH during exercise is in contrast to earlier studies on isolated animal muscles, where an oxidation of NADH was observed during contractions. The difference might be due to the experimental model (isolated muscle vs. in vivo) or to the analytical method (qualitative data by reflectance fluorimetri from the surface of intact muscle vs. quantitative data from muscle extracts). Calculations of the cytosolic NADH concentration from the lactate dehydrogenase equilibrium show that 95% or more of the NADH is confined to the mitochondrial compartment. The observed increase of muscle NADH therefore imply that the redox potential of the mitochondria is decreased during intense exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Recovery from short term intense exercise: its relation to capillary supply and blood lactate concentration.

Muscle force recovery from short term intense exercise was examined in 16 physically active men. They performed 50 consecutive maximal voluntary knee extensions. Following a 40-s rest period five additional maximal contractions were executed. The decrease in torque during the 50 contractions and the peak torque during the five contractions relative to initial torque were used as indices for fatigue and recovery, respectively. Venous blood samples were collected repeatedly up to 8 min post exercise for subsequent lactate analyses. Muscle biopsies were obtained from m. vastus lateralis and analysed for fiber type composition, fiber area, and capillary density. Peak torque decreased 67 (range 47-82%) as a result of the repeated contractions. Following recovery, peak torque averaged 70 (47-86%) of the initial value. Lactate concentration after the 50 contractions was 2.9 +/- 1.3 mmol X 1(-1) and the peak post exercise value averaged 8.7 +/- 2.1 mmol X 1(-1). Fatigue and recovery respectively were correlated with capillary density (r = -0.71 and 0.69) but not with fiber type distribution. A relationship was demonstrated between capillary density and post exercise/peak post exercise blood lactate concentration (r = 0.64). Based on the present findings it is suggested that lactate elimination from the exercising muscle is partly dependent upon the capillary supply and subsequently influences the rate of muscle force recovery.

Limb circulation during arm and leg exercise in supine position.

ArticleLimb circulation during arm and leg exercise in supine position.U Freyschuss, and T StrandellU Freyschuss, and T StrandellPublished Online:01 Aug 1967https://doi.org/10.1152/jappl.1967.23.2.163MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByInter-Modal Comparisons of Acute Energy Expenditure during Perceptually Based Exercise in Obese AdultsJournal of Nutritional Science and Vitaminology, Vol. 54, No. 1Aging, Exercise, and Limb Vascular Heterogeneity in HumansMedicine & Science in Sports & Exercise, Vol. 38, No. 10Heterogeneous limb vascular responsiveness to shear stimuli during dynamic exercise in humansD. Walter Wray, Abhimanyu Uberoi, Lesley Lawrenson, and Russell S. 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Mathematical modelEuropean Journal of Applied Physiology and Occupational Physiology, Vol. 46, No. 2Energetics of muscular exercise20 June 2005Gas exchanges during exercise in normoxia and hyperoxiaRespiration Physiology, Vol. 33, No. 2Oxygen uptake transients at the onset and offset of arm and leg workRespiration Physiology, Vol. 30, No. 1-2Prolonged exercise in prepubertal boysEuropean Journal of Applied Physiology and Occupational Physiology, Vol. 35, No. 4Relationships of femoral venous [K+], [H+], $$P_{o_2 } $$ , osmolality, and [orthophosphate] with heart rate, ventilation, and leg blood flow during bicycle exercise in athletes and non-athletes, osmolality, and [orthophosphate] with heart rate, ventilation, and leg blood flow during bicycle exercise in athletes and non-athletesEuropean Journal of Applied Physiology and Occupational Physiology, Vol. 35, No. 3Lactate content and pH in muscle samples obtained after dynamic exercisePfl�gers Archiv European Journal of Physiology, Vol. 367, No. 2Lactate oxidation by skeletal muscle during sustained contraction in vivoPfl�gers Archiv European Journal of Physiology, Vol. 366, No. 2-3Lactic acidosis and renal phosphoenolpyruvate carboxykinase activity during exerciseBiochemical Medicine, Vol. 14, No. 4Comparison between Arm and Leg Exercise in Women and Men14 February 2011 | Scandinavian Journal of Clinical and Laboratory Investigation, Vol. 35, No. 8ACTIVATION OR UNBLOCKING OF T LYMPHOCYTESThe Lancet, Vol. 304, No. 7886MECHANISM OF LACTIC ACIDOSISThe Lancet, Vol. 304, No. 7886The lactate/pyruvate ratio in muscular work and following injection of lactate in manPfl�gers Archiv European Journal of Physiology, Vol. 342, No. 4Lactate and Oxygen Debt: An IntroductionTurn Over of 14C-L(+)-Lactate in Human Skeletal Muscle During ExerciseIn situ oxidation of lactate by skeletal muscle during intermittent exercise19 October 2001 | FEBS Letters, Vol. 11, No. 1Oxygen debt: Involvement of the Cori cycleInternationale Zeitschrift f�r Angewandte Physiologie Einschlie�lich Arbeitsphysiologie, Vol. 28, No. 2The effect of training and various work loads on the lactacid-alactacid oxygen debt response of exercising dogsInternationale Zeitschrift f�r Angewandte Physiologie Einschlie�lich Arbeitsphysiologie, Vol. 28, No. 2 More from this issue > Volume 23Issue 2August 1967Pages 163-70 https://doi.org/10.1152/jappl.1967.23.2.163PubMed6031184History Published online 1 August 1967 Published in print 1 August 1967 Metrics