Macronutrient intake and whole body protein metabolism following resistance exercise

The provision of carbohydrate (CHO) supplements following resistance exercise attenuated muscle protein (PRO) degradation (Roy et al. J. Appl. Physiol. 82:1882-1888, 1997). The addition of PRO may have a synergistic effect upon whole body protein balance by increasing synthesis (Biolo et al. Am. J. Physiol. 273:E122-E129, 1997). PURPOSE: To determine if the macronutrient composition of a postexercise beverage would alter muscle anabolism and/or catabolism following resistance exercise. METHODS: We provided isoenergetic CHO (1 g x kg(-1)) and CHO/PRO/FAT supplements and placebo (PL) immediately (t = 0 h) and 1 h (t = + 1 h) following resistance exercise (9 exercises/3 sets/80% 1 RM) to 10 young, healthy, resistance-trained males. Whole body leucine turnover was determined from L-[1-13C]leucine kinetics at approximately 4 h postexercise. RESULTS: No differences were observed for urinary 3-methylhistidine or urea nitrogen excretion between the trials. Leucine flux was significantly elevated at approximately 4 h postexercise for both CHO/PRO/FAT (177.59+/-12.68 micromol x kg(-1) x h(-1)) and CHO (156.18+/-7.77 micromol x kg(-1) x h(-1)) versus PL (126.32+/-10.51 micromol x kg(-1) x h(-1)) (P < 0.01). Whole body leucine oxidation was elevated at approximately 4 h for CHO/PRO/FAT (29.50+/-3.34 micromol x kg(-1) h(-1)) versus CHO (16.32+/-2.33 micromol x kg(-1) x h(-1)) (P < 0.01) and PL (21.29+/-2.54 micromol x kg(-1) x h(-1)) (P < 0.05). Nonoxidative leucine disposal (NOLD) was significantly elevated at approximately 4 h for both CHO/PRO/FAT (148.09+/-10.37 micromol x kg(-1) x h(-1)) and CHO (139.86+/-7.02 micromol x kg(-1) x h(-1)) versus PL (105.03+/-8.97 micromol x kg(-1) x h(-1)) (P < 0.01). CONCLUSIONS: These results suggest that consumption of either CHO or CHO/PRO/FAT immediately and 1 h following a resistance training bout increased NOLD as compared with a placebo.     

Muscle glycogen degradation during simulation of a fatiguing soccer match in elite soccer players examined noninvasively by 13C-MRS

PURPOSE: The purpose of this research project was to noninvasively determine individual muscle glycogen [Gly] degradation during a test intended to predict individual fatigue in intense soccer matches. METHODS: The [Gly] of the calf muscles of 17 elite soccer players [age = 17.4 +/- 0.8 (SD)] were measured with 13C-MRS before and after an alternating velocity test to exhaustion. Blood samples were taken before and 3 min after the test for determination of blood metabolites. RESULTS: Average muscle [Gly] was 135 +/- 53 mmol x (kg wet weight)(-1) before and 87 +/- 27 mmol x (kg wet weight)(-1) (P < 0.001) after exhaustion (42 +/- 25 min). There was a high correlation (r = 0.87, P < 0.0001) between muscle [Gly] at rest and net muscle [Gly] utilized. There was also a more moderate correlation (r = 0.62, P < 0.01) between net muscle [Gly] used and time to exhaustion during the soccer-specific test. There was some evidence of correlation (r = 0.42, P = 0.09) between resting [Gly] and time to exhaustion. Plasma lactate increased (P < 0.001) from 0.8 +/- 0.4 before the test to 2.5 +/- 1.0 mmol x L(-1) at exhaustion, whereas ammonia was raised (P < 0.0001) from 44.1 +/- 10.3 to 89.7 +/- 14.9 micromol x L(-1). Similarly, plasma free fatty acids were elevated (P < 0.0001) from 148 +/- 106 to 797 +/- 401 micromol x L(-1), and glycerol was increased (P < 0.0001) from 48.3 +/- 17.7 to 182.2 +/- 61.8 micromol x L(-1). Insulin levels (11.9 +/- 3.7 vs 11.7 +/- 4.8 microU x mL(-1)) remained the same. Creatine kinase levels increased (P < 0.0001) from 486 +/- 501 to 640 +/- 548 micromol x L(-1) after the test. CONCLUSIONS: We conclude that exhaustion during soccer-specific performance is related to the capacity to utilize muscle [Gly]. The results underline the importance of dietary counseling (glycogen loading and resynthesis strategies) and proper training to enhance the glycogen levels and glycogenolytic capacity of the players.     

Increased IGF mRNA in human skeletal muscle after creatine supplementation

PURPOSE: We hypothesized that creatine supplementation would facilitate muscle anabolism by increasing the expression of growth factors and the phosphorylation of anabolic signaling molecules; we therefore tested the responses of mRNA for IGF-I and IGF-II and the phosphorylation state of components of anabolic signaling pathways p70(s6k) and 4E-BP1 to a bout of high-intensity resistance exercise after 5 d of creatine supplementation. METHODS: In a double-blind cross-over design, muscle biopsies were taken from the m. vastus lateralis at rest and 3 and 24 h postexercise in subjects who had taken creatine or placebo for 5 d (21 g x d(-1)). For the first 3 h postexercise, the subjects were fed with a drink containing maltodextrin (0.3 g x kg(-1) body weight x h(-1)) and protein (0.08 g x kg(-1) body weight x h(-1)). RESULTS: After creatine supplementation, resting muscle expressed more mRNA for IGF-I (+30%, P < 0.05) and IGF-II (+40%, P = 0.054). Exercise caused an increase by 3 h postexercise in IGF-I (+24%, P < 0.05) and IGF-II (+48%, P < 0.05) and by 24 h postexercise in IGF-I (+29%, P < 0.05), but this effect was not potentiated by creatine supplementation. The phosphorylation states of p70(s6k) and 4E-BP1 were not affected by creatine at rest; phosphorylation of both increased (150-400%, P < 0.05) to similar levels under placebo and creatine conditions at 3 h postexercise plus feeding. However, the phosphorylation state of 4E-BP1 was higher in the creatine versus placebo condition at 24 h postexercise. CONCLUSION: The increase in lean body mass often reported after creatine supplementation could be mediated by signaling pathway(s) involving IGF and 4E-BP1.     

Effect of creatine loading on long-term sprint exercise performance and metabolism

PURPOSE: This study examined whether creatine (Cr) supplementation could enhance long-term repeated-sprint exercise performance of approximately 80 min in duration. METHODS: Fourteen active, but not well-trained, male subjects initially performed 10 sets of either 5 or 6 x 6 s maximal bike sprints, with varying recoveries (24, 54, or 84 s between sprints) over a period of 80 min. Work done (kJ) and peak power (W) were recorded for each sprint, and venous blood was collected preexercise and on four occasions during the exercise challenge. Muscle biopsies (vastus lateralis) were obtained preexercise as well as 0 min and 3 min postexercise. Subjects were then administered either 20 g.d-1 Cr.H2O (N = 7) or placebo (N = 7) for 5 d. Urine samples were collected for each 24 h of the supplementation period. Subjects were then retested using the same procedures as in test 1. RESULTS: Total work done increased significantly (P < 0.05) from 251.7 +/- 18.4 kJ presupplementation to 266.9 +/- 19.3 kJ (6% increase) after Cr ingestion. No change was observed for the placebo group (254.0 +/- 10.4 kJ to 252.3 +/- 9.3 kJ). Work done also improved significantly (P < 0.05) during 6 x 6 s sets with 54-s and 84-s recoveries and approached significance (P = 0.052) in 5 x 6 s sets with 24-s recovery in the Cr condition. Peak power was significantly increased (P < 0.05) in all types of exercise sets after Cr loading. No differences were observed for any performance variables in the placebo group. Resting muscle Cr and PCr concentrations were significantly elevated (P < 0.05) after 5 d of Cr supplementation (Cr: 48.9%; PCr: 12.5%). Phosphocreatine levels were also significantly higher (P < 0.05) immediately and 3 min after the completion of exercise in the Cr condition. CONCLUSION: The results of this study indicate that Cr ingestion (20 g.day-1 x 5 d) improved exercise performance during 80 min of repeated-sprint exercise, possibly due to an increased TCr store and improved PCr replenishment rate.     

Caffeine is ergogenic after supplementation of oral creatine monohydrate

PURPOSE: The purpose of this investigation was to assess the acute effects of caffeine ingestion on short-term, high-intensity exercise (ST) after a period of oral creatine supplementation and caffeine abstinence. METHODS: Fourteen trained male subjects performed treadmill running to volitional exhaustion (T(lim)) at an exercise intensity equivalent to 125% VO(2max). Three trials were performed, one before 6 d of creatine loading (0.3 g x kg x d(-1) baseline), and two further trials after the loading period. One hour before the postloading trials, caffeine (5 mg x kg(-1)) or placebo was orally ingested in a cross-over, double-blind fashion. Four measurements of rating of perceived exertion were taken, one every 30 s, during the first 120 s of the exercise. Blood samples were assayed for lactate, glucose, potassium, and catecholamines, immediately before and after exercise. RESULTS: Body mass increased (P < 0.05) over the creatine supplementation period, and this increase was maintained for both caffeine and placebo trials. There was no increase in the maximal accumulated oxygen deficit between trials; however, total VO(2) was significantly increased in the caffeine trial in comparison with the placebo trial (13.35 +/- 3.89 L vs 11.67 +/- 3.61 L). In addition, caffeine T(lim) (222.1 +/- 48.9 s) was significantly greater (P < 0.05) than both baseline (200.8 +/- 33.4 s) and placebo (198.3 +/- 45.4 s) T(lim). RPE was also lower at 90 s in the caffeine treatment (13.8 +/- 1.8 RPE points) in comparison with baseline (14.6 +/- 1.9 RPE points). CONCLUSION: As indicated by a greater T(lim), acute caffeine ingestion was found to be ergogenic after 6-d of creatine supplementation and caffeine abstinence.     

Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage

INTRODUCTION: The purpose of this study was to determine whether endurance cycling performance and postexercise muscle damage were altered when consuming a carbohydrate and protein beverage (CHO+P; 7.3% and 1.8% concentrations) versus a carbohydrate-only (CHO; 7.3%) beverage. METHODS: Fifteen male cyclists (mean (.-)VO(2peak) = 52.6 +/- 10.3 mL x kg x min) rode a cycle ergometer at 75% (.-)VO(2peak) to volitional exhaustion, followed 12 - 15 h later by a second ride to exhaustion at 85% (.-)VO(2peak). Subjects consumed 1.8 mL x kg BW of randomly assigned CHO or CHO+P beverage every 15 min of exercise, and 10 mL x kg BW immediately after exercise. Beverages were matched for carbohydrate content, resulting in 20% lower total caloric content per administration of CHO beverage. Subjects were blinded to treatment beverage and repeated the same protocol seven to 14 d later with the other beverage. RESULTS: In the first ride (75% (.-)VO(2peak)), subjects rode 29% longer (P < 0.05) when consuming the CHO+P beverage (106.3 +/- 45.2 min) than the CHO beverage (82.3 +/- 32.6 min). In the second ride (85% (.-)VO(2peak)), subjects performed 40% longer when consuming the CHO+P beverage (43.6 +/- 12.5 min) than when consuming the CHO beverage (31.2 +/- 8.7 min). Peak postexercise plasma CPK levels, indicative of muscle damage, were 83% lower after the CHO+P trial (216.3 +/- 122.0 U x L) than the CHO trial (1318.1 +/- 1935.6 U x L). There were no significant differences in exercising levels of (.-)VO(2), ventilation, heart rate, RPE, blood glucose, or blood lactate between treatments in either trial. CONCLUSION: A carbohydrate beverage with additional protein calories produced significant improvements in time to fatigue and reductions in muscle damage in endurance athletes. Further research is necessary to determine whether these effects were the result of higher total caloric content of the CHO+P beverage or due to specific protein-mediated mechanisms.     

Reducing the dose of combined caffeine and ephedrine preserves the ergogenic effect

BACKGROUND: Ingestion of a combination of 5 mg x kg(-1) caffeine (C), and 1 mg x kg(-1) ephedrine (E) was reported to have an ergogenic effect on high intensity aerobic exercise performance, but 25% of the subjects experienced vomiting and nausea while engaging in hard exercise after the treatment. The present study was undertaken to investigate whether reduced levels of C+E would alleviate the problem and maintain the ergogenic effect. METHODS: Twelve healthy untrained male subjects completed four randomized and double-blind, cycle ergometer trials to exhaustion at a power output equivalent to approximately 85% Vo2peak 1.5-2 hours after ingesting a placebo (P) or a mixture of C+E in the following doses: 5 mg x kg(-1) of C plus 0.8 mg x kg(-1) of E (CLE); 4 mg x kg(-1) of C plus 1 mg x kg(-1) of E (LCE); or 4 mg x kg of C plus 0.8 mg x kg(-1) of E (LCLE). Trials were separated by 1 wk. Venous blood samples were obtained and analyzed for caffeine and ephedrine levels 1.5 h post-drug ingestion. Vo2, Vco2, VE, and RQ were measured every minute throughout the exhaustion ride. Heart rate and perceived exertion (RPE) were also recorded every 5 min and at the end of the exercise session. RESULTS: Plasma levels of C and E immediately before the exhaustion ride were (mean +/- SD): 38.7+/-5.2 micromol x L(-1) C, 1.285+/-0.275 micromol x L(-1) E in the CLE trial; 33.2+/-5.8 micromol x L(-1) C, 1.462+/-0.283 micromol x L(-1) E in the LCE trial; 33.0+/-2.9 micromol x L(-1) C, 1.229+/-0.202 micromol x L(-1) E in the LCLE trial. The times to exhaustion for the treatment trials (CLE = 27.5+/-12.4 min, LCE = 27.6+/-10.9 min, LCLE = 28.2+/-9.3 min) were similar and were significantly greater than placebo (p = 17.0+/-3.0 min). The drugs did not affect Vo2, Vco2, or VE. Heart rates were significantly higher for the drug trials while RPE was lower compared with P. No incidents of nausea or vomiting occurred with the lowest dose of the C+E, LCLE. CONCLUSIONS: A lower dose of C+E resulted in an ergogenic effect similar in magnitude to that reported previously with a higher dose, and with a reduced incidence of negative side effects.     

The effects of ingesting a carbohydrate-electrolyte beverage 15 minutes prior to high-intensity exercise performance

The aim of this study was to examine the effect of ingesting a commercially available carbohydrate-electrolyte (CHO-E) solution on strenuous exercise performance. Ten apparently healthy male volunteers (Mean +/- SD; age 20 +/- 2 yrs; height 178 +/- 7 cm; body mass 77 +/- 10 kg; estimated VO(2 max) 56 +/- 3 ml x kg(-1) x min(-1) completed three experimental trials in random order separated by a minimum of 7 days. For each trial, subjects consumed (8 ml x kg(-1) body mass) either a CHO-E solution (6% carbohydrate, 50 mg Na/500 ml), a non-CHO-E placebo, or no fluid, 15 minutes prior to exercise. The exercise involved intermittent shuttle (20 m apart) running for 1 hr followed by an incremental shuttle running test to exhaustion. Subjects displayed longer exercise times when the CHO-E solution was ingested compared with placebo or no fluid groups (exercise time to exhaustion - CHO-E 649 +/- 95 s, vs. placebo 601 +/- 83 s, vs. no fluid 593 +/- 107 s, P < 0.05). There was a main effect for time for specific gravity of urine (P < 0.05 vs. postexercise, pooled data) and body mass (P < 0.05 vs. postexercise, pooled data). The main finding from this investigation indicates that drinking a CHO-E solution 15 minutes prior to exercise improves performance. This study has practical implications for those sports where drinking during activity is restricted.     

Plasma creatine kinase responses of 18- to 30-yr-old African-American men to eccentric exercise

PURPOSE: The primary aim was to describe the response of plasma creatine kinase (CK) activity in a sample of African-American men after a bout of eccentric exercise. The study also described signal intensity changes detected by MR in the musculature of the right lower leg. METHODS: Subjects were 20 male volunteers of African descent (age = 24 +/- 4 [mean +/- SD] yr). Each walked backward for 60 min at 3 km x h(-1) down a 23% grade. Venous blood was sampled before exercise, immediately (0 d) after and 1, 2, 4, and 7 d after exercise for plasma CK assay. Soreness in the plantar flexor muscles was evaluated in 18 subjects at selected times during the 7 d postexercise. Injury to the plantar flexor muscles was evaluated by magnetic resonance imaging (MRI). RESULTS: The subjects had high baseline plasma CK activity (187 +/- 127 IU x L(-1); 163 +/- 70 IU x L(-1) with one outlier excluded) compared with typical clinical norms. As a group, CK activity was increased (P < 0.05) 4 d (980 +/- 1331 IU L(-1)) and 7 d (1022 +/- 1031 IU L(-1)) postexercise, compared with preexercise. Eleven (55%) of the subjects had large, delayed increases in plasma CK activity ("hyperresponses"). As a group, the plasma CK response was similar to responses of comparison Caucasian subjects. All subjects reported delayed muscle soreness; there was no association between soreness and plasma CK. Every subject showed MRI evidence of injury to plantar flexor muscles postexercise but varying in degree and time course. Plasma CK activity correlated to MRI signal intensity (rho = 0.445). CONCLUSION: Results suggest that changes in plasma CK activity and skeletal muscle injury in African-American men after eccentric exercise do not differ from the responses of Caucasians.     

Voluntary muscle function after creatine supplementation in acute hypobaric hypoxia

PURPOSE: To determine whether creatine (Cr) supplementation improves muscle performance during exposure to acute hypobaric hypoxia. METHODS: Seven healthy men (28 +/- 6 yr, mean +/- SD) performed submaximal intermittent static knee contractions interspersed with maximal voluntary contractions (MVCs) every minute to exhaustion (approximately 50% of rested MVC force) in normoxia and hypobaric hypoxia (separated by 3 d) after supplementation with Cr (20 g.d(-1) for 7 d then 5 g.d(-1) for 4-7 d) or placebo (Pla) in a double-blind, randomized crossover study. A 5-wk period without supplementation separated treatments. Each test day, subjects performed two bouts (separated by 2 min) at their preset submaximal force, 32 +/- 4% rested MVC). RESULTS: Rested MVC force (860 +/- 66 N) and MVC force at exhaustion (396 +/- 27 N; 47 +/- 3% rested MVC) did not differ among treatments or environments (P > 0.05). For bout 1, endurance time was shorter in hypobaria (26 +/- 3 min) than normoxia (34 +/- 2 min) (P < 0.01), but did not differ between Cr (27 +/- 3 min) and Pla (33 +/- 3 min) (P > 0.05). MVC force returned to similar levels (P >0.05) in bout 2 after recovery in all four sessions (to approximately 615 N). For bout 2, endurance time also was shorter in hypobaria (7 +/- 1 min) than normoxia (9 +/- 1 min) (P < 0.03) but did not differ between Cr and Pla (P > 0.05). CONCLUSION: This study, which used an exercise model designed to impose the same target contraction force under all experimental conditions, found no effect of Cr on maximal force, muscle endurance, or recovery in normoxia or hypobaric hypoxia.     

Muscle damage and resting metabolic rate after acute resistance exercise with an eccentric overload

PURPOSE: The purpose of this investigation was to determine whether muscle damage caused from acute resistance exercise with an eccentric overload would influence resting metabolic rate (RMR) up to 72 h postexercise in resistance-trained (RT) and untrained (UT) subjects. METHODS: Nine RT and 9 UT male subjects (mean +/- SD; age = 20.7 +/- 2.1 yr; body mass = 79.0 +/- 1.4 kg; height = 178.4 +/- 3.1 cm; and body fat = 10.2 +/- 1.6%) were measured for RMR, creatine kinase concentration ([CK]), and rating of perceived muscle soreness (RPMS) on five consecutive mornings. To induce muscle damage, after the measurements on day 2, each subject performed leg presses that emphasized the eccentric movement for 8 sets at his six-repetition maximum (6-RM). RESULTS: Compared with baseline, the RMR (kJ x d(-1) and kJ x kg FFM(-1) x h(-1) was significantly elevated for RT and UT at 24 h and 48 h postexercise. From 24 h to 48 h to 72 h postexercise, RMR significantly decreased within both groups. The UT group had a significantly higher RMR at 24 h (9,705.4 +/- 204.5 kJ x d(-1)) and 48 h postexercise (8,930.9 +/- 104.4 kJ x d(-1)) when compared with the RT group (9,209.3 +/- 535.3 and 8,601.7 + 353.7 kJ x d(-1)). Both [CK] and RPMS showed a similar time course. CONCLUSION: There was a significantly higher [CK] for the UT group at 24 h postexercise (320.4 +/- 20.1 U x L(-1)) and for both [CK] and RPMS at 48 h (1,140.3 +/- 37.1 U x L(-1) and 4.4 +/- 0.5, respectively) and 72 h postexercise (675.9 +/- 41.7 U x L(-1) and 1.67 +/- 0.5, respectively) when compared with the RT group (24 h, 201.9 +/- 13.4 U x L(-1); 48 h, 845.4 +/- 30.7 U x L(-1) and 3.7 +/- 0.5: and 72 h postexercise, 420.2 +/- 70.2 U x L(-1) and 0.89 +/- 0.3). These data indicate that eccentrically induced muscle damage causes perturbations in RMR up to 48 h postexercise.     

Prior heavy exercise enhances performance during subsequent perimaximal exercise

PURPOSE: To test the hypothesis that prior heavy exercise increases the time to exhaustion during subsequent perimaximal exercise. METHODS: Seven healthy males (mean +/- SD 27 +/- 3 yr; 78.4 +/- 0.7 kg) completed square-wave transitions from unloaded cycling to work rates equivalent to 100, 110, and 120% of the work rate at VO2peak (W-[VO2peak) after no prior exercise (control, C) and 10 min after a 6-min bout of heavy exercise at 50% Delta (HE; half-way between the gas exchange threshold (GET) and VO2peak), in a counterbalanced design. RESULTS: Blood [lactate] was significantly elevated before the onset of the perimaximal exercise bouts after prior HE (approximately 2.5 vs approximately 1.1 mM; P < 0.05). Prior HE increased time to exhaustion at 100% (mean +/- SEM. C: 386 +/- 92 vs HE: 613 +/- 161 s), 110% (C: 218 +/- 26 vs HE: 284 +/- 47 s), and 120% (C: 139 +/- 18 vs HE: 180 +/- 29 s) of W-VO2peak, (all P < 0.01). VO2 was significantly higher at 1 min into exercise after prior HE at 110% W-VO2peak (C: 3.11 +/- 0.14 vs HE: 3.42 +/- 0.16 L x min(-1); P < 0.05), and at 1 min into exercise (C: 3.25 +/- 0.12 vs HE: 3.67 +/- 0.15; P < 0.01) and at exhaustion (C: 3.60 +/- 0.08 vs HE: 3.95 +/- 0.12 L x min(-1); P < 0.01) at 120% of W-VO2peak. CONCLUSIONS: This study demonstrate that prior HE, which caused a significant elevation of blood [lactate], resulted in an increased time to exhaustion during subsequent perimaximal exercise presumably by enabling a greater aerobic contribution to the energy requirement of exercise.     

Montelukast has no ergogenic effect on cycle ergometry in cold temperature

PURPOSE: To examine the effects of a single 10-mg dose of ML on physical performance in EIB- and EIB+ athletes. METHODS: Twenty-four male college ice hockey players performed two 6-min maximal work accumulation bouts on an electronically braked cycle ergometer in subfreezing conditions (-2.5 +/- 0.4 degrees C) 6-8 h after either ML or placebo (PL) to obtain total work accumulated (kJ); subjects were evaluated for EIB after each exercise trial. RESULTS: Eight (33%) subjects were identified as EIB+ (23.5 +/- 13.35% fall in FEV1); 16 were EIB- (1.8 +/- 3.03% fall in FEV1). ML provided an approximately 50% protection against postexercise fall in FEV1. No significant differences in kJ were found between PL and ML trials for pooled subjects (95.3 +/- 13.69 and 94.8 +/- 13.27 kJ, respectively), EIB- subjects (99.6 +/- 13.26 and 99.0 +/- 11.81 kJ, respectively), or EIB+ subjects (86.8 +/- 10.67 and 86.5 +/- 12.72 kJ, respectively). Total work accumulated for EIB- subjects was significantly greater than for EIB+ subjects for both PL and ML (P < 0.05). CONCLUSION: A single 10-mg dose of ML had no ergogenic effect for EIB- and EIB+ subjects performing short-duration high-intensity exercise in subfreezing temperature, supporting the use of ML as EIB prophylaxis during international sport competition.     

Fatigue after submaximal intensive stretch-shortening cycle exercise

OBJECTIVE: The aim of the present study was to examine some sites of neuromuscular fatigue after submaximal intensity stretch-shortening cycle exercise. METHODS: Twelve male subjects performed consecutive sledge jumps at 60% of maximal height until exhaustion (mean duration 443.7 s +/- 304.9 s, mean +/- SD). RESULTS: During the exercise, the blood lactate increased from 1.8 +/- 0.6 mmol x L(-1) (before exercise) to 6.1 +/- 1.7 mmol x L(-1) (P < 0.001) and serum creatine-kinase from 248 +/- 142 IU x L(-1) to 584 +/- 344 IU x L(-1) (P < 0.001). Electrical stimulation of the vastus lateralis and quadriceps femoris muscles to induce isometric knee extension resulted in decreased peak torque during single and double twitch after workout (from 22.1 +/- 6.3 Nm to 17.3 +/- 8.0 Nm, P < 0.05, and from 96.6 +/- 15.4 Nm to 76.2 x 19.8 Nm, P < 0.001, respectively), whereas there were no significant changes in contraction and relaxation times. Torque during 20-Hz stimulation decreased significantly (from 23.7 +/- 9.2 to 16.1 +/- 7.8 Nm, P < 0.01) but not at 100-Hz stimulation. During maximal voluntary isometric knee extensions, the rate of torque development was significantly (P < 0.01) more impaired than maximal torque (from 1619 +/- 390 Nm x s(-1) to 1,004 +/- 360 Nm x s(-1) and from 185 +/- 30.7 Nm to 151 +/- 32.3 Nm, respectively, both P < 0.001). At the same time, the muscle activation level increased by 15.8 +/- 24.1% (P < 0.05). The mean EMG amplitude of vastus lateralis during MVC increased by 34.9 +/- 39.2% (P > 0.05). CONCLUSION: It was concluded that after submaximal stretch-shortening exercise, the low-frequency fatigue occurred, very likely caused by lower Ca2+ release per single action potential.     

Airway cell composition at rest and after an all-out test in competitive rowers

PURPOSES: This study was designed to assess: a) whether rowing affects airway cell composition, and b) the possible relationship between the degree of ventilation during exercise and airway cells. SUBJECTS AND METHODS: In nine young, nonasthmatic competitive rowers (mean age +/- SD: 16.2 +/- 1.0 yr), induced sputum samples were obtained at rest and shortly after an all-out rowing test over 1000 m (mean duration: 200 +/- 14 s), during which ventilatory and metabolic variables were recorded breath-by-breath (Cosmed K4b, Italy). RESULTS: At rest, induced sputum showed prevalence of neutrophils (60%) over macrophages (40%); after exercise, total cell and bronchial epithelial cell (BEC) counts tended to increase. In the last minute of exercise, mean VE was 158.0 +/- 41.5 L x min(-1), and VO2 x kg(-1) 62 +/- 11 mL x min(-1). Exercise VE correlated directly with postexercise total cell (Spearman rho: 0.75, P < 0.05) an dmacrophage (rho: 0.82, P < 0.05) counts. A similar trend was observed for exercise VE and changes in BEC counts from baseline to postexercise (rho: 0.64, P = 0.11). Exercise VE did not correlate with airway neutrophil counts at rest or after exercise. Expression of adhesion molecules by airway neutrophils, macrophages, and eosinophils decreased after the all-out test. CONCLUSION: Similar to endurance athletes, nonasthmatic competitive rowers showed increased neutrophils in induced sputum compared with values found in sedentary subjects. The trend toward increased BEC postexercise possibly reflected the effects of high airflows on airway epithelium. Airway macrophages postexercise were highest in rowers showing tile most intense exercise hyperpnea, suggesting early involvement of these cells during exercise. However, the low expression of adhesion molecules by all airway cell types suggests that intense short-lived exercise may be associated with a blunted response of airway cells in nonasthmatic well-trained rowers.     

Intravenous versus oral rehydration during a brief period: responses to subsequent exercise in the heat

PURPOSE: The purpose of this study was to assess whether a brief period (20 min) of intravenous (i.v.) fluid rehydration versus oral rehydration differentially affects cardiovascular, thermoregulatory, and performance factors during exhaustive exercise in the heat. METHODS: Following dehydration (-4% of body weight), eight nonacclimated highly trained cyclists (age = 23.5 +/- 1.2 yr; VO2peak = 61.4 +/- 0.8 mL x kg x min(-1); body fat = 13.5 +/- 0.6%) rehydrated and then cycled at 70% VO2peak to exhaustion in 37 degrees C. Rehydration (randomized, cross-over design) included: 1) CONTROL (no fluid), 2) DRINK (oral rehydration, 0.45% NaCl) equal to 50% of prior dehydration, and 3) IV (intravenous rehydration, 0.45% NaCl), equal to 50% of prior dehydration. Thus, in the DRINK and IV treatments subjects began exercise (EX) at -2% of body weight. RESULTS: Exercise time to exhaustion was not different (P = 0.07) between DRINK (34.9 +/- 4 min) and IV (29.5 +/- 3.5 min), but both were significantly (P < 0.05) longer than CONTROL (18.9 +/- 2.7 min). Plasma volume was better (P < 0.05) restored during IV than CONTROL and DRINK at pre-exercise and 5 min EX, but different (P < 0.05) from only CONTROL at 15 min EX. Plasma lactate during DRINK was lower (P < 0.05) than IV at 15 min EX and postexercise. Heart rate during CONTROL was greater (P < 0.05) than DRINK and IV from 0-8 min EX, and greater (P < 0.05) than DRINK from 10-14 min EX. Rectal temperature during DRINK was less (P < 0.05) than IV from 0-24 min EX. Mean weighted skin temperature during DRINK was less (P < 0.05) than IV from 4-12 min EX. CONCLUSIONS: Thus, despite no statistically significant performance differences between DRINK and IV, it appears that certain physiological parameters were better maintained in the DRINK trial, and the trend toward performance differences may be important to elite athletes.     

Creatine supplementation--part I: performance, clinical chemistry, and muscle volume

PURPOSE: Our purpose was to study the effects and side effects of creatine (Cr) supplementation on high-intensity, short-term muscle work, on biochemical parameters related to Cr metabolism in blood and urine, and on muscle volume of the lower limb muscles. METHODS: A cycling ergometer was used in a double-blind, cross-over study on 10 well-trained male physical education students to measure physical performance with 10 repetitive ergometer sprints (6-s duration, 30-s rest) before and after supplementation (5 d, 20 g x d(-1), washout period 61 +/- 8 d, mean +/- SEM, minimum 28 d) with Cr or placebo. Before and after supplementation, blood and urine were taken and the muscle volume of the lower limb was determined by magnetic resonance imaging (MRI). RESULTS: A significant (P < 0.05) increase in performance (+7%) at the end [4-6 s] of the later sprints (4-7 and 8-10) was observed combined with a lower production of blood lactate (-1 mmol x L(-1)) with Cr supplementation. The concentration of Cr was increased significantly in urine (P < 0.001) and serum (P = 0.005), whereas creatinine (Crn) was increased in serum (P < 0.001). Crn in urine and Crn clearance did not change significantly with Cr intake. There were no significant changes in the analyzed blood enzyme activities. A significant gain of body weight (pre-Cr 76.5 +/- 1.7 kg to 77.9 +/- 1.7 kg post-Cr) with Cr supplementation was measured, but no accompanying increase of muscle mass in a limited volume of the lower limb was observed by MRI. CONCLUSION: Cr supplementation is effective in improving short-term performance, and the methods used show no detrimental side effects with this supplementation protocol.     

Effect of creatine ingestion after exercise on muscle thickness in males and females

Muscles exercised before creatine (Cr) supplementation have a greater elevation of intramuscular Cr than nonexercised muscles. PURPOSE: To determine whether preferential increase of muscle thickness could be achieved by ingesting Cr immediately after exercise of specific muscles over 6 wk. Another purpose was to determine if the increase in lean tissue mass (LTM) with Cr supplementation is greater in males than females. METHODS: Subjects randomly assigned to Cr (six males, five females, 0.2 g Cr x kg(-1)) and placebo (PL; five males, five females) performed single-limb training with one side of the body two times per week and with the opposite limbs two times per week. Cr was consumed after training of one side of the body and PL after training the opposite side. Subjects on PL always consumed PL after exercise. Elbow flexors and knee extensors muscle thickness, LTM, fat, and bone mass, and single-limb bench and leg press one-repetition maximum (1-RM) were assessed before and after 6 wk. RESULTS: Within the Cr group, elbow flexors muscle thickness increased more in the limbs trained on days Cr was supplemented compared with limbs trained on days PL was supplemented (P < 0.02). All other measures changed to a similar extent between limbs. Males on Cr had the greatest increase in LTM (P < 0.05) with no difference between females on Cr and PL. Bench press 1-RM increased more in Cr than PL groups (P < 0.01). All other measures changed to a similar extent between groups. Males increased bone mass (P < 0.01) with no effect of Cr supplementation. CONCLUSION: Supplementing with Cr after training of the arms resulted in greater increase in muscle thickness of the arms. Males have a greater increase in LTM with Cr supplementation than females.     

Effect of an isocaloric carbohydrate-protein-antioxidant drink on cycling performance

PURPOSE: Fourteen male cyclists were studied to compare the effect of carbohydrate-protein-antioxidant beverage (CHOPA) to an isocaloric carbohydrate-only (CHO) beverage on time to fatigue and muscle damage. METHODS: Subjects performed two sets of rides to exhaustion on a cycle ergometer. In each set, the first ride was performed at 70% VO2peak, and the second was performed 24 h later at 80%. CHO or CHOPA was consumed every 15 min during exercise and immediately afterward. Plasma CK and LDH and muscle soreness were measured pre- and postexercise. RESULTS: Time to fatigue was not different between CHO and CHOPA at 70% VO2peak (95.8 +/- 29.7 vs 98.1 +/- 28.7 min), 80% VO2peak (42.3 +/- 18.6 vs 42.9 +/- 21.8 min), or total performance time (138.1 +/- 39.3 vs 140.9 +/- 43.7 min). Postexercise CK was increased (P < 0.05) from baseline in CHO (203 +/- 120 vs 582 +/- 475 U.L(-1)) but not with CHOPA (188 +/- 119 vs 273 +/- 169 U.L(-1)). Similarly, LDH values increased over baseline in CHO (437 +/- 46 vs 495 +/- 64 U.L(-1)) but not with CHOPA (432 +/- 40 vs 451 +/- 43 U.L(-1)). Postexercise CPK and LDH were higher after the CHO trial than after the CHOPA trial. Median postexercise muscle soreness was higher in CHO (3.0 +/- 5.0) than with CHOPA (1.0 +/- 3.0). CONCLUSION: No differences in time to fatigue were observed between the beverages, despite lower total carbohydrate content in the CHOPA beverage. The CHOPA beverage attenuated postexercise muscle damage, as evidenced by CK and LDH values, compared with an isocaloric CHO beverage.