An upper arm model for simulated weightlessness.

This investigation examined the effects of 4 weeks of non-dominant arm unloading on the functional and structural characteristics of the triceps brachii muscle of six normo-active college-age males (age: 23 +/- 1 years, height: 176 +/- 4 cm, weight: 76 +/- 6 kg). The primary intention of this study was to determine if arm unloading is an effective analogue for simulating the effects of weightlessness on human skeletal muscle. Subjects were tested 2-3 days preceding unloading in a standard arm sling and following removal of the sling. The sling was worn during waking hours to unload the arm. Subjects were allowed to remove the sling during sleep and bathing. Torque production (Nm) during maximal isometric extension at 90 degrees significantly declined (P < 0.05) in response to unloading (53.93 +/- 5.07 to 47.90 +/- 5.92; 12%). There was no significant change (P > 0.05) in the force-velocity attributes of the triceps over the other measured velocities (1.05, 1.57, 2.09, 3.14, 4.19, 5.24 rad.s-1). Cross-sectional muscle area (CSA) of the upper arm was smaller (44.3 +/- 2.7 to 42.4 +/- 2.5 cm2; 4%) following 4 weeks of unloading (P < 0.05). Histochemical analysis of individual muscle fibres demonstrated reductions in fibre CSA of 27 and 18% for type I and type II fibres, respectively. However, these changes were not statistically significant. Electrophoretic analysis of muscle samples revealed a significant increase (40 +/- 7 to 58 +/- 4%, pre- and post-, respectively) in myosin heavy chain (MHC) type II isoforms following unloading. Reductions in type I MHC isoform composition failed to reach statistical significance (P < 0.08). Amplitude of the integrated electromyographic (IEMG) signal during maximal isometric contraction of the long head of the triceps decreased by 21% in response to the 4-week unloading period (P < 0.05). The changes in triceps, muscle structure and function found with arm unloading are similar in magnitude and direction to data obtained from humans following exposure to real and simulated weightlessness. These findings demonstrate that arm unloading produces some of the effects seen in response to weightlessness in muscles of the upper arm and provides potential for an additional model to simulate the effects of microgravity on human skeletal muscle.

Performance and muscle fiber adaptations to creatine supplementation and heavy resistance training.

PURPOSE: The purpose of this study was to examine the effect of creatine supplementation in conjunction with resistance training on physiological adaptations including muscle fiber hypertrophy and muscle creatine accumulation. METHODS: Nineteen healthy resistance-trained men were matched and then randomly assigned in a double-blind fashion to either a creatine (N = 10) or placebo (N = 9) group. Periodized heavy resistance training was performed for 12 wk. Creatine or placebo capsules were consumed (25 g x d(-1)) for 1 wk followed by a maintenance dose (5 g x d(-1)) for the remainder of the training. RESULTS: After 12 wk, significant (P < or = 0.05) increases in body mass and fat-free mass were greater in creatine (6.3% and 6.3%, respectively) than placebo (3.6% and 3.1%, respectively) subjects. After 12 wk, increases in bench press and squat were greater in creatine (24% and 32%, respectively) than placebo (16% and 24%, respectively) subjects. Compared with placebo subjects, creatine subjects demonstrated significantly greater increases in Type I (35% vs 11%), IIA (36% vs 15%), and IIAB (35% vs 6%) muscle fiber cross-sectional areas. Muscle total creatine concentrations were unchanged in placebo subjects. Muscle creatine was significantly elevated after 1 wk in creatine subjects (22%), and values remained significantly greater than placebo subjects after 12 wk. Average volume lifted in the bench press during training was significantly greater in creatine subjects during weeks 5-8. No negative side effects to the supplementation were reported. CONCLUSION: Creatine supplementation enhanced fat-free mass, physical performance, and muscle morphology in response to heavy resistance training, presumably mediated via higher quality training sessions.

Effects of diet on muscle triglyceride and endurance performance.

The purpose of this investigation was to examine the effects of diet on muscle triglyceride and endurance performance. Seven endurance-trained men completed a 120-min cycling bout at 65% of maximal oxygen uptake. Each subject then ingested an isocaloric high-carbohydrate (Hi-CHO; 83% of energy) or a high-fat (Hi-Fat; 68% of energy) diet for the ensuing 12 h. After a 12-h overnight fast, a 1,600-kJ self-paced cycling bout was completed. Muscle triglyceride measured before (33.0 +/- 2.3 vs. 37.0 +/- 2.1 mmol/kg dry wt) and after (30.9 +/- 2.4 vs. 32.8 +/- 1.6 mmol/kg dry wt) the 120-min cycling bout was not different between the Hi-CHO and Hi-Fat trials, respectively. After the 24-h dietary-fasting period, muscle triglyceride was significantly higher for the Hi-Fat (44.7 +/- 2.4 mmol/kg dry wt) vs. the Hi-CHO (27.5 +/- 2.1 mmol/kg dry wt) trial. Furthermore, self-paced cycling time was significantly greater for the Hi-Fat (139.3 +/- 7.1 min) compared with the Hi-CHO (117.1 +/- 3.2 min) trial. These data demonstrate that there was not a significant difference in muscle triglyceride concentration before and after a prolonged moderate-intensity cycling bout. Nevertheless, a high-fat diet increased muscle triglyceride concentration and reduced self-paced cycling performance 24 h after the exercise compared with a high-carbohydrate diet.

Effect of inosine supplementation on aerobic and anaerobic cycling performance.

Ten competitive male cyclists completed a Wingate Bike Test (WIN), a 30-min self-paced cycling performance bout (END), and a constant load, supramaximal cycling spring (SPN) to fatigue following 5 d of oral supplementation (5,000 mg.day-1) with inosine and placebo. Blood samples were obtained prior to and following both supplementation periods, and following each cycling test. Uric acid concentration was higher (P < 0.05) following supplementation with inosine versus placebo, but 2,3-DPG concentration was not changed. The data from WIN demonstrate that there were no significant differences in peak power (8.5 +/- 0.3 vs 8.4 +/- 0.3 W.kg body mass-1), end power (7.0 +/- 0.3 vs 6.9 +/- 0.2 W.kg body mass-1), fatigue index (18 +/- 2 vs 18 +/- 2%), total work completed (0.45 +/- 0.02 vs 0.45 +/- 0.02 kJ.kg body mass-1.30-s-1), and post-test lactate (12.2 +/- 0.5 vs 12.9 +/- 0.6 mmol.l-1) between the inosine and placebo trials, respectively. No difference was present in the total amount of work completed (6.1 +/- 0.3 vs 6.0 +/- 0.3 kJ.kg body mass-1) or post-test lactate (8.4 +/- 1.0 vs 9.9 +/- 1.3 mmol.l-1) during END between the inosine and placebo trials, respectively. Time to fatigue was longer (P < 0.05) during SPN for the placebo (109.7 +/- 5.6 s) versus the inosine (99.7 +/- 6.9 s) trial, but post-test lactate (14.8 +/- 0.7 vs 14.6 +/- 0.8 mmol.l-1) was not different between the treatments, respectively. These findings demonstrate that prolonged inosine supplementation does not appear to improve aerobic performance and short-term power production during cycling and may actually have an ergolytic effect under some test conditions.

The influence of starch structure on glycogen resynthesis and subsequent cycling performance.

The present study was designed to evaluate the influence of starch structure on muscle glycogen resynthesis and cycling performance. Eight male cyclists (22 +/- 1 yr) completed an exercise protocol (DP) to decrease vastus lateralis glycogen concentration. This exercise consisted of 60 min cycling at 75% VO2max, followed by six 1-min sprints at approximately 125% VO2max with 1 min rest intervals. In the 12 hr after the exercise each subject consumed approximately 3000 kcal (65:20:15% carbohydrate, fat and protein). All of the carbohydrate (CHO) consumed was derived from one of four solutions; 1) glucose, 2) maltodextrin (glucose polymer), 3) waxy starch (100% amylopectin), or 4) resistant starch (100% amylose). Muscle biopsies were taken from the vastus lateralis muscle after DP and 24 hr later to determine glycogen concentrations. A 30 min cycling time trial (TT) was performed following the 24 hr post-DP muscle biopsy to examine the influence of the feeding regimen on total work output. The post-DP glycogen concentrations were similar among the four trials, ranging from 220.3 +/- 29.2 to 264 +/- 48.3 mmol.kg-1 dry weight (d.w.) muscle. Twenty-four hours after DP, muscle glycogen concentration had increased less (p < 0.05) in the resistant starch trial (+90.8 +/- 12.8 mmol.kg-1 d.w.) than in the glucose (+197.7 +/- 31.6 mmol.kg-1 d.w.), maltodextrin (+136.7 +/- 24.5 mmol.kg-1 d.w.) and waxy starch (+171.8 +/- 37.1 mmol.kg-1 d.w.) trials. There were no differences in total work output during the TT, or blood lactate concentration immediately following the TT in any of the CHO trials. In summary, glycogen resynthesis was attenuated following ingestion of starch with a high amylose content, relative to amylopectin or glucose; however, short duration time trial performance was unaffected.

The effects of pre-exercise starch ingestion on endurance performance.

This study compared the physiological responses and performance following the ingestion of a waxy starch (WS), resistant starch (RS), glucose (GL) and an artificially-sweetened placebo (PL) ingested prior to exercise. Ten college-age, male competitive cyclists completed four experimental protocols consisting of a 30 min isokinetic, self-paced performance ride preceded by 90 min of constant load cycling at 66% VO2max. Thirty min prior to exercise, they ingested 1 g.kg-1 body weight of GL, WS, RS, or PL At rest, GL elicited greater (p < 0.05) serum glucose and insulin responses than all other trials. During exercise, however, serum glucose, insulin, blood C-peptide and glucagon responses were similar among trials. The mean total carbohydrate oxidation rates (CHOox) were higher (p < 0.05) during the GL, WS, and RS trials (2.59 +/- 0.13, 2.49 +/- 0.10, and 2.71 +/- 0.15 g.min-1, respectively) compared to PL (2.35 +/- 0.12 g.min-1). Subjects were able to complete more work (p < 0.05) during the performance ride when they ingested GL (434 +/- 25.2 kj) or WS (428 +/- 22.5 kj) compared to PL (403 +/- 35.1 kj). They also tended to produce more work with RS ingestion (418 +/- 31.4 kj), although this did not reach statistical significance (p < 0.09). These results indicate that preexercise CHO ingestion in the form of starch or glucose maintained higher rates of total carbohydrate oxidation during exercise and provided an ergogenic benefit during self-paced cycling.

Effect of caffeine ingestion on perception of effort and subsequent work production.

The purpose of this investigation was to determine the effect of caffeine ingestion on work output at various levels of perceived exertion during 30 min of isokinetic variable-resistance cycling exercise. Ten subjects completed six trials 1 hr after consuming either 6 mg.kg-1 caffeine (3 trials) or a placebo (3 trials). During each trial the subjects cycled at what they perceived to be a rating of 9 on the Borg rating of perceived exertion scale for the first 10 min, a rating of 12 for the next 10 min, and a rating of 15 for the final 10 min. Total work performed during the caffeine trials averaged 277.8 +/- 26.1 kJ, whereas the mean total work during the placebo trials was 246.7 +/- 21.5 kJ (p < .05). However, there were no significant differences between the conditions in respiratory exchange ratio. These data suggest that caffeine may play an ergogenic role in exercise performance by altering both neural perception of effort and substrate availability.

Pyridoxic acid excretion during low vitamin B-6 intake, total fasting, and bed rest.

Vitamin B-6 metabolism in 10 volunteers during 21 d of total fasting was compared with results from 10 men consuming a diet low only in vitamin B-6 (1.76 mumol/d) and with men consuming a normal diet during bed rest. At the end of the fast mean plasma concentrations of vitamin B-6 metabolites and urinary excretion of 4-pyridoxic acid tended to be higher in the fasting subjects than in the low-vitamin B-6 group. The fasting subjects lost approximately 10% of their total vitamin B-6 pool and approximately 13% of their body weight. The low-vitamin B-6 group lost only approximately 4% of their vitamin B-6 pool. Compared with baseline, urinary excretion of pyridoxic acid was significantly increased during 17 wk of bed rest. There was no increase in pyridoxic acid excretion during a second 15-d bed rest study. These data suggest the possibility of complex interactions between diet and muscle metabolism that may influence indexes that are frequently used to assess vitamin B-6 status.

The effect of oral coenzyme Q10 on the exercise tolerance of middle-aged, untrained men.

In order to determine the effect of oral Coenzyme Q10 (CoQ10) dosing on exercise capacity, 15 middle-aged men (44.7 +/- 2.0 years) received either CoQ10 (150 mg/day x 2 months-Q10 GRP) or placebo (2 months-CON GRP). Blood CoQ10 levels increased (p < 0.05) during the treatment in the Q10 GRP (Pre = 0.72 +/- 0.06, 2 months = 1.08 +/- 0.14 micrograms/ml) and were unchanged in the CON GRP (Pre = 0.91 +/- 0.05, 2 month = 0.69 +/- 0.05 microgram/ml). Similarly, the subjective perception of vigor (visual analog scale 1-10 where, 10 = very energetic, and 0 = very, very unenergetic) increased (p < 0.05) in the Q10 GRP (Pre = 5.73 +/- 0.35, 2 month = 6.64 +/- 0.45). However, maximal oxygen consumption (VO2max Pre = 2.97 +/- 0.18, 2 month = 3.05 +/- 0.15 l/min) and lactate threshold (LT Pre = 2.04 +/- 0.12, 2 month = 2.08 +/- 0.12 l/min), as measured on the cycle ergometer, were unchanged as a result of the CoQ10 treatment, Neither forearm oxygen uptake, nor forearm blood flow was found to be affected by the CoQ10. Although lactate release during hand-grip testing tended to decrease in the Q10 GRP (Pre = 227 +/- 49, 2 month = 168.3 +/- 40 mumole/min) this was not significant (p > 0.05). It can be concluded that short-term (2 months) oral dosing with CoQ10 increases circulating blood levels of CoQ10 and the subjective perceived level of vigor in middle-aged men. However, short-term dosing does not improve aerobic capacity or firearm exercise metabolism as measured in this investigation.

Skeletal muscle characteristics among distance runners: a 20-yr follow-up study.

The purpose of this investigation was to examine the histochemical and enzymatic characteristics of skeletal muscle after 20 yr of distance running training. Twenty-eight men were first studied between 1966 and 1974 when they were all highly trained distance runners. On the basis of their training regimens in the interim between testing, subjects were described as highly trained (HI; n = 11), fitness trained (FIT; n = 10), or untrained (UT; n = 7). Gastrocnemius muscle biopsy samples revealed a mean increase (P < 0.05) in the proportion of type I fibers of the FIT and UT groups, whereas the HI group, which was initially characterized by a high percentage (> 70%) of type I fibers, was unchanged. Although the mean fiber type change of the HI group was similar between evaluations, 6 of the 11 subjects did elicit an increase in the percentage of type I fibers. A subgroup of elite distance runners who had continued to train for competition experienced an approximately 25% reduction (P > 0.05) in muscle succinate dehydrogenase activity and decreases (P > 0.05) in types I and II muscle fiber areas. On the average, in 1993 the HI group had higher (P < 0.05) succinate dehydrogenase and citrate synthase activities than the FIT and UT groups, whereas phosphorylase activity did not differ among the three groups. These data suggest that the middle-aged men in this study had a significantly greater proportion of type I muscle fibers than when they were 20 yr younger.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between muscle carnitine, age and oxidative status.

Muscle carnitine levels were examined in 31 younger [mean (SD), 27 (5) years] and 27 older [49 (8) years] men. Needle biopsies were obtained from the lateral gastrocnemius or vastus lateralis muscles and assayed for free and total carnitine concentrations via a 5,5'-Dithiobis-(2-nitrobenzoic acid) DTNB-linked spectrophotometric procedure. A subgroup of subjects (n = 28) were assessed for citrate synthase (CS) and succinate dehydrogenase (SDH) activity, and type I muscle fiber composition (% type I fibers). An additional sub-group of nine subjects was assessed for free and total serum carnitine levels. No mean (SEM) differences in free [21.6 (0.7) vs 20.3 (0.9) mumol.g dry weight-1] and total [26.4 (0.6) vs 26.1 (0.9) mumol.g dry weight-1) muscle carnitine levels were found between the younger and older subjects, respectively. Correlational data revealed no significant relationships between total muscle carnitine and CS (r = -0.36), SDH (r = -0.26), or % type I fibers (r = -0.16). In addition, there was a low non-significant relationship between serum and muscle total carnitine concentrations (r = -0.44). These findings suggest that muscle carnitine levels are similar between younger and older males, and there does not appear to be any relationship between muscle carnitine and markers of muscle oxidative potential (i.e., oxidative enzymes, % type I fiber). Since serum carnitine is often used as an indicator of body carnitine status, it is noteworthy that we found a low negative relationship between blood and muscle carnitine concentrations.

Carnitine supplementation: effect on muscle carnitine and glycogen content during exercise.

This study investigated the effects of L-carnitine supplementation on muscle carnitine and glycogen content during submaximal exercise (EX). Triglycerides were evaluated by a fat feeding (90 g fat) and 3 h later subjects cycled for 60 min at 70% VO2max (CON). Muscle biopsies were obtained preexercise and after 30 and 60 min of EX. Blood samples were taken prior to and every 15 min of exercise. Subjects randomly completed two additional trials following 7 and 14 d of carnitine supplementation (6 g.d-1). During one of the two trials, subjects received 2000 units of heparin 15 min prior to EX to elevate FFA (CNhep); no heparin was administered during the other trial (CN). There were no differences in VO2, respiratory exchange ratio, heart rate, or g.min-1 of CHO and fat oxidized among the three trials. At rest serum total acid soluble (TASC) and free (FC) carnitine increased with supplementation (TASC; CON, 71.3 +/- 2.9; CN, 92.8 +/- 5.4; CNhep, 109.8 +/- 3.5 mumol.l-1) (FC; CON, 44.1 +/- 2.7; CN, 66.1 +/- 5.3; CNhep, 77.1 +/- 4.1 mumol.l-1). During EX, TASC remained stable, while FC decreased and short-chain acylcarnitine (SCAC) increased (P < 0.05). Muscle carnitine concentration at rest was unaffected by supplementation. During EX, muscle TASC did not change, FC decreased, and SCAC increased significantly in all three trials. Pre-EX and post-EX muscle glycogens were not different. Increased availability of serum carnitine does not result in an increase in muscle carnitine content nor does it alter lipid oxidation. It appears that there is an adequate amount of carnitine present within the mitochondria to support lipid oxidation.

Effect of L-carnitine supplementation on muscle and blood carnitine content and lactate accumulation during high-intensity sprint cycling.

This study examined the effects of 14 days of L-carnitine supplementation on muscle and blood carnitine fractions, and muscle and blood lactate concentrations, during high-intensity sprint cycling exercise. Eight subjects performed three experimental trials: control I (CON I, Day 0), control II (CON II, Day 14), and L-carnitine (L-CN, Day 28). Each trial consisted of a 4-min ride at 90% VO2max, followed by a rest period of 20 min, and then five repeated 1-min rides at 115% VO2max (2 min rest between each). Following CON II, all subjects began dietary supplementation of L-carnitine for a period of 14 days (4 g/day). Plasma total acid soluble and free carnitine concentrations were significantly higher (p < .05) at all time points following supplementation. L-carnitine supplementation had no significant effect on muscle carnitine content and thus could not alter lactate accumulation during exercise.

Effect of passive and active recovery on the resynthesis of muscle glycogen.

The purpose of this investigation was to determine the effect of passive and active recovery on the resynthesis of muscle glycogen after high-intensity cycle ergometer exercise in untrained subjects. In a cross-over design, six college-aged males performed three, 1-min exercise bouts at approximately 130% VO2max with a 4-min rest period between each work bout. The exercise protocol for each trial was identical, while the recovery following exercise was either active (30 min at 40-50% VO2max, 30-min seated rest) or passive (60-min seated rest). Initial muscle glycogen values averaged 144.2 +/- 3.8 mmol.kg-1 w.w. for the active trial and 158.7 +/- 8.0 mmol.kg-1 w.w. for the passive trial. Corresponding immediate postexercise glycogen contents were 97.7 +/- 5.4 and 106.8 +/- 4.7 mmol.kg-1 w.w., respectively. These differences between treatments were not significant. However, mean muscle glycogen after 60 min of passive recovery increased 15.0 +/- 4.9 mmol.kg-1 w.w., whereas it decreased 6.3 +/- 3.7 mmol.kg-1 w.w. following the 60 min active recovery protocol (P < 0.05). Also, the decrease in blood lactate concentration during active recovery was greater than during passive recovery and significantly different at 10 and 30 min of the recovery period (P < 0.05). These data suggest that the use of passive recovery following intense exercise results in a greater amount of muscle glycogen resynthesis than active recovery over the same duration.

The effects of L-carnitine supplementation on performance during interval swimming.

To examine the effects of L-carnitine supplementation on short high-intensity exercise, twenty male collegiate swimmers completed two trials separated by seven days. Each trial consisted of five 91.4 m (100 yd) swims with a two minute rest interval between each bout. Following the first trial subjects were evenly and randomly assigned to either an L-carnitine (LC) group or a placebo (PL) group. The LC group ingested 2 grams L-carnitine in a citrus drink twice daily for 7 days, while the PL group received only the citrus drink during the same time period. Performance times were recorded for each repeat during both trials. Blood samples (5 ml) were obtained from an antecubital vein 1 minute following the interval set. Blood pH, base excess (BE), lactate (LA), carnitine and carnitine fractions were measured. Total serum carnitine was significantly (p < 0.05) elevated (75.9 +/- 2.0 vs. 106.4 +/- 3.5 mumol.l-1) in the LC group following treatment, while the PL group was unchanged (79.5 +/- 2.8 vs. 77.6 +/- 5.3 mumol.l-1). Free and short-chain serum carnitine fractions were also increased (p < 0.05) in the LC group, but were not altered in the PL group. No differences in performance times were observed between trials or between groups. Blood pH, LA and BE revealed a similar response in both groups during each trial. Despite the elevation in serum L-carnitine and carnitine fractions, these results indicate that L-carnitine supplementation does not provide an ergogenic benefit during repeated bouts of high-intensity anaerobic exercise in highly trained swimmers.

Carbohydrate ingestion during exercise: effects on muscle glycogen resynthesis after exercise.

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.

Effect of fat emulsion infusion and fat feeding on muscle glycogen utilization during cycle exercise.

Elevated plasma fatty acids have been shown to spare muscle glycogen during exercise. However, on the basis of recent findings, the saturation of fatty acids may influence this response. The purpose of this study was to determine whether saturated or unsaturated fatty acids affected muscle glycogenolysis to varying degrees during cycle exercise. Five healthy men completed three 60-min cycle ergometer trials (EX) at approximately 70% maximal O2 uptake (VO2max). Triglyceride levels were elevated by a fat feeding (FF) composed of 90% saturated fatty acids (heavy whipping cream, 90 g) or by the infusion of Intralipid (IL; Clintec Nutrition; 45 ml/h of 20% IL, 9.0 g), which was 85% unsaturated. A control trial (CON) consisted of a light breakfast (43 g carbohydrate and 1 g fat). Heparin (2,000 U) was administered 15 min before EX in FF and IL trials, resulting in one- and threefold increases in free fatty acid (FFA) levels in IL and FF, respectively. Pre-EX muscle glycogen did not differ. The utilization of muscle glycogen during 60 min of EX was less (P < 0.05) during the FF (60.0 +/- 5.2 mmol/kg wet wt) and IL (58.6 +/- 6.2 mmol/kg wet wt) compared with CON (81.8 +/- 7.5 mmol/kg wet wt). There was no difference between FF and IL in the amount of glycogen utilized. Serum triglyceride levels were greater (P < 0.05) at preheparin in FF (1.58 +/- 0.37 mmol/l) and IL (0.98 +/- 0.13 mmol/l) compared with CON (0.47 +/- 0.14 mmol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Dry-land resistance training for competitive swimming.

To determine the value of dry-land resistance training on front crawl swimming performance, two groups of 12 intercollegiate male swimmers were equated based upon preswimming performance, swim power values, and stroke specialties. Throughout the 14 wk of their competitive swimming season, both swim training group (SWIM, N = 12) and combined swim and resistance training group (COMBO, N = 12) swam together 6 d a week. In addition, the COMBO engaged in a 8-wk resistance training program 3 d a week. The resistance training was intended to simulate the muscle and swimming actions employed during front crawl swimming. Both COMBO and SWIM had significant (P < 0.05) but similar power gains as measured on the biokinetic swim bench and during a tethered swim over the 14-wk period. No change in distance per stroke was observed throughout the course of this investigation. No significant differences were found between the groups in any of the swim power and swimming performance tests. In this investigation, dry-land resistance training did not improve swimming performance despite the fact that the COMBO was able to increase the resistance used during strength training by 25-35%. The lack of a positive transfer between dry-land strength gains and swimming propulsive force may be due to the specificity of training.

Carbohydrate feedings and exercise performance: effect of initial 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)

Glycogen resynthesis in skeletal muscle following resistive exercise.

The purpose of this investigation was to determine the influence of post-exercise carbohydrate (CHO) intake on the rate of muscle glycogen resynthesis after high intensity weight resistance exercise in subjects not currently weight training. In a cross-over design, eight male subjects performed sets (mean = 8.8) of six single leg knee extensions at 70% of one repetition max until 50% of full knee extension was no longer possible. Total force application was equated between trials using a strain gauge interfaced to a computer. The subjects exercised in the fasted state. Post-exercise feedings were administered at 0 and 1 h consisting of either a 23% CHO solution (1.5 g.kg-1) or an equal volume of water (H2O). Total force production, preexercise muscle glycogen content, and degree of depletion (-40.6 and -44.3 mmol.kg-1 wet weight) were not significantly different between H2O and CHO trials. As anticipated during the initial 2-h recovery, the CHO trial had a significantly greater rate of muscle glycogen resynthesis as compared with the H2O trial. The muscle glycogen content was restored to 91% and 75% of preexercise levels when water and CHO were provided after 6 h, respectively.