The effects of replacing a portion of endurance training by explosive strength training on performance in trained cyclists

To investigate the effects of replacing a portion of endurance training by strength training on exercise performance, 14 competitive cyclists were divided into an experimental (E; n=6) and a control (C; n=8) group. Both groups received a training program of 9 weeks. The total training volume for both groups was the same [E: 8.8 (1.1) h/week; C: 8.9 (1.7) h/week], but 37% of training for E consisted of explosive-type strength training, whilst C received endurance training only. Simulated time trial performance (TT), short-term performance (STP), maximal workload ( ) and gross (GE) and delta efficiency (DE) were measured before, after 4 weeks and at the end of the training program (9 weeks). No significant group-by-training effects for the markers of endurance performance (TT and ) were found after 9 weeks, although after 4 weeks, these markers had only increased (P<0.05) in E. STP decreased (P<0.05) in C, whereas no changes were observed in E. For DE, a significant group-by-training interaction (P<0.05) was found, and for GE the group-by-training interaction was not significant. It is concluded that replacing a portion of endurance training by explosive strength training prevents a decrease in STP without compromising gains in endurance performance of trained cyclists. Electronic Publication     

The effect of endurance training on the ventilatory response to exercise in elite cyclists

The purpose of this study was to investigate the effects of endurance training on the ventilatory response to acute incremental exercise in elite cyclists. Fifteen male elite cyclists [mean (SD) age 24.3 (3.3) years, height 179 (6) cm, body mass 71.1 (7.6) kg, maximal oxygen consumption (V˙O_2max) 69 (7) ml · min⁻¹ · kg⁻¹] underwent two exercise tests on a cycle ergometer. The first test was assessed in December, 6 weeks before the beginning of the cycling season. The second test was performed in June, in the middle of the season. During this period the subjects were expected to be in a highly endurance-trained state. The ventilatory response was assessed during an incremental exercise test (20 W · min⁻¹). Oxygen consumption (V˙O₂), carbon dioxide production (V˙CO₂), minute ventilation (V˙ _E), and heart rate (HR) were assessed at the following points during the test: at workloads of 200 W, 250 W, 300 W, 350 W, 400 W and at the subject's maximal workload, at a respiratory exchange ratio (R) of 1, and at the ventilatory threshold (Th_vent) determined using the V-slope-method. Post-training, the mean (SD) V˙O_2max was increased from the pre-training level of 69 (7) ml · min⁻¹ · kg⁻¹ (range 61.4–78.6) to 78 (6) ml · min⁻¹ · kg⁻¹ (range 70.5–86.3). The mean post-training V˙O₂ was significantly higher than the pre training value (P < 0.01) at all work rates, at Th_vent and at R=1. V˙O₂ was also higher at all work rates except for 200 W and 250 W. V˙ _E was significantly higher at Th_vent and R=1. Training had no effect on HR at all workloads examined. An explanation for the higher V˙O₂ cost for the same work rate may be that in the endurance-trained state, the adaptation to an exercise stimulus with higher intensity is faster than for the less-trained state. Another explanation may be that at the same work rate, in the less-endurance-trained state power is generated using a significantly higher anaerobic input. The results of this study suggest the following practical recommendations for training management in elite cyclists: (1) the V˙O₂ for a subject at the same work rate may be an indicator of the endurance-trained state (i.e., the higher the V˙O₂, the higher the endurance-trained capacity), and (2) the need for multiple exercise tests for determining the HR at Th_vent during a cycling season is doubtful since at Th_vent this parameter does not differ much following endurance training. Accepted: 19 October 1999     

Acute effects of endurance exercise on mitochondrial distribution and skeletal muscle morphology

Summary Biopsies of vastus lateralis from seven well-trained males were studied 1 month before and 15–30 min after a 100-km race. The distribution of interfibrillar mitochondria was analyzed to determine whether a long bout of exercise induced a redistribution of mitochondria. Capillary densities and mean fiber areas were also estimated. Capillary density and mean interfibrillar mitochondrial volume density were found to be significantly correlated with running time in the race. An earlier study on these biopsies found that the mean volume densities of interfibrillar and subsarcolemmal mitochondria did not change after a race, but the volume densities of lipid droplets and interfibrillar glycogen decreased significantly. In the present study, volume density of interfibrillar mitochondria [V_v(mi, fim)] before the race was highest with a value of 0.098±0.007 near the fiber border, and decreased progressively with distance to 0.045±0.004 at the fiber center. After the race, V_v(mi, fim) was unchanged at the fiber border, but was significantly higher (0.062±0.005) in the center of the fiber. This increase in mitochondrial volume density was attributable to the shrinkage of the fibers from consumption of energy stores, which was relatively greater for interfibrillar glycogen than for subsarcolemmal glycogen. Thus the primary effect of this extended bout of endurance exercise on vastus lateralis was the nearly complete depletion of the interfibrillar glycogen and lipids, but there was no evidence of an acute redistribution of mitochondria.Supported by a Postdoctoral Fellowship from the Swiss National Science Foundation     

"Oxidative stress": effects of mild endurance training and testosterone treatment on rat gastrocnemius muscle

We evaluated the effects of testosterone overload on mitochondrial superoxide dismutase (MnSOD), cytochrome oxidase (COX) and citrate synthase (CS) activities of the rat superficial gastrocnemius both in non-exercised muscle and following moderate endurance training. Basal (bLPO) and stimulated (sLPO) lipid peroxidation was measured as an index of oxidative tissue damage. Furthermore, to assess the relationship between exercise and testosterone-induced metabolic adaptations and contractile protein expression, the distribution of myosin heavy chain (MHC) isoforms was analysed by SDS-PAGE. Samples were obtained from: controls (C), rats treated with testosterone propionate (Tp) (TP, 5 mg kg^–1 i.m. 6 days/week), trained rats (E, 5 days/week) and rats trained and treated with Tp (ETP). MnSOD significantly increased in E and TP in comparison with C and ETP. Training induced a significant increase in COX activity both in E and ETP whereas a statistical reduction was observed in TP in comparison with the other groups. Moreover, testosterone administration was associated with a significant reduction in CS activity which significantly increased in ETP. A reduction in lipid peroxidation was observed in E and ETP in comparison with controls both in basal and stimulated conditions, whereas TP showed a significant increase of bLPO. In trained rats enzymatic changes were correlated with an increase in the proportion of fast oxidative MHC-2A and MHC-2X with decrease of the proportion of fast MHC-2B. In contrast, Tp treatment induced an increase in the proportion of MHC-2B whereas MHC-2A and MHC-2X disappeared. Finally, ETP showed a reduction in MHC-2B and an increase in MHC-1 and MHC-2X. These data suggest that testosterone supplementation seems not to significantly modify the metabolic adaptation induced by exercise in gastrocnemius muscle. Furthermore, testosterone overload to non-exercised rats seems to reduce the mitochondrial function and increase the lipid peroxidation of the muscle. Electronic Publication     

The effect of salbutamol on performance in endurance cyclists

The effect of salbutamol (S) on cycling performance was examined in 15 highly trained non-asthmatic male cyclists. A double-blind, randomized cross-over design was used with S or placebo (P) administered using a metered-dose inhaler and a spacer device 20 min before each testing session. The S dose was 400 μg (four puffs), which is twice the normal therapeutic level. Subjects were habituated to all the laboratory procedures in the week prior to actual data collection. The subjects performed four tests under S and P conditions on separate days over 2 weeks. These included measurement of maximal O₂ uptake (cycle ergometry) with assessment of pulmonary function before and after, a submaximal (90% of ventilatory threshold) square-wave work transition from a base of unloaded cycling, a 60-s modified Wingate test, and a simulated 20 km time trial. No significant differences were observed in any of the dependent variables related to aerobic endurance or cycling performance between the S and P conditions. These results support other findings that an acute dose (400 μg) of S has no performance-enhancing properties.     

The influence of high carbohydrate diets on endurance running performance

Summary The purpose of the present study was to examine the influence of high carbohydrate (CHO) diets on recovery of endurance capacity following a treadmill run to exhaustion. Two high CHO diets were used, one in which the normal diet was supplemented with complex carbohydrates and the other in which supplementation was achieved with simple carbohydrates. The thirty recreational runners who took part in this study (fifteen men and fifteen women) completed weighed food intake diaries two to three weeks before the start of the study. From an analysis of this information each subject's normal diet was prescribed before Trial 1 and then a supplemented diet before Trial 2. The aim was to achieve an increase in carbohydrate content to 70% in the diets of the two high CHO groups and an equivalent increase in energy intake by the Control group. The subjects were required to run to exhaustion on a treadmill at a speed equivalent to 70% on two occasions separated by 3 days. After Trial 1 the subjects were divided into three equal groups. The Complex CHO group (301±86 mg vs 507±120 mg) and Simple CHO group (265±45 mg vs 462±81 mg) increased their CHO intake by approximately 70% (p<0.05) during the 3 days before Trial 2 whereas the Control group increased their energy intake with additional protein and fat so as to match the energy intakes of the two CHO groups. The Complex CHO group improved their running time to exhaustion during Trial 2 by 26% (105.9±22.4 to 133.3±46.5 min;p<0.01) and the Simple CHO group increased their run time by 23% (114.5±15.6 to 140.6±27.0 min;p<0.01) whereas there was no significant increase in the running time of the Control group (119±19.5 to 122.4±22.4 min). There was no significant difference between the blood lactate and glucose concentrations during the two trials but the plasma FFA concentrations were significantly lower before Trial 2 for the Complex CHO group (0.41±0.15 vs 0.27±0.16 mmol^–1;p<0.01) and the Simple CHO group (0.24±0.13 vs 0.19±0.09 mmol^–1). The respiratory exchange ratios for the two CHO groups were significantly higher for most of Trial 2 compared with the values obtained during Trial 1. The results of this study have shown that recovery of endurance running capacity is enhanced by an increase in dietary CHO, which can be accomplished by supplementing the normal diet with either simple or complex carbohydrates.     

Effect of prior ingestion of glucose or fructose on the performance of exercise of intermediate duration

The metabolic responses induced by the ingestion of a beverage containing glucose (G), fructose (F) or placebo (W) 30 min before exercise of high intensity and intermediate duration have been investigated; in these conditions the energy processes are mostly dependent on aerobic reactions. A group of 11 male recreational sportsmen ran on a treadmill, at an intensity corresponding to 82% of peak oxygen consumption, until exhaustion on three different occasions (after ingestion of a beverage containing 75 g of G, 75 g of F or W). Plasma glucose, insulin, and lactic acid concentrations were determined just prior to the ingestion of the beverages, 30 min afterwards and 10 and 30 min after completion of the exercise. The mean endurance time was 644 (SD 261) s after the ingestion of G, 611 (SD 227) s after the ingestion of F and 584 (SD 189) s after the ingestion of the W (P < 0.05 between G and W). No differences in the oxygen uptake, respiratory quotient or lactate concentrations between the three trials were observed. Both plasma glucose and insulin concentrations determined in samples obtained immediately before the onset of exercise were higher when G was ingested than when F (P < 0.05 andP < 0.05, respectively) or W (P < 0.001 and P < 0.005, respectively) were ingested. These findings would suggest that the ingestion of G prior to an effort of intermediate duration may improve physical performance.     

Effect of endurance exercise on fibre type composition and muscle weight of reinnervating rat plantaris muscle

The purpose of this study was to evaluate the effect of endurance exercise on the histochemistry and wet weight of the reinnervating rat plantaris muscle. Two groups of young female Wistar rats (6 weeks old), 1 sedentary denervated control (n=13) and 1 excercised denervated experimental (n=17), were denervated unilaterally by cutting and resecting the sciatic nerve. To effect reinnervation a skin grafting operation was carried out on the nerve so that the gap caused by resection was bridged. The third group was the sedentary non-denervated normal control (n=10). A progressive training program of 18 weeks of treadmill running was carried out by the experimental group. Approximately 5 months after denervation, the plantaris muscles were studied histochemically for reduced nicotinamide adenine dinucleotide diaphorase (NADH-D) and mitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPD) activities. Fibres were classified as red, white, or intermediate with NADH-D. Alpha-GPD differentiates intermediate from red fibre types in case of difficulty in differentiating these fibre types from each other with NADH-D. The weight of the reinnervated plantaris muscle increased significantly after exercise. The exerise did not change the fibre type proportions — including red fibre type — in the deep region of the reinnervating plantaris. There were significant differences between normal control and denervated control or experimental groups in histochemical fibre populations in the deep region of the plantaris. The findings of this study suggest that: (a) treadmill running did not increase the oxidative capacity of the deep region of the reinnervating rat plantaris muscle; (b) treadmill training did not damage the reinnervating plantaris; (c) the presence of type grouping following reinnervation was not affected by training (exercise did not interfere with reinnervation).     

Influence of fluid intake on endurance running performance

Summary The aim of the present study was to compare the influence of drinking water, a carbohydrate-electrolyte solution, containing additional free glucose (Glucose) or the same carbohydrate-electrolyte solution containing additional fructose (Fructose), on running performance. Twelve endurance-trained recreational runners volunteered to take part in this study; 9 completed the three and all 12 completed two trials. The subjects were randomly assigned to one of the three trials: Water, Glucose or Fructose. In each trial the subjects were required to run 30 km as fast as possible on a motorized treadmill, instrumented so that they could control its speed. The carbohydrate-electrolyte solutions contained a total of 50 g carbohydrate, 20 g as a glucose polymer. The Glucose solution contained an additional 20 g free glucose and the Fructose solution contained an additional 20 g fructose rather than glucose. The osmolality of the Glucose and Fructose solutions was approximately 300–320 mosmol and the energy equivalent of both solutions was 794 kJ·l^–1. The subjects ingested 11 fluid throughout each run. The running times were not significantly different, being 129.3 (±17.7) min, 124.8 (±14.9) min and 125.9 (±17.9) min for Water, Glucose and Fructose respectively. There was a decrease (P<0.05) in running speed over the last 10 km of the Water trial from 4.14 (±0.55) to 3.75 (±0.86) m· s^–1, which did not occur in the carbohydrate trials. Blood glucose concentrations during the Water trial decreased from 15 km onwards and at the end of the run they were significantly (P<0.05) lower than the value recorded at 15 km. In contrast they did not decrease in the two carbohydrate trials. There were no significant differences between the responses of the subjects during the Glucose and Fructose trials.     

Uptake of 3H-leucine into different fractions of rat skeletal muscle following acute endurance and sprint exercise

Summary In order to study the specificity of the protein synthetic response to different acute exercise loads, 48 male rats served as non-exercised controls or ran at either 0.5 m·s^–1 for 1 h or 1.5 m·s^–1, 10 s20 s workrest, for 1h. Animals were killed and red and white vastus muscles excised from the controls or at 0, 2, 18, 24, or 48 h post-exercise. Muscle slices were incubated in a medium containing 10 Ci l-[4,5-³H]leucine for 30 min. Incorporation of the radionuclide was measured by liquid scintillation (dpm·mg^–1 protein) in the whole homogenate and in four subcellular fractions. The endurance exercise elicited increased uptakes into the mitochondrial fractions of both red and white vastus at 2 and 18 h respectively. However, the mitochondrial uptake was depressed at 24 h in the red and at 2 h in the white vastus. Only in red vastus was incorporation into the soluble protein elevated following endurance exercise. The sprint protocol elicited increased uptake into soluble protein at 2 and 18 h in both red and white vastus and into mitochondrial protein at 18 and 24 h in the white vastus. The shifts in uptake in white vastus occurred in conjunction with depressed uptakes in the total homogenate. These data indicate that both the changes in the type of protein and the time course of amino acid incorporation following acute exercise are related to both the metabolic characteristics of the muscle fibres and the intensity of the exercise.This study was supported by Grants from the Natural Sciences and Engineering Research Council (NSERC A0424 and NSERC A6436)     

The reproducibility of an endurance performance test in adolescent cyclists

The purpose of the study was to measure the reproducibility of a performance test in well-trained adolescent cyclists. Eight male and one female cyclist [mean age 15.7 (0.7) y] participated in the study. Lactate threshold (LT) and peak VO₂ were assessed. The performance test was repeated on three separate days and consisted of 30 min of steady state (SS) cycling at 80% of individual LT. Immediately after the SS cycling a time trial (TT) started with the cyclists having to complete a fixed amount of work as fast as possible. Reliability was assessed for the TT with the coefficient of variation (CV) as the (SD/mean)*100 for each participant, intraclass correlation coefficients (ICC) and typical error (SD of the difference in mean /2). The group mean (SD) times for the TT were TT1 1889 (306), TT2 1857 (283) and TT3 1953 (279) s respectively. Individual CV varied from 0.25% to 10%. The ICC for TT1/2 and 2/3 were r=0.78 and 0.93 (P<0.05). The typical errors, expressed as a CV% on the log transformed performance times, were 7.3 and 3.7% for TT1/2 and TT2/3 respectively. The largest individual CVs were observed between TT1 and TT2. The differences in CV and SD among the three TTs indicate that trial two and three were more reliable than TT1, suggesting a habituation trial is needed. It is concluded that the present performance test is reliable in adolescent cyclists with lower variation between trials 2 and 3.     

Effects of vitamin E deficiency on fatigue and muscle contractile properties

Radical-mediated oxidative damage of skeletal muscle membranes has been implicated in the fatigue process. Vitamin E (VE) is a major chain breaking antioxidant that has been shown to reduce contraction-mediated oxidative damage. We hypothesized that VE deficiency would adversely affect muscle contractile function, resulting in a more rapid development of muscular fatigue during exercise. To test this postulate, rats were fed either a VE-deficient (EDEF) diet or a control (CON) diet containing VE. Following a 12-week feeding period, animals were anesthetized and mechanically ventilated. Muscle endurance (fatigue) and contractile properties were evaluated using an in situ preparation of the tibialis anterior (TA) muscle. Contractile properties of the TA muscle were determined before and after a fatigue protocol. The muscle fatigue protocol consisted of 60 min of repetitive contractions (250 ms trains at 15 Hz; duty cycle=11%) of the TA muscle. Prior to the fatigue protocol, no significant differences existed in the force-frequency curves between EDEF and CON animals. At the completion of the fatigue protocol, muscular force production was significantly (P<0.05) lower in the EDEF group (reduced by 69%) compared to CON group (reduced by 38%). Following the fatigue protocol, a right shift existed in the force-frequency curve at low stimulation frequencies (≤40 Hz) in the EDEF animals compared to the CON animals (P<0.05). The stimulated and the contralateral TA muscle from the EDEF animals had significantly higher markers of lipid peroxidation compared to the same muscles in the CON animals (P<0.05). These data support the hypothesis that VE deficiency impairs muscular endurance and alters muscle contractile properties following a prolonged series of contractions. Electronic Publication     

The effect of caffeine ingestion on physical performance after prolonged exercise

Summary The purpose of this study was to determine the effect of caffeine ingestion on physical performance after prolonged endurance exercise. Twenty three trained male volunteers participated in a 40-km march and were divided into two groups, matched for caffeine clearance rate and aerobic capacity. The experimental group ingested, prior to the march, a caffeinated drink at a dose of 5 mg·kg⁻¹ body mass and at the 3rd and 5th h of marching an additional drink at a dose of 2.5 mg·kg⁻¹ body mass. The control group ingested a drink of equal volume at the same times. Upon termination of the march each subject performed a cycle ergometer test at an intensity of 90% maximal oxygen consumption. Time to exhaustion and rate of perceived exertion (RPE) were recorded. Blood samples were drawn predrink, at the 3rd and 5th h of marching and immediately after the cycle ergometer test, and were analysed for caffeine, free fatty acids (FFA), lactate and glucose levels. Plasma FFA levels increased during the march (p<0.05), with no significant difference between groups. Lactate levels increased in the experimental group (p<0.05), with no significant change in the control group. Glucose levels did not change significantly in either group. After the cycle ergometer test, lactate levels were significantly higher in the experimental, as compared to the control group (3.77±0.33 vs 2.52±0.35 mmol·l⁻¹, respectively). There was no significant difference between treatments in the time to exhaustion on the cycle ergometer, but RPE was different (p<0.05). Under the conditions of this study, the results do not indicate caffeine ingestion as an ergogenic aid which will postpone exhaustion following prolonged endurance exercise. This work was presented, in part, at the Canadian Association of Sports Sciences Annual Meeting, October 1987, Lake Louise, Alberta, Canada     

Respiratory muscle endurance training: effect on normoxic and hypoxic exercise performance

The aim of this study was to investigate the effect of respiratory muscle endurance training on endurance exercise performance in normoxic and hypoxic conditions. Eighteen healthy males were stratified for age and aerobic capacity; and randomly assigned either to the respiratory muscle endurance training (RMT = 9) or to the control training group (CON = 9). Both groups trained on a cycle-ergometer 1 h day⁻¹, 5 days per week for a period of 4 weeks at an intensity corresponding to 50% of peak power output. Additionally, the RMT group performed a 30-min specific endurance training of respiratory muscles (isocapnic hyperpnea) prior to the cycle ergometry. Pre, Mid, Post and 10 days after the end of training period, subjects conducted pulmonary function tests (PFTs), maximal aerobic tests in normoxia ([(V)\dot] {\dot{V}} O_2maxNOR), and in hypoxia ([(V)\dot] {\dot{V}} O_2maxHYPO; F_IO₂ = 0.12); and constant-load tests at 80% of [(V)\dot] {\dot{V}} O_2maxNOR in normoxia (CLT_NOR), and in hypoxia (CLT_HYPO). Both groups enhanced [(V)\dot] {\dot{V}} O_2maxNOR (CON: +13.5%; RMT: +13.4%), but only the RMT group improved [(V)\dot] {\dot{V}} O_2maxHYPO Post training (CON: −6.5%; RMT: +14.2%). Post training, the CON group increased peak power output, whereas the RMT group had higher values of maximum ventilation. Both groups increased CLT_NOR duration (CON: +79.9%; RMT: +116.6%), but only the RMT group maintained a significantly higher CLT_NOR 10 days after training (CON: +56.7%; RMT: +91.3%). CLT_HYPO remained unchanged in both groups. Therefore, the respiratory muscle endurance training combined with cycle ergometer training enhanced aerobic capacity in hypoxia above the control values, but did not in normoxia. Moreover, no additional effect was obtained during constant-load exercise.     

The influence of a 1-year programme of brisk walking on endurance fitness and body composition in previously sedentary men aged 42–59 years

This study examined the influence of a 1-year brisk walking programme on endurance fitness and the amount and distribution of body fat in a group of formerly sedentary men. Seventy-two males, aged 42–59 years, body mass index 25.2 (0.3) kg·m^–2 [mean (SEM)], were randomly allocated to either a walking group (n = 48) or control group (n = 24). Brisk walking speed was evaluated using a 1.6-km track walk. Changes in endurance fitness were assessed by measuring blood lactate concentration and heart rate during submaximal treadmill walking. Body composition was determined by hydrostatic weighing and anthropometry; energy intake was assessed from 7-day weighed food inventories. Differences in the response of walkers and controls were examined using two-way analyses of variance. Forty-two walkers (87.5%) completed the study and averaged 27.9 (1.4) min·day^–1 of brisk walking (range 11–46). Brisk walking speed averaged 1.95 (0.03) m·s^–1 and elicited approximately 68 (1) % of maximum heart rate. Heart rate and blood lactate concentration during submaximal treadmill walking were significantly reduced in the walkers after 3, 6 and 12 months and the oxygen uptake at a reference blood lactate concentration of 2 mmol·l^–1 was increased by 3.2 ml·kg^–1. min^–1 (14.9%) in the walkers at 6 months (P< 0.01). Although skinfold thicknesses at anterior thigh and medial calf sites decreased significantly for the walkers, the response of the two groups did not differ significantly for other body composition variables or for energy intake.     

Effects of endurance training on hyperammonaemia during a 45-min constant exercise intensity

Summary Eleven laboratory-pretrained subjects (initial =54 ml·kg⁻¹·min⁻¹) took part in a study to evaluate the effect of a short endurance training programme [8–12 sessions, 1 h per session, with an intensity varying from 60% to 90% maximal oxygen consumption ] on the responses of blood ammonia (b[NH ₄ ⁺ ]) and lactate (b[la]) concentrations during progressive and constant exercise intensities. After training, during which did not increase, significant decreases in b[NH ₄ ⁺ ], b[la] and muscle proton concentration were observed at the end of the 80% constant exercise intensity, although b[NH ₄ ⁺ ] and b[la] during progressive exercise were unchanged. On the other hand, no correlations were found between muscle fibre composition and b[NH ₄ ⁺ ] in any of the exercise procedures. This study demonstrated that a constant exercise intensity was necessary to reveal the effect of training on muscle metabolic changes inducing the decrease in b[NH ₄ ⁺ ] and b[la]. At a relative power of exercise of 80% , there was no effect of muscle fibre composition on b[NH ₄ ⁺ ] accumulation.     

l-Carnitine and the recovery from exhaustive endurance exercise: a randomised, double-blind, placebo-controlled trial

We hypothesised that l-carnitine could accelerate recovery from exhaustive exercise since increased blood l-carnitine concentrations elicit a vasodilation in isolated animal vessels as well as in patients with peripheral vascular or coronary artery disease during exercise. Twelve subjects received either 2 g l-carnitine or a placebo in a study which was double-blind and crossover in design. Two hours after administration, the subjects performed a constant-load exercise test (CET₁) cycling at their individual anaerobic threshold to exhaustion. Three hours later this test was repeated (CET₂). After 4–14 days, each subject performed the same cycling tests after having taken the other substance. Exercise times of the 12 subjects were identical with l-carnitine (CET₁: 21.3±5.7 min; CET₂: 21.4±5.3 min) and placebo (CET₁: 21.9±6.2 min; CET₂: 20.4±4.8 min). Also, heart rate, oxygen consumption, respiratory exchange ratio, and blood lactate concentration were identical. In conclusion, 2 g of L-carnitine taken 2 h before a first of two constant-load exercise tests had no influence on the second tests performed 3 h after the first test compared with placebo.     

Blood ammonia and lactate concentrations during endurance exercise of differing intensities

Summary The purpose of this study was to examine the changes of blood ammonia concentration ([NH₃]_b) during endurance exercise of differing intensities on the cycle ergometer and to compare [NH₃]_b to the changes observed in the simultaneously monitored blood lactate acid concentrations ([la^–]_b) measurements. A group of 16 endurance-trained athletes participated in the first part of the study and performed exercise of 30 min duration in a randomized order at intensities of 85%, 95%, 100% and 105% of their individual anaerobic threshold (Th_an,ind; E85–E105) which had been determined beforehand by a cycle exercise test with stepwise increments in intensity. In the second part, 18 average endurance-trained sports students underwent exhausting intensive endurance exercise (IEE) with an intensity of 95% of Th_an,ind. An extensive endurance exercise (EEE) of the same duration at 85% of the Than,ind was carried out 2 days later. The [NH₃]_b increased constantly with increasing duration of all exercise. However, [la^–]_b only increased during exercise with intensities above the Th_an,ind (E105). The increase of [NH₃]_b was higher with higher exercise intensities. At IEE, [NH₃]_b was significantly higher from the 30th min than at EEE, whereas [la^–]_b increased from the 5th min. In conclusion, [la^–]_b responded more sensitively to the intensity of exercise than [NH₃]_b, but it is conceivable that in the future measurements of [NH₃]_b could be used to advise on the duration of endurance training. At present, however, the lack of experience and lack of appropriate values still hinders the systematic use of [NH₃]_b measurements in the physiological monitoring of sports training.     

Effects of training at simulated altitude on performance and muscle metabolic capacity in competitive road cyclists

Summary Differences between the effects of training at sea level and at simulated altitude on performance and muscle structural and biochemical properties were investigated in 8 competitive cyclists who trained for 3–4 weeks, 4–5 sessions/week, each session consisting of cycling for 60–90 min continuously and 45–60 min intermittently. Four subjects, the altitude group (AG), trained in a hypobaric chamber (574 torr=2300 m above sea level), and the other four at sea level (SLG). Before and after training work capacity was tested both at simulated altitude (574 torr) and at sea level, by an incremental cycle ergometer test until exhaustion. Work capacity was expressed as total amount of work performed. Venous blood samples were taken during the tests. Leg muscle biopsies were taken at rest before and after the training period. AG exhibited an increase of 33% in both sea level and altitude performance, while SLG increased 22% at sea level and 14% at altitude. Blood lactate concentration at a given submaximal load at altitude was significantly more reduced by training in AG than SLG. Muscle phosphofructokinase (PFK) activity decreased with training in AG but increased in SLG. All AG subjects showed increases in capillary density. In conclusion, work capacity at altitude was increased more by training at altitude than at sea level. Work capacity at sea level was at least as much improved by altitude as by sea level training. The improved work capacity by training at altitude was paralleled by decreased exercise blood lactate concentration, increased capillarization and decreased glycolytic capacity in leg muscle.