Sodium citrate and anaerobic performance: implications of dosage

Summary The use of sodium bicarbonate to improve anaerobic performance is well known but other buffering agents have been used with some success. Sodium citrate is one such substance which has been used but without the normal gastro-intestinal discomfort usually associated with sodium bicarbonate ingestion. The effects of five doses of sodium citrate (0.1 g·kg^–1 body mass, 0.2 g·kg^–1 body mass, 0.3 g·kg^–1 body mass, 0.4 g·kg^–1 body mass and 0.5 g·kg^–1 body mass) on anaerobic performance were studied in order to determine the minimal and most productive dose required for performance enhancement. A maximal test was performed for 1^–1, min on a cycle ergometer. Total work and peak power were measured at the end of the exercise period. Blood was drawn 1.5 h prior to the test session and measured for pH, partial pressure of carbon dioxide and concentrations of bicarbonate, base excess and lactate. In all but the control and placebo trials subjects then ingested one of five doses of sodium citrate which was contained in 400 ml of flavoured drink. Blood was again taken 90 min later and this was repeated after the completion of the exercise test. The greatest amount of work was completed in the trial with citrate given at 0.5 g·kg^–1 body mass (44.63 kJ, SD 1.5) and this was also true for peak power (1306 W, SD 75). The post-exercise blood lactate concentration was also highest during this trial 15.9 mmol·1^–1, SD 1.1. Post-exercise pH decreased significantly in all trials (P<0.0001) while the administration of the sodium citrate in all doses above 0.1 g·kg^–1 body mass significantly increased resting pH values. Blood bicarbonate concentrations also increased with dose in an almost linear fashion with the administration of sodium citrate. Bicarbonate increases were all significant, P<0.05 (citrate 0.1 g·kg^–1 body mass), P<0.01 (citrate 0.2 g·kg^–1 body mass, 0.3 g·kg^–1 body mass and 0.4 g·kg^–1 body mass) and P<0.005 (citrate 0.5 g·kg^–1 body mass). The administration of sodium citrate also significantly increased base excess values (citrate 0.1 g·kg^–1 body mass,P<0.01; 0.2 g·kg^–1body mass, P<0.001; 0.3 g·kg^–1 body mass, P<0.001; 0.4 g·kg^–1 body mass, P<0.001; 0.5 g·kg^–1 body mass, P<0.0001) above control and placebo values. All post-exercise base excess values were significantly lower than basal or pre-exercise values (P<0.0001). It was concluded that sodium citrate was an effective ergogenic aid for anaerobic performance of approximately 60-s duration, with the most effective of those dosages tested being 0.5 g·kg^–1 body mass.     

Cardiac responses to maximal anisotonic isometric contractions during handgrip and leg extension

A group of 14-healthy men performed anisotonic isometric contractions (AIC), for 60 s, at an intensity of 100% maximal voluntary contraction force (MVC) during handgrip (HG) and leg extension (LE). Heart rate (f _c), stroke volume index (SVI) and cardiac output index (Q_cI) were measured during the last 10 s of both AIC by an impedance reography method. Force (F) exerted by the subjects was recorded continuously and reported as a relative force (F _r) (% MVC). The F generated during MVC was greater for LE than for HG (502.I N compared to 374.6 N, P < 0.001). The rate of decrease in F _r was significantly slower for LE than HG for the first 25 s of the exercise (phase 1 of AIC). The F _r developed by the subjects at the end of AIC was 40% MVC for both LE and HG. The increase in f _c was greater for LE (63 beats · min^–1) than for HG (52 beats · min^–1), P < 0.01. The SVI decreased significantly from the resting level by 17.0 ml · m^–2 and by 18.2 ml · m^–2 for LE and HG, respectively. The Q_cI increased insignificantly for HG by 0.091 · min^–1 · m^–2 andsignificantly forLE by 0.561 · min^–1 · m^–2 (P < 0.001). It was concluded that although both AIC caused a significant decrease in SVI, greater increases in f _c and Q_c were observed for LE than for HG. The greater f _c and Q_c reported during LE was probably related to the greater relative force exerted by LE during phase 1 of AIC. It seems, therefore that central command might have dominated for phase 1 of AIC but that the muscle reflex also contributed significantly to the control of the cardiac response to the high intensity AIC.     

Evidence for a subgroup of essential hypertensives with non-suppressible excretion of aldosterone during sodium loading

Summary In patients with grade I and II essential hypertension studied during sodium loading (Na⁺ excretion above 175 meq·d^–1) we found a bimodal behaviour of aldosterone excretion and could distinguish two groups of patients: In the major part of essential hypertensives sodium loading led to a suppression of aldosterone excretion below 6 µg·d^–1, which is the highest control value during sodium loading, with an average of 2.7±1.4 (SD) µg·d^–1. Aldosterone excretion in a second group of patients was not suppressible below 6 µg·d^–1 despite forced sodium loading; it resulted in an average value of 10.0±3.0 (SD) µg·d^–1. During sodium deprivation or free sodium intake, aldosterone excretion in the first group of patients followed exactly the behaviour of normotensive controls, while in the second group of essential hypertensives the correlation of aldosterone excretion and log. Na excretion or log. Na⁺/K⁺ ratio in 24 h urine (r=–0.59) was far below the control value ofr=–0.87. Serum potassium concentration during sodium loading was significantly (p<0.001) lower (3.81±0.44 meq·l^–1) in the essential hypertensives with non-suppressible aldosterone excretion compared to those with suppressible aldosterone excretion (4.26±0.37 meq·l^–1). The blood pressure response to treatment with 200 mg spironolactone·d^–1 was better (p<0.05) in patients with non-suppressible aldosterone excretion compared to the essential hypertensives with normal aldosterone regulation. The plasma renin activity of both groups of patients was not significantly different, however, a tendency prevailed towards lower PRA-values in the patient group with non-suppressible aldosterone excretion during sodium loading.With the technical help of Mrs. R. Schendschilorz and Mrs. G. Suckau     

The effect of a high carbohydrate diet on running performance during a 30-km treadmill time trial

Summary The purpose of the present study was to examine the influence of a high carbohydrate diet on running performances during a 30-km treadmill time trial. Eighteen runners (12 men and 6 women) took part in this study and completed a 30-km time trial on a level treadmill without modifying their food intake (trial 1). The runners were then randomly assigned to a control or a carbohydrate (CHO) group. The CHO group supplemented their normal diets with additional carbohydrate in the form of confectionery products during the 7 days before trial 2; the control group matched the increased energy intake of the CHO group by consuming additional fat and protein. The mean (SEM) carbohydrate intake of both groups was 334 (22) g before trial 1, after which the CHO group consumed 566 (29) g · day^–1 for the first 3 days and 452 (26) g · day^–1 for the remaining 4 days of recovery. Although there was no overall difference between the performance times for the two groups during trial 2, the CHO group ran faster during the last 5 km of trial 2 than during trial^–1 [3.64 (0.24) m · s^–1 vs 3.44 (0.26) m · s^–1 P < 0.05] . Furthermore, the 6 men in the CHO group ran the 30 km faster after carbohydrate loading [131.0 (5.4) min vs 127.4 (4.9) min;P < 0.05], whereas there was no such improvement in times of the men in the control group. Blood glucose concentrations of both groups decreased below pre-exercise values during trial^–1 (P < 0.001), but only the control group had a decrease in blood glucose concentrations during trial 2 (P < 0.001). There were no differences between the concentrations of plasma catecholamines of the control group during the two trials. However, the adrenaline concentrations of the CHO group were lower (P < 0.05) during trial 2 than during trial 1, even though they ran faster during trial 2. These results confirm that dietary carbohydrate loading improves endurance performance during prolonged running and that confectionery can be used as an effective means of supplementing the normal carbohydrate intake in preparation for endurance races.     

Exhausting handgrip exercise reduces the blood flow in the active calf muscle exercising at low intensity

The calf and forearm blood flows (Q _calf and Q _forearm respectively), blood pressure, heart rate and oxygen uptake of six men and women were studied during combined leg and handgrip exercise to determine whether a reduction of exercise-induced hyperaemia would occur in the active leg when exhausting rhythmic handgrip exercise at 50% maximal voluntary contraction (MVC) was superimposed upon rhythmic plantar flexion lasting for 10 min at 10% MVC (P₁₀) prior to this combined exercise. The Q _calf and Q _forearm were measured by venous occlusion plethysmography during 5-s rests interposed during every minute of P₁₀ exercise and immediately after combined exercise. The muscle sympathetic nerve activity (MSNA) changes were also recorded during leg exercise alone and combined exercise. During plantar flexion performed 60 times · min^–1 with a load equal to 10% MVC (P₁₀), Q _calf was maintained at a constant level, which was significantly higher than the resting value (P < 0.001). When rhythmic handgrip contraction at 50% MVC (H₅₀) and P₁₀ were performed simultaneously, the combined exercise was concluded due to forearm exhaustion after a mean of 51.2 (SEM 5.5) s. At exhaustion, Q _calf had decreased significantly from 20.6 (SEM 3.0) ml · 100 ml^–1 · min^–1 (10th min during P₁₀ exercise) to 15.3 (SEM) ml · 100 ml^–1 · min^–1 (P = 0.001), whereas Q _forearm had increased significantly (0.001 < P < 0.01) from 8.6 (SEM 1.9) ml · 100 ml^–1 · min^–1 (10th min of P₁₀ exercise) to 26.2 (SEM 3.2) ml · 100 ml^–1 · min^–1. The mean blood pressure remained at an almost constant level during the 3rd to 10th min of P₁₀ exercise and increased markedly when H₅₀ was added. The calf vascular conductance during combined exercise decreased significantly (0.001 < P < 0.01) compared with that at the 10th min of P₁₀ alone. Although the MSNA (expressed as burst rate) remained unchanged during P₁₀ exercise for 10 min, it increased markedly when exhausting H₅₀ and P₁₀ exercise were performed simultaneously. These findings indicated that superimposition of exhausting handgrip exercise at 50% MVC caused a vasoconstriction in the exercising calf due to increased MSNA, which counteracted the vasodilatation in this active muscle.     

The effect of range of motion and isometric pre-activation on isokinetic torques

Summary The effect of an increased angle of excursion and isometric pre-activation on isokinetic torques of knee extensors was investigated in five male subjects, mean age 35.0 years, SD 9.6. Peak torque and isoangular torque at 0.52 rad from full knee extension (FKE) were measured when contractions were carried out at 3.14, 4.19 and 5.24 rad·s^–1 starting: 1) from a standard knee angle (SA) of 1.57 rad from FKE, 2) from the same starting angle as SA, plus an isometric preload (P) equivalent to 25% of isometric maximal voluntary contraction and 3) from an increased angle of knee flexion (1A), 2.09 rad from FKE plus P. Surface integrated electromyograms (iEMG) of the vastus lateralis muscle in SA and IA+P were also recorded. The IA+P had the effect of increasing peak torque, as compared to SA, on average by 12.0%, SD 7.5% (P<0.001) at 3.14 rad·s^–1, 19.5%, SD 5.5% (P<0.001) at 4.19 rad·s^–1, 21.6%, SD 10.7% (P<0.001) at 5.24 rad·s^–1 and of increasing mean iEMG by 15.7%, SD 7.0% (P<0.001) at 5.24 rad·s^–1. The IA+P also had the effect of increasing the angle from FKE at which peak torque occurred: from means of 0.80 rad, SD 0.11 to 1.00 rad, SD 0.07 at 3.14 rad·s^–1, from 0.65 rad, SD 0.11 to 0.92 rad, SD 0.09 at 4.19 rad·s^–1 and from 0.60 rad, SD 0.11 to 0.88 rad, SD 0.11 at 5.24 rad·s^–1 (P<0.0001). Mean isoangular torque rose by 12.6%, SD 5.1% at 5.24 rad·s^–1 (P<0.01); mean iEMG values by 8.5%, SD 5.2% (P<0.02) and 11.6%, SD 6.4%(P<0.02) at 4.19 and 5.24 rad·s^–1, respectively. The mean time for both peak and isoangular torque development was significantly increased (P<0.0001). The effect of SA+P on peak torque was smaller than that of IA+P, a mean increment of 3.4%, SD 6% (P<0.02) only being observed at 5.24 rad·s^–1. The increase in isoangular torque was of the same magnitude as that of IA+P. It was concluded that when isokinetic contractions were carried out from a standard position of the knee at a right angle, neuromuscular activation at high angular velocities (>4.19 rad·s^–1) was submaximal. The underestimation of torque seemed to be counteracted by starting the contraction from a flexed position and by utilizing a submaximal P.     

Long-term elevations of dietary sodium produce parallel increases in the renal excretion of urodilatin and sodium

The effects of dietary sodium intake on the renal excretion of urodilatin and of sodium were examined in six healthy male subjects. The 24-day study period was divided into three phases of 8 days each. Subjects Ingested 2.8 mequiv sodium (kg body weight)^–1 day^–1 during the first phase, 5.6 mequiv (kg body weight)^–1 day^–1 during the second phase, and 8.4 mequiv (kg body weight)^–1 day^–1 during the third phase. The excretion of both sodium (P<0.002) and urodilatin (P<0.006) increased in response to the increasing dietary sodium, while urine flow did not change. Urinary urodilatin excretion correlated closely with renal sodium excretion (P<0.001). Serum aldosterone levels (P<0.01) as well as serum renin levels (P<0.05) significantly decreased with increasing sodium intake. Plasma [Arg]vasopressin levels increased significantly (P<0.05). Plasma atrial natriuretic factor and cGMP levels as well as urinary cGMP excretion rates were unaltered by the changes in sodium intake. We conclude from these results that the renal natriuretic peptide, urodilatin, but not the main cardiac member of the natriuretic peptide family may be involved in the regulation of day-to-day sodium balance.     

Training does not affect protein turnover in pre- and early pubertal female gymnasts

This study compared protein turnover in ten young female gymnasts [10.3 (0.5) years] engaged in regular intense physical training with ten age-matched controls [9.4 (0.6) years)]. Nitrogen flux ( Q), protein synthesis (PS), protein degradation (PD) and net protein turnover (NPB = PS–PD) were measured following a single oral dose of [¹⁵N]-glycine. The habitual dietary intake of each subject was assessed using a 7-day food record, with food portions being weighed before ingestion. The gymnasts had a low total energy intake which was unbalanced in the proportions of lipid, carbohydrate and protein. Protein flux was 7.19 (0.35) g.kg^–1.day^–1 in the gymnasts and 7.53 (0.81) g.kg^–1.day^–1 in the controls; protein synthesis was 6.06 (0.27) g.kg^–1.day^–1 in the gymnasts and 6.53 (0.74) g.kg^–1.day^–1 in the controls; protein degradation was 5.45 (0.38) g.kg^–1.day^–1 in the gymnasts and 5.27 (0.74) g.kg^–1.day^–1 in the controls. All data are presented as means and standard errors of the mean (SEM). There were no statistical differences for protein flux, protein synthesis or protein degradation between the two groups. However, NPB was lower (–14%) in the trained gymnasts than in the control group ( P <0.05), which might be explained by a greater protein ingestion in the control group on the day of the protocol ( P <0.05). These results show that in pre- and early pubertal female gymnasts intense training does not exert a demonstrable effect on protein turnover.     

Effect of one- and two-leg training on arm and two-leg maximum aerobic power

Summary The purpose of this study was to examine the effect of one- and two-leg training on arm and two-leg maximum aerobic power. Seven subjects cycle-trained both legs simultaneously for 30 min·day^–1, 4 days·week^–1 for 4 weeks. Nine subjects cycle-trained each leg 15 min·day^–1, 4 days· week^–1 for 4 weeks. Both groups trained at a heart rate equal to that measured at 75% of their two-leg maximum aerobic power. Thus, during each training session the groups performed 30 min of work at the same heart rate intensity. Five subjects served as a non-training control group. Arm and leg maximum oxygen uptake tests were conducted before and after training. Only two-leg training induced significant gains in arm aerobic power (P<0.0003), whereas both modes of training resulted in signifcant increases in two-leg aerobic power (P<0.0008). The data demonstrate that improvements in arm aerobic power were dependent on the quantity of leg muscle mass involved in the training, whereas gains in two-leg aerobic power occurred regardless of whether the legs were trained separately or simultaneously.     

Post-exercise rehydration in man: effects of electrolyte addition to ingested fluids

This study examined the effects on water balance of adding electrolytes to fluids ingested after exercise-induced dehydration. Eight healthy male volunteers were dehydrated by approximately 2% of body mass by intermittent cycle exercise. Over a 30-min period after exercise, subjects ingested one of the four test drinks of a volume equivalent to their body mass loss. Drink A was a 90 mmol·l^–1 glucose solution; drink B contained 60 mmol·l^–1 sodium chloride; drink C contained 25 mmol·l^–1 potassium chloride; drink D contained 90 mmol·l^–1 glucose, 60 mmol·l^–1 sodium chloride and 25 mmol·l^–1 potassium chloride. Treatment order was randomised. Blood and urine samples were obtained at intervals throughout the study; subjects remained fasted throughout. Plasma volume increased to the same extent after the rehydration period on all treatments. Serum electrolyte (Na⁺, K⁺ and Cl^–) concentrations fell initially after rehydration before returning to their pre-exercise levels. Cumulative urine output was greater after ingestion of drink A than after ingestion of any of the other drinks. On the morning following the trial, subjects were in greater net negative fluid balance [mean (SEM);P<0.02] on trial A [745 (130) ml] than on trials B [405 (51) ml], C [467 (87) ml] or D [407 (34) ml]. There were no differences at any time between the three electrolyte-containing solutions in urine output or net fluid balance. One hour after the end of the rehydration period, urine osmolality had fallen, with a significant treatment effect (P=0.016); urine osmolality was lowest after ingestion of drink A. On the morning after the test, subjects were in greater net negative sodium balance (P<0.001) after trials A and C than after trials B and D. Negative potassium balance was greater (P<0.001) after trials A and B than after C and D. Chloride balance was positive after drink D and a smaller negative balance (P<0.001) was observed after drink B than after A and C. These results suggest that although the measured blood parameters were similar for all trials, better whole body water and electrolyte balance resulted from the ingestion of electrolyte-containing drinks. There appeared, however, to be no additive effect of including both sodium and potassium under the conditions of this experiment.     

Pathways of phosphate transport in chick jejunum

The effect of vitamin D₃ on intestinal phosphate (P_i) absorption was studied in everted sacs prepared from jejunum of either vitamin D-deficient (–D) or vitamin D-replete (+D) chicks. Vitamin D₃ stimulates the maximal velocity (V _max) of a mucosal active P_i transport mechanism from 125 to 314 nmol·min^–1·g^–1 tissue.K _m of this process remains virtually unchanged (–D: 0.15 mmol·l^–1; + D: 0.18 mmol·l^–1).Active P_i entry into the epithelium depends on extracellular Na⁺. Reduction of buffer Na⁺ reducesV _max in the + D group to 182 nmol·min^–1·g^–1 tissue but has no significant effect in the –D animals (V _max=105 nmol·min^–1·g^–1 tissue). In this group, the predominant effect of Na⁺ substitution is a shift ofK _m to 1.13 mmol·l^–1, whileK _m in the +D group is changed only to 0.53 mmol·l^–1.Transeptithelial P_i transport in the + D group involves the mucosal phosphate pump and hence an intracellular pathway, proceeding at a rate of 48 nmol·min^–1·g^–1 tissue. This is in contrast to –D P_i transfer (8 nmol·l^–1·g^–1 tissue) which is by a diffusional, Na⁺-insensitive, and presumably paracellular pathway.Transepithelial calcium transport (–D: 3.3 nmol·min^–1·g^–1; + D: 7.6 nmol·min^–1·g^–1 tissue) does not require the presence of extracellular Na⁺ and apparently involves pathways different from those of the P_i absorptive system.Presented in part at the Annual Meeting of the Austrian Biochemical Society, Salzburg, September 1978     

Changes in structure and function of the human left ventricle after acclimatization to high altitude

Summary To analyse the role of changes in structure and function of the left ventricle in determining cardiac function at rest and during exercise, several two-dimensional and Doppler echocardiographic measurements were performed on 11 healthy subjects immediately before an Himalayan expedition (Nun, 7135 m), during acclimatization (3 weeks) and 14 days after the return. At rest decreases were found in cardiac index (CI) (3.23 l · min^–1 · m^–2, SD 0.4 vs 3.82 l · min^–1 · m^–2, SD 0.58,P < 0.01), left ventricular mass (55.3 g · m^–2, SD 9.4 vs 65.2 g · m^–2, SD 13.5,P < 0.005) and left ventricular end-diastolic volume (LVEDV) (53.9 ml · m^–2, SD 6.9 vs 64.8 ml · m^–2, SD 9.1,P < 0.001) after acclimatization; by contrast the coefficient of peak arterial pressure to left ventricular end-systolic volume (PAP/ESV) (7.8, SD 1.6 vs 6.0, SD 1.8,P < 0.005) and mean wall stress [286 kdyn · cm^–2, SD 31 vs 250 kdy · cm^–2, SD 21 (2.86 N · cm^–2, SD 0.31 vs 2.50 N · cm^–2, SD 0.21),P < 0.005] increased. After return to sea level, low values of CI and mass persisted despite a return to normal of LVEDV and preload. A reduction of PAP/ESV was also observed. At peak exercise, PAP/ESV (8.7, SD 2.4 vs 12.8, SD 2.0,P < 0.0025), CI (9.8 l · min^–1 m^–2, SD 2.5 vs 11.61 · min^–1 · m^–2, SD 1.6,P < 0.05) and the ejection fraction (69%, SD 6 vs 76%, SD 4,P < 0.05) were lower after return to sea level than before departure. The depressed left ventricular performance after prolonged exposure to hypoxia may be related to changes in structure and function including reduction in preload, loss of myocardial mass and depression of inotropic state.     

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.     

Physical activity and energy expenditure in lean and obese adult human subjects

Summary We compared the physical activity of 11 lean and 11 obese men and women over a 7-day period. There were no significant differences in either the amount of movement recorded with an accelerometer (9.5 (SD 3.9) vs 9.9 (SD 2.6) kcounts · day^–1), or in the energy expenditure due to physical activity reflected by the difference between the average daily metabolic rate measured by the doubly labelled water, technique and the sleeping metabolic rate measured in a respiration chamber and adjusted for fat-free mass: 112 (SD 33) vs 118 (SD 22) kJ · kg^–1·day^–1.The obese showed a non-significant loos of body of 0.5 (SD 1.1) kg, probably due to reduced intake during the 7-day intake recording period.     

Effect of anaerobic and aerobic exercise of equal duration and work expenditure on plasma growth hormone levels

Summary Growth hormone (GH) and lactic acid levels were measured in five normal males before, during and after two different types of exercise of nearly equal total duration and work expenditure. Exercise I (aerobic) consisted of continuous cycling at 100 W for 20 min. Exercise II (anaerobic) was intermittent cycling for one minute at 285 W followed by two minutes of rest, this cycle being repeated seven times. Significant differences (P<0.01) were observed in lactic acid levels at the end of exercise protocols (20 min) between the aerobic (I) and anaerobic (II) exercises (1.96±0.33 mM·l^–1 vs 9.22±0.41 mM·l^–1, respectively). GH levels were higher in anaerobic exercise (II) than in aerobic (I) at the end of the exercise (20 min) (2.65±0.95 g·l^–1 vs 0.8±0.4 g·l^–1;P<0.10) and into the recovery period (30 min) (7.25±6.20 g·l^–1 vs 2.5±2.9 g·l^–1;P<0.05, respectively).     

Is exhaustive training adequate preparation for endurance performance?

Summary Our purpose was to test the significance of exhaustive training in aerobic or endurance capacity. The extent of adaptations to endurance training was evaluated by assessing the increase in physical performance capability and oxidative markers in the organs of rats trained by various exercise programs. Rats were trained by treadmill running 5 days · week^–1 at 30 m · min^–1 for 8 weeks by one of three protocols:T ₁ — 60 min · day^–1;T ₂ — 120 min · day^–1; andT ₃ — 120 min · day^–1 (3 days · week^–1) and to exhaustion (2 days · week^–1). GroupsT ₂ andT ₃ ran for longer thanT ₁ in an endurance exercise test (P<0.05), in which the animals ran at 30 m · min^–1 to exhaustion; no difference was observed between groupsT ₂ andT ₃. All 3 trained groups showed a similar increase (20–27%) in the fast-twitch oxidative-glycolytic (FOG) fibers with a concomitant decrease in the fast-twitch glycolytic (FG) fiber population in gastrocnemius (p<0.05). The capillary supply in gastrocnemius increased with the duration of exercise (p<0.05): no difference was found between groupsT ₂ andT ₃. Likewise, no distinction was seen between groupsT ₂ andT ₃ in the increase in succinate dehydrogenase activity in gastrocnemius and the heart. These results suggest that the maximal adaptive response to endurance training does not require daily exhaustive exercise.     

Increased activity of the Na-K-ATPase in red cell-ghosts of patients with Cushing's Syndrome: Possible significance for the pathogenesis of glucocorticoid-induced hypertension

Summary The Na-K-ATPase activity of erythrocyte ghosts was increased in 6 patients with Cushing's syndrome compared with 28 control subjects (0.986±0.291 versus 0.259±0.1 µM P_i·h^–1·mg^–1,p<0.001). Ouabain insensitive Mg-ATPase activity was similar in both groups. These data support the concept of an activation of the Na-pump in patients with glucocorticoid excess.     

Effects of isokinetic training of the knee extensors on high-intensity exercise performance and skeletal muscle buffering

Twenty-three subjects isokinetically trained the right and left quadriceps femoris, three times per week for 16 weeks; one group (n=13) trained at an angular velocity of 4.19 rad · s^–1 and a second group (n=10), at 1.05 rad · s^–1. A control group (n=10) performed no training. Isometric endurance time at 60% quadriceps maximum voluntary contraction (MVC), mean power output and work done (W) during all-out cycling, and the muscle buffer value (B) and carnosine concentration of biopsy samples from the vastus lateralis, were all assessed before and after training. The two training groups did not differ significantly from each other in their training response to any of these variables (P < 0.05). No significant difference in either 60% MVC endurance time or impulse [(endurance time × force) at 60% MVC] was observed for any group after the 16 week period (P > 0.05). However, the post-training increase (9%) in W during high-intensity cycling was greater in the training group than in the control group (P=0.04). NeitherB nor carnosine concentration showed any significant change following training (P=0.56 andP=0.37, respectively). It is concluded that 16 weeks of isokinetic training of the knee extensors enables subjects to do more work during high-intensity cycling. Although the precise adaptations responsible for the improved performance have yet to be identified, they are unlikely to include an increase inB.     

Effect of short-term energy intake level and exercise on oxygen consumption in men

Summary The influence of short-term energy intake and cycle exercise on oxygen consumption in response to a 1.5 MJ test meal was investigated in ten young, adult men. On the morning after a previous day's low-energy intake (LE regimen) of 4.5 MJ, the mean resting oxygen consumption increased by 0.7 ml · kg^–1 · min^–1 after the test meal (P<0.025). After a high-energy intake (HE regimen) of 18.1 MJ, the resting measurement was unchanged (+0.4 ml · kg^–1 · min^–1) after the meal (n.s.). These trends are the reverse of what would be expected if oxygen consumption in response to feeding is a factor in the acute control of body weight. The mean fasting oxygen consumption during cycle exercise at 56% of (constant work) for both LE and HE prior intakes was not different at 31.1 ml · kg^–1 · min^–1. Oxygen consumption during exercise increased after feeding by 0.5 ml · kg^–1 · min^–1 on the LE regimen (n.s.) and decreased by 1.2 ml · kg^–1 · min^–1 on the HE regimen (n.s.). These results are also the reverse of what would be expected if oxygen consumption in response to exercise is related to short-term energy intake.     

Influence of acute maximal exercise on lecithin: cholesterol acyltransferase activity in healthy adults of differing aerobic performance

Summary To document the possible influence of a single episode of maximal aerobic stress on the serum lecithin: cholesterol acyltransferase (LCAT) activity in subjects with differing histories of training, two groups of healthy male adults [controls (C),n = 18, 28.6 years, SD 5.2, 50.1 ml · kg^–1 · min^–1 maximal O₂ uptake (VO_2max), SD 5.3; endurance trained athletes (T),n = 18, 31.4 years, SD 8.8, 65.0 ml · kg^–1 · min^–1 VO_2max, SD 2.8] were examined in a maximal aerobic stress test. In addition to the routine assessment of lipid status, LCAT activity was measured immediately before and after exercise. At rest nearly identical LCAT activity values were found in both groups: C 64.4 nmol · ml^–1 · h^–1, SD 16.7 vs T 65.0 nmol · ml^–1 · h^–1, SD 20.9. The post-exercise LCAT values induced by the maximal stress test increased significantly to (C) 95.7 nmol · ml^–1 · h^–1, SD 23.5, +48.6%,P<0.001; (T) 83.5 nmol · ml^–1 · h^–1, SD 24.3, +29.1%,P<0.01. Neither the pre nor the post-exercise individual LCAT activity values showed any significant correlation to the corresponding data on physical performance.