Effects of iron deficiency and exercise on myoglobin in rats

Summary The effects of iron deficiency and endurance training on muscle myoglobin (Mb), body weights, and blood lactic acid concentration were studied in rats. Fifty animals were divided into four groups: anemic trained (AT), normal trained (NT), anemic sedentary (AS), and normal sedentary (NS). Following 5 weeks of dietary control, the mean hemoglobin values for the AT and AS rats were 0.013±0.002 mmol·l^–1 (8.7±1.4 g·dl^–1) and 0.014±0.003 mmol·l^–1 (9.2±1.7 g·dl^–1) respectively, and did not significantly change throughout the study. AT and NT rats were run on a motor driven treadmill 4 days/week for 6 weeks up to a pre-established time of 90 min. Following the training, body weights of the AT (157±13 g) and NT (153±13 g) rats were lower than their respective sedentary groups AS (172±9 g) and NS (176±15 g). Resting blood lactic acid concentration following training was lower in both trained groups, AT (3.3±2.0 mM) and NT (2.3±1.9 mM) compared to AS (8.2±2.6 mM) and NS (3.8±1.6 mM). Training increased Mb concentration in hearts of both the anemic and normal trained groups (AT, 0.66±0.13 mg·g^–1; NT, 0.95±0.08 mg·g^–1) compared to the sedentary groups (AS, 0.44±0.08 mg·g^–1; NS, 0.70±0.13 mg·g^–1). Only the AT rats showed an increase in skeletal muscle Mb. This study provides evidence that myoglobin may limit aerobic metabolism.     

Supramaximal cycle tests do not detect seasonal progression in performance in groups of elite speed skaters

Summary Seven female and eight male elite junior skaters performed cycle ergometer tests at four different times during the 1987/1988 season. The tests consisted of a Wingate-type 30-s sprint test and a 2.5-min supramaximal test. The subjects were tested in February, May and September 1987 and in January 1988. Maximal oxygen consumption was measured during the 2.5-min test. With the exception of the maximal oxygen consumption of the women in May which was about 6% lower than in the other three tests, no seasonal changes in the test results could be observed —this, in spite of a distinct increase in training volume (from 10 to more than 20 h · week^–1) and training intensity in the course of the season. When the test data were compared to those of elite senior skaters, it appeared that the junior skaters showed the same values for mean power output during the sprint test [14.2 (SD 0.4) W · kg^–1 for the men and 12.6 (SD 0.5) W · kg^–1 for the women] and maximal oxygen consumption [63.1 (SD 2.8) ml· kg^–1 · min^–1 for the men and 55.3 (SD 3.5 ml · kg^–1 · min^–1 for the women, respectively] as found for senior skaters. It seemed, therefore, that the effects of training in these skaters had already levelled off in the period before they participated in this investigation. In contrast to previous studies, no relationship could be shown between the test results and skating performance. This was most likely due to the homogenous character of the groups (mean standard deviations in power and oxygen consumption were only 5%). It was concluded that the present cycle tests used to measure aerobic and anaerobic power were obviously not of use in evaluating seasonal changes in performance in these groups of highly trained athletes.     

Effect of exercise training on aortic collagen content in spontaneously hypertensive rats (SHR)

Summary We investigated the effects of exercise training on the amount of aortic collagen and systolic blood pressure in spontaneously hypertensive rats (SHR). Ten-week old SHR were trained either by forced treadmill running (26.8 m·min^–1 h·day^–1, five times a week, 0% incline) or by voluntary running in revolving wheels (7,800 m·day^–1 at peak) for 8 weeks. Succinate dehydrogenase (SDH) activity measured as a marker of an endurance training effect was 13% higher (P<0.01) in the soleus of forced-exercised animals than in that of sedentary ones. (6.56±0.17 mol·g^–1·min^–1; mean ± SEM), whereas SDH activity in that of voluntarily-exercised group was found to be at the same level as in sedentary animals. The systolic blood pressure after training increased by 26.4 in sedentary, 21.1 in voluntarily-exercised, and 33.9 mm Hg in forced-exercised rats, when compared with the value of each group at the beginning of the training programm. A significant difference was observed in the increment of blood pressure only between the voluntarily- and forced-exercised groups (P<0.05). The amount of aortic collagen in voluntarily-trained rats (96.5±2.0 mg·g tissue^–1, 39.8±0.7 mg·100 mg protein^–1) was significantly less than that in forced-trained rats (P<0.05). These results suggest that voluntary, mild exercise training may be more effective in the reduction of collagen accumulation in the aorta associated with the suppression of blood pressure increase than forced, vigorous exercise training in SHR.     

Physiological and biomechanical comparison of roller skating and speed skating on ice

Summary Eight well trained marathon skaters performed all-out exercise tests during speed skating on ice and roller skating. To compare these skating activities in relation to the concept of training specificity, relevant physiological (V _O2,V _E, RER and heart rate) and biomechanical variables (derived from film and video analysis) were measured. There were no significant differences between oxygen uptake (50.5±8.0 and 53.3±6.7 ml·min^–1·kg^–1), ventilation (102.4±11.2 and 116.0±11.1 l·min^–1) or heart rate (174±12.2 and 176±14.5 min^–1) between speed and roller skating. In roller skating a higher RER (1.16±0.1 cf. 1.05±0.1) was found. Power, work per stroke and stroke frequency were equal. Due to a higher coefficient of friction the maximal roller skating speed was lower. The effectiveness of push-off and parameters concerning the skating techniques showed no differences. In roller skating a 7.5% higher angle of the upper leg in the gliding phase occurred. It is speculated that the blood flow through the extensor muscles might be higher in roller skating. It is concluded that roller skating can be considered as a specific training method which may be used by trained speed skaters in the summer period.     

Force generation capacity of knee extensor muscles in speed skaters

The force generation capacities during a single as well as repetitive maximal knee extensions were investigated in speed skaters in relation to the cross-sectional area (CSA) of quadriceps femoris muscles. The subjects were 15 male and 12 female speed skaters, and an age-matched untrained group (20 men and 21 women). An isokinetic dynamometer was used to determine force output at three constant velocities of 1.05, 3.14 and 5.24 rad · s^–1 and to perform 50 repetitive maximal contractions at 3.14 rad · s^–1. The CSA was measured by using a B-mode ultrasound technique at the midpoint of the thigh length. The isokinetic force produced at each test velocity was significantly correlated to CSA in all the subjects (r = 0.867–0.920, P < 0.05). There was no significant difference in force (F) per unit CSA (F · CSA^–1) at the three test velocities between the speed skaters and untrained subjects within the same sex. In both the speed skaters and untrained subjects, the women showed significantly lower F · CSA^–1 at 3.14 and 5.24 rad · s^–1 than the men. The means of force output ( ) of every five consecutive and all trials during the repetitive maximal bout were significantly correlated to CSA in all the subjects (r = 0.889–0.934, P < 0.05). Compared to the untrained subjects, the speed skaters showed significantly higher ( ) for every five consecutive contractions even when calculated per unit of CSA ( · CSA^–1), and had lower percentage of decline of F during a trial span between the 6th–10th and 41th–45th trials. For the untrained subjects, · CSA^–1 for every five consecutive contractions was significantly lower in the women than in the men. For the speed skaters, the men showed significantly higher · CSA^–1 than the women during a trial span from the 1st–5th trial to the 31th–35th trial, although there was no significant sex difference in the ratio on and after the 36th–40th trial. From these results, it is concluded that the speed skaters show a higher muscle performance in a repetitive maximal contraction task rather than in a single contraction compared to the untrained subjects. In addition, judging from the results for the speed skaters, the women might be less trainable than the men in the · CSA^–1 during a single contraction at a fast velocity as well as repetitive maximal contractions.     

Bovine colostrum supplementation does not affect plasma buffer capacity or haemoglobin content in elite female rowers

It has been reported that bovine colostrum (BC) supplementation improves buffer capacity () during exercise, but whether the improvement results from changes in tissue and/or blood buffer systems has not been determined. The purpose of the present study was to examine the effect of supplementation with BC on blood buffer systems. Thirteen elite females rowers were supplemented with 60 g·day^–1 of either BC (n=6) or whey protein (WP, n=7) during 9 weeks of pre-competition training in a randomised, double-blind, placebo-controlled, parallel design. All subjects undertook the study as a group and completed the same training program. Resting haemoglobin (Hb) concentration and plasma buffer capacity (p) (determined by titration with HCl) were measured pre- and post-supplementation. There were no differences in macronutrient intakes (P>0.56) or training volumes (P>0.99) between BC and WP during the study period. There were no differences in Hb [BC 13.28 (0.28) mg·dl^–1, WP 13.70 (0.26) mg·dl^–1; P=0.45] or p [BC 14.8 (1.1) nmol HCl·ml^–1·pH^–1, WP 14.8 (0.5) nmol HCl·ml^–1·pH^–1; P=0.68] between groups at week 0. p increased in both groups during the study period (P<0.001), but the increases were not significantly different between groups (P=0.52). Hb did not change significantly in either group (P=0.35). These data indicate that supplementation with BC does not affect p or Hb. We therefore suggest that adaptations in tissue buffer systems are responsible for the previously reported increases in buffer capacity that result from BC supplementation.     

Endurance training attenuates exercise-induced oxidative stress in erythrocytes in rat

The aim of this study was to investigate whether endurance training reduces exercise-induced oxidative stress in erythrocytes. Male rats (n=54) were divided into trained (n=28) and untrained (n=26) groups. Both groups were further divided equally into two groups where the rats were studied at rest and immediately after exhaustive exercise. Endurance training consisted of treadmill running 1.5 h·day^–1, 5 days a week for 8 weeks, reaching the speed of 2.1 km·h^–1 at the fourth week. For acute exhaustive exercise, graded treadmill running was conducted reaching the speed of 2.1 km·h^–1 at the 95th min, 10% uphill, and was continued until exhaustion. Acute exhaustive exercise increased the erythrocyte malondialdehyde level in sedentary but not in trained rats compared with the corresponding sedentary rest and trained rest groups, respectively. While acute exhaustive exercise decreased the erythrocyte superoxide dismutase activity in sedentary rats, it increased the activity of this enzyme in trained rats. On the other hand, acute exhaustive exercise increased the erythrocyte glutathione peroxidase activity in sedentary rats; however, it did not affect this enzyme activity in trained rats. Erythrocyte glutathione peroxidase activity was higher in trained groups compared with untrained sedentary group. Neither acute exhaustive exercise nor treadmill training affected the erythrocyte total glutathione level. Treadmill training increased the endurance time in trained rats compared with sedentary rats. The results of this study suggest that endurance training may be useful to prevent acute exhaustive exercise-induced oxidative stress in erythrocytes by up-regulating some of the antioxidant enzyme activities and may have implications in exercising humans.     

The acute effect of 30 min of moderate exercise on high density lipoprotein cholesterol in untrained middle-aged men

Summary Fifteen middle-aged, untrained (defined as no regular exercise) men (mean age 49.9 years, range 42–67) cycled on a cycle ergometer at 50 rpm for 30 min at an intensity producing 60% predicted maximum heart rate [(f _c,max), wheref _{c, max} = 220 - age]. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglyceride (Tg) concentrations were measured from fasting fingertip capillary blood samples collected at rest, after 15 and 30 min of exercise, and at 15 min post-exercise. The mean HDL-C level increased significantly from the resting level of 0.85 mmol · l^–1 to 0.97 mmol · 1^–1 (P<0.05) after 15 min of exercise, increased further to 1.08 mmol · 1^–1 (P<0.01) after 30 min of exercise and remained elevated at 1.07 mmol · 1^–1 (P<0.01) at 15 min post-exercise. These increases represented changes above the mean resting level of 14.1%, 27.1% and 25.9% respectively. The HDL-C/LDL-C ratio increased significantly from a resting ratio of 0.20 to 0.26 after 30 min of exercise (P < 0.01) and to 0.24 at 15 min post-exercise (P<0.05). The mean Tg level increased significantly from a resting level of 0.88 mmol · 1^–1 to 1.05 mmol · 1^–1 after 15 min, and to 1.06 mmol · I^–1 after 30 min of exercise (P<0.05 at each time). The TC/HDL-C ratio decreased significantly (P=0.05) after 30 min of exercise and at 15 min post-exercise by 18.8% and 14%, respectively. No significant changes were observed in the levels of TC or LDL-C over time. These results indicate that 30 min of moderate exercise elicits significant changes in HDL-C concentration during and up to 15 min after the exercise in untrained middle-aged men with low mean resting levels of HDL-C (0.85 mmol · 1^–1).     

Interference of strength development by simultaneously training for strength and endurance

Summary The purpose of this study was to determine how individuals adapt to a combination of strength and endurance training as compared to the adaptations produced by either strength or endurance training separately. There were three exercise groups: a strength group (S) that exercised 30–40 min·day^–1, 5 days·week^–1, an endurance group (E) that exercised 40 min·day^–1, 6 days·week^–1; and an S and E group that performed the same daily exercise regimens as the S and E groups. After 10 weeks of training, VO_{2 max} increased approx. 25% when measured during bicycle exercise and 20% when measured during treadmill exercise in both E, and S and E groups. No increase in VO_{2 max} was observed in the S group. There was a consistent rate of development of leg-strength by the S group throughout the training, whereas the E group did not show any appreciable gains in strength. The rate of strength improvement by the S and E group was similar to the S group for the first 7 weeks of training, but subsequently leveled off and declined during the 9th and 10th weeks. These findings demonstrate that simultaneously training for S and E will result in a reduced capacity to develop strength, but will not affect the magnitude of increase in VO_{2 max}.This research was supported by a University of Illinois at Chicago Circle Research Board Grant and by a NIH Biomedical Research Support Grant (HEW RR07158-2) to the University of Illinois at Chicago Circle     

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.     

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.     

Supramaximal test results of male and female speed skaters with particular reference to methodological problems

Summary Six male and six female elite speed skaters were tested during two bicycle ergometer tests: a 30 s sprint test and a 2.5 min supra maximal test. During the 2.5 min test oxygen consumption was measured every 30 s. The males showed 30–31% higher mean power output values both during the sprint test (1103 versus 769 Watt) and during the 2.5 min test (570 versus 390 Watt). Maximal oxygen consumption was 31% higher for the males than for the females (5.10 versus 3.50 l · min^–1). However, when expressed per kilogram lean body weight (LBM), power output and oxygen consumption was equal for both sexes. Differences between present and previous results are most likely due to methodological problems with the estimation of load during the supra maximal test. Subjects appear to experience difficulties in distributing their power output over the 2.5 min if they are tested for the first time. For experienced skaters and cyclists, fixed levels of 19 W · kgLBM^–1 as initial load setting for the sprint test and 8 W · kg LBM^–1 for the 2.5 min test are recommended.     

Cortisol,testosterone, and insulin action during intense swimming training in humans

An increase in the amounts of circulating plasma cortisol or a decrease in testosterone can result in whole-body insulin resistance. The purpose of this study was to determine if the increase in cortisol and/or decrease in testosterone concentrations commonly evident with intense endurance training is associated with insulin resistance. Male (n = 9) and female (n = 10) swimmers were examined during the off-season, after 9 weeks (9 WKS) of training averaging 5,500 m·day^–1 and after an additional 9 weeks (18 WKS) of training averaging 8,300 m·day^–1. Resting plasma cortisol concentration was (P <– 0.05) higher in the women compared to the men at 9 WKS; values were not significantly different between genders at 18 WKS. Plasma testosterone concentration decreased significantly (P <– 0.05) in the men at 9 and 18 WKS, but did not change in the women. Whole-body insulin action, as determined by insulin and glucose responses during a 120 min, 75-g oral glucose tolerance test, did not change with training in either the men or women. These data indicated that plasma testosterone concentration can decrease in male swimmers during intense endurance training; this alteration does not affect whole-body insulin action. There would also appear to be a gender-specific response of plasma cortisol to endurance training, which does not influence insulin action.     

Atrial natriuretic peptide response to endurance physical training in the rat

Summary The effect of an endurance physical training programme on the plasma and atrial natriuretic peptides (ANP) and on renal glomerular ANP receptors was evaluated in male normotensive Wistar rats. Maximal O₂ uptake was significantly greater in the endurance trained (117.1 Ml O₂ · kg^–1 · min^–1, SEM 6.18 versus the control rats 84.2 ml O₂ · kg^–1 · min^–1, SEM 4.88, P<0.01. In addition, various muscle oxidative enzymes were also significantly higher in endurance trained animals. An increase in resting plasma [ANP] was observed after 11 weeks of physical training (40.02 pg · ml^–1, SEM 7.07 vs 22.8 pg.ml^–1, SEM 3.83, P<0.05). Glomerular ANP receptor density was lower in trained rats (272 fmol · mg^–1 protein, SEM 3.1 vs 380 fmol · mg^–1 protein, SEM 6.1, P < 0.05), whereas atrial tissue [ANP] was not significantly different between controls and trained animals. However, in trained rats, circulating [ANP] was closely correlated with left atrial [ANP] (r = –0.92, P<0.05). Resting systolic blood pressure had not changed at the end of this physical training programme. It is considered that under physiological conditions ANP may be involved in long-term extracellular fluid volume homeostasis through the regulation of renal glomerular ANP receptors, and that the left atrium might play a significant role in this long term fluid volume control.     

Comparative effects of hindlimb suspension and exercise on skeletal muscle myosin isozymes in rats

Summary The purpose of this study was to ascertain the time course of changes, whilst suspending the hindlimb and physical exercise training, of myosin light chain (LC) isoform expression in rat soleus and vastus lateralis muscles. Two groups of six rats were suspended by their tails for 1 or 2 weeks, two other groups of ten rats each were subjected to exercise training on a treadmill for 9 weeks, one to an endurance training programme (1-h running at 20 m · min^–1 5 days · week^–1), and the other to a sprint programme (30-s bouts of running at 60 m · min^–1 with rest periods of 5 min). At the end of these experimental procedures, soleus and vastus lateralis superficialis muscles were removed for myosin LC isoform determination by two-dimensional gel electrophoresis. Hindlimb suspension for 2 weeks significantly increased the proportion of fast myosin LC and decreased slow myosin LC expression in the soleus muscle. The pattern of myosin LC was unchanged in the vastus lateralis muscle. Sprint training or endurance training for 9 weeks increased the percentage of slow myosin LC in vastus lateralis muscle, whereas soleus muscle myosin LC was not modified. These data indicate that hindlimb suspension influences myosin LC expression in postural muscle, whereas physical training acts essentially on phasic muscle. There were no differences in myosin LC observed under the influence of sprint- or endurance-training programme.     

Effect of endurance training on excessive CO2 expiration due to lactate production in exercise

Summary We attempted to determine the change in total excess volume of CO₂ Output (CO₂ excess) due to bicarbonate buffering of lactic acid produced in exercise due to endurance training for approximately 2 months and to assess the relationship between the changes of CO₂ excess and distance-running performance. Six male endurance runners, aged 19–22 years, were subjects. Maximal oxygen uptake (VO_2max), oxygen uptake (VO₂) at anaerobic threshold (AT), CO₂ excess and blood lactate concentration were measured during incremental exercise on a cycle ergometer and 12-min exhausting running performance (12-min ERP) was also measured on the track before and after endurance training. The absolute magnitudes in the improvement due to training for C02 excess per unit of body mass per unit of blood lactate accumulation (Ala^–) in exercise (CO₂ excess·mass^–1·la^–), 12-min ERP, VO₂ at AT (AT-VO₂) and VO_2max on average were 0.8 ml·kg^–1·l^–1·mmol^–1, 97.8m, 4.4 ml·kg^–1· min^–1 and 7.3 ml·kg^–1·min^–1, respectively. The percentage change in CO₂ excess·mass^–1·la^– (15.7%) was almost same as those of VO_2max (13.7%) and AT-VO₂ (13.2%). It was found to be a high correlation between the absolute amount of change in CO₂ excess·mass^–1·la^– and the absolute amount of change in AT-VO₂ (r=0.94, P<0.01). Furthermore, the absolute amount of change in C02 excess·mass^–1·la^–, as well as that in AT-VO₂ (r=0.92, P<0.01), was significantly related to the absolute amount of change in 12-min ERP (r=0.81, P<0.05). It was concluded that a large CO₂ excess·mass^–1·la^–1 of endurance runners could be an important factor for success in performance related to comparatively intense endurance exercise such as 3000–4000 m races.     

Erythrocyte count and hemoglobin levels in diabetic women

Summary Fasting blood glucose, erythrocyte counts hemoglobin levels of 131 Libyan diabetic women of Tripoli, Libya were determined. The respective mean values were 223±7 mg·dl^–1, 4.97±0.034× 10⁶·mm^–3 and 14.4±0.127 g·dl^–1. Sixty-five percent of these diabetic women were obese. The highest percent of diabetics belong to the age group 46–55 years. The increase in prevalence of diabetes correlates with an increase in obesity.A significant positive correlation was found between body surface area and fasting blood glucose levels (r=0.65;P<0.001). Elevated levels of erythrocyte count and hemoglobin were present in these diabetic patients. Significant correlations were found between body surface area and erythrocyte count, as well as between fasting blood glucose levels and erythrocyte count, indicating the effect of obesity and diabetes on erythrocyte numbers.A significant correlation was found between fasting blood glucose levels and hemoglobin (r=0.35;P<0.001). The elevated levels of hemoglobin present in these patients may be the result of haemoconcentration due to polyuria, which is always present in poorly controlled diabetic patients.The results suggest a close relationship between diabetes and obesity. Regulation of body weight/surface area is an important factor in the control of diabetes. The elevated levels of erythrocyte count and hemoglobin reflect poor control of blood glucose levels in these diabetic patients.     

The respiratory system as an exercise limiting factor in normal sedentary subjects

Summary The present study was undertaken to investigate the respiratory system as an exercise limiting factor. Breathing and cycle endurance (i.e. the time until exhaustion at a given performance level) as well as physical working capacity 170 (i.e. the exercise intensity corresponding to a heart rate of 170 beats -min^–1 on a cycle ergometer) were determined in four healthy sedentary subjects. Subsequently, the subjects trained their respiratory system for 4 weeks by breathing daily about 901 · min^–1 for 30 min. Otherwise they continued their sedentary lifestyle. Immediately after the respiratory training and 18 months later, all performance tests carried out at the beginning of the study were repeated. The respiratory training increased breathing endurance from 4.2 (SD 1.9) min to 15.3 (SD 3.8) min. Cycle endurance was improved from 26.8 (SD 5.9) min to 40.2 (SD 9.2) min whereas physical working capacity 170 remained essentially the same. During the endurance cycling test in the respiratory untrained state, the subjects continuously increased their ventilation up to hyperventilation [ventilation at exhaustion = 96.9 (SD 23.6) 1 · min^–1] while after the respiratory training they reached a respiratory steady-state without hyperventilation [ventilation at exhaustion = 63.3 (SD 14.5) 1 · min^–1]. The absence of this marked hyperventilation was the cause of the impressive increase of cycle endurance in normal sedentary subjects after respiratory training. The effects gained by the respiratory training were completely lost after 18 months. Our results indicated that the respiratory system was an exercise limiting factor during an endurance test in normal sedentary subjects.     

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.     

The influence of weekly training distance on fractional utilization of maximum aerobic capacity in marathon and ultramarathon runners

Summary This study was designed to examine the interrelationships between performance in endurance running events from 10 to 90 km, training volume 3–5 weeks prior to competition, and the fractional utilization of maximal aerobic capacity (% ) during each of the events. Thirty male subjects underwent horizontal treadmill testing to determine their , and steady-state at specific speeds to allow for calculation of % sustained during competition. Runners were divided into groups of ten according to their weekly training distance (group A trained less than 60 km · week^–1, group B 60 to 100 km · week^–1, and group C more than 100 km · week^–1). Runners training more than 100 km · week^–1 had significantly faster running times (average 19.2%) in all events than did those training less than 100 km · week^–1. or % sustained during competition was not different between groups. The faster running speed of the more trained runners, running at the same % during competition, was due to their superior running economy (19.9%). Thus all of the group differences in running performance could be explained on the basis of their differences in running economy. These findings suggest either that the main effect of training more than 100 km · week^–1 may be to increase running economy, or that runners who train more than 100 km · week^–1 may have inherited superior running economy. The finding that the maximal horizontal running speed reached during the progressive maximal treadmill test was a better predictor (r=0.72) of running performance at all distances than was the (r=0.54) suggests that peak treadmill running speed can predict performance in endurance running events.