Effects of endurance training and heat acclimation on psychological strain in exercising men wearing protective clothing

Two experiments examined the influences of endurance training and heat acclimation on ratings of perceived exertion (RPE) and thermal discomfort (RTD) during exercise in the heat while wearing two types of clothing. In experiment 1, young men underwent 8 weeks of physical training [60-80% of maximal aerobic power (VO2max) for 30-45 min day-1, 3-4 days week-1 at 20-22 degrees C dry bulb (db) temperature] followed by 6 days of heat acclimation [45-55% VO2max for 60 min day-1 at 40 degrees C db, 30% relative humidity (rh)] (n = 7) or corresponding periods of control observation followed by heat acclimation (n = 9). In experiment 2, young men were heat-acclimated for 6 or 12 days (n = 8 each). Before and after each treatment, subjects completed bouts of treadmill exercise (1.34 m s-1, 2% grade in experiment 1 and 0% grade in experiment 2) in a climatic chamber (40 degrees C db, 30% rh), wearing in turn normal light clothing (continuous exercise at 37-45% VO2max for a tolerated exposure of 116-120 min in experiment 1 and at 31-34% VO2max for 146-150 min in experiment 2) or clothing protective against nuclear, biological, and chemical agents (continuous exercise at 42-51% VO2max for a tolerated exposure of 47-52 min in experiment 1 and intermittent exercise at 23% VO2max for 97-120 min in experiment 2). In experiment 1, when wearing normal clothing, endurance training and/or heat acclimation significantly decreased RPE and/or RTD at a fixed power output. There were concomitant reductions in relative work intensity (% VO2max) [an unchanged oxygen consumption (VO2) but an increased VO2max, or a reduced VO2 with no change of VO2max], rectal temperature (Tre), mean skin temperature (Tsk), and/or heart rate (HR). When wearing protective clothing, in contrast, there were no significant changes in RPE or RTD. Although training and/or acclimation reduced %VO2max or Tre, any added sweat that was secreted did not evaporate through the protective clothing, thus increasing discomfort after training or acclimation. Tolerance times were unchanged in either normal or protective clothing. In experiment 2, when wearing normal clothing, heat acclimation significantly decreased RPE and RTD at a fixed power output, with concomitant reductions in Tre, Tsk, and HR; the response was greater after 12 than after 6 days of acclimation, significantly so for RPE and HR. When wearing protective clothing, the subjects exercised at a lower intensity for a longer duration than in the moderate exercise trial. Given this tactic, either 6 or 12 days of heat acclimation induces significant reductions RPE and/or RTD, accompanied by reductions in Tre, Tsk, and/or HR. Tolerance times in protective clothing were also increased by 11-15% after acclimation, despite some increase of sweat accumulation in the protective clothing. The results suggest that (1) neither endurance training nor heat acclimation reduce psychological strain when protective clothing is worn during vigorous exercise, because increased sweat accumulation adds to discomfort, and (2) in contrast to the experience during more vigorous exercise, heat acclimation is beneficial to the subject wearing protective clothing if the intensity of effort is kept to a level that allows permeation of sweat through the clothing. This condition is likely to be met in most modern industrial applications.     

Effects of aerobic exercise training and yoga on the baroreflex in healthy elderly persons

It is unclear whether the age-associated reduction in baroreflex sensitivity is modifiable by exercise training. The effects of aerobic exercise training and yoga, a non-aerobic control intervention, on the baroreflex of elderly persons was determined. Baroreflex sensitivity was quantified by the alpha-index, at high frequency (HF; 0.15-0.35 Hz, reflecting parasympathetic activity) and mid-frequency (MF; 0.05-0.15 Hz, reflecting sympathetic activity as well), derived from spectral and cross-spectral analysis of spontaneous fluctuations in heart rate and blood pressure. Twenty-six (10 women) sedentary, healthy, normotensive elderly (mean 68 years, range 62-81 years) subjects were studied. Fourteen (4 women) of the sedentary elderly subjects completed 6 weeks of aerobic training, while the other 12 (6 women) subjects completed 6 weeks of yoga. Heart rate decreased following yoga (69 +/- 8 vs. 61 +/- 7 min-1, P < 0.05) but not aerobic training (66 +/- 8 vs. 63 +/- 9 min-1, P = 0.29). VO2 max increased by 11% following yoga (P < 0.01) and by 24% following aerobic training (P < 0.01). No significant change in alpha MF (6.5 +/- 3.5 vs. 6.2 +/- 3.0 ms mmHg-1, P = 0.69) or alpha HF (8.5 +/- 4.7 vs. 8.9 +/- 3.5 ms mmHg-1, P = 0.65) occurred after aerobic training. Following yoga, alpha HF (8.0 +/- 3.6 vs. 11.5 +/- 5.2 ms mmHg-1, P < 0.01) but not alpha MF (6.5 +/- 3.0 vs. 7.6 +/- 2.8 ms mmHg-1, P = 0.29) increased. Short-duration aerobic training does not modify the alpha-index at alpha MF or alpha HF in healthy normotensive elderly subjects. alpha HF but not alpha MF increased following yoga, suggesting that these parameters are measuring distinct aspects of the baroreflex that are separately modifiable.     

Effects of a muscle exercise program on exercise capacity in subjects with osteoarthritis

Maximal aerobic power and muscle function have been shown to decrease with age and to be even lower in patients with osteoarthritis (OA). This study was designed to determine if subjects with OA who underwent only a muscle exercise program had improved exercise capacity and cardiovascular fitness. A maximal graded exercise test was given before and after 3 months of exercise (isometric, isotonic, and isometric force generated as a function of time contractions, three times a week). Maximal strength and the tension-time index improved significantly. Peak aerobic power increased from 15.99 +/- 3.96 mL.kg-1.min-1 to 20.34 +/- 3.29 mL.kg-1.min-1. On average, maximal walking speed increased from 2.0 +/- 0.6 mph to 2.4 +/- 0.7mph. Exercise time increased 22%, from 9.2 +/- 2.3 minutes to 11.2 +/- 2.7 minutes. There were significant reductions in submaximal heart rate (15b.min-1) and systolic blood pressure (15mmHg) after training. It would appear that the reduction in aerobic fitness of subjects with OA is secondary to their reduced muscle function. By improving muscle function, increases in exercise capacity and aerobic fitness occurred.     

Techniques of MRI cholangiopancreatography. History, current status and future prospects

This study investigates the effects of long-term passive heat exposure and a 16-week basic military training program on heat acclimatization. Thirty recruits were tested on the zero (T1), 2nd (T2), 6th (T3), and 16th (T4) weeks of the basic military training program. The trials involved 1 hour of marching on a treadmill at 5.5 km h-1, with a 5% gradient. The subjects wore their camouflage uniforms during the trials, with simulated combat loads. The trials were conducted in a climatic chamber programmed at 32 degrees C, 60% relative humidity, 900 Wm-2 of simulated solar radiation, and wind speed of 3 m s-1. There was no fluid replacement during the trials. Because only 9 subjects attended all the trials, the results presented are based on these subjects. No significant difference was found in mean skin temperature in all the four trials. Tympanic temperature was significantly reduced (p < 0.05) only at 20 minutes. Pairwise analysis was significant (p < 0.05) only between T1 (37.18 +/- 0.38 degrees C) and T4 (36.48 +/- 0.53 degrees C). Average body temperature was significantly different only at 10 and 60 minutes (p < 0.05). A significant pairwise difference (p < 0.05) was found only between T1 (36.61 +/- 0.33 degrees C) and T4 (36.07 +/- 0.46 degrees C) in 10 minutes. No pairwise difference was found at 60 minutes. Mean heart rate (HR) was significantly reduced during the 16 weeks at 10, 20, and 30 minutes. Mean HR at 10 minutes was reduced from 152.11 +/- 14.18 beats min-1 in T1 to 130.78 +/- 10.43 beats min-1 in T4 (p < 0.001). Mean HR at 20 and 30 minutes was reduced from 156.11 +/- 17.74 beats min-1 (T1) to 137.25 +/- 11.42 beats min-1 (T4) (p < 0.001), and from 157.14 +/- 15.77 beats min-1 (T1) to 146.11 +/- 12.64 beats min-1 (T4) (p < 0.05). There was no significant difference in sweat loss and mean sweat rate during the 16 weeks. This study concluded that long-term passive heat exposure was effective at inducing heat acclimatization in terms of tympanic temperature, average body temperature, mean skin temperature, sweat loss, and mean sweat rate, but not in terms of HR. Physical training was still necessary to induce further adaptation in HR. The limiting factor to task completion during the trials was physical fitness rather than beat fitness.     

Effect of hypohydration on gastric emptying and intestinal absorption during exercise

Dehydration and hyperthermia may impair gastric emptying (GE) during exercise; the effect of these alterations on intestinal water flux (WF) is unknown. Thus the purpose of this study was to determine the effect of hypohydration ( approximately 2.7% body weight) on GE and WF of a water placebo (WP) during cycling exercise (85 min, 65% maximal oxygen uptake) in a cool environment (22 degrees C) and to also compare GE and WF of three carbohydrate-electrolyte solutions (CES) while the subjects were hypohydrated. GE and WF were determined simultaneously by a nasogastric tube placed in the gastric antrum and via a multilumen tube that spanned the duodenum and the first 25 cm of jejunum. Hypohydration was attained 12-16 h before experiments by low-intensity exercise in a hot (45 degrees C), humid (relative humidity 50%) environment. Seven healthy subjects (age 26.7 +/- 1.7 yr, maximal oxygen uptake 55.9 +/- 8.2 ml . kg-1 . min-1) ingested either WP or a 6% (330 mosmol), 8% (400 mosmol), or a 9% (590 mosmol) CES the morning following hypohydration. For comparison, subjects ingested WP after a euhydration protocol. Solutions ( approximately 2.0 liters total) were ingested as a large bolus (4.6 ml/kg body wt) 5 min before exercise and as small serial feedings (2.3 ml/kg body wt) every 10 min of exercise. Average GE rates were not different among conditions (P > 0.05). Mean (+/-SE) values for WF were also similar (P > 0.05) for the euhydration (15.3 +/- 1.7 ml . cm-1 . h-1) and hypohydration (18.3 +/- 2.6 ml . cm-1 . h-1) experiments. During exercise after hypohydration, water absorption was greater (P < 0.05) with ingestion of WP (18.3 +/- 2. 6) and the 6% CES (16.5 +/- 3.7), compared with the 8% CES (6.9 +/- 1.5) and the 9% CES (1.8 +/- 1.7). Mean values for final core temperature (38.6 +/- 0.1 degrees C), heart rate (152 +/- 1 beats/min), and change in plasma volume (-5.7 +/- 0.7%) were similar among experimental trials. We conclude that 1) hypohydration to approximately 3% body weight does not impair GE or fluid absorption during moderate exercise when ingesting WP, and 2) hyperosmolality (>400 mosmol) reduced WF in the proximal intestine.     

Free fatty acid metabolism in aerobically fit individuals

The impact of aerobic fitness level on the production and disposal of serum free fatty acids was investigated in 26 normal young volunteers. The fitness level was ascertained by history and confirmed by determination of maximal aerobic capacity. Energy expenditure and substrate oxidation at rest were measured with indirect calorimetry. Free fatty acid turnover was measured with an infusion of [14C]palmitic acid. All tests were done > or = 48 h after the last bout of exercise. The sedentary (SED) volunteers had higher rates of systemic delivery of fatty acids than aerobically fit (FIT) individuals (532 +/- 53.4 vs. 353 +/- 62.3 mumol/min; P = 0.05). This difference was accentuated when the values were normalized to fat-free mass (9.2 +/- 0.8 and 5.9 +/- 0.98 mumol.kg-1.min-1 for SED and FIT, respectively). Fatty acid oxidation was similar between FIT and SED volunteers in absolute numbers (209 +/- 25 vs. 202 +/- 21 mumol/min, respectively; NS) as well as when normalized to fat-free mass (3.8 +/- 0.9 vs. 3.6 +/- 1.4 mumol.kg-1.min-1, respectively; NS). In contrast, the nonoxidative disposal of serum fatty acids was higher in SED (330 +/- 46.1 mumol/min) than in FIT individuals (144 +/- 52 mumol/min; P = 0.026). Thus, the ratio of nonoxidative to oxidative disposal rates of fatty acids was higher in SED than in FIT individuals (1.65 +/- 0.29 vs. 0.75 +/- 0.17; P = 0.021). The data support the hypothesis that high aerobic fitness level is associated with a low rate of systemic delivery of fatty acids at rest. Nevertheless, subjects with high aerobic fitness levels have fat oxidation at the same rate as unfit individuals.     

Skeletal muscle lactate accumulation and creatine phosphate depletion during heavy exercise in congestive heart failure. Cause of limited exercise capacity?

OBJECTIVE: To study the mechanisms of limited exercise capacity and skeletal muscle energy production in male patients with congestive heart failure. DESIGN: Muscle biopsy study. PATIENTS: Skeletal muscle metabolic response to maximal bicycle exercise was studied in 10 patients with chronic congestive heart failure (ejection fraction 0.22 +/- 0.05; peak oxygen consumption, VO2 15.1 +/- 4.9 ml.min-1.kg-1) and in nine healthy subjects (peak VO2 33.5 +/- 6.7 ml.min-1.kg-1). Activities of skeletal muscle enzymes were measured from the vastus lateralis muscle of 48 patients (ejection fraction 0.24 +/- 0.06, peak VO2 17.4 +/- 5.4 ml.min-1.kg-1) and 36 healthy subjects (peak VO2 38.3 +/- 8.4 ml.min-1.kg-1). RESULTS: Although blood lactate levels were lower in patients than in healthy subjects (2.2 +/- 0.3 vs 5.2 +/- 0.6 mmol.l-1; P < 0.001) at peak exercise (96 +/- 11 W for patients and 273 +/- 14 W for controls), skeletal muscle lactate was similarly elevated (25.6 +/- 3.2 vs 22.7 +/- 2.7 mmol.kg-1) and creatine phosphate was equally depressed (P < 0.02) to low levels (7.0 +/- 1.9 vs 6.7 +/- 0.9 mmol.kg-1). The muscle ATP decreased by 21% (P < 0.05) and 8% (P < 0.01) in the patients and controls, respectively. Activities of rate limiting enzymes of the citric acid cycle (alpha-ketoglutarate dehydrogenase) and oxidation of free fatty acids (carnitine palmitoyltransferase II) were 48% and 21% lower than in controls, but the mean phosphofructokinase activity was unchanged in congestive heart failure. CONCLUSIONS: It seems that the main limiting factor of exercise performance during heavy exercise is the same in congestive heart failure and healthy subjects, a high rate of skeletal muscle lactate accumulation and high-energy phosphate depletion. In congestive heart failure, the low activity of aerobic enzymes is likely to impair energy production and lead to lactate acidosis at low workloads.     

Olympics in Atlanta: a fight against physics

Environmental stress can become so severe that athletes, in spite of proper training, heat acclimation, and hydration level, are unable to maintain thermal balance. Such incompensable conditions occur when air temperature exceeds 35 degrees C and relative humidity becomes higher than 60%. At these high environmental temperatures, the heat liberated during exercise can only be lost by evaporation of sweat, and therefore water vapor pressure sets limits on the possible rate of evaporation. Calculations are presented for the required and the maximal possible sweat evaporation rate for high-intensity, long-duration events, using marathon racing as an example. The consequence of the environmental heat stress is that the athlete must reduce the speed of running considerably to prevent potential heat injury. In certain extreme environmental conditions, sporting events should be canceled or postponed.     

Metabolic profile of high intensity intermittent exercises

To evaluate the magnitude of the stress on the aerobic and the anaerobic energy release systems during high intensity bicycle training, two commonly used protocols (IE1 and IE2) were examined during bicycling. IE1 consisted of one set of 6-7 bouts of 20-s exercise at an intensity of approximately 170% of the subject's maximal oxygen uptake (VO2max) with a 10-s rest between each bout. IE2 involved one set of 4-5 bouts of 30-s exercise at an intensity of approximately 200% of the subject's VO2max and a 2-min rest between each bout. The accumulated oxygen deficit of IE1 (69 +/- 8 ml.kg-1, mean +/- SD) was significantly higher than that of IE2 (46 +/- 12 ml.kg-1, N = 9, p < 0.01). The accumulated oxygen deficit of IE1 was not significantly different from the maximal accumulated oxygen deficit (the anaerobic capacity) of the subjects (69 +/- 10 ml.kg-1), whereas the corresponding value for IE2 was less than the subjects' maximal accumulated oxygen deficit (P < 0.01). The peak oxygen uptake during the last 10 s of the IE1 (55 +/- 6 ml.kg-1.min-1) was not significantly less than the VO2max of the subjects (57 +/- 6 ml.kg-1.min-1). The peak oxygen uptake during the last 10 s of IE2 (47 +/- 8 ml.kg-1.min-1) was lower than the VO2max (P < 0.01). In conclusion, this study showed that intermittent exercise defined by the IE1 protocol may tax both the anaerobic and aerobic energy releasing systems almost maximally.     

Anaerobic and aerobic responses of males and females to rope skipping

Six male and six female subjects performed maximal bicycle ergometer work and skipped rope at selected rates. Measures included oxygen uptake (VO2), oxygen debt (VO2 debt), blood lactate, and heart rate (HR). Mean values for males for the maximum test and while skipping at 120, 140, and 160 turns . min-1 were, respectively: VO2-50.2, 38.3, 39.7, and 44.3 ml . kg-1 . min-1; HR-185, 166, 168, and 178 beats . min-1; VO2 debt--5.70, 3.65, 3.50, and 4.04 liter; and lactate--12.7, 7.4, 7.6, and 9.2 mM . 1(-1). For females: VO2--42.8, 39.8, 39.4, and 39.4 ml . kg-1 . min-1; HR--185, 181, 181, and 181 beats . min-1; VO2 debt--4.71, 4.27, 4.22, and 4.15 liter; and lactate--11.5, 11.5, 12.2, and 11.9 mM . l-1. No significant differences were found between treatments for females for any measure. Rope skipping placed high demands on both aerobic (females, 92% VO2max, males, 76-88%) and anaerobic capacities (females, 100-106% lactate values after maximum bicycle exercise; males, 58-72%). In males, who did not reach VO2max during rope skipping, it was verified that the VO2 requirement does not increase with skipping rate over a relatively wide range, but that extremely high rates do require more energy from both aerobic and anaerobic sources. Differences in tolerance of males and females to rope skipping were attributed to the lower aerobic power and higher body fat of females.     

Effects of local restriction of evaporation and moderate local ventilation on thermoregulatory responses in exercising humans

Ten healthy young men participated in two series of three trials: series 1 (C1) with, or without, local restriction of evaporation (either on the trunk or on the legs) and series 2 (C2) with, or without, local moderate nitrogen ventilation (40 l.min-1) under an impermeable garment (trunk or leg ventilation). After 60-min rest in a thermoneutral environment, the subjects exercised in a warm environment [30 degrees C, 47% relative humidity (rh) during C1 and 29% rh during C2] on a cycle ergometer for 60 min at 70 W during C1 or at 60 W during C2. During C1, local covering with plastic foil did not increase internal temperature, but increased the mean skin temperature with a higher effect in the case of leg restriction. The trunk skin temperature was affected by the leg covering while the leg skin temperature was not changed by the trunk covering. Only the local sweat rate of the trunk was increased by the two restriction conditions. During C2, internal temperature was decreased by local ventilation while mean skin temperature was reduced only by trunk ventilation. The local ventilation affected only trunk skin temperature with a greater decrease during trunk ventilation. Trunk ventilation did not influence the skin temperature of the legs while ventilation of the legs decreased trunk skin temperature. In addition, leg ventilation decreased the sweat rate of the legs. The impermeable suit worn during C2 led to a greater physiological strain compared to the plastic film worn during C1 even with local ventilation under the impermeable garment. As expected, limiting sweat evaporation led to an increase in physiological strain. Microclimate ventilation at a rate of 40 l.min-1 was not sufficient to allow total heat dissipation but allowed 60-min exercise in a warm environment to be completed without excessive heat accumulation. It would appear that ventilation of the trunk locally was the best solution because of the smaller increase in skin temperature and higher sweating capacity of the trunk.     

Differential expression of CD14, CD36 and the LDL receptor on human monocyte-derived macrophages. A novel cell culture system to study macrophage differentiation and heterogeneity

Multiple heterogeneous groups of subjects (both sexes and a wide range of maximal oxygen uptake VO2max, body mass, body surface area (AD),% body fat, and AD/mass coefficient) exercised on a cycle ergometer at a relative (%VO2max, REL) or an absolute (60 W) exercise intensity in a cool (CO 21 degrees C, 50% relative humidity), warm humid (WH 35 degrees C, 80%) and a hot dry (HD 45 degrees C, 20%) environment. Rectal temperature (Tre) responses were analysed for the influence of the individual's characteristics, environment and exercise intensity. Exposures consisted of 30-min rest, followed by 60-min exercise. The Tre was negatively correlated with mass in all conditions. Body mass acted as a passive heat sink in all the conditions tested. While negatively correlated with VO2max and VO2max per kilogram body mass in most climates, Tre was positively correlated with VO2max and VO2max per kilogram body mass in the WH/REL condition. Thus, when evaporative heat loss was limited as in WH, the higher heat production of the fitter subjects in the REL trials determined Tre and not the greater efficiency for heat loss associated with high VO2max. Body fatness significantly affected Tre only in the CO condition, where, with low skin blood flows (measured as increases in forearm blood flow), the insulative effect of fat was pronounced. In the warmer environments, high skin blood flows offset the resistance offered by peripheral adipose tissue. Contrary to other studies, Tre was positively correlated with AD/mass coefficient for all conditions tested. For both exercise types used, being big (a high heat loss area and heat capacity) was apparently more beneficial from a heat strain standpoint than having a favourable AD/mass coefficient (high in small subjects). The total amount of variance in Tre responses which could be attributed to individual characteristics was dependent on the climate and the type of exercise. Though substantial for absolute exercise intensities (52%-58%) the variance explained in Tre differed markedly for relative intensities: 72% for the WH climate with its limited evaporative capacity, and only 10%-26% for the HD and CO climates. The results showed that individual characteristics play a significant role in determining the responses of body core temperature in all conditions tested, but their contribution was low for relative exercise intensities when evaporative heat loss was not restricted. This study demonstrated that effects of individual characteristics on human responses to heat stress cannot be interpreted without taking into consideration both the heat transfer properties of the environment and the metabolic heat production resulting from the exercise type and intensity chosen. Their impact varies substantially among conditions.     

Analysis of swainsonine and its early metabolic precursors in cultures of Metarhizium anisopliae

We examined the separate and combined effects of hypohydration level and exercise intensity on aldosterone (ALD) and arginine vasopressin (AVP) responses during exercise-heat stress. Nine heat acclimated men performed 50 min of treadmill exercise in a warm room (30 degrees C dry bulb (DB), 50% relative humidity (RH) at 25%, 45% and 65% VO2max when euhydrated and when hypohydrated by 3% and 5% of body weight. Blood samples were drawn at rest and at 20 min of exercise. ALD and AVP increased (P < 0.05) in a graded manner with hypohydration level, and this effect persisted during exercise-heat stress. High intensity exercise produced greater ALD and AVP increases than low intensity exercise. ALD responses during exercise were independent of hypohydration level. AVP responses were closely related to osmolality (N = 6 of 7 subjects; r = 0.51 to r = 0.98; average r = 0.84) despite varying hydration, exercise intensity, or core temperature. We conclude that: 1) ALD and AVP increase in a graded manner with hypohydration, and this effect persists during exercise-heat stress; 2) ALD and AVP increases elicited by exercise are greater during high intensity than low intensity exercise; 3) Hypohydration and exercise intensity have additive effects on ALD: and 4) AVP responses are closely coupled to osmolality.     

Ways of knowing

BACKGROUND: Although it has become clear that habitual exercise in older individuals can partially offset age-associated cardiovascular declines, it is not known whether the beneficial effects of exercise training in older individuals depend on their prior fitness level. METHODS AND RESULTS: Ten sedentary men (S), age 60.0 +/- 1.6 years (mean +/- SEM), who were carefully screened to exclude cardiac disease underwent exercise training for 24 to 32 weeks, and eight age-matched endurance-trained men (ET) stopped their exercise training for 12 weeks. All underwent treadmill exercise and rest and maximal cycle exercise upright gated blood pool scans at baseline and after the lifestyle intervention. Before the intervention, the treadmill maximum rate of oxygen consumption (Vo2max) was 49.9 +/- 1.9 and 32.1 +/- 1.4 mL.kg-1.min-1 in ET and S, respectively. During upright cycle exercise at exhaustion, although heart rate did not differ between groups, cardiac index, stroke volume index, ejection fraction, and left ventricular contractility index (systolic blood pressure/end-systolic volume index) all were significantly higher, and end-systolic volume index, diastolic blood pressure, and total systemic vascular resistance all were significantly lower in ET versus S. After the partial deconditioning of ET men, Vo2max fell to 42 +/- 2.2 mL.kg-1.min-1, and training of S increased Vo2max to 36.2 +/- 1.6 mL.kg-1.min-1. Training of S had effects on cardiovascular function that were similar in magnitude but directionally opposite those of detraining ET. All initial differences in cardiovascular performance at peak work rate between S and ET were abolished with the intervention. Across the broad range of fitness levels encountered before and after change in training status (Vo2max of 26 to 58 mL.kg-1.min-1), cardiac index, stroke volume index, end-systolic volume index, ejection fraction, and the left ventricular contractility index were all linearly correlated with Vo2max. CONCLUSIONS: Exercise training or detraining of older men results in changes in left ventricular performance that are qualitatively and quantitatively similar, regardless of the initial level of fitness before the intervention.     

Human acclimation to work in warm and humid environments

The aim of this study was to analyse the acclimation of male Europeans during a forty-one day stay in the hot and humid climate of Thailand. We also tried to examine the phases of acclimation which would eventually be used by trainers in the elaboration of the schedule of athletes' preparation to participate in competitions in a tropical climate. Twelve Polish male subjects ageing 21-38 years participated in these examinations. In Poland and Thailand the cycloergometric exercise test with the load of 53% of VO2max was performed until a 1.2 degrees C (delta Tre) increase in rectal temperature was reached. The exercise test was executed in the same environmental conditions (i.e. 30 +/- 1 degrees C and 70 +/- 3% of relative humidity). The duration of this exercise test (DE) was used as a criterion for the efficiency of thermoregulatory functions. During acclimation, three peaks of greater exercise thermoregulatory efficiency have been found, i.e. on the 4th-5th, 11th-12th and 29th-30th days of stay. These findings are particularly important for professional athletes who wish to prepare themselves for competitions held in hot and humid climates.     

Smaller lungs in women affect exercise hyperpnea

We subjected 29 healthy young women (age: 27 +/- 1 yr) with a wide range of fitness levels [maximal oxygen uptake (VO2 max): 57 +/- 6 ml . kg-1 . min-1; 35-70 ml . kg-1 . min-1] to a progressive treadmill running test. Our subjects had significantly smaller lung volumes and lower maximal expiratory flow rates, irrespective of fitness level, compared with predicted values for age- and height-matched men. The higher maximal workload in highly fit (VO2 max > 57 ml . kg-1 . min-1, n = 14) vs. less-fit (VO2 max < 56 ml . kg-1 . min-1, n = 15) women caused a higher maximal ventilation (VE) with increased tidal volume (VT) and breathing frequency (fb) at comparable maximal VT/vital capacity (VC). More expiratory flow limitation (EFL; 22 +/- 4% of VT) was also observed during heavy exercise in highly fit vs. less-fit women, causing higher end-expiratory and end-inspiratory lung volumes and greater usage of their maximum available ventilatory reserves. HeO2 (79% He-21% O2) vs. room air exercise trials were compared (with screens added to equalize external apparatus resistance). HeO2 increased maximal expiratory flow rates (20-38%) throughout the range of VC, which significantly reduced EFL during heavy exercise. When EFL was reduced with HeO2, VT, fb, and VE (+16 +/- 2 l/min) were significantly increased during maximal exercise. However, in the absence of EFL (during room air exercise), HeO2 had no effect on VE. We conclude that smaller lung volumes and maximal flow rates for women in general, and especially highly fit women, caused increased prevalence of EFL during heavy exercise, a relative hyperinflation, an increased reliance on fb, and a greater encroachment on the ventilatory "reserve." Consequently, VT and VE are mechanically constrained during maximal exercise in many fit women because the demand for high expiratory flow rates encroaches on the airways' maximum flow-volume envelope.     

The effect of antiemetics and reduced radiation fields on acute gastrointestinal morbidity of adjuvant radiotherapy in stage I seminoma of the testis: a randomized pilot study

OBJECTIVE: To assess the long term effects of weight loss with and without additional aerobic and weight training exercises on exercise tolerance and cardiorespiratory fitness in obese women. EXPERIMENTAL DESIGN: Randomized prospective study for an approximately one-year community setting. PATIENTS: 31 healthy obese women volunteers (age 42.8 yrs +/- 6 SD) recruited by community advertisement. INTERVENTION: All subjects underwent a weight loss program consisting of low calorie diet and behavior therapy for a minimum of 46 weeks. They were randomly assigned to one of the four groups. Group A: diet alone, Group B: diet plus aerobic exercise program in a supervised group setting, Group C: Diet plus weight training and Group D: diet plus weight training plus aerobic exercise program. MEASURES: Exercise time (Tex) peak sustained workload (Wp), peak oxygen consumption (VO2), oxygen pulse and the rate of change of VO2 on recovery (VO2rec) were measured at the beginning and after 47.5 weeks +/- 1.5 SD, of the program. RESULTS: All subjects lost weight and achieved increased Tex and lowered resting VO2. VO2 peak and VO2 peak kg-1 increase in Groups B and D only. O2 pulse and VO2rec improved in group D. Improvements in exercise time correlated significantly with initial exercise time and weight loss. CONCLUSIONS: Weight loss increase Tex irrespective of participation in an exercise program. However, evidence of improved aerobic fitness occurred only in groups performing aerobic exercise.     

Cardiorespiratory fitness evaluation by the shuttle test in asthmatic subjects during aerobic training

PURPOSE: The purpose of this study was to assess the validity of the 20-m shuttle test with 1-min stages (20-MST) to estimate maximal oxygen uptake (VO2 max) and its ability to register cardiorespiratory modifications over the course of an individualized aerobic training program for mild to moderately asthmatic children acclimatized to moderate altitude. METHODS: Forty-eight asthmatic subjects aged 12 to 17 years performed both a maximal incremental exercise test on a cycle ergometer and the 20-MST. Ten of the subjects were then randomly chosen and trained three times per week at their ventilatory threshold (Vth) intensity level for three months. Another group of ten asthmatic subjects served as control subjects. Training intensity was adjusted monthly; heart rate values at Vth were increased by the same proportion as the increase in Vo2 max as measured by the 20-MST. At the end of training, both groups were again evaluated with the two tests. The Vo2 max values by direct measurement and by the 20-MST were not significantly different for the entire population (46.5 +/- 1.6 vs 47.2 +/- 2.1 ml.min-1.kg-1). In addition, the two test results were in close agreement (r = 0.84; p < 0.01). After training, a sharp improvement in the direct Vo2 max (44.1 +/- 2.4 to 51.2 +/- 1.9 ml.min-1.kg-1) was noted in the training group as well as an increase in the Vth (25.6 +/- 1.9 to 32.1 +/- 3.4 ml.min-1.kg-1), the maximal power (152 +/- 7.1 to 185 +/- 3.8 W), and the maximal oxygen pulse (0.24 +/- 0.007 to 0.27 +/- 0.008 ml.beat-1.kg-1). CONCLUSION: The indirect measure confirmed these results: a simultaneous increase in VO2 max (43.7 +/- 2.5 to 53.8 +/- 2.1 ml.min-1.kg-1), maximal oxygen pulse (0.22 +/- 0.004 to 0.27 +/- 0.006 ml.beat-1.kg-1), and the number of stages completed (7 +/- 1.4 to 10.1 +/- 1.3) was observed. It was concluded that the 20-MST has sufficient validity to assess VO2 max and to register cardiorespiratory modifications over the course of individualized aerobic training programs in mild and moderately asthmatic children. It thus may be used to adjust training intensities during these programs.     

Temperature regulation during exercise in water and air

Four healthy subjects were studied during exercise in water, using a swimming flume, and in air, on a stationary bicycle ergometer at mean skin temperatures of 30 and 33 degrees C, respectively. Measurements included rectal (Tre), esophageal (Tes), and mean skin (Ts) temperatures, metabolic energy liberation (M) and total heat production (H), maximal aerobic power output (Vo2 max), cardiac frequency and calculated peripheral tissue heat conductance (K). The results showed that for a given M and Ts, Tes and Tre were about 0.4 degree C lower and the K values were consistently higher in swimming than in bicycling. The intersubject variability in Tes and Tre was reduced by considering relative (expressed as %VO2max) rather than absolute work load, but the differences in the body temperatures between the two types of exercise remained. It was concluded that during exercise in water where the capacity for heat dissipation is increased, the body core temperature (Tc) is maintained at a lower level due to the higher forced convective and conductive heat transfer from the skin in water. This reduces the heat storage at the beginning of exercise compared with conditions in air. The lower Tc-Ts gradient for a given H in swimming, which results in higher K values implies a greater skin circulation than during cycling in air.     

Atropine substitutes and the writhing syndrome in mice

Eight subjects underwent an exercise training program (10 days at 75% VO2max for 1 h/day at 25 degrees C db/13 degrees C wb) and a heat-acclimation program (10 days at 50% VO2max for 1 h/day at 35 degrees C db/32 degrees C wb). The relations of chest sweat rate and of forearm blood flow to internal temperature were determined for each subject at a 25 degrees C ambient temperature before training, between training and acclimation, and following acclimation. Training shifted the vasodilation and sweating thresholds toward lower internal temperatures, and acclimation further lowered these thresholds. All threshold shifts were statistically significant (P less than 0.05). Training and acclimation both appeared to increase the slope of the sweating relation, but these effects were not statistically significant. Changes in the slope of the blood flow relation were small and inconsistent. Since arm blood flow is higher at any given internal temperature after acclimation, the lower blood flow which is reported to accompany heat acclimation must result from the lower body temperatures.