Acute physiological responses to different circuit training protocols.

AIM: The purpose of present study was to compare the acute physiological responses to a circuit weight training with the responses to a combined circuit training (weight training and treadmill run). METHODS: The sample consisted of 25 individuals at an average state of training, 10 men and 15 female, between 18 and 35 year old. There were selected 60 second sets of resistance exercises to the circuit weight training (CWT). Whereas in the combined circuit training (CCT), the subjects spent 30 seconds on the same resistance exercises and 30 seconds running on the treadmill. The rest intervals between the sets lasted 15 seconds. The analysis of variance (ANOVA) with 5% significance level was utilized to the statistical analysis of the results. RESULTS: Comparing circuit training protocols, it was noted that CCT elicits a higher relative and absolute VO2 and energy expenditure values than CWT for both genders (P<0.05). Regarding inter-gender comparison, males showed higher absolute and relative VO2 and absolute energy expenditure values for both CWT and CCT than females (P<0.05). Females showed a significant greater %VO2max value for both CWT and CCT. Due to the experimental conditions used to state both circuit training bouts (CWT and CCT), the VO2 rate found was higher than the values reported by previous studies which used heavier weight lift. CONCLUSION: CCT seems adequate to produce cardiovascular improvements and greater energy expenditure for both men and women, while CWT group classes are sufficient only for unfit women.

Effects of long-term training on the progression of chronic renal failure in rats.

To evaluate the effects of long-term exercise on the progression of chronic renal failure (CRF), adult Munich-Wistar rats with 5/6 renal mass ablation were submitted to treadmill exercise for 30 min 5 times/wk for 60 d. Whole kidney function and glomerular hemodynamics, proteinuria, and glomerular sclerosis were evaluated in 4 groups: Control, Sham trained (Sham + Ex), rats submitted to 5/6 nephrectomy (CRF) and maintained sedentary, and rats with 5/6 nephrectomy and trained (CRF + Ex). The groups with chronic renal failure (sedentary and trained) presented a reduction in total glomerular filtration rate (GFR) and in renal plasma flow (RPF), accompanied by an increase in single nephron GFR (SNGFR) and glomerular plasma flow (QA). However, the CRF + EX group did not show the glomerular hypertension observed in the CRF group. Despite the normalization of glomerular hypertension, proteinuria and sclerosis index were not different from the CRF sedentary group. Physical training provoked a vasodilatation of efferent arterioles, which induced the normalization of glomerular hypertension. These results suggest that the reduction alone of glomerular hypertension induced by exercise does not prevent the progression of renal disease, indicating the participation of other associated factors in this experimental model.

Ventilatory responses during electrically induced muscular work in anesthetized dogs, after both deafferentation and cross circulation of hindlimbs.

1. The role of the neural afferent component from moving limbs during exercise hyperpnea has been studied in dogs. The influence of neural and humoral effects was evaluated by dorsal root section and limb cross-circulation. 2. Respiratory minute volume (Ve), frequency (f), tidal volume (VT) and oxygen consumption (VO2) were measured in anesthetized dogs submitted to light electrically-induced exercise (ventral root stimulation of L6 or L7), both before and after deafferentation. 3. In control experiments the increase of respiratory minute volume (Ve) was directly proportional to VO2, and primarily due to changes in frequency. After dorsal root section (L1 to S1), VO2 increased, but no significant changes were observed in the other respiratory parameters. 4. In contrast to the deafferentation experiments, no changes were detected either in Ve or in f during exercise in the cross-circulation experiments. 5. It is concluded that during light exercise reflexes generated by moving limbs are important for triggering the exercise tachypneic response.

Maximal oxygen uptake during exercise using trained or untrained muscles.

Maximal oxygen uptake, VO2 max, was determined for cyclists, long-distance runners and non-athletes during uphill running (treadmill) and cycling (cycloergometer) to compare trained and untrained muscles. Blood lactate, maximal heart rate and maximal ventilation during work were also measured. VO2 max was higher for runners and non-athletes during exercise on the treadmill and higher for cyclists during exercise on the cycloergometer. For runners and non-athletes, maximal heart rate accompanied the increase in VO2 max, whereas similar values were obtained for cyclists on both ergometers. Maximal ventilation during work accompanied the difference in VO2 max in both groups of athletes but among non-athletes it was similar during exercise on both the cycloergometer and the treadmill. Blood lactate was similar during exercise on both ergometers for all groups. These results suggest that the quantitative effects of training on cardiovascular and respiratory functions may only be properly evaluated by using an ergometer which requires an activity similar to that usually performed by the subjects. Cycle riding may possibly induce significant and specific alterations in the muscles involved in the exercise, thus increasing peripheral O2 uptake even after stabilization of maximal cardiac output, whereas running may well induce an improvement of all factors which are responsible for aerobic work power.

Breathing pattern during pharmacological activation and blockade of the intermediate area of the ventrolateral surface of the cat medulla.

The present study analyzes the respiratory pattern of chloralose-(50-60 mg/kg, iv) anesthetized cats treated with Nembutal (NE) (30 mg/ml), glycine (GL) (200 mg/ml) or leptazol (LE) (200 mg/ml) topically applied to the intermediate area of the ventrolateral surface of the medulla oblongata in a volume of 20 microliters. Application of NE and GL produced a decrease in ventilation (approximately 24%) and tidal volume (approximately 25%) suggesting that the intermediate area facilitates respiratory drive and inhibits the inspiratory off-switch mechanism. These results are consistent with the view that intermediate area is necessary for the central chemosensitivity to CO2. The topical application of LE produced an increase in inspiration time (12.5%), expiration time (20.8%) and tidal volume (7%). The increased tidal volume caused by LE is compatible with its action as a GL antagonist.

Effect of exercise training during pregnancy: maternal and fetal responses of the rat.

Pregnancy duration, offspring number, body weight gain per day, as well as offspring body and heart weights were studied in pregnant Wistar rats subjected to exercise training at relative work loads of 60, 70, 80 or 90% of maximum oxygen consumption (VO2max) (N = 6 for each group). Pregnancy duration, offspring number and heart weight of the rats subjected to exercise during pregnancy were not different from the control group not subjected to exercise training. Body weight gain per day of pregnant rats subjected to exercise was 4.64 +/- 0.21, 4.79 +/- 0.22 and 4.72 +/- 0.12 g, respectively, for work loads of 70, 80 or 90% of VO2max. This decrease of body weight gain per day was significantly different (P less than 0.05) from the control group (5.69 +/- 0.22 g). The offspring body weight decreased in the rats submitted to work loads of 70, 80 and 90% of VO2max (5.30 +/- 0.05, 5.34 +/- 0.02 and 5.24 +/- 0.01 g, respectively) by comparison to the control group value (5.73 +/- 0.07 g). These results suggest that only intense exercise could impair body weight gain in pregnant rats and their offspring.

Potassium-induced ventilatory reflexes originating from the dog hindlimb during rest and passive exercise.

1. It has been previously shown that Ketalar-anesthetized dogs do not exhibit alterations either in ventilation or in oxygen uptake during passive motion. In the present study, the same model was used to study the effects induced by increasing extracellular K+ to the concentration achieved during active exercise. 2. The isolated hindlimbs of twelve dogs anesthetized with ketamine hydrochloride i.v., after induction with sodium pentobarbital, were perfused with control (2.8 mM KCl) and experimental (8 mM KCl) physiological solutions under resting conditions, and in passive motion. 3. Respiratory minute volume (VE), respiratory rate (f) and tidal volume (VT) were determined by collecting the expired air in a Tissot gasometer. 4. During the control perfusion, the values of VE, f and VT for passive exercise did not differ significantly from those obtained under resting conditions. However, during perfusion with 8 mM KCl, a significant increase in VE was observed, possibly due to an increase of VT under resting conditions and to an increase of f during passive exercise. 5. The results suggest that passive exercise can induce a significant increase in ventilation only when accompanied by local chemical changes such as an increase in extracellular K+.

Breathing pattern during exercise in myopathic subjects.

Previous studies have described a neurogenic-induced ventilatory tachypneic response during exercise. The present paper compares the breathing pattern of control and myopathic human subjects submitted to exercise. Peripheral neurogenic stimuli (PNS) at the same level of oxygen consumption should be enhanced in myopathic subjects as a consequence of muscular mass loss. Myopathic individuals showed hyperventilation (increased VeO2 and VeCO2) which was mostly due to higher respiratory frequency. The shorter respiratory cycle was due chiefly to Te reduction, since the Ti/TTOT ratio was greater in the myopathic individuals for a VO2 of 1 L. These results are in agreement with previous studies in anesthetized dogs and in unanesthetized humans in which a tachypneic mechanism associated to the relative work load was observed. These results also suggest that PNS may have a facilitatory effect upon the inspiratory off switch mechanism.

Cardiorespiratory responses to exercise in patients with spinal muscular atrophy and limb-girdle dystrophy.

Maximum oxygen consumption, maximum heart rate and maximum ventilation during cycle ergometer exercise were studied in individuals with spinal muscular atrophy (N = 8) and limb-girdle dystrophy (N = 8). The limiting factors in aerobic power may be related to loss of functional muscular mass rather than to changes in the oxygen transport system. There was no correlation between VO2 max values and muscle strength as determined by a manual test of the affected muscles recruited for bicycle exercise. The results, therefore, do not support the possibility of a correlation between these indices previously proposed on the basis of clinical evidence.

Effects of caffeine on the rate of perceived exertion.

The role of caffeine in improving performance in endurance exercises is controversial and its mechanism of action is not well understood. The purpose of the present study was to evaluate the effects of caffeine on the rate of perceived exertion (RPE) by exercising athletes. Six male non-smoking runners, aged 26.8 +/- 4.9 years (mean +/- SD), who had been in training continuously for at least two years before the experiment were studied. Mean maximum oxygen consumption (VO2max) was 61.21 +/- 5.36 ml kg-1 min-1. The subjects were asked to exercise on a bicycle ergometer for 3 min each at 300 and 600 kg m min-1, after which the work load was elevated to 1200 kg m min-1 and they exercised until exhaustion. In order to evaluate the effects of caffeine, the exercise was performed twice following the ingestion of 200 ml decaffeinated coffee with and without caffeine (5 mg/kg body weight). Caffeine had no significant effect on exercise time, pulmonary ventilation, oxygen consumption, carbon dioxide extraction or exchange respiratory ratio, but the RPE was significantly lower (P less than 0.05) at the work load of 1200 kg m min-1 after the ingestion of caffeine for both trials I and II. The present results suggest that metabolic acidosis and glycogen depletion were not the main causes of exhaustion.

Oxygen consumption and ventilation during constant-load exercise in runners and cyclists.

The effect of using specialized or no specialized muscle groups on ventilatory threshold (VT) and on maintenance of steady-state oxygen consumption during long term exercise on treadmill and on cycle ergometer was studied in ten endurance runners and nine cyclists. Initially, maximum oxygen consumption (VO2max) and VT were determined. Oxygen consumption (VO2) ventilation (VE) respiratory rate (f), and blood lactate (in the beginning and at the end of exercise) were measured during exercise at constant relative loads of 60, 70, and 80% of VO2max. In the runners, both VO2max and VT (expressed as % VO2max and VO2 l/min) were greater on treadmill than on cycle ergometer and in the cyclists, VO2max was higher on cycle ergometer than on treadmill, but no differences in VT were detected between the two tests. The VO2, VE, and f drifts correlated with blood lactate level as well as with the calculated VT. The results suggest that the effect of using specialized or no specialized muscle groups on the maintenance of VO2 steadiness is achieved through training-induced changes on the level of blood lactate and, in VT.

Aerobic training effects on maximum oxygen consumption, lactate threshold and lactate disappearance during exercise recovery of dogs.

1. Dogs were submitted to an aerobic training schedule and its maximum oxygen consumption, lactate threshold and lactate concentration during recovery were compared among the following conditions: not trained (UT), after 1 month of training (T1), after 2 months of training (T2) and after detraining (DT). 2. Maximum oxygen consumption increased significantly in relation to UT condition only at T2 condition. The detraining reversed this alteration. 3. Lactate threshold when expressed as Vo2 or absolute work load increased significantly after aerobic training (T2) but did not present any alteration when it was expressed as % of Vo2 max. 4. The lactate decreasing during recovery did not differ between the four experimental conditions (after 10 min). 5. The latency time for the lactate concentration to reach the top values was reduced by aerobic training (T2).

Effects of exercise and food restriction in pregnant and newborn rats. Pre-pregnancy maximum oxygen consumption.

1. In the present study, the effects of exercise and food restriction in pregnant and newborn rats were investigated. 2. The following groups were formed: adequate food supply, with and without exercise (AE and AN) and 30% food restriction, with and without exercise (RE and RN). 3. Exercise was performed throughout the pregnancy on a treadmill at a speed of 18 m/min for 30 min/day, which represented 84% of maximum VO2. 4. The results show that food restriction affected body weight gain while exercise only affected the RE group (P < 0.05). 5. Body temperature was increased by exercise. The initial temperature was lower in group RE. 6. No differences were obtained in average offspring number but reabsorption, preterm and natimortality were observed in group RE. 7. Newborn body weight was lowered by food restriction rather than by exercise. 8. Newborn brain and heart weights were not affected but lung and liver weights were significantly affected by the nutritional factor (P < 0.05).

Reactive oxygen species in pregnant rats: effects of exercise and thermal stress.

With the aim of evaluating the effect of interaction between physical training or exercise only during pregnancy and thermal stress on oxidative stress, and antioxidant mechanism sedentary pregnant rats (PS), exercised pregnant rats only during pregnancy (PE) and trained rats submitted to also exercise during pregnancy (PT) were compared (N=63). Exercise sessions consisted of swimming at 80% of maximal work load supported into water at 28 degrees C (hypothermia, PS 28, PE28, PT28) or 35 degrees C (thermal neutrality, PS35, PE35, PT35) or 39 degrees C (hyperthermia, PS39, PE39, PT39), for 30 min. The initial body weight in all groups of rats was from 177 to 207 g. On the 20th day of pregnancy, 24 h after the last immersion or swimming session venous blood was collected to determine oxidative stress. Plasma concentrations of means malondialdehyde (MDA) values measured as thiobarbituric acid reactive substances (TBARS); total glutathione (GSH) and vitamin E were determined. The oxidative stress index was calculated from the ratio TBARS/GSH and TBARS/Vitamin E. TBARS did not change on the group PE at different temperatures of water; TBARS were higher for PS28 than PS35 and PS39; PT35 had higher values than PT28 and PT39. For GSH, PS39 was lower than PS35; PE28 was higher than PE35 and PE39 and PT35 were lower than PT28 and PT39. Plasma concentration of vitamin E did not present any difference for sedentary rats at different water temperatures, but for PE28, the values were lower than for PE35 and PE39, whereas PT39 was lower than PT35 and PT28. In relation to TBARS/GSH, it was verified an increase in oxidative stress for PS28 (in relation to PS35 and PS39), PE35, and PT35 (in relation to PE28 and PE39 or PT28 and PT39); regarding the ratio TBARS/vitamin E, the highest values were obtained at 35 degrees C for PS and PT groups and at 39 for PE group. These results have shown the great complexity of the interaction between physical training, thermal stress and pregnancy. Apparently, hypothermia produces large index of oxidative stress only in sedentary rats, but this index was greater at 35 degrees C in relation to extreme temperatures for trained rats. These results have suggested that physical training allows a more efficient activation of antioxidant mechanisms under thermal stress.

Effect of exercise during pregnancy, graded as a percentage of aerobic capacity: maternal and fetal responses of the rat.

1. A number of variables were studied in pregnant rats that underwent strenuous exercise during pregnancy. They were: total weight gain, daily weight gain, length of pregnancy, number of offspring. Also the weight, the heart weight and fibre/capillary ratio of the newborn male rats and their VO2 max at 90 days were measured. 2. The exercise was graded in accordance to previous aerobic capacity as determined by VO2 max with relative loads of 60% (E60), 70% (E70), 80% (E80) and 90% (E90) of VO2 max being applied to the various groups (N = 6 per group). 3. The total weight gain and daily weight gain was significantly less in the E70, E80 and E90 groups. Weight gain in the anabolic phase (0-14d) was not different, but during the first week the weight gain in the E90 group was significantly less than control group. In the catabolic phase the observations were similar the first week of the anabolic phase. 4. Length of pregnancy, heart weight offspring and VO2 max of 90-day-old male rats were not significantly different. The number of offspring of the E90 group was significantly smaller than the control, E60 and E70 groups. 5. The offspring body weight was less in the E70, E80 and E90 groups than control group and was significantly less in the E90 group compared to the E60 and E70 groups. 6. The fibre/capillary ratio of the offspring was different in the E90 group compared to the control group. 7. These results suggest that the effect of exercise depends on the relative work load applied to the mother and these effects are particularly marked at high work loads.

Swimming of pregnant rats at different water temperatures.

We studied the chronic effect of exercise during water immersion, associated with thermal stress (water temperature at 22, 35 and 40 degrees C) at an intensity of 80% of maximal work load supported in pregnant rats (P) and non-pregnant female rats (NP). P and NP were subdivided into three subgroups according to water temperature during exercise (P22 and NP22; P35 and NP35; P40 and NP40). The animals were submitted to daily swimming sessions of 10-15 min, for 19 days of pregnancy (P) or experimental conditions (NP). Plasma concentration of triglycerides, cholesterol, glucose, total protein, albumin and corticosterone were determined 24 h after the last exercise session. Weight gain and rectal temperature pre- and post-swimming session were also determined. The offspring were examined just after caesarian section on the 20th day of pregnancy to check weight, length and litter size. Pregnant rats showed an increase of triglycerides, reduction of glycemia, total protein and albumin and cholesterol (at 35 degrees C) when compared to non-pregnant animals. Such effects probably lead to an adequate delivery of substrate to the fetus and prepare the mother for lactation. Daily thermal stress did not modify metabolic responses to exercise in pregnant rats. Results also show a deleterious effect on offspring when the mother is exposed daily to extreme temperatures during swimming. These results suggest that water temperature (cold and hot) in swimming have to be considered to avoid damage in fetal development.

The influence of isotonic exercise on cardiac hypertrophy in arterial hypertension: impact on cardiac function and on the capacity for aerobic work.

Intense physical training through isotonic exercises has controversial effects in individuals with moderate to severe hypertension. In this study, normotensive Wistar rats and rats with renovascular hypertension (Goldblatt II) were subjected to intense physical exercise involving two 50-min swimming sessions per day for a period of 12 weeks. At the end of the study, we evaluated the effect of training on arterial pressure, the capacity for aerobic work and cardiac function. Our results demonstrate that intense physical training has no effect on the arterial blood pressure of normotensive rats or of animals with moderate renovascular hypertension. Hypertensive animals with cardiac hypertrophy require a greater period of training in order to attain the same capacity for aerobic work as normotensive rats. This difference may result from an inability of the former animals to increase cardiac compliance, thereby impeding more extensive usage of the Frank-Starling mechanism to subsequently increase the systolic cardiac performance. Cardiac hypertrophy induced by exercise did not summate with that induced by arterial hypertension. Physical exercise normalized the end-diastolic left ventricular pressure in hypertensive animals without any corresponding increase in the compliance of the chamber. The first derivative of left ventricular pulse pressure (+/- dP/dt) was greater in the hypertensive trained group than in the hypertensive sedentary rats. These observations suggest that a systolic dysfunction of the left ventricle involving an elevated residual volume secondary to arterial hypertension may be corrected by physical exercise such as swimming.

Effects of caffeine on the rate of perceived exertion

The role of caffeine in improving performance in endurance exercises is controversial and its mechanism of action is not well understood. The purpose of the present study was to evaluate the effects of caffeine on the rate of perceived exertion (RPE) by exercising athletes. Six male non-smoking runners, aged 26.8 ñ 4.9 years (mean ñ SD), who had been in training continuously for at least two years before the experiment were studied. Mean maximum oxygen consumption (VO2max) was 61.21 ñ 5.36 ml kg**-1 min**-1. The subjects were asked to exercise on a bicycle ergometer for 3 min each at 300 and 600 kg m min**-1, after which the work load was elevated to 1200 kg m min**-1 and they exercised until exhaustion. In order to evaluate the effects of caffeine, the exercicse was performed twice following the ingestion of 200 ml decaffeinated coffee with and without caffeine (5 mg/kg body veight). Caffeine had no significant effect on exercise time, pulmonary ventilation, oxygen consumption, carbon dioxide extraction or exchange respiratory ratio, but the RPE was significantly lower (P<0.05) at the work load of 1200 kg m min**-1 after the ingestion of caffeine for both trials I and II. The present results suggest that metabolic acidosis and glycogen depletion were not the main causes of exhaustion

Effect of exercise training during pregnancy: maternal and fetal responses of the rat

Pregnancy duration, offspring number, body weight gain per day, as well as offspring body and heart weights were studied in pregnant Wistar rats subjected to exercise training at relative work loads of 60, 70, 80 or 90% of maximum oxygen consumption (VO2max) (N = 6 for each group). Pregnancy duration, offspring number and heart weight of the rats subjected to exercise during pregnancy were not different from the control group not subjected to exercise training. Body weight gain per day of pregnant rats subjected to exercise was 4.64 + or - 0.21, 4.79 + or - 0.12 g, respectively, for work loads of 70,80 or 90% of VO2max. This decrease of body weight gain per day was ignificantly different (P<0.05) from the control group (5.69 + or - 0.22 g). The offspring body weight decreased in the rats submitted to work loads of 70,80 and 90% of VO2max(5.3-0 + or - 0.02 and 5.24 + or - 0.01g, respectively) by comparison to the control group value (5.73 + or - 0.07 g). These results suggest that only intense exercise could impair body weight gain in pregnant rats and their offspring

Breathing pattern during pharmacological activation and blockade of the intermediate area of the ventrolateral surface of the cat medulla

The present study analyzes the respiratory pattern of chloralose- (50-60 mg/kg,iv) anesthetized cats treated with Nembutal (NE) (30 mg/ml), glycine (GL) (200 mg/ml) or leptazol (LE) (200 mg/ml) topically applied to the intermediate area of the ventrolateral surface of the medulla oblongata in a volume of 20 micronl. Application of NE and GL produced a decrease in ventilation (-24%) and tidal volume (-25%) suggesting that the intermediate area facilitates respiratory drive and inhibits the inspiratory off-switch mechanism. These results are consistent with the view that intermediate area is necessary for the central chemosensitivity to CO2. The topical application of LE produced an increase in inspiration time (12.5%), expiration time (20.8%) and tidal volume (7%). The increased tidal volume caused by LE is compatible with it action as a GL antagonist