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.

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

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

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).

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.

Effects of diet and thermal acclimation on oxygen consumption in rats.

The relationship between food intake and oxygen consumption was studied in a group of 60 rats acclimated at environmental temperatures of either 30 or 10 degrees C. Three separate experiments were performed. In the first, 28 rats were divided into two groups: control, which received 20 and 32 g of food/day at 30 and 10 degrees C, respectively, from 0800 to 1700 and experimental, which received 10 and 25 g of food/day at 30, and 10 degrees C, respectively. The experimental period lasted 6 weeks. Oxygen consumption was measured weekly at environmental temperatures of 5, 15, 25, 30, and 35 degrees C. In the second experiment, 16 rats were subjected to the same food intake as the animals in the first experiment. After 1 week, their oxygen consumption was measured at 25 degrees C over a period of 24 h. The third experiment was carried out with 16 other rats in which the control groups received the same amount of food as in the first experiment, and the experimental groups were fed 6 and 11 g/day at 30 and 10 degrees C, respectively, during 1 week. In the first experiment, no changes in oxygen consumption (per kilogram 0.67) were apparent in the experimental rats during 6 weeks. However, after 1 week on severe food restriction a significant decrease in oxygen consumption (per kilogram 0.67) was observed. A long-lasting thermic effect of food was observed in control rats from the second experiment and a rapid effect was apparent in restricted rats.(ABSTRACT TRUNCATED AT 250 WORDS)

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 temperature acclimation on rabbit metabolic rate and rectal temperature.

The metabolic rates and rectal temperatures of cold-(10 degrees C), warm-(20 degrees C) and heat-(30 degrees C) acclimated rabbits were measured at 10, 20 and 30 degrees C. When the logarithm of metabolic rate was plotted against the logarithm of body weight, no differences could be demonstrated between the slopes of the lines obtained for each of the nine experimental groups. Metabolic rate, expressed as kcal h-1 kg-1, kcal h-1 kg-3/4 and kcal h-1 kg-2/3, was mass-independent for most of the experimental conditions. The rabbits were able to maintain constant rectal temperature during cold or heat exposure only when previously acclimated to these temperature extremes. The increase in metabolic rate of cold-acclimated rabbits observed during cold exposure seemed to be too low to explain the maintenance of rectal temperature. The lower metabolic rate of heat-acclimated rabbits exposed to heat probably played an important role in preventing increased rectal temperatures.

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.

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.

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+.