Food intake in the exercising rat: A brief review

Contrary to the current model based on Mayer's work, increasing levels of exercise does not lead to caloric compensation in the male rat. While female rats show compensatory hyperphagia in response to forced or spontaneous exercise male rats do not. These conclusions apply only to studies employing premixed chow. The kind of exercise (e.g. running vs burrowing) may also affect feeding differentially.     

Comparison of supine and sitting body position during a triangular exercise test

Summary A comparison of haemodynamic parameters is performed during a triangular exercise test on bicycle ergometer in respect of studying the influence of supine and sitting body position.At the maximal symptom-limited work load reached the heart rate is on the average 9.2% higher, the arterial systolic pressure 16.1% and the cardiac output 17.2% less in the sitting body position (P<0.001).On the opposite the pulmonary artery pressure during work is of slightly but not significantly higher level in the sitting position than in the supine. This phenomenon is explained by a prevailing of the beta-adrenergic tonus in our untrained subjects, while total sympathetic stimulation seems to be comparable in both body positions.     

The effect of exercise on bleeding time and local production of prostacyclin and thromboxane

Summary Exercise at a heart rate corresponding to 30% for 15 min was associated with an increase in the volume of bleeding time blood from a mean of 133 μl before exercise to a mean of 218 μl during and immediately after the exercise. There was similarly an increase in thromboxane B₂ production from 6.40 nmol·l⁻¹ before to 11.50 nmol·l⁻¹. Most subjects also showed an increase in the length of the bleeding time and in the production of bleeding time 6-keto-PGF_1α. The extent of increase in the bleeding time and in production of 6-keto-PGF_1α was quite variable, with subjects showing the largest increases in bleeding time also demonstrating the greatest increases in 6-keto-PGF_1α (r=0.76,P=0.004). The ingestion of aspirin before exercise markedly inhibited basal bleeding time thromboxane B₂ production and blocked the exercise-associated increments in thromboxane B₂ and 6-keto-PGF_1α production. While the aspirin itself increased the length of the bleeding time, there was not any further increase associated with exercise. In contrast to the effects of acute short-term exercise, long-distance running was associated with a significant decrease in bleeding time, but no change in bleeding time blood volume, bleeding time thromboxane B₂, or bleeding time 6-keto-PGF_1α. The results show that acute low-level exercise can be associated with significant changes in the volume of blood oozing from a bleeding time incision and in the amount of thromboxane production stimulated at the incisional site. Following exhaustive exercise of long duration, the above changes are no longer seen.     

Exercise-induced intermittent angina and ST-segment elevation in Prinzmetal's angina

A patient with primary angina showed intermittent ST elevation(with and without chest pain), during two exercise tests performedon consecutive days; the same ST changes were also seen duringthe recovery phase. The electrocardiographic changes recorded in this patient maybe considered an example of myocardial response to spasm-relatedischemia.     

Effects of a brisk walk on blood pressure responses to the Stroop, a speech task and a smoking cue among temporarily abstinent smokers

A review and meta-analysis by Hamer et al. (2006) showed that a single session of exercise can attenuate post-exercise blood pressure (BP) responses to stress, but no studies examined the effects among smokers or with brisk walking. Healthy volunteers (n=60), averaging 28 years of age and smoking 15 cigarettes daily, abstained from smoking for 2 h before being randomly assigned to a 15-min brisk semi-self-paced walk or passive control condition. Subject characteristics, typical smoking cue-elicited cravings and BP were assessed at baseline. After each condition, BP was assessed before and after three psycho-social stressors were carried out: (1) computerised Stroop word–colour interference task, (2) speech task and (3) only handling a lit cigarette. A two-way mixed ANCOVA (controlling for baseline) revealed a significant overall interaction effect for time by condition for both systolic blood pressure (SBP) and diastolic blood pressure (DBP). Univariate ANCOVAs (to compare between-groups post-stressor BP, controlling for pre-stressor BP) revealed that exercise attenuated systolic BP and diastolic BP responses to the Stroop and speech tasks and SBP to the lit cigarette equivalent to an attenuated SBP and DBP of up to 3.8 mmHg. Post-exercise attenuation effects were moderated by resting blood pressure and self-reported smoking cue-elicited craving. Effects were strongest among those with higher blood pressure and smokers who reported typically stronger cravings when faced with smoking cues. Blood pressure responses to the lit cigarette were not associated with responses to the Stroop and speech task. A self-paced 15-min walk can reduce smokers’ SBP and DBP responses to stress, of a magnitude similar on average to non-smokers.     

Perception of drinking water temperature and effects for humans after exercise

Subjects rated the perceived temperature and hedonic values of four samples of drinking water (5 degrees, 16 degrees, 22 degrees, 38 degrees C) after exercise and on a control day. Ad lib drinking of any of the four samples was permitted for 20 minutes after exercise and intake was measured. Subjects completed questionnaires pertaining to their subjective states. Sensory thermal neutral water was found to be close to 22 degrees C which was also judged to be affectively neutral. Subjects rated 16 degrees C water higher on the hedonic scale after exercise than they did on a control day, despite the fact that no change in the perception of this temperature was observed. Responses to the symptoms questionnaire showed a marked effect of exercise on the perception of thirst, sweating, body warmth and dryness in the mouth. Sensations of stomach fullness could not account for the incomplete rehydration of most subjects in the time allotted. It was suggested that a rapid reduction in symptoms which initiate drinking was responsible for drinking termination. The role of water temperature in the reduction of thirst symptoms was discussed.     

Effect of prolonged exercise on the level of triglycerides in the rat liver

Summary This study examined the effect of prolonged exercise on the level of triglycerides (TG) in rat liver. The rats were divided into groups: 1-control, 2-treated with nicotinic acid, 3-fed with glucose during exercise, 4-fasted, 5-adrenalectomized, 6-adrenalectomized and fed with oil. In the control group, there was gradual accumulation of TG in the liver and their level was doubled at exhaustion as compared to the resting value. Nicotinic acid lowered the resting level of TG and prevented their accumulation during exercise. Administration of glucose during exercise partially prevented the increase in TG level in the liver. In rats fasted for 24 h before exercise, the net increase in liver TG level during exercise was similar to that in the controls. Adrenalectomy, like nicotinic acid, lowered TG level at rest and prevented its increase during exercise. Feeding the adrenalectomized rats with oil elevated the plasma free fatty acid level but did not result in accumulation of TG in the liver, either at rest or during exercise. It is concluded that prolonged exercise results in accumulation of TG in the liver and that the process depends on the supply of free fatty acids and glucose and requires the presence of glucocorticoids.This work was supported by the Polish Central Programme for Basic Research 06-02.     

Acid-base balance and subjective feelings of fatigue during physical exercise

Six trained male subjects performed exercise on a bicycle ergometer. The external load was increased every minute by 10 watt until exhaustion. The subjects quantified their subjective feeling of fatigue by means of a rating scale.Parameters of acid-base balance (pH, ) were determined in arterial blood from the a. brachialis.Correction of the acidaemia by infusion of NaHCO₃ (8%) during exercise had no effect upon the subjective feeling of fatigue, and except for carbon dioxide output no effect upon some important physiological functions (heart rate, blood pressure, ventilation, and oxygen consumption) during submaximal and maximal exercise.     

Intensity of exercise and heart tissue catecholamine content

Summary The present investigation was primarily aimed at showing, in rats, the relation between intensity of exercise and heart tissue catecholamine depletion. For this purpose two running speeds were chosen; one at 500 m/h, the other at 750 m/h. In the sixth week of exercise, when a steady state in depletion was obtained, the cardiac catecholamine levels were similar at both speeds and were 30% lower when compared to the control animals. However, the onset of this decrease was significant after two weeks of exercise at the higher speed, whereas at the lower speed it was only significant five weeks after the beginning of muscular training. Rats submitted to an enforced training had the same heart tissue catecholamine levels as the spontaneously running ones, except in the fifth week. Some of the rats only slid passively in the drum. Also their heart tissue noradrenaline was not different from the controls. It was concluded that chronic exercise produced a primary catecholamine depletion not related to an increase of the heart weight. Though the onset of depletion was related to the intensity of excersive the final levels were independent of it.     

Reabsorption ofl-glutamine andl-histidine from various regions of the rat proximal convolution studied by stationary microperfusion: Evidence that the proximal convolution is not homogeneous

Summary The glycogen depletion pattern in human muscle fibers was followed throughout the course of prolonged exercise at a work load requiring 67% of the subjects' maximal aerobic power. Biopsy samples were taken from the vastus lateralis muscle at rest and after 20, 60, 120, and 180 (or when unable to continue at the prescribed load) min of exercise. Muscle fibers were identified as fast twitch (FT) or slow twitch (ST) on the basis of myofibrillar ATPase activity. The glycogen content of muscle samples was determined biochemically. At the end of the exercise total muscle glycogen content was very low. Glycogen was also estimated in the fibers with the PAS stain. ST fibers were the first to become depleted of their glycogen but as the exercise progressed, the FT fibers were also depleted. These data may suggest a preferential utilization of ST fibers during prolonged, intense exercise, with a secondary recruitment of FT occuring as the ST fibers became depleted of their glycogen stores.