Endogenous vasopressin and the central control of heart rate during dynamic exercise

The present article contains a brief review on the role of vasopressinergic projections to the nucleus tractus solitarii in the genesis of reflex bradycardia and in the modulation of heart rate control during exercise. The effects of vasopressin on exercise tachycardia are discussed on the basis of both the endogenous peptide content changes and the heart rate response changes observed during running in sedentary and trained rats. Dynamic exercise caused a specific vasopressin content increase in dorsal and ventral brainstem areas. In accordance, rats pretreated with the peptide or the V1 blocker into the nucleus tractus solitarii showed a significant potentiation or a marked blunting of the exercise tachycardia, respectively, without any change in the pressure response to exercise. It is proposed that the long-descending vasopressinergic pathway to the nucleus tractus solitarii serves as one link between the two main neural controllers of circulation, i.e., the central command and feedback control mechanisms driven by the peripheral receptors. Therefore, vasopressinergic input could contribute to the adjustment of heart rate response (and cardiac output) to the circulatory demand during exercise.

Training graduate students to be teachers

Pedagogic education of graduate students, when and where it exists, is restricted to theoretical courses or to the participation of the students as teachers' assistants. This model is essentially reproductive and offers few opportunities for any significant curriculum innovation. To open an opportunity for novelty we have introduced a new approach in "Biochemistry Teaching", a course included in the Biochemistry Graduate Program of the Biochemistry Department (Universidade Estadual de Campinas and Universidade de São Paulo). The content of the course consists of a) choosing the theme, b) selecting and organizing the topics, c) preparing written material, d) establishing the methodological strategies, e) planning the evaluation tools and, finally, f) as teachers, conducting the course as an optional summer course for undergraduate students. During the first semester the graduate students establish general and specific educational objectives, select and organize contents, decide on the instructional strategies and plan evaluation tools. The contents are explored using a wide range of strategies, which include computer-aided instruction, laboratory classes, small group teaching, a few lectures and round table discussions. The graduate students also organize printed class notes to be used by the undergraduate students. Finally, as a group, they teach the summer course. In the three versions already developed, the themes chosen were Biochemistry of Exercise (UNICAMP), Biochemistry of Nutrition (UNICAMP) and Molecular Biology of Plants (USP). In all cases the number of registrations greatly exceeded the number of places and a selection had to be made. The evaluation of the experience by both graduate and undergraduate students was very positive. Graduate students considered this experience to be unique and recommended it to their schoolmates; the undergraduate students benefited from a more flexible curriculum (more options) and gave very high scores to both the courses and the teachers.

Response of the arterial blood pressure of quadriplegic patients to treadmill gait training

Blood pressure pattern was analyzed in 12 complete quadriplegics with chronic lesions after three months of treadmill gait training. Before training, blood pressure values were obtained at rest, during treadmill walking and during the recovery phase. Gait training was performed for 20 min twice a week for three months. Treadmill gait was achieved using neuromuscular electrical stimulation, assisted by partial body weight relief (30-50%). After training, blood pressure was evaluated at rest, during gait and during recovery phase. Before and after training, mean systolic blood pressures and heart rates increased significantly during gait compared to rest (94.16 ± 5.15 to 105 ± 5.22 mmHg and 74.27 ± 10.09 to 106.23 ± 17.31 bpm, respectively), and blood pressure decreased significantly in the recovery phase (86.66 ± 9.84 and 57.5 ± 8.66 mmHg, respectively). After three months of training, systolic blood pressure became higher at rest (94.16 ± 5.15 mmHg before training and 100 ± 8.52 mmHg after training; P < 0.05) and during gait exercise (105 ± 5.22 mmHg before and 110 ± 7.38 mmHg after training; P < 0.05) when compared to the initial values, with no changes in heart rate. No changes occurred in blood pressure during the recovery phase, with the lower values being maintained. A drop in systolic pressure from 105 ± 5.22 to 86.66 ± 9.84 mmHg before training and from 110 ± 7.38 to 90 ± 7.38 mmHg after training was noticed immediately after exercise, thus resulting in hypotensive symptoms when chronic quadriplegics reach the sitting position from the upright position.

Effects of type of physical exercise and leisure activities on the depression scores of obese Brazilian adolescent girls

Several studies have indicated that depressive states may lead to hypokinesia with diminished metabolic rate and energy use. Hypokinesia associated with certain eating behaviors may lead to an unfavorable energy balance that can contribute to the emergence and prevalence of obesity among children and adults. The purpose of the present study was to examine the possibility of reducing depression inventory scores in female adolescents with third-degree obesity while testing the effectiveness of different exercise programs in reducing anxiety and depression scores. The sample consisted of 40 female subjects (mean age 16 ± 1.56 years) divided into 4 groups (aerobic training, anaerobic training, leisure activities, and control). Subjects had a body mass index of 95% or more in relation to the 50th percentile. The aerobic program consisted of three ergometric bicycle sessions per week over a 3-month period (12 weeks) and the activities were prescribed after determining the anaerobic ventilatory threshold (VO2 threshold). Anaerobic training was based on the Wingate anaerobic power test. The leisure program consisted of a varied range of activities (games, exercises, etc.). A nutritionist interviewed the members of these two groups and the control group every week in order to adapt them to the nutritional guidelines proposed for the study. The study showed that all three programs (aerobic exercise, anaerobic exercise and leisure activities) were effective in reducing body mass. However, we found a significant reduction when analyzing the depression scores only for aerobic exercise (18.9 ± 9.33 to 10.6 ± 9.56 or 43.9%) but no significant alterations for anaerobic exercise (11.36 ± 5.23 to 9.63 ± 4.78 or 15.22%) and leisure (17.28 ± 7.55 to 15.07 ± 7.54 or 12.78%), thus indicating that in principle this type of activity could be included to improve emotional well-being of obese adolescent girls.

Effect of exercise on the caloric intake of breast cancer patients undergoing treatment

The purpose of this study was to examine the effects of an exercise intervention on the total caloric intake (TCI) of breast cancer patients undergoing treatment. A secondary purpose was to determine whether or not a relationship existed between changes in TCI, body fat composition (%BF), and fatigue during the study, which lasted 6 months. Twenty females recently diagnosed with breast cancer, scheduled to undergo chemotherapy or radiation, were assigned randomly to an experimental (N = 10) or control group (N = 10). Outcome measures included TCI (3-day food diary), %BF (skinfolds), and fatigue (revised Piper Fatigue Scale). Each exercise session was conducted as follows: initial cardiovascular activity (6-12 min), followed by stretching (5-10 min), resistance training (15-30 min), and a cool-down (approximately 8 min). Significant changes in TCI were observed among groups (F1,18 = 8.582; P = 0.009), at treatments 2 and 3, and at the end of the study [experimental (1973 ± 419), control (1488 ± 418); experimental (1946 ± 437), control (1436 ± 429); experimental (2315 ± 455), control (1474 ± 294), respectively]. A significant negative correlation was found (Spearman rho(18) = -0.759; P < 0.001) between TCI and %BF and between TCI and fatigue levels (Spearman rho(18) = -0.541; P = 0.014) at the end of the study. In conclusion, the results of this study suggest that an exercise intervention administered to breast cancer patients undergoing medical treatment may assist in the mitigation of some treatment side effects, including decreased TCI, increased fatigue, and negative changes in body composition.

Training-related changes in the R-R interval at the onset of passive movements in humans

The aim of the present study was to determine whether training-related alterations in muscle mechanoreflex activation affect cardiac vagal withdrawal at the onset of exercise. Eighteen male volunteers divided into 9 controls (26 ± 1.9 years) and 9 racket players (25 ± 1.9 years) performed 10 s of voluntary and passive movement characterized by the wrist flexion of their dominant and non-dominant limbs. The respiratory cycle was divided into four phases and the phase 4 R-R interval was measured before and immediately following the initiation of either voluntary or passive movement. At the onset of voluntary exercise, the decrease in R-R interval was similar between dominant and non-dominant forearms in both controls (166 ± 20 vs 180 ± 34 ms, respectively; P > 0.05) and racket players (202 ± 29 vs 201 ± 31 ms, respectively; P > 0.05). Following passive movement, the non-dominant forearm of racket players elicited greater changes than the dominant forearm (129 ± 30 vs 77 ± 17 ms; P < 0.05), as well as both the dominant (54 ± 20 ms; P < 0.05) and non-dominant (59 ± 14 ms; P < 0.05) forearms of control subjects. In contrast, changes in R-R interval elicited by the racket players' dominant forearm were similar to that observed in the control group, indicating that changes in R-R interval at the onset of passive exercise were not attenuated in the dominant forearm of racket players. In summary, cardiac vagal withdrawal induced by muscle mechanoreflex stimulation is well-maintained, despite long-term exposure to training.

Swimming training down-regulates plasma leptin levels, but not adipose tissue ob mRNA expression

The aim of the present study was to assess the effects of endurance training on leptin levels and adipose tissue gene expression and their association with insulin, body composition and energy intake. Male Wistar rats were randomly divided into two groups: trained (N = 18) and sedentary controls (N = 20). The trained group underwent swimming training for 9 weeks. Leptin and insulin levels, adiposity and leptin gene expression in epididymal and inguinal adipose tissue were determined after training. There were no differences in energy intake between groups. Trained rats had a decreased final body weight (-10%), relative and total body fat (-36 and -55%, respectively) and insulin levels (-55%) compared with controls (P < 0.05). Although trained animals showed 56% lower leptin levels (2.58 ± 1.05 vs 5.89 ± 2.89 ng/mL in control; P < 0.05), no difference in leptin gene expression in either fat depot was demonstrable between groups. Stepwise multiple regression analysis showed that lower leptin levels in trained rats were due primarily to their lower body fat mass. After adjustment for total body fat, leptin levels were still 20% (P < 0.05) lower in exercised rats. In conclusion, nine weeks of swimming training did not affect leptin gene expression, but did lead to a decrease in leptin levels that was independent of changes in body fat.

Long-term aerobic swimming training by rats reduces the number of aberrant crypt foci in 1,2-dimethylhydrazine-induced colon cancer

We determined the effect of long-term aerobic swimming training regimens of different intensities on colonic carcinogenesis in rats. Male Wistar rats (11 weeks old) were given 4 subcutaneous injections (40 mg/kg body weight each) of 1,2-dimethyl-hydrazine (DMH, dissolved in 0.9% NaCl containing 1.5% EDTA, pH 6.5), at 3-day intervals and divided into three exercise groups that swam with 0% body weight (EG1, N = 11), 2% body weight (EG2, N = 11), and 4% body weight of load (EG3, N = 10), 20 min/day, 5 days/week for 35 weeks, and one sedentary control group (CG, N = 10). At sacrifice, the colon was removed and counted for tumors and aberrant crypt foci. Tumor size was measured and intra-abdominal fat was weighed. The mean number of aberrant crypt foci was reduced only for EG2 compared to CG (26.21 ± 2.99 vs 36.40 ± 1.53 crypts; P < 0.05). Tumor incidence was not significantly different among groups (CG: 90%; EG1: 72.7%; EG2: 90%; EG3: 80%). Swimming training did not affect either tumor multiplicity (CG: 2.30 ± 0.58; EG1: 2.09 ± 0.44; EG2: 1.27 ± 0.19; EG3: 1.50 ± 0.48 tumors) or size (CG: 1.78 ± 0.24; EG1: 1.81 ± 0.14; EG2: 1.55 ± 0.21; EG3: 2.17 ± 0.22 cm³). Intra-abdominal fat was not significantly different among groups (CG: 10.54 ± 2.73; EG1: 6.12 ± 1.15; EG2: 7.85 ± 1.24; EG3: 5.11 ± 0.74 g). Aerobic swimming training with 2% body weight of load protected against the DMH-induced preneoplastic colon lesions, but not against tumor development in the rat.

Exercise may cause myocardial ischemia at the anaerobic threshold in cardiac rehabilitation programs

Myocardial ischemia may occur during an exercise session in cardiac rehabilitation programs. However, it has not been established whether it is elicited when exercise prescription is based on heart rate corresponding to the anaerobic threshold as measured by cardiopulmonary exercise testing. Our objective was to determine the incidence of myocardial ischemia in cardiac rehabilitation programs according to myocardial perfusion SPECT in exercise programs based on the anaerobic threshold. Thirty-nine patients (35 men and 4 women) diagnosed with coronary artery disease by coronary angiography and stress technetium-99m-sestamibi gated SPECT associated with a baseline cardiopulmonary exercise test were assessed. Ages ranged from 45 to 75 years. A second cardiopulmonary exercise test determined training intensity at the anaerobic threshold. Repeat gated-SPECT was obtained after a third cardiopulmonary exercise test at the prescribed workload and heart rate. Myocardial perfusion images were analyzed using a score system of 6.4 at rest, 13.9 at peak stress, and 10.7 during the prescribed exercise (P < 0.05). The presence of myocardial ischemia during exercise was defined as a difference ≥2 between the summed stress score and summed rest score. Accordingly, 25 (64%) patients were classified as ischemic and 14 (36%) as nonischemic. MIBI-SPECT showed myocardial ischemia during exercise within the anaerobic threshold. The 64% prevalence of ischemia observed in the study should not be looked on as representative of the whole population of patients undergoing exercise programs. Changes in patient care and exercise programs were implemented as a result of our finding of ischemia during the prescribed exercise.

Effects of chronic treadmill training on body mass gain and visceral fat accumulation in overfed rats

This study evaluated the effects of chronic treadmill training on body mass gain and visceral fat accumulation in overfed rats. Overfeeding was induced by reducing the litter size to 3 male pups per mother during the suckling period. The litter size of control rats was adjusted to 10 male pups per mother. Seven weeks after birth overfed and normally fed rats were selected and assigned to a sedentary protocol or to a low-intensity treadmill training protocol (60 min, 5 times/week, for 9 weeks). Four groups (overfed sedentary, N = 23; normally fed sedentary, N = 32; overfed exercised, N = 18, and normally fed exercised, N = 18) were evaluated at 18 weeks. Data are reported as means ± SEM. Initial body weight was similar in control and overfed rats [8.0 ± 0.2 g (N = 42) vs 8.0 ± 0.1 g (N = 50); P > 0.05] and body weight gain during the suckling period was higher in the overfed rats (30.6 ± 0.9 vs 23.1 ± 0.3 g; P < 0.05). Exercise attenuated the body weight gain of overfed compared to sedentary rats (505 ± 14 vs 537 ± 12 g; P < 0.05). The sedentary overfed rats showed higher visceral fat weight compared to normally fed animals (31.22 ± 2.08 vs 21.94 ± 1.76 g; P < 0.05). Exercise reduced visceral fat by 36.5% in normally fed rats and by 35.7% in overfed rats. Exercise attenuated obesity in overfed rats and induced an important reduction of visceral fat.

Effect of aerobic training on EEG alpha asymmetry and depressive symptoms in the elderly: a 1-year follow-up study

The effect of physical exercise on the treatment of depressive elderly adults has not been investigated thus far in terms of changes in cortical hemispheric activity. The objective of the present study was to identify changes in depressive symptoms, quality of life, and cortical asymmetry produced by aerobic activity. Elderly subjects with a diagnosis of major depressive disorder (DSM-IV) were included. Twenty patients (70% females, 71 ± 3 years) were divided into an exercise group (pharmacological treatment plus aerobic training) and a control group (undergoing pharmacological treatment) in a quasi-experimental design. Pharmacological treatment was maintained stable throughout the study (antidepressants and anxiolytics). Subjects were evaluated by depression scales (Beck Depression Inventory, Hamilton Depression Rating Scale, Montgomery-Asberg Depression Rating Scale) and the Short Form Health Survey-36, and electroencephalographic measurements (frontal and parietal alpha asymmetry) before and after 1 year of treatment. After 1 year, the control group showed a decrease in cortical activity on the right hemisphere (increase of alpha power), which was not observed in the exercise group. The exercise group showed a significant decrease of depressive symptoms, which was not observed in the control group. This result was also accompanied by improved treatment response and remission rate after 1 year of aerobic exercise associated with treatment. This study provides support for the effect of aerobic training on alpha activity and on depressive symptoms in elderly patients. Exercise facilitates the treatment of depressive elderly adults, leading to clinical and physical improvement and protecting against a decrease in cortical activity.

Participation of endogenous opioids in the antinociception induced by resistance exercise in rats

Exercise is a low-cost intervention that promotes health and contributes to the maintenance of the quality of life. The present study was designed to investigate the influence of different resistance exercise protocols on the nociceptive threshold of rats. Female Wistar rats were used to perform exercises in a weight-lifting exercise model. The following groups were examined (N = 6 per group): untrained rats (control group); an acute protocol group consisting of rats submitted to 15 sets of 15 repetitions of resistance exercise (acute group); rats exercised with 3 sets of 10 repetitions, three times per week for 12 weeks (trained group), and a group consisting of trained rats that were further submitted to the acute protocol (trained-acute group). The nociceptive threshold was measured by the paw-withdrawal test, in which the withdrawal threshold (escape reaction) was measured by an apparatus applying force to the plantar surface of the animal paw. The opioid antagonist naloxone (2 mg/kg) was administered subcutaneously 10 min before the exercise protocols. The trained group demonstrated antinociception only up to day 45 of the 12-week training period. A significant increase (37%, P < 0.05) in the nociceptive threshold was produced immediately after exercise, decreasing to 15% after 15 min, when the acute exercise protocol was used. Naloxone reversed this effect. These data show that the acute resistance exercise protocol was effective in producing antinociception for 15 min. This antinociceptive effect is mediated by the activation of opioid receptors.

Relationship between work rate and oxygen uptake in mitochondrial myopathy during ramp-incremental exercise

We determined the response characteristics and functional correlates of the dynamic relationship between the rate (Δ) of oxygen consumption ( O2) and the applied power output (work rate = WR) during ramp-incremental exercise in patients with mitochondrial myopathy (MM). Fourteen patients (7 males, age 35.4 ± 10.8 years) with biopsy-proven MM and 10 sedentary controls (6 males, age 29.0 ± 7.8 years) took a ramp-incremental cycle ergometer test for the determination of the O2 on-exercise mean response time (MRT) and the gas exchange threshold (GET). The ΔO2/ΔWR slope was calculated up to GET (S1), above GET (S2) and over the entire linear portion of the response (S T). Knee muscle endurance was measured by isokinetic dynamometry. As expected, peak O2 and muscle performance were lower in patients than controls (P < 0.05). Patients had significantly lower ΔO2/ΔWR than controls, especially the S2 component (6.8 ± 1.5 vs 10.3 ± 0.6 mL·min-1·W-1, respectively; P < 0.001). There were significant relationships between ΔO2/ΔWR (S T) and muscle endurance, MRT-O2, GET and peak O2 in MM patients (P < 0.05). In fact, all patients with ΔO2/ΔWR below 8 mL·min-1·W-1 had severely reduced peak O2 values (<60% predicted). Moreover, patients with higher cardiopulmonary stresses during exercise (e.g., higher Δ ventilation/carbon dioxide output and Δ heart rate/ΔO2) had lower ΔO2/ΔWR (P < 0.05). In conclusion, a readily available, effort-independent index of aerobic dysfunction during dynamic exercise (ΔO2/ΔWR) is typically reduced in patients with MM, being related to increased functional impairment and higher cardiopulmonary stress.

Do whole-body vibration exercise and resistance exercise modify concentrations of salivary cortisol and immunoglobulin A?

A single bout of resistance exercise (RE) induces hormonal and immune responses, playing an important role in a long-term adaptive process. Whole-body vibration (WBV) has also been shown to affect hormonal responses. Evidence suggests that combining WBV with RE may amplify hormonal and immune responses due to the increased neuromuscular load. Therefore, the aim of this study was to evaluate salivary cortisol (Scortisol) and salivary IgA (SIgA) concentrations following a RE session combined or not with WBV. Nine university students (22.9 ± 5.1 years, 175.8 ± 5.2 cm, and 69.2 ± 7.3 kg) performed five sets of squat exercise (70% one-repetition-maximum) combined (R+V30) or not (R) with WBV at 30 Hz. Saliva samples were obtained before and after exercise. Subjects also rated their effort according to the Borg CR-10 scale (RPE). Data were analyzed by a mixed model. RPE was higher after R+V30 (8.3 ± 0.7) compared to R (6.2 ± 0.7). However, Scortisol (pre: 10.6 ± 7.6 and 11.7 ± 7.6, post: 8.3 ± 6.3 and 10.2 ± 7.2 ng/mL for R and R+V30, respectively) and SIgA concentrations (pre: 98.3 ± 22.6 and 116.1 ± 51.2, post: 116.6 ± 64.7 and 143.6 ± 80.5 µg/mL for R and R+V30, respectively) were unaffected. No significant correlations were observed between Scortisol and RPE (r = 0.45, P = 0.22; r = 0.30, P = 0.42, for R and R+V30, respectively). On the basis of these data, neither protocol modified salivary cortisol or IgA, although RPE was higher after R+V30 than R.

Functional and morphological effects of resistance exercise on disuse-induced skeletal muscle atrophy

Abstract The reduction of skeletal muscle loss in pathological states, such as muscle disuse, has considerable effects in terms of rehabilitation and quality of life. Since there is no currently effective and safe treatment available for skeletal muscle atrophy, the search for new alternatives is necessary. Resistance exercise (RE) seems to be an important tool in the treatment of disuse-induced skeletal muscle atrophy by promoting positive functional (strength and power) and structural (hypertrophy and phenotypic changes) adaptive responses. Human and animal studies using different types of resistance exercise (flywheel, vascular occlusion, dynamic, isometric, and eccentric) have obtained results of great importance. However, since RE is a complex phenomenon, lack of strict control of its variables (volume, frequency, intensity, muscle action, rest intervals) limits the interpretation of the impact of the manipulation on skeletal muscle remodeling and function under disuse. The aim of this review is to critically describe the functional and morphological role of resistance exercise in disuse-induced skeletal muscle atrophy with emphasis on the principles of training.