Role of exercise training in secondary prevention of ischemic heart disease

Role of lateral parabrachial opioid receptors in exercise-induced modulation of the hypotensive hemorrhage response in conscious male rats

Some of the benefits of exercise appear to be mediated through modulation of neuronal excitability in central autonomic control circuits. Previously, we identified that six weeks of voluntary wheel running had a protective effect during hemorrhage (HEM), limiting both the hypotensive phase of HEM and enhancing recovery. The present study was undertaken to evaluate the role of opioid release in the lateral parabrachial nucleus (LPBN) on the response to severe HEM in chronically exercised (EX, voluntary) versus sedentary (SED) controls. Male Sprague Dawley rats were allowed either free access to running wheels (EX) or normal cage conditions (SED). After 6 weeks of "training" animals were instrumented with a bilateral cannula directed toward the dorsolateral pons and arterial catheters. After a recovery period, animals underwent central microinjection of either vehicle (VEH; n=3/group) or the opioid receptor antagonist naloxone (NAL; n=6/group) followed by withdrawal of 30% of their total estimated blood volume. Following VEH injection, the drop in MAP during and following HEM was significantly attenuated in the EX vs SED animals. Alternatively, NAL microinjection in the dorsolateral pons (20 μM, 200-500 nl) reversed the beneficial effect of EX on the HEM response. NAL microinjection in SED rats did not significantly alter the response to HEM. These data suggest chronic voluntary EX has a beneficial effect on the autonomic response to severe HEM which is mediated, in part, via EX-induced plasticity of the opioid system within the dorsolateral pons.

Daily voluntary exercise alters the cardiovascular response to hemorrhage in conscious male rats

The present study tested the hypothesis that voluntary wheel-exercised rats would better tolerate severe hemorrhage (HEM) compared to age matched sedentary (SED) controls. Conscious rats housed with (EX, n = 8) or without (SED, n = 8) a running wheel for 6 weeks underwent a 30% total blood volume HEM over 15 min and were euthanized 90 min later and brain tissue was processed for Fos-like immunoreactivity (FLI). Both EX and SED groups displayed typical responses to HEM (initial tachycardia followed by decreased HR and MAP) but at the end of HEM, mean arterial pressure (93 ± 6 vs 58 ± 3 mm Hg) and heart rate (316 ± 17 vs. 247 ± 22 bpm,) were higher in the EX vs. SED animals and 60 min following the end of HEM, HR remained significantly elevated in the EX vs SED animals. The altered HR response to HEM in the EX animals was linked to a significant difference in sympatho-vagal drive identified by heart rate variability analysis and an augmented baroreflex response to hypotension tested in a separate group of animals (n = 4-5/group). In many of the brain regions analyzed, EX rats displayed lower levels of FLI compared to SED rats. Significantly lower levels of FLI in the EX vs SED rats were identified in the middle and caudal external lateral subnucleus of the lateral parabrachial nucleus and the dorsal cap of the hypothalamic paraventricular nucleus. These results suggest that enhanced tolerance to HEM following daily exercise may result from an EX-induced reduction in excitation or exaggerated inhibition in central circuits involved in autonomic control.

[Strength training with elastic bands: measure of its effects in cardiac rehabilitation after coronary diseases]

OBJECTIVES

To compare high intensity strength training with weightlifting exercises or with elastic bands.

SETTING

Outpatient unit of cardiac rehabilitation. TYPE: Prospective randomised clinical trial.

POPULATION

Inclusion of coronary patients in phase II after medical or surgical treatment of a myocardiac infarction, without cardiac insufficiency; beta-blockers were accepted.

METHOD

Evaluation of coronary patients at beginning and at the end of a 4 week cardiac rehabilitation program. It included progressive aerobic training according to Karvonen method for all the patients, associated with weightlifting exercises (Koch press) in the control group, or use of elastic bands in the experimental group. Cardiac rate, oxygen consumption at rest and at maximum power were the main criteria with also muscle strength of quadriceps, hamstrings, biceps brachii, latissimus dorsi and triceps brachii, body mass indexes, quality of life with SF-36, anxiety (stay T test) and perceived exertion with the Borg 10-point category-ratio scale, myotendinous injuries (Shaw scale).

RESULTS

Twenty-six coronary patients, all male from 45 to 65 years old, all receiving beta-blockers, were included, 13 in each group. Control and experimental groups were initially similar. At the end of the 4 week program, all the two groups improved significantly their strength and power and there were no differences between the two groups. Perceived exertion was lower in the group using elastic bands and there were no myotendinous lesions.

CONCLUSION

Strength training with elastic bands is a low-cost, attractive, playful technique, proposed to a group of coronary patients, which appears as effective in cardiac rehabilitation as individual weightlifting training.

Design of the training levels comparison trial

The Training Levels Comparison (TLC) trial was a grant-supported, multicenter, randomized, controlled clinical trial designed to determine whether cardiac rehabilitation patients would benefit from supervised exercise for a prolonged period (2 years) and whether subjecting patients to a more vigorous exercise program than currently recommended would provide additional cardiac benefit. If high-intensity exercise does not enhance the cardiac benefit, then physical activity should be limited to low-intensity levels that are safer, easier to implement and more adaptable to a greater number of patients. Patients were randomly assigned to either a low-intensity or high-intensity training program. All patients were to attend three 1-hour supervised exercise sessions per week for a period of 2 years. Attendance at exercise sessions and adherence to assigned treatments were monitored throughout the study. Patients were evaluated for outcome measures at 3, 6, 12, and 24 months. This paper reports the study design and methodology for the TLC trial, and should be useful in providing methodologies to facilitate comparison of data from other studies with different levels of exercise as an intervention.