Chronic beta-blockade does not influence muscle power output during high-intensity exercise of short-duration

Effects of beta-blockers on archery performance, body sway and aiming behaviour

Objectives

This study aimed to determine the effect of selective (bisoprolol-5 mg) and non-selective (propranolol-40 mg) beta-blockers on archery performance, body sway and aiming behaviour.

Methods

Fifteen male archers participated in a randomised, double-blind, placebo-controlled, cross-over study and competed four times (control, placebo, selective (bisoprolol) and non-selective (propranolol) beta-blocker trials). Mechanical data related to the changes in the centre of pressure during body sway and aim point fluctuation and when shooting was collected. During the shots, heart rate was recorded continuously.

Results

Results indicated that, in beta-blocker trials, although shooting heart rates were lowered by 12.8% and 8.6%, respectively, for bisoprolol and propranolol, no positive effect of beta-blockers was observed on shooting scores. Also, the use of beta-blockers did not affect shooting behaviour and body sway.

Conclusion

The use of either selective or non-selective single dose beta-blockers had no positive effect on shooting performance in archery during simulated match conditions.

The Effect of Acute Taurine Ingestion on Human Maximal Voluntary Muscle Contraction

PURPOSE

This study aimed to examine the effect of taurine ingestion on maximal voluntary muscle torque and power in trained male athletes with different caffeine habits.

METHODS

Fourteen male athletes 21.8 ± 2.5 yr old were separated into caffeine and noncaffeine consumers to control for the effect of caffeine withdrawal on muscle function. On separate occasions, participants performed four isokinetic or three maximal isometric knee extensions with and without taurine (40 mg·kg body mass) after a double-blind, counterbalanced design. Muscle contractile performances were compared between the first sets as well as between the sets where these variables scored best.

RESULTS

In response to isokinetic contraction, taurine treatment in the noncaffeine consumers resulted in a significant fall in first (-16.1%; P = 0.013) and best peak torque (-5.0%; P = 0.016) as well as in first (-17.7%; P = 0.015) and best power output (-8.0%; P = 0.008). In the caffeine consumers deprived of caffeine, taurine intake improved best power (5.2%; P = 0.045). With respect to the isometric variables, there was a significant decrease in the first (-5.1%; P = 0.002) and best peak torque (-4.3%; P = 0.032) in the noncaffeine group, but no effect in the group of caffeine consumers deprived of caffeine. Taurine ingestion increased blood taurine levels but had no effect on plasma amino acid levels.

CONCLUSIONS

Taurine ingestion is detrimental to maximal voluntary muscle power and both maximal isokinetic and isometric peak torque in noncaffeine consumers, whereas taurine ingestion in caffeine-deprived caffeine consumers improves maximal voluntary muscle power but has no effect on other aspects of contractile performance.

Effects of propranolol and exercise training in children with severe burns

OBJECTIVES

To investigate whether propranolol administration blocks the benefits induced by exercise training in severely burned children.

STUDY DESIGN

Children aged 7-18 years (n = 58) with burns covering ≥30% of the total body surface area were enrolled in this randomized trial during their acute hospital admission. Twenty-seven patients were randomized to receive propranolol, whereas 31 served as untreated controls. Both groups participated in 12 weeks of in-hospital resistance and aerobic exercise training. Muscle strength, lean body mass, and peak oxygen consumption (VO2 peak) were measured before and after exercise training. Paired and unpaired Student t tests were used for within and between group comparisons, and χ(2) tests for nominal data.

RESULTS

Age, length of hospitalization, and total body surface area burned were similar between groups. In both groups, muscle strength, lean body mass, and VO2 peak were significantly greater after exercise training than at baseline. The percent change in VO2 peak was significantly greater in the propranolol group than in the control group (P < .05).

CONCLUSIONS

Exercise-induced enhancements in muscle mass, strength, and VO2 peak are not impaired by propranolol. Moreover, propranolol improves the aerobic response to exercise in massively burned children.

Treatment of hypertension in athletes: an evidence-based review

Hypertension is the most common cardiovascular condition in adults. It is also very common in athletes. When lifestyle changes fail, medications may be needed for the treatment of hypertension. When choosing a drug for antihypertensive therapy, providers should choose an agent that has favorable effects on blood pressure and minimal detrimental hemodynamic change during exercise. Evidence supports that the medications with the most favorable effects are angiotensin-converting enzyme inhibitors, calcium channel blockers, alpha-blockers, and cardiac-selective beta-blockers. The effects of diuretics are less desirable, and nonselective beta-blockers should be a last choice for hypertensive patients who are physically active.

The period between beta-blocker use and physical activity changes training heart rate behavior

The Brazilian Society of Cardiology (SBC) proposes that hypertensive subjects who use beta-blockers and practice physical exercises must have their training heart rate (HR) corrected due to the negative chronotropic effect of this drug. Nevertheless, if the physical activity is performed outside of plasmatic half-life, correction may not be necessary. This study investigated the exercise chronotropic response both inside and outside the beta-blocker plasmatic half-life. Nine subjects in use of atenolol or propranolol, and six controls, carried out three walking sessions in three days according to different schedules: EX2 (two hours after drug administration, at the plasmatic peak); EX11 (eleven hours after drug administration, at the end of plasmatic half-life); and EX23 (twenty-three hours after drug administration, outside the plasmatic half-life. The walking sessions were performed on an ergometric treadmill and HR was monitored by a heart rate monitor. During the exercises, mean HRs were 97.2, 108.4 and 109 for EX2, EX11 and EX23, respectively, with the value for EX2 statistically lower than the others (p<0.05). There were no statistical differences in the control group (p>0.05). The study concludes that the attenuation of the positive chronotropic response which occurs during exercise in subjects using beta-blockers, is less evident when the exercise is performed outside the plasmatic half-life of the drug.

Nebivolol in the management of essential hypertension: a review

Nebivolol is a lipophilic beta1-blocker. It is devoid of intrinsic sympathomimetic or membrane stabilising activity but appears to have nitric oxide-mediated vasodilatory effects. Nebivolol is administered as a racemic mixture of equal proportions of d- and l-enantiomers. The drug does not significantly influence glucose or plasma lipid metabolism and appears to have a protective effect on left ventricular function. At the recommended dosage (5 mg once daily) nebivolol reduces resting diastolic blood pressure as effectively as standard therapeutic dosages of atenolol, metoprolol, lisinopril and nifedipine, as shown in comparative trials. Nebivolol reduced blood pressure significantly more than enalapril 10 mg daily in the short but not the long term, although the enalapril dose may not have been optimal. Nebivolol has an additive effect in combination with hydrochlorothiazide. Standing blood pressure and/or mean 24-hour ambulatory blood pressure is significantly and similarly reduced with nebivolol, atenolol or nifedipine. Nebivolol tended to prevent increases in early morning blood pressure better than nifedipine. Overall response rates to nebivolol therapy (a decrease in sitting/supine diastolic blood pressure to < or = 90 mm Hg or a 10% or > or = 10 mm Hg fall in diastolic blood pressure) ranged from 58 to 81% after 4 to 52 weeks' treatment. In comparative studies, response rates were greater in nebivolol than in enalapril or metoprolol recipients, but not significantly different from those in atenolol or nifedipine recipients. Nebivolol 5 mg once daily is well tolerated in patients with hypertension. Adverse events are infrequent, transient and mild to moderate. Those reported most often include headache, fatigue, paraesthesias and dizziness. Several studies reported no signs of orthostatic hypotension with nebivolol. Comparative trials revealed no significant differences between the frequency and severity of adverse events in patients receiving nebivolol, atenolol, enalapril or placebo; however, the overall incidence of adverse events was greater with nifedipine or metoprolol. Some atenolol or enalapril, but not nebivolol, recipients reported impotence or decreased libido during therapy.

CONCLUSION

Current evidence indicates that nebivolol 5 mg once daily is a well tolerated beta-blocker, which is as effective as once daily atenolol and other classes of antihypertensive agents. It may therefore be recommended as a useful alternative first-line treatment option for the management of patients with mild to moderate uncomplicated essential hypertension.