CLINICS 2012;67(6):615-621 CLINICAL SCIENCE DOI:10.6061/clinics/2012(06)12 The effect of acute magnesium loading on the maximal exercise performance of stable chronic obstructive pulmonary disease patients Ange´ lica Florı´pedes do Amaral, Lourenc¸o Gallo Jr., He´ lio Vannucchi, Ju´ lio Ce´ sar Cresceˆ ncio, Elcio Oliveira Vianna, Jose´ Antoˆ nio Baddini Martinez Universidade de Sa˜ o Paulo, Medical School of Ribeir a˜o Preto, Internal Medicine Department, Ribeira˜ o Preto/SP, Brazil. OBJECTIVE: The potential influence of magnesium on exercise performance is a subject of increasing interest. Magnesium has been shown to have bronchodilatatory properties in asthma and chronic obstructive pulmonary disease patients. The aim of this study was to investigate the effects of acute magnesium IV loading on the aerobic exercise performance of stable chronic obstructive pulmonary disease patients. METHODS: Twenty male chronic obstructive pulmonary disease patients (66.2¡8.3 years old, FEV1: 49.3¡19.8%) received an IV infusion of 2 g of either magnesium sulfate or saline on two randomly assigned occasions approximately two days apart. Spirometry was performed both before and 45 minutes after the infusions. A symptom-limited incremental maximal cardiopulmonary test was performed on a cycle ergometer at approximately 100 minutes after the end of the infusion. ClinicalTrials.gov: NCT00500864 RESULTS: Magnesium infusion was associated with significant reductions in the functional residual capacity (-0.41 l) and residual volume (-0.47 l), the mean arterial blood pressure (-5.6 mmHg) and the cardiac double product (- 734.8 mmHg.bpm) at rest. Magnesium treatment led to significant increases in the maximal load reached (+8 w) and the respiratory exchange ratio (0.06) at peak exercise. The subgroup of patients who showed increases in the work load equal to or greater than 5 w also exhibited significantly greater improvements in inspiratory capacity (0.29 l). CONCLUSIONS: The acute IV loading of magnesium promotes a reduction in static lung hyperinflation and improves the exercise performance in stable chronic obstructive pulmonary disease patients. Improvements in respiratory mechanics appear to be responsible for the latter finding. KEYWORDS: Pulmonary Disease; Chronic Obstructive; Magnesium; Cardiopulmonary Exercise Test; Spirometry; Blood Pressure; Circulatory and Respiratory Physiology. Amaral AF, Gallo Jr L, Vannucchi H, Cresceˆ ncio JC, Vianna EO, Jose´ Martinez AB. The effect of acute magnesium loading on the maximal exercise performance of stable chronic obstructive pulmonary disease patients. Clinics. 2012;67(6):615-621. Received for publication on March 9, 2012; First review completed March 12, 2012; Accepted for publication on March 12, 2012 E-mail: baddini@fmrp.usp.br Tel.: 55 16 36022531 INTRODUCTION Magnesium (Mg) is involved in a great number of enzymatic reactions and may be involved in several biological processes, such as energy production, glycogen catabolism, control of neuronal activity, cardiac electric conduction, muscular contraction, vasomotor tone, and blood pressure (1,2). An increased interest in the potential influence of Mg on exercise performance has been observed in recent years (2-6). Nutritional status is an important determinant of exercise performance in patients with chronic respiratory diseases Copyright 2012 CLINICS – This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non- commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. No potential conflict of interest was reported. (7). A potential role for Mg supplementation in regard to physical performance may be pronounced in these patients. Dietary Mg intake has been shown to be related to lung function, airway reactivity, and respiratory symptoms (8,9). Some studies have suggested that patients with chronic obstructive pulmonary disease (COPD) may exhibit decreased body levels of Mg (10-12). This abnormality may be related to the chronic use of medicines such as steroids and bronchodilators or the presence of food in- gestion disorders. Inhaled Mg and IV Mg administration have been shown to promote bronchodilation and to improve lung function in asthmatic subjects (13-15). The IV administration of Mg during episodes of acute exacer- bation of COPD in patients treated with albuterol leads to improvements in the peak flow (12). In another study, also involving COPD subjects with exacerbations, the effects of IV Mg were evident only after albuterol inhalation (16). In a previous study, we have investigated the acute effects of the IV loading of Mg on the pulmonary function 615