Tecklenburg 2007.
| Methods | Randomised, double‐blind, trial, cross‐over design | |
| Participants | 8 participants
Mean age: 24.5 (4.8)
Sex: 2 males (25%) All participants were diagnosed with clinically treated mild‐to‐moderate persistent asthma with an FEV1 greater than 70% of predicted and documented EIB (usual diet) as indicated by a drop of greater than 10% in postexercise FEV1 compared with pre‐exercise values. Physician‐diagnosed asthma. All participants had a history of chest tightness, shortness of breath and intermittent wheezing following exercise Baseline lung function: mean FEV1 L (SD) 3.82 (0.37) Baseline lung function: mean % predicted FEV1 (SD): 97.0 (6.1) Inclusion criteria: exercise‐induced bronchoconstriction Participants: university students and the local community Indiana, USA |
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| Interventions | Run‐in: participants were asked to discontinue taking leukotriene receptor antagonists (LTRAs; N = 3 montelukast (Singulairs)) 12 h prior to testing, 10, 13, 14 and 4 days prior to testing to abstain from taking combined inhaled corticosteroids (ICS) and long‐acting b2‐agonists (N = 2, fluticasone propionate (Flovents) and salmeterol (Advairs)) or combined long‐acting b2‐agonists and LTRAs (N = 3 salmeterol (Advairs) and montelukast (Singulairs)). In addition, all participants were asked to refrain from taking caffeine, and to avoid physical activity for 12 h and 24 h, respectively, before exercise testing. Participants were asked to abstain from taking antioxidant supplements other than those given during the course of the study. Participants were advised to avoid foods that were high in vitamin C during the study Intervention: pharmaceutical grade ascorbic acid supplement (1500 mg/day: 3 500 mg capsules)(NOW foods, Bloomingdale, IL) versus a matched (colour/size) placebo (3 capsules/day of sucrose)(NOW foods, Bloomingdale, Illinois) |
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| Outcomes | Pulmonary function (FEV1) pre‐ and postexercise, symptoms, exhaled nitric oxide and urine analysis | |
| Notes | Participants were randomised to active treatment or placebo for 2 weeks. 1‐week wash‐out period. Participants crossed over to the alternative condition for the following 2 weeks Study was funded, in part, by the Gatorade Sports Science Institute |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | Not reported |
| Allocation concealment (selection bias) | Unclear risk | Not reported |
| Blinding of participants and personnel (performance bias) All outcomes | Low risk | Matching placebo manufactured by the same company as the active treatment |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | Matching placebo manufactured by the same company as the active treatment |
| Incomplete outcome data (attrition bias) All outcomes | Unclear risk | No indication of withdrawals |
| Selective reporting (reporting bias) | Unclear risk | No indication of reporting bias |
Abbreviations
ASO: antibodies to streptolysin O BMI: body mass index EIA: exercise‐induced asthma EIB: exercise‐induced bronchoconstriction FEV1: forced expiratory volume in one second FVC: forced vital capacity IgA: immunoglobulin A ITT: intention‐to‐treat MEF: maximal expiratory flow MEF40%(P): maximal expiratory flow at 40% of the vital capacity below total lung capacity on the partial expiratory flow‐volume curve MEFR: mid‐expiratory flow rate mmol: millimoles MMEFR: resting maximal mid‐expiratory flow rate PC20: histamine provocative concentration causing a 20% drop in FEV1 PCV: packed cell volume PEFR: peak expiratory flow rate PD35 sGaw: a 35% reduction in specific airway conductance PMNL: polymorphonuclear leucocyte WBC: white blood cell count