Therefore, the aim of this review is to provide an overview of the current status of research in this field, characterize potential mechanisms by which EIB may impact exercise performance and provide recommendations for future research. 2. METHODS A systematic evaluation of peer-reviewed literature from the PubMed/Medline and EBSCO databases was performed from January 1980 until May 2014 using the search parameter: [(‘exercise’ OR ‘athlete’) AND (‘asthma’ OR ‘bronchoconstriction’ OR ‘hypersensitivity’) AND ‘performance’] (English and humans (Filter), loattrfull text (Filter), not review (Filter) AND has abstract (Filter). This initial search returned 243 papers. Two authors independently reviewed the titles and abstracts of potential studies and subsequently screened full-text study reports for inclusion. After systematically reviewing the literature, 101 duplicate papers were removed, with 132 papers excluded for not including an exercise performance outcome measure (Figure 1). As research addressing the impact of EIB on exercise performance in elite athletes is relatively limited, individuals regularly participating in sport and/or physical activity were considered further. Included studies required subjects to have a previous physician diagnosis of asthma and/or objective evidence of EIB (i.e. ≥10% fall in FEV1) following bronchoprovocation testing. Consequently, ten papers met the initial criteria; six purported to evaluate exercise performance in physically active individuals with asthma and/or EIB [] while four assessed the effects of medication on performance in a comparable population []. These will be considered in more detail in the subsequent sections and form the basis of this review (Table 1). Furthermore, an appraisal of evidence using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) [] approach has been provided (Table 2).
First Author / Year Design Limitations Inconsistency Indirectness Imprecision Other considerations Overall quality Performance Freeman et al. 1990 [] Observational VO2max is a poor predictor of athletic performance Severity of airway obstruction not defined No important inconsistencies Asthmatic subjects recruited rather than individuals with objective evidence of EIB Standard of asthmatic subjects below standard expected for elite or competitive athletes (mean ± SD VO2max: 56 ± 5 mL.kg-1.min-1 ) Low subject numbers No further considerations Very low Freeman et al. 1990 [14] Observational No control group employed VO2max is a poor predictor of athletic performance Severity of airway obstruction not defined No important inconsistencies Asthmatic subjects recruited rather than individuals with objective evidence of EIB Standard of asthmatic ranged from recreational to elite level athlete Low subject numbers No further considerations Very low Sonna et al. 2001 [12] Observational VO2max is a poor predictor of athletic performance Severity of EIB not defined No important inconsistencies Physically active army recruits rather than athletes Standard of asthmatic subjects below standard expected for elite or competitive athletes (mean ± SD VO2max 46 ± 1 mL.kg-1.min-1) No serious imprecision No further considerations Very low
expected for elite or competitive athletes (mean ± SD 43 ± 9 mL.kg-1.min-1) Steinshamn et al. 2002 [17] Randomised control trial No control group employed VO2max is a poor predictor of athletic performance Severity of EIB not defined No important inconsistencies Standard of asthmatic subjects below standard expected for elite or competitive athletes (mean ± SD VO2max: 45 ± 8 mL.kg-1.min-1) No serious imprecision No further considerations Very low Steinshamn et al. 2004 [18] Randomised control trial No control group employed VO2max is a poor predictor of athletic performance Severity of EIB not defined No important inconsistencies Standard of asthmatic subjects below standard expected for elite or competitive athletes (mean ± SD VO2max: 48 ± 11 mL.kg-1.min-1) No serious imprecision No further considerations Very low Koch et al. 2013 [20] Randomised control trial Severity of EIB not defined No important inconsistencies Direct No serious imprecision No further considerations Moderate EIB, Exercise-induced bronchoconstriction; VO2max, maximal oxygen consumption.