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Table 4 Characteristics of studies included in this meta-analysis that were not included in Trinh et al. [3] systematic review

From: Effects of pseudoephedrine on parameters affecting exercise performance: a meta-analysis

Authors

Title of study

Rationale for inclusion in the meta-analysis

Bright et al. [6]

“Selected cardiac and metabolic responses to pseudoephedrine with exercise”

This paper studied the cardiac and metabolic responses to pseudoephedrine with exercise. As GLU after exercise was measured (a non-significant small decrease was seen), it was included in our study. The relevant performance measure was ‘time to reach 85% of maximum HR’ during submaximal exercise, with no effect being seen. The inclusion criteria of Trinh et al. accounted for any enhancement in sport above baseline such as timing, strength, time to fatigue and/or respiratory enhancement”. Although it did not fit our time trial criteria, it is at least arguable that time to reach 85% of maximum HR fits those of Trinh et al.

Clemons and Crosby [8]

“Cardiopulmonary and subjective effects of a 60 mg dose of pseudoephedrine on graded treadmill exercise”

This evaluated the cardiopulmonary and subjective effects of a 60 mg dose of PSE on graded treadmill running. The RPE and HR data recorded during exercise were included in our meta-analysis. However, the time to exhaustion was not, as it was a graded exercise test rather than a time trial. Despite this, it would seem that time to fatigue on a treadmill would fit well with the Trinh et al. criteria, so it was not clear why they did not discuss this research.

Mouatt [23]

“The physiological effects of pseudoephedrine on endurance cycling”

This study looked at the effects of high dose (2.5 mg/kg 184 mg total) PSE on endurance cycling. This comprehensive randomised controlled trial was included in our analysis as it measured HR, GLU, RPE and TT duration. A difficult study to find owing to it only being published as an MSc. thesis, it is freely and readily available in open access form via standard search engines (Google etc.). Nevertheless, as a research thesis from a well-recognised university (Massey), supervised by a well-published author in the sports and exercise science field (Toby Mündel), we feel it is appropriate to add to our analysis.

Betteridge et al. [20]

“The effect of pseudoephedrine on self-paced endurance cycling performance”

This used a randomised controlled study design to measure HR, GLU, LAC, RPE, and TT duration after a high dose PSE. Heart rate and TT were included in our meta-analysis; however, changes in GLU and LAC values could not be used as they were not reported in sufficient detail. The European Journal of Sports Science is the official journal of the European College of Sports Science, but was not listed in Medline until 2013 so the search strategy of Trinh et al. would not have uncovered it as their search strategy excluded sports and exercise science databases. Trinh et al.’s criteria also did not include citation or reference searches of the final selected papers, which might have rectified this omission as the relevant article was commented on in the discussion of one of the studies [25] that was cited by Trinh et al.

Gradidge et al. [22]

“Effect of a therapeutic dose of pseudoephedrine on swimmers’ performance”

This paper explored the effect of a low dose of PSE on swim performance (TT, RPE, and HR data were included in our analysis). This double blind randomised controlled trial was published in the South African Journal of Sports Medicine, which is absent from the search database used by Trinh et al. [3].

Pritchard-Peschek [24]

“Pseudoephedrine and preexercise feeding: influence on performance”

An apparent inconsistency occurred in the selection of studies from Pritchard-Peschek and collaborators between ourselves and Trinh et al. [3]. Between 2010 and 2014, this group published three randomised controlled trials on PSE and exercise performance. All included TT data and so were included in our meta-analysis. However, Trinh et al., only included the papers published in 2010 [15] and 2014 [25], despite the 2013 paper being published in Medicine and Science in Sports and Exercise and hence readily accessible by Medline. Their 2013 paper [24] had a similar protocol to those in 2010 and 2014 [25], but with the addition of a pre-ingestion meal group. However, this additional group could be easily removed for consistency with the other two studies and so was included in our analysis.

Spence et al. [19]

“A comparison of caffeine versus pseudoephedrine on cycling time-trial performance”

This paper was analysed by Trinh et al., but specifically excluded from their analysis. It compared caffeine and PSE in cycling time trial performance. Trinh et al. excluded the study as they stated it “focuses on differences between effects of caffeine and PSE”. However, in their inclusion criteria, they note that “studies that looked at other substances were included if athletes were not administered both substances simultaneously”. This article outlined three experimental arms (caffeine, PSE, and placebo) in a cross-over study with adequate wash out periods between trials. It is true that the authors focus on the differences between caffeine and PSE in their discussion, but they give full statistics (means, standard deviations, and effect sizes) for a comparison between PSE and placebo. In light of this, by their own criteria, we feel that Trinh et al. should not have excluded this study.