The Effect of 400 µg Inhaled Salbutamol on 3 km Time Trial Performance in a Low Humidity Environment

The Objectives of the study were to investigate whether 400 µg inhaled salbutamol influences 3 km running time-trial performance and lung function in eucapnic voluntary hyperpnoea positive (EVH+ve) and negative (EVH-ve) individuals. Fourteen male participants (22.4 ± 1.6yrs; 76.4 ± 8.7kg; 1.80 ± 0.07 m); (7 EVH+ve; 7 EVH-ve) were recruited following written informed consent. All participants undertook an EVH challenge to identify either EVH+ve (?FEV1>10%) or EVH-ve (?FEV1<10%). Participants performed three separate 3 km running time-trials in a low-humidity (20-25%) environment on a non-motorized treadmill, 15 minutes following inhalation of salbutamol (400 µg), placebo (non-active inhalant) or control (no inhalant), in a randomized, single-blind, repeated measures design. Forced vital capacity maneuvers were performed at baseline, 10 minutes post inhalation and post time-trial. Time to complete 3 km and lung function data were analyzed using mixed model repeated measures ANOVA. Significance was assumed at p < 0.05. All EVH+ve participants had FEV1 falls from baseline between 10-25% post-challenge. There was no difference in performance time between trial conditions in EVH+ve (1012.7 ± 129.6s; 1002.4 ± 123.1s; 1015.9 ± 113.0s) (p = 0.774) and EVH-ve (962.1 ± 99.2s; 962.0 ± 76.2s; 950.8 ± 84.9s) (p = 0.401) groups for salbutamol, placebo and control trials, respectively. Exercising heart rate was significantly higher (p = 0.05) in the salbutamol trial (183 ± 8 beats?min-1) compared to control (180 ± 9 beats?min-1) with a trend towards significance (p=0.06) in the placebo trial (179 ± 9 beats?min-1) for the pooled groups, no differences were seen between trials in groups individually. There was an increase in FEV1 in both EVH+ve (4.01 ± 0.8L; 4.26 ± 0.7L; 4.25 ± 0.5L) and EVH-ve (4.81 ± 0.4L; 5.1 ± 0.4L; 5.1 ± 0.5L) groups which was significant post-inhalation (p = 0.01; p = 0.02), but not post-time-trial (p = 0.27; p = 0.06), respectively, following salbutamol. EVH+ve participants did not demonstrate significant falls (>10% from baseline) in FEV1 following any time-trial. Administration of 400µg inhaled salbutamol does not improve 3 km time-trial performance in either mild EVH+ve or EVH–ve individuals despite significantly increased HR and FEV1.