Summary
The aim of the study was to test the hypothesis that a 24-week exercise intervention improves asthma control in adults.
Adults with mild or moderate asthma were randomly assigned to either the exercise intervention group (IG) or the reference group (RG). Participants in IG received an individualized exercising program, including aerobic exercise at least three times a week for ≥30 minutes, muscle training, and stretching.
The primary outcome was asthma control, measured by Asthma Control Test (ACT), asthma-related symptoms, and peak expiratory flow (PEF) variability. We estimated the risk (i.e. probability) of improvement in asthma control and the risk difference (RD) between IG and RG.
Of 131 subjects (67 IG/64 RG) entered, 105 subjects (51/54) completed the trial (80%), and 89 (44/45) were analysed (68%). The ACT became better among 26 (62%) participants in IG and among 17 (39%) participants in RG. The effect of intervention on improving asthma control was 23% (RD = 0.23, 95% CI 0.027–0.438; P = 0.0320). The intervention also reduced shortness of breath by 30.1% (RD = 0.301, 95% CI 0.109–0.492; P = 0.003). The change in PEF variability was similar in both groups.
Regular exercise improves asthma control measured by the ACT, while has little effect on PEF variability.

Relevance
This study offers a detailed exercise intervention which was shown to be effective in asthma control among adults, especially within younger, women, and never smokers stratum.
Participants were instructed to carry out aerobic exercise at least three times a week for at least 30 minutes. They received individualized advice on different forms of aerobic exercising. Suggested forms of aerobic exercising included rapid walking, jogging, running, Nordic walking, skiing, cycling, team games, dancing, and exercising in the gym using for example weights, rowing machine or cross-trainer. The targeted heart-rate level was 70–80% of the maximal heart rate, which was measured in spiroergometry at baseline. The participants were instructed to perform interval training, if the exercise caused asthma symptoms. They were also instructed to moderate their training during cold weather (temperature below −10 °C). They were advised to avoid strenuous exercising during high levels of pollen to which they were sensitized. In addition, they were instructed to perform muscle exercises to strengthen abdominal, back, upper body and thigh muscles at least twice a week. Further, the participants received instructions for stretching before and after aerobic and muscle exercises. The instructions were based on the Finnish National Guidelines on Exercising that aim at sufficient amount of aerobic exercise and comprehensive muscular training.