Background: People with asthma may have skeletal muscle dysfunction but data on core function in severe asthma (SA) are limited.

Aims: To compare core function between people with SA and healthy controls (HC) and to investigate its association with dyspnoea impact and dysfunctional breathing (DB).

Methods: Adults with a doctor diagnosis of SA and HC undertook a core function assessment that consisted of 3 endurance tests: the Πstatic sit-up, the Biering-Sorensen, and the side bridge. Dyspnoea impact was assessed by the modified Medical Research Council (mMRC) score and the modified Borg dyspnoea scale. Nijmegen questionnaire was used to assess DB.

Results: 140 people with SA (38% male, age median[Q1-Q3] 59[44-68] years, BMI 30[26-37]kg/m², FEV₁ 2.09[1.57-2.82]L, 6MWD of 462[380-527]m, ACQ score 2.3 [1.5-3.0]) were compared to 67 HC (46% male, age 55[34-65] years, BMI 25[22-28] kg/m², FEV₁ 3.02[2.55-3.57]L, 6MWD of 613[567-656]m). There was no difference between SA and HC in the Œ static sit-up (30[18-56] vs 38[16-62]s; p=0.09); however, participants with SA had worse performance in the Biering-Sorensen (43[25-84] vs 100[65-141]s; P<0.001) and in the left and right side bridge test (20[11-42] vs 45[33-66]s and 31[12-40] vs 48[29-92]s; p<0.001) compared to HC. The mMRC (2[1-3] vs 0[0-0]), Borg scale (1[0-2] vs 0[0-0]) and Nijmegen score (22[13-30] vs 6[3-11]) were greater in SA compared to HC (p<0.001). The core function tests correlated with mMRC, Borg scale and Nijmegen score (-0.51>r>-0.19, p?0.03) across both groups.

Conclusion: Adults with SA have worse core function compared to their control counterparts. As core function decreases the symptoms of dyspnoea and DB increase.