The Alfred Step Test Exercise Protocol (A-STEP), for Adults With Cystic Fibrosis.

"Study A) Study A) Development of new exercise test protocol and Observational Feasibility/Safety Study (no comparator).~Feasibility/safety of a newly designed, incremental, maximal, standardised step test in adults with Cystic Fibrosis."

Study B) Validation Study (random allocation of test order). Validity of an incremental, maximal, standardised incremental step test with breath-by-breath gas analysis using portable metabolic measurement equipment against CPET.

"Study B) Validation study (random allocation of test order) Gold standard CPET. An incremental, maximal standardised cycle ergometer exercise test (performed as per published protocol) using portable metabolic measurement equipment."