Feasibility and reliability of measuring strength, sprint power, and aerobic capacity in athletes and non-athletes with cerebral palsy

Aim: The aim of this study was to analyse the feasibility and reliability of the tests used to determine muscle strength, sprint power, and aerobic capacity in athletes and non-athletes with cerebral palsy (CP).

Methods: Twenty individuals with spastic CP (four females, 16 males; age range 18-49y; Gross Motor Function Classification System level I, n=15; II, n=5; unilateral CP, n=10; bilateral CP, n=10; athletes, n=12; non-athletes, n=8) participated in the study. Isometric and isokinetic knee flexor and extensor strength, sprint power, and aerobic capacity were determined, using, respectively an isokinetic dynamometer, a Wingate cycling test, and a graded maximal bicycle exercise test, on three occasions. Intraclass correlation coefficients (ICC), standard error of measurements, and smallest detectable differences (SDD) were calculated.

Results: The feasibility of the isometric strength test, Wingate test, and graded exercise test was good; the isokinetic strength test was difficult to perform for five participants. The strength parameters showed moderate to good ICCs (isometric, 0.74-0.94; isokinetic, 0.88-0.93) but high SDDs (isometric, 25-45%; isokinetic, 30-45%). Sprint power (ICC 0.98; SDD 24%) and aerobic capacity (ICC 0.98-0.99; SDD 16-21%) showed good ICCs and moderate SDDs.

Interpretation: All tests, except for the isokinetic strength test, seemed to be feasible for almost all participants. All tests are suitable for evaluating changes in a group; however, only large improvements (16-45%) can be detected when monitoring individual changes.