Validity and reliability of an instrumented leg-extension machine for measuring isometric muscle strength of the knee extensors.

Context: Isometric muscle strength of knee extensors has been assessed for estimating performance, evaluating progress during physical training, and investigating the relationship between isometric and dynamic/functional performance.

Objective: To assess the validity and reliability of an adapted leg-extension machine for measuring isometric knee extensor force.

Design: Validity (concurrent approach) and reliability (test and test-retest approach) study.

Analysis of the lateral push-off in the freestyle flip turn.

The aim of this study was to examine the contact phase during the lateral push-off in the turn of front crawl swimming to determine which biomechanical variables (maximum normalized peak force, contact time, impulse, angle of knee flexion, and total turn time within 15 m) contribute to the performance of this turn technique. Thirty-four swimmers of state, national, and international competitive standard participated in the study. For data collection, the following equipment was used: an underwater force platform, a 30-Hz VHS video camera, and a MiniDv digital camera within an underwater box.