Análise das variáveis cinemáticas espaço-temporais frequência e amplitude de passos, na pista e na esteira ergométrica

Abstract

Introduction - A treadmill is an appropriate instrument to provide a standardized and reliable performance task. Although it had been used mostly for research, currently it has been widely used at gyms and has gained popularity at endurance training. The distance between strides during the walk or the run is called stride length, and the number of strides during a certain period of time is the frequency. This way, the speed is determined by stride length times stride frequency. The kinematics is a biomechanics subject that allows to measure the position, displacement, speed, and acceleration of the body or its segments. The kinematic major focus is to describe how the body moves. The kinematic parameters for speed analysis include stride and pace frequency and length as well as all space-time variables and all their variations. The researches which tried to draw a comparison between track and treadmill run are inconsistent nor even recent. This inconsistency seems to be related to the differences among methodology, endurance capacity of volunteers, speed at test protocols, and methods to estimate this speed in each study. Objective - To analyse if stride length and stride frequency behave similarly by comparing a track and a treadmill run. And if there are differences, the purpose is to check if they are unchangeable or if the subject is able to choose which frequency and amplitude they want to run and also to verify if they are randomized or pre-determinate by some peculiarity of the sample. Methods - 22 runners participated of this study with VO2max 59,8 ± 5,53, MAS 17,4 ± 1,59, age 33,7 ± 10,84, body mass 69,18 ± 9,31. Three tests were conducted in this order: maximal test, treadmill and track tests for all volunteers. Results - For a 100% and 120% MAS a decreased value of stride length and an increased value of stride frequency were found at treadmill compared to track. We believe runners prefer to run this way, because they run differently when they receive verbal stimulus to change the technique. We can also predict that well-trained runners manage to run at lower differences between treadmill and track, specially at 120 % of MAS. Conclusion - For stride length and stride frequency, no difference was found at 60% and 80% of MAS, but at 100% and 120%, stride length is higher and stride frequency lower at treadmill compared to track at same speed. These differences are not unchangeable; runners are capable of choosing which combination of stride length and stride frequency they prefer to run. Besides, the differences may be determined, mostly at 120% of MAS by the fitness level of the runners.