The intermittent work in soccer demands rapid changes in velocity and direction due to the unpredictable events that occur during match play. Hence, the players’ ability to accelerate and decelerate are important indicators for physical performance and load. It is common for elite teams to use inertial measurement units (IMU) to monitor the external training load, of which accelerations and decelerations are considered important variables. Accelerations and decelerations have traditionally been determined relative to a fixed threshold (e.g., >2.0 m·s −2 ). The aim of this study was to examine accelerations and decelerations in several zones (graded from low to high) in two different levels of sensitivity and in three different thresholds for determination of accelerations and decelerations. Thirty-five semi-professional soccer players were monitored with a foot-mounted IMU (Playermaker) during 60 official matches, where number- and meters of accelerations and decelerations were distributed from low to high in sensitivity level 1 (6 zones), sensitivity level 2 (3 zones), and three different thresholds for determination of accelerations and decelerations. Sensitivity and threshold are shown to influence positional differences when acceleration and deceleration values are relatively low but appear to be absent when the values are relatively high. High sensitivity leads to positional differences that are not present for low sensitivity, whereas low sensitivity polarizes differences between zones. For thresholds, the use of acceleration meters leads to greater positional differences compared to number of accelerations. These findings should be considered in the interpretation of the data output and in decisions regarding training load management.
Sandmæl et al. (Wed,) studied this question.