Abstract
Background
The low level of evidence regarding injury risk factors motivates new studies analysing biomechanical risk factors (BRF) and their interaction with factors such as fatigue, which serves as the primary modulator of biomechanical response during running. This study aimed to determine if fatigue-related changes in BRF could functionally group healthy recreational runners and to compare biomechanical responses among them. Thirty-nine (N = 39) male recreational runners underwent analysis of lower leg angular kinematics, heart rate, blood lactate levels, and perceived effort before and after a 30-minute exhaustive continuous treadmill running test. Changes in BRF between pre- and post-fatigue conditions were used for clustering via the K-means algorithm.
Results
Three functional groups (FG) were identified, each displaying distinct behaviours in lower limb angular kinematics following fatigue onset. While FG1 and FG2 exhibited similar or compensatory behaviours to maintain their usual running dynamics, FG3 showed more pronounced changes, including increased hip flexion (7.4%) and knee flexion (21%) at touch-down, as well as increased knee flexion at maximal knee flexion (6%) and at the toe-off instant (9%) during the running cycle.
Conclusions
Fatigue-induced alterations in the considered biomechanical risk factors allow for the functional grouping of recreational athletes. Changes in FG3 impact running patterns, altering running economy-related variables, and supposedly increasing injury risk, requiring different training and preventive interventions.