Submaximal Fitness Tests in Team Sports: A Theoretical Framework for Evaluating Physiological State

Abstract

Team-sports staff often administer non-exhaustive exercise assessments with a view to evaluating current physiological state or fitness–fatigue status, to inform decision-making on athlete management (e.g., future training or recovery). Submaximal Fitness Tests (SMFT) have become prominent in team-sports settings for observing responses to a standardised physical stimulus, likely due to their time-efficient nature, relative ease of administration and physiological rationale. It is evident, however, that many variations of SMFT characteristics, response measures and monitoring purposes exist. The aim of this review is to provide a theoretical framework of SMFT and a detailed summary of their use as indicators of fitness–fatigue status in team-sports. Using a systematic review of the literature, we identified five distinct SMFT protocols characterised in their combinations of exercise regimen (continuous or intermittent) and the progression of exercise intensity (fixed, incremental or variable). Heart rate (HR) derived indices were the most studied outcome measures in SMFT and included exercise (HR exercise) and recovery (HR recovery and vagal-related HR variability) responses. Despite the disparity between studies, these measures appear more relevant to detect positive changes in fitness (i.e., maximal oxygen uptake, intermittent endurance capacity), whereas their role in detecting fatigue associated with variations in ANS function is not yet clear. Psycho-physiological outcome measures such as ratings of perceived exertion were less common SMFT outcome measures in team-sports, but their potential utility when collected alongside objective measures (e.g., HR exercise) has been advocated. Mechanical outcome measures included Global-Positioning-System-derived locomotor variables—such as distance covered, primarily during standardised training drills (e.g., small-sided games) to monitor exercise performance (i.e., fitness status)—or response measures derived from inertial-measurement units to monitor lower limb neuromuscular function and subsequently fatigue status. Whilst there is an emerging interest regarding the utility of these mechanical measures, their measurement properties and underpinning mechanisms are yet to be fully established. Further, it is essential to better understand the methodological aspects of SMFT characteristics in relation to all outcome measures. Herein, we provide a deeper synthesis of the available literature, culminating with best-evidence practical recommendations and directions for future research.