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

Team-sports staff often administer non-exhaustive exercise assessments with a view to evaluating physiological state, 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 scoping review is to provide a theoretical framework of SMFT and a detailed summary of their use as proxy indicators of training effects in team-sports. Using a review of the literature stemming from a systematic search strategy, 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 (exercise HR) and recovery (HR recovery and vagal-related HR variability) responses. Despite the disparity between studies, these measures appear more relevant to detect positive chronic endurance-oriented training effects, whereas their role in detecting negative transient effects associated with variations in autonomic nervous system function is not yet clear. Subjective outcome measures such as ratings of perceived exertion were less common in team-sports, but their potential utility when collected alongside objective measures (e.g., exercise HR) has been advocated. Mechanical outcome measures either included Global-Positioning-System-derived locomotor outputs such as distance covered, primarily during standardised training drills (e.g., small-sided games) to monitor exercise performance, or responses derived from inertial-measurement units to make inferences about lower limb neuromuscular function. 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. Herein, we provide a deeper synthesis of the available literature, culminating with evidence-based practical recommendations and directions for future research.