Mechanical work derived using markerless motion capture provides a valid indication of acute neuromuscular fatigue in tennis.

Whilst workload monitoring is key to managing performance and injury risk, effective strategies in tennis are not well-established. Mechanical work (external and internal components), measurable through markerless motion capture approaches, provides a novel way to quantify workload. To determine the suitability of this approach, this study investigated the association between mechanical work and acute neuromuscular fatigue. Fifteen tennis players completed a tennis-specific on-court fatiguing protocol interspersed with sprint tests. Peak sprint velocity (measure of acute neuromuscular fatigue) was correlated against mechanical work for each player. Pooled correlations (accounting for inter-individual differences) for total (external + internal) and external work, as well as external work estimated from centre of mass (CoM) proxies (pelvis and bounding box methods) were comparable, with values of -0.93 to -0.92. Although the calculated work done varied greatly between methods (~40% for pelvis method), these differences were systematic. All methods therefore appeared to provide an indication of individual players' workload (acute neuromuscular fatigue), despite the absolute values of the CoM proxy methods being inaccurate. Therefore, we recommend using the approximations only when monitoring an individual player in similar contexts. These findings present the markerless approach as a promising tool that could be implemented for non-invasive, on-court workload monitoring in tennis.