The terms explanatory and pragmatic trials were first articulated by Schwartz and Lellouch in 1967,1 clarifying their focus on efficacy (causal hypothesis) versus effectiveness (choice of care), respectively.2 Then, in 1986, Flay warned against uncritical adoption of ‘programme causes outcome’ logic that bypasses theory-driven causal testing.3 Subsequently, the PRECIS framework in 20092 operationalised a continuum of explanatory to pragmatic trials. Explanatory trials test effects under ideal conditions, while pragmatic trials assess whether an intervention works in real-world contexts, tolerating variability and lower fidelity with intention-to-treat designs, acknowledging that few trials are purely explanatory or pragmatic.4 Early-stage research should prioritise explanatory trials to establish mechanistic causal inference. By maximising control first, these trials provide the plausible range of effects that may be observed in later implementation-focused studies.4 Yet anterior cruciate ligament (ACL) injury prevention research often bypasses explanatory trials, relying on pragmatic, multicomponent interventions without testing which elements (or exercises) are necessary or sufficient. Generalisation without explanatory inference is a gamble, not a scientific conclusion.

Generally, training programmes may reduce ACL injuries in certain athletic cohorts, particularly younger or less-trained athletes.5 However, these interventions are often modified to improve adherence to a multicomponent programme6 before the effects of single-component programmes (ie, strength, proprioceptive) are examined to determine which elements are most important to include.7 We argue that prioritising theory-grounded, evidence-based strategies is essential for athlete health and avoiding research waste.3 While bodyweight strength exercises, running, proprioceptive and jumping tasks benefit younger athletes, these are unlikely to meet the progressive overload thresholds required for musculoskeletal adaptation in athletes with greater strength and conditioning training experience. The absence of progressive overload and the law of diminishing returns inherently limit improvements in the strength, balance, jumping and landing ability these programmes purport to develop.8 9

The focus on adherence or implementation may have unintentionally deprioritised rigorous testing of efficacy and mechanistic underpinnings. This led to extensive adoption of adapted low-dose exercise prescriptions that are so embedded in ‘the way we do things’, they become difficult to replace or evolve.3 Subsequently, these widely disseminated programmes often become default solutions. We present a principles-based critique of continued efforts to use warm-up protocols as training programmes for long-term ACL injury prevention. We begin by addressing our central concern: the interpretation and extrapolation of evidence drawn largely from youth and amateur populations, despite limited mechanistic evidence to justify broader claims of benefit. We then examine principles of training and outline priorities for future causal research, emphasising that stronger evidence is needed before programme benefits can be confidently extended.