A recent systematic review published in the British Journal of Sports Medicine has revealed significant inconsistencies in how heading impacts are measured in football. The study urges the adoption of wearable technology and standardized metrics to protect players from potential long-term brain injuries.
The review, titled “Quantification of heading in adult football: a systematic review and evidence synthesis,” highlights the need for validated methods to establish clinically relevant thresholds for heading impacts. These should reflect both the frequency and cumulative force of ball-to-head contacts, according to the authors.
An Understudied Aspect of the Sport
Heading is a fundamental skill in football, used in both attacking and defensive situations. However, the physical forces involved remain poorly defined, especially for elite players. While research has been conducted on head impacts in various sports, consistent thresholds for determining whether heading is risky or safe in football are lacking.
Quantifying heading accurately requires understanding key kinematic measures such as linear and rotational accelerations, impact force, frequency, and header type. Technological advancements, like wearable sensors, have enabled researchers to measure these factors. However, many devices still lack sufficient validation for real-world use.
Measurement of Force and Acceleration
Peak linear acceleration (PLA) and peak rotational acceleration (PRA) were the most frequently measured variables, often recorded simultaneously. Adhesive patch sensors, such as the xPatch system, were the most common devices, though more recent studies also used instrumented mouthguards (iMGs) or anthropomorphic test devices (ATDs).
Highest accelerations occurred during goal-kick headers, while lower values were recorded in artificially induced or laboratory scenarios. PLA thresholds for data capture varied widely, complicating cross-study comparisons. Mouthguards were generally the most accurate devices, though even they failed to capture hundreds of headers identified on video in one study.
Recent neuroimaging research demonstrated that frequent heading among amateur soccer players causes microstructural disruption in the orbitofrontal cortex and juxtacortical white matter, regions vulnerable to shear stress from repeated impacts.
Assessment of Heading Frequency and Context
Heading frequency was captured using accelerometers, synchronized video analysis, or subjective questionnaires. Players generally performed more headers in training than in competitive games, except where heading drills were excluded from training. Defenders typically had the highest heading frequency, followed by midfielders and forwards, while elite female strikers executed more contested headers.
Studies explored various contextual factors, including contact location, stance, ball delivery, and type of header. However, definitions and reporting methods were inconsistent. Laboratory-based reconstructions provided controlled insights but lacked realism, whereas field studies better represented game conditions but offered less precision.
Ball properties and neck strength were identified as potential moderators of heading response. Lower ball inflation reduced acceleration values, and balanced neck strength correlated with reduced head acceleration.
Conclusions and Future Directions
This review is the first to comprehensively synthesize how heading is quantified in adult football, revealing major methodological and technological inconsistencies. While acceleration, frequency, and nature are the most reported parameters, no unified framework exists for measuring all four domains together.
Current technologies, especially wearable sensors, often suffer from limited validity and reliability in uncontrolled settings. Gender, playing position, and ball characteristics clearly influence heading dynamics, but findings are fragmented and non-comparable.
Complementary research links repetitive heading in retired male professionals with higher rates of cognitive impairment and self-reported dementia, strengthening the argument for standardized, force-based quantification of heading exposure across all levels of play.
Strengths of the review include a rigorous, systematic approach and inclusion of both laboratory and real-world studies, providing a balanced understanding of accuracy versus realism. Limitations stem from heterogeneity in methods, small and uneven sample sizes, a lack of longitudinal data, and the exclusion of non-English studies.
Future research should establish standardized protocols integrating accelerometry with video verification to accurately quantify ball-to-head impacts. Investigations should include elite players, consider gender and positional demands, and assess moderating variables such as neck strength and ball mechanics.
