How many headers are too many before football crosses the safety line?

By Priyanjana Pramanik, MSc.Reviewed by Susha Cheriyedath, M.Sc.Oct 23 2025

A systematic review finds major inconsistencies in how heading impacts are measured, urging the use of wearable technology and standardized metrics to safeguard players from potential long-term brain injury.

Systematic review: Quantification of heading in adult football: a systematic review and evidence synthesis. Image Credit: KOTOIMAGES / Shutterstock

In a recent systematic review published in the British Journal of Sports Medicine, researchers examined how heading in adult soccer is quantified and assessed the influence of various factors on these measurements. Their findings highlight the need for standardized and validated methods. The authors conclude that these should be based on data from wearable technology and video analysis to establish valid, clinically relevant thresholds for heading impacts that reflect both the frequency and cumulative force of ball-to-head contacts.

An Understudied Aspect of the Sport

Heading is a fundamental skill in football, used in both attacking and defensive situations, yet the physical forces involved remain poorly defined for elite players. Although research has investigated 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. These include linear and rotational accelerations, impact force, frequency, and header type. Technological advancements, such as wearable sensors, have enabled researchers to measure these factors. However, many devices still lack sufficient validation for real-world use.

Previous reviews have provided only partial overviews and have not considered how moderating variables, including ball properties, playing position, approach, and gender, influence heading outcomes.

Moreover, no comprehensive review has synthesized how heading is quantified across different environments, ranging from competitive games to laboratory setups and training sessions.

To address this gap, the current systematic review aimed to evaluate all available evidence on the measurement of acceleration, force, nature, and frequency of heading in adult football, and to identify how contextual factors modify these parameters.

The findings, drawn from 32 studies that met rigorous screening criteria, are intended to guide future research toward developing standardized, reliable, and ecologically valid measurement techniques for heading in football.

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 (typically ≥10 g, sometimes as low as 5–8 g), and inconsistent sampling rates and filters complicated 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. This aligns with recent neuroimaging research in JAMA Network Open (Song et al., 2025) and Neurology (DeMessie et al., 2025), which 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. These alterations were associated with poorer memory and cognitive performance, underscoring the need for validated, sensor-based impact thresholds.

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. Data inconsistencies arose from diverse methodologies, unverified events, and limited contextual detail, such as tactical settings or match halves.

Studies explored various contextual factors, including contact location, stance, ball delivery, and type of header, but 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. Few studies integrated all parameters (nature, force, acceleration, and frequency) simultaneously.

Ball properties (namely, inflation, speed, and pressure) 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. Additional evidence from Frontiers in Sports and Active Living (Palmer et al., 2025) shows that female players exposed to realistic match-play heading exhibited measurable changes in fine motor control, even when gross balance was unaffected. These findings underscore the review’s call to consider sex-based physiological responses when setting safe exposure limits.

However, inconsistencies in study design and a lack of elite-level data prevented firm conclusions.

Most human studies were of moderate quality, with strong control for confounders but weaknesses in design and statistical reporting. Model-based studies scored higher methodologically yet lacked ecological validity.

Conclusions

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, and none of the studies investigating acceleration or force were representative of an elite adult football population. Gender, playing position, and ball characteristics clearly influence heading dynamics, but findings are fragmented and non-comparable.

Complementary research from JAMA Network Open (Espahbodi et al., 2023) links repetitive heading in retired male professionals with higher rates of cognitive impairment and self-reported dementia, while pathology data from Nature Communications (Daneshvar et al., 2023) show that the cumulative force of head impacts, rather than the number of concussions, best predicts chronic traumatic encephalopathy (CTE). Together, these studies strengthen 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.

Developing reliable thresholds for heading exposure is essential for monitoring safety, informing training guidelines, and advancing understanding of potential long-term neurological risks such as cognitive decline and CTE in professional football.