Based on articles:

1️⃣ ‘Should GPS data be normalized for performance and fatigue monitoring in soccer? A theoretical-practical discussion on high-speed running‘

2️⃣ ‘The Need for GPS Data to be Normalized for Performance and Fatigue Monitoring in Soccer: Considerations for Accelerations and Decelerations‘

Authors: Ricardo Pimenta et al
Journal: Frontiers in Sports and Active Living (2025) and Strength & Conditioning Journal (2026)

AI generated summary (ChatGPT)

Across both articles, the central argument is that GPS-derived external load metrics in football — particularly accelerations and decelerations — are often misinterpreted when used as raw, absolute values. While these metrics are widely used to monitor performance and fatigue, their practical value is limited unless they are contextualized, individualized, and methodologically understood.

The first article emphasizes that GPS data only becomes meaningful when normalized to the individual player’s capacity. Identical external loads can impose very different physiological and neuromuscular demands depending on the player’s sprint speed, acceleration ability, strength profile, position, and fatigue state. Therefore, expressing accelerations, decelerations, and high-intensity actions relative to individual maximum capabilities provides a more accurate picture of load and fatigue.

The second article complements this perspective by showing that the measurement of accelerations and decelerations itself is more complex and less robust than commonly assumed. It highlights several methodological issues that influence the reliability and validity of these metrics:

• Acceleration and deceleration counts are highly sensitive to filtering methods, sampling frequency, and manufacturer algorithms.
• Different GPS systems can produce substantially different values for the same movement.
• Short, high-intensity velocity changes — which characterize many decisive football actions — are particularly difficult to measure accurately.
• Threshold-based event counting (e.g., >3 m/s²) is heavily influenced by noise and does not reflect true mechanical or physiological demand.

When these methodological limitations are combined with the lack of individual normalization, practitioners risk drawing incorrect conclusions about:

• Player fatigue
• Training load
• Match demands
• Readiness and recovery
• Return-to-play decisions

Together, the articles argue for a shift in practice:

From counting acceleration and deceleration events as absolute KPIs
→ to interpreting them as individualized, capacity-referenced indicators, understood within the technical limits of the measurement system.

This reframes GPS not as a direct measure of mechanical load, but as a proxy signal that requires intelligent interpretation.

Additional note — recent scientific findings on reliability and validity of GPS acceleration/deceleration metrics

Recent scientific evidence strongly supports the concerns raised in both articles and provides further clarity:

1. Decelerations are the least valid GPS metric
   Studies consistently show that rapid decelerations are poorly captured because they depend on very short time-interval velocity changes, where GPS positional error is magnified.
2. Filtering and firmware determine outcomes
   The same raw movement processed with different smoothing or filtering techniques can change acceleration counts by 20–40%. This means the KPI is partly a product of the software, not just the player’s movement.
3. High accelerations are underestimated, moderate ones overcounted
   Due to sampling limitations, extreme accelerations are often smoothed out, while small fluctuations can be falsely detected as events.
4. Thresholds are not biomechanically meaningful
   Fixed thresholds ignore individual acceleration capacity and do not correspond to true load or neuromuscular stress.
5. Better associations with fatigue occur when individualized
   Research shows stronger relationships between acceleration/deceleration load and neuromuscular fatigue markers (e.g., CMJ, eccentric strength loss) when expressed relative to individual maximum acceleration/deceleration capacity.
6. Consistency within the same device is more important than absolute accuracy
   GPS can be useful for monitoring trends within players over time, but cross-player or cross-device comparisons are problematic.

These findings reinforce the practical takeaway:

Accelerations and decelerations are valuable indicators in football only when
(1) device limitations are understood,
(2) data processing is standardized, and
(3) outputs are normalized to the individual player’s capacity.

This aligns directly with the conceptual message of both articles:

The future of GPS monitoring in football is not more data, but smarter interpretation.