The Difference Between Acute Training Load and Chronic Training Load

When it comes to performance monitoring, two metrics stand above the rest for understanding how your body responds to training: Acute Training Load (ATL) and Chronic Training Load (CTL).

While they sound similar, they measure very different things — and knowing the difference is key to balancing fitness and fatigue effectively.

Acute Training Load (ATL): short-term fatigue

Acute Training Load represents your short-term training stress, typically calculated over the last 7 days.
It shows how much fatigue your body is currently carrying — the immediate impact of recent sessions.

A rising ATL means your recent workload is high. If it climbs too fast, fatigue builds up faster than your body can recover, increasing the risk of overtraining or injury.

Chronic Training Load (CTL): long-term fitness

Chronic Training Load, on the other hand, reflects your long-term adaptation — the average workload your body has sustained over the past 42 days (about six weeks).
A higher CTL indicates that you’ve built a solid base of fitness and resilience from consistent training over time.

In short:

• ATL = fatigue (short-term)
• CTL = fitness (long-term)

The balance between both determines your readiness to perform.

Why the difference matters

When ATL is much higher than CTL, you’re likely overreaching. When CTL is stable and ATL decreases, you’re tapering and recovering.
The key lies in managing both — building CTL progressively while keeping ATL within recoverable limits.

This relationship is often summarized through Training Stress Balance (TSB), which represents the difference between CTL and ATL. A slightly negative TSB indicates productive training; a highly negative one signals too much fatigue.

For a deeper understanding of how CTL evolves and how to measure it accurately, check out our guide on Chronic Training Load.

Tracking ATL and CTL with Vitruve

Using the Vitruve Encoder, you can measure bar velocity and detect neuromuscular fatigue in real time — giving you an inside look at how your acute load is affecting performance within each session.

Meanwhile, tools like the Vitruve AMS allow coaches to visualize both ATL and CTL trends across weeks, helping adjust volume, intensity, and recovery more precisely.

By combining short-term fatigue data with long-term adaptation metrics, you can make smarter training decisions — ensuring every load you apply leads to lasting progress.

More on this topic:

The Importance of Measuring CTL, ATL, TSB, and TSS

In summary

• ATL (Acute Training Load): short-term fatigue, 7-day average
• CTL (Chronic Training Load): long-term fitness, 42-day average
• TSB (Training Stress Balance): the bridge between the two

Understanding and managing the difference between ATL and CTL is the foundation of smart, data-driven training — and the key to consistent performance gains.