What Is Running Load?
Running load refers to the total amount of stress placed on your body from running. In scientific literature, this is called training load, defined as the cumulative stress placed on an athlete during training sessions (Windt & Gabbett, 2018).
Importantly, training load is not just how far you ran. It reflects:
- How much work you did
- How intense it was
- How your body responded
- How your training has changed over time
Research consistently shows that injury risk is not caused by training itself, but by how load is progressed and managed (Soligard et al., 2019). When load increases too quickly, the risk of overload injuries such as Achilles tendinopathy, shin splints, or stress fractures rises significantly.
The Two Types of Running Load
To truly understand training stress, we need to look at two components:
- External Load
- Internal Load
This framework is widely used in sports science and athlete monitoring (Coyne et al., 2021).
- External Load: The Work You Do
External load refers to the objective work completed during a run. It answers the question: “What did you physically do?” Common external load metrics include:
- Distance (km or miles)
- Duration (minutes)
- Pace or speed
- Elevation gain
- Step count
- Ground contact metrics (from advanced wearables)
Modern wearable devices allow accurate tracking of these variables through GPS and motion sensors (Areces et al., 2018). For example: A 15 km long run = high external load 8 × 800 m intervals at fast pace = high external load 5 km easy jog = lower external load However, external load alone does not tell us how stressful that session was for you. Two runners can complete the same workout but experience very different physiological stress. That’s where internal load comes in.
2. Internal Load: Your Body’s Response
Internal load measures how your body responded to the external workload. It answers the question: “How hard was that run for you?” Key internal load metrics include:
- Heart rate (average and time in zones)
- Heart rate variability (HRV)
- Rating of Perceived Exertion (RPE)
Research shows that combining internal and external load provides a more accurate picture of training stress than using either alone (Coyne et al., 2021).
Why Load Changes Matter More Than Load Alone
One of the most important discoveries in injury research over the past decade is this: Injuries are strongly linked to sudden spikes in training load. It’s not high training volume alone that causes injuries, it’s rapid increases beyond what your body is prepared for (Windt & Gabbett, 2018).
When load increases too quickly: Muscles fatigue Tendons struggle to adapt Bone remodeling cannot keep up Recovery is insufficient
This creates a mismatch between stress and tissue capacity. The International Olympic Committee emphasizes that proper load management is central to injury prevention (Soligard et al., 2019).
Acute vs Chronic Load
To monitor training safely, researchers distinguish between: Acute Load: Short-term load (typically last 7 days) Chronic Load: Long-term load (rolling 3–6 weeks average)
Chronic load reflects your fitness base or your body’s preparedness while acute load reflects your fatigue levels. When acute load significantly exceeds chronic load, injury risk increases (Windt & Gabbett, 2018). This relationship is often described using workload ratios, although recent research emphasizes careful interpretation and individualized context rather than strict cut-off numbers (Impellizzeri et al., 2020). The key message is simple: Gradual progression protects you. Sudden spikes increase risk.
Which Data Points Are Used to Calculate Running Load?
At LODE, we integrate multiple scientifically supported data points to calculate load in a meaningful way.
External Data
- Distance
- Duration
- Pace
- Training frequency
- Weekly totals
Internal Data
- Average heart rate
- Session intensity
- Perceived exertion (if entered)
These are combined to calculate:
- Session Load
- Weekly Load
- Acute Load
- Chronic Load
- Load trends over time
Instead of simply showing raw numbers, LODE translates these into clear insights so runners understand: Whether their training is progressing safely If they are entering a higher risk period When recovery may be needed Research strongly supports the value of individualized load monitoring for reducing injury risk while supporting progression (Soligard et al., 2019).
Why This Matters for You
As a physiotherapist specializing in running injuries, I see the same pattern repeatedly: The runner wasn’t “too weak.” They weren’t “bad at recovery.” They simply mismanaged their. The body adapts remarkably well when stress is progressive and appropriate. Tendons strengthen. Bones remodel. Muscles become more resilient. But adaptation takes consistency. Having a week off because of work, vacation, sickness, periods, etc. is not a bad thing, it just needs to be managed appropriately. Load monitoring gives you visibility into something that was previously invisible: cumulative stress.
By understanding your running load, you can: Train consistently Avoid unnecessary injury setbacks Improve long-term performance Build durable fitness
The Bottom Line
Running load is the total stress your body experiences from training. It is calculated using both: External load (distance, pace, duration) Internal load (heart rate, perceived effort) The most important factor for injury prevention is not how hard you train, but how wisely you progress.
At LODE, we use validated sports science principles to transform your wearable data into meaningful load insights, helping you train smarter and stay healthy long term. Because performance isn’t built in a single session.
It’s built through consistent, well-managed load over time.
References
Areces, F., et al. (2018). Reliability and validity of GPS devices for measuring running performance. Journal of Sports Sciences, 36(4), 381–388. Coyne, J. O., Gregory Haff, G., Coutts, A. J., et al. (2021). Internal and external load monitoring in team sports: A systematic review. Sports Medicine, 51(7), 1361–1386. Haddad, M., et al. (2019). Session-RPE method for training load monitoring: Validity and practical applications. Frontiers in Neuroscience, 13, 612. Impellizzeri, F. M., et al. (2020). Acute:Chronic workload ratio: Conceptual issues and fundamental pitfalls. International Journal of Sports Physiology and Performance, 15(6), 907–913. Soligard, T., et al. (2019). How much is too much? (Part 1) International Olympic Committee consensus statement on load in sport and risk of injury. British Journal of Sports Medicine, 53(22), 1399–1409. Windt, J., & Gabbett, T. J. (2018). How do training and competition workloads relate to injury? The workload–injury aetiology model. British Journal of Sports Medicine, 52(7), 428–435.
