Training load: when to push, when to rest
Training load quantifies the stress your running puts on your body. Balancing chronic fitness against acute fatigue tells you when to push and when to rest. Four numbers do the work: Fitness (what you have built), Fatigue (what you are carrying), Training Balance (fitness minus fatigue) and Load Ratio (recent load versus long-term load). Read together, they turn guesswork into a plan.
Fitness is built by the largest load you can absorb and recover from, repeatedly. These four metrics make that invisible balance visible.
Fitness (chronic training load)
Fitness is your chronic training load, a roughly six-week weighted average of the training stress you have accumulated. It is the durable engine you have built, and it changes slowly. A single great run barely moves it; six weeks of consistent running moves it a lot. In sports science this is often called CTL, the chronic side of the fitness-fatigue systems model published by Calvert, Banister and colleagues in 1976. In Runked, Fitness carries named levels from Starting to Building, Solid, Strong, Advanced and Exceptional.
Fatigue (acute training load)
Fatigue is your acute training load, a roughly one-week average of recent training stress. It is the tiredness you are carrying right now, and it rises and falls fast, spiking after a hard week and draining away over a few easy days. This is often called ATL. Runked labels it from Fresh to Light, Moderate, High and Very High.
Training Balance (fitness minus fatigue)
Training Balance is fitness minus fatigue, the trade-off between fresh and fatigued, sometimes called form or TSB. A positive balance means you are fresher than your fitness, primed to race. A negative balance means you are carrying strain from recent training. Most of a training block sits in Runked's Building zone, a negative balance that later rises before a race. Runked maps it to six zones:
| Zone | What it means |
|---|---|
| Overloaded | Deeply fatigued. Recovery is overdue. |
| Building | Training hard and adapting. Where fitness grows. |
| Balanced | Load and recovery are level. |
| Fresh | Fatigue draining, freshness returning. |
| Race Ready | Fresh and sharp. |
| Very Rested | Too fresh for too long; fitness slipping. |
Load Ratio (acute:chronic workload)
Load Ratio is your acute load divided by your chronic load, the acute:chronic workload ratio or ACWR. It measures how big a jump your recent training is relative to what your body is used to. Gabbett's 2016 review in the British Journal of Sports Medicine calls a ratio of about 0.8 to 1.3 the training's "sweet spot" and a ratio above 1.5 the "danger zone," where the athlete has loaded faster than they have adapted and the review links the pattern to higher injury risk. Runked sorts it into four zones:
| Zone | Roughly | Read |
|---|---|---|
| Low | below ~0.8 | Resting or detraining. |
| Balanced | ~0.8–1.3 | Sustainable building. |
| Rising Fast | ~1.3–1.5 | Ramping fast. Watch it. |
| Too High | above ~1.5 | Sharp spike. Back off. |
How runners use these numbers
- Build gradually. Add load in small steps so your Load Ratio stays in the Balanced zone.
- Respect the warning. When the ratio climbs into Rising Fast or Too High, hold volume flat or take a down week before pushing again.
- Peak for the race. In the final week or two, cut fatigue faster than fitness so Training Balance rises into Race Ready.
- Track the multi-week direction. A single hard run should spike fatigue; that is the point, and it fades within days without changing the underlying trend.
When these four numbers stay flat for weeks while the training still feels hard, the signs of overtraining guide covers what the ECSS/ACSM consensus statement lists and when to see a doctor.
How Runked shows it
All four metrics live on the Home Performance section with trend graphs and named levels, so you see the number, where it sits, and which way it is heading. Alongside them, Runner DNA breaks your running into six systems, Endurance, Threshold, Pacing, Speed, Climbing and Consistency, showing which quality your training is building alongside how much load you are carrying.
These metrics update automatically from every synced or tracked run. One Runked PRO subscription covers tracking, leagues and streaks. The running rank depends only on your own running, regardless of experience: compare this month to your own last month, not to another runner's training load.
Train by the numbers
Download Runked, connect your watch, and start the yearly plan's 7-day free trial to see your fitness, fatigue and load ratio update after every run.
Download on App StoreFrequently asked questions
What is a good training load ratio?
The acute:chronic workload ratio (ACWR) compares your recent 7-day load to your longer-term roughly 6-week load. Gabbett's 2016 review in the British Journal of Sports Medicine calls a ratio between about 0.8 and 1.3 the training's sweet spot and a ratio above 1.5 the danger zone for injury risk. Below about 0.8 you are detraining or resting.
What is the difference between fitness and fatigue?
Fitness is your chronic training load, a roughly 6-week weighted average of the work you have put in, representing the durable engine you have built. Fatigue is your acute training load, a roughly 1-week average, representing the tiredness you are carrying right now. Fitness changes slowly; fatigue rises and falls fast. In Runked, both update automatically from every synced or tracked run, as part of Runked PRO, whose yearly plan starts with a 7-day free trial.
What does TSB mean in running?
TSB, or Training Stress Balance, is your fitness minus your fatigue, sometimes called form or training balance. A positive balance means you are fresh and race-ready; a negative balance means you are carrying strain from a hard training block.
How do I avoid overtraining?
Build load gradually so your acute:chronic ratio stays roughly between 0.8 and 1.3, respect Rising Fast and Too High warnings by backing off, keep most running easy in an 80/20 split, and schedule recovery days and down weeks. Watch for a training balance that stays deeply negative for weeks; that pattern points to accumulated fatigue outpacing fitness gains.