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 not built by the hardest workout you can survive. It 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. In Runked, Fitness carries named levels from Novice to Building, Solid, Strong, Advanced and Elite.
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 Rested to Light, Moderate, Heavy and Intense.
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 productive strain, which is where fitness is actually built. The art is spending most of a training block in productive negative balance, then letting it rise before a race. Runked maps it to six zones:
| Zone | What it means |
|---|---|
| Extreme Strain | Deeply fatigued. Recovery is overdue. |
| Productive | Training hard and adapting. Where fitness grows. |
| Equilibrium | Load and recovery are balanced. |
| Recovery | Fatigue draining, freshness returning. |
| Peaking | Fresh and sharp. Race-ready. |
| Detraining | 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. The widely cited guidance: keep it in a moderate band and injury risk stays low; let it spike above roughly 1.5 and you have loaded far faster than you have adapted, which research associates with elevated 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. |
| Caution | ~1.3–1.5 | Ramping fast. Watch it. |
| High Risk | 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. The classic 10%-a-week rule is a rough version of the same idea.
- Respect Caution. When the ratio climbs into Caution or High Risk, 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 Peaking. That is the taper, in one number.
- Read the trend, not the day. A single hard run should spike fatigue; that is the point. It is the multi-week direction that matters.
How Runked shows it
All four metrics live on the Home Performance section with trend graphs and named levels, so you see not just a number but where it sits and which way it is heading. Alongside them, Performance Shape breaks your running into six systems, Endurance, Threshold, Pacing, Speed, Climbing and Consistency, so you can see which quality your training is building, not just how much load you are carrying.
These metrics update automatically from every synced or tracked run and are part of Runked PRO, which includes a 7-day free trial. Your rank, tracking, leagues and streaks are free.
Train by the numbers
Download Runked, connect your watch, and start the PRO free trial to see your fitness, fatigue and load ratio update after every run.
Download Runked FreeFrequently asked questions
What is a good training load ratio?
Roughly 0.8 to 1.3 is a balanced zone. Climbing toward and above 1.5 marks a load spike linked to higher injury risk; below 0.8 you are resting or detraining.
What is the difference between fitness and fatigue?
Fitness is your chronic load, a roughly 6-week average, the engine you have built. Fatigue is your acute load, a roughly 1-week average, the tiredness you are carrying now. Fitness changes slowly; fatigue moves fast.
What does TSB mean in running?
TSB, or Training Stress Balance, is fitness minus fatigue, also called form or training balance. Positive means fresh and race-ready; negative means productive strain. You build in negative and race best after it rises.
How do I avoid overtraining?
Build gradually so your load ratio stays around 0.8 to 1.3, respect Caution and High Risk warnings, keep most running easy with an 80/20 split, and schedule recovery days and down weeks.