Training Load & Performance Management
Quantifying Stress, Tracking Fitness, Optimizing Performance
Understanding Training Load
Training load quantification answers the critical question: How hard was that workout? Not just distance or time, but the true physiological stress imposed on your body.
The Training Stress Score (TSS) system, developed by Dr. Andrew Coggan, provides a standardized method to quantify workout intensity and duration into a single number. For swimming, we use Swim Training Stress Score (sTSS) with a crucial modification that accounts for water's unique resistance properties.
The TSS Standard
One hour at your functional threshold pace (CSS) = 100 TSS
This standardization allows comparison across workouts, weeks, and training cycles. A 30-minute threshold swim = ~50 TSS. A 2-hour threshold swim = ~200 TSS.
Swim Training Stress Score (sTSS)
The Formula
Where Intensity Factor (IF) is:
And Normalized Swim Speed (NSS) is:
⚡ The Cubic Factor (IF³)
Key Innovation: Swimming uses IF³ while cycling/running use IF². This reflects water's physics—resistance increases exponentially with speed.
Going 10% faster in water requires ~33% more power. The cubic factor accurately weights this increased physiological cost.
Worked Example
Swimmer Profile:
- CSS: 1:33/100m = 93 seconds/100m
- FTP: 64.5 m/min (100m / 1.55min)
Workout Data:
- Total Distance: 3000m
- Moving Time: 55:00 (3300 seconds)
- Rest Time: 10:00 (not counted)
Step 1: Calculate NSS
NSS = 54.5 m/min
Step 2: Calculate IF
IF = 0.845
Step 3: Calculate sTSS
sTSS = 0.603 × 0.917 × 100
sTSS = 55.3
sTSS Intensity Guidelines
| sTSS Range | Intensity Level | Description | Example Workouts |
|---|---|---|---|
| < 50 | Easy Recovery | Light swimming, technique focus, active rest | 30-45min recovery swim, drill sets |
| 50-100 | Moderate Training | Typical daily training volume | 60-90min aerobic endurance, mixed zones |
| 100-200 | Hard Training | Quality sessions with threshold/VO₂ work | 90-120min with CSS intervals, race pace sets |
| 200-300 | Very Hard | Race simulation, very high intensity blocks | 2-3hr sessions, time trials, max effort sets |
| > 300 | Extreme | Race day, ultra-distance events | Competition, Ironman swims, marathon swimming |
📊 Weekly TSS Targets by Level
- Beginners: 200-400 TSS/week
- Intermediate: 400-700 TSS/week
- Advanced/Elite: 700-1000+ TSS/week
These accumulate toward your Chronic Training Load (CTL).
Performance Management Chart (PMC)
The PMC visualizes three interconnected metrics that tell the complete story of your training: fitness, fatigue, and form.
CTL - Chronic Training Load
42-day exponentially weighted average of daily TSS. Represents long-term aerobic fitness and training adaptation.
ATL - Acute Training Load
7-day exponentially weighted average of daily TSS. Captures recent training stress and accumulated fatigue.
TSB - Training Stress Balance
Difference between yesterday's fitness and fatigue. Indicates readiness to perform or need to rest.
Understanding CTL: Your Fitness Metric
What CTL Represents
CTL quantifies the training workload your body has adapted to over the past 6 weeks. A higher CTL means:
- Greater aerobic capacity and endurance
- Ability to handle more training volume
- Improved muscular and metabolic adaptations
- Higher sustainable performance
Time Constant: 42 Days
CTL has a half-life of ~14.7 days. After 42 days, approximately 36.8% (1/e) of a single workout's impact remains.
This slow decay means fitness builds gradually but also fades slowly—protecting against detraining during short breaks.
Typical CTL Values
Building base fitness, 3-4 swims/week
Consistent training, 4-5 swims/week
High volume, 5-6 swims/week, doubles
Professional training load, 8-12 sessions/week
- Beginners: +3-5 CTL per week
- Intermediate: +5-7 CTL per week
- Advanced: +7-10 CTL per week
Exceeding these rates significantly increases injury and burnout risk.
Understanding ATL: Your Fatigue Metric
ATL tracks short-term training stress—the fatigue accumulated in the past week. It rises quickly after hard training and drops quickly during rest.
ATL Dynamics
- Fast Response: 7-day time constant (half-life ~2.4 days)
- Spiky Pattern: Jumps after hard sessions, drops during recovery
- Recovery Indicator: Falling ATL = dissipating fatigue
- Overtraining Warning: Chronically elevated ATL suggests inadequate recovery
🔬 The Fitness-Fatigue Model
Every training session produces two effects:
- Fitness stimulus (slow-building, long-lasting)
- Fatigue (fast-building, fast-dissipating)
Performance = Fitness - Fatigue. The PMC visualizes this model, enabling scientific training periodization.
At Steady State
When training load is consistent week-to-week, CTL and ATL converge:
Example: 500 TSS/week consistently
CTL approaches ~71
ATL approaches ~71
TSB approaches 0
Interpretation: Fitness and fatigue are balanced. No accumulating deficit or surplus.
During Build Phases
When increasing training load:
ATL rises faster than CTL due to shorter time constant. TSB becomes negative (fatigue > fitness). This is normal and productive—you're applying overload to stimulate adaptation.
During Taper
When reducing training load:
ATL drops faster than CTL. TSB becomes positive (fitness > fatigue). This is the goal—arrive at race day fresh while retaining fitness.
Understanding TSB: Your Form/Readiness Metric
TSB is the difference between yesterday's fitness (CTL) and yesterday's fatigue (ATL). It indicates whether you're fresh or fatigued, ready to race or in need of recovery.
TSB Interpretation Guide
| TSB Range | Status | Interpretation | Recommended Action |
|---|---|---|---|
| < -30 | Overload Risk | Extreme fatigue. Potential overtraining. | Immediate recovery needed. Reduce volume 50%+. |
| -20 to -30 | Optimal Training Block | Productive overload. Building fitness. | Continue plan. Monitor for signs of excessive fatigue. |
| -10 to -20 | Moderate Load | Standard training accumulation. | Normal training. Can handle quality sessions. |
| -10 to +15 | Transition/Maintenance | Balanced state. Light fatigue or freshness. | Good for B/C races, testing, or recovery weeks. |
| +15 to +25 | Peak Race Form | Fresh and fit. Optimal performance window. | A-priority races. Expected peak performance. |
| +25 to +35 | Very Fresh | Highly rested. Good for sprints. | Short races, time trials, very rested state. |
| > +35 | Detraining | Losing fitness from inactivity. | Resume training. Fitness declining from extended rest. |
🎯 Target TSB by Race Distance
- Sprint/Olympic Triathlon: TSB +15 to +25 (7-10 day taper)
- Half Ironman (70.3): TSB +20 to +30 (10-14 day taper)
- Full Ironman: TSB +15 to +25 (14-21 day taper)
- Pool Swimming Events: TSB +15 to +25 (7-14 day taper depending on event)
PMC Example: Training Block → Taper → Race
8-Week Training Cycle
Weeks 1-5: Building Phase
- Weekly TSS: 400 → 450 → 500 → 550 → 550
- CTL: Gradually rises from 50 → 65
- ATL: Tracks weekly load, fluctuates 55-80
- TSB: Negative (-15 to -25), indicates productive training stress
Week 6: Recovery Week
- Weekly TSS: 300 (40% reduction)
- CTL: Slight dip to ~63 (fitness retained)
- ATL: Drops to ~50 (fatigue dissipates)
- TSB: Rises to +5 (partial freshness)
Week 7: Final Build
- Weekly TSS: 500
- CTL: Climbs to ~65
- ATL: Jumps to ~75
- TSB: Returns to -20 (quality training absorbed)
Week 8: Taper + Race
- Days 1-9: Reduced volume, maintain intensity (200 TSS total)
- CTL: Gentle decline to ~62 (minimal fitness loss)
- ATL: Rapid drop to ~40 (fatigue eliminated)
- TSB: Peaks at +20 on race day
- Result: Fresh, fit, ready to perform
✅ Why Taper Works
The different time constants (42 days for CTL, 7 days for ATL) create the taper effect:
- ATL responds quickly → Fatigue disappears within 7-10 days
- CTL responds slowly → Fitness persists for weeks
- Result: Fitness remains while fatigue vanishes = peak performance
Practical Application Guidelines
1️⃣ Track Daily sTSS
Consistency is key. Log every workout's sTSS to build accurate CTL/ATL/TSB trends. Missing data creates gaps in the fitness curve.
2️⃣ Monitor CTL Ramp Rate
Increase CTL gradually. A 5-7 point weekly increase is sustainable for most swimmers. Jumping 15-20 points invites injury.
3️⃣ Plan Recovery Weeks
Every 3-4 weeks, reduce volume 30-50% for one week. Let TSB rise to -5 to +10. This consolidates fitness and prevents overtraining.
4️⃣ Time Your Taper
Target TSB +15 to +25 on race day. Begin taper 7-14 days out depending on event distance and current TSB.
5️⃣ Don't Panic with Negative TSB
TSB of -20 to -30 during build phases is normal and productive. It means you're applying stimulus for adaptation.
6️⃣ Respect CTL Decay
After a break from training, don't try to resume at previous CTL immediately. Rebuild gradually to avoid injury.
Master Your Training Load
The PMC transforms subjective training into objective data. By monitoring sTSS, CTL, ATL, and TSB, you gain precise control over fitness progression, fatigue management, and peak performance timing.