Early Detection of Overtraining Syndrome (OTS) in Triathlon — HRV, Heart Rate, and Perceived Exertion

What is Overtraining Syndrome (OTS)?

OTS (Overtraining Syndrome) occurs when long-term training volume exceeds recovery capacity, leading to:

• Persistent performance decline lasting weeks to months
• Low mood, irritability, insomnia
• Suppressed immunity (frequent colds)
• Changes in appetite
• Hormonal disruption (elevated cortisol, decreased testosterone)

Unlike short-term Functional Overreaching (FOR), OTS requires months to fully recover and is the biggest invisible killer for triathletes.

The Three Stages of OTS

Stage 1: Functional Overreaching (FOR)

• Short-term performance decline lasting 7-14 days
• Bounces back with proper deloading
• This is a normal part of training

Stage 2: Non-functional Overreaching (NFOR)

• Performance decline lasting 2-8 weeks
• Requires extended rest to recover
• Already exceeds normal load

Stage 3: Overtraining Syndrome (OTS)

• Performance decline lasting more than 2 months
• May take months or even a year to recover
• Severely impacts daily life

Five Early Detection Indicators

Indicator 1: HRV (Heart Rate Variability)

HRV is the gold standard for OTS detection. When HRV consistently falls more than 10ms below the 7-day average, it is a warning sign.

Measurement Method

• Measure within 5 minutes of waking each morning
• Use Polar H10, Whoop, Garmin, or Oura
• Measure for 7-14 consecutive days to establish a baseline

Interpretation Guide

HRV Change	Training Recommendation
Baseline +5% or higher	Normal training or increase volume
Baseline ±5%	Normal training
Baseline -5% to -10%	Reduce volume by 20-30%
Baseline -10% or lower	Complete rest for 1-2 days

Indicator 2: Resting Heart Rate (RHR)

Resting heart rate consistently 5bpm or more above baseline for 3 consecutive days is an OTS warning sign.

Measurement Method

• Measure within 5 minutes of waking each morning
• Use a sleep tracker for automatic recording
• Observe the 7-14 day average

Indicator 3: Training Perception (RPE Deviation)

A deviation between RPE (Rating of Perceived Exertion) and actual intensity is an OTS warning sign.

Deviation Assessment

Same Heart Rate/Power	RPE Deviation
Normal	RPE unchanged
Mild fatigue	RPE +1
OTS warning	RPE +2 or higher for 3 consecutive days

Indicator 4: Sleep Quality

• Time to fall asleep > 30 minutes for more than 3 consecutive days
• Waking up 2 or more times during the night
• Deep sleep < 1 hr (track with Oura/Whoop)
• Sleep efficiency < 85%

Indicator 5: Mood and Motivation

Use the simplified POMS (Profile of Mood States) for weekly assessment:

Item	Score 1-5
Training motivation	1 = absolutely no desire to train
Overall fatigue	1 = extremely fatigued
Mood	1 = low and irritable
Appetite	1 = no appetite at all
Libido	1 = almost none

Total score < 15 for 7 consecutive days is an OTS warning sign.

Comprehensive Objective Data Monitoring

TSB (Training Stress Balance)

Track with TrainingPeaks or intervals.icu:

TSB	Status	Recommendation
> +25	Excessive deloading	Increase training volume
+5 ~ +25	Peak condition	Race window
-10 ~ +5	Normal training	Maintain
-30 ~ -10	High training load	Focus on recovery
< -30	Overload warning	Mandatory deload

CTL/ATL Ratio

• CTL (Chronic Training Load) = 42-day average TSS
• ATL (Acute Training Load) = 7-day average TSS
• ATL > CTL × 1.5 for 2 consecutive weeks = OTS risk

Five Strategies to Prevent OTS

Strategy 1: 3:1 Microcycle

After every 3 weeks of accumulation, deload by 30% in the 4th week.

Strategy 2: At Least 1 Full Rest Day Per Week

Not “easy training,” but complete inactivity.

Strategy 3: Prioritize Sleep

At least 8 hours per day, and 9 hours per day for the month before a race.

Strategy 4: Adequate Nutrition

• Carbohydrates: 6-10g per kg of body weight
• Protein: 1.6-2.2g per kg of body weight
• Avoid Low Energy Availability (LEA)

Strategy 5: Regular Blood Testing

• Pre-season tests: ferritin, vitamin D, cortisol, testosterone
• Ferritin < 30 ng/ml = iron deficiency, supplementation required

OTS Management Steps

If OTS is suspected:

1. Immediately stop high-intensity training for 7-14 days
2. Switch to Z1-Z2 recovery training
3. Increase sleep + nutrition + hydration
4. Seek medical evaluation: blood tests, ECG
5. After full recovery, restart from the base phase

Conclusion

OTS is the biggest “invisible enemy” for triathletes. Establishing daily monitoring habits for HRV + resting heart rate + RPE is more important than chasing training volume every day. The race winner is not the one who trains the most, but the one who recovers the best.

Related Reading

• Identifying Overtraining Syndrome (OTS) and Returning to a Training Plan
• Recognizing Overtraining Syndrome: 6 Body Warning Signs You Can’t Ignore
• Chronic Overtraining Syndrome (OTS): When Passion Turns into Injury
• Overtraining Syndrome (OTS): Identification, Prevention, and Complete Recovery Strategies