Science15 min
Strength Endurance Training for Endurance Athletes
Strength endurance delays fatigue and protects against injury. See what the science says, the right loads and reps, and protocols for each sport.
Read articleCalculate Your Training Zones
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Triathlon13 min
Triathlon Nutrition by Distance: Sprint to Ironman
How to fuel every triathlon distance. Exact carbs, fluid and sodium per hour for Sprint, Olympic, 70.3 and Ironman, plus a race-day plan.
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Science12 min
Lactic Acid vs Lactate: What Your Body Actually Makes
Lactic acid and lactate aren't the same thing, and only one actually exists in your muscles. Here's what exercise science really says about the burn.
Read articleTraining Zones Explained
From active recovery to all-out sprints - each zone triggers different adaptations to optimize your performance.
Metric
1Recovery
2Endurance
3Tempo
4Threshold
5VO₂max
Heart Rate
50–60%
60–70%
70–80%
80–90%
90–100%
Perceived Exertion (RPE)
1–2
3–4
5–6
7–8
9–10
Breathing
Easy conversation
Can hold conversation
Short sentences only
A few words only
Unable to speak
Running
Very easy jog
Easy, steady pace
Sustained pace, half-marathon
10K pace, hard effort
Sprint, all-out effort
Cycling (% FTP)
< 55%
56–75%
76–90%
91–105%
> 105%
Swimming (% CSS)
< 75%
75–85%
86–95%
96–105%
> 105%
Energy System
Fat oxidation
Fat + some carbs
Carbs + fat
Mostly carbohydrates
Anaerobic (ATP-CP + glycolysis)
Sustainable Duration
Trained: > 7 hBeginner: < 3 h
Trained: > 5 hBeginner: < 2 h
Trained: 2–3 hBeginner: < 45 min
Trained: 20–60 minBeginner: < 20 min
Trained: 5–7 minBeginner: < 3 min
Key Benefit
Active recovery, blood circulation
Aerobic base, fundamental endurance
Lactate threshold, running economy
VO₂max, maximal aerobic power
Maximum speed, anaerobic power
HR= % HRmaxFTP= Functional Threshold PowerCSS= Critical Swim SpeedRPE= Rate of Perceived Exertion (1–10)
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