Endurance
Zone 2 in 34°C: base building without melting
Daniel Okafor · Sat 18 Jul · 6 min read
Every runner who joins River Run Club hears the same thing in week one: slow down. Zone 2 — the effort where you can still hold a conversation — builds the aerobic engine that every distance from 5K to marathon runs on. The catch in Bangkok is that heat pushes your heart rate up before your legs do any real work.
Our rule of thumb: in the hot season, your usual Zone 2 pace is 30–60 seconds per kilometre slower than what your watch thinks. Run to heart rate, not pace. If your conversational effort is 6:30/km at 6am and 7:15/km at 9am, both are correct.
We schedule base runs at 5:45–7:00, keep the route shaded along the river, and treat electrolytes as non-negotiable above 45 minutes. Members on the marathon block get a weekly treadmill session in the cool studio purely so one quality session a week happens at true pace.
The payoff compounds quietly. Most members who commit to twelve weeks of honest Zone 2 see their easy pace drop by a minute per kilometre at the same heart rate — before we add any intervals at all.
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Every article starts as advice we give members on the floor.