Today was scheduled for a long slow distance (LSD) run. The goal was simple: get the distance in while keeping the intensity strictly within the aerobic development zone (Zone 2). I ended up with exactly 21.21km — a very satisfying and memorable number on the watch.
Fighting the Summer Heat and Cardiac Drift#
Starting early is the only way to survive July running, but even then, the sun rises fast and the humidity is relentless. Here is how the run unfolded:
- First 10km: Felt fantastic and locked in. Heart rate stayed beautifully within my target Zone 2 range (around 135–142 bpm), and the rhythm was smooth.
- After 10km: The temperature rose quickly. This is where cardiac drift kicked in — the heart has to work harder to pump blood to the skin for cooling, causing the heart rate to climb even if the speed doesn’t change.
- The Adjustment: To prevent my heart rate from spiking into Zone 3 and beyond, I had to dial back my pace significantly. It took some discipline to slow down and embrace a slower stride, but keeping the stress on the aerobic system (rather than muscle fatigue) is what summer base building is all about.
A tough but rewarding morning. Paces might be slower in the summer, but the heart doesn’t lie — the effort was there, and these hot miles will pay off when autumn arrives.