Cardio Curiosity: A Small Shift, A Big Surprise

This morning at the gym, I had one of those subtle but eye-opening moments during cardio, something worth sharing, even if it's just anecdotal.

Cardio days are my break from lifting. I treat them as active recovery, focused on heart health rather than intensity. My usual setup is the Life Fitness treadmill: Hill mode, level 15, 3 mph for one hour. The incline fluctuates between 5° and 10°, and during the steepest sections, my heart rate can climb to around 121 bpm. But that’s the peak. During the flatter segments, it drops significantly, sometimes dipping well below that number. The workout ends up feeling like a rollercoaster of effort: steep climbs followed by easy strolls.

Today, I decided to tweak the formula.

I lowered the level from 15 to 12 and nudged the speed up to 3.2 mph. That adjustment softened the incline range to roughly 2°–8°, and I expected a slightly easier ride with a lower heart rate. Instead, I hit the same peak: 121 bpm.

What surprised me wasn’t just the number, it was the consistency. The workout felt smoother, more regulated. Without the steep incline swings, my heart rate stayed elevated more evenly throughout the hour. The increased speed seemed to stabilize the effort, avoiding those dramatic drops during the easier segments.

Of course, this is just one experience. But it reminded me how small changes, speed vs. incline, intensity vs. consistency, can shift the cardio equation in unexpected ways. It’s a good reminder that heart rate isn’t just about how steep the hill is. Sometimes, it’s about how steady the climb feels.

Just a little cardio curiosity from today’s gym session. Thought it was worth putting out there.