9. What I Learned from More Than 30 Years of CPX

For decades, I have used CPX to evaluate patients and athletes.

CPX often focuses on AT (anaerobic threshold) and VO₂max.

These are valuable measurements.

But over the years, I became increasingly interested in another region:

the area below AT, where breathing and aerobic metabolism remain relatively stable.

I also became interested in RQ/RER and what it tells us about substrate utilization during lower-intensity exercise.

Instead of looking only at what happens near maximum effort, I began asking:

What is happening when the body is still comfortable?

That question gradually changed the way I thought about exercise.

CPX（心肺運動負荷テスト）の代表的な例です。

CPX Results: The Power of Gentle, Sustained Exercise

Left: Before — High-Intensity Training

The athlete initially trained at an intensity that caused breathlessness. However, this demanding approach was difficult to sustain, and the training was eventually discontinued.

Right: After — Gentle, Sustained Training (Around 50% Intensity)

The athlete then switched to a gentler approach: exercising at a comfortable pace, without becoming breathless, and continuing for longer periods.

The CPX results show remarkable improvements following this change.

The white dotted line represents oxygen uptake (VO₂), while the red dotted line represents carbon dioxide output (VCO₂).

After sustained, low-intensity training, three important changes were observed:

Anaerobic Threshold (AT) increased substantially, indicating improved aerobic endurance.
Peak VO₂ increased markedly, demonstrating improved overall exercise capacity.
The respiratory exchange ratio (RER = VCO₂/VO₂) decreased below AT, suggesting improved fat oxidation and more efficient aerobic metabolism.

What makes these findings particularly interesting is that these improvements occurred without high-intensity training.

Instead, they followed a simple approach: gentle exercise, sustained for longer periods.

This is consistent with my long-standing clinical observation that developing a strong aerobic foundation does not necessarily require intense exercise.

Sometimes, exercising more gently—and continuing longer—can produce remarkable improvements in endurance and metabolic efficiency.

日本語訳（要点）

CPX結果：弱い刺激を長く続ける運動の力

左図は、当初、息切れする強度でトレーニングを開始したものの、継続が難しく、途中で中止した状態です。

右図は、その後、息切れしない程度の弱めの運動（最大能力の約50％）に切り替え、少し長めに継続した後のCPX結果です。

白点線は酸素摂取量（VO₂）、赤点線は二酸化炭素排出量（VCO₂）を示しています。

低強度運動を継続した結果、ATとPeak VO₂が大きく増加しました。

さらに注目すべきことは、AT以下の呼吸交換比（RER）が低下していることです。

これは、運動中の脂質酸化の割合が高まり、有酸素代謝が改善した可能性を示唆しています。

これらの変化は、高強度トレーニングを行わず、弱めの運動を長く続けることで得られたものです。

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≪to be continued≫

Dr.Monjiro#101（10.21）