Brilliant peak flow rate, terrible VO2max

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I've just had my second fitness test, 5 months apart. In November I had a peak flow of 480 (off the chart good), and a VO2 max of 25 (very poor).

Today I had a peak flow of 520 (off the chart good) and a VO2 max of 31.4 (borderline very poor/poor).

If I'm interpreting that properly, I'm breathing in just fine, and taking in enough oxygen. What it's not doing is getting to my muscles when I run. What sort of reasons might there be? (And yes, I will go to the doctor if I need to.)

In case it's relevant, my blood pressure is normally around 100/70 (low) and my heart rate while comfortably running 5k in 34-36 mins is 176 (high for sustained effort!).

Yes, there is a difference between ventilation (peak flow) and oxygen uptake (VO2). As already mentioned, ventilation just refers to moving air in and out, VO2 is the actual oxygen uptake. Think of as catching fish in a flowing stream. There could be plenty of water and plenty of fish, but if you have a small net with a lot of holes, your volume of fish caught will be disproportionately low.

My main addition is that VO2 is more that just oxygen absorption into the bloodstream. Actually, movement across the membrane is probably fine and doesn't change that much. Increases is VO2 are primarily due to increases in cardiac output--total amount of blood pumped--and an increase in capillary density and the cellular structures/enzymes that are involved in aerobic metabolism.

In short, the mismatch between your pulmonary function and oxygen uptake does not reflect a medical issue and the VO2 max numbers your are reporting correlate to your reported 5K running times.

Thanks - it's certainly not because I haven't done enough miles.

How would you define "too fast"? If I can sustain the pace for the distance required and be comfortable at the end, wouldn't that be a good pace to run at?

How much are you running per week? A beginning runner training for the 5K should be running between 20 and 30 miles per week minimum (1). As you progress past beginner the weekly mileage goes up to coninue improvement. Many of the people at the front of local 5Ks are running up to 60 or more miles per week.

How many times per week do you run? Four times per week is probably optimum as it presents the highest fitness gains before the injury risk starts to rise significantly (2). If you can run more often than that without injury you will improve faster. You also should be doing one run a week that is 90 minutes long minimum. Two hours is a lot better.

What is your maximum heart rate? If you havent done so already you should do a maximum heartrate test so that you can accurately determine training zones. For now, I'll assume your max is around what the formula predicts which is 190. You said you do your runs at 170 heartrate. That is 90% and is way to high for daily runs. Not less than 80% of your weekly mileage needs to be easy at 70 to 80% max HR or below. That means you should be running between 133 and 150 on most of your daily runs. The aerobic adaptations that Azdak mentioned above are primarily stimulated by running at this intensity. By running a lot harder all the time you are not getting these aerobic adaptations and are not training the slow twitch muscle fibers much at all.

You will not improve by running 5K race pace all the time. For example, my 5K race pace is 6:40/mi right now. My daily easy run training pace is around 8:20 to 8:50/mi. I also do some runs at 10:00/mi. These runs, done in high volume, are what stimulate the aerobic adaptations that enable me to run at 6:40/mi for three miles.


1. Run Faster from the 5K to the Marathon, How to Be Your Own Best Coach by Brad Hudson and Matt Fitzgerald. Table 3.1
2. From Lore of Running by Dr. Timothy Noakes, MD