My VO2max Results (2018-05-04)

I took my VO2max test today and achieved my predicted results. My prediction was:

I want to make a prediction about what my VO2 Max will be now before I take the test. After 9 months of mediocre performance in CrossFit I expect my number to be at the bottom end of good for my age range. I predict it will be about 36 ml/kg/min.

I got 34.6 which on the WVU scale (apparently there are different scales used at different facilities) which is at the bottom end of good for my age range. So my prediction of my performance was right where I expected it to be. And that’s perfectly fine.

Why Not Better?

I believe it’s lower being Low Carb and having Low Body Fat worked against me. If I was carb fueled and had higher body fat I would have more fuel for the engine. I had never exercised before CrossFit which I started 9 months ago. I’ve made huge strides since then in improving my physical fitness.

Heart Rate

My Samsung Gear Sport Watch showed my heart rate max at much lower numbers than the ECG. ECG had my max heart rate at 173. Watch had 130. Expected watch to show higher. Now I am confused. Is it a function of the treadmill mode on the watch vs “other workout” mode that I usually use?

A heart rate of 173 is pretty high. I am 57 so they normal max heart rate is 220 minus age or 153. I got 20 bpm higher than that value and they let you do this at higher than max heart rate but it is one of the termination conditions (it takes a few of them to be present for them to stop the test).

VO2 Max and Athletes

Originally posted 2018-04-20.

Vo2 Max is (VO2 Max and How It Is Measured in Athletes – Measure of Aerobic Fitness and Maximal Oxygen Uptake):

VO2 max is the measurement of the maximum amount of oxygen that an individual can utilize during intense, or maximal exercise. It is measured as milliliters of oxygen used in one minute per kilogram of body weight (ml/kg/min).

I made an appointment for 2 weeks from now to get my VO2 Max measured at the WVU Human Performance Lab. I hope to get some answers about my exercise capacity. For one thing:

Accurate measurement of VO2 max is done in a sports performance lab. An all-out effort is performed on a treadmill or bicycle under a strict protocol. These protocols involve specific increases in the speed and intensity of the exercise and collection and measurement of the volume and oxygen concentration of inhaled and exhaled air.

I want to make a prediction about what my VO2 Max will be now before I take the test. After 9 months of mediocre performance in CrossFit I expect my number to be at the bottom end of good for my age range. I predict it will be about 36 ml/kg/min. Let’s see if I am correct or not.

 

Fat Adapted Athletes

Here’s a great study on fat adapted athletes (Lambert EV, Speechly DP, Dennis SC, Noakes TD. Enhanced endurance in trained cyclists during moderate intensity exercise following 2 weeks adaptation to a high fat diet. Eur J Appl Physiol Occup Physiol. 1994;69(4):287-93.).

The study looked at five cyclists and compared them on a High Carb vs a High Fat diet.

Despite a lower muscle glycogen content at the onset of MIE [32 (SEM 7) vs 73 (SEM 6) mmol · kg −1 wet mass, HIGH-FAT vs HIGH-CHO, P < 0.01], exercise time to exhaustion during subsequent MIE was significantly longer after the HIGH-FAT diet [79.7 (SEM 7.6) vs 42.5 (SEM 6.8) min, HIGH-FAT vs HIGH-CHO, P<0.01]

Looks like they have an almost 2x advantage when it comes to endurance.

How long did it take to convert these athletes from Carb Adapted to Fat Adapted?

These results would suggest that 2 weeks of adaptation to a high-fat diet would result in an enhanced resistance to fatigue and a significant sparing of endogenous carbohydrate during low to moderate intensity exercise in a relatively glycogen-depleted state and unimpaired performance during high intensity exercise.

Only two weeks!

 

Muscle Glycogen and Exercise – Phinney Revisited

Stephen Phinney et.al. did an interesting study which put elite bicycle races on a ketogenic diet  (Metabolism. 1983 Aug;32(8):769-76. The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation. Phinney SD, Bistrian BR, Evans WJ, Gervino E, Blackburn GL).

The study measured the amount of muscle glycogen in the subjects before they went on the ketogenic diet and after then they had been in the diet for 4 weeks and before/after exercise in both diets. Here’s the mean values.

Pre-Keto
Before Exercise
Pre-Keto
After Exercise
Keto Wk 4
Before Exercise
Keto Wk 4
After Exercise
Mean 143 53 76 56

After the four weeks the subjects had approximately half the muscle glycogen in the ketogenic state. The fact that the post exercise numbers were similar pre and post keto appears to show the glycogen sparing effects of the diet. The study states that the reason that the muscle glycogen doesn’t go to zero is that there is muscle glycogen stored in fast and slow twitch muscles. The slow twitch muscles were used during this exercise and depleted by this test. Hence, glycogen use was 90 pre-keto and only 20 post keto.

RER Shift from Carbs to Fat

The difference between the two diets  is also seen in the shift down of the RQ (RER) of the subjects during exercise from a mean of 0.83 to 0.72. This represents a significant shift towards fat oxidation in place of carbohydrate oxidation.

My Own Numbers on Low Carb Diet

Adding in my VO2max numbers to the chart from a previous post:

HR RER %Fat %Carbs %VO2max
120 0.70 99% 1% 56%
125 0.74 88% 12% 61%
130 0.77 77% 23% 66%
135 0.80 66% 34% 71%
140 0.84 55% 45% 77%
145 0.87 44% 56% 82%
150 0.90 33% 67% 87%
155 0.94 21% 79% 92%
160 0.97 10% 90% 97%
165 1.00 0% 100% 102%

For me, 65% of my VO2max corresponds to a heart rate of about 129 or fat as about 79% of calories. My RER was about 0.75 at that rate which is not as good as the elite bicyclists in this study who were at an RER or 0.72 at that level of activity. Hopefully with additional cardio training my RER will be reduced further during exercise.

Energy Used

The study showed that the athletes used about 950 kcals/hr. Before keto 28% of that came from carbs and the rest from fat. After keto, the carb oxidation rate dropped to 9%.

The energy from fat when in keto was 864 kcal/hr which is 1.6 g/min. This is a high level of fat oxidation and is more than my own fat oxidation rate (of around 1.2 g/min).

 

Does Exercise Increase Energy Expenditure While Dieting?

Here is a study that looked at resting energy expenditure (REE) under a calorie restricted diet (L C Henson D C Poole C P Donahoe D Heber. Effects of exercise training on resting energy expenditure during caloric restriction. The American Journal of Clinical Nutrition, Volume 46, Issue 6, 1 December 1987, Pages 893–899).

The seven subjects were moderately obese women put on a calorie restricted diet. The test was lasted nine weeks. They were exercised for three weeks at the end of their diet at 70% of their VO2max.

Resting energy expenditure (REE), maximum oxygen uptake (VO2max), and body composition were measured in seven moderately obese women during 9 wk of dietary restriction (800 kcal/d). During weeks 4-6, subjects underwent exercise training (30 min cycling/d, 5 d/wk, at 70% VO2max).

The conclusions were:

The first 3 wk of caloric restriction decreased REE by 13% (from 1437 +/- 76 to 1254 +/- 66 kcal/24 h, means +/- SEM, p less than 0.05).

That shouldn’t be a surprise since weight loss results in a reduction of Energy Expenditure.  The numbers need to be compared closely to the actual weight loss to see how much of the reduction in TDEE was from the weight difference and how much was from metabolic adaptation.

How was their performance affected?

Exercise training increased VO2max (from 1717 +/- 108 to 1960 +/- 120 mL/min, means +/- SEM, p less than 0.05)

Their VO2max showed a substantial improvement for only three weeks of training. It would have been interesting to have a control group which was not put on the exercise program to tease out whether some of this was due to weight reduction or it was due to the exercise.

but did not elevate the dietary-depressed REE (from 1254 +/- 66 to 1262 +/- 62 kcal/24 h).

It looks like the REE did show an increase but it was not statistically significant.

The greatest decrease in body fat (3.7 +/- 0.4 kg) occurred during exercise training, resulting in a small apparent increase in REE when expressed per kilogram total body weight. However, expressed per unit lean body mass, REE remained suppressed throughout the period of caloric restriction.

At 70% of VO2max they were at a good rate for loss of both carbohydrates and fat stores. It would be interesting to see their actual rates of substrate metabolism.

Their conclusions?

We conclude that exercise training of sufficient intensity to substantially increase VO2max does not reverse the dietary-induced depression of REE.

This is interesting since there’s a common assumption that exercising will cause people to burn more calories at rest but that wasn’t the case in this particular situation.

However, the increase in VO2max itself was worthwhile as it indicates a gain in fitness.