Discover more from Endurance Philosophy

Sharing lessons learned along the journey of becoming an Ironman and building an endurance community on Twitter.

Over 1,000 subscribers

Lactate Test Results: Maxing Out Fat Loss For Bodybuilding

And breaking free from generic cardio routines

Ryan Dreyer

Mar 31, 2023

My bodybuilding buddy Jason Lewis came to me for help maximizing his fat loss.

Jason competed in his first bodybuilding show last year and got absolutely shredded.

But he tortured himself with grueling and generic stairmaster cardio.

He saw my lactate test with Gordo and questioned if he could be more effective.

We jumped on a call and I quickly realized he could use a more calculated approach that would…

be more effective for fat loss
be lower intensity and less grueling mentally
add balance and flexibility to an otherwise strict bodybuilding program

So I offered to run a lactate test on him and help build his plan.

The Standard Bodybuilding Cardio Routine

Here’s the routine he followed in prep for his first show:

stair master
45 minutes per day
6 days per week
moderate to high intensity, every time

My immediate assumption was that he was doing cardio too intensely and burning more carbs than fat for fuel.

Same Logic, Different Sport

I guessed that…

his aerobic base was moderate
his lactate was rising over 2.0 mmoL during sessions

We know that aerobic training (Z1/Z2) is where the body maximizes fat burning in endurance training.

So I thought: why would it be different in cardio done for bodybuilding?

Fat burning vs. Carb burning as intensity rises

Where I Thought I Could Be Wrong

There was one caveat to my logic:

I wondered if the moderate/high intensity stairmaster exercise was adding enough lower body muscle to increase his total caloric burn at rest.

And I wondered if total caloric burn made a bigger difference in his overall physique than getting specific about whether his body was burning fat or carbs.

But I didn’t think this was the case.

He lifts 6 days per week with an emphasis on progressive overload and building strength.

I figured his strength plan was influencing the majority of his caloric burn.

Manipulating his cardio would help him gain a few percentage points of progress on the margins of his program.

In The Lactate Lab

I met up with Jason at his gym and brought the lactate test equipment Gordo generously lent me.

Instead of using the stairmaster, I opted to have him do incline walking on the treadmill.

The treadmill would give us a more complete warmup and make it easier to control his heart rate.

Test Set Up

The main metrics we followed were:

Heart Rate
Treadmill speed
Treadmill incline
Lactate readings

We didn’t have a HR chest strap, so we relied on Jason’s Whoop and Apple Watch for the data.

Lactate Test Baseline

We had imperfect data from the jump.

Jason’s baseline lactate before the test was elevated at 3.2 mmoL.

He came into the test a little dehydrated and was in the midst of moving apartments.

Dehydration and life stress can both lead to elevated lactate.

I would have liked to see him at 1.2 to 1.5 mmoL before we began.

But we continued on with the test and decided to see if anything would change.

Lactate Test Results

After a 15 minute warm up, Jason’s lactate had a positive response and dropped to 1.6 mmoL.

This would be the best lactate reading in the entire test and the primary prescription for future cardio.

Treadmill speed: 3.2 mph
Treadmill incline: 5.0
Heart Rate: 98 (readings were unreliable throughout the test)

Although we had imperfect data, I determined 1.6 mmoL was his Aerobic Threshold and where he would maximize both his fat burning and base fitness development.

On top of this, we noticed a subtle deepening of his breath, indicating the reading was accurate and that he was right at the border between Z1 and Z2.

Here are the rest of the test results:

Additional Test Notes

Heart Rate Readings:

The heart rate readings from the Whoop and Apple Watch were both unreliable, especially through the first half of the test.

The 2 devices were often showing readings that were 15+ beats apart.

In a future test, we will make sure to use a chest strap.

Lifting Callouses:

Jason’s hands were so calloused from lifting iron that we struggled to get testable blood droplets until he was fully warmed up.

My Recommendation For Future Cardio

Jason should keep a minimum of 80% of his cardio training under 115 bpm.

While heart rate readings were not perfect during the test, it’s safe to assume that his aerobic threshold is around 100-105 bpm and his Z2 ceiling is around 120-125 bpm.

If on a treadmill, he can do the same 3.2 speed and 5.0 incline that we saw a positive lactate response with during the test.

I encouraged him to include bike training as well.

On top of maximizing fat burning, shifting to lower intensity cardio will prevent adding unnecessary fatigue to an already demanding strength training split.

Do you have questions on maximizing your fat burning?

Reply or comment below and I’ll help you out.