#262 – AMA #49: Heart rate recovery, strength training, rucking, kidney function, and brain health

[Heart rate recovery] is one of the metrics that we should care about just as we care about VO2 max and just as we care about resting heart rate.” —Peter Attia

Read Time 31 minutes

In this “Ask Me Anything” (AMA) episode, Peter addresses follow-up questions related to recent conversations around exercise, kidney function, and brain health. He begins with the topic of exercise, covering aspects such as starting rucking, transitioning from muscle building to maintenance, the optimal order of lifting weights and cardio, and exploring heart rate recovery. Shifting gears, he delves into the realm of kidney health, discussing the most effective blood tests to measure kidney function, desired levels, the natural decline with age, and the crucial role of maintaining a high glomerular filtration rate for longevity. Additionally, he discusses the importance of managing homocysteine levels and alcohol consumption for brain health.

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We discuss:

  • Topics: exercise, kidneys, and brain health [1:30];
  • Rucking: advice for beginners, proper load, packs, and shoes [4:30];
  • Rucking for women, bone health, using a treadmill, zone 2, and more [11:45];
  • Building vs. maintaining: when and how to transition from the goal of building muscle and strength to focusing on maintenance [16:00];
  • Should you lift weights before or after a cardio session? [24:00];
  • Heart rate recovery: defining heart rate recovery and how it relates to cardiovascular fitness [28:45];
  • How to measure heart rate recovery, and what is considered a “good” heart rate recovery [33:15];
  • How kidney health and function typically measured [42:30];
  • Differentiating between creatine and creatinine [48:15];
  • The cystatin C blood test as a practical way to assess kidney health [52:45];
  • How kidney function impacts lifespan and the five stages of kidney disease [59:15];
  • Slowing the decline of kidney function [1:08:15];
  • The main drivers of kidney disease [1:11:15];
  • The importance of managing homocysteine levels for brain health [1:14:00];
  • The relationship between alcohol consumption and brain health [1:21:30]; and
  • More.


Topics: exercise, kidneys, and brain health [1:30]

For today’s AMA, going to cover a few different topics:

  • Exercise​​
    • Rucking – advice for beginners, what weight to use, how to know when to ratchet it up, what shoes to wear, and more
    • When and how to thinking through your goals of building muscle and strength versus maintenance
    • Should you lift before or after cardio, what one is “better”?
    • Questions on heart rate recovery – what it is and why it’s relevant
  • Kidneys
    • Most effective and practice ways to measure kidney function
    • The desired levels to look for 
    • The natural decline with age and how to combat it
    • And the crucial role of maintaining a high glomerular filtration rate for longevity
  • Brain health
    • Answering follow up questions from AMA #46 such as… 
    • The importance of managing homocysteine levels for brain health
    • The relationship between alcohol consumption and brain health — is any amount of alcohol “good” for the brain?


Rucking: advice for beginners, proper load, packs, and shoes [4:30]

⇒ Peter has already discussed with Michael Easter how he enjoys rucking for its physical and mental benefits with as well as on AMA #39 

What weight should people start at when they’re going to ruck?

  • It’s completely dependent on the fitness and health of the person.
  • One end of the spectrum as little as just walking with an empty backpack
  • For others, they might start with 10% of their body weight
  • But you don’t really need to go beyond about a third of your body weight
  • The true answer is highly dependent on the terrain—how flat it is, how uneven it is—all of these things make it obviously more or less difficult
  • The first few times you go out there, it’s hard to overstate how foreign it can feel on your shoulders, on your traps 
  • And you don’t want to overdo it, for a couple reasons
    • 1) there’s just a risk of getting injured
    • 2) you want to enjoy this
  • When in doubt start with a low weight, and if you come back from a ruck and you felt like there was no additional stress then just add incremental weight the next time and so on

How to add weight and rucking packs [7:00]

Do you recommend everyone gets a waistband to go with a ruck bag?

  • There are very different styles of rucking
  • For instance, some people who really prefer to have all the weight in their shoulders and they don’t want to have any of it on their waist

There’s really three things to consider when using a rucking pack of backpack

  • 1 – The waistband strap that allows you to, if you cinch it down correctly, it allows you to keep more of that weight on your hips
  • 2 – On the front of a backpack, there’s a little strap that keeps the straps of the pack more or less tight
  • 3 – Then there are the straps that are pulling on your shoulders
  • Most people benefit from a hip belt because it is advantageous to put more of the weight on your hips than on your shoulders

For Peter personally, he actually doesn’t even buckle the small strap that joins the shoulder straps

{end of show notes preview}


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  1. The evidence does not seem to support the commonly held notion that modern contrast agents negatively affect renal function. There are no RCTs on this one way or the other and the observational data seem to suggest contrast-induced nephropathy is not real. There is a great article about this on EMCrit with links to many of the studies.


  2. If you like rucking, and possess a masochistic personality disorder, then you would probably enjoy going on a canoe trip in Algonquin Park during the blackfly and mosquito season. Portaging a cedar strip canoe one to two miles provides an opportunity to bun off a few pounds. Canoe tripping in Killarney will provide some vertical and the North Bay to Mattawa canoe race (along the old voyageur route) will burn a few pounds in a day.

  3. GREAT AMA guys, wow. Just wanted to give my 2 cents, I think most doctors use CrCl or eGFR because drug monographs use these measures to recommend dose adjustments.

  4. Quick question regarding calculating eGFR using Cystatin C- if you order a Cystatin C test will they automatically give you the eGFR based on cystatin C or do you need request it when ordering labs?

    I’m living one of your examples. 55 years old, I lift weights but recently increased intensity and protien intake. eGFR went from 79 to 62 in 12 months.

  5. I have tried the lowest dose of Jarrow Methyl B12 500mcg recently. I even cut the tablet up and tried to titrate up, but cannot seem to tolerate it well. Are there other options that you have seen work well for those of us who struggle with jarrow methyl b12? I also get about as much b12 in my diet as I am going to reasonably be able to maintain over a long period of time. Thank you.

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