Podcast Episode #25: What Your Parents Didn’t Tell You About Metabolic Testing

Ben Greenfield (0:00)

Podcast, episode number 25 from bengreenfieldfitness.com.

Welcome to the bengreenfieldfitness.com podcast, your free weekly audio exposure to cutting edge fitness, nutrition, and wellness information. My name is Ben Greenfield, and I'm an exercise physiologist, certified personal trainer, and nutritionist. Each week, I'll be bringing you information that goes outside, run of the mill exercise and diet advice. So whether you're an Ironman triathlete or you're just trying to lose a few pounds, enjoy this week's podcast episode from bengreenfieldfitness.com.

Hey, podcast listeners, happy holidays, and welcome to the December 9th episode from bengreenfieldfitness.com. Today's episode is gonna give you just a ton of information on metabolic testing, everything that your parents didn't tell you about it.

I also have an interview with pro triathlete, Angela Nath, who is actually the eighth place pro female at the Half Ironman Triathlon World Championships, which happened recently down in Clearwater, Florida. We're gonna do a listener Q&A on how quickly you can actually lose your fitness after you quit training. And then I have a special announcement about an event that's going to happen on Sunday, January 4th, and I'll give you all the information on that in this week's podcast episode. So, sit back and listen in. Unless you're one of those crazy individuals who listens to podcasts while you're biking, running, weightlifting, driving in a car, doing jumping jacks, brushing your teeth, washing the dishes, or taking care of two screaming infants. Not that I would know what that's all about.

Listener Q and A. So in this week's Listener Q and A, Tony from Virginia wrote me and asked, how quickly is fitness actually lost when an individual stops training?

And there's a lot of research that's been done on what happens to your skeletal muscle enzymes or your VO2 max, your oxygen capacity, when you stop exercising after you've been engaged in a routine for some time. But two studies in particular have been around for a while. I'm not saying that they're the best studies on the planet because they've been around a while. Sometimes old research isn't quite as good as new research. But there's one study done in 1985 called Metabolic Characteristics of Skeletal Muscle during D-training. And this study was done on swimmers. And there's another study called Interrelationships between Skeletal Muscle Adaptations and Performance as studied by D-training and re-training. And that study was actually done in 1979 And what these studies looked at was VO2 max, which is tested in exercise metabolic tests that I'll actually talk about a little bit later on in this podcast. Cardiac output, so how much oxygen your heart is actually getting to your muscle tissue. Skeletal muscle capillarization, which is basically a word that indicates how well your muscles are actually saturated with vessels to deliver blood. And then aerobic capacity of the extremities, particularly the arm and the leg muscles.

And what was found was after about seven days of detraining, the muscles aerobic capacity declines by about 10 to 15 percent.

And this was indicated by a drop in the activity of mitochondrial enzymes. And these are the enzymes in your cell that are responsible for taking oxygen that you breathe in and converting it to energy. And actually the concentration of those enzymes starts to decline as little as 48 hours after you stop exercising. That means that if you're sedentary or you sit around for two days after you stop exercising, you can begin to lose a little bit of the oxygen utilizing capacity of your cells. Now, the other thing that can change is the actual ability of your body to deliver blood to the muscle fibers. And studies observed that this decrease was around 10 to 20% within anywhere from 5 to 12 days after exercise stopped. And so we'd be looking at an average of just under to a little over a week, maybe almost two weeks, where you're actually going to start to see a decrease in the amount of blood that's actually delivered to your muscle. Now, some of the other things that happened during that same length of inactivity during that 5 to 12 day period of time, where there's a little bit of a decrease in cardiac output, which is how well your heart is able to actually pump blood during a maximal effort. And so your heart's not only putting out less output, but there's also less blood getting to the muscles, period. And so you're getting a little bit lower oxygen delivery, you're getting a little bit less metabolic activity from exercise, and if you're an athlete, for sure, a pretty significant loss in performance if you're taking a layoff of more than about five to seven days. That's not to say that there's not a place in your program for rest and for recovery. It's very necessary. But what you want to realize is that repeated bouts of inconsistent training can actually do quite a bit of damage. I don't think many people actually realize that they can start to see a decrease in their oxygen capacity after just a couple of days of not training. And that's really one of the things that I make sure to do when I'm writing out training programs for the people that I work with. For example, if I'm writing out an online training program to deliver to someone, I make sure that there are rest days in there, and that there are days where some of the workouts are easy, and days where some of the workouts are hard. But basically, it's stacked so that you can keep coming back over and over and over again to get your exercise sessions in without injuring yourself, without overtraining, and without experiencing a loss in activity that can cause some of these detraining adaptations to occur. So, great question, Tony. And if you have a question, email me ben at bengreenfieldfitness.com or you can simply leave a comment in the show notes for the podcast that you may have a question about in the blog posting that you may have a question about. And that way, I will not only get a chance to respond to your question, but also some of our other listeners may be able to pipe in. So that's this week's listener Q&A.