The 4-Minute Workout: Reality or overly ambitious research conclusion?

A lot more people, including myself, are talking about minimalist training for endurance sports. I wrote in a previous blog how I adapted and successfully used high-intensity intervals to structure my training to post a Boston marathon qualifying time.

An eye-catching article ran in the New York Times’ wellness blog a couple weeks back with the headline “The 4-Minute Workout.” It opened by saying, “Thanks to an ingratiating new study, we may finally be closer to answering that ever-popular question regarding our health and fitness: How little exercise can I get away with?”

With more and more people feeling the time squeeze, and with increasing evidence pointing to the negative health consequences of sedentary lifestyles, this is a valid question. The article went on to reference the positive findings of a recent study published in the journal PLoS ONE, which showed that a single bout of four minutes at 90% of maximum heart rate performed three times a week elicited similar improvements in VO_2max, blood pressure and fasting glucose to that of a four by four minute protocol. 

This sounds great! Why don’t we all just cut down on our training time?

I’m not one to shy away from pointing out the shortcomings when it comes to the media accurately reporting on scientific research. But this time it’s a classic case of the researchers overgeneralizing the research findings beyond the studied population. (There is also a pretty big glaring overreach by the NY Times article – both exercise protocols included a 10 minute warm up and 5 minute cool down. So, if you’re really looking at TOTAL TIME for the workout, it would be 19 minutes, NOT 4 minutes.)

Let’s take a closer look.

In the methods section, the authors describe the study participants:

“Twenty-six inactive but otherwise healthy overweight men [my emphasis] (BMI: 25–30, age: 35–45 years) were recruited for this investigation at St. Olav's hospital, Trondheim, Norway (study period: 05.01.2009–03.04.2009).”

**Note the subjects were exclusively young/middle-aged MEN.**

Later, in the discussion section where the authors interpreted the study results, they say:

“The present study demonstrates that a relatively intense stimulus administered only once and for a relatively short duration can substantially improve VO_2max and work economy. A single bout of 4-minute interval training three times per week will not solve all lifestyle-related problems for people already obese or overweight, and it is not the only solution for inactive persons with a BMI below 25. However, brief interval training can have a central role in public health and lifestyle medicine initiatives, in addition to changes in nutrition and other, less intense physical activity [my emphasis].”

**Despite the known hormonal differences between men and women when it comes to responding to high intensity training, the authors still apply their findings to ALL individuals, rather than to just MEN, which was the study population.**

The study did include a section on limitations, but failed to mention anything on this, and later concluded:

“Our study demonstrated that slightly overweight and healthy individuals [my emphasis] only required brief, duration bouts of exercise with good effort three times a week, to produce large increases in VO_2max and work economy and reduce blood pressure and fasting glucose levels.”

As researchers (and I include myself in this statement) we have an obligation to accurately describe and communicate a study’s findings. When this fails to happen, misinformation is only compounded down the line (especially in the popular media), which doesn’t help matters for the average American trying to make heads or tails of what they should be doing.

How exercise can wreak havoc on your body

We endurance athletes and fitness enthusiasts are in a perpetual state of more, more, more. We're constantly testing ourselves and pushing our bodies to the max.

But, what does this actually do to the body?

There has been quite a bit of conversation in the media and scientific literature about the diminishing returns associated with exercise. Not enough is associated with a range of health and chronic disease issues, while too much can be just as harmful to the body. In previous posts I've written about some of the cardiovascular risks associated with prolonged endurance exercise.

In lieu of this month's regular "Monthly Reading Roundup," there was really one major article I wanted to share. Why, because it takes a detailed and comprehensive look at what exactly a hard workout, marathon, or triathlon does to your body's lipids, hormones, enzymes, and major organ function, like your kidneys.

Fitness expert and Ironman triathlete Ben Greenfield undertook his own personal experiment to test the damage that back-to-back triathlons caused on his body. A few weeks ago he did both the long-course (half Ironman distance) Wildflower Triathlon and the Olympic distance in one weekend; one race on Saturday, the other on Sunday. He had comprehensive blood work done a couple days before the races, and then again afterwards.

The results were both fascinating and scary, especially since my training protocol probably isn't too far off from what he does.

By far, the most concerning aspect is the huge rise in cortisol and inflammatory biomarkers. He writes:

"Yes folks, that’s nearly a seven-fold rise in inflammation. In other words, this type of brutal event creates a complete inflammatory firestorm in your body."

And the biggest issue isn't necessarily producing some inflammation following exercise (which is a good thing in terms of recovery and muscle development), but the cumulative effect:

"The problem is that in the absence of proper recovery, round after round of this acute inflammation can eventually become chronic inflammation, and that is when lack of blood flow to tissue, poor mobility, and risk for chronic disease or serious injury set in."

 He sums up by saying:

"You need look no further than my cortisol levels, TSH, insulin, testosterone, growth factor, creatinine, blood urea nitrogen, white blood cell count, and liver enzymes to see this to be true.

And heck – I actually take care of myself pretty darn well. I sleep 7-9 hours, eat a healthy diet, meditate, and avoid excessive training. Just imagine what someone who doesn’t do all those things looks like.

But I’ll be the first to admit that despite the healthy measures I take, I’m brutally beating my body up with the sport I’ve chosen (triathlon), and if you’re reading this, you probably are too (Crossfitters – you don’t get off that easy – I’ve seen hundreds of these blood panels and you have the same issues)."

So if you're an endurance athlete, or you simply exercise frequently and beat up your body, this article really shines a spotlight on the delicate balance between performance and health.

It's a very detailed article, but well worth the time. Click here to read.

Beating the heat at the North Face Endurance Challenge

It was going to be a hot one. The forecast for the weekend was for low 90's, and, of course, the wonderful humidity that the DC area is known for.

But, that was one of the last things I was thinking about when a friend of mine asked me to join her marathon relay team for last weekend's North Face Endurance Challenge, two days of trail runs ranging from a 5k all the way up to 50 miles.

My first triathlon of the year (Philadelphia) is only a few weeks away. So, heading into the event my mindset was to treat my leg of the marathon relay - a quarter of a marathon, or 6.55 miles - as a litmus test, much like I did for Cherry Blossom. Only this time the distance was more specific to what I'll see up in Philly, which will be a 10k (6.2 mile) for the run part of the triathlon. 

The exciting part about the race was that it was something new - a trail race. And even though the forecast was for hot and humid, I was shooting for six minute miles. It wasn't too long ago I was playing multiple soccer matches over the course of a weekend in the dead of summer when temperatures were well into the mid 90's. The heat would be tough, but I knew it wasn't anything my body hasn't experience before.

The start of the marathon relay wasn't until 11am, which meant a fairly regular morning. I was able to sleep a little, wake up at a decent time, and have a pretty normal breakfast (and of course coffee - which I usually don't have before early morning races, though there is some pretty strong evidence suggesting a performance benefit from consuming some coffee before exercise).

This was my first experience as part of a relay team and one of the hardest parts was simply the downtime. Having to arrive for the start of the race, but then wait two and a half hours to actually run was something very new. Though, I couldn't complain about spending some quality lounge time in the shade, just relaxing at the park where the run was held. It sure would've been nice to have a book though.

Every so often I would stand up to move around a bit and loosen my legs. After about 90 minutes since the race started, I made my way closer to the start/finish line (which also served as the transition area for the relay teams) to keep an eye out for our first runner, James, who was doing the first two legs. He came in a little under two hours (not bad for his first race!) and our second runner, Kim, was off.

Now it was time to get focused.

After some short warm-up efforts, I finally felt my mind had switched from relax mode to race mode. I didn't want to overdue the warm-up with the heat, but a solid 15 minutes and I felt ready. I kept anxiously checking my watch, counting down the minutes until the approximate time I thought I'd see Kim come towards the transition area.

And before I know it she rounded the corner and comes into the transition area. We quickly exchange the timing chip strap fastened to her ankle, and I'm off...

I race out onto the course like I was trying to win. The first mile was all about getting accustomed to running on something other than pavement. I make it onto the trails every now and again, but not often enough to remember how much extra energy you need to focus and stabilize yourself on the uneven ground.

The next 4.5 miles was a mixture of paved pathway, packed gravel pathway, and packed dirt trails through the woods. Though I was trying to keep as fast a pace as I could, I really didn't have much of an idea what it was - I was just going based on feel. There were no mile markers, and I don't race with a GPS watch. The aid stations provided some guidance, but there were only two of them, spaced about 2.5 miles apart.

So, I decided to not even look at my watch and just run. There's something about running through the woods that feels so natural, so pure. I blew by the first aid station without taking anything and was really just trying to pass as many people as I could. I felt my pace slow just a little bit, which I wasn't too worried about because of the heat. I knew it would happen.

I ran at pretty close to max effort. I figured, it's a short race, why not push it. (Though, I wasn't thinking about how I might feel the next day, which I spent completely wiped out with zero energy -  something that I've never experience after a race).

I felt myself getting hot and thirsty, and thankfully I came up on the second aid station. I grabbed two cups, threw them back, and kept on going. It was all about getting to finish line at this point - as fast as I could. I tried to take in as much of the scenery as I could, but before I knew it, I was closing in on the finish area. To make things more fun I had a nice dual with someone to the finish. It's always fun to sync up with someone at some point during the race. Rarely are any words spoken, but you're both taking jabs trying to go a little faster.

I crossed the finish line and my hands immediately went to my knees. I quickly grabbed one of the ice-cold water bottles and squirted about half of it on my neck. Man that felt good. I took a glance at my watch and saw 39 minutes - not too bad at all! I'll take a 6:06 in 90 degree heat any day!

Our relay team did pretty well - finished 22nd out of 81 total teams.

I was also really happy with how I ran, especially considering the heat and that it was my first trail race. I was even more stoked when I actually saw my chip time results, which were posted Sunday evening. I, of course, kept my time with my watch, but I was shocked when I saw how my time stacked up with the field. I compared my time with those who ran the stand-alone 10k.

With my pace, I would've placed first in my age group had I run the 10k, and fourth overall.

Well, I guess I'll just need to put that race on the calendar for next year...

Endurance Sports and Heart Health (Part II): What are the benefits?

This is the second part in a series of posts on endurance sports and heart health.

2,466,115,200. That's how many times my heart will beat if I live as long as the average American is expected to (78.2 years). (My wife says it better beat for longer.) My resting heart rate is about 60 beats per minute. That's a fascinating number to think about. For almost eight decades my heart will supply my entire body (and itself) with the oxygen it needs to survive, and never stopping. 

When it comes down to it, the heart is a relatively simple organ - essentially a four-chambered pump with some tubing going into it and coming out of it. But of course the devil is in the details. Over the course of more than 2 million beats, there is a lot of opportunity for things to go wrong, and many times these things are the result of accumulated issues over time.

As I discussed in the first part of this series, with endurance exercise, there is a fine line between performance and pathology - something referred to as the "grey area" in the scientific literature. There are risks when it comes to endurance sports. But risks can be managed and risks must also be viewed in the context of benefits (it's all about optimizing). 

In this post I discuss some of the benefits of endurance sports and regular exercise, particularly from a physiology perspective, as well as a public health standpoint. But I close with some cautions about maximizing exercise while neglecting other areas of daily life that contribute to heart disease and heart issues.

Popularity of Endurance Sports is Increasing

Endurance sports, such as half-marathons, marathons and triathlons, are becoming more and more popular. The previous post in this series showed the increasing level of participation in USAT-sanctioned triathlon events. Half-marathons and marathons held in the U.S. show a similar trend. Not only are there more races, but more people are participating. For example, according to Running USA, a non-profit that tracks trends in U.S. distance running events, the number of marathons in the U.S. more than tripled between 1985 and 2011, from 200 events to 720 events.

Active.com, an online community for sports and event registration hub for a variety of activities (including running, cycling, triathlon, and more), revealed similar increases based on race registrations between 2008 and 2010. During these three years, marathon registrations increased 203%; half marathons rose 154%, 10K events rose 155% and 5K events rose 144%.

Why is This a Good Thing from an Individual Health Perspective?

Your heart is a muscle, and like other muscles, it responds to stimuli like exercise. It can grow stronger and increase in size similar to other muscles in our body after periods of exercise. And generally (and up to a point), the more exercise, the stronger, more efficient, and sometimes larger the muscle. Endurance activities markedly improve the efficiency of your heart, increasing stroke volume (or the amount of blood pumped by the heart with each beat) and thereby decreasing the number of overall beats needed.

Other markers of heart health have also been positively linked with endurance exercise, such as lower blood pressure and increased HDL cholesterol.

There is also evidence to suggest that exercise plays a strong role is energy partitioning, or the type of energy (such as carbohydrates or fat) our body preferentially burns for fuel. One study of 55 years old women found a more than 9% increase in energy derived from fat after 12 weeks of endurance exercise training.

The weight-bearing movements of regular exercise and strength training support bone health and improve longevity, particularly as people age. Exercise is also associated with lower stress levels, higher energy levels, and overall positive mental health.

Not a bad list of benefits.

Why is This Essential from a Public Health Standpoint?

Physical inactivity is becoming a new norm and the trends don't look promising. A recent review from researchers from the University of North Carolina looked at trends of metabolic equivalent hours (just a fancy way to show the amount of exertion by your body doing different activities) from 1965 to the present, and also projected trends through 2030. Between 1965 and 2009, MET-hours per week decreased by about half (235 to 160), and they are projected to decrease to roughly 126 by 2030. You can see the trend in the graph below, which traced MET-hours in several different areas, such as physical activity during work, transport, domestic activities, and leisure time. The black line is the average hours per week of being sedentary.

The rising trend from 2010 to 2030 represents one of the major public health challenges we face. 

 

What These Trends Don't Tell Us  

Even though registration and participation levels in endurance activities, such as triathlon and marathon, are increasing for a range of age groups, a couple things to remember.

First, this is still a relatively small proportion of the overall U.S. population, which is almost 315 million. From a sports, competition, and individual health perspective, increasing participation is a great thing. For people like myself, it provides a great opportunity to continue competing, setting and working towards new individual goals, staying in good overall health (though my third point mentions another counter-argument to this), and traveling to new and interesting places. However, one must keep this all in perspective that we're still talking about a fairly exclusive cohort of people.

Second, inequalities, particularly in regards to access, are major issues. Opportunities to participate in physical activity pay huge dividends with individual physical and mental health, population health, and create millions of dollars of health care cost savings annually. But, not everyone can afford a gym membership; or can safely walk to a park; or can spare the $120 marathon registration or the extra 30 minutes a day to train. The challenge is to celebrate record numbers of people taking on the endurance challenges of running, triathlon, cycling, etc, but to also ensure environments are conducive to regular physical activity for everyone.

Third, all the effort put into exercising everyday could be for naught if you spend hours sitting for the rest of the day. A recent review examining the link between sedentary time and diabetes, cardiovascular disease and cardiovascular and all-cause mortality in adults older than 18 years of age found that "higher levels of sedentary behavior are associated with a 112% increase in the RR of diabetes, 147% increase in the risk of cardiovascular disease, 90% increase in the risk of cardiovascular mortality and 49% increase in the risk of all cause mortality." Even more frightening are the results from a recent National Health and Nutrition Examination Survey. The study looked at almost 5,000 adults 20 years of age or older and found "Independent of potential confounders, including moderate-to-vigorous exercise, detrimental linear associations of sedentary time with waist circumference, HDL-cholesterol, C-reactive protein, triglycerides, insulin, HOMA-%B, and HOMA-%S were observed." (emphasis added) This essentially is saying that even if someone exercises in the morning, and the rest of the day is spent sitting, this could have a detrimental effects on risk factors - high levels of triglycerides, higher inflammation, higher waist circumference (a fairly good measure for dangerous visceral fat), etc - for heart disease and other chronic diseases.

So, I come back to this theme of optimizing. Sure there are a lot of health benefits to exercise and endurance training. But at the same time, if you're trying to maximize in this area of your life, and neglect other things (such as diet, stress, amount of time sitting during the day, etc), are you really optimizing for better overall health?

Let me know your thoughts and post a comment below.