How I Program for CrossFit

-1I wrote an in-depth article for the CrossFit Solace blog covering CrossFit programming, with specific emphasis on how I create programming for CrossFit classes in the context of the other classes we offer at Solace (e.g., Gymnastics, Strength, Weightlifting, Mobility, etc.). You can read the full article HERE.

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Joining the Hylete Train Team

I have added a “Gear” section to my Product Recommendations Page and the first addition is the clothing company Hylete. Hylete was founded on three principles: 1) Train to push yourself both physically and mentally, 2) Compete so as to improve yourself, as well as those around you and 3) Live to be healthy in mind, body, and soul. I couldn’t agree more. Even better is that they make great products. It took me a while to find a company whose clothing line I felt comfortable training in, but better late than never. I am also happy to report that I am officially part of the Hylete Train Team which means I am part of a group of trainers/coaches who promote the company and encourage others to train with Hylete. This gets my followers some perks – just click on any Hylete link on my site, create a free account, and use promo code (TRT90UF1W) to get 20% off your next purchase.

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Book Review – Lean Habits


I was sent a free copy of the book Lean Habits by Georgie Fear. Georgie is a registered dietician and professional nutrition coach who co-founded Georgie has a lot of experience working with clients, helping them achieve their weight loss goals and this book is a road-map to undertaking the challenge yourself.

Who The Book Is For: This book is targeted towards individuals that want to eat healthier and/or lose weight, but are struggling with the processes necessary for those changes. Very often people are eating the wrong foods, eating the wrong quantity of foods, unable to control the timing of their foods, unable to deal with food cravings, unable to separate emotional attachment to foods, and so on. For these people, just telling them where they need to be isn’t enough – they need a progression to get them there.

What The Book Gives You: This book gives you 16 habits that will improve your nutrition and enable you to reduce your body fat if you are overweight. Some habits include, minimizing liquid calories, eating the right amount of fat, shaping your social and physical environment, getting enough sleep. Each habit is presented with an explanation of why it is important (incorporating scientific studies where appropriate), as well as one or more progressions to help make that habit become truly second nature.

Where the Book Excels: This book excels in targeting a specific group of individuals. For those that are very far from a healthy lifestyle, specific, gradual changes are needed. Taking the wrong steps, or going too fast can set them back. This book explains how to improve your eating habits step-by-step, recognizing that the time process may be different for everyone. This book also excels in explaining the science of why things do or do not work. It’s done in a way that is accessible to the average reader, but references are given for those science-minded individuals like myself. Not nearly enough books on exercise and nutrition cite the studies they reference, so I was very pleased with how this was handled.

Areas for Improvement: There is very little I would improve about this book. This is largely because the audience is very clear. The book isn’t targeted to everyone trying to lose weight, so the focus is dialed in. One improvement I would have made is to put numerical references after each study that was cited in the text so it could easily be found in the references section at the end. Also, as the book progresses, a number of studies are mentioned, but authors and journals are not given (only the science), so one has to scan the reference list in the back (which is alphabetical by author) and figure out which study it was based on solely from the description of the science given in the text.

My Final Recommendation: This is a book I plan to keep in my personal library, so if you are someone who has been struggling with the proper behavior for healthy eating habits/weight loss, or if you train such individuals, I would definitely recommend this book.

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Paleo Challenge Seminar at CrossFit Solace

Last Thursday I kicked off the CrossFit Solace 2015 “Prelude to Summer” Paleo Challenge with a mini talk on the Paleo diet. It was about 30 minutes and I briefly went over the history of the Paleo diet along with why certain items are excluded (diary, grains, legumes, sugar). Where possible, I presented the science that addressed these aspects of exclusion. In the future, I plan to put together a full, more comprehensive talk on the diet. In the meantime, you can check out a clip from my talk by watching the instagram video below:

Coach/Dr. Hayden @scienceforfitness laying down the paleo law… @crossfitsolace #paleo #crossfit #diet #fitness

A video posted by Chad McDonald (@chadjmcdonald) on

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Artificial Sweeteners Can Promote Glucose Intolerance

The movement away from sugar and towards non-caloric artificial sweeteners (NAS), began over a century ago after recognizing that 1) large amounts of calories could lead to obesity and likely a variety of other health problems, and 2) that large amounts of sugar adversely affected hormone levels (in particular insulin), which could also lead to obesity and a variety of other health problems. Thus, consumers looked to NAS as a way to continue to eat sweet foods and beverages while protecting their health. However, research is beginning to indicate that NAS may not be as harmless as we had hoped.

I posted previously about an interesting study in rats, which examined examined the effects of NAS in diet. The results were fascinating as many of the problems we know to arise from over-consumption of sugar, were also found after consuming the artificial sweetener. If you haven’t read my review, it’s worth a read. Recently, another study was published on NAS, this time by Suez and coworkers. Suez et al., 2014 was conducted in both mice and humans.

The Takehome: Glucose intolerance (high levels of blood sugar), often a precursor to Type 2 Diabetes, has been linked to cardiovascular disease, muscle loss, and a variety of other health problems. In this study, the authors found that the commercial non-caloric artificial sweeteners (NAS) saccharine, sucralose, and aspartame all caused mice to develop glucose intolerance. Further examination of saccharine alone (which had the greatest effect of the three), revealed that this intolerance was associated with a change in gut microbiota (bacteria) populations. Fecal matter with these altered microbiota could be transplanted into healthy mice and cause them to become glucose intolerant. In humans, increased consumption of foods with NAS was correlated (a questionnaire-based study) with impaired glucose tolerance and also an alteration of gut microbiota. Finally, ingesting NAS-continaing foods for 1 week was enough time to show reduced glucose tolerance in some, though not all, humans. In these affected humans, microbiota populations were, as expected, altered, though differently than in mice. Nevertheless, when this fecal material from humans was transplanted into healthy mice, the mice developed glucose intolerance. The results of this study indicate that artificial sweeteners don’t give us a free pass to eat without consequence. Although artificial sweeteners do not raise insulin, there appears to be another route by which they can disrupt blood glucose levels, and that is through modification of the bacterial populations that live in our digestive tract. The bacteria in our digestive tract don’t only affect the processing of sugars and artificial sweeteners as highlighted in this study. In fact, they play many other roles in maintaining our health, so it’s quite possible that consumption of artificial sweeteners may negatively impact our health in even more ways than we have yet to realize.

The Experiment:

  • 10-week (young adult) C57/BL6 mice were given one of three NAS in their drinking water: commercial saccharin, sucralose, or aspartame. Control mice were given either water or water with glucose or sucrose. Note: commercial NAS typically contain large amounts of glucose (~95%) and only small amounts of the artificial sweetener (~5%). The investigators matches these ratios.
  • Fecal mibcrobiota composition was assessed in mice through rRNA gene sequencing.
  • Fecal matter was removed from mice and cultured in tissue culture dishes to examine direct effects of NAS on microbiota growth.
  • The effect of NAS in humans (381 non-diabetic males and females, mean age of 43 years old) was assessed through a food frequency questionnaire.
  • 7 humans (5 males, 2 females) who do not normally consume NAS were given NAS-containing foods (at the FDA’s maximal acceptable daily intake levels) for 1 week, after which glucose intolerance and gut microbiota were assessed.

The Results:

  • After 11 weeks, the three groups that drank commercial NAS all had marked glucose intolerance (higher than normal blood sugar levels).
  • The greatest intolerance was found in mice who consumed commercial saccharine.
  • In mice who were on a high-fat diet (to simulate obesity), glucose intolerance from commercial saccharine ingestion was greater than from glucose ingestion.
  • As with commercial saccharine, a lower dose (FDA acceptable daily intake adjusted to mouse) of pure saccharine, also resulted in glucose intolerance in mice on a high fat diet.
  • Fasting serum insulin levels and insulin tolerance were similar in all mouse groups, regardless of diet.
  • Mice drinking saccharine had a fecal microbiota profile different from their starting profiles and from the profile of all control groups (including a group that drank glucose). Profile differences were present even in mice that were on a high fat diet.
  • Gene pathway analysis indicated that the microbiota profile in saccharine-fed mice had gene profiles for enhanced sugar breakdown/fermentation activity. These profiles were previously associated with obesity in mice and humans; overabundance of Bacteroides and under-abundance of Clostridiales.
  • Fecal matter isolated from mice and treated with pure saccharine yielded similar shifts in the microbiota profile and transplanting this altered fecal material into normal mice resulted in their developing glucose intolerance.
  • In humans, NAS consumption was significantly correlated with higher fasting blood glucose, glycosylated hemoglobin (indicates higher than normal levels of blood glucose), and higher glucose intolerance (as measured by a glucose tolerance test).
  • In humans, NAS consumption was significantly correlated with differences in microbiota profiles.
  • In 7 humans given NAS-containing food for 1 week, all developed a poorer glucose tolerance as compared to before they started consuming NAS-containing foods.
  • Fecal material from humans who consumed NAS-containing food for 1 week and developed impaired glucose tolerance was transplanted into healthy mice and resulted in these mice developing glucose intolerance.

The Limitations:

  • Although very often a good model for humans, mice are not humans, so differences may exist where the initial mouse data is concerned. However, the pairing of human data with mouse data in this study makes this much less of a limitation.
  • After seeing the greatest glucose intolerance effect from saccharine, the authors do not further examine effects/mechanisms in mice using sucralose or aspartame. We therefore do not know if the different sweeteners behave any differently beyond impairing glucose tolerance.
  • Insulin levels appear to be unaffected by NAS (as expected), so the exact mechanism of intolerance remains somewhat unclear. We know gut microbiota are involved, but not exactly how.
  • Food questionnaires are noted for being inaccurate as participant reporting is often inaccurate despite the participants’ best efforts.
  • In humans, the microbiota profile differences resulting from NAS were not identical to those found in mice and were also different human-to-human. This suggests that the effects may vary substantially from person-to-person.
  • The human study where NAS-containing foods were consumed had a very low sample size and an unequal distribution of men and women. This would generally be considered “preliminary” data that could be used to support a larger study.
  • In the human study where NAS-containing foods were consumed, the types of NAS consumed were variable, so any differences among them could not be examined.
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Video Post – Clip from “Health & Fitness During Aging” Seminar at UCONN

Below is a video clip from my recent seminar at UCONN. The audience was older and the seminar therefore dealt with health and fitness during aging. It examined, from a scientific perspective, the theme of death and rebirth at the organ and tissue level and how these processes are influenced by modifiable lifestyle factors such as nutrition (calories, fat, carbohydrates, salt) and activity (walking, running, weight training). For more information on my seminars, click the Seminar tab on the menu.

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Creatine Supplementation Can Boost Testosterone

Creatine is an organic acid naturally found in vertebrate muscles and it is arguably the most extensively studied supplement on the market. A variety of studies indicate that supplementing with creatine can enhance athletic performance, endurance, and muscle growth. A previous post of mine goes deeper into creatine, its mechanism of action, and the studies that support its effectiveness. If you haven’t read it, check it out now. In this post I add another potential role for creatine supplementation as indicated in Arazi et al., 2015: the ability to raise testosterone levels. Testosterone is a hormone, produced largely by the male testes, that plays a major role in building muscle (it is therefore said to be anabolic). As such, this study is of immediate interest to men who are interested in getting bigger or stronger.

The Takehome: Both 5 and 7 days after creatine supplementation, men who were resistance training (lifting weights) had significantly higher testosterone levels than they did at baseline and also higher levels compared to those who did similar weight training, but took a placebo instead of creatine. Creatine supplementation also reduced cortisol levels relative to baseline at 5 and 7 days. High levels of cortisol are “catabolic” in that they can lead to tissue breakdown (muscle loss), inefficient tissue repair, and a variety of other processes that hinder growth and recovery of body tissues. So, while previous literature assumed creatine’s main route of action was through restoration of muscle energy reserves, this study indicates there may also be a systemic response through the upregulation of anabolic hormones (testosterone) and the downregulation of catabolic hormones (cortisol).


The Experiment:

  • 20 active males (mean age of 20 years old).
  • Baseline levels of markers were taken: testosterone, cortisol, heart rate and blood pressure.
  • Participants were given 5g of creatine (or dextrose as placebo) 4 times daily dissolved in grape juice.
  • Creatine or placebo was ingested morning, mid-day, afternoon, and before sleep.
  • 3 sessions of resistance training were given (days 3, 5, 7).
  • 3 sessions were conducted to test for the above-mentioned markers (days 4, 6, 8).

The Results:

  • At both 5 and 7 days, resting testosterone levels in creatine supplemented individuals were significantly higher than their baseline levels.
  • At both 5 and 7 days, resting resting testosterone levels in creatine supplemented individuals were higher than placebo supplemented individuals.
  • At both 5 and 7 days, resting cortisol levels in creatine supplemented individuals were significantly lower than their baseline levels.
  • Blood pressure and heart rate levels were largely unaffected by creatine supplementation.

The Limitations:

  • Only men were used and they were fairly young, an age when testosterone levels are already fairly high to begin with. It is unclear if similar results would be found in women or if the same results would be found in older men.
  • The sample size (10 participants per group) is low.
  • We do not know if the changes in testosterone and cortisol levels will be maintained throughout longer periods of creatine use.
  • The exact form of creatine used (i.e., creatine monohydrate) was not listed in the methods.
  • This is just one study. More studies are needed to confirm these findings.
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A Recap of My Recent Strength Cycle

I recently tested a couple of strength cycle variations and wrote up a recap of how things went on the CrossFit Solace blog. If you are interested in balancing strength cycles and conditioning in your CrossFit training, I encourage you to have a read. To access the article CLICK HERE.

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Refocusing My Efforts – Subscribe to My Newsletter

Since I launched Science for Fitness, the regularity of my posts has been fairly frequent and over the past several months new posts were going live nearly every week. This is a lot of content and I’ve been thinking about how much is too much. I know some of my readers have had a hard time keeping up, so that’s one issue. Another issue is that the posts take time, especially if they are to be accurate and of good quality (and I don’t want to post anything that isn’t). The risk of losing quality when you ramp up the quantity of your material was impressed upon me recently when I came across a review of the Paleo literature. My previous post on this site addressed the problems with this review, so if you haven’t read it, check it out. I don’t want to succumb to the kind of problems this review had.

Another consideration is that I want to refocus my efforts a bit. There is more to Science for Fitness than just my articles. There are of course the clients I train that need my attention, but I also need to spend more time working on seminars that I will be giving, as well as on a book that I am trying to put together. What this means is that the frequency of posts to will drop a bit. You will still see at least 1-2 posts per month, but posting dates will be variable. This means that the best way to keep track of what’s going on is to sign up for my monthly newsletter (on my homepage). This will go out at the beginning of each month and recap everything from the month prior, so you won’t miss a beat.

Thanks for reading,

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Quality vs Quantity: A Paleo Review That Doesn’t Quite Add Up

Not too long ago I came across Led by Dr. Greger, the organization’s goal is to “present you and your doctor with the results of the latest in peer-reviewed nutrition and health research, presented in a way that is easy to understand.” We certainly need more people out there doing this. The videos the organization puts out are very slick (as you will see below in a moment) and it’s a format I’ve been considering adopting for quite some time. However, I soon noticed that videos were being released every other day and they were each discussing the primary literature (scientific studies). It takes time to read and interpret scientific studies. I was puzzled. And then I came across one of the organization’s videos on Paleo research. The video is below, give it a watch:

The video threw me for a loop because it was espousing things I had understood to be different. In short, I felt the data wasn’t being interpreted properly. This happens all the time in the popular media when they summarize science, but here a doctor was interpreting (or at least speaking the interpretation) and citing the actual studies. So, I went through the article piece by piece and here is what I found:

  • At 1:10: Here Holt et al., 1997 is referenced and in the video’s bar graph a serving of meat was shown to increase insulin the most. But this isn’t what the study showed. As seen in Table 4 of the study, the beef insulin came in at 7910 pmol(min/L) and the apple came in at 8919 pmol(min/L). The study showed the apple raised insulin more than the beef.
  • At 1:37: Here a graph is shown indicating that beef causes the same insulin spike as pure sugar (glucose). But the study isn’t cited, so I don’t know where it comes from. But if we look back at the Rabinowitz et al., 1966 paper which is cited in the very beginning of the video, we see a lot of data on this – data that actually looks at the insulin levels after various times post-ingestion. This data does not indicate a similar insulin spike between meat and glucose. In all the graphs shown in Figures 4&5, insulin levels during the 1st two hours after ingestion are greater for glucose than meat (click to see an example here).
  • At 3:37: Bueno et al., 2013 is cited comparing a low-carb diet to a low-fat diet is cited to indicated that dropping carbs does not lower insulin. But this is a Meta Analysis study. It is collating data from many studies and the “low-fat” groups are not necessarily high carb diets and the types of carbohydrates consumed is also not accounted for.
  • At 4:00: The Smith et al., 2014 study is cited to close the video. In the video we are told that the paleo diet worsened LDL cholestrol (“bad cholesterol”) and reduced HDL (“good cholesterol”) in individuals who were exercising (CrossFit). The narrative has now, only at the very end, switched away from insulin, to cholesterol to address an interaction effect with exercise. I’ve posted numerous times about how the cholesterol literature is riddled with problems, so I won’t go into it again. But I will note that this study is problematic for another big reason – the participants didn’t strictly follow a Paleo diet as indicated in the study’s methods. For a write-up on this, check out this blog post by The Russells.

As you can see, the above video is problematic. There is some interesting data in the video, such as the fact that Holt et al., 1997 saw white pasta spike insulin less than meat, and the fact that vegetarians tend to have lower insulin levels (despite eating more carbs than non-vegetarians), but there are many key points that just don’t add up and the viewer is given the impression that the “case is closed” when we are really still putting the pieces together.

I posted several of my above-mentioned corrections to the video in the comments thread (because of course maybe I was missing something), but didn’t get any response. I then suspected that Dr. Greger wasn’t reading all the social media himself and that he probably wasn’t reading the actual studies himself either. It made sense, because for me to really pick apart one study and make sure I get it right, it takes several hours. In this video alone, there were more than 5. He must have been using a team to go through the studies.

It turns out I was right. Earlier this month February Dr. Greger put out a call for “fact checkers” to work freelance for the organization. It’s also revealing that he tested applicants on their fact-checking skills and during the first round everyone was under 80% (out of 100%). has a great mission statement, and many of their videos are great, but interpreting scientific studies is hard, even for the scientists. It’s very demanding and requires a lot of training, thought and focus.

As scientists and doctors we have to remember this and not get caught up in trying to give the public large quantities of information covering all topics all the time. Quality suffers when quantity goes up. Not to mention, our understanding of science (e.g., nutrition, health, fitness), does not change every time a new study comes out. It’s an aggregate of studies over time, shown to be repeatable, that have meaning and putting this message together requires quite an enormous investment of thoughtful consideration.

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