Saturday, May 28, 2016

Performance Metrics

The season is well underway and you have been following a regimented training program. You often wonder "How am I doing?" "Is suffering through the training doing anything?"


Aside from recording and tracking “personal bests” (your PR or personal records) on your standard routes, how can you monitor improvement over the season to assess the effectiveness of your training program and give you the numbers to decide if you are getting better or if changes should be considered.

Before we discuss specifics, I want to emphasize the importance of doing the testing in a way that maximizes the odds of obtaining reproducible results. That is why following PRs on a standard route is not an ideal metric as weather (especially wind) and traffic can have a significant impact on your results. Using an indoor trainer with the same bike and tires will minimize any effect of external and equipment variables from day to day. To maximize standardization, also consider:

  • doing the testing the same time of day – and with the same timing in relation to your last meal. 
  • keeping the same resistance (or gearing) on the trainer from session to session. 
  • keeping the room temperature constant. (A fan is often a helpful addition.) 
  • making note of the timing of the test in your training cycle. Make note of your self assessment of your fatigue level (from prior rides). And, for example, you may always want to to do the testing after a day off the bike. 
How you measure the results is important as well. A power meter will provide the most accurate and reproducible numbers, but a cycle computer (for speed) and heart rate monitor will work as well.

I. Maximum Power (anaerobic sprint effort, watts of power)


In this test you want to measure your maximum power – so it will be short to avoid a fatigue factor or limits from the build up of acidic byproducts in the muscles from a maximum anaerobic effort.

Six seconds of all out effort with resistance set at a point that will allow you to maximize your RPMs without changing gears. From a dead stop, standing, give it your all. Measure your peak watts or top speed achieved (which indirectly reflects power output) on your cycle computer.

  • Duration: six seconds 
  • Resistance (gearing) that you will not top out RPMs 
  • Metric: Peak watts or top speed on cyclocomputer
II. VO2max (maximal aerobic power)

In this test, you want to identify the maximal power you can maintain for many minutes i.e. an effort that is just at the edge of being anaerobic. In this test, if you start too fast (sprint speed), you will be working at an anaerobic pace, build up acidic metabolites, and in the end actually limit your maximum performance. The goal - produce the highest average wattage (or speed on your cyclocomputer) for the duration of the test.
  • Duration: 3 minutes
  • Resistance or gearing that you can maintain for the full 3 minutes (and will not need to downshift to an easier gear near the end.)
  • Metric: average power (or speed) over the entire 3 minutes (monitor splits to assure an even effort)
III. Lactate Threshold (maximal sustainable power)

In this test you will identify the maximum wattage (or speed) you can maintain for up to 1 hour (a time trial performance). Your speed can vary(slowly increase) but at the end of the 20 minutes you should feel you have given your all. It is probably the best measure of overall cycling fitness.

  • Duration: 20 minutes 
  • Resistance – can vary but occasionally, but best to pick a resistance you feel you can maintain for the entire 20 minutes (especially if you are using top speed as your metric). 
  • Metric: 0.95 x average power (speed) for 20 minutes = lactate threshold

As I run across other thoughts on performance metrics, I'll add them here, so consider adding your email to be notified when changes are made.

Wednesday, April 27, 2016

The Mukilteo Diet - a healthy diet (and treatment for metabolic syndrome).

I am a gastroenterologist (living in Mukilteo, Washington) and have been seeing patients with liver and other digestive tract complaints for 35 years.  Over the years I have seen a dramatic increase in the number of patients referred for consultation for the diagnosis of “fatty liver”. 

Fatty liver refers to increased fat in the liver which in turn can cause inflammation and in a few patients lead to cirrhosis or scarring . Fatty liver is associated with a condition known as metabolic syndrome. This condition is seen in pre-diabetes/diabetes as well as in many overweight individuals. However, it can also be seen in individuals who are not diabetic and not obese (normal range BMI).

By some estimates fatty liver now affects upwards of 25% of the population. Fatty liver, diabetes, and obesity overlap in their underlying physiology (abnormal insulin metabolism) and are all impacted (both positively and negatively) by diet. When I explain this to patients, that a change in diet is a simple start to impact the liver fat accumulation, the next question is predictably “what can I do ?” The following is a summary of my answer to them.

Although the traditional dietary approach to treatment of all three conditions has emphasized losing weight, it is not just about weight loss. Carbohydrates, and the insulin release they stimulate, are thought to be the culprit. Thus the source of one's daily calories (carbohydrate versus fat) and when they are eaten during the day are equally as significant as the total daily calorie balance.

The following five factors are important in any healthy diet but are particularly important in a comprehensive dietary approach to weight loss (where they work together with a decrease in total daily caloric intake) as well as in the treatment of glucose intolerance and fatty liver (steato-hepatitis).



I. Caloric Balance – if weight loss is a goal, then you will need to eat fewer calories a day than you will use. It is the mantra that is the basis os all weight loss plans. It is simple to understand and each diet then goes on to explain how you can easily eat less with their program. A negative caloric balance will ultimately translate into fat loss. As there is individual as well as day to day variability in water retention, it may not show an immediate effect on the scale. And when you go into negative caloric balance, the body will slow its metabolism a bit to compensate, so the loss may not be as dramatic as hoped. But in the end if you eat fewer calories than you expend, you will lose weight. If you have achieved your goal weight, then stepping on the scale every morning before breakfast will reinforce that you are remaining on track.
  • If you want to lose weight, eat fewer calories than you expend.

II. When you eat – When you eat your calories is just as important as the caloric balance. You should eat the bulk of your calories early in the day (before 2 PM). Aim for a 25-50-25 split for breakfast – lunch- dinner. Any calories, especially carbohydrates, eaten early in the day are preferentially used by your active muscles during the subsequent 3 or 4 hours rather than being stored as fat (in the liver as well as fat cells) for later use when the muscles are not active (evening, sleeping).

If you do cut back on your evening calories – and for double bonus points focus on a plant based, low carbohydrate meal – you are moving towards an “intermittent fast” as described by Dr. Mirkin. A fast does not need to be a total elimination of calories. His post has references as well as a list of identified benefits.


To quote directly from Dr. Mirkin: "Intermittent fasting" does not mean complete avoidance of foods and drinks. Instead, you markedly reduce your intake of food during certain periods. The benefits of intermittent fasting can be seen as long as you significantly reduce your total caloric intake during those periods (http://www.ncbi.nlm.nih.gov/pubmed/16529878).


Intermittent fasting appears to work by increasing the body's sensitivity to insulin and reducing an overactive immunity, called inflammation (Cell Metabolism, Feb, 2014;19(1932-7420):181–92).



Various programs of intermittent fasting have been shown to:

  • lower blood pressure (British Journal of Diabetes and Vascular Disease, April 2013) 
  • lower cholesterol and triglycerides (Am J Clin Nutr, Nov 2009;90(5):1138-43) 
  • reduce body fat (Int J Obes (Lond), May 2015;39(5):727-33) 
  • lower insulin (Am J Clin Nutr, Jan 2005;81(1):69-73) 
  • lower blood markers of inflammation (Free Radic Biol Med, March 2007;42(5):665-74) 
  • increase speed and endurance in athletes (Med Sci Sports Exerc, April 2016;48(4):663-72) 
A decrease in your evening carbohydrates will directly increase the use of body fat metabolism and use. My blog post “Optimizing The Use of Body Fat As An Exercise Energy Source - train high, sleep low” reviews the physiology and logic. It is even more effective if you exercise just prior to deplete muscle glycogen stores and “force” or stimulate fat metabolizing pathways. The results are clear. The subjects on a post exercise carbohydrate restriction burned 8.7% of their body fat while the control group lost just 2.6%. Both were on equi-caloric daily diets so this was not just fat loss from calorie restriction.
  • Move to a daily 25-50-25 distribution of calories (breakfast-lunch-dinner).
  • Minimal carbohydrates for the evening meal – bonus points for a plant based meal.
  • Maximize the effect with an afternoon exercise session.

III. What you eat (cabs versus fats/protein) and glycemic load – there is a growing body of evidence that a healthy diet (especially if you are trying to lose weight or treat fatty liver or a pre-diabetic tendency) means a decrease in the percentage of total daily calories provided by carbohydrates.

When carbohydrates are absorbed from the intestinal tract, they elevate the blood sugar level which in turn stimulates insulin release from the pancreas. Insulin is required to move glucose (the absorbed form of the carbohydrates) into the muscle cells where it is used for energy or stored (in the form the carbohydrate glycogen or fat). A carbohydrate with a high glycemic INDEX is more rapidly absorbed and the blood glucose rise higher which provides an extra stimulus to insulin secretion. Some foods contain only a small amount of carbohydrate per serving (a carrot is an example) which is rapidly absorbed, so the idea of glycemic LOAD as a measure of the glucose surge makes more physiologic sense as a measure of pancreatic stimulation. Here is a nice summary of glycemic index versus glycemic load: http://www.fammed.wisc.edu/files/webfm-uploads/documents/outreach/im/handout_glycemic_index_patient.pdf
Here is a quick link to a list which compares glycemic index and glycemic load of common foods. http://www.health.harvard.edu/diseases-and-conditions/glycemic_index_and_glycemic_load_for_100_foods

As mentioned, insulin facilitates movement of carbohydrate into muscle and fat cells. And if it is not immediately use by a working muscle, after an evening meal or a bedtime snack, it is converted into fat. To decrease carbohydrate fueled fat production you could a) decrease the total percentage of carbohydrates in your diet, b) eat foods that contain low glycemic load carbohydrates which will decrease the production of insulin to facilitate the movement into fat cells, or c) eat more of your carbohydrates early in the day or just before/while exercising. With vigorous exercise, glucose will move into the muscle cell without insulin (it is insulin INDEPENDENT) and any blood sugar spike is blunted. Thus the idea of glycemic load is less important if carbohydrates are eaten just before or during exercise.

  • Carbohydrate calories should be a smaller part of your total daily calories.
  • Low glycemic load carbohydrate containing foods are preferred.
  • The bulk of your daily carbohydrates should be eaten in morning or before 2 PM.


IV. Exercise – adding exercise to a dietary program adds 3 benefits.

First, it increases the total calories you metabolize during the day. Additional calories expended for the actual exercise period as well as a slight rise in the basal metabolism rate for a few hours post exercise.

Second, while exercising, blood glucose moves into the actively contracting muscles cells without using insulin. And this insulin independent effect blunts the blood sugar spike (and stimulation of insulin release) seen after eating a high glycemic index food.

This New York Times article (http://well.blogs.nytimes.com/2015/01/23/ask-well-the-best-time-of-day-to-exercise/) refers to a study that shows us how to use the timing of exercise to blunt insulin release. In this study, exercising BEFORE eating blunted the negatives of excess daily dietary carbohydrate calories, while exercising a few hours AFTER eating provided a lesser (but still definite) benefit. Exercising before a meal appears to shunt post exercise calories directly into muscles and divert them from fat storage (throughout the body and liver). And as the process is insulin independent, it takes the pressure off the pancreas to provide additional insulin to move the glucose into the cells.

Third, when exercising, you will decrease your muscle glycogen (glucose) stores to provide energy to the muscles. Then, if you limit your post exercise carbohydrates, you stimulate fat metabolizing pathways to refill that glycogen storage deficit in the muscle. This magnifies or leverages the benefits of a low carbohydrate diet to reduce overall body fat stores.

The exercise can be as simple as an afternoon walk – which only has to be 20 minutes to be of benefit - or as complex as a rigorous training program .(http://cptips.com/hit.htm). There are a number of programs out there – here is a short video: http://www.nytimes.com/video/health/100000001515630/the-20-minute-workout.html  And a recent study shows that even a few minutes of intense exercise in a 10 minute exercise program will provide these benefits. So lack of time is not an excuse.

  • 20 minutes of exercise a day provides further health benefits (magnifying the positives of a low carbohydrate diet).
  • Exercising BEFORE a meal is a plus.


V. Microbiome (colon bacteria) – The bacteria in our colon were traditionally considered as “outside our body” and irrelevant to health. But we now understand that products of bacterial metabolism of the food we eat are actually absorbed and impact metabolism. Here is an intriguing article that illustrates the point. http://www.nytimes.com/2013/09/06/health/gut-bacteria-from-thin-humans-can-slim-mice-down.html.  And here is another easy to understand explanation: http://www.drmirkin.com/nutrition/two-clues-to-the-obesity-epidemic.html
And the colon's bacterial balance will change in a matter of days based on our diet – http://nutritionfacts.org/video/how-to-change-your-enterotype/

I feel certain that we will find that colon bacteria play a significant role in the development of fatty liver and glucose intolerance or pre-diabetes - most likely via the production of intermediate chemical products from the metabolism of the foods we eat. And that it is the microbiome that is involved in the weight loss benefits we see with a shift to a plant based diet.

  • No artificial sugars.
  • Decrease the amount of meat in your diet relative to plant based protein sources.

To summarize, these are the components of my Mukilteo diet. And if you want a go slow approach, I put them in what I think is their relative order of importance.

  1. Move towards a daily 25%-50%-25% distribution of calories (breakfast-lunch-dinner).
  2. Decrease the percentage of daily calories from carbohydrates – low glycemic load foods preferred.
  3. The bulk of daily carbohydrates to be eaten by 2 PM. Minimize carbohydrates in the evening meal – bonus points for a plant based dinner.
  4. As protein is increased, increase the amount that is from plant based protein sources.
  5. 20 minutes of exercise a day will magnify the benefits of a low carbohydrate diet.
  6. If you want to lose weight, eat fewer calories than you expend.



Thursday, April 21, 2016

Optimizing The Use of Body Fat As An Exercise Energy Source - train high, sleep low


Muscle fiber contraction is powered by ATP – a molecule that contains high energy phosphate bonds. It is the final step in cell energy metabolism being produced via both glucose and fat metabolic pathways. As exercise intensity increases, the percentage of energy derived from glucose metabolism increases while that from fat metabolism decreases.



Traditionally, training to maximize performance (especially at high levels of exercise intensity) has focused on improving the glucose metabolism pathways. Intervals have been the most successful strategy as they stress both the glucose pathways to optimize the use of muscle glycogen as well as stress the cardiovascular system to improve the delivery of oxygen to the exercising muscle (higher cardiac stroke volume, more capillaries to the muscle cells themselves). 







To assure that adequate energy stores were available for the high energy, interval workouts, a key part of all serious training program has focused on post exercise muscle glycogen repletion (replenishment) to get ready for the next riding session.

There have been a number of studies investigating the idea that improving fat metabolism might be another option to improve high exercise intensity performance. These studies limited glycogen availability to the exercising muscle with the thought that this metabolic stress would then “force” the cell to develop more effective (and efficient) fat --> ATP pathways.  And this improved fat metabolism might then add a few extra ATPs of energy at all levels of exertion to provide an edge for the elite athlete. These papers (using carbohydrate restriction as the training stress) did show training adaptations including increased whole body fat oxidation as well as increased activities of oxidative enzymes when compared to training with normal glycogen stores and high CHO availability. However the subject athletes experienced disappointing performance increases.



These 2 graphs might give a better idea of what was hoped. This (top ) graph shows the relative contribution of fat versus carbohydrate to energy calories at exercise intensities up to 85%VO2 max.

And this lower one shows the hoped for increase in fat energy calories from muscle triglycerides mainly (red line) and resulting increase in total energy calories available (blue line), again at all levels of exertion up to 85%VO2max.








This recent paper offers a different strategy to implement a low carb/high fat training approach and, if one looks at their success, a possible explanation as to why previous studies failed to show any benefits from training on a low carbohydrate diet.

As one reads the original study here's a nice analysis in simpler language - the challenge appears quite similar to the issues of using altitude as a training tool (the stress being a low ambient oxygen levels at altitude). Originally it was speculated that the stress of living at altitude (where there is less oxygen per liter of air taken into the lungs) would induce already understood changes in the athletes' blood chemistry to facilitate the releasing of additional oxygen from red blood cell hemoglobin.  (The compound 2,3 DPG, which aids the release of oxygen from hemoglobin, forms when a climber - or athlete - spends 3 or 4 days at altitude.) But when the athletes lived at altitude and continued their high intensity training program, the hoped for performance benefits did not materialize. The reason? Although the blood chemistry changes did occur, de-conditioning was evident in the interval training results as there was not enough ambient oxygen (even when released more easily from the red blood cells) to permit maximal interval intensity and a maximum training effect. The solution?  “Live high and train low”. That provided the "living at altitude" stimulus to form additional 2,3 DPG and maximized the interval training effect as training ("train low") was now being done with a higher ambient oxygen concentration. This combination of “live high, train low” maximized the efficient use of oxygen for high level performance at any altitude.

In the original studies that looked at CHO deprivation as the route to stimulate efficient fat metabolism, the lack of carbohydrates during HIT interval training kept the athlete from maximizing the level of interval intensity (talk to someone who has trained in the South Beach diet - a carbohydrate restricted diet - and they will tell you it is like training with the bonk).  As a result an athlete's personal VO max slowly fell over time as they de-conditioned. The current author's used a hybrid model:  

1) "train high" (with adequate carbohydrate as a muscle energy source) to minimize the interval training dilemma by limiting an athlete's HIT to periods when carbohydrates had been taken on board before the session (and during the ride)

2) "sleep low" (no carbohydrates after the HIT session) to stimulate improvement of the cell's  fat metabolizing enzymes as the athlete's muscle cells work to rebuild post exercise glycogen stores from the body's fat stores. 

They also added the additional stimulus of a low intensity training session in a glycogen depleted state (without glucose supplements) a fat metabolism stress (and as the LIT session was at 65% of maximum activity, a low glycogen or bonk situation, performance was not limited by glucose availability (again, the common complaint of low carbohydrate diets is that one always feels as if they are bonked and cannot perform at any more than 50 – 60% of their VO2max). The specifics of the author's program are outlined in this online analysis.

The finding of an improvement in fat metabolism at 50 – 60% VO@max has been reported before. What is different in this study is:
  • an additional improvement in both the length of time an athlete could maintain supra-maximal cycling to exhaustion trial at 150% of peak aerobic power 
  • as well as an improvement in 10k running performance.


An third observation, an impact on body % fat composition supports a modification of fat metabolism during the low carbohydrate, post exercise period which preferentially metabolized fat to rebuild muscle glycogen stores.  The subjects on post exercise carbohydrate restriction burned a whopping 8.7 ± 7.4 % body fat literally overnight, while the control group lost a measurable, but significantly lower and overall non-significant 2.6 ± 7.4% of their body fat. And both were on equi-caloric daily diets so this is not just fat loss due to calorie restriction. As an aside, this observation could be used to facilitate weight loss with a restricted calorie diet.  In the past the mantra was "eat fewer calories than you are using" (by exercise) and you will lose fat. But this observation suggests that WHEN you eat your calories may be just as important as the total daily calories consumed. Exercise during the day, eat your carbohydrate calories before your daily exercise routine and then switch to a low carb diet in the afternoon/evening and you may increase weight loss.

So where does this leave us?

1) If you are interested in pursuing that extra 1 or 2 % performance edge for a competitive, then this regimen has merits.

Load up on carbs a few hours before and during during your HIT training and cut off your carbohydrate intake when you don't need them (during sleep and low intensity exercise) to maximize the positive adaptive responses in your fat metabolism pathways.

2) If you are doing a multi-day ride, I still favor the use of the post ride window to advantage the replacement of muscle glycogen and minimize the odds of bonking the next day.

3) And if you are trying to lose a few pounds, plan your diet to avoid those evening carbohydrates after an interval training ride.


A couple more articles for those interested:














Tuesday, April 19, 2016

Cycling Performance Tips

Your potential as a cyclist is defined by your genes, your training (to strengthen the cardiovascular and musculoskeletal systems; to help us plan race day strategies), and your nutritional programs that provide the "fuel" to power us for an event or ride.

Our athletic potential is, in the end, limited by our genes. But what we actually will achieve is determined to a much greater degree by the training and the nutritional programs we choose to follow. 


So where does a new rider, committed to maximizing their performance, start?  The first challenge is to get past the anecdotes that are found on almost every training website. These are the recommendations and claims based on personal opinions and "experience" rather than firm factual information.

But "factual" articles can be just as misleading as anecdotes. The positive result in a study of a supplement, or training change, might actually be a placebo effect - a one time (not reproducible) improvement that is not related to the intervention (training program or nutritional supplement) being studied but rather the user's anticipation of benefit and subconscious biasing of a result. One way to minimize the possibility we are seeing result that is a placebo effect is to focus on articles that have been subjected to a rigorous review (generally in peer-reviewed journals) of the study's design and analysis of results. For that reason,  you will notice that many of my references are from PubMed, a compilation of abstracts from peer reviewed studies.

Another question to ask yourself is about the study model. The results of a study done in animals may not transfer to humans, and some interventions which are positive in an animal model can actually produce a negative result when studied in human athletes.

And finally we have the conundrum of a non linear dose-response relationship - that is the concept that "...if a little is good, a lot is better."  Occasionally, while there may be an initial positive correlation with a small dose of an intervention or supplement, as the dose or volume (of exercise) is increased further, these benefits start to fall off. Thus when a manufacturer or promoter uses an article that shows a benefit of a small dose to support a product that has a much higher dose of ingredient, the risk of a loss of effectiveness or even a negative impact increases.

To help you sift through the many claims on the internet, what I'll call "urban legends", it is my hope to collect and discuss performance tips (nutritional, training, and equipment) that are supported by scientific evidence (controlled studies, published in the peer reviewed medical literature), or based on well accepted principles of nutritional physiology. This information will then let you, the reader, decide when and how to apply a particular study or finding to your own unique situation.

It can be a long and tedious search to find those training and nutritional tips which will help you gain a competitive edge. While one always hopes to find that magic shortcut, or unknown supplement, it is more commonly the application of tried and true training basics, not shortcuts, that will get you to your goals. Hopefully this website will point you to the best training (and riding strategies) for you.