Nutrition implications for the aging athlete

In general, our society is becoming more health conscious, which is great! People are living longer and are looking to feel younger as they age. I often work with aging athletes, and older adults to help provide guidance on how they can use different nutrition strategies to help them reach their goals, whether health or fitness related. One of the most common issue these I find older adults face including recovery, strength and body composition changes. If you are over 50 I would encourage you to keep reading!

Sarcopenia

Sarcopinia is the term used to describe the gradual muscle mass loss seen in older adults. We know that in general once you hit age 50, you start to lose about 1% of your lean body mass per year. This is concerning for a few reasons. First, the loss of muscle mass means you will also likely lose functionality, ie you may be unable to lift groceries like you used to. It also can result in changes in balance and stability which may lead to increased risk of falls. Lastly, because our muscle mass is a metabolically active tissue (ie it stores and burns carbohydrates and fats) the decreased muscle mass can decrease the metabolic efficiency and storage of carbohydrates and fats and can lead to development of chronic diseases such as cardiovascular disease or type 2 diabetes. This results in a huge stress on our health care system and therefore is important for us to think about nutrition strategies to maintain our muscle mass as we age.

Why do we lose muscle mass?

It is not known for certain why we lose muscle mass as we age, whether we have a general decreased muscle building and/or increased muscle breakdown or a lower sensitivity for turning on protein synthesis (ie it takes more protein to increase muscle building). Either way, in general this leads us to have higher muscle breakdown than build up, and thus a loss of lean tissue.

What can we do about it?

The first point I want to make is not related to nutrition. It is well known that resistance training is a VERY powerful stimulus of muscle building capacity and aged muscles respond to resistance training similar to young muscles. Resistance training in combination with very easy nutrition changes can help retain, maintain and possibly even build muscle mass in older adults.

 Nutrition Strategies

1. Increase the protein intake

In a westernized country like Canada, we often get enough protein, however I do notice that older athletes or adults may still need to bump up their intake to maximize recovery. The reason for this recommendation is because we know that an older adult will not respond to a 20g dose of protein like a younger person would, and a higher dose of protein is needed to stimulate muscle building. Some older adults experience decreased appetite and will reduce portions, again we need to keep in mind we need more protein to maintain our muscle mass compared to when we were young!

2. Protein quality is important

Research does show that soy protein vs whey or beef protein is less effective to stimulate muscle building. Even though soy is a complete protein (has the same amino acid make up as meat) it seems as though it is processed slightly different in the body. Mainly, the protein in soy seems to be digested slower resulting in less of an increase in amino acid levels in the blood and thus decreased stimulation of muscle protein synthesis. Very careful nutrition planning is necessary if you are an older adult who adheres to a vegetarian or vegan diet.

3. Dairy

Dairy has the amino acid Leucine, which is a branch chain amino acid. It is a potent stimulator of muscle synthesis and can assist in maintaining lean mass. Not only is dairy a source of leucine, but adding a glass of milk to your meal will add about 8g of protein, which actually could be all the changes you need to make to meet the protein needs at your breakfast, lunch and dinner. In addition, consuming dairy products will provide you with calcium and vitamin D to assist in prevention of osteoporosis! Win win right?!

4. Distribution

We talked about the amount, quality and now we get to the timing! If we look at typical protein amounts at each meal of the general population, we typically consume very little protein at breakfast, moderate amounts at lunch and a HUGE portion at dinner. This is a very skewed distribution of your protein and very little protein synthesis occurs until the dinner time, where not all of that protein can even be used and is wasted. Having multiple doses throughout the day at regular time intervals is the best method of feeding and maintain your muscle mass. You also want to make sure you place your protein at appropriate times to ensure adequate recovery from exercise bouts.

5. Supplements

If you are an older adult who is engaging in regular exercise, supplements like protein powder might be common place in your dietary plan. One other supplement that has been shown to have some benefits for older adults is creatine. First we must understand that lifting a weight for 8reps the activity is more intense and it lasts very little time and therefore it will use anaerobic metabolism for the most part, which means that you will be using the phosphocreatine pathway to provide energy along with carbohydrates. The theory is that the more creatine in the muscle, the harder you can train, thus getting a better workout and getting a larger response of muscle strength and growth. It can be used to stimulate your muscle building potential. Research does show that proper dietary strategies + weight training + creatine supplementation can result in additional muscle building, increased strength and also increase in functional movement. Proper dosing is needed to elicit results, and there are a few contraindications for using such a supplement, independent assessment for this supplementation is needed.

As our population ages, it is predicted that at year 2050 a quarter (25%) of the population will be over the age of 65. This may put strain on our health care system, and therefore we need to make sure we do as much as we can to keep our bodies healthy as we age. For more information about how you can keep your body healthy as you age, book an appointment today!

Nutrition for the male endurance athlete

We are back at it again, and this time I want to talk a little bit about nutrition concerns for the male endurance athlete. If you have been following along with my previous blogs (if you haven’t, you should be!), you will recall we discussed how nutrition impacts the health and wellbeing of female endurance athletes, especially regarding stress fracture risk. You can find it here, if you would like to take a look back for a refresher.

For a quick recap, we discussed how endurance running is a huge metabolic demand, meaning it costs a lot to run fast for long periods of time. This can result in accidental under consumption of macronutrients (carbohydrates, fat and protein), energy, and ultimately vitamin/mineral intake, or purposeful restriction of food intake to achieve a desired level of thinness or body shape. Chronic under consumption, whether accidental or not, of both nutrient and energy, can cause some physiological changes in the body and can greatly increase your risk of bone related injuries.

It was typically believed that low energy availability (LEA), in the past known as the female athlete triad, only was a complication females encountered in sport, however it is now known that males also experience negative health and performance effects of LEA. It is possibly harder to detect in males, as there is no clear sign, such as loss of menstrual cycle, however that is why we need to be careful not to miss the subtle signs. In this article we will discuss what happens physiologically with LEA, and its effects on bone mineral density (BMD).

Physiological Changes
Under consuming energy can be a difficult concept to understand because calculations of exercise energy expenditure, basil metabolic rate and even energy intake are difficult to assess. Current research defines “Energy Availability” (EA) as the left over energy to be used for normal physiological processes after accounting for energy expenditure, which is expressed as kcal/kg of FAT FREE mass.

The EA equation= [energy intake- exercise energy expenditure] / fat free mass (kg)

Physiological Changes With LEA
– Decreased metabolic rate
– Increased cortisol (stress hormone)
– Decreased testosterone
– Signs include fatigue and decreased sex drive

Bone Mineral Density
There is ample evidence to suggest that an active individual have higher BMD than sedentary individuals. Within the athletic population swimmers and cyclists tend to have fairly low BMD due to non-weight bearing nature of the exercise. A study by Viner et al. looked at male and female cyclists with lower than expected BMD. The found that 70% had LEA across the entire training cycle, including pre season, competition and post season. This points to the theory that this particular group may have had low BMD due to their LEA. They found that 40% of the participants had low bone mineral density in their lumbar spine, and 10% had low bone mineral density in the femoral neck. The athletes were followed for 1 year and their BMD stayed the same, which is positive. The researchers pointed to their previous interventions of increasing vitamin D & calcium intake and including weight training as a reason for the maintenance of BMD. This provides evidence that a good nutrition and training intervention can help maintain bone strength.

Another study in elite male endurance athletes showed that LEA resulted in low testosterone (although not clinically low) however it did not result in any differences in BMD compared to those with normal testosterone levels. There seems to be a caloric value threshold before we start to see negative health and bone effects. Interestingly, it seems as though women are more sensitive to changes in EA, where we see significant and detrimental effects in heath and bone when their EA reaches 30 kcal/kgFFM/day or below. There is evidence that this occurs at levels of 20-25 kcal/kgFFM/day in a male athlete, although more research is needed to confirm this. This study suggested that because they investigated athletes at ~30kcal/kgFFM/day that this was not enough of a deficit to result in decreased BMD. However, this does not mean you can neglect your nutrition planning because even though their BMD did not change, those with low testosterone had 4.5x more risk of sustaining a stress fracture and had 4.5x more missed training days due to injury.

Main Take-Away:
In elite endurance athletes, 40% of males were found to have LEA. Even temporary low EA increases bone breakdown and decreases bone building, and chronic low EA has long lasting effects on bone health plus many more effects such as mental health and performance to name a few. Therefore, it is essential to stay on top of your nutrition as a part of stress fracture/injury risk reduction.

1. Negative energy balance and testosterone: studies show low testosterone results in 4.5x higher risk of bone injury and had 4.5x more missed training days due to injury
2. NFL players and vitamin D: In NFL players, low circulating vitamin D levels correlated with increased risk of core and lower muscle injuries; players with 1+ fractures had higher rates of inadequate levels of circulating vitamin D.
3. Military recruits with lower serum Vitamin D- correlated with higher risk of fractures

References:
Viner RT, Harris M, Berning JR, Meyer NL. Energy availability and dietary patterns of adult make and female competitive cyclists with lower than expected bone mineral density. International Journal of Sports Nutrition and Exercise Metabolism. 2015. 25, 594-602.

Ruohola JP, Laaksi I, Ylikomi T, Haataja R, Mattila VM, Sahi T, Tuohimaa P, Pihlajamaki H. Association between serum 20(OH)D concentration and bone stress fractures in Finnish young men. Journal of Bone and Mineral Research. 2006. 21, 1483-1488.

Heikura IA, Uuitalo ALT, Stellingwerff T, Bergland D, Mero AA, Burke LM. 2017. Low energy availability is difficult to assess but outcomes have a large impact on bone injury rates in elite distance athletes. International Journal of Sport Nutrition and Exercise Metabolism.

Keto for Weight Loss- Does it work, and is it necessary?

If you have been following along in my past articles, you saw the evidence for whether or not a keto diet is beneficial for endurance athletes. However, I wanted to also share my thoughts and some research on the keto diet for my non-athlete readers. In this article I will discuss why keto may, or may not, be a good choice for you.

 First off, I want to say that keto is likely not meant to be a life-time eating style.

Typically for weight loss, keto could be used for 2-4 months and then one could switch into a long term maintenance phase where you are including healthy carbohydrates.

Secondly there are some warnings that come with the keto diet. Our brains and hearts run exclusively on carbohydrates and when we severely restrict carbs, our body needs to switch to the use of ketones for fuel instead. There is a 3-4 day period of “brain fog” when you initially switch to a keto diet, where your ability to think is reduced. Not to mention food selection is quite limited and your social life may take a hit due to your restrictions. Plus, fair warning, your breath will smell bad too!

There are risks!

Very close monitoring is required for implementing a keto diet (especially to assess if keto would be a benefit to you). You also have to have a solid plan for transitioning into a regular diet, which should also be lead by a dietitian or qualified health care professional. The latter is quite important. This is because when you starve yourself of carbohydrates and then suddenly reintroduce a large load of carbohydrates, the body switches to an anabolic (or build up) mode and causes increased insulin, increased uptake of carbohydrates into the cells, increased utilization of those carbohydrates, all which increases the uptake and use of potassium, magnesium, phosphate, thiamine and increased sodium and water retention. The sudden changes in these electrolytes and vitamins can cause serious issues that can be as severe as a heart attack. AKA you can not have a cheat day in a keto diet and have yourself a big old piece of cake.

Keto & weight loss

Most of the research as a whole shows that you MAY lose more weight on a keto diet vs. regular diet.  However, when studies include body composition analysis they show that on average keto leads to more overall weight loss, but the amount of fat lost is the same. This means that keto diets lead to more muscle mass loss compared to a traditional diet.

Therefore, you may see a better outcome when you step on the scale but it may have less desirable body composition changes.

 The main reason for this finding is that you have to have a moderate protein intake while on a keto diet because protein can be used in a process called gluconeogenesis, where amino acids are (inefficiently) used to make glucose, thus keeping you out of ketosis, where as a traditional weight loss diet will be higher in protein to support the muscle mass retention. Other reasons could also include you can not have dairy, which has been shown to be an important food group to stimulate weight loss and muscle mass retention due to its leucine content.

It is also important to note that resistance exercise is a VERY powerful stimulus of muscle protein synthesis and muscle retention during weight loss, and regardless of diet should be included in your weight loss plan.

There may be benefits too

Keto may work for certain people. For instance, people who are on a keto diet often feel more satisfied with their diets. This is likely because higher fat foods are often pleasurable foods and provide flavour and mouth-feel to food (ie cheese, who doesn’t want to eat a brick of cheese every day!). Johnstone et al. (2008) conducted a study where participants were able to eat ad libitum (ie no restrictions or standards for caloric consumption) and participants were assigned to a keto group or a moderate carbohydrate group. They found that people on a keto diet felt less hungry, and lead to them eating less than compared to a moderate carbohydrate diet.

To my surprise, keto does seem to have a beneficial effect on decreasing blood glucose and HbA1c levels, decrease triglyceride levels, LDL cholesterol, and may increase HDL cholesterol levels. One thing I think is important to remember here is that in most cases, healthy dietary changes (ie more vegetables, fibre, less processed carbohydrates and sweets etc.), decreasing alcohol consumption, and increasing exercise can do the same for you, without doing something as intense or dramatic as a keto diet.

 Take home:

My personal and professional opinion on this is that I would first have someone try a to make healthy diet changes which would include consuming good sources of carbohydrates such as beans, lentils and whole grains before trying a keto diet. Keto in my mind is a last ditch effort if no other dietary interventions have worked.

Summary:

• Keto diets can be somewhat dangerous and should be eased into and out of with the help of a qualified health care professional
• Keto diets sometimes result in more weight loss but fat loss is comparable to typical diet
• There must be a caloric restriction to create weight loss, no different than a regular diet
• Keto may help keep you full and more satisfied with the diet and may help you adhere to the diet plan
• Keto does seem to have beneficial therapeutic effects for type 2 diabetes, pre-diabetes and on blood lipid profiles (but so does healthy diet/exercise)
• Ultimately the diet needs to be something you can follow and stick to before transitioning to your maintenance phase, if that’s keto, great!
• Bottom line: Try traditional approaches first, if that is not successful, you could consider the keto diet for the short term and transition into a healthy diet intervention for maintenance

I hope you found this helpful, this is not a full list of keto uses and I did not list all the pros and cons for you, as I wanted to keep this conversation relatively short. If you have any further questions about dietary interventions for building a healthier you, please feel free to come in for a visit. To learn more about me, you can find my bio here.  

Reference:

Johnstone AM, Horgan GW, Murison SD, Bremner DM, Lobley GE. 2008. Effects of a high-protein diet on hunger, appetite and weight loss in obese men feeding ad libitum. Am J Clin Nutr. 87, 44–55.

Nutritional strategies for bone health in female endurance athletes

Are you a constant sufferer of stress related bone injuries? An endurance athlete? Female?

There are many different contributing factors of stress fractures in endurance athletes. Overcoming these challenges and working toward the prevention of these injuries is so important in order to continue with our training and competition schedule. In this article ,I will discuss why female endurance runners are more susceptible to these injuries along with some modifiable risk factors (i.e. nutrition interventions) that can be manipulated to reduce your risk of suffering one!

(Men, I did not forget about you. Stay tuned for an article on stress fractures in male endurance athletes!)

Possible Reasons for Stress Fractures

There are many endurance athlete-specific reasons why stress fractures may occur. One reason for this is the fact that distance running has a high metabolic demand. It costs a lot of energy to run fast for long periods of time and thus increases our need for a higher caloric intake. This can put us at risk if we are inadvertently under consuming calories. Inadequate food intake including both overall energy and micronutrient intake, can play a role in increasing our risk of fractures.

Excessive negative energy balance aside, runners seem to be especially at risk compared to other endurance athletes who also consume lots of calories. Although running does indeed increase bone mineral density (bone strength) with the proper balance of training and recovery, the repetitive nature of high-volume running often leads to the athletes not taking adequate rest days and/or programming in periodized reduced training weeks. This can lead to insufficient recovery and healing of the bone in between bouts of stress and therefore not enough time for the bone to adapt and become stronger. I would refer you to my colleagues, Dr. Sean and Kayla Ng, at the clinic to find out more about how to structure your training schedule.

 On top of inadvertent negative energy balances and insufficient recovery, some endurance athletes neglect the inclusion of a strength program into their training schedule. Lifting will act as a stimulus to increase bone mineral density. Not only this, but strength training can also aid in enhancing hours muscles ability to direct forces optimally through bones (i.e. compressive vs. sheer forces). For more on this, again I would encourage you to discuss this with my colleagues Dr. Sean and Kayla Ng.

Another risk factor is related to how in some circles, runners are often pressured to fit into the very thin and light body category. First off, low BMI or low weight in itself can be correlated with low bone mineral density. In addition, if that low weight is combined with weight loss efforts and low energy intake, this can wreak havoc on your bone health due to hormonal changes (i.e. decreased estrogen production) and resulting menstrual dysfunction (which can act as an early sign that your are consuming insufficient calories).

BUT, all is not lost!  There is a lot we can do to overcome our bone health challenges. Nutrition, for one, is an easily modifiable risk factor that can have positive outcomes for our bone health.

Nutrition & Bone Related Injuries

To put the need for proper nutrition in maintaining bone health in perspective, here are the results of 3 interesting and very applicable studies on the topic:

1. Negative energy balance and estrogen: Low energy availability, which is the amount of energy left over after exercise for normal physiological function expressed in calories/kg fat free mass, decreases estrogen levels. This results in a 4x greater risk of bone injury compared to those who have adequate energy availability.
2. Insufficient calcium: Low calcium intake (800mg) resulted in 6x more risk for bone injury compared to high calcium (1500mg).
3. NFL players and Vitamin D: In NFL male players, players with 1+ fractures had higher rates of inadequate levels of circulating Vitamin D.

Practical Applications:

So, here’s what you can do:

1. Make sure nutrition intake closely matches energy demand of sport & daily life.
2. Consume enough bone building materials (i.e. calcium, vitamin D, and magnesium)
3. Weight loss tactics should be introduced at appropriate times (likely in the low training/off season) to reduce risk of injury close to race season.

I hope these statistics and general tips reinforce how important nutrition planning is for endurance female athletes. If you still have questions or need guidance on planning for your race season, come visit me at the clinic!  You can check out more about me on my profile HERE.

References:

Tenforde AS et al., 2016. Association of the female athlete triad risk assessment stratification to the development of bone stress injuries in collegiate athletes. The American Journal od Sports Medicine 45(2), 302-310.

Heikura IA, Uuitalo ALT, Stellingwerff T, Bergland D, Mero AA, Burke LM. 2017. Low energy availability is difficult to assess but outcomes have a large impact on bone injury rates in elite distance athletes. International Journal of Sport Nutrition and Exercise Metabolism.

Barrack et al., 2014. Higher incidences of bone stress injuries with increasing female athlete triad-related risk factors. The American Journal of Sports Medicine. 42(4). 949-958.

Papageorgiu M, Dolan E, Elliot-Sale KJ, Sale C. 2018. Reduced energy availability: implications for bone health in physically active populations. Eur J Nutr. 57:847-859.

Maroon JC, Mathyssek CM, Bost JW, Amos A, Winkelman R, Yates AP, Duca MA, Norwig. 2015. Vitamin D profile in National Football League players.

Very Low Carbohydrate Diets & Endurance Events: Part 2

Welcome to part 2 of the my exploration of very low carb diets for endurance athletes.  My last article provided the basis for understanding this article as it explored how and when our body choses to use fat vs. carbs.  Check it out here.

In this article, I will now explore (1) do low carb diets actually enhance fat metabolism and (2) does that actually makes us faster.

Does VLCD increase fat burning capacity?

Short answer, yes, the body is forced to increase fat use to support the energy needs during exercise. Research clearly shows that after adapting to a keto diet for as little as 3 weeks results in significantly elevated rates of fat oxidation (0.6g/min to 1.5g/min) during exercise. Fat oxidation at moderate intensities (65% VO_2max) in elite ultra-endurance athletes on a keto diet contributed 88% of the fuel for exercise verses 56% in athletes consuming high carbohydrate diets. Now, if we remember what we discussed in the last article, we learned that as we increase intensity we increase the amount of carbohydrates burned. This begs the question “will those high fat oxidation rates continue at intense ecercise (80% VO_2max)?”. Another study investigated the fuel usage of elite race walkers at 80% VO2max, and they too found that fat oxidation was elevated to the same levels as previous research (1.5g/min).

Research Outcomes of VLCD and Performance:

The more important question in my mind (and likely yours as well) is “well that is fine and dandy- my body will burn more fat, but what will happen to my performance?!”. We will review some key research studies that have looked at fat adaption diets (high fat diets for 3-7days), keto diets and their effect on performance. The majority of high fat diet adaptation and keto diets find that performance decreased and a handful found they had no-statistically significant effect. Only two articles find a performance benefit.

Keto, Training and Performance

Louise Burke et al. (2017) conducted a large study investigating the effects of a keto diet, chronically high carbohydrate diet or periodised carbohydrate diet on race performance of elite race walkers after a 3 week intervention and training camp. Athletes on the keto diet perceived the training to be significantly more difficult and experienced an inability to complete the exercise training sessions planned. This is a very important point because if an athlete cannot train as hard as they could they won’t see much improvement in their sport.

After the 3 weeks of intense training, the keto group had higher fat oxidation compared to the two high carbohydrate groups. All groups had significant increases in their maximal oxygen uptake (VO_2max) as a result of the training. As we discussed in the previous article, burning fat is less efficient and this study clearly demonstrated that at all competition race speeds there was significantly more oxygen used in the keto group and there was no change in the fraction of VO_2max at various speeds. The high carbohydrate and periodised carbohydrate groups used less oxygen and were able to keep the same pace at lower fraction of VO_2max. In plain English, the two carbohydrate groups improved their running economy and efficiency with the training where the keto group did not reap the benefits of the training because the cost of burning fat is so high.

Lastly, this study compared pre and post training performance walk times in a real 10km race. They found that both carbohydrate groups had a reduction in their time by 5-6% (on average 190s and 124s faster for high carbohydrate and periodised carbohydrate group). There was no improvement in the keto group and on average their times were 23s slower. There was a wide variability in performance for the keto group, ranging from 162s faster to 208s slower, meaning that keto worked for some individuals but not others.

High Fat Diet With Carbohydrate Loading

What if we don’t go into ketosis and we use a fat adaptation strategy + carbohydrate load, best of both worlds right? Havemann et al. (2006) showed that when elite cyclists consumed a high fat diet (68%) for 6 days with 1 day of carbohydrate loading that there was no significant difference in time to complete a 100km simulated bike race compared to a traditional high carbohydrate diet. However, if we look at the time to completion, we find that the high carbohydrate trial was completed on average 3 minutes 44 seconds faster (likely significant in the real world), leading us to believe that on average high carbohydrate diet may be superior to high fat diets. Again, 3 out of 8 racers on the high fat diet did improve their time compared to high carbohydrate diet, demonstrating that there may be some athletes who may respond well to a high fat diet.

More importantly, this research included 1km sprints throughout the ride to simulate a race like situation and found that the power output was significantly lower in the high fat diet group which lead to slower sprint times. Despite having lower power output in the high fat trial, they perceived they were working as hard as they were in the high carbohydrate trial. There was no difference in muscle recruitment during the sprints, meaning the high fat trial worked just as hard as the carbohydrate trial but did not achieve the same results in the sprint performance. The researchers thought that the high fat diet + a carbohydrate loading period would result in glycogen sparing due to increased reliance on fat for fuel, thus improving sprint times as sprinting relies on glucose to provide fuel. This was not the case and it is possible that high fat/fat adaptation diets reduce the ability to effectively burn carbohydrates.

Summary

• VLCD do result in higher rates of fat oxidation during exercise
• VLCD may reduce response to training
• VLCD decreases economy in elite athletes
• VLCD decreases ability to work at maximal effort which is important when there is change in work intensity- ie running up a hill, breaking away from the pack
• Most studies show that on average VLCD negatively affect performance in endurance athletes, however there are some that may respond well
• Remember that VLCD are not the same as training fasted or temporarily low carb diets to train your body to use fat more effectively, as this is an effective training method

In my final article in this series, I will explore the roll of supplements, the keto diet, and how that relates to athletic performance.

References:

Volek JS, Noakes T, Phinney SD. Rethinking fat as a fuel for endurance exercise. Eur J Sport Sci. 2015;15(1):13- 20.

Volek JS, Freidenreich DJ, Saenz C, Kunces LJ, Creighton BC, Bartley JM, Davitt PM, Munoz CX, Anderson JM, Maresh CM, Lee EC, Schuenke MD, Aerni G, Kraemer WJ, Phinney SD. Metabolic Characteristics of keto-adapted ultra –endurance runners. Metabolism. 2016;65(3):100-10.

Burke LM, Ross ML, Garvican-Lewis LA, Welvaert M, Heikura IA, Forbes SG, Mirtschin JG, Cato LE, Strobel N, Sharma AP, Hawley JA. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. J. Physiol. 2017;595(9):2785-2807.

Havemann L, West SJ, Goedecke JH, Macdonald IA, Gobson ASC, Noakes TD, Lambert EV. Fat adaptation followed by carbohydrate loading compromises high intensity sprint performance. J. Appl. Physiol. 2006;100: 194-202.

Leckey JJ, Ross ML, Quod M, Hawley JA, Burke LM. Ketone diester ingestion impairs time-trial performance in professional cyclists. Front. Physiol. 2017;8(806).