Written by Ryan Jackson and Jacob Linn
The term “fueling” is a popular buzz word within the sports dietetics and athletic performance setting. Ensuring athletes are properly fueled for competition and training is very important for athletes to perform at their best. However, is our view of fueling short sided? What I mean by this is not that we are wrong in any way for fueling but that we may only be looking at fueling in a narrow sighted way. Much of the sports dietetics fueling strategies is centered on the type of activity being performed and not as much as the desired adaptation the athletic performance professional is seeking to improve from the activity. When thinking in terms of macronutrients we often might emphasize protein as a means to promote our muscular adaptations while carbohydrates are emphasized as our fuel, and thus glycogen stores must always be full or replenished. However, there is also a case for carbohydrate manipulation in energy system development models to promote desired adaptations. Recently there has been a growing amount of research looking into the concept of restricting carbohydrates around training sessions in endurance athletes to accentuate positive training adaptations. One of the common complaints that has been levied by sports dietitians and sports performance professionals against low carb diets in athletes is that it has been at times proven to benefit endurance athletes yet has not quite been proven to work for “anaerobic team sports sport athletes”. While I used to raise this same point myself, I believe this to be a narrow sighted view of things. There is not a plethora of information or any real concrete research providing a link between carbohydrate restriction and anaerobic team performance but bear with me for a second. A well developed and trained aerobic system HAS repeatedly been found to improve repeat sprint ability in team sports athletes. Carbohydrate restriction HAS been found to improve aerobic training adaptations. Therefore carbohydrate restriction in conjunction with aerobic training improves training adaptations which theoretically would improve performance in team sport athletes. If you are not following this sequencing, I hope the rest of this article will clear things up however it might just make you more confused.
One important point to get across before we move forward is that when we discuss carbohydrate availability and training, we are talking about just that TRAINING. Training is implemented to improve performance in competition. Intense training will lead to an initial or acute decrease in performance but over time our body adapts, supercompensates, and ultimately performance is improved. We know nutrition has a paramount role in the adaptation process of training. When it comes to training adaptations we think protein and when it comes to fuel, we often think carbohydrates. On a side note, recent research indicates fat is more of a fuel during high intensity exercise than what we learned from the tried and true RER substrate utilization chart. We consume protein after heavy lifting and training sessions to promote protein synthesis. However, not every training session is completely geared towards these specific adaptations. Team sports athletes also perform intense conditioning sessions often with the end goal to improve repeat sprint ability. We certainly would want to improve this ability through the adaptive process as well. Reducing carbohydrates around certain types of training will help enhance those training adaptations. We are not talking about restricting carbohydrate in competition, just as we are not typically prescribing extremely intense and taxing training methods in the days leading up to a competition. We are talking about doing it in carefully planned blocks training. Think of it this way in terms of the pathways (mTor and AMPK) responsible for signaling endurance and resistance training adaptations. Protein is to mTor and resistance training adaptations as carbohydrate availability is to AMPK and endurance training adaptations.
DISCLAIMER:
I have worked in the collegiate athletic performance setting for the past eight years. I have only worked in the collegiate setting meaning I have next to zero professional or private experience other than I have done some private dietary consulting with powerlifters and strength athletes. With that being said I am well aware of the dietary habits of young athletes. I am well aware that before recommending an athlete to restrict and/or manipulate a macronutrient when they have not proven the ability to consistently eat 3-4 balanced meals a day and sleep 7-9 hours a night it is not a good idea. I am well aware that some young athlete’s biggest problems are inadequate caloric intake. On the strength side of the spectrum I am well aware that the collegiate setting can be a scheduling nightmare. I am aware of the struggles of finding optimal training times around class and practice schedules. I will do my best to give as much information and as many examples as possible so the information can be adapted your setting. I am presenting a theoretical model I have adapted from the current research and my own experience as strength and conditioning coach who also has a background in dietetics. I believe this model could be applied to advanced athletes who have demonstrated high level ability to manage their diet and lifestyle. Depending on the situation and what food access is available, a more team wide approach could be implemented.
Part 1: The Energy System Training Model
Energy system development and training is a topic that has been rehashed to death although I continue to find it a fascinating topic. Everyone trains it different and has their own philosophies on it. In the end, most coaches will agree that all the energy systems need to be developed to some degree depending on the sport in general prepatory phases of training. The focus of this article is no different.
Before going any further it is very important to me to give credit where credit is due. The concept and history of this energy system development model is really the result and culmination of an environment that promoted and facilitated education, creativity, and innovation. From a practical standpoint, the model is blatantly based on Ben Peterson’s and Charlie Francis’ principles and methods from Joel Jamieson, Cal Dietz, and standard American football conditioning drills. In 2013, Ben Peterson gave a presentation energy system training that changed the way I looked at energy system training. Among his main points were that aerobic capacity contributes to an athlete’s repeat sprint ability and that classifying conditioning into aerobic work or lactic work or alactic work are essentially self-limiting terms as there is so much fluxuation within the systems during actual competition and conditioning drills. Instead of doing one type of energy system training he proposed a system where conditioning methods are classified by looking at their gas exchange ratio and heart rate response. He came up with four metabolic classifications: push, climb, stretch, and pull. We took these classifications and with the help of a bunch of unofficial research on ourselves first and several athletes from a wide array of sports, a heart rate monitor system, and a lot of mistakes put together our own spin on the system. Based off of what we found we called it ETCP: endurance, threshold, capacity, and power. Endurance and threshold were thought of as sub threshold work while capacity and power were thought of as supra threshold work. When looking at these from a High/Low Intensity Charlie Francis lens, sub-threshold work would fall in more of the Low spectrum while supra-threshold would fall more on the High spectrum. We color coded it to match the heart rate zones from the polar system and to help convey and communicate the intent of the session to athletes and coaches. Here is a quick breakdown of the four classifications.
ENDURANCE
Endurance work is your general and basic continuous work. Often referred to as aerobic base work. This is typically performed at 65-80% HRmax and could be looked at as RPEs ranging in the 4-7 range. The metabolic goals of this type of work include aiding in recovery and imporving sub-threshold work capacity. Endurance training should in theory prevent our time to fatigue and reduce the need to tap into the lactic system. Some common examples of endurance training would be tempo runs, roadwork cardio, and some low intensity density training/circuits. The table lays out the various methods.
THRESHOLD
Threshold work is considered higher intensity aerobic work. It could be referred to or thought of as aerobic power style training. The intensities of threshold work is typically performed at 80-85% HRmax and could be viewed as RPEs of 6-9. Threshold training should be able to improve work capacity at higher aerobic intensities and improve the anaerobic threshold. Although the way to attack the threshold training can be quite varying in nature some common examples include high resistance intervals, explosive repeat, high intensity continuous training, and threshold intervals. If you have read Ultimate MMA Conditioning before, the aforementioned examples should look pretty familiar. Much of the methods Jamieson utilizes to train the aerobic system, we found to fit well into the threshold classification. The table lays out the various methods.
CAPACITY
Capacity training is over simply defined as full go, incomplete rest. The idea is that capacity work is very demanding on the metabolic systems. It is working on the capacity of all of our systems. It is performed at 90-100%HRmax and RPEs of 8-10. The concept of capacity training is not all that difficult. Make it physically demanding without giving enough time to recover. Some common examples utilized to train capacity are short to long intervals with incomplete rest and circuit style weight room training(density lifting circuits, German Body Comp training from Poliquin). The table lays out the various methods:
POWER
Power training is over simply defined as full go, full rest. While capacity is highly metabolically demanding, power training could be viewed as highly demanding on the central nervous system. HRmax percentages are not prescribed here at the goal is generally to perform full speed work with complete rest in between reps, intervals, sets, etc. Power training aims to improve our ability to perform high intensity speed/power work and overall metabolic power. Some common examples utilized to train power are short to long intervals with complete rest, plyometrics, max effort strength training, and Olympic lifting. The table lays out the various methods:
Part 2: The Carbohydrate Restriction Model
So how exactly does carbohydrate restriction before and/or after training work? The basic premise of carbohydrate restriction around training is that it has been found to increase AMPK signaling which in turn leads to mitochondrial biogenesis. In our exercise physiology classes we might recall learning about adaptations to training. Two of the predominant peripheral adaptations which improve aerobic performance are an increase in mitochondrial and capillary density. What researchers are finding is that with carbohydrate restriction both before and after training we are able to induce greater increases in mitochondria than we would with a regular carbohydrate intake around workouts as is commonly recommended for both aerobic and high intensity anaerobic activity. It appears there are two primary proteins who are regulators of mitochondrial biogenesis. One is PCG-1a, which is commonly referred to as the master regulator of mitochondrial biogenesis and while the other, is known as p53. Increases in AMPK signaling, usually from exercise that is of a more aerobic nature, will lead to PCG-1a and p53 translocation. PCG-1a appears to be enhanced in conditions of low glycogen levels pre-exercise while p53 is enhanced in conditions of low carbohydrate levels post-exercise. In fact, researchers found p53 to increase threefold with carbohydrate restriction post-exercise compared to regular carbohydrate intake post-exercise. From these research based findings some carbohydrate availability strategies have been established. The research has helped establish the following terms to refer to carbohydrate availability strategies; train low/fasted and sleep low/recover low. An important point to note and perhaps the major point of this article is the type of training being performed is very important in selecting which carbohydrate availablity strategy to employ.
Train low(low glycogen levels pre-exercies) strategies are effective at increasing PCG-1a. However, train low strategies are potentially effective for reasons that surpass increases in PCG-1a. The first being an increase in lipolysis during fasted exercise. The other interesting finding which appears to help promote endurance training adaptations in a fasted state is autophagy. Autophagy can be simply looked at as the natural process of cell death and clearing the way for new better adapted cells to take their place. Fasted training in conjunction with endurance exercise has been found to increase the pathway responsible for this process. Exercise intensity is important when we are training fasted. Lower intensity exercise is the preferred type of exercise to perform as higher intensity exercise can be detrimental in states of low carbohydrate availability. Some of the drawbacks include protein breakdown, increases in susceptibility of illness/infection, and reduced ability to use carbohydrates as fuel during high intensity exercise. The most logical time to perform these sessions is in the morning relatively soon after waking up. Caffeine ingestion is also recommended before these types of training sessions.
Sleep low/recover low strategies(carbohydrate restriction post-exercise) were derived from research looking into two training sessions with carbohydrates restricted between training sessions. Researchers found better adaptations when they restricted carbohydrates after an AM session when a PM session was to be performed. Further research found better adaptations when carbohydrates were restricted after a high intensity PM session all the way through bed time. Sleep low/recover low strategies is where we can maximize the adaptations from high intensity exercise by inducing increases in p53. The exercise is performed in a state where glycogen stores are full but carbohydrates are restricted for an extended period of time post exercise (current research recommends approximately 6-10 hours and/or overnight). The most logical time to perform these types of sessions would be in the afternoon or early evening followed by carbohydrate restriction post exercise all the way through bedtime.
While train low and recover low strategies are found to work in conjunction with endurance exercise, carbohydrate back loading is a strategy worth mentioning as it is reported to work in conjunction with heavy strength/resistance training. Popularized by creator John Kiefer, carbohydrate back loading is an adapted version of the Anabolic Diet by Mauro Di Pasquale. The general premise is that you skip breakfast, restrict carbohydrates throughout the day until lifting in the later afternoon/early evening and then consume carbohydrates for 1-3 meals post-training up until bed. The oversimplified suggested mechanism behind this strategy is that it plays on our bodies release of insulin(nutritionally) and the translocation of glut4 receptors on our muscle cells in response to heavy muscular contractions. In theory this creates an environment of insulin sensitivity where amino acids and carbohydrates are shuttled into our muscle cells as opposed to fat cells. Carbohydrate back loading strategies recommends the consumption of high glycemic carbohydrates to induce higher insulin spikes. Although criticism is commonly levied against this strategy based on the author not being an dietitian or having a educational background in nutritional sciences, there are several testimonials and anecdotal evidence this is an effective strategy at increasing lean body mass and decreasing body fat. Principles of this strategy can be utilized along with other carbohydrate restriction strategies especially, when conditioning and strength training are both being performed, which is almost all cases for team sport strength and conditioning programs.
Adequate protein intake after training and throughout the day at every meal is highly recommended regardless of the carbohydrate restriction strategy is being utilized.
The Application
With our basic understanding of both the carbohydrate manipulation strategies and energy system development model from part 1 we can infer what nutritional and training strategies will lend themselves to the best possible training adaptations. The current research indicates recover low strategies would maximize adaptations with supra-threshold training methods while train low strategies would maximize adaptations with sub-threshold training methods. Carbohydrate back loading can be utilized after lifting and/or PM conditioning sessions. For the purpose of this article if we reference back loading we are for the most part referring to carb intake after a session that was performed in a train 
I want to do my best to lay out how you might accomplish undertaking carbohydrate restriction strategies in team sports training environment. As I mentioned in my disclaimer I have some time and experience as a collegiate strength and conditioning coach so I am well aware of the scheduling nightmare that athletic performance settings can be. The tables will include training type, carb restriction strategy, and training time. This application is in most cases for advanced athletes who are nutritionally competent, however if you are in a setting where most meals and snacks is provided by you and your staff then a more team wide approach could be implemented. I firmly believe this application has a place in competitive powerlifters and strength athletes off-season or GPP blocks of training.
This is probably the best applied model of this system but also the most unrealistic in a team setting. Days 1/3/5 are classified as a HIGH intensity day. We will utilize suprathreshold methods on these days. Carbohydrates are free game throughout the day leading up until the training session. However, carbohydrates will be restricted as soon as training is completed and continued until bedtime. This is a combination of the recover low and sleep low training Days 2/4 are viewed as a LOW intensity days. We will use subthreshold methods on these days such. These will be performed in conjunction with carbohydrate strategies of train low/fasted. Train low and fasted can be thought of as being one in the same. Days 6/7 are off from training. Regular carbohydrate intake is fine on these days.
THE 5 DAY SPLIT-PM training
Days 1/3/5 are classified as a HIGH intensity day. We will utilize suprathreshold methods on these days. Carbohydrates are free game throughout the day leading up until the training session. However, carbohydrates will be restricted as soon as training is completed and continued until bedtime. This is a combination of the recover low and sleep low training Days 2/4 are viewed as a LOW intensity days. We will use subthreshold methods on these days. These will be performed in conjunction with carbohydrate strategies of train low. Since these sessions will be performed in the PM, low-carb meals will be eaten up until training, followed by carb back loading. In essence, these session are not being performed “fasted” but with carb restriction the night before and the day of, the session will be a train low session. Days 6/7 are off from training. Regular carbohydrate intake is fine on these days.
This model combines all three strategies. On days 1 and 5 recover low strategies are utilized following AM conditioning sessions. After about 6-10 hours post training carbohydrates can be reintroduced and consumed. Days 2 and 4 utilize fasted AM training sessions following by regular carb consumption before and after lifting sessions. By definition these sessions are not being necessarily performed in a true “train low” state as carbohydrates were consumed the night before. Glycogen stores might have been burned during sleep but are likely not completely depleted. Days 6/7 are off from training. Regular carbohydrate intake is fine on these days.
This model combines all three strategies. This training schedule is not unlike a typical football training schedule in the summer time. This model includes conditioning and lifting on all days. On days 1 and 5 recover low strategies are utilized following AM conditioning sessions and PM lifting sessions with back loading post lifting. Days 2 and 4 utilize fasted AM training sessions following by regular carb consumption before and after lifting sessions. Although it notes back loading after PM upper body lifting sessions, carbohydrates will be consumed throughout the day, so technically it is not a backload. Days 6/7 are off from training. Regular carbohydrate intake is fine on these days.
The 3 day split can be difficult to work around as training never takes placed on successive days. On day 1 subthreshold methods will be utilized in fasted state. By definition this session is not necessarily performed in a true “train low” state as carbohydrates were consumed the day before. Recover low strategies will be utilized post training for 6-10 hours followed by carb back loading. On days 3 and 5 recover low strategies will be utilized post training for 6-10 hours followed by carb back loading. When working in a 3 day split, I believe a low carb intake for the duration of the GPP block might be the best option to maximize adaptations.
The 3 day split can be difficult to work around as training never takes placed on successive days. On all days recover low/sleep low strategies are used. With all PM training sessions, there will be no fasted or training low strategies utilized. When working in a 3 day split, I believe a low carb intake for the duration of the GPP block might be the best option to maximize adaptations.
Conclusion
My hope is that this article brought to light the need for the athletic performance setting to be a communicative and integrative environment. A periodized diet plan which coincides with a periodized training plan can go a long way in maximizing training adaptations not just those from resistance training. Where we often view the dietitian’s role as helping to fuel mainly the activity, they can also have a significant impact on fueling the desired adaptations of the performance coach, outside of just promoting protein post workout. The better coaches and dietitians are able to understand each other’s areas of expertise the further along we can drive our profession and maximize the development of our athletes.
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