Depletion Workouts, What are They, and How & When to Introduce Them?

Training Modality that can boost performance through more efficient glycogen use and tapping into fat stores to contribute to more successful multi-hour training and racing...

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Runner after completing one of my Depletion Workouts

Background: Glycogen, the Fuel Source we Deplete and Restore

Let us start with some basics before getting into the actual workout modalities or types and frequency of training used in your training/exercise plan. First off, simply, your body runs off of sugar primarily for most of the time; this sugar is referred to glycogen, and is stored in limited quantities in the liver and the muscles of the body. For most individuals consistently training or exercising, you can “store” up to approximately 60-90 minutes of fuel (glycogen) for a moderate-high intensity exercise period. Of course this depends upon many variables; some being, metabolism, fitness level, frequency (training days per week), and volume (hours of training per week), intensity level of training throughout each day, week…etc., and nutritional “expertise”. By that I mean, how well you fuel yourself before, during, and after each training session, which should be correlated directly to your personal needs and the length and intensity of the training or exercise session(s) you’re performing. Besides your training, how active or inactive you are throughout the rest of the waking hours. In other words, are you sedentary on a computer all day, or does your job require you to be on your feet and constantly moving for 12 or more hours? This must be taken into consideration as well, otherwise, you may likely be over-fueling (consuming too much) or under-fueling (inadequate caloric intake for your activity level). Keep in mind that exercise, especially moderate-to high intensity training will boost your metabolism of calorie burning for hours post-workout; some activities more than others. For instance strength training and swimming at intensity utilizing a numerous amount of muscles and multi-joint movements, may have your metabolism elevated for up to 10-15 hours post-workout for many trained individuals. Whereas less taxing of total muscular and joint training may elevate your metabolism for anywhere between 2-8 hours; again, individual and sport/exercise specific. Keep this main take-away point in mind, exercise that involves all four limbs versus (vs.) only two, as with running vs. cycling, will require and burn more calories per segment of time. Again, level of intensity over the training period (high intensity vs. low intensity) will also dictate caloric consumption in terms of demands, or simply “calories burned”. Furthermore, the human body is still burning some glycogen during sleeping hours, now it’s not much, but it is a factor to consider. With another critical take-away point being, when and how much you last ate anything. For example, your last period of intake was at 6pm, and a calorically balanced breakfast or snack prior to training vs. no intake, will alter your performance (time at intensity), as well as your effectiveness both physically and mentally. Furthermore, training on “no fuel” vs. adequately fueled alters how the human body metabolizes energy and where it draws its primary source from at times, whether it’s primarily – carbohydrates (carbs), fat, or protein. The longer the session and low on glycogen, the sooner the body starts to tap into fat stores and protein. Once the body starts using protein as its primary source, we refer this to catabolism or “destructive metabolism”, opposed to anabolism or anabolic, which is “constructive metabolism” – muscle maintaining or building synthesis from adequate intake of fuel applicable to the type of training you’re performing. So yes, eventually without adequate carbs or fats to draw energy from, the body starts to breakdown muscle proteins to continue for some period at intensity (individual and sport-specific factors apply)…etc. This is where we start to lose lean muscle mass or what’s referred to as muscle atrophy vs. hypertrophy, or instead of muscle gain in size and/or composition, we’re losing muscular composition, size, and at some point strength. Now that we’re ready to discuss what a depletion workout is, when to consider introducing into your training plan, or whether not to venture down the depletion workout road altogether (ever), we will explain what a depletion session does to the body.

Why perform a Depletion Workout, What’s the Purpose?

Depletion workouts are designed for weight loss, specifically, fat stores. Depletion training burns more fat and (for most) improves training adaptations that allow performance at intensity longer with lower glycogen levels. The whole point of a depletion workout/day is to “drain” your glycogen stores – most effectively performed during an early morning session, and then refill muscle-glycogen storage optimally. Therefore, what a depletion workout does is empty remaining stores so that when you eat carbohydrates post-workout, they are “sucked up” or synthesized more rapidly into the muscles like a vacuum and stored as muscle and liver glycogen. Cardiovascular-wise, sprint intervals, hill repeats, and other high intensity interval training (HIIT) modalities are often the most effective form of depletion exercise for subsequent glycogen synthesis. Therefore, for strength training sets (safe) rapid execution with challenging weights/workloads, in other words, “high intensity” sets are going to utilize or burn more sugar (carbohydrate/glycogen stores). It may seem obvious, but these workouts are typically 1-2 hours max. If you’re training is going to last 3 hours or more, then you’ll need to take in carbs at about the 60-70min timeframe. Otherwise, at 2-4 hours in, you’ll “hit the wall” or “bonk”, and need to back off considerably or even stop for a period while getting some sugar back into the system. Depending on your metabolism and what you intake, this could take 20-60 minutes. I’ve found that a couple of gels (200 calories) with cold water will empty out of your gut and get into the bloodstream faster than a bar or other solid food and water…etc. If you’re one who can’t stomach gels, then a carb-rich drink with 100-300 calories with key electrolytes as well. Your typical Gatorade or Powerade have about 20 grams of carbs (sugar) per 12 ounce portion, but only ~80 calories. Therefore, if you’re really suffering and deep into glycogen depletion, you may likely need to eat a (Clif) bar or some gels or chews along with the carb drink.

Key Electrolytes that We must not Deplete during Multi-hour Training Sessions

Now, there are several products in the market that are more scientifically geared towards endurance athletes who normally lose significant electrolytes as well. The “Big 4” as I call them are Sodium, Potassium, Magnesium, and Calcium; so look for these in your performance drink. For instance, since I’m typically racing 100-200 miles or more, the sponsor’s drink that works for me has 30 grams of carbs, 300mg of sodium, 300mg of potassium, 150mg of magnesium, 100mg of calcium, plus branched-chain amino acids (or BCAAs) per serving. Therefore, my electrolyte balances and protein synthesis is addressing the volume and intensity of my training and racing. This may not work for you, so you have to try different products on the market that works for you, in other words, adequately addresses the type, volume, and intensity of your training and competing – without making you nauseous. After all, what good is a product that makes you nauseous? You may even vomit, compounding your electrolyte balance and hydration – a whole other article in itself. For intense sessions lasting longer than 2 hours, electrolytes really come into play at warmer temperatures – along with glycogen or sugar levels. I’m not going to prescribe a perfect portion and ratios, because just like fingerprints, we’re all different.

Trial & Error – Fueling & Hydrating, a Component We all Must Go Through

Therefore, you must learn your body, what works, and what does not. It’s “trial and error”, and each and every one of us has to go through this period in order to determine what works best for us at varying session lengths, as well as under varying conditions (i.e. 95-100+ and humid, 70 and cool, 35 and windy, or flat vs. a very hilly or mountainous course). The demands upon your body fuel-wise and electrolyte-wise will differ under such varying conditions. This is why I insist my athletes “learn their body”, be very attuned to biofeedback (what your body is telling you), and “dial-in” optimal intake types and amounts for every condition. You never know what event day or race day conditions will be, so you have to have learned and prepared for every scenario. This takes time, but we all started from scratch and learned – sometimes rather easily, and sometimes the hard way. At some point, we all have “run out of gas”, cramped up, or have been forced to shut down or cease training altogether in order to refuel/rehydrate and wait until we have adequate blood sugar and electrolyte balances. For most, you only have to learn these lessons once, and hopefully never get to such stages in training or racing again. This brings up another point, as I say, “there’s no training like racing”. I don’t care how hard I push myself, I can never push myself as hard as in a competitive race, it’s just human nature that amongst others, we’ll push ourselves harder. This is often applicable to your group rides, group runs, group swims, or partnered strength sessions; it’s just the way we’re wired.

Most Common Athletes Using and Benefitting from Depletion Training

Endurance athletes are the most common athletes utilizing depletion workouts in their training plan. For most who have tried glycogen depleted endurance training most often involves cardiovascular exercise such as running or cycling on an empty stomach first thing in the morning; however, strength training for fitness, bikini, and bodybuilders have started using this training modality as well. So, when glycogen store levels are low, with only coffee, tea, and/or water prior, and then performing at a moderate-high pace/intensity (~70% – 75+% of max heart rate (MHR)) for 60-90 minutes. Glycogen is the only fuel that can supply and support exercise intensity above 70% of MHR. Therefore, when you approach depletion, your body is forced to access your fat and protein stores instead. The body will first tap into fat stores, and as the last resort before exercise has to cease altogether, it’ll start breaking down muscle proteins to fuel your effort. Research has confirmed that training in a depleted state prompts the body to adapt to perform more efficiently at processing carbohydrates and fats. As the body adapts, it results in better utilization for optimizing fuel usage in the future. Certainly, this is not for everyone, and incorporating more than once per week is typically not recommended. This training method isn’t without risks as well, since there may be a higher risk of overtraining and more lethargic performances early on into using or overusing this type of training. This training technique should be introduced gradually and used sparingly, perhaps once a week for most athletes is more than sufficient. While it’s typical to see a reduction in performance and energy levels in 1-2 days following these workouts, if lethargy or subpar performance persists for 4-5 days or more, even when training at a low intensity level, then that’s a red flag indicator to back off the frequency. Glycogen Depletion Training is definitely a high-risk technique; however, for many the rewards of improved performances providing that extra boost to the next level is worth it. Another way to incorporate depletion workouts (especially if you’re a multisport athlete), is to use one of your 2-a-days or 3-a-days. Preferably, perform two moderately hard workouts in the same day, separated by incomplete recovery and refueling. Because the goal is to deplete glycogen and carbohydrate stores, stay away from carbs between the two workouts to make sure that you start the second or third session in a depleted state. Again this can be applied to a strength training day as well. When you finally do refuel, make sure you have a good balance and abundance carbohydrates, protein, and fat. Like anything else, the amount of caloric intake should be commensurate with the type, intensity, and volume of your training. Lastly, make sure you stay well hydrated and get a good night’s sleep to aid this adaptation process. If done correctly, you’ll have taught your body that when you intake carbs, it utilizes and metabolizes them more efficiently, as well as teaching the body to tap into fat stores sooner, and effectively helping you maintain or lose some body fat. Best of luck, and train smart. Coach Parker

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Todd Parker is a World-Renowned Cycling & Triathlon Coach, Influencer within the Sports & Fitness Industries, and Corporate Wellness Consultant – consulted by Coaches, Athletes, Corporations, Governing Bodies, and Sports Supplement, Gear, and Apparel Companies Worldwide. Todd’s a former Professional Triathlete, Elite Cyclist, Personal Trainer, Strength Coach, Public Speaker, Guest Lecturer, and Professor. Besides his expertise in consulting in Training and Coaching, Todd is also a Corporate/Government Security Consultant. You can reach Todd at: , by appointment only, or at his secure site

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