In part 1 of this nutrient periodization series we discussed how to periodize our calorie and macronutrient (carbohydrate, protein and fat) intake on a daily basis according to our training demands and lifestyle factors (days of low activity/high sedentary behaviors compared with very active days). In part 2 we discuss more precise strategies to periodize our intake of carbohydrate and protein specifically to optimize our response to the training stimulus.
‘Train low’ has become a catchphrase that is surprisingly variable in the scientific literature and does not refer to one specific nutritional state. In a general sense, ‘train low’ refers to training with limited or low carbohydrate availability. This could be the result of training with low liver and muscle glycogen stores (AKA endogenous carbohydrate availability) or the result of inadequate carbohydrate intake before and/or during longer training sessions (AKA exogenous carbohydrate availability). The thought behind training low is that it provides the stimulus to up-regulate lipid oxidation pathways and ‘spare’ the body’s glycogen stores. This is based upon the well-understood fact that when our bodies becomes depleted of glycogen and do not have exogenous carbohydrate available, that athletes quickly experience fatigue. This can significantly impair performance and is often experienced as ‘hitting the wall’ or ‘running out of fuel.’
The concept backing all of this research is that carbohydrate is the muscle’s preferred energy source. It is the most efficient substrate to provide ATP for the muscle, or the currency of the cell. Lipids (= fat) can be broken down for energy but require oxygen and are an important energy source for cardio exercise. But, at high intensities when oxygen availability is limited, the body relies upon stored and exogenous carbohydrate. If carbohydrate is not available, exercise intensity and duration quickly becomes limited.
If we can ‘spare’ muscle glycogen (save it for later), we can delay that experience of running out of fuel. Thus, training the body to burn fat at higher intensities sounds great, since it would spare us the need to rely upon carbohydrate.
Indeed, studies have shown that when training ‘low’ (whether from low endogenous stores, or from limited exogenous carbohydrate availability), there are physiological adaptations that enhance fat oxidation. Specifically, we see enhanced activation of cellular signaling pathways and up-regulation of cellular enzymes required for fat oxidation. Unfortunately, there are also some challenges with chronically training low (such as what would happen in a ketogenic or lower carbohydrate/Paleo‘ish’ diet).
First, in the face of chronic low carbohydrate availability, an athlete is likely to be unable to sustain a higher training intensity level (since carbohydrates are needed to fuel these high intensity exercises). This would result in poorer training adaptations Secondly, both long duration and high-intensity training undergone consistently with low carbohydrate availability (such as when following a low carbohydrate diet) can make an athlete more susceptible to illness and infection; this is related to carbohydrate’s role in off-setting exercise-induced immunosuppression. We also see increased muscle protein breakdown in those chronically exercising in the presence of low carbohydrate availability. I cannot imagine any athlete wanting to promote great muscle protein breakdown! Eventually this could lead to decreased skeletal muscle mass. Finally, chronically training in this states actually down-regulates the body’s ability to oxidize carbohydrate. So, for the athlete who perpetually trains low, but then consumes a lot of carbohydrates right before a key event is likely to be significantly less efficient at being able to utilize those carbohydrates they just consumed. Bummer.
What to do? First, it should be noted that as of yet, there are no quality scientific studies that actually show a benefit of low carbohydrate/ketogenic diets on performance, and especially not on exercise done at higher intensities (such as CrossFit). However, this does not mean that there may not be benefit to training smart, instead of training low. By this, I would suggest (as would many sports dietitians) that undergoing key training sessions with low carbohydrate availability may be a smart strategy. This will support improved fat oxidation and all of the cellular and metabolic adaptations outlined above.
However, being ‘smart’ is the name of the game here. If you are undergoing an important, key training session where you want to optimize your training capacity and consequent training stimulus, you want to start that session with optimized carbohydrate stores (training ‘high’). This is done by consuming adequate carbohydrates (see Icon nutrition calculator for recommendations) in the 24 hours leading up to the training session, and ensuring you’ve consumed a carbohydrate-rich snack or meal in the few hours before training.
If, however, you are undergoing a second training session that day, for example, that will be of less importance (a lower training load) or of low to moderate intensity that is not prolonged, you likely can afford to enter that training session ‘low’ by not replacing the carbohydrates you previously burned. That is, your recovery nutrition in between the 2 training sessions can be low in carbohydrates so that you enter the second session low. Other practical strategies to training ‘low’ include training in the fasted state, or restricting carbohydrate intake in the post-recovery period.
Other tips to facilitate the process of training low for particular sessions is to consider consumption of caffeine (such as what would be consumed in a cup of coffee) and/or carbohydrate mouth rinse that is not actually swallowed before training; research indicates this can be registered by the central nervous system from sensors in the mouth and can stimulate some of the benefits achieved from actually consuming carbohydrate. This may help to achieve higher training intensities in the face of low carbohydrate availability. Additionally, when training ‘low’, athletes should consume 20-25 grams of protein before, during, or immediately after training to attenuate muscle protein breakdown and to stimulate muscle protein synthesis that is otherwise more likely to occur when training low.
Keep in mind, training low should only be considered for less important training sessions that include a lower training volume and decreased intensity. Athletes should continue to train ‘high’ for important, key training sessions. For athletes hoping to enter competition, training ‘high’ should be undertaken during training sessions that mimic competition – that is, practice training with a carbohydrate-rich meal that will be similar to what is consumed before competition and even practicing different carbohydrate-rich meals that can be consumed in the 24 hours prior to competition. This all supports positive training adaptations and avoids any ‘surprises’ on game day.
Alright, that was a lot of info… What questions do you have?!?