As a performance coach, you have probably heard of the interference effect observed during concurrent training. The interference effect states that endurance signaling stunts muscle growth and adaptations from strength training. This poses a problem to the performance coach working with team sports as the physiological demands of these sports require high levels of both strength-power and endurance. Born from this are concurrent training sessions where conditioning and lifting are performed within the same training session. Since 1980, when research was first published showing endurance training negatively impacting strength adaptations in untrained subjects, the concept has been repeatedly studied. The subsequent literature has been mixed. Some research has even demonstrated concurrent training can be complimentary or potentially enhance adaptations. However, some research still favors the hypothesis that concurrent training can compromise resistance training adaptations—the crux of why is based on the molecular signaling from the two divergent training styles.
Endurance and resistance training both have specific molecular pathways that induce adaptations. Endurance training is associated with the AMPK pathway, stimulating mitochondrial biogenesis, while strength training is associated with the mTOR pathway, stimulating muscular hypertrophy. While both pathways have their benefits, in a vacuum, it is probably in the athlete's best interest to minimize the crosstalk from these two pathways to get the most out of their training. Theoretically, separating strength-power and conditioning sessions into separate days or sessions within a day would arguably be the best practice. In reality, most performance settings are not equipped to do this from a time and logistical standpoint. Rather than overthinking how to implement the best concurrent training sessions, a straightforward solution is hidden in plain sight. That solution, as you may have already guessed, is nutrition. Specific nutrients very much influence both pathways.
The role of nutrition and fuel availability is intricately tied to the upregulation of the AMPK pathway. The AMPK pathway is sensitive to fuel availability, specifically carbohydrates and muscle glycogen. Carbohydrate periodization application is rooted in the ability of carbohydrate availability to influence the AMPK pathway. In conditions of low carbohydrate availability, the AMPK pathway is upregulated, leading to increased mitochondria within the muscle. These findings led to “train low” and “recover low” sports nutrition strategies. These strategies often entail twice-a-day endurance training sessions where athletes perform a high-intensity glycogen depletion session followed by the absence of carbohydrates. In the morning, athletes perform a fasted/glycogen-depleted low-intensity session. Despite this protocol leading to increased mitochondrial biogenesis, improved fat oxidation, and increased autophagy, there still is no definitive link between these mechanisms and specific outcomes, i.e., improved performance. We can take from this the importance of carbohydrates in concurrent training sessions. Carbohydrate availability can certainly diminish the impact of AMPK, negatively impacting muscular adaptations from strength-power sessions. Therefore, sufficient carbohydrate intake before and during concurrent training sessions is the best practice. Another potential drawback of endurance training is that it leads to protein degradation of muscles. Protein degradation is a consequence of both types of training. While protein degradation is necessary for muscle growth, endurance, and interval training lack the mechanical tension required for muscle growth, bringing us to our next nutrient of importance: protein.
The role of protein in concurrent training is twofold. Adequate protein intake in and around activity provides athletes with the amino acids necessary to repair the muscle breakdown from both forms of training. In addition, the amino acid leucine initiates the mTOR pathway. The mTOR pathway is responsible for initiating muscle growth. Two to three grams of the essential amino acid leucine has been routinely found to “turn on” the mTOR pathway switch. This can be accomplished with 20-30 grams of a complete protein source. Carbohydrates also have a role in promoting positive adaptations to strength-power training. In the absence of carbohydrates, the body can utilize amino acids from muscle tissue to provide energy. This is not optimal given that this training is already breaking down muscle tissue; therefore, proper adequate carbohydrate availability is both muscle-sparing and performance-enhancing.
When looking at the research on the interference effect, rarely, if ever, is diet controlled in any of the subjects. While we looked into the scientific side of the interference effect and the role nutrition has, the recommendations it leads to are nothing groundbreaking. It falls right in line with standard performance nutrition recommendations for training sessions. Take an assessment of your setting as a strength coach or sports dietitian. How compliant are your athletes with your fueling and recovery recommendations? Do you find a way to ensure there is both time and resources for the athletes you work with to consume carbohydrate sources before and during concurrent training sessions? Do you schedule a nutrition break between conditioning and lifting sessions for them to consume a protein source? Do you allow the athletes you work with to consume carbohydrates and protein while they are training? Are you putting the same amount of time into coaching, organizing, planning, and periodizing concurrent training sessions as you are to ensure they have the low-hanging fruit of proper nutrition to maximize training adaptation and performance?
Taking this a step forward, we can look more specifically at the college setting. Making this work in the college setting is all about when your meals and training sessions are.
Ensuring every training session is either preceded by or followed by a meal is a good start. In a perfect world, your training sessions are bookended by two meals. If you train in the morning, athletes consume breakfast before training and lunch soon after training. If you train in the afternoon, athletes consume lunch before training and dinner soon after. Throw in some intra-training protein and carbs, and you have a scenario where you mitigate most, if not all, of the interference effect you would experience from concurrent training sessions. If two meals are not an option, you might emphasize training sessions beginning when athletes consume both a quick and easily digestible carbohydrate and protein source that are easy on the stomach before training and a big meal following training. If you have a tough run or on-field session and lift following, protein before the run might be contraindicated. In this situation, you put a big emphasis on carbohydrates pre-run followed by protein and carbs post-run. Every school provides its unique challenges with dining halls, training tables, and nutrition resources, but with enough thought and effort, you can set your athletes up for some success with nutrition being the center of every training session.
For more information on this you can contact us at service@strengthcoachnetwork.com
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