Protein and the Adaptive Response With Endurance Training: Wishful Thinking or a Competitive Edge?

Abstract

The significance of carbohydrates for endurance training has been well established, whereas the role of protein and the adaptive response with endurance training is unclear. Therefore, the aim of this perspective is to discuss the current evidence on the role of dietary protein and the adaptive response with endurance training. On a metabolic level, a single bout of endurance training stimulates the oxidation of several amino acids. Although the amount of amino acids as part of total energy expenditure during exercise is relatively low compared to other substrates (e.g., carbohydrates and fat), it may depress the rates of skeletal muscle protein synthesis, and thereby have a negative effect on training adaptation. A low supply of amino acids relative to that of carbohydrates may also have negative effects on the synthesis of capillaries, synthesis and turn-over of mitochondrial proteins and proteins involved in oxygen transport including hamoglobin and myoglobin. Thus far, the scientific evidence demonstrating the significance of dietary protein is mainly derived from research with resistance exercise training regimes. This is not surprising since the general paradigm states that endurance training has insignificant effects on skeletal muscle growth. This could have resulted in an underappreciation of the role of dietary protein for the endurance athlete. To conclude, evidence of the role of protein on endurance training adaptations and performance remains scarce and is mainly derived from acute exercise studies. Therefore, future human intervention studies must unravel whether dietary protein is truly capable of augmenting endurance training adaptations and ultimately performance.

Supplement with whey protein hydrolysate in contrast to carbohydrate supports mitochondrial adaptations in trained runners

“…Hence, the international society of sports nutrition recommends endurance athletes to consume a high CHO diet containing 8-12 g of CHO kg − 1 day − 1 to maximize the endogenous glycogen stores and 1.2 g kg − 1 h − 1 following strenuous exercise to replenish the glycogen stores [2]. Additionally, within the last decade attention has been given to protein (PRO), due to its possible role in maximizing the adaptational responses to endurance training [3]. Endurance training is characterized by repetitive, relatively low power output muscle contractions performed over a prolonged period, causing a metabolic and mechanical stress on the muscle [4].…”

“…Stress, which may cause myofibrillar disruption, and activation of signaling pathways which enhance myofibrillar and mitochondrial muscle protein synthesis (MPS) [4]. Thus, in order to provide amino acids for skeletal muscle accretion, a protein intake above the recommended level for sedentary or moderately active people (RDA; 0.8 g protein kg − 1 d − 1 ) is suggested to improve recovery [5], but also trainings adaptations [3]. Furthermore, within recent years, a number of studies have demonstrated that high volume endurance exercise increase whole body amino acid oxidation and enhance the need for protein up to 1.8 g of PRO kg − 1 day − 1 [6,7].…”

Supplement with whey protein hydrolysate in contrast to carbohydrate supports mitochondrial adaptations in trained runners

“…Hence, the international society of sports nutrition recommends endurance athletes to consume a high CHO diet containing 8-12 g of CHO kg -1 day -1 to maximize the endogenous glycogen stores and 1.2 g kg -1 h -1 following strenuous exercise to replenish the glycogen stores (2). Additionally, within the last decade attention has been given to protein (PRO), due to its possible role in maximizing the adaptational responses to endurance training (3). Endurance training is characterized by repetitive, relatively low power output muscle contractions performed over a prolonged period, causing a metabolic and mechanical stress on the muscle (5).…”

“…Stress, which may cause myo brillar disruption, and activation of signaling pathways which enhance myo brillar and mitochondrial muscle protein synthesis (MPS) (5). Thus, in order to provide amino acids for skeletal muscle accretion, a protein intake above the recommended level for sedentary or moderately active people (RDA; 0.8 g protein kg -1 d -1 ) is suggested to improve recovery (6), but also trainings adaptations (3). Furthermore, within recent years, a number of studies have demonstrated that high volume endurance exercise increase whole body amino acid oxidation and enhance the need for protein up to 1.8 g of PRO kg -1 day -1 (7,8).…”

Supplement With Whey Protein Hydrolysate in Contrast to Carbohydrate Supports Mitochondrial Adaptations in Trained Runners

“…Stress, which may cause myo brillar disruption, but also induce activation of signaling pathways which enhance myo brillar and mitochondrial muscle protein synthesis (MPS) and thereby tissue remodeling and mitochondrial biogenesis (5). Thus, in order to provide amino acids for skeletal muscle accretion, a protein intake above the recommended level for sedentary or moderately active people (RDA; 0.8 g protein kg − 1 d − 1 ) is suggested to improve recovery (6), but also trainings adaptations (3). Furthermore, within recent years, a number of studies have demonstrated that high volume endurance exercise increase whole body amino acid oxidation and enhance the need for protein up to 1.8 g of PRO kg − 1 day − 1 (7,8).…”