Toward a Common Understanding of Diet–Exercise Strategies to Manipulate Fuel Availability for Training and Competition Preparation in Endurance Sport

Abstract

From the breakthrough studies of dietary carbohydrate and exercise capacity in the 1960s through to the more recent studies of cellular signaling and the adaptive response to exercise in muscle, it has become apparent that manipulations of dietary fat and carbohydrate within training phases, or in the immediate preparation for competition, can profoundly alter the availability and utilization of these major fuels and, subsequently, the performance of endurance sport (events >30 min up to ∼24 hr). A variety of terms have emerged to describe new or nuanced versions of such exercise–diet strategies (e.g., train low, train high, low-carbohydrate high-fat diet, periodized carbohydrate diet). However, the nonuniform meanings of these terms have caused confusion and miscommunication, both in the popular press and among the scientific community. Sports scientists will continue to hold different views on optimal protocols of fuel support for training and competition in different endurance events. However, to promote collaboration and shared discussions, a commonly accepted and consistent terminology will help to strengthen hypotheses and experimental/experiential data around various strategies. We propose a series of definitions and explanations as a starting point for a more unified dialogue around acute and chronic manipulations of fat and carbohydrate in the athlete’s diet, noting philosophies of approaches rather than a single/definitive macronutrient prescription. We also summarize some of the key questions that need to be tackled to help produce greater insight into this exciting area of sports nutrition research and practice.

Contemporary Nutrition Strategies to Optimize Performance in Distance Runners and Race Walkers

“…This is at least partly attributable to different definitions or inaccurate descriptions of the implementation or goals of these strategies. A recent commentary has promoted the case for a common terminology and understanding of this theme (Burke et al, 2018c). In the meantime, it appears that elite athletes include various versions of "train high," "train low," and "gut training" within their training programs, both accidentally and intentionally (Heikura et al, 2018;Stellingwerff, 2012).…”

“…Meanwhile, meals are consumed soon after training sessions, and high-intensity track sessions are completed as a midmorning workout after breakfast. Indeed, many concepts of periodizing CHO availability according to the needs of the session (Burke et al, 2018c) appear within these traditional practices. Although supplements are rarely used, data from observational studies (Beis et al, 2012) and accounts of recent attempts on world marathon records by male runners (Caesar, 2017;Hutchinson, 2013) note personalized race nutrition plans including proactive intakes of fluid and CHO, often with the involvement of Western sports scientists.…”

Post‐exercise carbohydrate and energy availability induce independent effects on skeletal muscle cell signalling and bone turnover: implications for training adaptation

“…The concept of deliberately promoting reduced carbohydrate (CHO) availability to enhance endurance training induced adaptations of skeletal muscle (i.e. the 'train-low' paradigm) is gaining increased acceptance amongst athletic populations (Bartlett et al 2015;Marquet et al 2016;Burke et al 2018;Stellingwerff et al 2019). Over the last decade, a multitude of research designs examining the train-low approach (e.g.…”

Acute and sustained effects of a periodized carbohydrate intake using the sleep‐low model in endurance‐trained males

“…Endogenous and exogenous carbohydrate (CHO) availability during exercise are important factors for endurance performance . Since human CHO stores represent a limited energy source compared to fat, a variety of diet‐exercise strategies to improve fat oxidation rate and endurance performance have been investigated, primarily in endurance‐trained populations . The overall theoretical rationale for this is that increased reliance on fat as fuel during exercise decreases utilization of glycogen, which then will be available for use when more intense work is demanded at the end of a race lasting several hours (>4 hours) .…”