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Trent Stellingwerff, James P. Morton and Louise M. Burke

Over the last decade, in support of training periodization, there has been an emergence around the concept of nutritional periodization. Within athletics (track and field), the science and art of periodization is a cornerstone concept with recent commentaries emphasizing the underappreciated complexity associated with predictable performance on demand. Nevertheless, with varying levels of evidence, sport and event specific sequencing of various training units and sessions (long [macrocycle; months], medium [mesocycle; weeks], and short [microcycle; days and within-day duration]) is a routine approach to training periodization. Indeed, implementation of strategic temporal nutrition interventions (macro, meso, and micro) can support and enhance training prescription and adaptation, as well as acute event specific performance. However, a general framework on how, why, and when nutritional periodization could be implemented has not yet been established. It is beyond the scope of this review to highlight every potential nutritional periodization application. Instead, this review will focus on a generalized framework, with specific examples of macro-, meso-, and microperiodization for the macronutrients of carbohydrates, and, by extension, fat. More specifically, the authors establish the evidence and rationale for situations of acute high carbohydrate availability, as well as the evidence for more chronic manipulation of carbohydrates coupled with training. The topic of periodized nutrition has made considerable gains over the last decade but is ripe for further scientific progress and field application.

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Louise M. Burke, John A. Hawley, Asker Jeukendrup, James P. Morton, Trent Stellingwerff and Ronald J. Maughan

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.