Acute Carbohydrate Strategies for Resistance Training Performance

Abstract

Carbohydrate (CHO) is critical for moderate-to-high-intensity exercise; however, its relevance to resistance training (RT) performance is unclear due to inconsistent findings, limited mechanistic evidence, and overreliance on endurance-based nutritional guidelines. This thesis elucidates the role of CHO ingestion and mouth rinsing (CMR) as potential ergogenic aids for RT performance by integrating systematic evaluation and update of the literature (Chapters 2 - 4); characterisation of applied nutrition practices in RT-centric athletes (Chapters 5 & 6); and experimental cross-over trials (Chapters 7 & 8), including preliminary evidence of acute CHO ingestion’s influence on subcellular glycogen utilisation during RT (Chapter 8).

A systematic review and meta-analysis were conducted to quantify the acute effects of CHO on RT performance and identify ergogenic response moderators (Chapter 2). Across studies with varying designs, CHO produced small improvements in total session volume when pre-exercise fasts exceeded 8 hours, and large improvements when session durations exceeded 45 minutes. An updated meta-analysis (Chapter 3) incorporating recently published trials and corrected data extractions refined these estimates as a small effect across the same sub-groups.

A network meta-analysis was subsequently conducted to rigorously synthesise CMR data for acute RT outcomes (Chapter 4). The network structure allowed for the simultaneous modelling of multiple active comparators (e.g., CMR with maltodextrin, glucose, or maltose) and non-active comparators (e.g., taste matched placebo and water only rinses, or no-rinse control). Relative to placebo, CMR did not improve maximal dynamic strength but produced moderate and small effects on peak force and total session volume, respectively.

Two international surveys characterised the general and peri-workout nutrition practices of drug-tested powerlifters (Chapters 5 & 6). Athletes periodised their nutrition across training phases and reported peri-workout nutrition strategies broadly aligned with sport nutrition guidelines. Pre-training nutrition was prioritised, with many athletes consuming CHO-containing meals before RT, with general and peri-workout CHO practices varying by sex, weight class, age class, and competitive calibre.

To test whether CHO ingestion, independent of energy provision, enhances RT performance, a double-blind, isoenergetic, cross-over trial compared high-CHO (1.2 g/kg), low-CHO (0.3 g/kg), and calorie-less placebo breakfasts before a ~90-min, high-volume RT session (Chapter 7). Volume performance did not differ between conditions, indicating performance may not be sensitive to CHO dose when EI and expectancy are controlled.

Finally, a case series examined the effects of acute CHO ingestion versus an energy-matched placebo on high-volume lower-body RT volume and total and subcellular glycogen compartments (Chapter 8). Preliminary data suggest an ergogenic effect of CHO on volume performance. Total muscle glycogen decreased by approximately 50 - 77% from pre- to post-exercise, representing a substantially greater depletion than previously reported in the literature. Subcellular glycogen depots exhibited similarly large pre- to post-exercise reductions, and neither total nor subcellular glycogen measures demonstrated consistent differences between high- and low-carbohydrate conditions.

Collectively, this thesis clarifies the contextual role of CHO ingestion and CMR as potential RT ergogenic aids, advances their mechanistic understanding through novel subcellular analyses, and provides applied insights informing RT-specific sport nutrition guidelines.