The Effect of a Moderately Low and High Carbohydrate Intake on Crossfit Performance

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Abstract

CrossFit is a metabolically demanding strength and conditioning method which performance may benefit from a carbohydrate (CHO)-rich diet. This study investigated the effect of three consecutive days of high CHO intake on CrossFit performance and corresponding metabolically -related variables in strength trained individuals. Eighteen subjects with a CHO intake of <6 g/kg/day were randomly assigned into a CHO (n = 9) or control (C) group (n =9) and underwent a 9-day training protocol. During days 1, 5, and 9, performance was measured as repetitions completed during a 12 minute CrossFit workout. Oxygen consumption (VO ₂), respiratory exchange ratio (RER), and blood lactate (BL) were also measured. Days 6–8, the CHO group increased CHO intake from <6 g/kg/day to 6–8 g/kg/day; the C group maintained their current intake of <6 g/kg/day. On days 6 and 7 both groups performed CrossFit workouts followed by a day of rest prior to day 9. There was a significant increase in repetitions completed in both groups in day 9 (vs. means score of day 1 + 5) (p = 0.002), but no differences between C and CHO groups (p = 0.111). However, the CHO group displayed a 15.2 repetition increase (+10.9%) in day 9, compared to 5.7 (+4.2%) by the C group. VO ₂, RER, and BL were not influenced by the experimental intervention. Our results suggest that the CrossFit-embraced practice of moderately-low CHO diets may be adequate in CHO during short periods of training, however, given the noted trend, extended training periods may be effected.

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Nutrition for endurance sports: marathon, triathlon, and road cycling.

Asker Jeukendrup (2011)

Endurance sports are increasing in popularity and athletes at all levels are looking for ways to optimize their performance by training and nutrition. For endurance exercise lasting 30 min or more, the most likely contributors to fatigue are dehydration and carbohydrate depletion, whereas gastrointestinal problems, hyperthermia, and hyponatraemia can reduce endurance exercise performance and are potentially health threatening, especially in longer events (>4 h). Although high muscle glycogen concentrations at the start may be beneficial for endurance exercise, this does not necessarily have to be achieved by the traditional supercompensation protocol. An individualized nutritional strategy can be developed that aims to deliver carbohydrate to the working muscle at a rate that is dependent on the absolute exercise intensity as well as the duration of the event. Endurance athletes should attempt to minimize dehydration and limit body mass losses through sweating to 2-3% of body mass. Gastrointestinal problems occur frequently, especially in long-distance races. Problems seem to be highly individual and perhaps genetically determined but may also be related to the intake of highly concentrated carbohydrate solutions, hyperosmotic drinks, as well as the intake of fibre, fat, and protein. Hyponatraemia has occasionally been reported, especially among slower competitors with very high intakes of water or other low sodium drinks. Here I provide a comprehensive overview of recent research findings and suggest several new guidelines for the endurance athlete on the basis of this. These guidelines are more detailed and allow a more individualized approach.

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The effect of protein timing on muscle strength and hypertrophy: a meta-analysis

Brad Jon Schoenfeld, Alan Aragon, James Krieger (2013)

Protein timing is a popular dietary strategy designed to optimize the adaptive response to exercise. The strategy involves consuming protein in and around a training session in an effort to facilitate muscular repair and remodeling, and thereby enhance post-exercise strength- and hypertrophy-related adaptations. Despite the apparent biological plausibility of the strategy, however, the effectiveness of protein timing in chronic training studies has been decidedly mixed. The purpose of this paper therefore was to conduct a multi-level meta-regression of randomized controlled trials to determine whether protein timing is a viable strategy for enhancing post-exercise muscular adaptations. The strength analysis comprised 478 subjects and 96 ESs, nested within 41 treatment or control groups and 20 studies. The hypertrophy analysis comprised 525 subjects and 132 ESs, nested with 47 treatment or control groups and 23 studies. A simple pooled analysis of protein timing without controlling for covariates showed a small to moderate effect on muscle hypertrophy with no significant effect found on muscle strength. In the full meta-regression model controlling for all covariates, however, no significant differences were found between treatment and control for strength or hypertrophy. The reduced model was not significantly different from the full model for either strength or hypertrophy. With respect to hypertrophy, total protein intake was the strongest predictor of ES magnitude. These results refute the commonly held belief that the timing of protein intake in and around a training session is critical to muscular adaptations and indicate that consuming adequate protein in combination with resistance exercise is the key factor for maximizing muscle protein accretion.

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Recovery of power output and muscle metabolites following 30 s of maximal sprint cycling in man.

G Bogdanis, M E Nevill, L Boobis … (1995)

1. The recovery of power output and muscle metabolites was examined following maximal sprint cycling exercise. Fourteen male subjects performed two 30 s cycle ergometer sprints separated by 1.5, 3 and 6 min of recovery, on three separate occasions. On a fourth occasion eight of the subjects performed only one 30 s sprint and muscle biopsies were obtained during recovery. 2. At the end of the 30 s sprint phosphocreatine (PCr) and ATP contents were 19.7 +/- 1.2 and 70.5 +/- 6.5% of the resting values (rest), respectively, while muscle lactate was 119.0 +/- 4.6 mmol (kg dry wt)-1 and muscle pH was 6.72 +/- 0.06. During recovery, PCr increased rapidly to 65.0 +/- 2.8% of rest after 1.5 min, but reached only 85.5 +/- 3.5% of rest after 6 min of recovery. At the same time ATP and muscle pH remained low (19.5 +/- 0.9 mmol (kg dry wt)-1 and 6.79 +/- 0.02, respectively). Modelling of the individual PCr resynthesis using a power function curve gave an average half-time for PCr resynthesis of 56.6 +/- 7.3 s. 3. Recovery of peak power output (PPO), peak pedal speed (maxSp) and mean power during the initial 6 s (MPO6) of sprint 2 did not reach the control values after 6 min of rest, and occurred in parallel with the resynthesis of PCr, despite the low muscle pH. High correlations (r = 0.71-0.86; P 0.05). 4. These data suggest that PCr resynthesis after 30 s of maximal sprint exercise is slower than previously observed after dynamic exercise of longer duration, and PCr resynthesis is important for the recovery of power during repeated bouts of sprint exercise.

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Author and article information

Journal

Journal ID (nlm-ta): Int J Exerc Sci

Journal ID (iso-abbrev): Int J Exerc Sci

Title: International Journal of Exercise Science

Publisher: Berkeley Electronic Press

ISSN (Electronic): 1939-795X

Publication date Collection: 2016

Publication date (Electronic): 1 October 2016

Volume: 9

Issue: 3

Pages: 460-470

Affiliations

[1 ]Department of Health, Exercise & Sport Sciences, University of New Mexico, Albuquerque, New Mexico, USA

[2 ]Department of Kinesiology, California State University, Fresno, Fresno, California, USA

[3 ]Department of Exercise Science & Sports Management, Kennesaw State University, Kennesaw, Georgia, USA

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[†]

Denotes graduate student author

[‡]

Denotes professional author

Article

Publisher ID: ijes_09_04_460

DOI: 10.70252/IZLO1608

PMC ID: 5065325

PubMed ID: 27766133

SO-VID: d5c4d3f9-08f6-4465-94a3-868bcff4d616

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The Effect of a Moderately Low and High Carbohydrate Intake on Crossfit Performance

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Most cited references 33

Nutrition for endurance sports: marathon, triathlon, and road cycling.

The effect of protein timing on muscle strength and hypertrophy: a meta-analysis

Recovery of power output and muscle metabolites following 30 s of maximal sprint cycling in man.

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