Crossfit is a method that physically and metabolically requires strength and conditioning, whose ultimate goal is to maximize power. It incorporates gymnastics, strength training, aerobic training and high-power cardiorespiratory activities in various combinations, loads and repetitions that last from 5 minutes to 30-45 minutes (ESCOBAR, ET AL, 2016).
Crossfit workouts result in a heart rate of approximately 90% of the maximum rate and aerobic intensities of around 85% of the VO2max, with variables in the types of training that can exceed the intensities of the VO2max for short but repeated periods of time. This requires a high demand on glycolytic metabolism for energy production, with a high degree of glycogen utilization. According to Escobar et al, 2016, athletes with heavy anaerobic training may require more than 8-10 g/cho/day/kg of weight or 60 to 70% of energy consumption. Other recommendations are around 4 to 7 g/cho/day/kg of weight or 55 to 60%, with total energy consumption depending on the training phase. Now! The Endurance Recommendation can reach up to 12 g/cho/day/kg in weight.
The effects of CHO on performance can be partially attributed to influences on the central nervous system and associated with a lower perception of effort, in addition to the improvement of the effective response to training and a greater recruitment of motor units for muscle work, these main mechanisms being responsible for the ergogenic effects of CHO during short-duration events (BAUR, ET AL, 2021; ROLLO, ET AL, 2020).
According to Rountree, et al 2017, Actual intake of CHO during the crossfit section could reduce the rate of glycogen depletion, as well as provide an additional fuel source to maintain or improve performance.
It is known that in fasting, CHO stores, mainly muscle glycogen and blood glucose (derived from liver glycogen stores and gluconeogenesis) are predominantly used as an energy substrate for muscle work at moderate and/or intense intensities. Depletion of endogenous CHO stores has been shown to contribute to fatigue and impairs exercise capacity. Therefore, increasing the availability of carbohydrates generates greater conservation of muscle and liver glycogen, better maintaining the capacity to generate energy, greater tolerance to effort and resistance to fatigue, generating increases in performance (BAUR ET AL., 2021; ROLL, ET AL., 2020).
Regarding supplementation, it is widely documented that the combination of more than one type of carbohydrate (glucose, fructose, maltodextrin) is more efficient from a performance point of view because it improves absorption capacity in the gastrointestinal tract, reduces malabsorption and symptoms of gastrointestinal distress, has better gastric emptying and activates a greater amount of glucose transporters, which favors a greater amount of absorption and a better oxidation rate of this substrate, approximately 40% more, promoting thus a better resynthesis of muscle and liver glycogen stores in a post-exercise condition, which would directly affect muscle recovery (BAUR, ET AL, 2021; ROLLO, ET AL, 2020).
Glycogen resynthesis is also greatly influenced by the period and amount of carbohydrates and nutrients consumed by patients. The recovery of glycogen stores is maximal when CHO is consumed within the first 2 hours of recovery, but then they decrease due to the attenuation of the GLUT 4 translocation. Therefore, the administration of CHO immediately after training can improve recovery, especially in cases of simultaneous consumption of proteins together with carbohydrates after training. through the insulinemic response. Studies show that protein intake along with CHO can also improve post-exercise recovery markers, such as muscle reconstruction, muscle degradation, and muscle pain, compared to consuming CHO alone.
Another influence of CHO on exercise is at the intestinal level. During exercise, there is a reduction in blood flow to the gastrointestinal tract, inducing a common condition called splanchnic hypoperfusion, which causes a rapid increase in plasma concentrations of intestinal fatty acid-binding proteins (I-FABP), a marker of cell turnover and epithelial integrity. Ingestion of CHO before or during exercise reduces this hypoperfusion and prevents increased plasma concentrations of I-FABP., where CHO plays a role in regulating the integrity of intestinal epithelial cells, implying less damage to intestinal health and inflammation (ROLLO, ET AL, 2021).
One supplement that can also interact positively with carbohydrates is caffeine. Studies show that caffeine can act to preserve glycogen, enhance fat oxidation, improve motor pattern and force production, and several studies indicate that caffeine increases the delivery of exogenous CHO to the muscle, both by increasing absorption rates and by oxidizing CHO, and can also be used as a post-exercise strategy (2 mg/kg of weight) to improve muscle recovery and analgesic effects (BAUR, ET AL, 2020).
References:
1. Rountree JA, Krings BM, Peterson TJ, Thigpen AG, McAllister MJ, Holmes ME, Smith JW. Effectiveness of carbohydrate ingestion on CrossFit exercise performance. Sports (Basel). August 14, 2017; 5 (3) :61. doi: 10.3390/sports5030061. PMID: 29910421; PMC5968949.
2. Escobar KA, Morales J, Vandusseldorp TA. The effect of moderately low and high carbohydrate intake on Crossfit performance. Int J Exerc Sci. October 16, 2016; 9 (3) :460-470. PMID: 27766133; PMCID: PMC5065325.
3. Baur DA, Saunders MJ. Carbohydrate supplementation: a critical review of recent innovations. Euro J Apple Physiol. 2021 January; 121 (1) :23-66. doi:10.1007/s00421-020-04534-y. Electronic publication of October 27, 2020. PMID: 33106933.
4. Rollo I, Gonzalez JT, Fuchs CJ, van Loon LJC, Williams C. Primary, secondary and tertiary effects of carbohydrate ingestion during exercise. Sports Med. November 2020; 50 (11) :1863-1871. doi:10.1007/s40279-020-01343-3. Errata in: Sports Med. 2021 Dec; 51 (12) :2671. doi:10.1007/s40279-021-01489-8. PMID: 32936440; PMCID: PMC8159838.