This interventional study examined the effect of a four-week vegan diet (VegD) during a four-week high-intensity functional training (HIFT) on performance, training results and blood biochemical indices in female (n = 12) and male (n = 8) moderate-trained CrossFit participants. The whole study group performed the maximum number of repetitions with a load of 70% one repetition-maximum (1RM) and a modified Fight Gone Bad (FGBMod) test before and after a dietary intervention (the group was divided to follow a VegD or a traditional mixed diet (MixD)) in a randomised and parallel design. Pre-exercise resting blood samples were also analysed. There was a significant improvement in the number of repetitions performed at a load corresponding to 70% of 1RM in the classic squat in the MixD group (p < 0.001), and in the classic deadlift in the VegD group (p = 0.014). Furthermore, there was a significant improvement in the results of the FGBMod performance test after a MixD. Moreover, an improvement in some exercises in the modified FGBMod test (Wall Ball after the VegD and the MixD, and rowing after the MixD) was also observed. However, differences between the MixD and the VegD groups were not clinically relevant. In conclusion, the short-term study conducted here indicated that a VegD in HIFT training positively affects strength endurance in the classic deadlift but is unlikely to be more beneficial in improving performance than a MixD.

Department of Physiology and Biochemistry Faculty of Physical Education and Sport Charles University 162 52 Prague Czech Republic

Department of Physiology and Biochemistry Poznań University of Physical Education 61 871 Poznan Poland

Department of Sports Dietetics Poznań University of Physical Education 61 871 Poznan Poland

Home of Body Training Studio AFB Marcelin Sp z o o 60 324 Poznan Poland

See more in PubMed

Craig W.J., Mangels A.R. American Dietetic Association Position of the American Dietetic Association: Vegetarian Diets. J. Am. Diet Assoc. 2009;109:1266–1282. PubMed

Lynch H., Johnston C., Wharton C. Plant-Based Diets: Considerations for Environmental Impact, Protein Quality, and Exercise Performance. Nutrients. 2018;10:1841. doi: 10.3390/nu10121841. PubMed DOI PMC

Melina V., Craig W., Levin S. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. J. Acad. Nutr. Diet. 2016;116:1970–1980. doi: 10.1016/j.jand.2016.09.025. PubMed DOI

Rogerson D. Vegan Diets: Practical Advice for Athletes and Exercisers. J. Int. Soc. Sports Nutr. 2017;14:36. doi: 10.1186/s12970-017-0192-9. PubMed DOI PMC

Wirnitzer K.C. Vegan Diet in Sports and Exercise–Health Benefits and Advantages to Athletes and Physically Active People: A Narrative Review. Int. J. Sports Exerc. Med. 2020;6:165.

Barnard N.D., Goldman D.M., Loomis J.F., Kahleova H., Levin S.M., Neabore S., Batts T.C. Plant-Based Diets for Cardiovascular Safety and Performance in Endurance Sports. Nutrients. 2019;11:130. doi: 10.3390/nu11010130. PubMed DOI PMC

Mondal H., Mishra S.P. Effect of BMI, Body Fat Percentage and Fat Free Mass on Maximal Oxygen Consumption in Healthy Young Adults. J. Clin. Diagn. Res. 2017;11:CC17–CC20. doi: 10.7860/JCDR/2017/25465.10039. PubMed DOI PMC

Schabort E.J., Killian S.C., St Clair Gibson A., Hawley J.A., Noakes T.D. Prediction of Triathlon Race Time from Labor-atory Testing in National Triathletes. Med. Sci. Sports Exerc. 2000;32:844–849. doi: 10.1097/00005768-200004000-00018. PubMed DOI

Durkalec-Michalski K., Podgórski T., Sokołowski M., Jeszka J. Relationship between Body Composition Indicators and Physical Capacity of the Combat Sports Athletes. Arch. Budo. 2016;12:247–256.

Durkalec-Michalski K., Nowaczyk P.M., Podgórski T., Kusy K., Osiński W., Jeszka J. Relationship between Body Composition and the Level of Aerobic and Anaerobic Capacity in Highly Trained Male Rowers. J. Sports Med. Phys. Fitness. 2019;59:1526–1535. doi: 10.23736/S0022-4707.19.08951-5. PubMed DOI

Feito Y., Heinrich K.M., Butcher S.J., Poston W.S.C. High-Intensity Functional Training (HIFT): Definition and Research Implications for Improved Fitness. Sports (Basel) 2018;6:76. doi: 10.3390/sports6030076. PubMed DOI PMC

Murawska-Cialowicz E., Wojna J., Zuwala-Jagiello J. Crossfit Training Changes Brain-Derived Neurotrophic Factor and Irisin Levels at Rest, after Wingate and Progressive Tests, and Improves Aerobic Capacity and Body Composition of Young Physically Active Men and Women. J. Physiol. Pharmacol. 2015;66:811–821. PubMed

Heinrich K.M., Patel P.M., O’Neal J.L., Heinrich B.S. High-Intensity Compared to Moderate-Intensity Training for Exer-cise Initiation, Enjoyment, Adherence, and Intentions: An Intervention Study. BMC Public Health. 2014;14:789. doi: 10.1186/1471-2458-14-789. PubMed DOI PMC

Buckley S., Knapp K., Lackie A., Lewry C., Horvey K., Benko C., Trinh J., Butcher S. Multimodal High-Intensity In-terval Training Increases Muscle Function and Metabolic Performance in Females. Appl. Physiol. Nutr. Metab. 2015;40:1157–1162. doi: 10.1139/apnm-2015-0238. PubMed DOI

Heinrich K.M., Spencer V., Fehl N., Poston W.S.C. Mission Essential Fitness: Comparison of Functional Circuit Training to Traditional Army Physical Training for Active Duty Military. Mil. Med. 2012;177:1125–1130. doi: 10.7205/MILMED-D-12-00143. PubMed DOI

Feito Y., Hoffstetter W., Serafini P., Mangine G. Changes in Body Composition, Bone Metabolism, Strength, and Skill-Specific Performance Resulting from 16-Weeks of HIFT. PLoS ONE. 2018;13:e0198324. doi: 10.1371/journal.pone.0198324. PubMed DOI PMC

Durkalec-Michalski K., Nowaczyk P.M., Główka N., Ziobrowska A., Podgórski T. Is a Four-Week Ketogenic Diet an Effective Nutritional Strategy in CrossFit-Trained Female and Male Athletes? Nutrients. 2021;13:864. doi: 10.3390/nu13030864. PubMed DOI PMC

Durkalec-Michalski K., Nowaczyk P.M., Siedzik K. Effect of a Four-Week Ketogenic Diet on Exercise Metabolism in CrossFit-Trained Athletes. J. Int. Soc. Sports Nutr. 2019;16:16. doi: 10.1186/s12970-019-0284-9. PubMed DOI PMC

Durkalec-Michalski K., Zawieja E.E., Zawieja B.E., Jurkowska D., Buchowski M.S., Jeszka J. Effects of Low Versus Moderate Glycemic Index Diets on Aerobic Capacity in Endurance Runners: Three-Week Randomized Controlled Crossover Trial. Nutrients. 2018;10:370. doi: 10.3390/nu10030370. PubMed DOI PMC

Kerksick C.M., Wilborn C.D., Roberts M.D., Smith-Ryan A., Kleiner S.M., Jäger R., Collins R., Cooke M., Davis J.N., Galvan E., et al. ISSN exercise & sports nutrition review update: Research & recommendations. J. Int. Soc. Sports Nutr. 2018;15:38. PubMed PMC

Teixeira V., Voci S.M., Mendes-Netto R.S., da Silva D.G. The Relative Validity of a Food Record Using the Smartphone Application MyFitnessPal. Nutr. Diet. 2018;75:219–225. doi: 10.1111/1747-0080.12401. PubMed DOI

Seo D.-I., Kim E., Fahs C.A., Rossow L., Young K., Ferguson S.L., Thiebaud R., Sherk V.D., Loenneke J.P., Kim D., et al. Reliability of the One-Repetition Maximum Test Based on Muscle Group and Gender. J. Sports Sci. Med. 2012;11:221–225. PubMed PMC

Durkalec-Michalski K., Zawieja E.E., Podgórski T., Łoniewski I., Zawieja B.E., Warzybok M., Jeszka J. The Effect of Chronic Progressive-Dose Sodium Bicarbonate Ingestion on CrossFit-like Performance: A Double-Blind, Randomized Cross-over Trial. PLoS ONE. 2018;13:e0197480. doi: 10.1371/journal.pone.0197480. PubMed DOI PMC

Durkalec-Michalski K., Zawieja E.E., Zawieja B.E., Podgórski T. Evaluation of the Repeatability and Reliability of the Cross-Training Specific Fight Gone Bad Workout and Its Relation to Aerobic Fitness. Sci. Rep. 2021;11:7263. doi: 10.1038/s41598-021-86660-x. PubMed DOI PMC

Podgorski T., Bartkowiak U., Pawlak M. Comparison of Hematological Parameters of Venous and Capillary Blood in Athletes. Trends Sport Sci. 2014;21:31–45.

Wirnitzer K., Motevalli M., Tanous D.R., Gregori M., Wirnitzer G., Leitzmann C., Hill L., Rosemann T., Knechtle B. Supplement Intake in Recreational Vegan, Vegetarian, and Omnivorous Endurance Runners-Results from the NURMI Study (Step 2) Nutrients. 2021;13:2741. doi: 10.3390/nu13082741. PubMed DOI PMC

Banaszek A., Townsend J.R., Bender D., Vantrease W.C., Marshall A.C., Johnson K.D. The Effects of Whey vs. Pea Protein on Physical Adaptations Following 8-Weeks of High-Intensity Functional Training (HIFT): A Pilot Study. Sports (Basel) 2019;7:12. doi: 10.3390/sports7010012. PubMed DOI PMC

Hartman J.W., Tang J.E., Wilkinson S.B., Tarnopolsky M.A., Lawrence R.L., Fullerton A.V., Phillips S.M. Consumption of Fat-Free Fluid Milk after Resistance Exercise Promotes Greater Lean Mass Accretion than Does Consumption of Soy or Car-bohydrate in Young, Novice, Male Weightlifters. Am. J. Clin. Nutr. 2007;86:373–381. doi: 10.1093/ajcn/86.2.373. PubMed DOI

Joy J.M., Lowery R.P., Wilson J.M., Purpura M., De Souza E.O., Wilson S.M., Kalman D.S., Dudeck J.E., Jäger R. The Effects of 8 Weeks of Whey or Rice Protein Supplementation on Body Composition and Exercise Performance. Nutr. J. 2013;12:86. doi: 10.1186/1475-2891-12-86. PubMed DOI PMC

Babault N., Païzis C., Deley G., Guérin-Deremaux L., Saniez M.-H., Lefranc-Millot C., Allaert F.A. Pea Proteins Oral Supplementation Promotes Muscle Thickness Gains during Resistance Training: A Double-Blind, Randomized, Place-bo-Controlled Clinical Trial vs. Whey Protein. J. Int. Soc. Sports Nutr. 2015;12:3. doi: 10.1186/s12970-014-0064-5. PubMed DOI PMC

Mangine G.T., Cebulla B., Feito Y. Normative Values for Self-Reported Benchmark Workout Scores in CrossFit® Practitioners. Sports Med. Open. 2018;4:39. doi: 10.1186/s40798-018-0156-x. PubMed DOI PMC

Outlaw J.J., Wilborn C.D., Smith-Ryan A.E., Hayward S.E., Urbina S.L., Taylor L.W., Foster C.A. Effects of a Pre-and Post-Workout Protein-Carbohydrate Supplement in Trained Crossfit Individuals. SpringerPlus. 2014;3:369. doi: 10.1186/2193-1801-3-369. PubMed DOI PMC

Kephart W.C., Pledge C.D., Roberson P.A., Mumford P.W., Romero M.A., Mobley C.B., Martin J.S., Young K.C., Lowery R.P., Wilson J.M., et al. The Three-Month Effects of a Ketogenic Diet on Body Composition, Blood Parameters, and Performance Metrics in CrossFit Trainees: A Pilot Study. Sports (Basel) 2018;6:1. doi: 10.3390/sports6010001. PubMed DOI PMC

Craddock J.C., Probst Y.C., Peoples G.E. Vegetarian and Omnivorous Nutrition–Comparing Physical Performance. Int. J. Sport Nutr. Exerc. Metab. 2016;26:212–220. doi: 10.1123/ijsnem.2015-0231. PubMed DOI

Lederer A.-K., Maul-Pavicic A., Hannibal L., Hettich M., Steinborn C., Gründemann C., Zimmermann-Klemd A.M., Müller A., Sehnert B., Salzer U., et al. Vegan Diet Reduces Neutrophils, Monocytes and Platelets Related to Branched-Chain Amino Acids—A Randomized, Controlled Trial. Clin. Nutr. 2020;39:3241–3250. doi: 10.1016/j.clnu.2020.02.011. PubMed DOI

Venderley A.M., Campbell W.W. Vegetarian Diets: Nutritional Considerations for Athletes. Sports Med. 2006;36:293–305. doi: 10.2165/00007256-200636040-00002. PubMed DOI

Fuhrman J., Ferreri D.M. Fueling the Vegetarian (Vegan) Athlete. Curr. Sports Med. Rep. 2010;9:233–241. doi: 10.1249/JSR.0b013e3181e93a6f. PubMed DOI

Ostojic S.M., Ahmetovic Z. Weekly Training Volume and Hematological Status in Female Top-Level Athletes of Different Sports. J. Sports Med. Phys. Fitness. 2008;48:398–403. PubMed

Shaw N.S., Chin C.J., Pan W.H. A Vegetarian Diet Rich in Soybean Products Compromises Iron Status in Young Students. J. Nutr. 1995;125:212–219. PubMed

Snyder A.C., Dvorak L.L., Roepke J.B. Influence of Dietary Iron Source on Measures of Iron Status among Female Runners. Med. Sci. Sports Exerc. 1989;21:7–10. doi: 10.1249/00005768-198902000-00002. PubMed DOI

Nebl J., Schuchardt J.P., Ströhle A., Wasserfurth P., Haufe S., Eigendorf J., Tegtbur U., Hahn A. Micronutrient Status of Recreational Runners with Vegetarian or Non-Vegetarian Dietary Patterns. Nutrients. 2019;11:1146. doi: 10.3390/nu11051146. PubMed DOI PMC

Beard J.L., Burton J.W., Theil E.C. Purified ferritin and soybean meal can be sources of iron for treating iron deficiency in rats. J. Nutr. 1996;126:154–160. doi: 10.1093/jn/126.1.154. PubMed DOI

Chang Y.J., Jo M.Y., Hwang E.H., Park C.U., Kim K.S. Recovery from iron deficiency in rats by the intake of recombinant yeast producing human H-ferritin. Nutrition. 2005;21:520–524. doi: 10.1016/j.nut.2004.07.016. PubMed DOI

Trapp D., Knez W., Sinclair W. Could a Vegetarian Diet Reduce Exercise-Induced Oxidative Stress? A Review of the Literature. J. Sports Sci. 2010;28:1261–1268. doi: 10.1080/02640414.2010.507676. PubMed DOI

Yokoyama Y., Levin S.M., Barnard N.D. Association between Plant-Based Diets and Plasma Lipids: A Systematic Review and Meta-Analysis. Nutr. Rev. 2017;75:683–698. doi: 10.1093/nutrit/nux030. PubMed DOI PMC

Wang F., Zheng J., Yang B., Jiang J., Fu Y., Li D. Effects of Vegetarian Diets on Blood Lipids: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J. Am. Heart Assoc. 2015;4:e002408. doi: 10.1161/JAHA.115.002408. PubMed DOI PMC

Fontana L., Meyer T.E., Klein S., Holloszy J.O. Long-Term Low-Calorie Low-Protein Vegan Diet and Endurance Exercise Are Associated with Low Cardiometabolic Risk. Rejuvenation Res. 2007;10:225–234. doi: 10.1089/rej.2006.0529. PubMed DOI

Mazidi M., Kengne A.P. Higher Adherence to Plant-Based Diets Are Associated with Lower Likelihood of Fatty Liver. Clin. Nutr. 2019;38:1672–1677. doi: 10.1016/j.clnu.2018.08.010. PubMed DOI

Chiarioni G., Popa S.L., Dalbeni A., Senore C., Leucuta D.C., Baroni L., Fantin A. Vegan Diet Advice Might Benefit Liver Enzymes in Nonalcoholic Fatty Liver Disease: An Open Observational Pilot Study. J. Gastrointestin. Liver Dis. 2021;30:81–87. doi: 10.15403/jgld-3064. PubMed DOI

Yokoyama Y., Barnard N.D., Levin S.M., Watanabe M. Vegetarian Diets and Glycemic Control in Diabetes: A Systematic Review and Meta-Analysis. Cardiovasc. Diagn. Ther. 2014;4:373–382. PubMed PMC

Nebl J., Drabert K., Haufe S., Wasserfurth P., Eigendorf J., Tegtbur U., Hahn A., Tsikas D. Exercise-Induced Oxidative Stress, Nitric Oxide and Plasma Amino Acid Profile in Recreational Runners with Vegetarian and Non-Vegetarian Dietary Pat-terns. Nutrients. 2019;11:1875. doi: 10.3390/nu11081875. PubMed DOI PMC

The dose-dependent effect of caffeine supplementation on performance, reaction time and postural stability in CrossFit - a randomized placebo-controlled crossover trial

The effect of caffeine dose on caffeine and paraxanthine changes in serum and saliva and CYP1A2 enzyme activity in athletes: a randomized placebo-controlled crossover trial

The effect of 12-week high-dose Colostrum Bovinum supplementation on immunological, hematological and biochemical markers in endurance athletes: a randomized crossover placebo-controlled study

Bovine colostrum supplementation as a new perspective in depression and substance use disorder treatment: a randomized placebo-controlled study

The interplay between bicarbonate kinetics and gastrointestinal upset on ergogenic potential after sodium bicarbonate intake: a randomized double-blind placebo-controlled trial