The Effect of CrossFit vs. Resistance Training on Aerobic, Anaerobic, and Musculoskeletal Fitness

Abstract

Background: Although a number of studies to date have investigated the acute physiological outcomes of single CrossFit Workout Of the Days (WODs) and/or fitness attributes of well-trained CrossFit athletes, the variable populations, training histories, and short duration analysis of participants in these studies makes it difficult to evaluate the effectiveness of long term (multi-week) CrossFit training to improving fitness attributes (especially when compared to more traditional resistance training modalities). Thus, the primary purpose of the current study was to investigate the effects of multi-week CrossFit training on specific fitness attributes compared to a traditional resistance training intervention (of equivalent duration). Participants, Measures, and Training: 30 recreationally active male and female adults (BM: 70.0 ± 9.9kg, age: 23.2 ± 3.23 years) were randomly assigned to one of 3 groups (FE, CF, TRAD; n=10). All participants performed the same battery designed to assess musculoskeletal strength, endurance, and power, as well as aerobic and anaerobic power, and anaerobic metabolism outcomes. Following pre-testing, the intervention groups performed 6 weeks of resistance training; participants in the CrossFit (CF) group performed up to 4 days/week of researcher supervised CrossFit modality training, while those in the traditional resistance training group (TRAD) performed a more conventional form of resistance training (at the same frequency, while also supervised by a member of the research team). The free exercise group (FE) was asked to maintain their pre-study exercise regimens for the entire study duration, and was not supervised by a member of the research team during any training session. Following 6 weeks of training, the same test battery (completed prior to training) was performed; detailed records of all additional physical activity (including exercise performed external to study sanctioned workouts) were also analyzed to determine training time and subjective intensity. Results: The major findings from the primary analyses were: 1. post-training mean lower body power output (measured via 30 second Wingate cycle ergometer test) of CF was significantly lower than both FE (p = .004, CF < FE by 96.36 ± 30.98 watts) and TRAD (p = .025, CF < TRAD by 66.71 ± 28.09 watts); 2. post-training mean upper body endurance (measured via bent-arm hang time to failure) of CF was significantly greater than TRAD (p = .026, CF > TRAD by 4.63 ± 1.95 seconds). Secondary analyses revealed that CF incurred positive changes in all measures of strength (p < .05), as well as significant improvements in shuttle run test performance (0.85 ± 0.22 stages, p = .004), estimated VO2max (2.10 ± 0.78 ml/kg/min, p = .025), and general lower body endurance (measured via maximum bodyweight squats in 1 minute) (4.20 ± 1.42 repetitions, p = .026). There were, however, no differences in total time spent exercising (p = .440), as well as time spent performing moderate (p = .489) and vigorous (p = .478) intensity physical activity between groups (based on participant training log data recorded throughout the study duration). Conclusion: While CF elicited significant improvements in aerobic power, whole body muscular strength, upper body pull endurance, and lower body general endurance over time, this group also experienced a significant decrement in lower body anaerobic power from pre to post training. Compared to TRAD, CF only elicited greater improvements in upper body muscular endurance, and greater decrements in lower body anaerobic power. Thus, relative to traditional resistance training, CrossFit may be superior at improving upper body endurance, inferior at improving lower body anaerobic power, and similar at improving whole body strength, aerobic power, and lower body general endurance in recreationally active adults (after 6 weeks of training). Future research should examine if these adaptations can be extended to other populations (such as elite endurance athletes) who may benefit from concurrent improvements in both strength and aerobic fitness, or athletes involved in sports requiring substantial amounts of upper body muscle endurance (such as rock climbing). Future studies should also examine the molecular and genetic factors underpinning changes in fitness during concurrent training (which is used during CrossFit workouts).