MedXFit-Effects of 6 months CrossFit® in sedentary and inactive employees: A prospective, controlled, longitudinal, intervention study

Abstract

Background and aims: Sedentary behavior and physical inactivity are associated with musculoskeletal disorders (MSD). Muscle and mobility enhancing training is recommended to promote musculoskeletal fitness and prevent MSD. A functional fitness program emphasizing the importance of musculoskeletal fitness is provided by CrossFit®. However, data from long-term CrossFit® interventions assessing measures of musculoskeletal fitness in sedentary and inactive individuals does not exist.

Methods: This prospective, controlled study investigates the effects of 6 months CrossFit® training (2×60 min/week) in inactive adults (in terms of <2 muscle or mobility enhancing training sessions per week) with predominantly sitting or standing occupations. 91 participants were initially assessed, 2 were excluded, 55 self-selected for intervention (IG), and 34 for the control group (CG). Primary endpoint was a change in mobility (Functional Movement Screen score). Secondary endpoints were changed in strength (maximum isometric strength in kg; Dr. Wolff BackCheck®), and well-being (WHO-5 score). Key exploratory endpoints were changes in back-issue measures (pain intensity, limitation, and frequency).

Results: 39 participants of IG and 31 of CG completed the evaluation after 6 months. The IG improved significantly more (p < 0.001) compared with the CG in the FMS (η² = 0.58), trunk extension (η² = 0.46), trunk flexion (η² = 0.47), trunk lateral flexion left (η² = 0.41), trunk lateral flexion right (η² = 0.42), upper body push (η² = 0.4), upper body pull (η² = 0.25), hip extension left (η² = 0.18), and hip extension right (η² = 0.4). Change of WHO-5 scores did not significantly differ between groups (p = 0.55; η² = 0.01). Exploratory analysis of back-issue data showed a higher decrease for pain intensity, limitation, and frequency in the IG compared with the CG.

Conclusion: This study proves for the first time within the scope of a prospective, controlled study the broad benefits of CrossFit® in inactive adults doing predominantly sedentary work.

Keywords: exercise; fitness; functional movement; health; high‐intensity interval training; military.

Figure 1

Schematic overview of the MedXFit study.

Figure 2

Participant flow over the course of the study.¹ Due to minor shoulder injuries, two participants of the intervention and one of the control group had to leave out particular movements of the BackCheck®. Additionally, one participant was incapable of completing the BackCheck® as prescribed.² Due to a minor shoulder injury one participant did not complete the full Functional Movement Screen.

Figure 3

Strength: difference in change between groups from baseline (t0) to 6 months (t1). HEl, hip extension left; HEr, hip extension right; TE, trunk extension; TF, trunk flexion; TLFl, trunk lateral flexion left; TLFr, trunk lateral flexion right; UPush, upper body push; UPull, upper body pull

Figure 4

Distribution of pain intensity, limitation, and frequency for IG and CG at baseline (t0) and 6‐months follow‐up (t1). CG, control group; IG, intervention group