Effect of a novel low volume, high intensity concurrent training regimen on recruit fitness and resilience

Abstract

Objectives: To determine the effect of a novel low volume high intensity concurrent training regimen and warm-up on physiological performance and musculoskeletal injury in Australian recruits.

Design: Controlled longitudinal intervention.

Methods: Military recruits completed 12 weeks of either experimental (EXP: n=78, 6-8RM resistance loads, and high intensity intervals) or basic military (CON: n=69, usual practice) matched for total sessions and time. Endurance (3.2km 22kg-load carriage, V˙O_{2 peak}, multi-stage fitness test (MSFT)), 1RM strength and local muscle endurance (bench, squat, box-lift and push-ups) and power (squat jump) were assessed at Weeks 1,6,12. Body composition, physical activity (PAC·min^-1) and heart rate reserve (HRR%), were assessed at Weeks 2,7,9. Musculoskeletal injury and mechanism were recorded. Two-way repeated measures ANOVA interaction (group×time), mean difference and effect size (ES) are reported p≤0.05.

Results: A significant interaction over 12 weeks was observed for load carriage (ES -0.30), squat jump (ES 0.65), V˙O_{2 peak} (ES 0.58), MSFT (ES 0.41), push-ups (ES 0.26), 1RM bench (ES 0.26), squat (ES 1.05) and box lift (ES 0.27) in EXP compared to CON. At Week 12 significantly greater squat (38.9kg), MSFT (2.1mL·kg^-1·min^-1), and faster load carriage (49.9s) was observed in EXP than CON, but no difference in body composition. EXP had a lower PAC·min^-1 (641.1±63.1) but higher HRR% (21.8±4.0) compared to CON. EXP had a lower number of injuries (6) compared to CON (17).

Conclusions: The inclusion of compound-specific resistance exercise and high intensity intervals improved physical function and was associated with reduced musculoskeletal injury.

Keywords: Endurance; Injury prevention; Occupational; Overtraining; Strength.