The influence of age on the recovery from worksite resistance exercise in career firefighters.

Abstract

To examine the changes in indirect markers of muscle damage in young and older firefighters following a feasible worksite resistance exercise routine. Nineteen young (25.5±3.4years) and 19 older male career firefighters (50.3±3.5years) completed pre-testing, an acute bout of resistance exercise, and post-testing at 24, 48, and 72h post-exercise at their fire station. Prior to all testing, firefighters completed a work-related fatigue (WRF) questionnaire to account for potential unanticipated differences in previous shift workloads. Testing included perceived muscle soreness, ultrasonography to quantify muscle size and echo intensity (EI) of the vastus lateralis (VL) and biceps brachii (BB), countermovement jump (CMJ) height and velocity, upper body (UB) peak force (PF), lower body (LB) PF and rapid force, and electromyographic (EMG) amplitude of the VL. The resistance training session included 3 sets of 8-10 repetitions of a deadlift, shoulder press, lunge, and upright row exercise at 80% 1-RM. All recovery variables were analyzed using a linear mixed model, controlling for WRF. There was no interaction (age × time) for any of the variables and a similar training volume were completed between groups (P≥0.171). Muscle soreness, CMJ height and velocity, UB PF, LB rapid force and EMG amplitude at later time intervals (100-200ms), and VL and BB muscle size were altered from baseline (P≤0.044) for 48, 24, 48, 72, and 72h post-exercise, respectively. Young firefighters exhibited greater CMJ height and velocity, LB PF, LB rapid force (200ms), and lower VL EI values than the older firefighters (P≤0.047). Age did not influence the recovery from an acute bout of worksite resistance exercise in firefighters. However, UB muscle strength, CMJ performance, and LB rapid force production were reduced 24-72h post-exercise. Appropriately scheduled and chronic on-duty resistance training may mitigate these decrements.