External loading during daily living improves high intensity tasks under load

Tactical athletes (TA) perform high intensity tasks while carrying considerable external loads. This study examined the effects of wearing an external load during daily living (ELDL) on high intensity TA tasks. Nine trained men (21 ± 2 years; 180 ± 1 cm; 91.1 ± 4.4 kg) completed 3 weeks of ELDL which consisted of wearing a weighted vest equal to ∼11%, 13%, and 16% body mass 4 days/week; 8 h/day during weeks 1, 2, and 3 of ELDL phase. Weight vests were not worn during training. A 3 week control phase (CON) commenced after ELDL. Four TA performance tasks were practiced during two familiarization sessions before experimental trials. The tasks included a 5 flight, 53 step stair climb, 44 m zig-zag sprint with 2 points of change in direction and kneeling on one knee, 2 × 25 m casualty drag (84 kg), and 8 × 25 yard shuttle run. All tasks were completed while wearing a 12 kg vest. Percentage change in performance from pre-to post-intervention were compared between ELDL and CON using dependent t-tests, and Cohen's D effect size was calculated for absolute change in performance for each task. All tasks displayed trends of robust improvement from baseline to post ELDL, followed by modest drops in performance during CON (p-value range = 0.03 to < 0.001; ES range 1.1-2.6). The addition of ELDL provides a transient enhancement of occupational anaerobic task performances for TA that exceeds resistance and conditioning training alone.