Body armour: the effect of load, exercise and distraction on landing forces

We investigated the effect of added load and intense exercise on jump and landing performance and ground reaction force (GRF) during landings where attentional demand was varied. Fifty-two males (37 +/- 9.2 years, 180.7 +/- 6.1cm, 90.2 +/- 11.6kg, maximal aerobic fitness (VO2max) 50 +/- 8.5ml (.) kg(-1 .) min(-1), BMI 27.6 +/- 3.1, mean +/- s) completed a VO2max test. Experimental sessions were completed (4 days in between) in a randomised counterbalanced order, one while wearing body armour and appointments (loaded) and one without load (unloaded). A vertical jump, a drop landing concentrating on safe touchdown, a drop jump and a drop landing with an attentional distraction were performed. These were repeated 1 min after a 5-min treadmill run. Mean jump height decreased by 12% (P<0.001) with loading and a further by 6% following the running task. Peak GRFs were increased by 13-19% with loading (P<0.001) depending on the landing task demands and a further by 4-9% following intense exercise. The distracted drop landing had significantly higher GRFs compared to all other landings. Results demonstrate that added load impacts on jumping and landing performance, an effect that is amplified by prior intense exercise, and distraction during landing. Such increases in GRF apply to police officer performance in their duties and may increase the risk of injury.