The Effects of Load Carriage and Physical Fatigue on Cognitive Performance

Abstract

In the current study, ten participants walked for two hours while carrying no load or a 40 kg load. During the second hour, treadmill grade was manipulated between a constant downhill or changing between flat, uphill, and downhill grades. Throughout the prolonged walk, participants performed two cognitive tasks, an auditory go no/go task and a visual target detection task. The main findings were that the number of false alarms increased over time in the loaded condition relative to the unloaded condition on the go no/go auditory task. There were also shifts in response criterion towards responding yes and decreased sensitivity in responding in the loaded condition compared to the unloaded condition. In the visual target detection there were no reliable effects of load carriage in the overall analysis however, there were slower reaction times in the loaded compared to unloaded condition during the second hour.

Effect of locomotor demands on cognitive processing

“…muscle activity, motion artifact) 5,24,50 . Behavioral studies of walking with a heavily loaded rucksack have demonstrated changes in biomechanics of gait including ground reaction force, step length, body segment acceleration, and muscle activation 12,28,51,52 , all of which have been identified as sources of noise in EEG. Our results show that we were able to measure the expected waveforms and topography related to a visual discrimination task during walking with a heavily loaded rucksack.…”

“…The rating of perceived exertion was significantly different across the three conditions: seated, unloaded walking, and loaded walking. We did not include measures of biomechanics or energetics in our study, but there is ample evidence from past studies that the addition of 40% body weight load during walking substantially affects gait biomechanics and metabolic measures 12,28,51,52 . Although we did not measure it, we also observed increased amounts of sweating with the greater rucksack load.…”

“…Previous loaded walking studies that have found reduced cognitive performance under certain circumstances. Eddy and colleagues 12 studied subjects performing auditory and visual detection tasks while walking for two hours both unloaded and with a 40 kg rucksack load. They found greater errors and longer reaction times during loaded vs unloaded marching, but only after the first hour and with the inclusion of surface grades other than level.…”

“…In the high physical demand condition, we added lead pellets to the rucksack to bring the total load up to ~40% body weight. The 40% body weight load was chosen to be within the range of real world loads that Soldiers are trained to carry and often may carry in real operations 12 (U.S. Army Field Manual 21–18).…”

The Physical Fitness Effects of a Week-Long Specialist Tactical Police Selection Course

“…The large decrease in vertical jump measures in the second day of this study are thought to be due to the timetabling of the selection course. Candidates were tasked with both a load carriage event and another task with a high number of stairs on the first night, which would have elicited high levels of neuromuscular fatigue [ 28 ] leading to decreases in both physical and cognitive performance [ 29 , 30 ]. Additionally, a greater amount of rest was given after the first night, which may also have had some contribution to the relative improvements in performance in the latter stages of the week.…”