Self-pacing and cognitive performance while walking

Ten hikers completed a 4 km hike on hilly terrain three times: once self-paced without load, once self-paced with a backpack load of 10% body weight, and once externally paced with a backpack load of 10% body weight. Subjects performed mental arithmetic tasks and provided ratings of perceived exertion while walking. No differences in speed or accuracy of performance of mental arithmetic problems were observed. A battery of cognitive and physical tests was performed prior to walking and after each of the three walks. Significant differences between pre-walk baselines and post-walk tests were found only for the pattern-matching task. Subjects altered their pace in response to the addition of the backpack load, and altered their speed on downhill terrain in response to external pacing. Ratings of perceived exertion were found to correlate relatively well (r = 0.80) with heart rate, but consistently underestimated actual heart rate. Underestimation was much greater for downhill than for uphill terrain. Underestimation of heart rate by rating of perceived exertion was least when subjects carried an external load of 10% body weight.