Trekking poles are used by hikers for improved stability and lowered leg fatigue due to increased upper body muscle involvement. However, the weight of the poles and exaggerated upper body movement when using poles may increase total energy expenditure at a given walking speed. Few studies have investigated the physiological responses of hiking with trekking poles outside the laboratory setting. The purposes of this study were to determine if trekking poles altered physiological responses to hiking on varied terrain, and whether responses between trials were dependent on the grade of the terrain. Fourteen recreational hikers completed four hiking trials over a course that included sustained sections of flat (0 +/- 1% grade), steep uphill (>10% grade), gradual uphill (5% grade), gradual downhill (-5% grade) and steep downhill (<-10% grade) terrain. Subjects walked at a self-selected speed that was matched across trials using time-splits and a metronome. Two trials were conducted with hiking poles and two without poles. [latin capital V with dot above]O2 was significantly elevated (p <0.05) during the pole trials (1502.9 +/- 510.7 ml/min) compared to the no-pole trials (1362.4 +/- 473.2 ml/min). Similarly, ventilatory efficiency ([latin capital V with dot above]E) (43.1 +/- 9.6; 38.3 +/- 10.1 L/min) and heart rate (HR) (112.1 +/- 9.7; 105.7 +/- 10.4 bt/min) were significantly higher during the pole trials than the no-pole trials. However, ratings of perceived exertion (RPE) was not altered by pole condition (8.5 +/- 0.7; 8.4 +/- 0.8). Comparisons within each grade revealed significantly higher physiological responses for [latin capital V with dot above]O2, [latin capital V with dot above]E and HR in the pole-condition at all grades, with no significant variable*grade interactions. RPE measures were not significantly different between pole trials at any grade. These data suggest that trekking poles may be a beneficial tool for increasing caloric expenditure, as energy production increased during exercise without increased perceptions of effort.