Effects of load carrying methods and stair slopes on physiological response and postures during stairs ascending and descending.

The purpose of this study was to examine the effects of load carrying methods, stair slopes and walking speeds on heart rate and walking postures. Nine participants climbed up and down stairs with various stair slopes (24°, 30° and 36°), walking speeds (72, 96, and 132 steps per minute), and using different load carrying methods (empty loads, backpack, and hand-held). The effects of these factors on heart rate, Borg-RPE and flexion angles of knee joints, hip joints and trunk angles were investigated. This study demonstrated that increased stair slopes and walking speed were associated with increased heart rate and RPE. The heart rate for empty loads subjects was lowest, followed by backpack load and hand-held load. Climbing stairs with larger inclination was associated with smaller knee joint flexion angle and larger trunk and hip joint flexion angle. In conclusion, it is easier for subjects to carry a load of the same weight up stairs by backpack than by hand. However, the stair slope should be less than 30°. Thus, the standard fixed stair slope (30° of stair slope) on recommended for riser height and tread depth are 160 mm (6.5 inches) and tread depth 280 mm (11 inches).