Author(s): SON, S., CHO, H., YUN, S., LEE, Y., JUNG, D.G., SHIM, E., LEE, D.T., Institution: UNIVERSITY OF KOOKMIN, Country: KOREA, SOUTH, Abstract-ID: 1587

INTRODUCTION:
The purpose of this study was to evaluate the metabolic responses during walking at a constant speed on uphill and downhill slopes while maintaining a preferred step rate (PSR, in steps per minute) or modified step rates.
METHODS:
Participants were 10 healthy men in their 20s (26.8±1.6 yrs, 172.4±3.9 cm, 73.7±6.2 kg). They participated in 30 testing conditions; 3 slopes (Flat, 10% downhill (D10 %), and 10% uphill (U10 %)) ˟ 2 walking speed (3.5 and 5 kph) ˟ 5 step rates (80, 90, 100, 110, and 120 % of PSR). In each condition, they walked on a treadmill for 5 minutes, and their step frequency, heart rate (HR), and oxygen uptake (VO2) were measured. First, they were asked to perform in 6 conditions (3 slopes ˟ 2 speed) at their self-selected step rates, and these were considered as PSR corresponding to 100 % of PSR. Based on their PSR, individual 80, 90, 110, and 120 % of PSR were calculated, and these step rates were utilized at the remaining conditions. The order of testing was randomly assigned. One-way ANOVA with repeated-measures was used for analysis of the effects of slopes and step rates, and Scheffe post hoc test was performed. The significance level was set at α=.05.
RESULTS:
PSR was highest at both 3.5 and 5 kph in D10 % (102.9±6.2 and 113.9±4.9) than Flat (96.4±5.4 and 111.3±4.6) and U10 % (92.1±6.1 and 107.5±6.7 spm, respectively, p<0.001). HR at PSR was highest at both 3.5 and 5 kph in U10 % (110.6±8.1 and 126.8±11.4) than Flat (88.3±6.0 and 94.5±7.4) and D10 % (85.4±6.8 and 88.8±8.1 bpm, respectively, p<0.001). VO2 at PSR was highest at both 3.5 and 5 kph in U10 % (24.7±3.2 and 30.6±3.5) than Flat (14.1±2.2 and 17.8±1.8) and D10 % (10.9±2.0 and 11.4±1.7 ml/kg/min, respectively, p<0.001). During 3.5 kph walking on flat, HR was higher in 120%-PSR (97.1±9.8 bpm, p<0.001) than 100%-PSR and VO2 was higher in 80%-PSR and 120%-PSR (15.5±2.2 and 15.5±1.8 ml/kg/min, respectively p<0.05) than 100%-PSR. HR during walking at 5.0 kph in all varied step rates (i.e., 80, 90, 110, and 120%-PSR) was higher in D10 % (ranged 93.2±9.7 ~ 98.3±10.5), Flat (101.9±10.4 ~ 109.2±10.9), and U10 % (133.4±10.6 ~ 145.5±13.7 bpm) than 100%-PSR (p<0.001). VO2 during walking at 5.0 kph in all varied step rates was also higher in D10 % (ranged 12.2±2.0 ~ 15.6±2.6), Flat (17.7±2.2 ~ 20.8±2.4), and U10 % (31.3±3.2 ~ 34.3±4.3 ml/kg/min) than 100%-PSR (p<0.001).
CONCLUSION:
The preferred step rates were higher during downhill walking than the leveled and uphill walking, while HR and VO2 were higher during uphill than the leveled and downhill walking. As walking speed increased from 3.5 to 5 kph, HR and VO2 also increased as the step rates both increased or decreased from the preferred step rates.