Physiological responses and perceptions of exertion in a step aerobics session

The aims of this study were to establish the cardiovascular and metabolic demands of a university step aerobics session entitled 'Uni-Step' performed at three step heights, and to evaluate the use of heart rate and ratings of perceived exertion for the estimation of exercise intensity during this mode. Ten female participants in step aerobics (mean VO2max = 47.7, s = 6.8 ml.kg-1.min-1) performed a 40-min Uni-Step routine on steps of height 6, 8 and 10 inches (15.2, 20.3 and 25.4 cm). Oxygen uptake, heart rate and ratings of perceived exertion were recorded throughout each test. Maximum oxygen uptake (VO2max) and maximum heart rate were measured using a continuous treadmill protocol. The mean intensities were 45.6%, 51.6% and 56.2% VO2max for the 6-, 8- and 10-inch steps respectively. The mean percent heart rate reserves were 57.2%, 63.6% and 70.1% at these three heights respectively. Correlations indicated a weak relationship between %VO2max and ratings of perceived exertion for the 6- and 8-inch steps (r = 0.61 and 0.66 respectively) but a stronger one for the 10-inch step (r = 0.79). Uni-Step performed on the two highest steps was of a sufficient relative intensity to improve or maintain the cardiovascular fitness of participants in this study. The lowest step may be useful for participants of lower fitness. Heart rate overestimated the metabolic cost of Uni-Step at all three step heights and therefore caution is advised if used to predict intensity. Low correlations between %VO2max and ratings of perceived exertion at the two lower step heights indicate that ratings of perceived exertion may have limited utility in prescribing training intensity.