Annual Meeting Abstracts: C-28 - Free Communication/Poster: Exercise Evaluation
Oxygen consumption (VO2) is commonly estimated through heart rate (HR) response to a submaximal test based on several ergometers, such as treadmill, cycle and step. Step test is a method for predicting the maximal VO2 by stepping on a standardized bench.
PURPOSE: To analyze the HR response to a step test as a function of the horizontal distance between the foot to the bench (D), the bench height (H), and the lower limb segmental height (HT, tibia height; HF, femur height). METHODS: Twelve male nonathletic subjects (27 ± 4 yrs; 78.2 ± 6.2 kg; 174 ± 5 cm) accomplished 4 modified (T1, T2, T3, T4) Queens College step tests (3 min at 96 step.min−1). Different H and D were applied to each test: T1 (D = 23.5cm, H = 41cm); T2 (D = 41cm, H = 41cm); T3 (D = 41cm, H = 23.5cm); T4 (D = 23.5cm, H = 23.5cm). The HR was measured continuously (Polar S610, USA), at rest, tests and recovery phase lasting 5-min. The HR reserve (HRr) was calculated for each test. Relations between HR response with HF and HT were tested by Spearman correlation coefficient (r). Differences among tests were calculated by analysis of variance (ANOVA) one way with post hoc Tukey's test when significant differences (α = 0.05) were achieved. Additionally, HR response was modeled by linear multiple regression (forward stepwise) through least square method as a function of H, D and age. RESULTS: Highest maximal HR and HRr measured during exercise were achieved in T1 (143 ± 16bpm) and T2 (143 ± 11bpm), which were not significantly different. Comparing all tests, HR time response shown a tendency to achieve steady state during exercise (T3 and T4), such as a fast decreasing in recovery phase. This finding could be related to the highest H in T1 and T2 compared to T3 and T4. Although the lower limb height had been weakly correlated to HRr, the HF presented inversely correlated to HRr (−0.48, on average), while HT averaged r = −0.35. The HRr modeled by linear regression resulted in 87% of the explained variance (p<0.001, SE = 6.5bpm), corresponding to the following function: HRr = −14.0488 + 0.1498. age+1.18199. H+0.1881.D. CONCLUSIONS: The highest HR values were achieved in T1 and T2, according to the higher H. The HRr was adequately modeled and was more weighted by D (r = 0.93) instead H (r = 0.09).