Author(s): TAKANO, D., HIRASAWA, A., SAKURAI, A., YAMADA, Y., HORINO, M., MURATA, H., FUKUIE, M., SUZUKI, R., MATSUSHIMA, S., MATSUDA, T., SHIBATA, S., Institution: KYORIN UNIVERSITY, Country: JAPAN, Abstract-ID: 643

INTRODUCTION:
Anaerobic threshold (AT)-based exercise prescription is commonly performed as cycle ergometer exercise at a pedaling rate of 60 rpm. However, patients often request changes in pedaling rate. The effects of different pedaling rates on hemodynamic and metabolic responses remain unclear. Furthermore, to our knowledge, no previous studies have examined the effects of varying pedaling rate while keeping the workload constant at the AT workload determined at 60 rpm, which is commonly used in AT-based exercise prescription. Therefore, this study aimed to clarify the effects of different pedaling rates on hemodynamic and metabolic responses at the AT workload determined at 60 rpm.
METHODS:
Twelve healthy adults (9 men and 3 women; age 27+/- 3 years) participated. On day 1, the AT workload was determined during cardiopulmonary exercise testing at 60 rpm. On day 2, participants performed constant-load cycle ergometer exercise at the AT workload under three pedaling rate conditions of 40, 60, and 80 rpm in a randomized crossover design. Measurements were obtained at steady state, 3 min after the onset of exercise. Outcomes included respiratory gas analysis, echocardiography, and blood lactate concentration. Repeated-measures analysis of variance (ANOVA) was performed, followed by Holm-corrected multiple comparisons when a significant main effect was detected.
RESULTS:
Respiratory exchange ratio increased with increasing pedaling rate (40 rpm: 0.93+/-0.04, 60 rpm: 0.99+/-0.04, 80 rpm: 1.03+/-0.05; P<0.001). Cardiac output increased with pedaling rate (40 rpm: 8.7+/-1.3 L/min; 60 rpm: 10.0+/-1.6 L/min; 80 rpm: 12.3+/-2.0 L/min; P<0.001). Oxygen uptake also increased with pedaling rate (40 rpm: 1.17+/-0.26 L/min; 60 rpm: 1.23+/-0.26 L/min; 80 rpm: 1.36+/-0.26 L/min; P<0.001). In contrast, arteriovenous oxygen difference decreased with increasing pedaling rate (40 rpm: 13.8+/-1.7 mL O2/100 mL; 60 rpm: 12.6+/-1.6 mL O2/100 mL; 80 rpm: 11.4+/-2.2 mL O2/100 mL; P<0.001). Holm-corrected multiple comparisons showed significant differences for all pairwise comparisons among the three pedaling rate conditions of 40, 60, and 80 rpm for the respiratory exchange ratio, cardiac output, oxygen uptake, and arteriovenous oxygen difference.
CONCLUSION:
Increasing pedaling rate was associated with increased cardiac output and decreased arteriovenous oxygen difference, suggesting that oxygen delivery may increase relative to oxygen demand. In contrast, the increase in respiratory exchange ratio suggested that anaerobic metabolism may be recruited even under relatively sufficient oxygen delivery. Therefore, careful consideration may be required when changing pedaling rate during AT-based exercise prescription.