cross sectional study about intra-individual and inter-individual variability of subjective effort in submaximal sprint running in collegiate male sprinters

Background: although subjective exercise intensity is widely used to monitor training load in athletes, the reliability of subjective effort (se) during high-intensity sprint running has not yet been established. objectives: this study aimed to examine the intra-individual and inter-individual variability in sprint running performance at different se levels. methods: eighteen male collegiate sprinters participated in the study. we measured 60 m sprint running performance at four se levels (60% se, 80% se, 90% se, and 100% se) every day for 5 days. the coefficient of variation (cv) of each participant’s 5-day performance (60 m sprint time (60t) and 40 - 50 m interval average speed (sp)) was calculated to assess the intra-individual variability of se. a repeated measures anova was used to compare 60 t, sp, and the cvs of 60 t and sp across the different se levels. results: the sp ratios of each submaximal sprint (60% se, 80% se, 90% se) to the maximal sprint (100% se) were 89.72 ± 1.62%, 95.50 ± 1.08%, and 98.11 ± 0.56%, respectively. the inter-individual variation at each se level for 60t was inversely related to the se level (60% se: 3.25%, 80% se: 2.31%, 90% se: 2.06%, and 100% se: 1.54%). significant differences were found in the intra-individual variability (cv) of 60 t between 60% se (2.22 ± 0.35%) and 90% se (1.42 ± 0.22%), 60% se and 100% se (1.40 ± 0.30%), 80% se (1.95 ± 0.32%) and 90% se, and between 80% se and 100% se (p < 0.05). conclusions: intra- and inter-individual variation at all se levels were below 5%, indicating that se is a reliable indicator of sprint running intensity. however, the lower the se, the greater the variability, suggesting se is most suitable for higher-intensity sprint running.