The Use of Subjective Ratings of Perceived Exertion (RPE) to Estimate Fixed Blood Lactate Concentrations During Incremental Cycle Ergometer Exercise

Prescription of exercise intensity based on blood lactate concentration has become widely accepted in recent years. The methods used to directly measure blood lactate concentration however, can be costly, time consuming and potentially hazardous to both subject and tester. Recent studies indicate that a strong relationship exists between subjective feelings of strain experienced during exercise and changes in the appearance of blood lactate. This raises the possibility that subjective ratings of perceived exertion (RPE) can be used to simply and effectively estimate and monitor appropriate exercise intensity based on blood lactate concentration. In order to test this theory two groups of subjects, high active (HA) and low active (LA) were asked to complete a continuous incremental cycle ergometer protocol. Heart rate, blood lactate, differentiated (overall) and undifferentiated (central and local) RPE values were measured at the completion of each workload. At exercise intensities corresponding to 2.0, 2.5 and 4.0 mmol blood lactate, no statistically significant differences were found between the groups for undifferentiated RPE values, however low active individuals consistently rated exercise intensity corresponding to each of the blood lactate conditions as being easier than the high active group (mean overall RPE at exercise intensity corresponding to 4.0 mmol blood lactate was 15.7±0.4 for HA compared to 14.0±0.5 for LA). Higher RPE responses from the high active group occurred due to the fact that increases in the appearance of blood lactate were observed closer to maximal relative exercise intensity for individuals in this group (4.0 mmol blood lactate occurred at 80.3% maximum heart rate for HA and 73.4% maximum heart rate for LA). Results indicate that RPE values of between 9 and 15 will result in reliable estimation of training intensities required for improvements in cardiorespiratory fitness and endurance performance based on the blood lactate response to exercise but that consideration should be given to potential modification of effort sense which may only be experienced under extreme physiological conditions.