The validity of regulating blood lactate concentration during running by ratings of perceived exertion

We examined whether ratings of perceived exertion (RPE) observed during an incremental (response) protocol could be used to produce target blood [HLa] of 2.5 mM and 4.0 mM during a 30-min treadmill run at a constant RPE, RPE (15.3, 17.6 19.1), oxygen uptake (V̇O₂) (3.31, 3.96, 4.00 l · min^-1), velocity (V) (198, 218, 223 m · min^-1), and heart rate (HR) (179, 185, 190 bpm) at blood [HLa] of 2.5 mM and 4.0 mM, and peak were determined for nine subjects (5 males, 4 females) during incremental exercise. Subjects then completed two 30-min runs at the RPE corresponding to blood [HLa] of 2.5 mM (RPE 2.5 mM) and 4.0 mM (RPE 4.0 mM) measured during the incremental protocol. For both 30-min runs, V̇O₂ was not different from V̇O₂ corresponding to either 2.5 or 4.0 mM blood [HLa] during the incremental test. During the 30-min run at RPE 2.5 mM: (a) only during minutes 25-30 was the blood [HLa] significantly different than 2.5 mM (3.2 ± 0.6 mM, P < 0.05) for the first 20 min HR was significantly lower than the HR at 2.5 mM during the incremental protocol, and (c) V did not differ from V at 2.5 mM during the incremental protocol. During the 30-min run at RPE 4.0 mM; (a) blood [HLa] was not significantly different from 4.0 mM, (b) HR at every time point was significantly lower than HR 40 mM during the incremental protocol, and (c) V was decreased over time by an average of 24.6 m · min^-1 (P < 0.05). Because RPE from the response protocol was able to produce a blood [HLa] close to the criterion value during each 30-min run, we conclude that RPE is a valid tool for prescribing exercise intensities corresponding to blood [HLa] of 2.5 mM and 4.0 mM.