Percentual responses proximal to the onset of blood lactate accumulation.

AIM: Running at incremental velocities proximal to the onset of blood lactate accumulation (OBLA) elicits linear increases in VO(2), and HR, while the increases in V(E) and blood lactic acid concentrations (BLa) are curvilinear. In addition, effort sense is often measured in the field with the traditional 15-point scale Ratings of Perceived Exertion scale, increases linearly whereas the perceptual response of affect seem to decrease in a nonlinear manner. This study examined the changes in effort sense (RPE) and affect, utilizing the Feeling Scale (FS), at 3 running intensities proximal to the onset of blood lactate accumulation. In addition, the relationship between these perceptual responses and V(E), VO(2), HR, RER, and BLa were examined.

METHODS: Eleven highly-trained distance runners (VO(2max) = 67.65+/-1.24) participated in 2 sessions of data collection. During Session 1 subjects performed a discontinuous progressive treadmill protocol to determine peak aerobic power. After each stage a finger tip blood sample was taken to determine BLa. A regression line between the 2 successive workloads that produced BLa above and below 4 mM was calculated to predict the VO(2) that would generate 4mM BLa (VO(2) @ 4 mM). Within 1 week each subject returned for Session 2, which included a 10-min warm-up run followed by 3 submaximal runs lasting 5 min each: the VO(2) at 10% below OBLA (VO(2) 10% ), the VO(2) at OBLA (VO(2) @ 4 mM), and the VO(2) at 10% above OBLA (VO(2) 10%). During the last minute of each run VO(2), V(E), HR, RER, RPE, and FS were assessed. In addition, Bla was assessed immediately following each run.

RESULTS: Results demonstrated that VO(2) 10%, VO(2) @ 4 mM, and VO(2) 10% - elicited BLa of 2.66+/-0.33, 3.75+/-0.40, and 6.10+/-0.68 mM, respectively. In addition, RPE increased significantly from VO(2) 10% to VO(2) @ 4 mM and from VO(2) @ 4 mM to VO(2) 10% -; whereas FS demonstrated a slight decrease from VO(2) 10% to VO(2) @ 4 mM, and a more substantial and significant decrease from VO(2) @ 4 mM to VO(2) 10% -. Correlational analyses revealed significant relationships at VO(2) 10% -. Specifically, RPE and FS were negatively related (r=0.62), while RPE and VO(2) were positively related (r=0.53). Correlations across all workloads revealed a tendency for more powerful relationships to exist among RPE and physiological cues than FS and physiological cues.

CONCLUSION: This is the first study to directly examine changes in RPE and FS in relation to the physiological threshold for anaerobic metabolism, Bla, which responds to linear increases in exercise intensity in a curvilinear manner. Results support previous investigations suggesting a that the drop in FS has some distinction from the increase in RPE and that FS may be more sensitive to the onset of anaerobic metabolism. Moreover, the relationship of RPE to FS at VO(2) 10% -, but not VO(2) 10% and VO(2) @ 4 mM, supports the hypothesis that the unique variability of FS is diminished at higher intensities of exercise when physiological cues are unambiguous.