Comparison of Prolonged Exercise Tests at the Individual Anaerobic Threshold and the Fixed Anaerobic Threshold of 4 mmol·l^-1Lactate*

Abstract

Prolonged physical exercise tests (50 min) at the threshold of 4 mmol . l-1 lactate (ATc) and at the individual anaerobic threshold (IAT) were applied in 19 rowing athletes. In each of the rowers (n = 19) work loads corresponding to the IAT did not result in a gradual lactase accumulation or exhaustion within 50 min of exercise. Means of lactate concentration and heart rate at the end of exercise were 4.0 +/- 1.6 mmol . l-1 and 182 +/- 13.0 beats . min-1, respectively. In 15 of 19 rowers, the IAT corresponded to lower work loads than the ATc. In these cases, prolonged exercise tests at the ATc showed gradual increases in lactate concentrations to a mean of 9.6 +/- 1.2 mmol . l-1, associated with exhaustion at a mean working time of 14.4 +/- 6.3 min and a mean heart rate of 192 +/- 10.4 beats . min-1. In four rowers, the IAT was found at identical (n = 3) or higher (n = 1) work loads than the ATc. In these cases, after an initial increase no further rise in lactate concentrations in blood was observed, and exhaustion did not occur during the prolonged exercise tests. These findings support the conclusion derived from the lactate kinetics model that the IAT defines the work load at the maximal lactate steady state.

Sex differences and training adaptations in relation to the lactate threshold and endurance exercise performance

“…Original research showed that the workload at IAT was lower than the workload at OBLA in the majority of their trained participants, and since exercise was maintained for 50 min at the workload corresponding to the IAT but not OBLA, it was suggested that the IAT must be reflective of MLSS [159] , although multiple constant load tests were not performed. However, subsequent research showed that power output and blood [La -] reflective of IAT were significantly higher (12% and 68%, respectively; both p < 0.01) than MLSS power output and blood [La -] in trained male rowers (n = 9), despite there being a strong relationship between IAT power output and MLSS power output (r = 0.81; p < 0.01) [7] .…”

“…Amann et al [93] investigated the IAT determined via two methods; the traditional Stegmann and Kindermann method [159] and the modified version described above by Baldari and Guidetti [165] . It was found that the Baldari and Guidetti method (r = 0.72; p < 0.01) [165] but not the traditional Stegmann and Kindermann method (r = 0.52; p > 0.05) [159] was significantly correlated with 40 km cycling time trial performance in trained male cyclists (n = 15). However, power output determined by the Baldari and Guidetti method [165] significantly underestimated 40 km time trial power output (14%; p value not stated) and therefore its capacity to establish a performance intensity cannot be confirmed.…”

“…In contrast to methods of LT2 determination that are based on a fixed [La -], or fixed inclinations of [La -], the IAT takes into account individual lactate kinetics in the blood during, and immediately after, incremental exercise to exhaustion. This is completed by examining the lactate diffusion along gradients and its simultaneous elimination [159] .…”

“…This method of threshold detection was developed with the aim of improving objective methods such as OBLA, which do not take into account individual variation in lactate levels and have been shown to be dependent on a number of external factors such as test protocol and alimentation [156,171] . As discussed, an IAT method has also been derived which takes into account individual lactate kinetics in the blood during and immediately after incremental exercise to exhaustion, based on lactate diffusion along gradients and its simultaneous elimination [159] . However, numerous flaws have also been identified with this method, with evidence suggesting it is influenced by changes in speed increments during incremental testing [162] and it may over-estimate a true threshold point [7,160,163] .…”

“…Workload at IAT lower than the workload at OBLA in 15 of the 19 participants; Since workload at OBLA ≠ workload at IAT, workload at OBLA ≠ workload at MLSS (indirect evidence); Exercise maintained for 50 min at IAT workload but not at OBLA workload (14.4 ± 6.3 min), therefore IAT must = MLSS (indirect evidence). Beneke [7] Male rowers (n = 9) [159] and; (2) those of Baldari & Guidetti [165] The Baldari method correlated with 40 [165] [163] Male rowers (n = 10) …”